Acute, whole-body microwave exposure and testicular function of rats

Male Sprague-Dawley rats were exposed for 8 h to continuous-wave microwave radiation (MWR, 1.3 Ghz) at a mean specific absorbed dose rate of 9 mW/g. MWR exposure and sham-irradiation took place in unidirectionally energized cylindrical waveguide sections, within which the animals were essentially unrestrained. The MWR treatment in this setting was determined to yield an elevation of deep rectal temperature to 4.5 degrees C. The animals were taken for analysis at 6.5, 13, 26, and 52 days following treatment, which corresponded to .5, 1, 2, and 4 cycles of the seminiferous epithelium. Net mass of testes, epididymides, and seminal vesicles; daily sperm production (DSP) per testis and per gram of testis; and the number of epididymal sperm were determined. The levels of circulating follicle-stimulating hormone (FSH) and leutinizing hormone (LH) were derived via radioimmunoassay of plasma samples taken at the time of sacrifice. Despite the evident acute thermogenesis of the MWR at 9 mW/g, no substantial decrement in testicular function was found. We conclude that, in the unrestrained rat, whole body irradiation at 9 mW/g, while sufficient to induce evident hyperthermia, is not a sufficient condition for disruption of any of these key measures of testicular function.     

Determination of daily sperm production in stallion testes by enumeration of germ cells in homogenates

Thirty adult stallion testes were selected with high (n = 15) and low (n = 15) Daily Sperm Production (DSP)/testis. Parenchymal samples were prepared for morphometric analysis, and the numbers of germ cells and Sertoli cells were determined. Testicular samples were homogenized, and germ cells and Sertoli cells were enumerated using phase contrast microscopy. Numbers of germ cells and Sertoli cells and potential DSP during spermatogenesis were determined. Significant correlations existed between morphometric and homogenate determinations of number per testis of preleptotene, leptotene plus zygotene primary spermatocytes (r = 0.58; P < 0.001), pachytene plus diplotene primary spermatocytes (r = 0.67; P < 0.0001), all primary spermatocytes (r = 0.67; P < 0.0001), round spermatids (r = 0.72; P < 0.0001), and Sertoli cells (r = 0.70; P < 0.0001). Significant correlations (P < 0.0001) existed between morphometric and homogenate determination of DSP/testis based on preleptotene, leptotene plus zygotene primary spermatocytes (r = 0.78), pachytene plus diplotene primary spermatocytes (r = 0.88), and round spermatids (r = 0.85). Using morphometric determination as the standard, the sensitivity (i.e., ability to detect low DSP/testis) and specificity (i.e., ability to detect high DSP/testis) by homogenate enumeration of germ cells was 81 and 93% for round spermatids, 100 and 24% for pachytene plus diplotene primary spermatocytes, and 67 and 87% for preleptotene, leptotene plus zygotene primary spermatocytes, respectively. Enumeration of primary spermatocytes in homogenates was less accurate than enumeration of round or elongated spermatids. Enumeration of round and elongated spermatids in homogenates was a rapid and useful method for determining DSP in horses, and it may prove to be a useful technique for quantitating potential DSP from testicular biopsies.     

Missing generations of spermatocytes and spermatids in seminiferous epithelium contribute to low efficiency of spermatogenesis in humans.

