Assessment of the human sperm acrosome reaction using concanavalin A lectin

A method for assessment of the human sperm acrosome reaction is reported using fluorescein isothiocyanate (FITC)-conjugated Concanavalin A (ConA). The technique involved labelling prefixed spermatozoa, where only those spermatozoa that showed a complete loss of the acrosome bound FITC-ConA to the acrosomal region. Competitive sugar binding studies demonstrated that binding of ConA lectin to the acrosomal area of human spermatozoa was inhibited in the presence of 0.2 M D-mannose. Staining with the supravital stain Hoechst 33258 (H258) concomitantly with FITC-ConA allowed determination of only those spermatozoa that had undergone a true and not degenerative acrosomal loss. Incubation of human spermatozoa with 0, 1, 5, and 25 microM calcium ionophore, A23187, for 60 min demonstrated that changes in acrosomal status due to the different treatment protocols may be determined by the dual-staining method. Electron microscopy studies revealed that gold-conjugated ConA bound specifically to the surface of the inner acrosomal membrane of acrosome-reacted spermatozoa. A significant correlation (r = +.97) between transmission electron microscopy (TEM) and FITC-ConA labelling methods of acrosomal status assessment was achieved. The simple ConA labelling procedure reported here therefore provides a reliable method for quantitation of the physiological acrosome reaction of a population of human spermatozoa.     

Reproduction in mice: The fate of spermatozoa not involved in fertilization

Mechanisms were sought through which the control of preimplantation mouse embryo development by spermatozoa might be effected. A potential route for the transmission of sperm-dependent stimuli to C3HeB/FeJ females was uncovered. It was found that within 24–48 hr after artificial insemination with spermatozoa, in which the DNA had been labeled with tritiated thymidine, a minimum of 9% of the radioactivity was transported across the uterine walls. It was deposited among the maternal tissues in a pattern that differed from the patterns of isotope distribution obtained when either free tritiated thymidine or Escherichia coli cells containing DNA labeled with tritiated thymidine were used instead of labeled sper-matozoa. In sperm-treated animals the ovaries, the adrenals, and a mesenteric lymph node exhibited strikingly large accumulations of radioactivity. The heart, spleen, and uterus manifested lesser accumulations of label, but were higher than liver, kidney, lung, brain, muscle, and intestine. The specific activity of the lymph node was found to decrease during the 12–72-hr period following insemination. This result led to the hypothesis that the lymphatic system could serve as a route for the dissemination, to maternal tissues, of radioactivity originally associated with spermatozoa deposited in the uterus. Heat-inactivated spermatozoa, which have the potential for facilitating the first cleavage of fertilized embryos, exhibited a distribution pattern indistinguishable from untreated spermatozoa. Sperm protein kinase was found to survive the heat inactivation of spermatozoa. This stability was interpreted as being compatible with the kinase functioning as an intermediary in the transmission of sperm-dependent stimuli that control preimplantation embryo development in mice.     

Energy metabolism of spermatozoa of the sea urchin Glyptocidaris crenularis

Energy metabolism in spermatozoa of the sea urchin Glyptocidaris crenularis was examined. The spermatozoa contained not only several kinds of phospholipids and cholesterol but also triacylglycerides (TG). Following dilution of the dry sperm in sea water, the TG content decreased rapidly. Other lipids, however, remained at constant levels, except for an increase in the level of free fatty acid. Oil red-O staining of spermatozoa showed that TG was principally located in part of the sperm midpiece. Also, high lipase activity was demonstrated in the spermatozoa. In both intact cells and a cell-free system, 14C-labeled fatty acids were oxidized to 14CO2. It is thus concluded that G. crenularis spermatozoa use TG as a substrate for energy metabolism.     

