Susceptibility of sperm chromatin to acid denaturation in situ: a study in endogenous FSH-deprived adult male bonnet monkeys (Macaca radiata)

Acid denaturation of calf thymus DNA in vitro followed by acridine orange (AO) binding induced a 112% increase in the emission of red, a 58% decrease in green, and a consequential decrease in the ratio of green:red fluorescences from 1.7 to 0.9. This metachromatic property of AO on binding to DNA following acid denaturation was utilized to study the susceptibility of normal and ovine follicle-stimulating hormone (oFSH) actively immunized bonnet monkey spermatozoa voided throughout the year. For analyses, the scattergram generated by the emission of red and green fluorescences by 10,000 AO-bound sperm from each semen sample was divided into 4 quadrant zones representing percentage cells fluorescing high green-low red (Q1), high green-high red (Q2), low green-low red (Q3) and low green-high red. (Q4). Normal monkey sperm obtained during the months of July-December exhibited 76, 13, and 11% cells in Q2, Q3, and Q4 quadrants, respectively. However, during January-June, when the females of the species are markedly subfertile, noncycling, and amenorrhoeic, the spermatozoa ejaculated by the male monkeys exhibited 38, 39, and 23% sperm in Q2, Q3, and Q4, respectively, the differences being highly significant (p < .01-.001). FSH deprivation induced significant shifts in fluorescence emissions, from respective controls, with 39, 33, and 28% cells in Q2, Q3, and Q4, respectively, during July-December, and 15, 48, and 37% sperm in Q2, Q3, and Q4 quadrants, respectively, during January-June. It is postulated that the altered kinetics of germ cell transformations and the deficient spermiogenesis observed earlier following FSH deprivation in these monkeys may have induced the enhanced susceptibility to acid denaturation in sperm.

Enhanced susceptibility of follicle-stimulating-hormone-deprived infertile bonnet monkey (Macaca radiata) spermatozoa to dithiothreitol-induced DNA decondensation in situ

Immunoneutralization of endogenous follicle-stimulating hormone (FSH) of adult male monkeys leads to oligospermia and infertility despite unchanged testosterone levels. The inability of these monkeys to impregnate despite repeated exposures to cycling females appeared to be due to abnormal alterations in the kinetics of germ cell transformations and deficient spermiogenesis. Here we investigated the stability of sperm chromatin in oFSH-immunized monkeys as a marker for spermiogenesis. The susceptibility of spermatozoa to in vitro decondensation induced by dithiothreitol (DTT, 0.05-50 mM) was studied by measuring the nuclear fluorescence of DTT-treated, ethidium bromide (EB)-stained sperm using flow cytometry. Changes in sperm morphology and binding of thiol-specific 14C-iodoacetamide (14C-IA) were also monitored under the same conditions. Sperm from the immunized monkeys decondensed at a lower concentration of DTT, bound more EB, and decondensed more extensively than those from control animals. The difference was apparent in sperm from all regions of the epididymis. Immunized monkey sperm also bound significantly more 14C-IA at all concentrations of DTT. Overall, the effective concentration of DTT required to elicit 50% of maximal decondensation (ED50) of epididymal and ejaculated sperm was significantly lower for the immunized monkeys than even the caput sperm of controls. These results suggest that FSH deprivation in monkeys results in production of sperm with limited potential for disulfide formation and reduced chromatin stability.

Susceptibility of human sperm to in situ DNA denaturation is strongly correlated with DNA strand breaks identified by single-cell electrophoresis

Susceptibility of mammalian sperm DNA to low pH- or heat-induced denaturation in situ has shown very strong dose-response relationships with animal and human exposure to chemical and physical toxicants and also fertility potential. In this study, 23 human semen samples representing a wide range in percentage (7-86%) of sperm exhibiting abnormally high susceptibility of DNA in situ to denaturation were studied for the integrity of their DNA using alkaline comet assay (single-cell microgel electrophoresis, pH 10.0). The percentage of comets observed for these samples ranged from 5 to 95%; these data correlated strongly with the percentage of sperm with increased DNA denaturability (r = 0.973; P < 0.001). Labeling of 3' ends of nicked DNA sites with 5-bromo-2'-deoxyuridine 5'-triphosphate (BrdUTP) followed by tagging with FITC-BrdUTP monoclonal antibody and flow cytometry also indicated significantly strong correlations of BrdUTP incorporation with both abnormal susceptibility of DNA to denaturation (r = 0.859, P < 0.001) and comet assay (r = 0.812, P < 0.001). The relationship among susceptibility of sperm chromatin to acid denaturation in situ, BrdUTP incorporation, and formation of comets suggests that DNA fragmentation monitored by these assays may have important physiological relevance in terms of sperm quality and fertility potential.