Daily sperm production per gram parenchyma (DSP/g) in humans is only 25 or 35% of that for most species including rats and nonhuman primates. To explain the low efficiency of spermatogenesis in humans, the number of generations of germ cells (spermatocytes and spermatids) and the number of these germ cells in each generation were determined for each spermatogenic stage in men with varied efficiencies. Testes were obtained at autopsy, fixed by vascular perfusion with glutaraldehyde, further fixed in osmium, and embedded in Epon 812 before 0.5-micron sections were stained with toluidine blue. Tubular cross sections were photographed, and spermatogenic stages were determined by two observers. Testes were divided into three groups on the basis of DSP/g. The number of generations of spermatocytes and spermatids was greater (p < 0.05) in the high (2.01 +/- 0.05) and intermediate (1.77 +/- 0.04) than in the low (1.45 +/- 0.15) DSP/g group. All groups had a lower number of generations of spermatocytes and spermatids compared to the optimum value of three. The number of these generations per cross section was related (r = 0.85; p < 0.01) to DSP/g in these men. The number per cross section of spermatocytes, spermatids, and the combined number of germ cells was higher (p < 0.01) in the high than in the low DSP/g group. The combined number of germ cells per cross section was related (r = 0.85; p < 0.01) to DSP/g. The combined number of germ cells was higher in the high versus the low DSP/g group in stages I through V, but this difference was significant only in stages IV and V.(ABSTRACT TRUNCATED AT 250 WORDS)     

Atropine, diazepam, and physostigmine: thermoregulatory effects in the heat-stressed rat

We have previously reported that administration of atropine (A) to unrestrained, sedentary, heat-stressed rats resulted in a dose-dependent increase in heating rate (rate of rise of core temperature, degree C/min). Additionally, we have demonstrated that the decrements in treadmill endurance and increments in heating rate of physostigmine (PH)-treated running rats can both be restored to control levels by pretreating the animals with A and diazepam (D). Our objective in the present work was to determine if the administration of D + PH to A-treated unrestrained, sedentary, heat-stressed rats (N = 16/group, 510-530 g) could improve their thermal tolerance. The following drugs were administered singly (at 10 min intervals) via lateral tail vein: vehicle-control (C), A (200 micrograms/kg), D (500 micrograms/kg), and PH (200 micrograms/kg). After drug administration, the rats were heat-stressed (Tamb = 41.5 degrees C) until a core temperature of 42.6 degrees C was attained when they were removed to a 26 degrees C chamber. The heating rates (degrees C/min) and tolerance times (min) of the respective groups were: C- 0.02, 235; A- 0.08, 58; A D- 0.06, 94; and A + D + PH- 0.04, 143. Administration of D with A significantly decreased heating rate, and D + PH more than doubled the thermal tolerance of A-treated rats. Thus, the combination of A + D + PH not only restores PH-induced performance and thermoregulatory decrements of rats exercised in a moderate environment, but also reduces A-induced heat intolerance.     

Low temperature promotes annexin V expression in newt testis

We examined the effect of low temperatures on annexin V expression in newt testis. When newts were transferred to a low temperature (12 degrees C), up-regulation of annexin V protein was observed in secondary spermatogonia. In primary spermatocytes, high levels of annexin V expression were observed at both 12 degrees C and 22 degrees C, but at 12 degrees C the protein was localized in part of the cytoplasm of primary spermatocytes. These results indicate that in newt testis annexin V is a cold-sensitive protein, suggesting the possibility that annexin V might have a cold stress-related function in newt germ cells.     

Prolonged microwave irradiation of rats: Effects on concurrent operant behavior

Two measures of performance were used to study the effects of pulse-modulated microwave radiation (PM MWR) on schedule-controlled operant behavior of rats: 1) cued (S^D), fixed-ratio (FR) bar pressing for food reinforcement; and 2) noncued (S^d) bar pressing in the absence of food reinforcement. The animals were irradiated and the behavioral data were obtained concurrently, during daily three-hour sessions, five days per week for six to nine weeks. Each experiment began with a two to three-week baseline interval of sham irradiation; a two to three-week interval of sham irradiation followed the irradiation phase. The irradiated animals were exposed to 1.3-Ghz PM MWR (pulse width of 1 microsecond at 600 pulses per second) at whole-body, average specific absorbed-dose rates of from 1.5–6.7 mW/g. Control and irradiated animals were tested in identical, cylindrical waveguide exposure/behavioral assemblies; different groups of irradiated and sham-irradiated animals were used for each dose rate. At 1.5 mW/g, the levels of S^D operant responding by control and irradiated animals were comparable, and showed similar progressive diminutions over the course of each daily session. S^d operant responding was more variable, but again comparable, with both groups showing similar, progressive declines in rate of responding during each session. At 3.6 mW/g, no specific effects on S^D operant response rates were observed. However, there was an initial and transient increase in the rate of extinction of S^d responding. At 6.7 mW/g, S^D response rates were slightly reduced, whereas there was a major reduction in noncued (S^d) operant responding followed by a sharp rebound during the first post-MWR week. This marked reduction in S^d operant responding at MWR onset was in contrast to the relative stability and persistence of FR responding for food reinforcement.     

