Final Maturation Of Spermatozoa Research Articles

Spermatogenesis ofAmphisbaena silvestrii(Boulenger, 1902): First Report for Amphisbaenidae

Abstract Gametogenesis studies are important to understand ecological and evolutionary processes. We report the first detailed description of spermatogenesis in amphisbaenians and describe the morphology of the male germ cells of Amphisbaena silvestrii and the organization of the germinal epithelium. We sampled the testes of 25 specimens and cut 3-μm thick sections. We then stained these sections by using 1% toluidine blue and photo-documented them. Testes are covered by the tunica albuginea that sends septa between the seminiferous tubules. The interstitial tissue is highly vascularized and consists of loose connective tissue with Leydig cells. Seminiferous tubules are coiled and coated with juxtaposed myoid cells. Sertoli cells and sperm series present a digitiform or pyramidal organization. We observed eight stages of development of the spermatids and the final maturation of spermatozoa during spermiogenesis. Further, we noted significant variation in the nuclear diameters of germ cells. This trait cou...

Differential protein expression during sperm maturation and capacitation in an hermaphroditic bivalve,Pecten maximus(Linnaeus, 1758)

In order to investigate the mechanisms of final maturation and capacitation of spermatozoa in Pecten maximus, we used a 2D proteomic approach coupled with MALDI-TOF/TOF mass spectrometry (MS) and bioinformatics search against the Pecten database, to set up a reference map of the proteome of spawned spermatozoa, and identified 133 proteins on the basis of the EST database. These proteins are mainly involved in energy production, ion and electron transport (44%), cell movement (22%) and developmental processes (10%). Comparison between proteomes of spermatozoa collected before and after transit through the genital ducts of P. maximus led to the identification of differentially expressed proteins. Most of them are associated with energy metabolism (aconitate hydratase, malate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase), indicating important modifications of energy production during transit in gonoducts, potentially linked with acquisition of sperm motility. Three proteins involved in cell movement (Tektin-2, tubulin and microtubule-associated protein RP/EB family member 3) were down-regulated in spermatozoa stripped from the gonad. 40S ribosomal protein SA, involved in maturation of 40S ribosomal subunits, was also found to be down-regulated in spermatozoa obtained by induced spawning, suggesting reduction of the efficiency of RNA translation, a characteristic of late spermatozoon differentiation. These results confirm that maturation processes of P. maximus spermatozoa during transit through the gonoduct involve RNA translation, energy metabolism and structural proteins implicated in cell movement. Spermatozoa maturation processes clearly differ between P. maximus and gonochoric or alternately hermaphroditic bivalves, potentially in relation to reproductive strategies: the final maturation of the spermatozoon along the genital tract probably contributes to reduction of autofertilization in this simultaneously hermaphroditic species.

Aromatase, oestrogens and human male reproduction.

In most mammalian species aromatase is encoded by a single gene (Cyp19), which contains 18 exons, nine of them being translated. In man, the presence of a biologically active aromatase and oestrogen receptors (ERalpha and ERbeta) has been reported in Leydig cells, and also in immature germ cells and ejaculated spermatozoa. Concerning aromatase, the amount of transcript and enzymatic activity are decreased in immotile compared with motile sperm. We have amplified aromatase mRNA by real-time polymerase chain reaction in spermatozoa from asthenospermic, teratospermic and asthenoteratospermic men and recorded, respectively, 44, 52 and 67 per cent decreases of the amount of transcripts compared with fertile donors. A high degree of correlation (r = -0.64) between the abnormal spermatozoa (especially microcephaly and acrosome malformations) and aromatase/GAPDH transcript ratio has been observed. Idiopathic infertility is a wide health problem and no treatment is currently available. In humans, even if the role of oestrogens in spermatogenesis is still a matter of debate, the observations of decreased sperm number and motility in men genetically deficient in aromatase, together with our data and those reported in the literature, may suggest a role for aromatase/oestrogens not only during the development and maintenance of spermatogenesis but also in the final maturation of spermatozoa.

Binding characteristics and regulation of the 17,20β,21-trihydroxy-4-pregnen-3-one (20β-S) receptor on testicular and sperm plasma membranes of spotted seatrout (Cynoscion nebulosus)

The binding characteristics of 17,20β,21-trihydroxy-4-pregnen-3-one (20β-S) to plasma membranes prepared from the testes and sperm of spotted seatrout (Cynoscion nebulosus) were investigated using a filtration method to retain the bound 20β-S. A single class of high affinity (Kd = 17.9 nM), low capacity (Bmax = 0.072 nM g-1 testes) binding sites was identified by saturation and Scatchard analyses on testicular membranes of spermiating spotted seatrout. A corresponding receptor (Kd = 22.17 nM, Bmax = 0.00261 nM ml-1 milt) was also detected in spermatozoan membrane preparations. The rates of 20β-S association and dissociation were rapid, both had Thalfs of less than 1 min. Competition studies indicated that the receptor was highly specific for 20β-S. 17,20β-dihydroxy-4-pregnen-3-one, which had the highest affinity of the other steroids tested, had a relative binding affinity (RBA) of 14.3%. Progesterone, 11-deoxycortisol and testosterone competed with an order of magnitude less affinity (RBA's of 7.4, 1.8 and 1.1%, respectively). Estradiol displayed low affinity for the receptor (RBA = 0.4%) and cortisol did not cause any displacement at 1000-fold excess concentration. Specific 20β-S receptor binding was detected in plasma membranes from testes of both spermiating and non-spermiating seatrout and on spermatozoa. Prolonged incubation of testicular fragments from a spermiating fish with gonadotropin (15 IU ml-1 human chorionic gonadotropin) or forskolin (10 µM) caused a 2–3 fold increase in membrane receptor binding. Previous studies have shown that gonadotropin-induced upregulation of the 20β-S plasma membrane receptor in seatrout ovaries is required for the oocytes to become responsive to 20β-S and undergo final maturation. The existence of a 20β-S membrane receptor on sperm and its upregulation in the testes by gonadotropin raises the possibility that final maturation of spermatozoa in male seatrout may be regulated by a similar mechanism.

Uterine changes during capacitaion in the golden hamster.

‘CAPACITATION’ was defined by Chang1 as the final maturation of spermatozoa in the female genital tract. Since Chang's report considerable research has been directed towards this phenomenon2,3. Capacitation has been observed outside the female tract in such areas as the eye or urinary bladder4 as well as in vitro with follicular fluid5 or eosinophils6. The viability of ejaculated sperm is determined by factors such as levels of oestrogen and progesterone7, and the phase of the oestrous cycle, including the different positions in the female genital tract8. Hunter9 has recently demonstrated in hamsters that ejaculated spermatozoa exposed to oestrous uterus underwent capacitation with a high rate of zona penetration. He concluded that an incubation effect occurred directly between the uterine environment and the spermatozoa. Even though the epididymal sperm were capacitated, they were not very fertile9. It seems that for normal fertilization the uterine environment and seminal plasma are indispensable factors. In studying mammalian fertilization I became interested in the role of the uterine epithelium in capacitation. This preliminary report describes uterine changes during capacitation. A detailed report will be published elsewhere.