Identification, isolation, and characterization of a 41-kilodalton protein from rat germ cell-conditioned medium exhibiting concentration-dependent dual biological activities

In this report, we describe the purification of a novel protease with dual biological actions from germ cell-conditioned medium (GCCM) where germ cells were isolated from adult rat testes using a mechanical procedure. Using multiple HPLC columns and two sequential high performance electrophoresis chromatography steps in association with an [125I]-collagen film assay to detect protease activity, a 41-kDa polypeptide (41-kDa-P) was purified to apparent homogeneity from GCCM. Partial N-terminal amino acid sequence analysis of the purified protein revealed a sequence of NH2-KYEFYEIXLL that, when compared with the existing database at Protein Identification Resource (PIR), GenBank, and BLAST revealed that this is a unique protein. The purified protein, when incubated with [125I]-testin, a Sertoli cell secretory product that is localized at the intertesticular cell junction and is resistant to tryptic digest, was found capable of hydrolyzing testin dose dependently. The proteolysis of [125I]-testin by this 41-kDa protein was inhibited by alpha2-macroglobulin (a Sertoli cell secretory product) also in a dose-dependent manner. A study on the interactions between different classes of protease inhibitors and the purified 41-kDa protein revealed that it is a serine protease. At doses ranging between 0.5 and 50 ng/ml, 41-kDa-P induced a dose-dependent inhibition of Sertoli cell secretory function using testin and clusterin as markers without any apparent proteolytic activity. However, at doses greater than 0.5 microg/ml, 41-kDa-P was found to cleave [125I]-collagen and [125I]-testin at physiological pH, indicating that this 41-kDa protein has dual biological activities whose primary action is concentration dependent. In view of the biological activities of this protease, it is postulated that this protein may be involved in facilitating germ cell migration in the epithelium.

Differential expression of multiple cathepsin mRNAs in the rat testis during maturation and following lonidamine induced tissue restructuring

In the seminiferous epithelium, germ cell development behind the blood-testis barrier involves continual degradation and renewal of inter-testicular cell junctions. This allows: (i) the translocation of developing germ cells from the basal lamina to the adluminal compartment during spermatogenesis, and (ii) the eventual release of mature spermatids into the tubular lumen during spermiation. Throughout spermatogenesis, cellular debris must also be removed from the epithelium Thus, it is conceivable that proteases, protease inhibitors, and cell junctional components are involved in these events. The present study sought to examine whether testicular cells can express multiple cathepsin mRNAs given that these proteases are involved in the degradation and processing of proteins as well as in tissue regeneration. By using total RNA isolated from primary cultures of Sertoli, Leydig, and germ cells for reverse-transcription and polymerase chain reaction (RT-PCR), the mRNAs of cathepsin B, C, D, H, L, and S were shown to be expressed by Sertoli and Leydig cells, whereas germ cells isolated from adult rats expressed all of the above cathepsin mRNAs except cathepsin D. Throughout postnatal development and maturation, the testicular steady-state mRNA levels of cathepsin B, C, D, L, and S remain relatively unchanged with the exception of cathepsin H whose mRNA level increased during maturation and peaked at 45-60 days of age. Using lonidamine, an anti-spermatogenic drug which is known to induce premature release of germ cells without affecting Leydig cell function by disrupting the inter-Sertoli-germ cell junctions, we have examined the differential expression of these cathepsin mRNAs in the testis at the time of extensive tissue restructuring. It was noted that the expression of cathepsin L and S in the testis increased significantly concomitant with the disappearance of elongate spermatids whereas the expression of cathepsin B, C, D, and H increased significantly when most of the round spermatids and spermatocytes were depleted. These results illustrate the intricate inter-relationship between these proteases in the testis during maturation and tissue restructuring.

