Changes in binding of a 27-kilodalton chimpanzee cauda epididymal protein glycoprotein component to chimpanzee sperm

Molecular biology of sperm maturation in the human epididymis

Male infertility is a frequent cause of childlessness, and, indeed, a comparison of the contributions to conception failure made by male and female factors shows them to be equally frequent. In practice, male infertility appears to be resistant to most treatments. However, the major reason for this may be that often attempts are carried out without knowing the cause of the problem. Unlike in women, obstructions and hormonal disorders are rare in male infertility. Rather, it would appear that sperm disorders are the most common cause, reflecting a variety of pathogenetic mechanisms. Defects in sperm morphology, defective sperm movement, deficient development or functional failure of the acrosome, and the excessive generation of reactive oxygen species are changes that are often seen in infertile semen, but little is known about their aetiology. In 5–10% of men being treated for infertilty, an autoimmune reaction against spermatozoa is observed. Although the correlation between the presence of systemic antisperm antibodies and fertility potential is poor, the appearance of sperm-bound antibodies of immunoglobulin class IgA in semen seems to be closely associated with infertility. Studies in laboratory animals and humans have shown that complementary adhesion molecules are located on the surface of oocytes and spermatozoa. These molecules interact and lead to gamete fusion. Abnormalities in these molecules on the sperm surface might be expected to contribute to male infertility. However, their clinical significance has not yet been documented, and the molecular basis of human gamete interaction is far from being understood. Therefore, the key to understanding male infertility may lie in basic research which directly targets the fundamental cellular and molecular biology of the human spermatozoon.

Histological effects of androgen deprivation on the adult chimpanzee epididymis

Primate sperm acquire functional maturity, including vigorous forward motility and the ability to fertilize an ovum, as they transit the unique, regional microenvironment of the epididymal lumen. Several proteins secreted into this luminal fluid are epididymal-specific and androgen-dependent, and thus contribute potentially to sperm maturation. For the adult male chimpanzee, we report the effects of GnRH antagonist-induced androgen deprivation on the histology of the epithelia and interstitium composing the ductuli efferentes, ductus epididymis, proximal ductus (vas) deferens. After 21 days of androgen deprivation, epididymal tissues exhibit characteristic atrophic changes, including cellular disorganization, degradation, and loss of structures. Androgen-deprived cytoplasm is differentially and characteristically disrupted, vacuolated, and reduced in volume, resulting in decreased epithelial height and loss of stereocilia. Most principal cell nuclei appear hyperchromatic, smaller in size, more irregular in outline, and disordered in arrangement, while others appear swollen and vacuolated. Apical cells of the efferent ducts and the basal cells and microvillar borders of the ductus epididymis seem minimally affected by androgen deprivation. Such histologically differential responses suggest correspondingly that androgen is differentially essential to the maintenance of the epididymis and thus to normal functioning of the component tissues. Therefore, epididymal epithelia directly and their secretions indirectly are differentially androgen-dependent.

A porcine homolog of the major secretory protein of human epididymis, HE1, specifically binds cholesterol

A porcine homolog of the major secretory protein of human epididymis, HE1, was for the first time purified from the porcine cauda epididymal fluid. The HE1 homolog was secreted into the epididymal fluid as a 19-kDa glycoprotein, whose sugar moiety was gradually processed to form a 16-kDa protein during transit through the epididymis. The HE1 homolog mRNA was detected only in the caput and corpus epididymis among the porcine tissues examined. The purified HE1 homolog specifically bound cholesterol with high affinity (Kd=2. 3 microM). The binding stoichiometry was determined to be 0.94 mol/mol, suggesting that 1 mol of cholesterol binds to 1 mol of the protein. It was also found that the HE1 homolog is a major cholesterol-binding protein in the porcine epididymal fluid. The possibility that the HE1 homolog is involved in the regulation of the lipid composition of the sperm membranes during the maturation in epididymis is discussed.

Changes in binding of lectins to epididymal, ejaculated, and capacitated spermatozoa of the rhesus monkey

BACKGROUND

The present study was undertaken to evaluate the changes in rhesus monkey sperm surface glycoconjugates during maturation, ejaculation, and capacitation in order to provide background information that would help in evaluating adverse effects, if any, caused by the use of contraceptive agents.

METHODS

Adult sexually mature rhesus monkeys were castrated under ketamine anaesthesia. Percoll purified sperm from different epididymal segments and motile-ejaculated spermatozoa prior to and following in vitro capacitation were exposed to FITC-labeled lectins. Live or sperm prefixed with paraformaldehyde/alcohol were used. Quantitative analysis of changes in lectin binding was done immunoassay.

