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Topic: Spermatogenesis

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	Spermatogenesis - Wikipedia, the free encyclopedia
		Spermatogenesis is the process by which stem cells develop into mature spermatozoon (sperm) cells.
		Spermatogenesis takes place inside a male’s testes, specifically in the walls of the seminiferous tubules.
		One daughter cell, known as a Type A spermatogonium, does not participate in spermatogenesis and is needed to ensure that stem cells never run out of supply, which are needed in large quantities since the average male produces trillions of sperm cells throughout his lifetime.
	en.wikipedia.org /wiki/Spermatogenesis (906 words)

	Definition of Spermatogenesis
		Spermatogenesis refers to the creation, or genesis, of sperm cells, which occurs in the male gonads or testes.
		The process of spermatogenesis is highly regulated via hormonal messengers and also the cell-cell comunication between the developing germ cells (sperm cells) and the nurse-like Sertoli cells.
		The Sertoli cell is essential for spermatogenesis as it provides support for the developing sperm cells - moving them towards the lumen of the semiferous tubule as they develop until maturity when they are released.
	www.wordiq.com /definition/Spermatogenesis (417 words)

	[No title]
		Spermatogenesis is the process of sperm cell development.
		Genes carried on the X chromosome that inhibit spermatogenesis are inactivated in XY somatic cells.
		Biochemical and biophysical facets of sperm-Sertoli interactions in spermatogenesis are largely unknown.
	www.uwyo.edu /wjm/repro/spermat.htm (1769 words)

	Indmedica - Obs & Gynaecology - Cyber Lectures (Site not responding. Last check: 2007-10-22)
		Spermatogenesis is a hormonally regulated process where germ cells differentiate into mature spermatozoa by passing through several stages of meiosis.
		Depending upon the state of spermatogenesis in a particular patient, a variety of cell types-including Sertoli cells, spermatogonia, primary spermatocytes, secondary spermatocytes, spermatocytes (early and late) and spermatozoa are encountered in the smears.
		Normal spermatogenesis this pattern is described when the smears show spermatogonia, primary spermatogonia, spermatids, many spermatozoa and a proportional number of Sertoli cells forming roughly one third of the total spermatogenetic cells.
	www.indmedica.com /cyberlectures.php?action=details&catid=10&clid=60 (1023 words)

	Microsurgical TESE and the distribution of spermatogenesis in non-obstructive azoospermia - Sherman J. Silber, M.D.
		The theoretical basis for attempting to retrieve spermatozoa for ICSI from the testes of men with apparent absence of spermatogenesis was based on early quantitative histological studies from testicle biopsy in fertile and infertile men (Zuckerman et al., 1978; Silber and Rodriguez-Rigau, 1981).
		Among 15 cases where multiple biopsies were performed for mapping of spermatogenesis, and among 43 cases where contiguous strips were removed (58 microsurgical TESE cases in toto; Table 1), there was a total of 28 cases of maturation arrest and 30 of Sertoli cell-only, as verified by histology.
		We now have direct evidence that if spermatogenesis is present in cases of non-obstructive azoospermia, it is distributed diffusely throughout the testis and is not limited to a specific region.
	www.infertile.com /inthenew/sci/teseopin.htm (4698 words)

	Spermatogenesis (Site not responding. Last check: 2007-10-22)
		The process of spermatogenesis is highly regulated hormonal messengers and also the cell-cell comunication the developing germ cells (sperm cells) and nurse-like Sertoli cells.
		The Sertoli cell is essential for spermatogenesis as it support for the developing sperm cells - them towards the lumen of the testicual as they develop until maturity when they released.
		The Establishment of Spermatogenesis in the Seminiferous Epithelium of the Pubertal Golden Hamster: (Mesocricetus Auratus) (Advances in Anatomy, Embryology, and Cell Biology, Vol 140)
	www.freeglossary.com /Spermatogenesis (369 words)

