query: the process by which the acrosome membranes of sperm break down is known as

pos: Acrosome vitro" by substances a sperm cell may encounter naturally such as progesterone or follicular fluid, as well as the more commonly used calcium ionophore A23187. This can be done to serve as a positive control when assessing the acrosome reaction of a sperm sample by flow cytometry or fluorescence microscopy. This is usually done after staining with a fluoresceinated lectin such as FITC-PNA, FITC-PSA, FITC-ConA, or fluoresceinated antibody such as FITC-CD46. In the case of globozoospermia (sperm with round heads), the Golgi apparatus is not transformed into the "acrosome", causing male infertility. Acrosome The acrosome is an organelle that develops

pos: Acrosome reaction Acrosome reaction During fertilization, a sperm must first fuse with the plasma membrane and then penetrate the female egg in order to fertilize it. Fusing to the egg usually causes little problem, whereas penetrating through the egg's hard shell or extracellular matrix can present more of a problem to the sperm. Therefore, sperm cells go through a process known as the acrosome reaction which is the reaction that occurs in the acrosome of the sperm as it approaches the egg. The "acrosome" is a cap-like structure over the anterior half of the sperm's head. As the sperm approaches the zona

pos: Acrosome reaction Acrosome reaction During fertilization, a sperm must first fuse with the plasma membrane and then penetrate the female egg in order to fertilize it. Fusing to the egg usually causes little problem, whereas penetrating through the egg's hard shell or extracellular matrix can present more of a problem to the sperm. Therefore, sperm cells go through a process known as the acrosome reaction which is the reaction that occurs in the acrosome of the sperm as it approaches the egg. The "acrosome" is a cap-like structure over the anterior half of the sperm's head. As the sperm approaches the zona

pos: Acrosome Acrosome The acrosome is an organelle that develops over the anterior half of the head in the spermatozoa (sperm cells) of many animals including humans. It is a cap-like structure derived from the Golgi apparatus. Acrosome formation is fully completed 5–10 years after testicular maturation. In Eutherian mammals the acrosome contains digestive enzymes (including hyaluronidase and acrosin). These enzymes break down the outer membrane of the ovum, called the zona pellucida, allowing the haploid nucleus in the sperm cell to join with the haploid nucleus in the ovum. This shedding of the acrosome, or acrosome reaction, can be stimulated "in

pos: Fertilisation the sperm and activating the acrosome reaction. ZP3 is sufficient though unnecessary for sperm/egg binding. Two additional sperm receptors exist: a 250kD protein that binds to an oviduct secreted protein, and SED1, which independently binds to the zona. After the acrosome reaction, the sperm is believed to remain bound to the zona pellucida through exposed ZP2 receptors. These receptors are unknown in mice but have been identified in guinea pigs. In mammals, the binding of the spermatozoon to the GalT initiates the acrosome reaction. This process releases the hyaluronidase that digests the matrix of hyaluronic acid in the vestments around

pos: Spermatozoon into the tails. The whip-like tail (flagellum) of the sperm is studded with ion channels formed by proteins called CatSper. These channels are selective, allowing only calcium ions to pass. The opening of CatSper channels is responsible for the influx of calcium. The sudden rise in calcium levels causes the flagellum to form deeper bends, propelling the sperm more forcefully through the viscous environment. Sperm hyperactivity is necessary for breaking through two physical barriers that protect the egg from fertilization. The second process in sperm activation is the acrosome reaction. This involves releasing the contents of the acrosome, which disperse,

pos: Acrosome reaction species a protuberance (the acrosomal process) forms at the apex of the sperm head, supported by a core of actin microfilaments. The membrane at the tip of the acrosomal process fuses with the egg's plasma membrane. In some echinoderms, including starfish and sea urchins, a major portion of the exposed acrosomal content contains a protein that temporarily holds the sperm on the egg's surface. In mammals the acrosome reaction releases hyaluronidase and acrosin; their role in fertilization is not yet clear. The acrosomal reaction does not begin until the sperm comes into contact with the oocyte's zona pellucida. Upon coming

pos: Acrosome reaction mind that a certain percentage of sperm cells will undergo a spontaneous acrosome reaction without the presence of the ovum. Those cells are not able to fertilise the egg, even if they do reach it later. Other cells will spontaneously shed their acrosome during the process of apoptosis/necrosis. When using intracytoplasmic sperm injection (ICSI) for IVF, the implantation rate is higher in oocytes injected with spermatozoa that have undergone acrosome reaction (~40%) vs. those injected with nonreacted spermatozoa (~10%). The implantation rate is ~25% in when injected with both reacted and nonreacted spermatozoa. The delivery rate per cycle follows the

pos: Acrosome reaction into contact with the zona pellucida, the acrosomal enzymes begin to dissolve and the actin filament comes into contact with the zona pellucida. Once the two meet, a calcium influx occurs, causing a signaling cascade. The cortical granules inside the oocyte then fuse to the outer membrane and a transient fast block reaction occurs. It also alters a patch of pre-existing sperm plasma membrane so that it can fuse with the egg plasma membrane. A sperm penetration assay includes an acrosome reaction test that assesses how well a sperm is able to perform during the fertilization process. Sperm that are

pos: Acrosome reaction "acrosome reaction". The sperm cell acquires a "hyperactive motility pattern" by which its flagellum produces vigorous whip-like movements that propel the sperm through the cervical canal and uterine cavity, until it reaches the isthmus of the fallopian tube. The sperm approaches the ovum in the ampulla of the fallopian tube with the help of various mechanisms, including chemotaxis. Glycoproteins on the outer surface of the sperm then bind with glycoproteins on the zona pellucida of the ovum. Sperm that did not initiate the acrosome reaction prior to reaching to the zona pellucida are unable to penetrate the zona pellucida. Since

pos: Acrosome reaction the acrosome reaction has already occurred, sperm are then able to penetrate the zona pellucida due to mechanical action of the tail, not because of the acrosome reaction itself. The first stage is the penetration of corona radiata, by releasing hyaluronidase from the acrosome to digest cumulus cells surrounding the oocyte and exposing acrosin attached to the inner membrane of the sperm. The cumulus cells are embedded in a gel-like substance made primarily of hyaluronic acid, and developed in the ovary with the egg and support it as it grows. It is necessary for the acrosome reaction to occur before

pos: Hyperactivation Hyperactivation Hyperactivation is a type of sperm motility. Hyperactivated sperm motility is characterised by a high amplitude, asymmetrical beating pattern of the sperm tail (flagellum). This type of motility may aid in sperm penetration of the zona pellucida, which encloses the ovum. Hyperactivation could then be followed by the acrosome reaction where the cap-like structure on the head of the cell releases the enzymes it contains. This facilitates the penetration of the ovum and fertilisation. Some definitions consider sperm activation to consist of these two processes of hyperactivation and the acrosome reaction Hyperactivation is a term also used to express