Quantification of human spermatogenesis: germ cell degeneration during spermatocytogenesis and meiosis in testes from younger and older adult men

Germ cell degeneration during spermatocytogenesis and meiosis was investigated to explain the age-related decline in daily sperm production (DSP). Numbers of Types A-dark, A-pale, and B-spermatogonia, potential daily sperm production per g parenchyma (PDSP) based on type B-spermatogonia, early primary spermatocytes, and late primary spermatocytes, and DSP per g based on early spermatids were determined in 15 men aged 20 to 48 yr (mean +/- SEM, 33 +/- 2 yr) and 15 men aged 52 to 90 yr (65 +/- 3 yr). Testes obtained within 15 h of death (largely due to trauma or heart failure) were perfused vascularly with glutaraldehyde. The number of each cell type per g parenchyma was calculated as the product of the percentage of nuclei in the parenchyma times a correction factor for section thickness and nuclear diameter divided by the volume of a single nucleus of that cell type. Paired testicular weight was lower (p less than 0.01) in older men (33 +/- 3 g) than in the younger men (49 +/- 3 g). Younger and older men had similar numbers of A-dark, A-pale, and B-spermatogonia per g parenchyma. PDSP based on late primary spermatocytes and DSP based on early spermatids were lower (p less than 0.01) in older men than in younger men. In younger men, PDSP was similar (p greater than 0.05) between B-spermatogonia and late primary spermatocytes, whereas DSP measured at the spermatid level was abruptly lower than that estimated from younger cell types. Older men showed reduction in PDSP between early and late primary spermatocytes, with further reduction occurring in DSP at the spermatid level.(ABSTRACT TRUNCATED AT 250 WORDS)     

FSH-initiated differentiation of newt spermatogonia to primary spermatocytes in germ-somatic cell reaggregates cultured within a collagen matrix

We previously cultured fragments of newt testes in chemically defined media and showed that mammalian follicle-stimulating hormone (FSH) stimulates proliferation of spermatogonia as well as their differentiation into primary spermatocytes (Ji et al., 1992; Abe and Ji, 1994). Next, we indicated in cultures composed of spermatogonia and somatic cells (mainly Sertoli cells) that FSH stimulates germ cell proliferation via Sertoli cells (Maekawa et al., 1995). However, the spermatogonia did not differentiate into primary spermatocytes, but instead died. In the present study, we embedded large reaggregates of spermatogonia and somatic cells (mainly Sertoli cells) within a collagen matrix and cultured the reaggregates on a filter that floated on chemically defined media containing FSH; in this revised culture system, spermatogonia proliferated and differentiated into primary spermatocytes. The viability and percentage of germ cells differentiating into primary spermatocytes were proportional to the percentage of somatic cells in the culture, indicating that differentiation of spermatogonia into primary spermatocytes is mediated by Sertoli cells.     