	Spermatogenesis and Spermiogenesis in Didymocystis wedli Ariola
		It was observed that the different cells of the spermatogenesis process follow the classic pattern reported for the majority of the parasitic platyhelminthes.
		Indeed spermatogenesis of Digenea has been the subject of several studies in recently published papers, although these dealt with only a few of the existing species, such as Mesocoelium monas by Iomini et al.
		The present study deals with the processes of spermatogenesis, spermiogenesis and the spermatozoon in a species of the family Didymozoidae, Didymocystis wedli Ariola, 1902, a parasite of Thunnus albacares recovered from the coast of the State of Rio de Janeiro, Brazil.
	memorias.ioc.fiocruz.br /968/4220.html (337 words)

	Developmental Biology Online: Gene Expression During Sperm Development
		RNA-binding proteins are critical in spermatogenesis, because many of the genes expressed in the sperm are regulated at the level of translation (Schäfer et al.
		The synthesis of protamine, the basic protein that replaces histones in the haploid sperm nucleus, is regulated by the phosphorylation of an 18-kDa binding protein that recognizes the 3′ untranslated region of the mouse protamine message (Kwon and Hecht 1993).
		This isoform of β-tubulin is seen only during spermatogenesis, and it is responsible for forming the meiotic spindles, the axoneme, and the microtubules associated with the lengthening mitochondria.
	www.devbio.com /article.php?ch=19&id=193 (1637 words)

	ROLE OF CYCLIC AMP-RESPONSE ELEMENT MODULATOR
		Spermatogenesis is an active process which continues during the lifetime of male individuals.
		In some cases of male infertility, the spermatogenesis is distrubed and is associated with apoptosis, and abnormal morphologic configurations in sperm.
		Although some vaiability was observed in the serum concentration of testosterone and the amount of testicular androgens, the serum concentration of the FSH in the mice with the knocked-out gene was not significantly different from those found in the normal control mice.
	www.bioscience.org /news/scientis/reprod.htm (620 words)

	Dietary phytoestrogens affect Testis (Site not responding. Last check: 2007-10-22)
		Estrogen is synthesized in the testis, both in Leydig cells and seminiferous epithelium, and its importance in spermatogenesis is highlighted by the phenotype of the aromatase knockout (ArKO) mouse.
		We hypothesized that maintenance of spermatogenesis in younger animals may be mediated by exogenous estrogenic substances.
		The impairment of spermatogenesis seen in soy-free ArKOs occurred in the absence of a decreased gonadotropic stimulus, suggesting that the effects of dietary phytoestrogens are independent of changes to the pituitary-gonadal axis.
	www.hairlosstalk.com /discussions/posts/56584.html (234 words)

	Research Summaries - Sharpe et al.
		The organization of the stages of spermatogenesis in human males is different from that of species with highly efficient spermatogenesis.
		The poor efficiency ('efficiency' referring to the number of germ cells that each Sertoli cell supports) of spermatogenesis in the human male may make him more susceptible than other species to the adverse effects of environmental factors.
		A study conducted in Denmark compared the sperm count in two groups of nearly 200 young men, one group from a rural and one from an urban population.
	www.emcom.ca /summaries/sharpe.shtml (1263 words)

	International Society of Andrology (Site not responding. Last check: 2007-10-22)
		Marvin L. Meistrich (USA) showed that recovery of spermatogenesis after irradiation in rats could be stimulated by hormone treatment not only during irradiation but also when T or GnRH treatment were initiated at different intervals after cessation of irradiation.
		The very interesting point was that recovery of spermatogenesis was more effective in those animals where intratesticular T was critically reduced by the treatments with T or GnRH agonist.
		The use of the last technique in mice indicated that FSH might not be essential for the initiation and completion of the initial wave of spermatogenesis and for the maintenance of spermatogenesis in the special strain of mice.
	www.andrology.org /Members/janos/spermatology/1998120104/view (1774 words)

	Revista do Hospital das Clínicas - Finasteride-associated male infertility (Site not responding. Last check: 2007-10-22)
		We hypothesize that finasteride may not dramatically change the spermatogenesis process in healthy men, but in patients with conditions related to infertility, an amplification of the negative influence of finasteride could occur.
		The aim of this study was describe 3 cases of young male patients who consulted for infertility and showed severe decrease of spermatogenesis during finasteride treatment (1 mg/day).
		Kinniburg D, Anderson RA, Baird D. Suppression of spermatogenesis with desogestrel and testosterone pellets is not enhanced by addition of finasteride.
	www.scielo.br /scielo.php?pid=S0041-87812004000400009&script=sci_arttext&tlng=en (1525 words)