pos: Antisperm antibodies or anal intercourse. In both men and women, ASA production are directed against surface antigens on sperm, which can interfere with sperm motility and transport through the female reproductive tract, inhibiting capacitation and acrosome reaction, impaired fertilization, influence on the implantation process, and impaired growth and development of the embryo. As of 2017 research was ongoing in several areas related to ASA. Research has been conducted, but not clinically tested, to use sperm antigens or recombinant ASAs as contraceptive vaccines for humans, as well as captive and wild animals. The mechanisms through which both women and men develop ASA is

pos: Human fertilization undergo capacitation in the female's reproductive tract over several hours, which increases its motility and destabilizes its membrane, preparing it for the acrosome reaction, the enzymatic penetration of the egg's tough membrane, the zona pellucida, which surrounds the oocyte. After binding to the corona radiata the sperm reaches the zona pellucida, which is an extra-cellular matrix of glycoproteins. A special complementary molecule on the surface of the sperm head binds to a ZP3 glycoprotein in the zona pellucida. This binding triggers the acrosome to burst, releasing enzymes that help the sperm get through the zona pellucida. Some sperm cells consume

pos: Acrosome reaction same trend. The acrosome reaction can be stimulated in vitro by substances a sperm cell may encounter naturally such as progesterone or follicular fluid, as well as the more commonly used calcium ionophore A23187. Birefringence microscopy, flow cytometry or fluorescence microscopy can be used for assessing the shedding of the acrosome or "acrosome reaction" of a sperm sample. Flow cytometry and fluorescence microscopy are usually done after staining with a fluoresceinated lectin such as FITC-PNA, FITC-PSA, FITC-ConA, or fluoresceinated antibody such as FITC-CD46. The antibodies/lectins have a high specificity for different parts of the acrosomal region, and will only bind

pos: Hamster zona-free ovum test whose sperm fail the hamster test are a third as fertile than those whose sperm pass. Donated sperm and intracytoplasmic sperm injection techniques are considered more strongly for those whose sperm fail this test. Contrary to some assertions by medical professionals, if the human sperm penetrates the hamster egg, a hybrid embryo is indeed created. The resulting hamster-hybrid is known as a humster. These embryos are typically destroyed before they divide into two cells and are never known to have been implanted in either a hamster or human uterus to develop. This test evaluates the acrosome reaction of human spermatozoa.

pos: Testicular immunology "Chlamydia trachomatis" which infects the genitals. It more commonly affects women, and if untreated, can lead to pelvic inflammatory disease and infertility. Serious symptoms in men are rare, but include swollen testicles and an unusual discharge from the penis. It is effectively treated with antibiotics. Antisperm antibodies (ASA) have been considered as infertility cause in around 10–30% of infertile couples. ASA production are directed against surface antigens on sperm, which can interfere with sperm motility and transport through the female reproductive tract, inhibiting capacitation and acrosome reaction, impaired fertilization, influence on the implantation process, and impaired growth and development of

pos: Asthenozoospermia which allows the fluidy of the membrane, necessary to the fusion with the ovule. Studies in mice have shown that DHA is essential for acrosome reaction and a DHA deficiency results in abnormal sperm morphology, lost of motility and infertility; which can be restored by dietary DHA supplementation. Futhermore, the supplementation with DHA in human has been reported to increase sperm motility. But also, DHA supplement can protect spermatozoa against the damage caused by the cryopresevation process. González-Ravina, Cristina; Aguirre-Lipperheide, Mercedes; Pinto, Francisco; Martín-Lozano, David; Fernández-Sánchez, Manuel; Blasco, Víctor; Santamaría-López, Esther; Candenas, Luz (2018). "Effect of dietary supplementation with a

pos: Biochemical cascade the ability to fertilize the female gamete, this cell suffers capacitation and acrosome reaction in female reproductive tract. The signaling pathways best described for spermatozoon involve these processes. The cAMP/PKA signaling pathway leads to sperm cells capacitation; however, adenilyl cyclase in sperm cells is different from the somatic cells. Adenilyl cyclase in spermatozoon doesn't recognize G proteins, so it is stimulated by bicarbonate and Ca ions. Then, it converts ATP into cAMP, which activates PKA. PKA leads to protein tyrosine phosphorylation. Phospholipase C (PLC) is involved in acrosome reaction. ZP3 is a glycoprotein present in zona pelucida and it interacts

pos: Hyperactivation epithelium. Thus, only those sperm which have undergone hyperactivation have the ability to fertilize the egg. Hyperactivation Hyperactivation is a type of sperm motility. Hyperactivated sperm motility is characterised by a high amplitude, asymmetrical beating pattern of the sperm tail (flagellum). This type of motility may aid in sperm penetration of the zona pellucida, which encloses the ovum. Hyperactivation could then be followed by the acrosome reaction where the cap-like structure on the head of the cell releases the enzymes it contains. This facilitates the penetration of the ovum and fertilisation. Some definitions consider sperm activation to consist of these

pos: Reproductive immunology and hopefully will be an effective contraceptive for humans. Normally, spermatozoa fuse with the zona pellucida surrounding the mature oocyte; the resulting acrosome reaction breaks down the egg's tough coating so that the sperm can fertilize the oovum. The mechanism of the vaccine is injection with cloned ZP cDNA, therefore this vaccine is a DNA based vaccine. This results in the production of antibodies against the ZP, which stop the sperm from binding to the zona pellucida and ultimately from fertilizing the oovum. Another vaccine in investigation is one against HCG. This immunization would produce antibodies against hCG and TT.

pos: Female infertility menopausal levels after four series. Other hormonal changes in chemotherapy include decrease in inhibin B and anti-Müllerian hormone levels. Women may choose between several methods of fertility preservation prior to chemotherapy, including cryopreservation of ovarian tissue, oocytes or embryos. Antisperm antibodies (ASA) have been considered as infertility cause in around 10–30% of infertile couples. ASA production are directed against surface antigens on sperm, which can interfere with sperm motility and transport through the female reproductive tract, inhibiting capacitation and acrosome reaction, impaired fertilization, influence on the implantation process, and impaired growth and development of the embryo. Factors contributing to the

pos: VEZT to the fusion of the sperm with the egg as, it is the outer acrosomal domain which initiates the acrosome reaction, enabling the sperm to fuse. Vezatin is present in both these domains, but the translocation of vezatin from the inner to the outer membrane is unknown. Furthermore, vezatin is not expressed in the epididymal cells, thus vezatin cannot be added to the exterior membrane during maturation of the spermatozoa. However, knowledge of the localisation of vezatin in this outer membrane and its known role in adherens junctions suggests that it plays a role in the fusion of the mammalian

pos: Intracytoplasmic sperm injection twin pregnancies with a second gestational sac with a dead fetus, first trimester screening should be based solely on the maternal age and the nuchal translucency scan as biomarkers are significantly altered in these cases. Intracytoplasmic sperm injection Intracytoplasmic sperm injection (ICSI ) is an in vitro fertilization (IVF) procedure in which a single sperm cell is injected directly into the cytoplasm of an egg. This technique is used in order to prepare the gametes for the obtention of embryos that may be transferred to a maternal uterus. With this method acrosome reaction is skipped. There are several differences within

