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Male Gametes (male + gamete)
Selected AbstractsEffect of Alcohol Consumption on CpG Methylation in the Differentially Methylated Regions of H19 and IG-DMR in Male Gametes,Implications for Fetal Alcohol Spectrum DisordersALCOHOLISM, Issue 9 2009Lillian A. Ouko Background:, Exposure to alcohol in utero is the main attributable cause of fetal alcohol spectrum disorders (FASD) which in its most severe form is characterized by irreversible behavioral and cognitive disability. Paternal preconception drinking is not considered to be a significant risk factor, even though animal studies have demonstrated that chronic paternal alcohol consumption has a detrimental effect on the physical and mental development of offspring even in the absence of in utero alcohol exposure. It has been documented that alcohol can reduce the levels and activity of DNA methyltransferases resulting in DNA hypomethylation and that reduced methyltransferase activity can cause activation of normally silenced genes. The aim of this study was to establish a link between alcohol use in men and hypomethylation of paternally imprinted loci in sperm DNA in genomic regions critical for embryonic development, thus providing a mechanism for paternal effects in the aetiology of FASD. Methods:, Sperm DNA from male volunteers was bisulfite treated and the methylation patterns of 2 differentially methylated regions (DMRs), H19 and IG-DMR, analyzed following sequencing of individual clones. The methylation patterns were correlated with the alcohol consumption levels of the volunteer males. Results:, There was a pattern of increased demethylation with alcohol consumption at the 2 imprinted loci with a significant difference observed at the IG-DMR between the nondrinking and heavy alcohol consuming groups. Greater inter-individual variation in average methylation was observed at the H19 DMR and individual clones were more extensively demethylated than those of the IG-DMR. CpG site #4 in the IG-DMR was preferentially demethylated among all individuals and along with the H19 DMR CpG site #7 located within the CTCF binding site 6 showed significant demethylation in the alcohol consuming groups compared with the control group. Conclusion:, This study demonstrates a correlation between chronic alcohol use and demethylation of normally hypermethylated imprinted regions in sperm DNA. We hypothesize that, should these epigenetic changes in imprinted genes be transmitted through fertilization, they would alter the critical gene expression dosages required for normal prenatal development resulting in offspring with features of FASD. [source] The zona pellucida of the koala (Phascolarctos cinereus): its morphogenesis and thicknessJOURNAL OF ANATOMY, Issue 3 2006Jamie A. Chapman Abstract In this study the ultrastructural organization of the koala oocyte and the thickness of the surrounding extracellular coat, the zona pellucida, has been determined to ascertain whether there is coevolution of the morphology of the female gamete with that of the highly divergent male gamete that is found in this marsupial species. Ovaries from several adult koalas were obtained and prepared for transmission electron microscopy. Oocytes in large tertiary follicles were somewhat smaller than those of most other marsupials, although their ultrastructural organization appeared similar and included many yolk vesicles. The zona pellucida surrounding the oocytes in tertiary follicles was approximately 8 µm thick and thus is of similar thickness to that of some eutherian mammals but at least twice as thick as that of most marsupial species so far studied. The results indicate that the koala oocyte is unusually small for a marsupial species whereas the zona pellucida is, by contrast, much thicker. How this relates to sperm,egg interaction at the time of fertilization has yet to be determined. [source] Widespread hermaphroditism in freshwater gastrotrichsINVERTEBRATE BIOLOGY, Issue 4 2001Mitchell J. Weiss Abstract. Freshwater members of the phylum Gastrotricha were long thought to lack male gametes and to exist exclusively as parthenogenetic females. The surprising 1978 discovery of sperm in the common species Lepidodermella squamata raised the question of how many other freshwater gastrotrichs might likewise be hermaphroditic. In a comparative study of species from across both major families, sperm have been found in every species examined intensively. They were detected in 19 species of Chaetonotidae (from Aspidiophorus, Chaetonotus, Heterolepidoderma, Ichthydium, Lepidodermella, and Polymerurus) and 3 species of Dasydytidae (from Haltidytes, Setopus, and Stylochaeta), characteristically occurring ventrally in single unilateral or (more often) 2,12 bilateral packets. Their shape ranges from filiform (length in Chaetonotus bisacer, ,40 ,m) to rodlike, spindlelike, oval, and possibly spherical (some in Stylochaeta scirtetica measure only 1 ,m). With light microscopy, a dense nucleus appears to fill the entire volume of these aflagellate cells. Spermatogenesis within cysts (maximally, 16 sperm/clone) is evidently characteristic of both families, each cyst generating one large residual body. Sperm-bearers display oocytes with sometimes distinctive cytoplasmic elements and a posterior X-organ whose organization can be complex. Evidence supports an unusual life cycle in which parthenogenesis is followed by simultaneous hermaphroditism. These findings may illuminate the reproductive characters as well as ancestry of marine and brackish-water taxa of Chaetonotida. [source] Disruption of a Plasmodium falciparum cyclic nucleotide phosphodiesterase gene