Quantitation of spermatogenesis by DNA flow cytometry: Comparative study among six species of mammals

Suspensions of testicular germ cells from six species of mammals were prepared and stained for the DNA content with a fluorochrome (ethidium bromide) adopting a common technique and subjected to DNA flow cytometry. While uniform staining of the germ cells of the mouse, hamster, rat and monkey could be obtained by treating with 0.5% pepsin for 60 min followed by staining with ethidium bromide for 30 min, that of the guinea pig and rabbit required for optimal staining pepsinization for 90 min and treatment with ethidium bromide for 60 min. The procedure adopted here provided a uniform recovery of over 80% of germ cells with each one of the species tested and the cell population distributed itself according to the DNA content (expressed as C values) into 5 major classes-spermatogonia (2C), cells in S-phase, primary spermatocytes (4C), round spermatids (1C), and elongating/elongated spermatids (HC). Comparison of the DNA distribution pattern of the germ cell populations between species revealed little variation in the relative quantities of cells with 2C (8–11%), S-phase (6–9%), and 4C (6–9%) amount of DNA. Though the spermatid cell populations exhibited variations (1C:31–46%, HCl:7–20% and and HC2:11–25%) they represented the bulk of germ cells (70–80%). The overall conversion of 2C to 1C (1C:2C ratio) and meiotic transformation of 4C cells to 1C (1C:4C ratio) kinetics were relatively constant between the species studied. The present study clearly demonstrates that DNA flow cytometry can be adopted with ease and assurance to quantify germ cell transformation and as such spermatogenesis by analysing a large number of samples with consistency both within and across the species barrier. Any variation from the norms in germ cell proportions observed following treatment, fore.g. hormonal stimulation or deprivation can then be ascribed due to a specific effect of the hormone/drug on single/multiple steps in germ cell transformation     

Differentiation of Primary Spermatocytes to Elongated Spermatids by Mammalian FSH in Organ Culture of Testes Fragments from the Newt, Cynops pyrrhogaster

Our previous studies (10, 11) showed that mammalian follicle-stimulating hormone (FSH) alone was indispensable and sufficient for the initiation and promotion of spermatogenesis from secondary spermatogonia to primary spermatocytes in organ culture of testes fragments from the newt, Cynops pyrrhogaster. The present study demonstrated that FSH promoted in the same model system the differentiation of primary spermatocytes even further: to the stage of elongated spermatids. When testes fragments, consisting of somatic cells and germ cells (mostly primary spermatocytes), were cultured in a control medium for three weeks, only round spermatids and spermatogonia were observed; both the diameter of the cysts and the viability of the germ cells decreased to about 10–15% of the original level. On the other hand, when the medium was supplemented with FSH, elongated spermatids appeared by the second week; both the diameter of the cysts and the viability of the germ cells were maintained at a higher level than in the control medium. The effect of FSH was dose-dependent. However, neither transferrin, androgens (testosterone and 5α-dihydrotestosterone) nor luteinizing hormone (LH) was effective. The addition of cyanoketone, a specific inhibitor of 3β-hydroxy-Δ⁵-steroid dehydrogenase (3β-HSD) (32), to the FSH-containing medium did not prevent the differentiation promoted by FSH, indicating that it is unlikely that Δ⁴-steroid metabolites produced in fragments by FSH acted directly on germ cells. Insulin was found to improve the viability of germ cells during a 2 week of culture period. In the presence of FSH, the cells in various differentiative stages had morphological characteristics very similar to those in vivo, whereas in the absence of FSH primary spermatocytes showed abnormal features in their nuclei and cytoplasm, indicating that they were deteriorating. These results and our previous results (1–3) suggest that FSH promotes primary spermatocytes to differentiate into elongated spermatids probably by stimulating Sertoli cells to secrete factors which then act on the germ cells.     