pos: Intracytoplasmic sperm injection Intracytoplasmic sperm injection Intracytoplasmic sperm injection (ICSI ) is an in vitro fertilization (IVF) procedure in which a single sperm cell is injected directly into the cytoplasm of an egg. This technique is used in order to prepare the gametes for the obtention of embryos that may be transferred to a maternal uterus. With this method acrosome reaction is skipped. There are several differences within classic IVF and ICSI. However, the steps to be followed before and after insemination are the same. In terms of insemination, ICSI needs one only sperm cell per oocyte, meanwhile IVF needs between 50 and

pos: Acrosome reaction unable to properly go through the acrosome reaction will not be able to fertilize an egg. However, this problem only occurs in about 5% of men that have the test done. This test is rather expensive and provides limited information on a man's fertility. In other cases, such as in the wood mouse "Apodemus sylvaticus", premature acrosome reactions have been found to cause increased motility in aggregates of spermatozoa promoting fertilization. The acrosomal reaction normally takes place in the ampulla of the fallopian tube (site of fertilization) when the sperm penetrates the secondary oocyte. A few events precede the actual

pos: Human fertilization be expelled by exocytosis to the zona pellucida. This in turn causes the glyco-proteins in the zona pellucida to cross-link with each other — i.e. the enzymes cause the ZP2 to hydrolyse into ZP2f — making the whole matrix hard and impermeable to sperm. This prevents fertilization of an egg by more than one sperm. The cortical reaction and acrosome reaction are both essential to ensure that only one sperm will fertilize an egg. After the sperm enters the cytoplasm of the oocyte (also called ovocyte), the tail and the outer coating of the sperm disintegrate and the cortical reaction

pos: Capacitation not require this capacitation step and are ready to fertilize an oocyte immediately after release from the male. After this capacitation, the sperm must undergo the final maturation step, activation, involving the acrosome reaction. Historically, the term "capacitation" has evolved in meaning and this should be taken into account when consulting sources. Capacitation has 2 effects: destabilisation of the acrosomal sperm head membrane which allows it to penetrate the outer layer of the egg, and chemical changes in the tail that allow a greater mobility in the sperm. The changes are facilitated by the removal of sterols (e.g. cholesterol) and

pos: ADCY10 ADCY10 Adenylyl cyclase 10 also known as ADCY10 is an enzyme that, in humans, is encoded by the "ADCY10" gene. The protein encoded by this gene belongs to a distinct class of mammalian adenylyl cyclase that is soluble and insensitive to G protein or forskolin regulation. It is localized in the cytoplasm and is thought to function as a general bicarbonate sensor throughout the body. It may also play an important role in the generation of cAMP in spermatozoa, implying possible roles in sperm maturation through the epididymis, capacitation, hypermotility, and/or the acrosome reaction. Mutations in the "ADCY10" gene are

pos: Veratridine progesterone-induced acrosome reaction. Veratridine Veratridine is a steroidal alkaloid found in plants of the lily family, specifically the genera "Veratrum" and "Schoenocaulon". Upon absorption through the skin or mucous membranes, it acts as a neurotoxin by binding to and preventing the inactivation of voltage-gated sodium ion channels in heart, nerve, and skeletal muscle cell membranes. Veratridine increases nerve excitability and intracellular Ca concentrations. Veratridine has been isolated from the seeds of "Schoenocaulon officinale" and from the rhizomes of "Veratrum album." Like the other steroidal alkaloids found in these plants and similar ones in the Melanthiaceae family, it is present as

pos: Veratridine its own, but it is able to block the progesterone-induced acrosome reaction. Moreover, veratridine has the effect of turning the membrane potential to a more positive one and also modiﬁes the eﬀect of progesterone on [Ca2+]i and sperm membrane potential. The activation of Nav1.8 is a key point in Veratradine's mechanism of action and, consequently, this sodium ion channel coordinates the effects of this compound. Veratradine also activates additional Nav channels. These facts contribute to support the importance of these Veratradine-sensitive proteins in the regulation of mature sperm function, such as human sperm fertility acquisition regulating motility, capacitation and the

pos: Zona pellucida system), the zona glycoprotein, ZP3, is responsible for sperm binding, adhering to proteins on the sperm plasma membrane (GalT). ZP3 is then involved in the induction of the acrosome reaction, whereby a spermatozoon releases the contents of the acrosomal vesicle. The exact characterisation of what occurs in other species has become more complicated as further zona proteins have been identified. In humans, five days after the fertilization, the blastocyst performs zona hatching; the zona pellucida degenerates and decomposes, to be replaced by the underlying layer of trophoblastic cells. The zona pellucida is essential for oocyte growth and fertilization. In some

pos: GPX5 GPX5 Glutathione peroxidase 5 (GPx-5), also known as epididymal secretory glutathione peroxidase is an enzyme that in humans is encoded by the "GPX5" gene. GPx-5 belongs to the glutathione peroxidase family. It is specifically expressed in the epididymis in the mammalian male reproductive tract, and is androgen-regulated. Unlike mRNAs for other characterized glutathione peroxidases, this mRNA does not contain a selenocysteine (UGA) codon. Thus, the encoded protein is selenium-independent, and has been proposed to play a role in protecting the membranes of spermatozoa from the damaging effects of lipid peroxidation and/or preventing premature acrosome reaction. Alternatively spliced transcript variants encoding

pos: Acrosin the zymogen form of the protease is then processed into its active form, β-acrosin. The active enzyme then functions in the lysis of the zona pellucida, thus facilitating penetration of the sperm through the innermost glycoprotein layers of the ovum. The importance of acrosin in the acrosome reaction has been contested. It has been found through genetic knockout experiments that mouse spermatozoa lacking β-acrosin (the active protease) still have the ability to penetrate the zona pellucida. Thus, some argue for its role in assisting in the dispersal of acrosomal contents following the acrosome reaction, while others demonstrate evidence for its

pos: Intracytoplasmic sperm injection 100 thousands. This is due to the fact that in IVF acrosome reaction has to take place and thousands of sperm cells have to be involved. Once fertilized, the egg is transformed into a proembryo and it has to be transferred to the uterus to continue its development. The first human pregnancy generated by ICS was carried out in 1991 by Gianpiero Palermo and his team. Round spermatid injection (ROSI) is a technique of assisted reproduction whereby a round spermatid is injected into oocyte cytoplasm in order to achieve fertilization. This technique can be used to enable genetic fatherhood to

pos: Infertility and transport through the female reproductive tract, inhibiting capacitation and acrosome reaction, impaired fertilization, influence on the implantation process, and impaired growth and development of the embryo. Factors contributing to the formation of antisperm antibodies in women are disturbance of normal immunoregulatory mechanisms, infection, violation of the integrity of the mucous membranes, rape and unprotected oral or anal sex. Risk factors for the formation of antisperm antibodies in men include the breakdown of the blood‑testis barrier, trauma and surgery, orchitis, varicocele, infections, prostatitis, testicular cancer, failure of immunosuppression and unprotected receptive anal or oral sex with men. Infections with the