Hormonal regulation of zona-binding ability and fertilizing ability of rat epididymal spermatozoa

Rat spermatozoa from the proximal caput, the proximal corpus, the middle corpus, and the distal cauda epididymidis were examined for their ability to bind to the zona pellucida after a 1-, 2.5-, or 4.5-h incubation at 34°C with rat eggs in cumulus. Caput spermatozoa did not bind to the zona after 1, 2.5, or 4.5 h of incubation. Corpus spermatozoa did bind to the zona, but the percentage of eggs with bound spermatozoa and number of bound spermatozoa per egg increased with the length of incubation. Cauda spermatozoa bound readily to the zona pellucida, and their zona binding ability did not change with longer incubations. It thus appears that rat spermatozoa gradually acquire the ability to bind to the zona pellucida in the corpus epididymidis. The zona-binding capacity of cold immobilized cauda spermatozoa, defined as the percentage of eggs with bound spermatozoa, increased with the number of spermatozoa incubated and reached a plateau characteristic of the endocrine status of the animal. After castration, zona-binding ability is progressively lost from day 3 until day 10 where it is nil. Testosterone supplementation maintains zona-binding ability to control levels. Similarly, fertilizing ability declines from day 5 after castration until day 10. Testosterone prevents this loss of fertilizing ability. It thus appears that the development of zona-binding ability during epididymal transit is, like the development of fertilizing ability, under androgen regulation. The close correlation between the onset of fertilizing ability and zona-binding ability during maturation, the loss of fertilizing ability and zona-binding ability after castration, and the recovery of both fertilizing ability and zona-binding ability with testosterone treatment suggests that the androgen-dependent development of zona-binding ability is an important component of the acquisition of sperm fertilizing ability during epididymal transit.     

Osmotic sensitivity of canine spermatozoa

The objective of this study was to determine osmotic tolerance of canine spermatozoa. The study comprised three experiments: (1) spermatozoa suspended either in an egg yolk-citrate (EYC) extender or in Kenney skim milk extender were exposed to NaCl solutions ranging from 290 to 1500 mOsm; (2) spermatozoa suspended in EYC were exposed to 550 to 1500 mOsm solutions of glucose, galactose, or fructose; and (3) spermatozoa suspended in EYC or glucose-bovine serum albumin (G-BSA) were exposed to 0.6 M (approximately 900 mOsm) or 1.2 M (approximately 1600 mOsm) solutions of glycerol, ethylene glycol (EG), or dimethyl sulfoxide (Me(2)SO). In all experiments, motility and membrane integrity of spermatozoa were assessed after they were diluted into isotonic medium at 37 degrees C. Exposure of canine spermatozoa to solutions of either NaCl or monosaccharides at osmolalities >500 mOsm caused a significant reduction of motility (P<0.01). Motility of spermatozoa was more affected by osmotic stress than their membrane integrity. Osmotic sensitivity of canine spermatozoa was dependent on the type of extender; spermatozoa suspended in the Kenney extender were more resistant to osmotic stress than those suspended in the EYC extender. Despite their sensitivity to exposure to high concentrations of nonpermeating agents, canine spermatozoa were rather resistant to exposure to glycerol and EG. However, Me(2)SO was toxic to canine spermatozoa; motility was substantially reduced after spermatozoa were exposed to 0.6 M Me(2)SO. The type of extender also affected the sensitivity of canine spermatozoa to Me(2)SO; spermatozoa suspended in the EYC extender were more resistant than those suspended in G-BSA. It was concluded that canine spermatozoa are sensitive to osmotic stress, but are tolerant to shrinking and swelling caused by exposure to permeating cryoprotectants.     

Sperm release from oviduct epithelial binding is controlled hormonally by peri-ovulatory graafian follicles

