Asscorbic acid portects against male infertility in a teleost fish

An animal unable to synthesize ascorbic acid uniquely minicks human and non-human primates. Therefore, in this study we used the rainbow trout, a teleost fish, as the model animal to study the importance of dietary ascorbic acid on the fertilizing ability of sperm. A high concentration of ascorbic acid in semen plays a key role in maintaining the genetic integrity of sperm cells, by preventing oxidative damage to sperm DNA. This study will show that the concentration of asorbic acid in seminal plasma refelcts the dietary fed either an ascorbate-free diet (from 4.74±0.9 to 0.16±0.08 g ml^–1) or an ascorbate-rich diet (from 37.9±4.7 to 17.7± 3.2 g ml^–1) during the sperimnation season. The relationship between ascrobate status and fertility was studied in six groups of fish fed graded levels of ascorbic acid, which sperimated over a 150-day-period. Sperm from individual males was used to fertilize several batches of eggs. When the seminal plasma ascorbate concentration decreased to 7.3 g ml^–1 a significant decrease of fertilization rate and the hatching rate of embryos resulted. This is the first evidence that dietary ascorbate level directly affected sperm quality and influenced male fertility in a scruvy-prone vertebrate.     

Control of sperm motility and fertility: Diverse factors and common mechanisms

Spermatozoa generated in the testis are immature and incompetent for fertilization. During their journey toward the egg, the sperm acquire fertility and achieving fertilization. These sperm modifications to ensure fertilization are induced by many female or male extra-sperm factors: for example, sperm motility-activating factors from the egg jelly, sperm attractants from the eggs, and decapacitation factors from the seminal plasma. The factors controlling sperm fertility are myriad and species specific; they may be peptides, sugar chains, or small organic compounds. Nevertheless, the fundamental mechanisms underlying fertilization must be common among all animals; increase in [Ca²⁺]_i triggers all the steps in the process of fertilization, and cAMP plays important roles in many steps. Elucidating the dynamic functional and morphological changes in sperm cells is important for understanding the regulation of fertilization. Here, we introduce the diversity and generality of the control of sperm fertility. Received 28 April 2008; received after revision 13 June 2008; accepted 17 June 2008     

Serine protease PRSS55 is crucial for male mouse fertility via affecting sperm migration and sperm–egg binding

Testis-specific PRSS55 is a highly conserved chymotrypsin-like serine protease among mammalian species. So far, the physiological function of PRSS55 remains unknown. Here, we show that PRSS55 is a GPI-anchored membrane protein, specifically expressed in adult mouse testis and mainly observed in the luminal side of seminiferous tubules and sperm acrosome. Mice deficient for Prss55 develop male infertile with normal reproduction-related parameters observed. Interestingly, in vivo fertilization rate of Prss55^?/? males is dramatically decreased, possibly due to incapable migration of Prss55^?/? sperm from uterus into oviduct. However, in vitro fertilization rate has no difference between two genotypes although Prss55^?/? sperm presents defective recognition/binding to zona-intact or zona-free oocytes. Further study reveals that mature ADAM3 is almost undetectable in Prss55^?/? sperm, while precursor ADAM3 remains unchanged in the testis. However, it is shown that ADAM3 has no interaction with PRSS55 by immunoprecipitation with anti-PRSS55 antibody. The expression levels of several proteins known to be related to the observed phenotypes remain comparable between wt and Prss55^?/? mice. Moreover, we found that Prss55 deficiency has no effect on PRSS37 or vice versa albeit two mutant males share almost the same phenotypes. Microarray analysis reveals a total of 72 differentially expressed genes in Prss55^?/? testis, most of which are associated with cellular membrane and organelle organization, protein transport and complex assembly, and response to stimulus and signaling. In conclusion, we have demonstrated that PRSS55 plays vital roles in regulating male fertility of mice, including in vivo sperm migration and in vitro sperm–egg interaction, possibly by affecting the maturation of ADAM3 in sperm and the expression of multiple genes in testis.     

The formation of disulfide bonds in human protamines during sperm maturation.

The disulfide contents of human sperm heads, as measured by reduction to the sulfhydryls and subsequent alkylation with 14C-iodoacetamide, increase about 2-fold during the sperm passage from the caput to caudal epididymides. Majority of the increased disulfides resides in the human protamine fractions.     