Ability of trypsin in mimicking germ cell factors that affect Sertoli cell secretory function

A biological factor that inhibits the in vitro secretion of testin by Sertoli cells was purified to apparent homogeneity from conditioned medium of germ cells isolated using trypsin. Partial N-terminal amino acid sequence analysis of the purified germ cell factor revealed a sequence of NH2-IVGGYTXAAN. Comparison of the sequence with the existing protein database revealed that it is homologous to trypsin. Immunoprecipitation experiments using either [35S]-labeled germ or Sertoli cell proteins and a monospecific anti-trypsin antibody failed to demonstrate the synthesis and secretion of trypsin by these testicular cells, suggesting the isolated factor is the residuary trypsin that was used for isolating germ cells from seminiferous tubules. Subsequent experiments revealed that trypsin per se can inhibit the secretion of Sertoli cell testin and clusterin dose-dependently, whose effect can be prohibited by soybean trypsin inhibitor (STI). In view of these findings, a nonenzymatic procedure was deemed necessary to prepare germ cell conditioned medium (GCCM) to assess whether an authentic biological factor(s) is indeed present. Four batches of conditioned medium of germ cells isolated by a mechanical procedure without the use of trypsin were fractionated by sequential Mono Q anion exchange and C8 reversed-phase HPLC. When these fractions were monitored for testin modulatory activity using an in vitro bioassay with primary cultures of Sertoli cells, it was shown that GCCM prepared by this procedure indeed contained testin modulatory bioactivity. Since testin is a novel component of specialized junctions between Sertoli and germ cells, the identification of a germ cell factor(s) that affects its secretion by Sertoli cells suggests a dynamic biochemical relationship between these cell types in the seminiferous epithelium.

Rat epididymal sperm exhibit on dithiothreitol treatment in vitro quantifiable differences in patterns of light scatter, uptake of 14C-iodoacetamide and binding of ethidium bromide to DNA

The extent to which chromatin of rat caput (CAP), corpus (COR), cauda (CAU) spermatozoa undergo condensation and compaction is known to be a function of progressive increase in the formation of inter- as well as intra-protamine disulphide bridges during their transit through the epididymis. Relative compaction undergone by the nuclear chromatin of these sperm populations was studied by monitoring their susceptibility to in vitro decondensation induced by varying concentrations (0, 0.01, 1, 5, 10, 50 mM) of disulphide reducing agent, dithiothreitol (DTT) after an initial exposure to 0.01% papain. Following this treatment and staining with the nucleic acid specific fluorochrome, ethidium bromide (EB), it was observed that irrespective of the epididymal region from which they were collected, spermatozoa exhibited DTT dose-dependent (a) increase in nuclear size as seen under fluorescence microscopic examination, (b) decrease in flow cytometrically quantifiable light scatter parameters--forward scatter (FSc, 'nuclear size') and side scatter (SSc, nuclear 'granularity'), (c) increase in individual cell EB binding when analyzed by DNA flow cytometry, and (d) increase in thiol specific 14C-iodoacetamide (14C-IA) uptake. The decrease in both FSc and SSc occurring in spite of actual increase in nuclear size has been attributed to increase in translucency of spermatozoan nuclei consequent to decondensation. The FSc, SSc and EB bindability were studied by monitoring both the channels of maximal cell concentration detected in the flow cytograms as well as by digitally quantitating the numbers of cells within specific channels (1-64, 65-128, 129-192 and 193-256) of the flow cytogram. The latter indicated a measure of the variability in the response of populations of sperm within each sample to DTT induced decondensation. At any given concentration of DTT, especially between 5-10 mM, the differences observed between sperms of different regions were consistent and significant (P < 0.01-P < 0.001), maximal changes being shown by CAP and minimal by CAU sperm, COR sperm appearing in between. The effective concentration of DTT required to elicit 50% of maximal (i.e. that exhibited by CAP sperm when taken as 100%) effect (ED50) varied significantly among CAP, COR and CAU sperms for each of the parameters studied (P < 0.01-P < 0.001). It is concluded that the differences observed among the three epididymal sperm populations are due to differences in the extent of susceptibility to decondensation in vitro and that this is dependent upon the variation in the -S-S-content of their chromatin during different stages of epididymal transit. All the parameters used (with the exception of fluorescence microscopy) can be quantified and as all of them show a similar dose dependency to DTT treatment, any one of these parameters can be conveniently used to determine the mature/immature status of the sperms voided. Application of such a method to determine the quality of sperms voided by man appears feasible.