	Characterisation of two novel genes required for spermatogenesis in Drosophila.
		All stages of spermatogenesis are seen as a temporal progression from young spermatogonia at the apical tip (top left), through primary spermatocytes (large cells on left hand side), to maturing sperm (long threads along lumen).
		In Drosophila spermatogenesis progression through the meiotic cell cycle is co-ordinated with the onset of spermatid differentiation.
		Transcriptional activation in Drosophila spermatogenesis involves the mutually dependent function of aly and a novel meiotic arrest gene cookie monster.
	users.ox.ac.uk /~zool0195 (866 words)

	Stephen DiNardo, Ph.D. (Site not responding. Last check: 2007-10-22)
		In initiating spermatogenesis, stem cells of the male germline choose between self-renewal and lineage progression.
		The DiNardo lab pioneered the use of Drosophila spermatogenesis as a model stem cell system, and we are now collaborating with the Brinster lab, which focuses on mammalian (mouse) germline spermatogonial stem cell (GSC) function.
		Spermatogenesis is quite similar comparing mouse and fruitfly, with both maintained by GSC populations and special somatic cells that comprise the stem cell’s “niche”.
	www.med.upenn.edu /crrwh/DiNardo.html (581 words)

	Comparative effects of neonatal exposure of male rats to potent and weak (environmental) estrogens on spermatogenesis ...
		This study investigated whether neonatal exposure of male rats to estrogenic compounds altered pubertal spermatogenesis (days 18 and 25) and whether the changes observed resulted in long-term changes in testis size, mating, or fertility (days 90-100).
		Compared with (soy-fed) controls, DES administration caused dose-dependent retardation of pubertal spermatogenesis on day 18, as evidenced by decreases in testis weight, lumen formation, and spermatocyte nuclear volume per unit Sertoli cell and elevation of the germ cell apoptotic index.
		By day 25, although the changes in FSH levels largely persisted, all of the stimulatory effects on spermatogenesis seen on day 18 in the various treatment groups were no longer evident.
	www.arclab.org /medlineupdates/abstract_11014247.html (570 words)

	Reproductive Biology and Endocrinology \| Abstract \| Understanding spermatogenesis is a prerequisite for treatment
		Throughout spermatogenesis multiplication, maturation and differentiation of germ cells results in the formation of the male gamete.
		The understanding of spermatogenesis needs detailed informations about the organization of the germinal epithelium, the structure and function of different types of germ cells, endocrine and paracrine cells and mechanisms, intratesticular and extratesticular regulation of spermatogenesis.
		The profound knowledge of the complicate process of spermatogenesis and all cells or cell systems involved with is the prerequisite to develop concepts for therapy of male infertility or to handle germ cells in the management of assisted reproduction.
	www.rbej.com /content/1/1/107/abstract (141 words)

	Spermatogenesis
		"Spermatogenesis" is generally used as a noun (singular) -- approximately 100.00% of the time.
		"Spermatogenesis" is used about 6 times out of a sample of 100 million words spoken or written in English.
		"Spermatogenesis" is suggested in spellcheckers for the following: spermatogensis, spermatongenesis.
	www.websters-online-dictionary.org /definition/english/Sp/Spermatogenesis.html (358 words)

	"MICROSURGICAL (TESE) TESTICULAR SPERM EXTRACTION FOR AZOOSPERMIC MEN: Abstract of Presentation for Meeting of the ...
		We wished to examine the quantitative presence of spermatogenesis in different regions of the testis in azoospermic men, in order to develop a rational microsurgical strategy for the TESE procedure.
		This suggested that a certain threshold of quantitative spermatogenesis was required in order for some sperm to "spill over" into the ejaculate.
		However, in cases where the distribution of sperm is sparsely diffused, a microsurgical approach is required in order to either locate tubules with spermatogenesis and remove minimal tissue, or to minimize pain and tissue loss when greater amounts of tissue must be removed in order to find sperm.
	www.infertile.com /inthenew/sci/teseabst.htm (701 words)

