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Acrosome
The acrosome is an organelle that develops over the anterior (front) 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. In placental mammals the acrosome contains degradative 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 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 fl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acrosome Reaction
During fertilization, a sperm must first fuse with the plasma membrane and then penetrate the female egg cell to fertilize it. Fusing to the egg cell usually causes little problem, whereas penetrating through the egg's hard shell or extracellular matrix can be more difficult. 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 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. Variation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Globozoospermia
Globozoospermia 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 is characterised by round-headed spermatozoa without acrosomes, 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 is unclear whether these two forms are variations on the same syndrome, or actually different syndromes. Infertility in this condition results from the sperm heads missing their acrosome. These sperm, therefore, have a characteristic round or spherically shaped head. Given the absence of the acrosome, these sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acrosin
Acrosin is a digestive enzyme that acts as a protease. In humans, acrosin is encoded by the ''ACR'' gene. Acrosin is released from the acrosome of spermatozoa as a consequence of the acrosome reaction. It aids in the penetration of the Zona Pellucida. Enzyme Mechanism Acrosin is a typical serine proteinase with trypsin-like specificity. The reaction proceeds according to the usual serine protease mechanism. First, His-57 deprotonates Ser-195, allowing it to serve as a nucleophile. Deprotonated Ser-195 then reacts with the carbonyl carbon of a peptide, forming a tetrahedral intermediate. The tetrahedral intermediate then collapses, resulting in an H2N-R1 leaving group, which is protonated through His-57. Finally, His-57 deprotonates a water molecule, which can then serve as a nucleophile by similarly reacting with the carbonyl carbon. Collapse of the tetrahedral intermediate then results in a Ser-195 leaving group, which is protonated through His-57, resulting in all residues re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spermatozoon
A spermatozoon (; also spelled spermatozoön; ; ) is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote. (A zygote is a single cell, with a complete set of chromosomes, that normally develops into an embryo.) Sperm cells contribute approximately half of the nuclear genetic information to the diploid offspring (excluding, in most cases, mitochondrial DNA). In mammals, the sex of the offspring is determined by the sperm cell: a spermatozoon bearing an X chromosome will lead to a female (XX) offspring, while one bearing a Y chromosome will lead to a male (XY) offspring. Sperm cells were first observed in Antonie van Leeuwenhoek's laboratory in 1677. Mammalian spermatozoon structure, function, and size Humans The human sperm cell is the reproductive cell in males and will only survive in warm environments; once it leaves the male body the sperm's survival likelihood is reduced and it may die, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 Male infertility refers to a sexually mature male's inability to impregnate 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, .... The acroplaxome is a structure found between the acrosomal membrane and the nuclear membrane. The acroplaxome contains structural proteins including keratin 5, F-actin and profilin IV ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zona Pellucida
The zona pellucida (plural zonae pellucidae, also egg coat or pellucid zone) is a specialized extracellular matrix that surrounds the plasma membrane of mammalian oocytes. It is a vital constitutive part of the oocyte. The zona pellucida first appears in unilaminar primary oocytes. It is secreted by both the oocyte and the ovarian follicles. The zona pellucida is surrounded by the corona radiata. The corona is composed of cells that care for the egg when it is emitted from the ovary. This structure binds spermatozoa, and is required to initiate the acrosome reaction. In the mouse (the best characterised mammalian system), the zona glycoprotein, ZP3, is responsible for sperm binding, adhering to proteins on the sperm plasma membrane. 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 h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Male Infertility
Male infertility refers to a sexually mature male's inability to impregnate 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. More recently, advance sperm analyses that examine intracellular sperm components are being developed. Age considerations There is a decrease in sperm concentration as men age: 90% of seminiferous tubules in men in their 20s and 30s contain spermatids, whereas men in their 40s and 50s have spermatids in 50% of their seminiferous tubules, and only 10% of seminiferous tubules from men aged > 80 years contain spermatids. In a random international sample of 11,548 men confirmed to be biological fathers by DNA paternity testing, the oldest father was found to be 66 years old at the birth of his child; the ratio of DNA-confirmed versus DNA-rejected paternity tests around tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organelle