To avoid inappropriate conclusions being drawn from the extensive use of in vitro preparations of sperm-oviduct epithelial binding, it is recalled that events in the genital tract of mammals are regulated by the gonads, primarily by their changing secretion of steroid hormones. Key observations from in vivo models are used to emphasise the dynamic interactions between viable sperm cells and the caudal (distal) portion of the oviduct isthmus, the site of the functional sperm reservoir. These include (1) pre-ovulatory arrest and epithelial binding of intact sperm cells and thereby suppression of completion of capacitation, (2) peri-ovulatory activation and release from binding of discrete sub-populations of competent spermatozoa, and (3) post-ovulatory liberation of large numbers of spermatozoa. These observations underline the influence of endocrine regulation of sperm binding and release by peri-ovulatory Graafian follicles, a point brought out by the enhanced sperm release prompted by diverse treatments with solutions of progesterone. In the light of this evidence, the suitability of in vitro preparations for clarifying physiological events should be questioned, especially if myosalpingeal catecholamines diffusing out of the autonomic nervous system contribute to sperm activation and/or release. None of this is to infer that sperm cells themselves are without influence on their epithelial binding reaction(s). Nor is it to suggest that in vitro models of sperm-oviduct binding are without relevance to the development of sperm evaluation technologies. However, pre-ovulatory sperm-epithelial binding and a regulated peri-ovulatory release should be seen as vital tactics in the overall strategy of achieving successful monospermic fertilisation.     

Reduction of seminal plasma concentration can decrease detrimental effects of seminal plasma on chilled ram spermatozoa

This study was conducted to investigate the effect of different levels of seminal plasma (SP) and cold-shock on ram spermatozoa during 36 h storage at 5°C. In both ejaculated spermatozoa coated with egg yolk (second ejaculate; coated spermatozoa) and epididymal spermatozoa, samples were treated with 0, 50 and 100% seminal plasma. Different levels of seminal plasma were added on the basis of ram spermatocrit (32%). Then half of aliquots were suddenly put on ice water (cold-shock) and other half were gradually (0.25°C/min) chilled (non- cold shock). Sperm motility, viability and functional membrane integrity were determined in both aliquots at 0, 12, 24 and 36 h storage at 5°C. Under non- cold shock and cold-shock conditions, coated spermatozoa treated with 0% SP showed the highest motility compared to ejaculated spermatozoa (first ejaculate; uncoated spermatozoa) after 12, 24 and 36 h of storage at 5°C (P<0.05). Under non- cold shock and cold-shock conditions, viability and functional membrane integrity was higher in the coated spermatozoa treated with 0% SP than in the uncoated spermatozoa during 36 h storage (P<0.05). There was no significant difference between coated spermatozoa treated with 0 and 50% SP in the percentage of motility and viability after 24 and 36 h of storage (P>0.05). Under non- cold shock and cold-shock conditions, the percentage of motility of epididymal spermatozoa treated with 0% SP was significantly (P<0.05) higher than those treated with 100% SP after 36 h of storage at 5°C. In conclusion, removal of seminal plasma and/or reduction (up to 50%) of its concentration can decrease detrimental effects of seminal plasma on chilled ram spermatozoa.     

Circular movement of honey bee spermatozoa inside spermatheca

It is believed that in honey bees spermatozoa stored inside the spermatheca remain motionless, however, some studies have reported the contrary. To observe behaviour of spermatozoa inside spermathecae, we have instrumentally inseminated queens with spermatozoa stained with fluorescent stains. During the first 8 h after insemination movement of the spermatozoa was stationary, without fast forward movement. Later, we observed circular movement of the spermatozoa inside spermathecae. Numerous circles were visible at one time. The circles were located close to the spermathecal wall. Movement of the spermatozoa was also observed in spermathecae of naturally inseminated queens. The marble-like pattern of the spermathecae was changing. The changes were slow and well visible only when video recordings were played at high speed.     