pos: Hamster zona-free ovum test However, the incidence of acrosome reaction in freely swimming human sperm does not accurately reflect the fertilizing ability of the sperm. The practice is made licensable in the United Kingdom by the Human Fertilisation and Embryology Act 1990. This test has a poor predictive value for the success of fertilization in IVF treatment at any insemination concentration. No strong correlation has been found between hamster egg penetration rates and the various semen parameters and the role of the hamster egg penetration test in the investigation of the causes of infertility should be evaluated further. However, a negative result on the

pos: AKAP3 fibrous sheath in the principal piece of the sperm tail. It may function as a regulator of both motility- and head-associated functions such as capacitation and the acrosome reaction. AKAP3 has been shown to interact with: AKAP3 A-kinase anchor protein 3 is an enzyme that in humans is encoded by the "AKAP3" gene. The A-kinase anchor proteins (AKAPs) are a group of structurally diverse proteins, which have the common function of binding to the regulatory subunit of protein kinase A (PKA) and confining the holoenzyme to discrete locations within the cell. This gene encodes a member of the AKAP family,

pos: Veratridine applicability as a neuropharmacological tool for the study of electrical properties of nerve and muscle fibers. It has also been tested as a treatment for myasthenia gravis, in light of its potential to increase muscle responses to motor neuron stimulation. Furthermore, this compound has recently been reported to increase sperm progressive motility (although it does not produce hyperactivation by itself). It has the potential of enhancing protein tyrosine phosphorylation, which takes place during capacitation, and its eﬀects are inhibited in the presence of lidocaine and tetrodotoxin. Veratridine has not been reported to have any eﬀect on the acrosome reaction on

pos: Acrosome reaction pellucida of the egg, which is necessary for initiating the acrosome reaction, the membrane surrounding the acrosome fuses with the plasma membrane of the sperm's head, exposing the contents of the acrosome. The contents include surface antigens necessary for binding to the egg's cell membrane, and numerous enzymes which are responsible for breaking through the egg's tough coating and allowing fertilization to occur. There are considerable species variations in the morphology and consequences of the acrosome reaction. In several species the trigger for the acrosome reaction has been identified in a layer that surrounds the egg. In some lower animal

neg: Human embryogenesis directs the movement of the sperm towards the ovum. Secondly there is an adhesive compatibility between the sperm and the egg. With the sperm adhered to the ovum, the third process of acrosomal reaction takes place; the front part of the spermatozoan head is capped by an acrosome which contains digestive enzymes to break down the zona pellucida and allow its entry. The entry of the sperm causes calcium to be released which blocks entry to other sperm cells. A parallel reaction takes place in the ovum called the zona reaction. This sees the release of cortical granules that release

neg: Acrosome reaction the sperm. Upon penetration, if all is occurring normally, the process of egg-activation occurs and the oocyte is said to have become activated. This is thought to be induced by a specific protein phospholipase c zeta. It undergoes its secondary meiotic division, and the two haploid nuclei (paternal and maternal) fuse to form a zygote. In order to prevent polyspermy and minimise the possibility of producing a triploid zygote, several changes to the egg's cell membranes renders them impenetrable shortly after the first sperm enters the egg. The aforementioned process describes the physiologically relevant events. One should however bear in

neg: Human fertilization Upon encountering the secondary oocyte, the acrosome of the sperm produces enzymes which allow it to burrow through the outer jelly coat of the egg. The sperm plasma, then fuses with the egg's plasma membrane, the sperm head disconnects from its flagellum and the egg travels down the Fallopian tube to reach the uterus. In vitro fertilization (IVF) is a process by which egg cells are fertilized by sperm outside the womb, "in vitro". The sperm binds through the corona radiata, a layer of follicle cells on the outside of the secondary oocyte. Fertilization occurs when the nucleus of both

neg: VEZT almost always expressed with vezatin but the absence of this partnership within the testis is yet to be fully understood. However, vezatin has been shown to be expressed within the acrosomal region of the actual spermatozoa. Vezatin is not found in the early spermatid but only appears when the formation of the acrosome occurs later on in the process of spermatogenesis. The acrosome itself is divided into two functional domains, the inner acrosomal membrane which faces the nucleus and the outer acrosomal membrane which is in contact with the exterior surfaces of the sperm. This compartmentalisation of functions is vital

neg: Acrosome reaction to a specific site (acrosomal content/ inner/outer membrane). If bound to a fluorescent molecule, regions where these probes have bound can be visualised. Sperm cells with artificially induced acrosome reactions may serve as positive controls. For fluorescence microscopy a smear of washed sperm cells are made, airdried, permealized and then stained. Such a slide is then viewed under light of a wavelength that will cause the probe to fluoresce if it is bound to the acrosomal region. At least 200 cells are viewed in an arbitrary fashion and classified as either acrosome intact (fluorescing bright green) or acrosome reacted (no

neg: Corona radiata (embryology) primary stage. These cuboidal granulosa cells, also known as the granulosa radiata, form more layers throughout the maturation process, and remain attached to the zona pellucida after the ovulation of the Graafian follicle. For fertilization to occur, sperm cells rely on hyaluronidase (an enzyme found in the acrosome of spermatozoa) to disperse the corona radiata from the zona pellucida of the secondary (ovulated) oocyte, thus permitting entry into the perivitelline space and allowing contact between the sperm cell and the nucleus of the oocyte. Corona radiata (embryology) The corona radiata is the innermost layer of the cells of the cumulus

neg: Human fertilization their acrosome prematurely on the surface of the egg cell, facilitating the penetration by other sperm cells. As a population, sperm cells have on average 50% genome similarity so the premature acrosomal reactions aid fertilization by a member of the same cohort. It may be regarded as a mechanism of kin selection. Recent studies have shown that the egg is not passive during this process. Once the sperm cells find their way past the zona pellucida, the cortical reaction occurs. Cortical granules inside the secondary oocyte fuse with the plasma membrane of the cell, causing enzymes inside these granules to

neg: Acroplaxome Acroplaxome Spermatozoa develop in the seminiferous tubules of the testes. During their development the spermatogonia proceed through meiosis to become spermatozoa. Many changes occur during this process: the DNA in nuclei becomes condensed; the acrosome develops as a structure close to the nucleus. The acrosome is derived from the Golgi apparatus and contains hydrolytic enzymes important for fusion of the spermatozoon with an egg cell. During spermiogenesis the nucleus condenses and changes shape. Abnormal shape change is a feature of sperm in male infertility. The acroplaxome is a structure found between the acrosomal membrane and the nuclear membrane. The acroplaxome

neg: Acroplaxome contains structural proteins including keratin 5, F-actin and profilin IV. Acroplaxome Spermatozoa develop in the seminiferous tubules of the testes. During their development the spermatogonia proceed through meiosis to become spermatozoa. Many changes occur during this process: the DNA in nuclei becomes condensed; the acrosome develops as a structure close to the nucleus. The acrosome is derived from the Golgi apparatus and contains hydrolytic enzymes important for fusion of the spermatozoon with an egg cell. During spermiogenesis the nucleus condenses and changes shape. Abnormal shape change is a feature of sperm in male infertility. The acroplaxome is a structure found