Glycoconjugates in sperm function and gamete interactions: how much sugar does it take to sweet-talk the egg?

Glycoconjugates in the mammalian reproductive tract are critical components of the molecular mechanisms that control sperm maturation, sperm transport and gamete interactions. In the oviduct of many species, sperm transport and maturation are regulated by protein-carbohydrate interactions that form a sperm reservoir. Subsequently, gamete interactions are mediated by the binding of lectin-like sperm proteins with carbohydrate moieties on the zona pellucida. The sperm glycocalyx is extensively modified during sperm transport and maturation. Multiple functions have been proposed for this dense carbohydrate layer overlying the sperm plasmalemma, and sperm-surface carbohydrates have been implicated in immune-mediated human infertility. The structure and function of glycoconjugates in the oviductal sperm reservoir, the zona pellucida, and on the sperm surface are reviewed.     

Aberrant protamine 1/protamine 2 ratios in sperm of infertile human males

Summary Protamines were extracted from the sperm of fertile and infertile human males and the relative proportion of protamines 1, 2, and 3 were determined by scanning microdensitometry following electrophoresis of total protamine in polyacrylamide gels. The proportion of the three protamines was found to be similar in sperm obtained from different normal males. The distribution of protamines in sperm obtained from a select group of infertile males producing an elevated level of large sperm heads, in contrast, was different from that of the fertile males.     

Aberrant protamine 1/protamine 2 ratios in sperm of infertile human males

Protamines were extracted from the sperm of fertile and infertile human males and the relative proportion of protamines 1, 2, and 3 were determined by scanning microdensitometry following electrophoresis of total protamine in polyacrylamide gels. The proportion of the three protamines was found to be similar in sperm obtained from different normal males. The distribution of protamines in sperm obtained from a select group of infertile males producing an elevated level of large sperm heads, in contrast, was different from that of the fertile males.     

Partial purification of components from fasting human blood serum which stimulate the forward migration of human spermatozoa

Summary Components from fasting human serum that could stimulate the forward migration of human spermatozoa were isolated by gel filtration on Sephadex G-25. The results suggest that these components may be used to enhance sperm forward migration and, hence, pregnancy rate in artificial insemination with husband's semen, (AIH) especially in cases where the sperm forward migration is not optimal.This work was supported by a grant from the World Health Organization.     

Biological effects of trilostane in vitro on oocyte maturation and fertilization in the hamster

Summary The effects of the inhibition of steroidogenesis by trilostane on oocyte maturation were examined by studying spontaneous maturation and fertilization in vitro. 10^–6 M trilostane had no influence on the meiotic process, whether the oocytes were naked or not. At a concentration of 10^–6 M and 10^–7 M trilostane, low normal pronuclear formation and high polyspermy were found during in vitro fertilization. However, no retarded male pronuclear development could be detected in the trilostane-treated group. Thus, steroid producing activity within ova is apparently necessary to prevent multiple sperm penetration, but it has no effect on meiosis or the action of the so-called male pronucleus growth factor (MPGF).     

The effects of sodium and amiloride on the motility of the caudal epididymal spermatozoa of the rat

Summary The forward motility of the rat caudal epididymal spermatozoa has been studied in different Na⁺ concentrations. When spermatozoa were suspended in a completely Na⁺-free solution, the forward motility suffered a progressive fall and after 3 h was completely suppressed. This effect was fully reversible on resuspending the spermatozoa in a solution containing Na⁺. Amiloride caused a fall in motility and the effect was similar to that of Na⁺ removal. The inhibition by amiloride of the motility was concentration dependent and the dose response curve showed an IC₅₀-value of about 5×10^–5 M. The role of Na⁺ influx in the maintenance of sperm motility was discussed.This work was supported by the World Health Organization.The technical assistance of Mr C.M. Li and the gift of amiloride from Merck, Sharp and Dohme are gratefully acknowledged.     

