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Spermatogonial Stem Cells
A spermatogonial stem cell (SSC), also known as a type A spermatogonium, is a spermatogonium that does not differentiate into a spermatocyte, a precursor of sperm cells. Instead, they continue dividing into other spermatogonia or remain dormant to maintain a reserve of spermatogonia. Type B spermatogonia, on the other hand, differentiate into spermatocytes, which in turn undergo meiosis to eventually form mature sperm cells. Spermatogonial stem cells in the testis During foetal development, gonocytes develop from primordial germ cells and following this SSCs develop from gonocytes in the testis. SSCs are the early precursor for spermatozoa and are responsible for the continuation of spermatogenesis in adult mammals. The stem cells are capable of dividing into more SSCs which is vital for maintaining the stem cell pool. Alternatively, they go on to differentiate into spermatocytes, spermatids and finally spermatozoa. One SSC is the precursor for multiple spermatozoa and there ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spermatocytogenesis
Spermatocytogenesis is the male form of gametocytogenesis and involves stem cells dividing to replace themselves and to produce a population of cells destined to become mature sperm. The stem cells involved are called spermatogonia and are a specific type of stem cell known as gametogonia. Three functionally separate spermatogonial cell types are recognised on the basis of the appearance of the nuclei: ''type A dark spermatogonia'' (Ad), ''type A pale spermatogonia'' (Ap), and ''type B spermatogonia'' (B). Type Ad spermatogonia ("dark") The population of spermatogonia is maintained by ''type Ad spermatogonia''. These cells do not directly participate in producing sperm, instead serving to maintain the supply of stem cells for spermatogenesis. Each type Ad spermatogonium divides to produce another type Ad spermatogonium, which can further carry on spermatogenesis, and one ''type Ap spermatogonium'', which differentiates further. Type Ap spermatogonia ("pale") ''Type Ap sper ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sertoli Cell
Sertoli cells are a type of sustentacular "nurse" cell found in human testes which contribute to the process of spermatogenesis (the production of sperm) as a structural component of the seminiferous tubules. They are activated by follicle-stimulating hormone (FSH) secreted by the adenohypophysis and express FSH receptor on their membranes. History Sertoli cells are named after Enrico Sertoli, an Italian physiologist who discovered them while studying medicine at the University of Pavia, Italy. He published a description of his eponymous cell in 1865. The cell was discovered by Sertoli with a Belthle microscope which had been purchased in 1862. In the 1865 publication, his first description used the terms "tree-like cell" or "stringy cell"; most importantly, he referred to these as "mother cells". Other scientists later used Enrico's family name to label these cells in publications, beginning in 1888. As of 2006, two textbooks that are devoted specifically to the Sertoli cell have ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkylation
Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effecting alkylation. Alkyl groups can also be removed in a process known as dealkylation. Alkylating agents are often classified according to their nucleophilic or electrophilic character. In oil refining contexts, alkylation refers to a particular alkylation of isobutane with olefins. For upgrading of petroleum, alkylation produces a premium blending stock for gasoline. In medicine, alkylation of DNA is used in chemotherapy to damage the DNA of cancer cells. Alkylation is accomplished with the class of drugs called alkylating antineoplastic agents. Nucleophilic alkylating agents Nucleophilic alkylating agents deliver the equivalent of an alkyl anion ( carbanion). The formal "alkyl anion" attacks an electrophile, forming a new covalent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flow Cytometry
Flow cytometry (FC) is a technique used to detect and measure physical and chemical characteristics of a population of cells or particles. In this process, a sample containing cells or particles is suspended in a fluid and injected into the flow cytometer instrument. The sample is focused to ideally flow one cell at a time through a laser beam, where the light scattered is characteristic to the cells and their components. Cells are often labeled with fluorescent markers so light is absorbed and then emitted in a band of wavelengths. Tens of thousands of cells can be quickly examined and the data gathered are processed by a computer. Flow cytometry is routinely used in basic research, clinical practice, and clinical trials. Uses for flow cytometry include: * Cell counting * Cell sorting * Determining cell characteristics and function * Detecting microorganisms * Biomarker detection * Protein engineering detection * Diagnosis of health disorders such as blood cancers * Measuring ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
In Vitro Spermatogenesis
In vitro spermatogenesis is the process of creating male gametes (spermatozoa) outside of the body in a culture system. The process could be useful for fertility preservation, infertility treatment and may further develop the understanding of spermatogenesis at the cellular and molecular level. Spermatogenesis is a highly complex process and artificially rebuilding it ''in vitro'' is challenging. These include creating a similar microenvironment to that of the testis as well as supporting endocrine and paracrine signalling, and ensuring survival of the somatic and germ cells from spermatogonial stem cells (SSCs) to mature spermatozoa. Different methods of culturing can be used in the process such as isolated cell cultures, fragment cultures and 3D cultures Culture techniques Isolated cell cultures Cell cultures can include either monocultures, where one cell population is cultured, or co-culturing systems, where several cell lines (must be at least two) can be cultured t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Repair
DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA damage, resulting in tens of thousands of individual molecular lesions per cell per day. Many of these lesions cause structural damage to the DNA molecule and can alter or eliminate the cell's ability to transcribe the gene that the affected DNA encodes. Other lesions induce potentially harmful mutations in the cell's genome, which affect the survival of its daughter cells after it undergoes mitosis. As a consequence, the DNA repair process is constantly active as it responds to damage in the DNA structure. When normal repair processes fail, and when cellular apoptosis does not occur, irreparable DNA damage may occur, including double-strand breaks and DNA crosslinkages (interstrand crosslinks or ICLs). This can eventually lead to malignant ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aging
Ageing ( BE) or aging ( AE) is the process of becoming older. The term refers mainly to humans, many other animals, and fungi, whereas for example, bacteria, perennial plants and some simple animals are potentially biologically immortal. In a broader sense, ageing can refer to single cells within an organism which have ceased dividing, or to the population of a species. In humans, ageing represents the accumulation of changes in a human being over time and can encompass physical, psychological, and social changes. Reaction time, for example, may slow with age, while memories and general knowledge typically increase. Ageing increases the risk of human diseases such as cancer, Alzheimer's disease, diabetes, cardiovascular disease, stroke and many more. Of the roughly 150,000 people who die each day across the globe, about two-thirds die from age-related causes. Current ageing theories are assigned to the damage concept, whereby the accumulation of damage (such as DNA ox ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Damage (naturally Occurring)
DNA damage is an alteration in the chemical structure of DNA, such as a break in a strand of DNA, a nucleobase missing from the backbone of DNA, or a chemically changed base such as 8-OHdG. DNA damage can occur naturally or via environmental factors, but is distinctly different from mutation, although both are types of error in DNA. DNA damage is an abnormal chemical structure in DNA, while a mutation is a change in the sequence of base pairs. DNA damages cause changes in the structure of the genetic material and prevents the replication mechanism from functioning and performing properly. The DNA damage response (DDR) is a complex signal transduction pathway which recognizes when DNA is damaged and initiates the cellular response to the damage. DNA damage and mutation have different biological consequences. While most DNA damages can undergo DNA repair, such repair is not 100% efficient. Un-repaired DNA damages accumulate in non-replicating cells, such as cells in the brains o ... [...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 that ag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retinoic Acid
Retinoic acid (used simplified here for all-''trans''-retinoic acid) is a metabolite of vitamin A1 (all-''trans''-retinol) that mediates the functions of vitamin A1 required for growth and development. All-''trans''-retinoic acid is required in chordate animals, which includes all higher animals from fish to humans. During early embryonic development, all-''trans''-retinoic acid generated in a specific region of the embryo helps determine position along the embryonic anterior/posterior axis by serving as an intercellular signaling molecule that guides development of the posterior portion of the embryo. It acts through Hox genes, which ultimately control anterior/posterior patterning in early developmental stages. All-''trans''-retinoic acid (ATRA) is the major occurring retinoic acid, while isomers like 13-''cis''- and 9-''cis''-retinoic acid are also present in much lower levels. The key role of all-''trans''-retinoic acid in embryonic development mediates the high teratogenici ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meiosis
Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately result in four cells with only one copy of each chromosome ( haploid). Additionally, prior to the division, genetic material from the paternal and maternal copies of each chromosome is crossed over, creating new combinations of code on each chromosome. Later on, during fertilisation, the haploid cells produced by meiosis from a male and female will fuse to create a cell with two copies of each chromosome again, the zygote. Errors in meiosis resulting in aneuploidy (an abnormal number of chromosomes) are the leading known cause of miscarriage and the most frequent genetic cause of developmental disabilities. In meiosis, DNA replication is followed by two rounds of cell division to produce four daughter cells, each with half the number of chr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peritubular Myoid Cells
A peritubular myoid (PTM) cell is one of the smooth muscle cells which surround the seminiferous tubules in the testis. These cells are present in all mammals but their organization and abundance varies between species. The exact role of PTM cells is still somewhat uncertain and further work into this is needed. However, a number of functions of these cells have been established. They are contractile cells which contain actin filaments and are primarily involved in transport of spermatozoa through the tubules. They provide structural integrity to the tubules through their involvement in laying down the basement membrane. This has also been shown to affect Sertoli cell function and PTM cells also communicate with Sertoli cells through the secretion of growth factors and ECM (extra-cellular matrix) components. Studies have shown PTM cells to be critical in achieving normal spermatogenesis. Overall, PTM cells have a role in both maintaining the structure of the tubules and regulating ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