neg: Globozoospermia People with globozoospermia have normal physical and mental development, normal clinical features and normal hormonal profile. The presence of round headed sperm in a semen analysis sample confirms the diagnosis of globozoospermia. The lack of acrosome can be ascertained by a technique known as immunofluorescence. Until 1995, the only options for people with globozoospermia who wished to conceive were adoption or sperm donation. With the advancement of assisted reproductive techniques (ART) it is now possible for those with globozoospermia to conceive using their own sperm. The main technique used is intracytoplasmic sperm injection (ICSI) where fertilisation is achieved by a

neg: Globozoospermia Globozoospermia Globozoospermia (also known as round-headed sperm syndrome) is a rare and severe form of monomorphic teratozoospermia. This means that the spermatozoa show the same abnormality, and over 85% of spermatozoa in sperm have this abnormality. Globozoospermia is responsible for less than 0.1% of male infertility. It characterised by round-headed spermatozoa without acrosome, an abnormal nuclear membrane and midpiece defects. Affected males therefore suffer from either reduced fertility or infertility. Studies suggest that globozoospermia can be either total (100% round-headed spermatozoa without acrosomes) or partial (20-60% round acrosomeless spermatozoa with normal sperm also identified in the sperm count,) however it

neg: Vasectomy hormones that continue to be secreted into the bloodstream. Some studies have found that sexual desire after vasectomy may be somewhat diminished. When the vasectomy is complete, sperm cannot exit the body through the penis. Sperm are still produced by the testicles, but they are soon broken down and absorbed by the body. Much fluid content is absorbed by membranes in the epididymis, and much solid content is broken down by the responding macrophages and reabsorbed via the bloodstream. Sperm is matured in the epididymis for about a month before leaving the testicles. After vasectomy, the membranes must increase in

neg: Acrosome reaction from binding. There is some evidence that this binding is what triggers the acrosome to release the enzymes that allow the sperm to fuse with the egg. It is likely that a similar mechanism occurs in other mammals, but the diversity of zona proteins across species means that the relevant protein and receptor may differ. More recent scientific evidence demonstrate the acrosomal reaction is necessary to expose a protein called IZUMO1 on the sperm, however, it is not critical for penetration of the egg shell or zona pellucida. As seen in mouse studies, IZUMO1 binds to the oocyte protein JUNO

neg: Acrosome reaction and once bound together, the sperm and the egg fuse together to form two pronuclei These pronuclei supply the zygote with the genetic material necessary for the formation of an embryo. Additionally, once the fusion of the sperm and oocyte is complete, phospholipase C zeta is released from the sperm. As the sperm arrive at the egg, it is the egg that chooses the sperm and pulls it towards her. The selected sperm actually tries to swim away from the egg but is tethered to the egg by female hormones. The membrane around the egg literally opens up and swallows

neg: Acrosome reaction probe present, or only on the equatorial region). It is then expressed as a percentage of the counted cells. For assessment with flow cytometry the washed cells are incubated with the chosen probe, (possibly washed again) and then sampled in a flow cytometer. After gating the cell population according to forward- and side-scatter the resulting data can be analysed (E.g. mean fluorescences compared). With this technique a probe for viability, like propidium iodide (PI) could also be included in order to exclude dead cells from the acrosome assessment, since many sperm cells will spontaneously lose their acrosome when they die.

neg: Globozoospermia also looks at causing oocyte activation in conjunction with ICSI, this time using spermatic binding-proteins, phospholipase C zeta (PLCζ) and postacrosomal sheath WW domain binding protein (PAWP). Globozoospermia Globozoospermia (also known as round-headed sperm syndrome) is a rare and severe form of monomorphic teratozoospermia. This means that the spermatozoa show the same abnormality, and over 85% of spermatozoa in sperm have this abnormality. Globozoospermia is responsible for less than 0.1% of male infertility. It characterised by round-headed spermatozoa without acrosome, an abnormal nuclear membrane and midpiece defects. Affected males therefore suffer from either reduced fertility or infertility. Studies suggest that

neg: Oocyte activation In most cells, this occurs at the cell membrane however, evidence suggests that the PIP required for oocyte activation is potentially stored in intracellular vesicles dispersed throughout the cytoplasm. The IP produced then triggers calcium oscillations which reactivate the meiotic cycle. This results in the production and extrusion of the second polar body. 4 hours after fusion of sperm and ovum, DNA synthesis begins. Male and female pronuclei move to the centre of the egg and membranes break down. Male protamines are replaced with histones and the male DNA is demethylated. Chromosomes then orientate on the metaphase spindle for mitosis.

neg: Double fertilization producing two sperm cells. Once the pollen grain has matured, the anthers break open, releasing the pollen. The pollen is carried to the pistil of another flower, by wind or animal pollinators, and deposited on the stigma. As the pollen grain germinates, the tube cell produces the pollen tube, which elongates and extends down the long style of the carpel and into the ovary, where its sperm cells are released in the megagametophyte. Double fertilization proceeds from here. Double fertilization "Double fertilization" is a complex fertilization mechanism of flowering plants (angiosperms). This process involves the joining of a female gametophyte

neg: Cysteine-rich secretory protein venom ophanin, for example, has 16 strictly conserved cysteines in addition to 8 disulfide bonds. CRISPs are found in the testes and epididymis of mammals, and are also involved in the process of fertilisation. In the spermatogenesis process (development of the spermatozoa in the testis), the CRISP2 protein is incorporated into the acrosome where it is believed to be involved in the adhesion of germ cells with Sertoli cells. CRISP2 also forms part of the sperm tail where it is thought to be involved in regulating flagellar beating. Proteins CRISP1 and CRISP4 are both found in the epididymis where they

neg: Cortical reaction the acrosomal reaction within the sperm, where the acrosome, a specialized secretory vesicle that is homologous to cortical granules, is fused with the plasma membrane of the sperm cell to release its contents which degrade the egg's tough coating and allow the sperm to bind to and fuse with the egg. In the well-studied sea urchin model system, the granule contents modify a protein coat on the outside of the plasma membrane (the vitelline layer) so that it is released from the membrane. The released cortical granule proteins exert a colloid osmotic pressure causing water to enter the space between

neg: Spermatozoon and the exposure of enzymes attached to the inner acrosomal membrane of the sperm. This occurs after the sperm first meets the egg. This lock-and-key type mechanism is species-specific and prevents the sperm and egg of different species from fusing. There is some evidence that this binding is what triggers the acrosome to release the enzymes that allow the sperm to fuse with the egg. ZP3, one of the proteins that make up the zona pellucida, then binds to a partner molecule on the sperm. Enzymes on the inner acrosomal membrane digest the zona pellucida. After the sperm penetrates the