Cyclic and postnatal developmental changes of testin in the rat seminiferous epithelium--an immunohistochemical study

Testin is an authentic Sertoli cell secretory protein consisting of two molecular variants designated testin I (M(r) 35 000) and testin II (M(r) 37 000). N-Terminal amino acid sequence analysis revealed that testin I is identical to testin II except that testin II has three extra N-terminal amino acids of threonine-alanine-proline (TAP). Earlier studies by immunoflorescence microscopy have shown that testin is detected in the seminiferous epithelium consistent with localization in the junctions between Sertoli cells as well as Sertoli-germ cells, and that it appears to be a component of junctional complexes in the testis. In the present study, we have examined the localization of testin in different stages of the spermatogenic cycle of the adult rat testis when germ cells migrate from the basal portion of the seminiferous epithelium to the tubular lumen. In stages I-IV, testin was localized mainly in the basement laminae in the junctional complexes between adjacent Sertoli cells as well as between Sertoli cells, spermatogonia, and pachytene spermatocytes. When elongated spermatids were embedded into the seminiferous epithelium in stage VII of the cycle, testin was detected predominantly on the concave side of the elongated spermatids, but relatively few testin reaction products were seen in the round spermatids. In the beginning of stage VIII of the spermatogenic cycle, intense testin immunoreactive substances were detected around the heads of the elongated spermatids; these substances were virtually undetectable in late stage VIII after the release of the mature sperm into the tubular lumen, suggesting that testin may be a novel marker to divide stage VIII into stages VIIIa and VIIIb.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemiorchidectomy leads to dramatic and immediate alterations in pituitary follicle-stimulating hormone secretion and the functional activity of the remaining testis in the adult male bonnet monkey (Macaca radiata)

The aim of the present study was to examine the effect of hemiorchidectomy (HO) on serum FSH, LH, testosterone (T), and inhibin (INH) concentrations as well as on the testicular volume (TV) and on changes in the kinetics of germ cell turnovers in the remaining testis of adult male bonnet monkeys. Blood samples collected at 2200 h at various times before and after HO and testicular biopsies obtained at different periods were subjected to hormone analysis and DNA flow cytometry. Though serum T levels were lowered (p < 0.05) at 12 h after HO, T levels rapidly returned to intact control concentrations by Day 5. While serum LH remained unaltered, serum FSH increased markedly within 2 days of HO and remained significantly (p < 0.05) elevated over the next 90 days. Though serum INH showed a significant decrease (p < 0.05) by 15 min of HO, it returned to approximately 80% of intact levels within one week. The TV of the remaining testis showed maximal increment by Day 30 (p < 0.05) of HO. DNA flow cytometric analysis 24 days after HO showed increases (p < 0.05) in spermatogonia (2C) and primary spermatocytes (4C). These cell types by Day 45 had transformed to round (1C) and elongate (HC) (by 38%, p < 0.001) spermatids. Overall spermatogenesis (conversion of 2C to 1C and HC) showed significant enhancement at Days 110 and 175, suggesting that the spurt in spermatogenic activity is not confined to a single spermatogenic cycle.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of altering endogenous gonadotrophin concentrations on the kinetics of testicular germ cell turnover in the bonnet monkey (Macaca radiata)

The role of FSH and diurnal testosterone rhythms in specific germ cell transformations during spermatogenesis were investigated using DNA flow cytometry and morphometry of the seminiferous epithelium of the adult male bonnet monkey (Macaca radiata), the endogenous hormone levels of which were altered by two different protocols. (1) Active immunization of five monkeys for 290 days using ovine FSH adsorbed on Alhydrogel resulted in the neutralization of endogenous FSH, leaving the LH and diurnal testosterone rhythms normal. (2) Desensitization of the pituitary gonadotrophs of ten monkeys by chronically infusing gonadotrophin-releasing hormone analogue, buserelin (50 micrograms/day release rate), via an Alzet pump implant (s.c.) led to a 60-80% reduction in LH and FSH as well as total abolition of testosterone rhythms. The basal testosterone level (3.3 +/- 2.0 micrograms/l), however, was maintained in this group by way of an s.c. testosterone silicone elastomer implant. Both of the treatments caused significant (P < 0.01) nearly identical reduction in testicular biopsy scores, mitotic indices and daily sperm production rates compared with respective controls. The germ cell DNA flow cytometric profiles of the two treatment groups, however, were fundamentally different from each other. The pituitary-desensitized group exhibited a significant (P < 0.001) increase in 2C (spermatogonial) and decrease in 1C (round spermatid) populations while S-phase (preleptotene spermatocytes) and 4C (primary spermatocytes) populations were normal, indicating an arrest in meiosis caused presumably by the lack of increment in nocturnal serum testosterone. In contrast, in the FSH-immunized group, at day 80 when the FSH deprivation was total, the primary block appeared to be at the conversion of spermatogonia (2C) to cells in S-phase and primary spermatocytes (4C reduced by > 90%). In addition, at this time, although the round spermatid (1C) population was reduced by 65% (P < 0.01) the elongate spermatid (HC) population showed an increase of 52% (P < 0.05). This, taken together with the fact that sperm output in the ejaculate is reduced by 80%, suggests a blockade in spermiogenesis and spermiation. Administration of booster injections of oFSH at time-points at which the antibody titre was markedly low (at days 84 and 180) resulted in a transient resurgence in spermatogenesis (at day 180 and 228), and this again was blocked by day 290 when the FSH antibody titre increased.(ABSTRACT TRUNCATED AT 400 WORDS)