Boar sperm changes after sorting and encapsulation in barium alginate membranes

A routine use of boar-sexed semen is limited by the long sorting time necessary to obtain an adequate number of sexed spermatozoa for artificial insemination and by the high susceptibility of spermatozoa of this species to damages induced by sorting procedure and subsequent cryopreservation. The aim of this work was to study the impact of encapsulation in barium alginate membrane on sorted boar spermatozoa by evaluating membrane integrity, chlortetracycline staining patterns, protein tyrosine phosphorylation, and Hsp70 immunolocalization during storage over 72 hours in liquid or encapsulated form. The encapsulation procedure significantly (P < 0.05) decreased the overall membrane integrity of control unsorted semen (81.8 vs. 57.4, CTR vs. CPS), but did not negatively affect the overall viability and the chlortetracycline staining patterns of sorted encapsulated cells. Moreover, encapsulation significantly decreased (P < 0.05) the overall phosphotyrosin A pattern cell percentage in unsorted (98.4 vs. 92.6, CTR vs. CPS) but not in sorted semen (64.0 vs. 74.2; SORT CTR vs. SORT CPS). As for Hsp70, the overall percentage of cells displaying the different patterns was significantly influenced (P < 0.05) by treatment but not by storage time. The sorting procedure seems to induce the major changes, whereas encapsulation tends to exert a protective effect on sorted semen by increasing the percentage of spermatozoa displaying the T pattern (2.8 vs. 24.3; SORT CTR vs. SORT CPS). In conclusion, our data confirm that the damaging impact of the encapsulation in barium alginate capsules seems to be limited when compared with that of the sorting procedure and, moreover, the association of the two procedures does not result in an algebraic sum of the negative effects. These results suggest the possibility of a future utilization of the encapsulation technology in order to store sorted spermatozoa and permit their controlled release in the female genital tract.     

A major secretory protein from rat seminal vesicle binds ejaculated spermatozoa

The rat seminal vesicle produces large amounts of a protein-rich fluid that greatly contributes to semen volume. RSV IV, a protein abundantly secreted from this gland, binds in vitro to rat epididymal spermatozoa. However, there is no evidence that this protein may have an in vivo role as a sperm-coating antigen. We report in this paper that high-molecular-weight RSV IV immunologically related proteins can be detected on ejaculated spermatozoa, but not on epididymal spermatozoa. After incubation of purified RSV IV with ejaculated spermatozoa in freshly recovered semen or with epididymal spermatozoa in a medium containing the coagulating gland secretion, sperm-bound proteins with analogous properties were detected. These results support the hypothesis that RSV IV is modified at ejaculation to an high-molecular-weight, sperm-coating antigen.     

Morphology of the male reproductive system and sperm ultrastructure of Leucoptera coffeella (Lepidoptera: Lyonetiidae)

The male reproductive tract of Leucoptera coffeella was processed for light and transmission electron microscopy. In the testis, the eupyrene cells are arranged in individual cysts, while the apyrene cysts form aggregates, never observed in other Lepidoptera. Both cysts contain 128 spermatozoa, which differ from the typical pattern. In the seminal vesicle, both types of spermatozoa are dispersed in the lumen, also different from other Lepidoptera. The apyrene spermatozoa are similar to those observed for other Lepidoptera. They present an anterior region covered by a dense cap and the flagellum is composed of a 9 + 9 + 2 axoneme and two mitochondrial derivatives. The eupyrene spermatozoa, however, differ from the typical pattern for Lepidoptera. Their anterior region contains a nucleus, an acrosome and a peculiar arc of eight accessory microtubules connected to the plasma membrane by dense bridges. In the nucleus–flagellum region, the ninth accessory microtubule is assembled between both mitochondrial derivatives, to participate in the axoneme. The flagellum comprises a 9 + 9 + 2 axoneme and two mitochondrial derivatives with paracrystalline cores. External to the plasma membrane and close to the accessory microtubules, there are tufts of an amorphous material, suggesting reduced lacinate appendages, while the reticular ones are absent. The reduction of lacinate appendages and the absence of sperm bundles in the seminal vesicle support the concept that the appendages of other Lepidoptera could be associated with the eupyrene aggregations. The characters ‘number of spermatozoa per cyst’ and ‘absence of bundles’ should be considered plesiomorphic, supporting the position of this taxon in the base of the Ditrysia.     