RESULTS

The majority of live spermatozoa did not show binding of Con A and PNA, whereas uniform labeling of WGA to sperm from corpus epididymidis onward was seen. Unfixed spermatozoa showed marked variation in the pattern of lectin binding. The majority of spermatozoa fixed with paraformaldehyde or alcohol showed maximum lectin labeling over the acrosome, but the postacrosomal area invariably did not bind the lectins. Major changes in the localization of Con A, PNA, or WGA to prefixed spermatozoa were not seen during epididymal transit and in the ejaculate. In capacitated acrosome-reacted spermatozoa, Con A, PNA, and WGA were localized mainly in the equatorial segment. Binding of Con A and PNA was abolished by using lectins preincubated with appropriate inhibitor saccharides. Sperm, exposed to FITC-WGA preincubated with inhibitor sugar, did not show complete inhibition. Quantitative analysis of lectin binding by immunoassay showed increase in binding of lectins during epididymal transit with maximum binding in sperm from the corpus epididymidis.

CONCLUSIONS

The variations in lectin labeling of live spermatozoa could be due to redistribution of sperm surface sugars or membrane damage. The changes in lectin labeling during maturation and capacitation may be associated with their role in ovum recognition and fusion.

Germ cell maturation and cellular associations in the seminiferous epithelial cycle of the chimpanzee

Seminiferous tubule architecture, germ cell maturation steps and cellular associations (stages) of the spermatogenic cycle of the chimpanzee (Pan troglodytes) are resolved. Cross sections of seminiferous tubules usually exhibit 2 to 4 stages, occasionally 1, and rarely 5; stages are not functionally sequential in structurally contiguous regions. The cellular maturation steps are: dark type A stem cell (Ad), pale type A (Ap), type B(B) spermatogonia; resting or preleptotene (P1), leptotene (L), zygotene (Z), pachytene (P), diplotene (Di) primary spermatocytes; meiotic divisions (M1, M2); secondary spermatocytes (2 degrees S); six developmental stages of the spermatid (Sa, Sb1, Sb2, Sc, Sd1, Sd2) composing spermiogenesis. The germ cell maturation steps characteristic of the six cellular associations (stages I-VI) are: Ad, Ap, B, P, Sa, Sd1 (I); Ad, Ap, B, PI, P, Sa, Sd2 (II); Ad, Ap, B, PI, L, P, Sb1 (III); Ad, Ap, PI, L, P, Sb2 (IV); Ad, Ap, L, Z, P, Di, Sc (V); Ad, Ap, B, Z, P, Di, 2 degrees S, Sc (VI). Surgical pressure trauma causes sloughing of some 2 degrees S spermatocytes and some Sa, Sb1, Sb2, Sd1, and Sd2 spermatids, resulting in missing generations, and disrupts Sertoli cell attachments, affecting germ cell development and associations. In structure and function, chimpanzee spermatogenesis appears most similar to the human.

Direct evidence for the elevated synthesis and secretion of procathepsin L in the distal caput epididymis of boar

The proteins which are secreted from the restricted part of the epididymis are suggested to sustain sperm maturation. In porcine species, as the potential abilities of sperm for movement and fertilization greatly increase in the corpus epididymis, the secretions in both the caput and corpus epididymis seem to be very important for the sperm maturation. In this study, we have directed our attention to the 40 kDa protein which is detected in the fluid of the distal caput epididymis of boar. It was purified from the porcine cauda epididymal fluid and its cDNA was cloned from the cDNA library of the distal caput epididymis. According to the deduced amino acid sequence, the 40 kDa protein has been identified as procathepsin L. Northern blot analysis showed that the procathepsin L mRNA was most abundant in the distal caput epididymis among the tissues as examined. Consistent with the distribution of the procathepsin L mRNA in the epididymis, the activity of procathepsin L was absent in the fluid of the proximal and mid caput epididymis and first appeared in the distal caput epididymal fluid, whose contents gradually decreased with the passage through the epididymis. These results first appeared in the first distal caput epididymis expresses very high levels of procathepsin L and unusually secretes it into the luminal fluid instead of targeting it to lysosomes. It has been also found that the mRNA of PDGF, which is known to enhance cathepsin L expression in the culture cells, is very high in the mid caput epididymis, which just precedes the site of procathepsin L secretion. This result indicates that PDGF directly regulates the locally restricted expression and secretion of procathepsin L in the epididymis, which is one of the possible mechanisms involved in the functional differentiation in the epididymis.