causes aberrant gametogenesisMOLECULAR MICROBIOLOGY, Issue 1 2008Cathy J. Taylor Summary Phosphodiesterase (PDE) and guanylyl cyclase (GC) enzymes are key components of the cGMP signalling pathway and are encoded in the genome of Plasmodium falciparum. Here we investigate the role of specific GC and PDE isoforms in gamete formation , a process that is essential for malaria transmission and occurs in the Anopheles mosquito midgut following feeding on an infected individual. Details of the intracellular signalling events controlling development of the male and female gametes from their precursors (gametocytes) remain sparse in P. falciparum. Previous work involving the addition of pharmacological agents to gametocytes implicated cGMP in exflagellation , the emergence of highly motile, flagellated male gametes from the host red blood cell. In this study we show that decreased GC activity in parasites having undergone disruption of the PfGC, gene had no significant effect on gametogenesis. By contrast, decreased cGMP-PDE activity during gametocyte development owing to disruption of the PfPDE, gene, led to a severely reduced ability to undergo gametogenesis. This suggests that the concentration of cGMP must be maintained below a threshold in the developing gametocyte to allow subsequent differentiation to proceed normally. The data indicate that PfPDE, plays a crucial role in regulating cGMP levels during sexual development. [source] Novel features of Equisetum arvense spermatozoids: insights into pteridophyte evolutionNEW PHYTOLOGIST, Issue 1 2002K. S. Renzaglia Summary ,,To characterize structural diversity within Equisetum and among pteridophytes, architectural features of the sperm cell are described here in a second subgenus of Equisetum, a divergent basal group in the fern clade. ,,Transmission electron microscopy observations of prereleased spermatozoids of Equisetum arvense were correlated with three-dimensional scanning electron microscopy images of swimming cells. ,,The mature spermatozoid completes a helix of approximately 2.5 revolutions. At the cell anterior is a complex multilayered locomotory apparatus with staggered flagella. Mitochondria (elongated,rounded) are aggregated near the locomotory apparatus and organelles extend along the cell length. The spline contains up to 300 microtubules and wraps in part around the long cylindrical nucleus. In swimming sperm cells, the anterior of the cell remains tightly coiled while the posterior relaxes and extends in a trailing fashion. ,,Spermatozoids of Equisetum arvense are smaller than those of Equisetum hyemale but structurally similar, except for nuclear shape. Conservation of cellular features suggests recent radiation of the genus. Equisetum spermatozoids share several critical features with ferns, including Psilotum, and support monophyly of a fern,Equisetum assemblage. Entry of the male gametes of Equisetum in their entirety into the archegonial venters indicates possible biparental inheritance of chloroplast and mitochondrial genomes. [source] Characterization of the methylation status of five imprinted genes in sheep gametesANIMAL GENETICS, Issue 6 2009A. Colosimo Summary Genomic imprinting is a mammalian developmental process that uses epigenetic mechanisms to induce monoallelic and parental-specific expression of particular autosomal genes. A crucial epigenetic event consists of DNA methylation of CpG-islands, which become differentially methylated regions (DMRs) on the maternal and paternal alleles during oogenesis or spermatogenesis (germline DMRs). By contrast, somatic DMRs are acquired after fertilization. While there are several studies referring to methylation acquisition within germline DMRs in the mouse and human, a comparable methylation analysis of orthologous sequences is still lacking in sheep. To identify germline DMRs, this study analysed the methylation status of the available CpG-islands of five ovine imprinted genes (H19, IGF2R, DLK1, DIO3 and BEGAIN) in mature spermatozoa and in female gametes at different stages of their follicle growth, including in vitro matured oocytes. The 5,-end CpG-island of H19 showed a full methylation in spermatozoa and an absent methylation in growing and fully grown oocytes. The intron 2 CpG-island of IGF2R was unmethylated in male gametes, while it showed a high level of methylation in early stages of oogenesis. The promoter CpG-islands of DLK1 and DIO3 were found to be unmethylated both in spermatozoa and oocytes. Finally, the exon 9 CpG-island of BEGAIN was hypermethylated in mature male gametes, while it showed an almost complete methylation only in late stages of oocyte development. Our findings suggest that DNA methylation establishment during early stages of sheep oogenesis and subsequent in vitro maturation is gene-specific and that, of the five genes investigated, only the CpG-islands of H19 and IGF2R might represent ovine germline DMRs. [source] Effects of tributyltin(IV) chloride on fertilization of Styela plicata (Ascidiacea: Tunicata): II.APPLIED ORGANOMETALLIC CHEMISTRY, Issue 8 2003Scanning, transmission electron microscopy studies Abstract The morphological aspects of Styela plicata fertilization after treatment with tributyltin(IV) chloride are described by means of scanning and transmission electron microscopy investigations. Alterations have been shown both on female and male gametes; spermatozoa, all the egg envelopes and the mitochondria of the egg cortical cytoplasm are modified in relation to incubation time. As a consequence, the damage to gametes blocks sperm,egg interaction and fertilization does not occur. Copyright © 2003 John Wiley & Sons, Ltd. [source] | ||||||||||