Isolation of motile spermatozoa by density gradient centrifugation in Percoll®

A procedure using centrifugation in density gradients composed of Percoll was developed for isolation of spermatozoa from mammalian semen. To evaluate the technique, rabbit, human, or bovine semen was layered over continuous Percoll gradients ranging in density from 1.02 to 1.13 gm/ml and centrifuged at 1,500g for 45 min. After centrifugation, the seminal plasma remained above the gradient, whereas the spermatozoa and seminal particles were distributed within the gradient according to their buoyant densities. Unlike most washing techniques, no sperm pellet was formed; instead, the spermatozoa were concentrated into a compact band above the most dense layer of Percoll. The spermatozoa recovered from the gradient were easily resuspended by gentle techniques. Thus, the mechanical stress to the spermatozoa was minimized. Osmotic stress to the spermatozoa was also negligible as the Percoll gradients were isotonic throughout. Spermatozoa obtained by this technique possessed motility equivalent to that of spermatozoa in the unfractionated semen. Sperm suspensions recovered from the gradients contained less than 5% of the nonspermatozoal particles present in the original samples of unfractionated semen. Soluble seminal components were also efficiently removed from the spermatozoa. Thirty billion bovine spermatozoa could be fractionated on a single gradient without loss of effectiveness. Recovery of spermatozoa from these preparative separations averaged 80%. These results demonstrated that Percoll was a superior medium for efficient density gradient isolation of motile spermatozoa free of contamination by other seminal constituents.     

Computerized analysis of the motility parameters of hamster spermatozoa during maturation

A computer-aided semen analysis system was used for the objective assessment of hamster spermatozoa during epididymal maturation. The caput epididymal spermatozoa were extremely sluggish, achieved very little progression, and the three velocity parameters, namely curvilinear velocity (VCL), progressive velocity (VSL), and path velocity (VAP), were low. These spermatozoa during progressive movement alternated between the linear shape and “U” shape or attained an “S” shape prior to changing to the “U”; shape. The corpus epididymal spermatozoa were faster, displayed greater VSL, VAP, and VCL compared to caput epididymal spermatozoa, and, during forward motility, attained “U,” “C,”; and (or) “?” shape as in the wriggling motility pattern. The proximal cauda epididymal spermatozoa were actively motile and VSL, VAP, and VCL in these spermatozoa were more than 10 times greater compared to the caput epididymal spermatozoa. The proximal cauda epididymal spermatozoa predominantly moved in circles and with time became slower and more circular in their trajectories and exhibited a reduction in LIN (linearity). The distal cauda epididymal spermatozoa were very similar to the proximal cauda epididymal spermatozoa with respect to their fast motility (VSL, VAP, and VCL are similar) and beat cross frequency (BCF), but showed larger values for STR (straightness) and LIN and moved along curved trajectories. The amplitude of lateral head displacement (ALH) was also considerably lower in the distal cauda epididymal spermatozoa compared to the proximal cauda epididymal spermatozoa. Thus, this study provides for the first time data related to seven motility parameters for caput and corpus epididymal spermatozoa of hamster. It also provides additional data with respect to VCL, LIN, BCF, and ALH for proximal and distal cauda epididymal spermatozoa of hamster. © 1994 Wiley-Liss, Inc.     

Production,characterization, and use of ionophore-induced,calcium-dependent acrosome reaction in ram spermatozoa

A system has been developed for inducing a calcium-dependent acrosome reaction in ram spermatozoa in vitro using the calcium ionophore A23187. The resultant reaction is accompanied by release of the acrosomal enzymes hyaluronidase and acrosin, but there is no release of the cytoplasmic enzyme glucose 6-phosphate isomerase. In any given cell, the visible acrosome reaction apparently takes place rapidly, but there is a variable delay before the reaction occurs. Under optimum conditions, about 90% of treated spermatozoa show an acrosome reaction within one hour. Preincubation of the spermatozoa with the proteinase inhibitors p-amino-benzamidine or p-nitrophenylguanidinobenzoate allows two stages of the reaction to be distinguished ultrastructurally, a membrane fusion stage followed by a dispersal of the acrosomal matrix. In the presence of the inhibitors, the first stage is delayed but is completed within 1 hour, whereas the second remains largely incomplete. In the presence of calcium, ionophore concentrations which induce an acrosome reaction abolish sperm motility rapidly and completely. However, by adding serum albumin shortly after addition of ionophore, motility can be preserved while the acrosome reaction occurs as usual; the motility pattern observed under these conditions is of the “whip-lash” or “activated” type. Although the motile ionophore-treated spermatozoa were unsuccessful at penetrating normal mature sheep oocytes in vitro, they were able to penetrate zona-free oocytes, after which swelling and decondensation of the sperm head took place.     