Increased daily sperm production in the breeding season of stallions is explained by an elevated population of spermatogonia

Seasonal variation in number of spermatogonia and germ cell degeneration was evaluated to determine which mechanism might explain seasonal differences in daily sperm production per testis (DSP/testis) or per g parenchyma (DSP/g) in stallions. Comparing 28 adult stallions (4 to 20 yr old) in each of the nonbreeding (December-January) and breeding (June-July) seasons, the population of type A spermatogonia was more than two times greater (P less than 0.01) in the breeding season. While the number of type B spermatogonia also was elevated (P less than 0.01) in the breeding season, the number of type B spermatogonia/type A spermatogonium was similar (P greater than 0.05) between seasons. Daily sperm production/testis based on each cell type from type B spermatogonia to spermatids with elongated nuclei was lower (P less than 0.01) in the nonbreeding season. Based on DSP/g, there was significant degeneration during the meiotic divisions in the nonbreeding season. However, this reduction in potential spermatozoan production was not significant (P greater than 0.05) when considering DSP/testis. Significant germ cell degeneration also occurred in the breeding season between type B spermatogonia and primary spermatocytes. However, the type A spermatogonial population was sufficiently elevated to override this degeneration and to explain elevated production of sperm in the breeding season of stallions.     

Heat resistance and mechanism of heat inactivation in thermophilic campylobacters

The heat resistance of Campylobacter jejuni strains AR6 and L51 and the heat resistance of Campylobacter coli strains DR4 and L6 were measured over the temperature range from 50 to 60 degrees C by two methods. Isothermal measurements yielded D55 values in the range from 4.6 to 6.6 min and z values in the range from 5.5 to 6.3 degrees C. Dynamic measurements using differential scanning calorimetry (DSC) during heating at a rate of 10 degrees C/min yielded D55 values of 2.5 min and 3.4 min and z values of 6.3 degrees C and 6.5 degrees C for AR6 and DR4, respectively. Both dynamic and isothermal methods yielded mean D55 values that were substantially greater than those reported previously (0.75 to 0.95 min). DSC analysis of each strain during heating at a rate of 10 degrees C/min yielded a complex series of overlapping endothermic peaks, which were assigned to cell wall lipids, ribosomes, and DNA. Measurement of the decline in the numbers of CFU in calorimetric samples as they were heated showed that the maximum rate of cell death occurred at 56 to 57 degrees C, which is close to the value predicted mathematically from the isothermal measurements of D and z (61 degrees C). Both estimates were very close to the peak m1 values, 60 to 62 degrees C, which were tentatively identified with unfolding of the 30S ribosome subunit, showing that cell death in C. jejuni and C. coli coincided with unfolding of the most thermally labile regions of the ribosome. Other measurements indicated that several essential proteins, including the alpha and beta subunits of RNA polymerase, might also unfold at the same time and contribute to cell death.     

Possible involvement of germ cells in the regulation of oestradiol-17 beta and ABP secretion by immature rat Sertoli cells (in vitro studies)

The effects of germ cells prepared from adult rats and of media conditioned by some of these germ cells have been studied in vitro on both ABP and oestradiol-17 beta secretion by immature rat Sertoli cells. Addition of the germ cells to the Sertoli cell cultures resulted in both a dose-dependent increase of ABP secretion and a dose-dependent inhibition of oestradiol production. These effects were suppressed after removal of germ cells by hypotonic treatment. Furthermore, spent media of highly viable germ cells (SMGC), but not spent media of an epithelial cell line, mimicked the effects of germ cells themselves on ABP and oestradiol levels after FSH or dbcAMP stimulation. These effects were reversible when SMGC were replaced by fresh media and did not result from a change in the conversion of oestradiol to oestrone. SMGC effects were unaltered by heating at 60 degrees C for 30 min, by freezing and thawing and non dialysable (MW greater than 10,000). However, heating at 100 degrees C for 3 min and treatment by trypsin, suppressed the SMGC effects. This indicates that the stimulation of ABP and inhibition of oestradiol levels by germ cells, in vitro, could be mediated by factor(s) of proteinaceous nature.     

Cytogenetic observations on XX/XY chimaeras and a reassessement of the evidence for germ cell chimaerism in heterosexual twin cattle and marmosets.