neg: Teratospermia Teratospermia Teratospermia or teratozoospermia is a condition characterized by the presence of sperm with abnormal morphology that affects fertility in males. The causes of teratozoospermia are unknown in most cases. However, Hodgkin's disease, coeliac disease, and Crohn's disease may contribute in some instances. Lifestyle and habits (smoking, toxin exposure, etc.) can also cause poor morphology. Varicocele is another condition that is often associated with decreased normal forms (morphology). In cases of globozoospermia (sperm with round heads), the Golgi apparatus is not transformed into the acrosome that is needed for fertilization. The presence of abnormally-shaped sperm can negatively affect fertility by

neg: Sperm competition faces an intermediate number of challenges from other males compared to exclusive polygyny and monogamy but frequent sperm competition. Other means of sperm competition could include improving the sperm itself or its packaging materials (spermatophore). The male black-winged damselfly provides a striking example of an adaptation to sperm competition. Female black-winged damselflies are known to mate with several males over the span of only a few hours and therefore possess a receptacle known as a spermatheca which stores the sperm. During the process of mating the male damselfly will pump his abdomen up and down using his specially adapted penis

neg: Fertility testing semen testing and genetic testing, as other factors such as impotence are obvious. Semen can be tested for sperm count, sperm motility, sperm morphology, pH, volume, fructose content, and acrosome activity. Checks are also made to identify undescended testicles and retrograde ejaculation, along with medical history, such as cancer treatment, radiation, drug use, etc. In some cases the hamster zona-free ovum test may also be used to diagnose fertility. Genetic testing and chromosomal analysis can rule out some other causes of male infertility, such as Klinefelter syndrome. A recent study identified epigenetic patterns in male sperm that may contribute to

neg: Male infertility Male infertility Male infertility refers to a male's inability to cause pregnancy in a fertile female. In humans it accounts for 40–50% of infertility. It affects approximately 7% of all men. Male infertility is commonly due to deficiencies in the semen, and semen quality is used as a surrogate measure of male fecundity. Factors relating to male infertility include: Antisperm antibodies (ASA) have been considered as infertility cause in around 10–30% of infertile couples. ASA production are directed against surface antigens on sperm, which can interfere with sperm motility and transport through the female reproductive tract, inhibiting capacitation and acrosome

neg: Sperm bank Sperm bank A sperm bank, semen bank or cryobank is a facility or enterprise which purchases and stores human semen from men known as sperm donors for use by women who wish to use donor-provided sperm to achieve a pregnancy or pregnancies. Sperm sold by a sperm donor is known as donor sperm. Sperm is introduced into the recipient woman by means of artificial insemination or by IVF and the process may also involve donated eggs or the use of a surrogate. From a medical perspective, a pregnancy achieved using donor sperm is no different from a pregnancy achieved using

neg: Pronucleus Pronucleus A pronucleus (plural: pronuclei) is the nucleus of a sperm or an egg cell during the process of fertilization, after the sperm enters the ovum, but before the genetic material of the sperm and egg fuse. Sperm and egg cells are haploid, meaning they carry half the number of chromosomes of somatic cells. The male and female pronuclei don't fuse, although their genetic material does. Instead, their membranes dissolve, leaving no barriers between the male and female chromosomes. Their chromosomes can then combine and become part of a single diploid nucleus in the resulting embryo, containing a full set

neg: Fertilisation the oocyte. Fusion between the oocyte plasma membranes and sperm follows and allows the sperm nucleus, the typical centriole, and atypical centriole that is attached to the flagellum, but not the mitochondria, to enter the oocyte. The protein CD9 likely mediates this fusion in mice (the binding homolog). The egg "activates" itself upon fusing with a single sperm cell and thereby changes its cell membrane to prevent fusion with other sperm. Zinc atoms are released during this activation. This process ultimately leads to the formation of a diploid cell called a zygote. The zygote divides to form a blastocyst and,

neg: Acrosome reaction the sperm cell reaches the zona pellucida. Acrosin digests the zona pellucida and membrane of the oocyte. Part of the sperm's cell membrane then fuses with the egg cell's membrane, and the contents of the head sink into the egg. In the mouse it has been demonstrated that ZP3, one of the proteins that make up the zona pellucida, binds to a partner molecule (to the β1,4-galactosyl transferase receptors) on the sperm. This lock-and-key type mechanism is species-specific and prevents the sperm and egg of different species from fusing. The zona pellucida also releases Ca granules to prevent additional sperm

neg: Sertoli cell Sertoli cell A Sertoli cell (a kind of sustentacular cell) is a "nurse" cell of the testicles that is part of a seminiferous tubule and helps in the process of spermatogenesis, the production of sperm. It is activated by follicle-stimulating hormone (FSH) secreted by the adenohypophysis, and has FSH receptor on its membranes. It is specifically located in the convoluted seminiferous tubules (since this is the only place in the testes where the spermatozoa are produced). Development of Sertoli cells is directed by the testis-determining factor protein. Because its main function is to nourish the developing sperm cells through the

neg: Scaling and root planing removing stain, plaque and calculus. In addition, ultrasonic scalers create tiny air bubbles through a process known as cavitation. These bubbles serve an important function for periodontal cleanings. Since the bacteria living in periodontically involved pockets are anaerobic, meaning unable to survive in the presence of oxygen, these bubbles help to destroy them. The oxygen helps to break down bacterial cell membranes and causes them to lyse, or burst. Since it is of the utmost importance to remove the entirety of the deposit in each periodontal pocket, attention to detail during this procedure is crucial. Therefore, depending on the depth

neg: Sperm donation in other assisted reproductive techniques such as IVF and intracytoplasmic sperm injection (ICSI). Donor sperm may also be used in surrogacy arrangements either by artificially inseminating the surrogate (known as traditional surrogacy) or by implanting in a surrogate embryos which have been created by using donor sperm together with eggs from a donor or from the 'commissioning female' (known as "gestational surrogacy"). Spare embryos from this process may be donated to other women or surrogates. Donor sperm may also be used for producing embryos with donor eggs which are then donated to a female who is not genetically related to

neg: Human fertilization takes place, preventing other sperm from fertilizing the same egg. The oocyte now undergoes its second meiotic division producing the haploid ovum and releasing a polar body. The sperm nucleus then fuses with the ovum, enabling fusion of their genetic material. The fusion of cell membranes of the secondary oocyte and sperm takes place. In preparation for the fusion of their genetic material both the oocyte and the sperm undergo transformations as a reaction to the fusion of cell membranes. The oocyte completes its second meiotic division. This results in a mature ovum. The nucleus of the oocyte is called

neg: Cancer-associated fibroblast been found to upregulate specific genes involved in pro-tumorigenic pathways including heat shock factor 1 (HSF1). They can also interfere with the function of tumour suppressor genes, such as Tumour protein p53, leading to higher rates of cell proliferation due to the loss of control of the cell cycle. Additionally, CAF have the ability to break down proteins in the extracellular matrix and basement membranes leading to disruption to the normal structure allowing cells to move away from their primary region. The group of proteins known as the matrix metalloproteinases are key to this process. CAF also direct the movement