The phylogenetic significance of sperm morphology in the Platyhelminthes

The phylogenetic significance of flatworm sperm morphology is discussed against the background of general spermatology. The modified type of spermatozoon of the Nemertodermatida, a group of primitive flatworms, indicates that the Platyhelminthes evolved from forms characterized by the primitive type of metazoan sperm and by the primitive mode of fertilization, implying the release of sperm freely into sea water.The occurrence of aberrant types of spermatozoa in most platyhelminths is obviously a consequence of early evolution of the internal mode of fertilization, which characterizes all true members of this group. It can be concluded, from the ultrastructure of these aberrant spermatozoa that higher metazoans cannot have evolved from seriated flatworms related to the recent Seriata (Proseriata and Tricladida). Even the seemingly primitive Acoela have such aberrant spermatozoa that evolution of higher metazoans from acoels related to the recent Acoela seems highly improbable.The ultrastructure of the spermatozoa of the parasitic groups of flatworms (Monogenea, Digenea, Cestoda) is very similar to that found in the Kalyptorhynchia, a further indication that the parasitic groups are related to the rhabdocoel turbellarians.     

Effects of caffeine and casein phosphopeptides on fertilization in vitro of pig oocytes matured in culture

Two experiments were conducted to assess the effects of caffeine and casein phosphopeptides (CPPs). One experiment tested the ability of frozenthawed epididymal spermatozoa from boar (A, B, C), of proven low in vitro fertilization rates, to penetrate pig follicular oocytes. The other experiment tested the ability of ejaculated spermatozoa to uptake Ca²⁺. In Experiment 1, oocytes matured in vitro were inseminated with spermatozoa (Boar A) in medium that contained 0, 2, 5, 10, 15, and 20 mM caffeine and CPPs (1 mg/ml), or in medium that contained the same caffeine concentrations without CPPs. When CPPs were added to the caffeine-containing medium, significantly higher penetration rates were obtained than when the oocytes were inseminated in the CPPs-free medium. When the oocytes were inseminated with the spermatozoa (Boar A, B, C) in medium that contained 5 mM caffeine and dephosphorylated CPPs (dCPP:1 mg/ml), the penetration rate was significantly lower than when the oocytes were inseminated with the spermatozoa in medium containing 5 mM caffeine and CPPs (1 mg/ml). In Experiment 2, the concentration of Ca²⁺ in ejaculated spermatozoa of proven low in vitro fertilization rates during incubation in the fertilization medium was determined with fluorescence, Fura2/AM. When the medium contained CPPs, the intracellular concentration of Ca²⁺ in spermatozoa increased with a peak of 113 nM after 90 min of incubation. The concentration of Ca²⁺ was gradually decreased in the medium without CPPs. However, addition of CPPs in the medium had no effect on the motility of spermatozoa in Experiments 1 and 2. These results indicate that CPPs promote Ca²⁺ uptake by spermatozoa and are effective for capacitation and/or acrosome reaction of spermatozoa leading to sperm penetration when caffeine is present in the medium and that the effect is reduced by dephosphorylation of CPPs. © 1994 Wiley-Liss, Inc.     