	BioCarta - Charting Pathways of Life
		The transcriptional regulator CREM plays a key role in spermatogenesis, acting as a central transcription factor triggering a cascade of transcriptional activation of post-meiotic genes involved in this process such as calspermin and testis angiotensin-converting enzyme.
		The key role of CREM in sperm formation is demonstrated by the male sterility of mice lacking CREM, the failure of spermatids to develop into mature sperm, and a lack of post-meiotic gene expression in these animals.
		Although the regulation of transcription by a kinesin is surprising, a functional connection between cytoskeletal elements and transcriptional regulation is not unprecedented, as demonstrated by the transcription factor MIZ-1 that regulates transcription in response to changes in microtubule structure.
	www.biocarta.com /pathfiles/m_cremPathway.asp (471 words)

	CAMB: Faculty: Ina Dobrinski
		In order to have a model system for the study and manipulation of spermatogenesis that is applicable to a variety of mammalian species including primates, we have recently developed the technique of testis tissue xenografting into mouse hosts.
		This strategy holds great potential not only as a basic science tool for the study of spermatogenesis in different species, but also for preservation of male genetics from immature individuals like endangered animals, valuable laboratory strains or farm animals, and potentially even human childhood cancer patients.
		Germ cell transplantation and testis tissue xenografting are novel, exiting research areas with tremendous potential both for basic research into male germ line stem cell biology and spermatogenesis, as well as applications for animal transgenesis and genetic preservation.
	www.med.upenn.edu /camb/faculty/cbp/dobrinski.html (651 words)

	Hospital for Sick Children Research Institute - Brill Lab - spermatogenesis
		Because much of spermatogenesis is conserved across species, what we learn will have implications for understanding human male infertility and may also lead to the design of novel therapeutic approaches for birth control.
		A germ line stem cell undergoes asymmetric division to yield a new stem cell and a founder gonial blast.
		The different stages of spermatogenesis are present in rough temporal order in the adult Drosophila testis.
	www.sickkids.ca /brilllab/custom/spermatogenesis.asp (241 words)

	Spermatogenesis
		Spermatogenesis is the process of producing sperm with half the number of chromosomes (hapliod) as somatic cells.
		Spermatogenesis occurs in medullary sex cords known as seminiferous tubules.
		This part of spermatogenesis is defined as the nuclear and cytoplasmic changes in the spermatid that results in the spermatozoa
	www.rci.rutgers.edu /~uzwiak/HumanSexuality/HSSpringLect3.html (638 words)

	The Society for Male Reproduction and Urology
		Previous studies suggest that appropriate GDNF expression in the testis is necessary for normal sperm survival, proliferation, and/or maturation; and, that accumulation of sperm precursors, resulting in germ cell tumors.
		We are pursuing several projects to establish the role of Ret signaling in the spermatogenesis.
		We are utilizing the technique of whole testicular tissue transplantation to study postnatal spermatogenesis of perinatal lethal mutant mice.
	www.smru.org /professionals/researchspotlight.html (542 words)

	Stage and developmental specific gene expression during mammalian spermatogenesis (Site not responding. Last check: 2007-10-22)
		ABSTRACT Spermatogenesis is a complex developmental process which involves amplification of germinal stem cells, their differentiation into spermatocytes, meiotic division and finally transformation into mature spermatozoa.
		Therefore, spermatogenesis provides an interesting system for examining the regulation of gene expression during development and differentiation.
		The genes expressed during spermatogenesis can be divided into two main groups: diploid and haploid expressed genes.
	www.ijdb.ehu.es /9601/a379.htm (133 words)

	CPEB proteins control two key steps in spermatogenesis in C. elegans -- Luitjens et al. 14 (20): 2596 -- Genes and ...
		functions in spermatogenesis and are dispensable for oogenesis.
		Barton, M.K. and Kimble, J. fog-1, a regulatory gene required for specification of spermatogenesis in the germ line of Caenorhabditis elegans.
		Huynh, J. and St Johnston, D. The role of BicD, Egl, Orb and the microtubules in the restriction of meiosis to the Drosophila oocyte.
	www.genesdev.org /cgi/content/full/14/20/2596 (7263 words)

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