In cell biology, an organelle is a specialized subunit, usually within a cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as organs are to the body, hence ''organelle,'' the suffix ''-elle'' being a diminutive. Organelles are either separately enclosed within their own lipid bilayers (also called membrane-bound organelles) or are spatially distinct functional units without a surrounding lipid bilayer (non-membrane bound organelles). Although most organelles are functional units within cells, some function units that extend outside of cells are often termed organelles, such as cilia, the flagellum and archaellum, and the trichocyst. Organelles are identified by microscopy, and can also be purified by cell fractionation. There are many types of organelles, particularly in eukaryotic cells. They include structures that make up the endomembrane system (such as the nuclear envelope, endoplasmic reticulum, an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hyaluronidase
Hyaluronidases are a family of enzymes that catalyse the degradation of hyaluronic acid (HA). Karl Meyer classified these enzymes in 1971, into three distinct groups, a scheme based on the enzyme reaction products. The three main types of hyaluronidases are two classes of eukaryotic endoglycosidase hydrolases and a prokaryotic lyase-type of glycosidase. In humans, there are five functional hyaluronidases: HYAL1, HYAL2, HYAL3, HYAL4 and HYAL5 (also known as SPAM1 or PH-20); plus a pseudogene, HYAL6 (also known as HYALP1). The genes for HYAL1-3 are clustered in chromosome 3, while HYAL4-6 are clustered in chromosome 7. HYAL1 and HYAL2 are the major hyaluronidases in most tissues. GPI-anchored HYAL2 is responsible for cleaving high-molecular weight HA, which is mostly bound to the CD44 receptor. The resulting HA fragments of variable size are then further hydrolized by HYAL1 after being internalized into endo-lysosomes; this generates HA oligosaccharides. According to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ovum
The egg cell, or ovum (plural ova), is the female reproductive cell, or gamete, in most anisogamous organisms (organisms that reproduce sexually with a larger, female gamete and a smaller, male one). The term is used when the female gamete is not capable of movement (non- motile). If the male gamete ( sperm) is capable of movement, the type of sexual reproduction is also classified as oogamous. A nonmotile female gamete formed in the oogonium of some algae, fungi, oomycetes, or bryophytes is an oosphere. When fertilized the oosphere becomes the oospore. When egg and sperm fuse during fertilisation, a diploid cell (the zygote) is formed, which rapidly grows into a new organism. History While the non-mammalian animal egg was obvious, the doctrine ''ex ovo omne vivum'' ("every living nimal comes froman egg"), associated with William Harvey (1578–1657), was a rejection of spontaneous generation and preformationism as well as a bold assumption that mammals also reprodu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Germ Cell Structures
Germ or germs may refer to: Science * Germ (microorganism), an informal word for a pathogen * Germ cell, cell that gives rise to the gametes of an organism that reproduces sexually * Germ layer, a primary layer of cells that forms during embryonic development * Cereal germ, the reproductive part of a cereal grain * Tooth germ, an aggregation of cells that eventually forms a tooth * Germ theory of disease, which states that some diseases are caused by microorganisms * Germ (mathematics), an object in a topological space that captures local properties Art and media Music * Germs (band), an American punk rock band * Germ (musician), a stage name of Tim Wright * Germ (rapper), an American rapper affiliated with Suicideboys and Pouya * "Germs" (song), by "Weird Al" Yankovic * ''The Germ'' (album), by Victim's Family Others * "Germs" (''Invader Zim''), an episode of ''Invader Zim'' * ''The Germ'' (periodical), a British art magazine published in 1850 * The Germs (comics), ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Andrology
Andrology (from grc, ἀνήρ, ''anēr'', genitive , ''andros'', "man"; and , ''-logia'') is a name for the medical specialty that deals with male health, particularly relating to the problems of the male reproductive system and urological problems that are unique to men. It is the counterpart to gynaecology, which deals with medical issues which are specific to female health, especially reproductive and urologic health. Process Andrology covers anomalies in the connective tissues pertaining to the genitalia, as well as changes in the volume of cells, such as in genital hypertrophy or macrogenitosomia. From reproductive and urologic viewpoints, male-specific medical and surgical procedures include vasectomy, vasovasostomy (one of the vasectomy reversal procedures), orchidopexy and circumcision as well as intervention to deal with male genitourinary disorders such as the following: History Unlike gynaecology, which has a plethora of medical board certification programs wo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