Immunocytochemical localization of DJ-1 in human male reproductive tissue

DJ-1 was identified as an activated ras-dependent oncogene product, and was also found to be an infertility-related protein (contraception-associated protein 1; CAP 1) that was reduced in rat spermatozoa treated with ornidazole, one of the endocrine disrupting substances that causes reversible infertility in rats. CAP 1 is present in spermatozoa but is not detectable in the epididymal fluid of fertile rats and appears to be shed from sperm during treatment with ornidazole. To determine the functions of DJ-1 in the human reproductive system as a target protein of endocrine active substances, we identified the localization of DJ-1 in human testis, epididymis, ejaculated spermatozoa, and seminal plasma. DJ-1 was present in cells existing in the seminiferous tubules and Leydig cells. Some strong expressions were observed in Leydig cells and Sertoli cells, suggesting a relation with spermatogenesis via androgen receptor (AR). In ejaculated spermatozoa, DJ-1 existed on the surface of the posterior part of head and the anterior part of the midpiece. DJ-1 was also present on sperm flagella when the antibody penetrated the plasma membrane, suggesting that there are two putative roles in fertilization, one is binding to the egg, and the other is flagella movement. In contrast to previous findings, we detected DJ-1 in seminal plasma of fertile men. These results demonstrate that DJ-1 in human seminal plasma is not only from spermatozoa but also from the testis and epididymis. It is suggested that DJ-1 may play an important and as yet uncharacterized role in spermatogenesis and fertilization in humans.     

Surface and internal antigens of rat spermatozoa distinguished using monoclonal antibodies

Fluorescent antibody labeling techniques are frequently used to investigate the topography of antigens on spermatozoa. It is generally assumed that these procedures detect molecules only on the sperm surface but we now show that this assumption is not always valid. Using monoclonal antibodies that recognize either surface or internal antigens we demonstrate how spurious conclusions can be made, and we suggest simple procedures for assigning the position of an antigen to the cell surface or to an intracellular organelle. Antibodies against plasma membrane antigens should stain 100% of normal intact spermatozoa, but this proportion should be greatly reduced if the spermatozoa have previously been demembranated. If ? 100% of spermatozoa are stained but the proportion increases following permeabilization, then the possibility should be considered that the antigens are intracellular. We conclude that assignment of an antigen to a regional domain on the sperm surface using fluorescent antibody techniques should be validated by a demonstration that the antigen is actually located on the cell surface.     

Abnormal Sperm Parameters in Humans Are Indicative of an Abortive Apoptotic Mechanism Linked to the Fas-Mediated Pathway

The life cycle of many cell types can hinge on the presence of death factors that can control programmed cell death. The Fas-mediated apoptotic pathway has been implicated in controlling apoptosis during spermatogenesis in a number of mammalian species. In the human, the presence of nuclear DNA damage in ejaculated spermatozoa has pointed to a possible role for apoptosis during spermatogenesis. The presence of other molecular markers of apoptosis has, however, not been shown. More importantly, differences in these markers have not been investigated in men with normal and abnormal sperm parameters. In this study we examine for the presence of the cell surface protein Fas in ejaculated human spermatozoa. Ejaculated spermatozoa (55 samples) were labeled with anti-human Fas antibody and the number of spermatozoa displaying Fas were counted using a fluorescence-activated cell sorter (FACS). In 30/31 (96.8%) normal males (>20 million sperm per milliliter), less than 10% of the spermatozoa were Fas positive. In contrast, 14/24 (58.3%) oligozoospermic samples (<20 million sperm per milliliter) contained more than 10% Fas-positive spermatozoa. Similar differences were observed in men whose spermatozoa had poor motility and morphology. These results indicate that apoptosis is a major mechanism in regulating spermatogenesis in the human and that there are clear differences in molecular markers of apoptosis between males with normal and abnormal sperm parameters. We propose that the presence of Fas-labeled spermatozoa in the ejaculate of these men is indicative of an "abortive apoptosis" having taken place, whereby the normal apoptotic mechanisms have misfunctioned, have been overridden, or have not been completed.     

Giant sperm cells with accessory macrotubules in a neuropteran insect

The flagellar axoneme of the atypical spermatozoa (paraspermatozoa) of Mantispa perla (Neuroptera, Planipennia) contains accessory microtubules or rather macrotubules that are 55 nm in diameter and that has a wall consisting of about 40 protofilaments. The sperm tail further contains two giant mitochondrial derivatives, which during spermiogenesis store an electron dense material. The mature spermatozoon has a flattened acrosome and a elliptical nucleus. These giant spermatozoa may furnish nutrients to the functional spermatozoa (euspermatozoa) when they reach the female genital tracts or/and they function in sperm competition filling the spermatheca.