Long-term contraceptive efficacy of vaccine of ovine follicle-stimulating hormone in male bonnet monkeys (Macaca radiata)

A group of ten healthy fertile adult male bonnet monkeys were actively immunized using procedures acceptable for human use with pure follicle-stimulating hormone (oFSH) isolated from sheep pituitaries. The vaccine elicited an immunogenic response in all ten monkeys; the antibody-binding capacity, determined by Scatchard analysis, varied from 3 to 18 micrograms oFSH ml-1, the binding affinity ranging from 0.13 to 2.0 x 10(10) mol-1. A substantial population of antibodies against oFSH crossreacted with 125I-labelled human (h) FSH, used here as a representative ligand of primate FSH. The bioneutralization activity of the antisera assessed by a specific bioassay in vitro, when the antibody titre was high, was 6.9 +/- 0.18 micrograms hFSH ml-1. Immunization for 4.7-5.7 years did not affect the health and libido of the animals. Concentration of testosterone in serum remained normal throughout the study, but, within 150 days of immunization, there was a marked decrease (75-100%) in the number of spermatozoa in seminal ejaculates. Oligospermic status interspersed with azoospermia was maintained by periodic boosting. The fertility of these animals was monitored between 6 months and 2 years after primary immunization. All the ten animals proved infertile in repeated mating experiments with females of proven fertility. After stopping booster injections, nine of ten animals regained fertility, but the time taken for this depended upon the rate of decline of antibody titres. Re-boosting these monkeys with 100 micrograms oFSH after confirming that recovery had occurred revealed prompt increases in antibody titres followed once again by onset of oligo-azoospermia and infertility, underscoring the specificity of immunization effect. The immunized monkeys, apart from being acutely oligospermic, ejaculated spermatozoa that were markedly deficient in key acrosomal enzymes, such as acrosin and hyaluronidase, and motility as well as in their ability to penetrate a gel in vitro, suggesting that the infertility observed was due to gross reductions in the numbers of spermatozoa that could effectively interact with the oocyte and cause successful fertilization.

DNA flow-cytometric analysis of testicular germ cell populations of the bonnet monkey (Macaca radiata) as a function of sexual maturity

Testicular germ cell populations of biopsies from 32 male bonnet monkeys in 5 different age groups were quantitated in a flow cytometer after labelling of germ cell DNA with the specific fluorochrome, 4,6-diamidino phenyl indole. The 5 quantifiable populations were spermatogonia (2C), preleptotene spermatocytes (S phase), primary spermatocytes (4C), round spermatids (1C) and elongate spermatids (HC). The seminiferous tubules of immature 3-4-year-old monkey had only Sertoli cells and spermatogonia (2C). At 5-6 years, germ cells in S-phase (9.5%), 4C (11.1%), 1C (41.8%) and HC (17.1%) stages of maturation appeared for the first time but at 7-8 years of age and beyond all cell types except HC decreased while 1C remained relatively constant. Histometric analysis correlated well with the flow-cytometric data. The decrease in cells of 2C, S-phase and 4C stages was associated with an increase in mitotic index, signifying acceleration in the kinetics of germ cell transformation into subsequent cell types. The total turnover in cell transformation (1C:2C) was significantly (P less than 0.01) increased at and beyond 7-8 years. Maximum transition from 2C to 4C occurred at 5-6 years (4C:2C ratio 0.8 at 5-6 years and 0.6 at 7-8 years). The ratio HC:1C (kinetics of cell transformation during spermiogenesis) attained near total efficiency only by 10 years of age (1.08 at 10-14 years; 0.9 at 18-20 years). Also, the cell associations within the seminiferous tubules of monkeys greater than or equal to 10 years of age were better defined than those of younger animals. The changes in germ cell ratios correlated well with alterations in testicular volume, sperm numbers in the ejaculate and surges of testosterone and increments in FSH in the serum, characteristic of development of sexual maturity. It is apparent from this study that DNA flow cytometry of testicular germ cell populations reveals subtle changes in spermatogenic status of bonnet monkeys with a high degree of sensitivity.