Cloning of complementary DNA encoding a 135-kilodalton protein secreted from porcine corpus epididymis and its identification as an epididymis-specific alpha-mannosidase

In the preceding study (Okamura et al., 1992; Biol Reprod 47:1040-1052) we suggested that a 135-kDa protein secreted by porcine epididymis is involved in the sperm maturation. In this work, we have isolated the cDNA clone coding the 135-kDa protein in an effort to investigate its structure and function. The 135-kDa protein was purified from porcine cauda epididymal fluid. Three oligonucleotide probes were synthesized according to the amino acid sequences of N-termini of the native protein and trypsin-digested peptides. A cDNA clone hybridizing with these three probes was isolated from the cDNA library derived from the porcine proximal corpus epididymis. It encodes a novel protein with 1,006 amino acid residues in an open reading frame. Its overall amino acid sequence was significantly homologous (25.7%) to the alpha-mannosidase precursor of Dictiostelium discoideum (P34098). The 135-kDa protein could digest both p-nitro-phenyl-alpha-D-mannoside and high mannose oligo saccharide (Man8-GlcNAc2), strongly suggesting that it is an alpha-mannosidase homologue. The expression of this protein was specific to porcine and was localized to the very narrow parts of epididymis: the border of the caput and corpus epididymis. This protein may serve as a good marker for the functional differentiation in porcine epididymis. A possible role of this protein in the species-specific sperm-egg interaction is discussed.

Protein synthesis and secretion in the human epididymis and immunoreactivity with sperm antibodies

The synthesis and secretion of proteins in the different regions of the human epididymis were studied in vitro. Epididymal tissues obtained from patients undergoing castration for prostatic carcinoma or from cadavers were incubated in the presence of [35S]methionine, and the resulting radiolabeled proteins were analysed on SDS-PAGE. The corpus region was found to be the most active segment in total protein synthesis. Significant qualitative and quantitative changes were observed in the pattern of proteins secreted from the different epididymal regions. To establish those epididymal proteins that interact with maturing sperm, the secreted products were immunoreacted with antibodies raised against a Triton X-100 extract of ejaculated human sperm heads. The antibodies react mainly with the head region of ejaculated spermatozoa as judged by indirect immunofluorescence. Protein A-gold labeling of freeze-fracture images showed gold particle distribution on the sperm plasma membrane. Western blot analysis of the secreted proteins revealed four bands (66, 37, 32, and 29 kDa) in the proximal regions and six additional bands (80, 76, 48, 27, 22, and 17 kDa) in the distal part of the epididymis. Immunoprecipitation of the secreted proteins with these antibodies revealed six radioactive bands of 170, 80, 76, 60, 48, and 37 kDa, which indicates that certain proteins of epididymal origin bind to the sperm plasma membrane.

Movement of cynomolgus and rhesus monkey spermatozoa collected from the lower female reproductive tract

Postcoital (pc) cervical mucus was collected in 73 menstrual cycles of cynomolgus monkeys and in 43 cycles of rhesus monkeys at 2, 6, 10, 30 hr pc. Videomicrography was used to analyze sperm numbers and movement in the mucus. Both cynomolgus and rhesus monkeys had comparable populations of motile sperm in the mucus at 2 hr pc. However, by 6 hr pc, cervical mucus from cynomolgus monkeys contained twice as many total sperm and motile sperm as mucus from rhesus monkeys (P less than .05). Mean swimming speeds of the free-swimming cervical sperm were similar for the two species at this time. No motile sperm were recovered in mucus from rhesus monkeys at 30 hr pc. In cynomolgus monkeys, however, 14 of the 26 animals examined at 30 hr pc had motile sperm in their mucus. These sperm exhibited lower percent motility, percent free-swimming sperm, and swimming speed than those sperm observed at 6 hr pc. Uterine sperm were collected by transcervical or transuterine aspiration from cynomolgus monkeys. In the transcervical technique, sperm were successfully obtained in four of nine animals examined at 6 hr and in four of five animals at 30 hr pc. The percentage of motile sperm in the uterine fluid was high, 82% +/- 4%, and the swimming speeds (86 +/- 2 microns/sec) were higher than those observed in cervical mucus. Approximately 5-10% of the uterine sperm exhibited swimming motions similar to the hyperactivated motility seen in most mammals. These findings indicate that the sperm cervical mucus interaction in vivo in cynomolgus monkeys has more similarities to the human situation than does the interaction in rhesus monkeys.