neg: Sperm washing in infertility treatment. Sperm washing takes place in a laboratory following sperm donation. Sperm may be washed by density gradient centrifugation or by a ""direct swim-up"" technique that does not involve centrifugation. In normal semen samples, centrifugation causes no more DNA damage to spermatozoa than a direct swim-up technique. Washed sperm is concentrated in Hams F10 media without L-glutamine, warmed to . A chemical known as a cryoprotectant is added to the sperm to aid the freezing and thawing process. Further chemicals may be added which separate the most active sperm in the sample, as well as extend or dilute

neg: Wrinkle-faced bat to be both polyestrous and asynchronous, pregnant females have been recorded every month between January and August except May. Males emit a musky odour from the chin area to attract females. Their sperm morphology is unique in that the sperm head has a rounded nucleus and extremely pointed acrosome. "C. senex" subsp. "senex" is found in Belize, Colombia, Costa Rica, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama and Venezuela. "C. senex" subsp. "greenhalli" is only found in Trinidad and Tobago. The binomial name "Centurio senex" is formed from the Latin "centurio" meaning division into hundreds and "senex" referring to old

neg: Vasectomy size to absorb and store more fluid; this triggering of the immune system causes more macrophages to be recruited to break down and reabsorb more solid content. Within one year after vasectomy, sixty to seventy percent of vasectomized men develop antisperm antibodies. In some cases, vasitis nodosa, a benign proliferation of the ductular epithelium, can also result. The accumulation of sperm increases pressure in the vas deferens and epididymis. The entry of the sperm into the scrotum can cause sperm granulomas to be formed by the body to contain and absorb the sperm which the body will treat as a

neg: Reproductive system sometimes to a unique pore such as a vagina or intromittent organ. The human reproductive system usually involves internal fertilization by sexual intercourse. During this process, the male inserts his erect penis into the female's vagina and ejaculates semen, which contains sperm. The sperm then travels through the vagina and cervix into the uterus or fallopian tubes for fertilization of the ovum. Upon successful fertilization and implantation, gestation of the fetus then occurs within the female's uterus for approximately nine months, this process is known as pregnancy in humans. Gestation ends with birth, the process of birth is known as

neg: Industrial applications of nanotechnology water repellent coating based on the actions of the lotus leaf as a result of the incorporation of silica and alumina nanoparticles and hydrophobic polymers. Mechanical studies of bones have been adapted to model wood, for instance in the drying process. Research is being carried out on the application of nanotechnology to glass, another important material in construction. Titanium dioxide (TiO) nanoparticles are used to coat glazing since it has sterilizing and anti-fouling properties. The particles catalyze powerful reactions that break down organic pollutants, volatile organic compounds and bacterial membranes. TiO is hydrophilic (attraction to water), which can attract rain

neg: Rust (fungus) which end at the stoma. Inside the stoma, the hyphae tips flatten out to form structures known as appressoria that lock to the cell walls. It is thought that the whole process is mediated by a mechano-sensitive calcium ion channel, located within the germ tube tip, which produces electric currents that stretch the cell membranes, changing gene expression and forming the appresorium. Then a peg grows into the plant's mesophyll cells. The peg produces specialised hyphal tips, known as haustoria. These spread around the plant cells without invading the membranes. The plant cell membranes invaginate around the main haustorial body

neg: Sperm motility mitochondria. The velocity of a sperm in fluid medium is usually 1–4 mm/min. This allows the sperm to move towards an ovum in order to fertilize it. In mammals, spermatozoa mature functionally through a process which is known as capacitation. When spermatozoa reach the isthmic oviduct, their motility has been reported to be reduced as they attach to epithelium. Near the time of ovulation, hyperactivation occurs. During this process, the flagella move with high curvature and long wavelength. Hyperactivation is initiated by extracellular calcium; however, the factors that regulate calcium level is unknown. Without technological intervention, a non-motile or abnormally-motile

neg: Human reproduction a sperm may penetrate and merge with the egg, fertilizing it with the help of certain hydrolytic enzymes present in the acrosome. The fertilization usually occurs in the oviducts, but can happen in the uterus itself. The zygote then becomes implanted in the lining of the uterus, where it begins the processes of embryogenesis and morphogenesis. When the fetus is developed enough to survive outside of the uterus, the cervix dilates and contractions of the uterus propel it through the birth canal, which is the vagina. The ova, which are the female sex cells, are much larger than the spermatozoon

neg: Female sperm storage sperm are received by the mesospermalege and eventually reach the spermathecae, also referred to as seminal conceptacles. At the microscopic level, "Drosophila" males have differing sperm tail lengths that correspond to various sizes of female seminal receptacles. Longer male sperm tail length has shown a greater reproductive success with a larger female seminal receptacle while sperm with short tail lengths have been found to be more successful in smaller seminal receptacles. The ability to store and separate sperm from multiple males enables females to manipulate paternity by choosing which sperm fertilize their eggs, a process known as cryptic female choice.

neg: Acrosin binding protein is detected in a range of different tumor types such as bladder, breast, lung, liver, and colon. Acrosin binding protein Acrosin binding protein is a protein that in humans is encoded by the ACRBP gene. The protein encoded by this gene is similar to proacrosin binding protein sp32 precursor found in mouse, guinea pig, and pig. This protein is located in the sperm acrosome and is thought to function as a binding protein to proacrosin for packaging and condensation of the acrosin zymogen in the acrosomal matrix. This protein is a member of the cancer/testis family of antigens and it

neg: Female sperm storage proteases that break down various proteins in male seminal fluid resulting in female selection in sperm. Like females, males have developed responses to counter evolutionary adaptations of the opposite sex. Responses in insects can vary in both genitalia and sperm structures, along with variations in behavior. Spiny male genitalia help to anchor the male to the female during copulation and remove sperm of previous males from female storage structures. Males have also developed alternative ways to copulate. In the case of the bed bug, males traumatically inseminate females, which allows faster passage of sperm to female sperm storage sites. The

neg: V-ATPase of insects, and certain tumor cells. Plasma membrane V-ATPases are involved in processes such as pH homeostasis, coupled transport, and tumor metastasis. V-ATPases in the acrosomal membrane of sperm acidify the acrosome. This acidification activates proteases required to drill through the plasma membrane of the egg. V-ATPases in the osteoclast plasma membrane pump protons onto the bone surface, which is necessary for bone resorption. In the intercalated cells of the kidney, V-ATPases pump protons into the urine, allowing for bicarbonate reabsorption into the blood. The yeast V-ATPase is the best characterized. There are at least 13 subunits identified to form

neg: Pervaporation membranes are fabricated by sol-gel chemical processes. Research into novel hydrophilic ceramic membranes has been focused on titania or zirconia. Very recently a break-through in hydrothermal stability has been achieved through the development of an organic-inorganic hybrid material. Pervaporation Pervaporation (or pervaporative separation) is a processing method for the separation of mixtures of liquids by partial vaporization through a non-porous or porous membrane. The term "pervaporation" is derived from the two steps of the process: (a) permeation through the membrane by the permeate, then (b) its evaporation into the vapor phase. This process is used by a number of industries