Two-step acquisition of motility by insect spermatozoa

High motility of eupyrene sperm of a grasshopper (Omocestus ventralis) was induced by cAMP. Both trypsin and cAMP were necessary for high motility of eupyrene sperm of three other species of grasshoppers. The same was found for apyrene sperm of the silkmoth,Bombyx mori, when they had been wahsed free from seminal plasma. On the other hand, in locusts (Locusta migratoria), in which the yellow gland has high Arg-C endopeptidase activity, sperm motility was induced by trypsin, like that of apyrene sperm of Lepidoptera. Thus in these two orders of Insecta, sperm motility appears to be induced by the same two-step process: the first step by Arg-C endopeptidase, and the second by cAMP.     

Semenogelin I: a coagulum forming, multifunctional seminal vesicle protein

Human seminal plasma spontaneously coagulates after ejaculation. The major component of this coagulum is semenogelin I, a 52-kDa protein expressed exclusively in the seminal vesicles. Recently, a sperm motility inhibitor has been found to be identical to semenogelin I, suggesting that it may also be a physiological sperm motility inhibitor. The protein is rapidly cleaved after ejaculation by the chymotrypsin-like prostatic protease prostate-specific antigen, resulting in liquefaction of the semen coagulum and the progressive release of motile spermatozoa. Some of the cleavage products of Sg I may also have various biological functions. While the semenogelin I protein is unique to human and higher primates, it has recently been shown to belong to a gene family having a similar gene structure but encoding widely differing proteins. The recently elucidated characteristics of the semenogelin I gene as well as the biochemical and functional properties of the encoded protein are reviewed, and an attempt is made to integrate the various findings into a model for semen coagulation, sperm immobilization and potential other functions. Received 21 October 1998; received after revision 15 December 1998; accepted 15 December 1998     

New insights into the molecular mechanisms of sperm-egg interaction

At the moment of insemination millions of mammalian sperm cells are released into the female reproductive tract in order to find a single cell – the oocyte. The spermatozoa subsequently ignore the thousands of cells they make contact with during their journey to the site of fertilisation, until they reach the surface of the oocyte. At this point, they bind tenaciously to the acellular coat, known as the zona pellucida, that surrounds the oocyte and initiate the chain of cellular interactions that will culminate in fertilization. These exquisitely cell- and species-specific recognition events are among the most strategically important cellular interactions in biology. Understanding the cellular and molecular mechanisms that underpin them has implications for diagnosis of the aetiology of human infertility and the development of novel targets for fertility regulation. Herein, we describe two models indicating the plethora of highly orchestrated molecular interactions underlying successful sperm zona binding and sperm oocyte fusion. Received 17 December 2006; received after revision 31 January 2007; accepted 16 March 2007     

Disruption of sperm release from insect testes by cytochalasin and β-actin mRNA mediated interference

Release of sperm bundles from moth testes is controlled by the local circadian oscillator. The mechanism which restricts migration of sperm bundles to a few hours each day is not understood. We demonstrate that a daily cycle of sperm release is initiated by the migration of folded apyrene sperm bundles through a cellular barrier at the testis base. These bundles have conspicuous concentrations of actin filaments at their proximal end. Inhibition of actin polymerization by cytochalasin at a specific time of day inhibited sperm release from the testis. Likewise, application of double-stranded actin RNA specifically inhibited sperm release. This RNA-mediated interference (RNAi) lowered the pool of actin mRNA in tissues involved in sperm release. The decline in mRNA levels resulted in the selective depletion of F-actin from the tip of apyrene sperm bundles, suggesting that this actin may be involved in the initiation of sperm release. Combined results of RNAi experiments at physiological, cellular and molecular levels identified unique cells that are critically involved in the mechanism of sperm release.Received 11 April 2003; received after revision 2 May 2003; accepted 27 May 2003     

Sperm predence in a hermaphroditic nematode (Caenorhabditis elegans) is due to competitive superiority of male sperm

When male and hermaphroditeCaenorhabditis elegans mate, the male's sperm outcompete the hermaphrodite's own sperm and fertilize a majority of the offspring. Here, we investigate the mechanism of male sperm precedence. We rule out the possibility that male sperm are stronger and more competitive because they are activated later than hermaphrodite sperm. We also find that a previously known gender difference in sperm activation does not influence sperm competition. Male sperm, rinsed free of seminal fluid, retained the capacity to take precedence after artificial insemination. Therefore, we conclude that male sperm themselves are competitively superior to hermaphrodite sperm. This trait maximizes outcrossing after mating and may increase both genetic diversity and heterozygosity of offspring whose parents, due to self-fertilization, may be highly homozygous.     