Testicular preparations were obtained from 7 bulls, twins of freemartins, and 1 male marmoset, all proved XX/XY chimaeras. X and Y sex chromosomes were confidently identified in nearly all the 87 spermatogonia at mitotic metaphase and 1052 primary spermatocytes at diakinesis-metaphase examined: no cell was identified as containing two X chromosomes. The germ cell chimaerism previously reported in these species is therefore not confirmed. Cultures grown from presumptive somatic these species is therefore not confirmed. Cultures grown from presumptive somatic cells in the testes of two of the bulls yielded 248 identifiable mitotic spreads, all XY-type; cultures from the gonads of their freemartin twins yielded 442 mitotic spreads, all XX-type. Direct preparations from one freemartin gonad, however, yielded 3 XY mitotic spreads out of 18 examined. The conflicting evidence concerning germ cell chimaerism in cattle and marmosets is discussed, particularly in relation to reports of XX/XY bulls that have sired a great excess of daughters. The possibility that XX germ cells contributed to the functional spermatozoa of these bulls is not favoured by present information, but is not excluded.     

Alterations in pulmonary surfactant after rapid arousal from torpor in the marsupial Sminthopsis crassicaudata.

Torpor in the dunnart, Sminthopsis crassicaudata, alters surfactant lipid composition and surface activity. Here we investigated changes in surfactant composition and surface activity over 1 h after rapid arousal from torpor (15-30 degrees C at 1 degrees C/min). We measured total phospholipid (PL), disaturated PL (DSP), and cholesterol (Chol) content of surfactant lavage and surface activity (measured at both 15 and 37 degrees C in the captive bubble surfactometer). Immediately after arousal, Chol decreased (from 4.1 +/- 0.05 to 2.8 +/- 0.3 mg/g dry lung) and reached warm-active levels by 60 min after arousal. The Chol/DSP and Chol/PL ratios both decreased to warm-active levels 5 min after arousal because PL, DSP, and the DSP/PL ratio remained elevated over the 60 min after arousal. Minimal surface tension and film compressibility at 17 mN/m at 37 degrees C both decreased 5 min after arousal, correlating with rapid changes in surfactant Chol. Therefore, changes in lipids matched changes in surface activity during the postarousal period.     

Effects of microwave exposure on the hamster immune system. II. Peritoneal macrophage function

Acute exposure to hamsters to microwave energy (2.45 GHz; 25 mW/cm2 for 60 min) resulted in activation of peritoneal macrophages that were significantly more viricidal to vaccinia virus as compared to sham-exposed or normal (minimum-handling) controls. Macrophages from microwave-exposed hamsters became activated as early as 6 h after exposure and remained activated for up to 12 days. The activation of macrophages by microwave exposure paralleled the macrophage activation after vaccinia virus immunization. Activated macrophages from vaccinia-immunized hamsters did not differ in their viricidal activity when the hamsters were microwave- or sham-exposed. Exposure for 60 min at 15 mW/cm2 did not activate the macrophages while 40 mW/cm2 exposure was harmful to some hamsters. Average maximum core temperatures in the exposed (25 mW/cm2) and sham groups were 40.5 degrees C (+/- 0.35 SD) and 38.4 degrees C (+/- 0.5 SD), respectively. In vitro heating of macrophages to 40.5 degrees C was not as effective as in vivo microwave exposure in activating macrophages to the viricidal state. Macrophages from normal, sham-exposed, and microwave-exposed hamsters were not morphologically different, and they all phagocytosed India ink particles. Moreover, immune macrophage cytotoxicity for virus-infected or noninfected target cells was not suppressed in the microwave-irradiated group (25 mW/cm2, 1 h) as compared to sham-exposed controls, indicating that peritoneal macrophages were not functionally suppressed or injured by microwave hyperthermia.     