neg: Temnospondyli while males released sperm to fertilize them. Several fossils were described from the Early Permian of Texas in 1998 that may be egg masses of dissorophoid temnospondyls. They were the first known fossils of amphibian eggs. The fossils consist of small disks with thin membranes that are probably vitelline membranes and halo-like areas surrounding them that are most likely mucous coatings. They are attached to plant fossils, suggesting that these temnospondyls laid eggs on aquatic plants much like modern frogs. The mucous membranes show that the eggs were laid by amphibians, not fish (their eggs lack mucous), but the type

neg: Colletotrichum lindemuthianum acids from the living host cell to the fungus by use of monosaccharide-H+ symporters. About 48–72 hours after inoculation, depending on the environment, the biotrophic phase ends and the necrotrophic phase begins. It is marked by the development of many thin hyphae, known as secondary or necrotrophic hyphae, which develop off of the primary hyphae and the infection hypha. Unlike the much larger primary hyphae, these secondary hyphae move freely through the host in all directions, penetrating cell walls and membranes alike. In order to more easily ramify throughout the host tissue, the hyphae release enzymes which break down host-specific

neg: Acrosin binding protein Acrosin binding protein Acrosin binding protein is a protein that in humans is encoded by the ACRBP gene. The protein encoded by this gene is similar to proacrosin binding protein sp32 precursor found in mouse, guinea pig, and pig. This protein is located in the sperm acrosome and is thought to function as a binding protein to proacrosin for packaging and condensation of the acrosin zymogen in the acrosomal matrix. This protein is a member of the cancer/testis family of antigens and it is found to be immunogenic. In normal tissues, this mRNA is expressed only in testis, whereas it

neg: Sperm competition breaks off or tears off at the end of copulation and remains within the female to serve as a copulatory plug. This broken genitalia is believed to be an evolutionary response to sperm competition. This damage to the male genitalia means that these males can only mate once. Female factors can influence the result of sperm competition through a process known as "sperm choice". Proteins present in the female reproductive tract or on the surface of the ovum may influence which sperm succeeds in fertilizing the egg. During sperm choice females are able to discriminate and differentially use the sperm

neg: Sperm washing would do the procedure, such as Italy. Today, hundreds of babies have been born through this process. Sperm washing Sperm washing is the process in which individual sperms are separated from the semen. Washed sperm is used in artificial insemination using the intrauterine insemination (IUI) technique and in in vitro fertilization (IVF). It may also be used to decrease the risk of HIV transmission by an HIV-positive male, in which case the washed sperm is injected into a female using an artificial insemination technique. Sperm washing involves removing any mucus and non-motile sperm in the semen to improve the chances

neg: Sperm guidance successful pregnancies. Chemotaxis and thermotaxis can also be exploited possibly as a diagnostic tool to assess sperm quality. In addition, these processes can potentially be used, in the long run, as a means of contraception by interfering with the normal process of fertilization. Sperm guidance Sperm guidance is the process by which sperm cells (spermatozoa) are directed to the oocyte (egg) for the aim of fertilization. In the case of marine invertebrates the guidance is done by chemotaxis. In the case of mammals, it appears to be done by chemotaxis, thermotaxis and rheotaxis. Since the discovery of sperm attraction to

neg: Pinophyta Some pollen grains will land on a female cone for pollination. The generative cell in the pollen grain divides into two haploid sperm cells by mitosis leading to the development of the pollen tube. At fertilization, one of the sperm cells unites its haploid nucleus with the haploid nucleus of an egg cell. The female cone develops two ovule, each of which contains haploid haploid megaspores. A megasporocyte is divided by meiosis in each ovule. Each winged pollen grain is a four celled male gametophyte Three of the four cells break down leaving only a single surviving cell which will

neg: Unconventional oil recover energy from existing sources of waste such as petroleum coke as well as pre-existing waste deposits. This process, which imitates those that occur in nature, uses heat and pressure to break down organic and inorganic compounds through a method known as hydrous pyrolysis. Because energy output varies greatly based on feedstock, it is difficult to estimate potential energy production. According to Changing World Technologies, Inc., this process even has the ability to break down several types of materials, many of which are poisonous to both humans and the environment. Using synthetic fuel processes, the conversion of coal and natural

neg: Synthetic membrane and physical properties of synthetic membranes and separated particles as well as a choice of driving force define a particular membrane separation process. The most commonly used driving forces of a membrane process in industry are pressure and concentration gradients. The respective membrane process is therefore known as filtration. Synthetic membranes utilized in a separation process can be of different geometry and of respective flow configuration. They can also be categorized based on their application and separation regime. The best known synthetic membrane separation processes include water purification, reverse osmosis, dehydrogenation of natural gas, removal of cell particles by microfiltration

neg: Unicorn (spider) called an embolus, through which sperm is released during mating. Female "U. catleyi" have been observed with broken-off embolus tips lodged in their genitalia. This has been hypothesized as a type of "sperm-plug" or copulatory plug, where, by breaking off a piece of his anatomy (a process known as genital mutilation or genital breakage), a male physically precludes other males from successfully mating with the female, one of many types of sperm competition in animals. An alternative to the sperm competition function is that genital mutilation might allow males to more rapidly escape and avoid being cannibalized after mating, although

neg: Prelabor rupture of membranes of fluid may be associated with the baby becoming easier to feel through the belly (due to the loss of the surrounding fluid), decreased uterine size, or meconium (fetal stool) seen in the fluid. The cause of prelabor rupture of membranes (PROM) is not clearly understood, but the following are risk factors that increase the chance of it occurring. In many cases, however, no risk factor is identified. Fetal membranes likely break because they become weak and fragile. This weakening is a normal process that typically happens at term as the body prepares for labor and delivery. However, this can

neg: Sertoli cell enlagre the cyst and produce a space for priliferating germ cells. Commonly accepted fact that Sertol cells are terminally differentiated in amniota was recently changed. After xenogeneic transplantation Sertoli cells were able to proliferate. Sertoli cell A Sertoli cell (a kind of sustentacular cell) is a "nurse" cell of the testicles that is part of a seminiferous tubule and helps in the process of spermatogenesis, the production of sperm. It is activated by follicle-stimulating hormone (FSH) secreted by the adenohypophysis, and has FSH receptor on its membranes. It is specifically located in the convoluted seminiferous tubules (since this is the

neg: Diffuser (sewage) on EPDM membranes. This provides a buffer between the EPDM substrate and wastewater, hence reducing the likelihood of chemical attack and oxidation, and also providing better resistance to biological fouling and calcium scaling (manufacturers claim). Diffuser (sewage) An air diffuser or membrane diffuser is an aeration device typically in the shape of a disc, tube or plate, which is used to transfer air and with that oxygen into sewage or industrial wastewater. Oxygen is required by microorganisms/bacteria residents in the water to break down the pollutants. Diffusers use either rubber membranes or ceramic elements typically and produce either fine or