A sperm GPI-anchored protein elicits sperm-cumulus cross-talk leading to the acrosome reaction

The acrosome reaction has long been thought to be induced by the zona pellucida. Here we report the identification and function of a novel human sperm glycosylphosphatidylinositol (GPI)-anchored membrane protein, NYD-SP8. The release of the protein during sperm-egg interaction and its binding to the cumulus, the first layer of egg investment, elicits cross-talk between the gametes and produces calcium dependant release of progesterone, which lead to the acrosome reaction. An in vivo mouse model of NYD-SP8 immunization is also established showing a reduced fertility rate. Thus, contrary to accepted dogma, our study demonstrates for the first time that, prior to reaching the zona pellucida, sperm may release a surface protein that acts on the cumulus cells leading to the acrosome reaction, which may be important for determining the outcome of fertilization. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Received 11 August 2008; received after revision 18 December 2008; accepted 22 December 2008     

Purification from human plasma of endogenous dodium transport inhibitor(s)

Summary Na⁺, K⁺-ATPase inhibitors extracted from plasma of healthy human subjects displaced³H-ouabain binding to human erythrocytes and inhibited the Na⁺ efflux catalyzed by the Na⁺, K⁺-pump and unexpectedly the Na⁺, K⁺-cotransport system without alteration of the Na⁺, Na⁺-exchange or the Na⁺ passive permeability. This suggests the presence in healthy human plasma of endogenous factors with ouabain-like and furosemide-like activities.Acknowledgments. We are indebted to Dr M. A. Devynck for her advice on chemical measurements and to Dr R. P. Garay for his help with flux measurements     

The epididymis-specific antimicrobial peptide β-defensin 15 is required for sperm motility and male fertility in the rat (<Emphasis Type="Italic">Rattus norvegicus</Emphasis>)

Spermatozoa acquire forward motility and fertilizing capacity during their transit through the epididymis. The maturation process involves modifications of the sperm surface by different proteins that are secreted by a series of specialized regions in the epididymal epithelium. Here we show that the rat epididymis-specific β-defensin 15 (Defb15) exhibits an androgen-dependent expression pattern, and it can bind to the acrosomal region of caput sperm. Coculture of caput spermatozoa with Defb15 antibody in vitro resulted in a significant decline in sperm motility. Moreover, the total and progressive motility of the spermatozoa dramatically decreased in rats when Defb15 was downregulated by lentivirus-mediated RNAi in vivo. Remarkably, knock down of Defb15 led to a reduction in fertility and embryonic development failure. In addition, the recombinant Defb15 showed antimicrobial activity in a dose-dependent fashion. These results suggest that Defb15 plays a dual role in both sperm maturation and pathogen defense in rat epididymis.     

Some properties of external NADH oxidation by human placental mitochondria

Summary Isolated human term placenta mitochondria catalyse oxidation of external NADH in the presence of cytochrome c. This reaction is insensitive to the respiratory chain inhibitors such as rotenone and antimycin A, and is not coupled to phosphorylation. Comparison of the effect of Mg⁺⁺ ion on NADH plus cytochrome c oxidation by human term placental, human skeletal muscle and rat skeletal mitochondria showed that Mg⁺⁺ ion exerts an inhibitory effect in the case of human mitochondria and a stimulatory effect in the case of rat skeletal muscle mitochondria.This work has been supported by a grant from Ministry of Higher Education Science and Technology within the project No. 01.02.     

Satellite DNA (II) from sea urchin (Lytechinus variegatus) sperm

Summary When DNA isolated from freshly collected sperm of sea urchin (Lytechinus variegatus) is centrifuged to equilibrium in CsCl, 2 heavy satellite bands appear beside the main band DNA. Satellite DNA (II) appears in between the main band DNA (=1.695 g/cm³) and the rDNA satellite (=1.722 g/cm³). Satellite DNA (II) has a buoyant density 1.710 g/cm³, corresponding to 50% GC content. It is speculated that the satellite DNA (II), which appears to be of high mol.wt, might contain the sequences complementary to histone mRNA.Acknowledgment. This work was carried out in the laboratory of Dr D. W. Stafford, Department of Zoology, University of North Carolina, Chapel Hill, N.C., USA. I thank him for his help and cooperation.