Wheat germ phosphoglycerate mutase: evidence for a metalloenzyme

Wheat germ phosphoglycerate mutase, exposed to 3.4 M guanidinium chloride at 22 degrees C and pH 7.8, slowly undergoes time-dependent inactivation which can be fully reversed by adding excess Co2+ or Mn2+ to a 50-fold dilution of the denaturing medium. Titration of the denatured enzyme with either Co2+ or Mn2+ shows that wheat germ mutase preferentially binds Co2+. Assuming 1:1 complexation between metal atom and protein, the apparent dissociation constants (Kd) for E Co2+ and E Mn2+ at 22 degrees C and pH 8.7 are approximately 1.06 and 1.84, respectively. Other metal atoms (e.g., Cr2+, Cu2+, Fe2+, Fe3+, Mg2+, and Ni2+) have no effect in restoring the apoenzyme's catalytic activity. At low concentrations (0.11-0.23 mM) Zn2+ partially restores activity, but promotes protein precipitation at elevated concentrations. Evidence suggests that all bisphosphoglycerate-independent phosphoglycerate mutases require either an intra- or an extramolecular metal atom in order to function. Attempts to characterize wheat germ mutase as a glycoprotein have yielded negative results.     

Overexpression of ubiquitin carboxyl-terminal hydrolase L1 arrests spermatogenesis in transgenic mice

Ubiquitin carboxyl-terminal hydrolase 1 (UCH-L1) can be detected in mouse testicular germ cells, mainly spermatogonia and somatic Sertoli cells, but its physiological role is unknown. We show that transgenic (Tg) mice overexpressing EF1alpha promoter-driven UCH-L1 in the testis are sterile due to a block during spermatogenesis at an early stage (pachytene) of meiosis. Interestingly, almost all spermatogonia and Sertoli cells expressing excess UCH-L1, but little PCNA (proliferating cell nuclear antigen), showed no morphological signs of apoptosis or TUNEL-positive staining. Rather, germ cell apoptosis was mainly detected in primary spermatocytes having weak or negative UCH-L1 expression but strong PCNA expression. These data suggest that overexpression of UCH-L1 affects spermatogenesis during meiosis and, in particular, induces apoptosis in primary spermatocytes. In addition to results of caspases-3 upregulation and Bcl-2 downregulation, excess UCH-L1 influenced the distribution of PCNA, suggesting a specific role for UCH-L1 in the processes of mitotic proliferation and differentiation of spermatogonial stem cells during spermatogenesis.     

Further quantification of human spermatogenesis: germ cell loss during postprophase of meiosis and its relationship to daily sperm production

Potential daily sperm production per gram of testicular parenchyma (PDSP/g) based on pachytene plus diplotene primary spermatocytes was determined by two methods for 10 men aged 26 to 53 years and compared with published daily sperm production per gram parenchyma (DSP/g) based on round spermatid nuclei for these same men. The PDSP/g based on primary spermatocytes was similar (P greater than 0.05) whether determined by histometric analysis (10.0 +/- 1.1 X 10(6] or from homogenates of parenchyma (10.4 +/- 1.0 X 10(6]. When PDSP/g values were compared to DSP/g (5.9 +/- 0.9 X 10(6) for the histometric or 5.5 +/- 0.8 X 10(6) for the homogenate method), 44.9 +/- 6.7% loss of potential sperm production during postprophase of meiosis was detected by the histometric approach and 48.3 +/- 7.9% loss by the homogenate method. Similar results were obtained when testes of 15 additional men aged 26 to 53 years were evaluated by the homogenate method; PDSP/g was 10.6 +/- 0.6 X 10(6), DSP/g was 5.8 +/- 0.5 X 10(6), and the loss during postprophase of meiosis was 45.3 +/- 4.4%. For all 25 men, DSP/g was significantly (P less than 0.01) correlated with PDSP/g (r = + 0.70) and with the percentage loss of potential sperm production during postprophase of meiosis (r = 0.86). Over 73% of the variation in DSP/g could be attributed to variation in the percentage loss during postprophase of meiosis. Whether faulty meiotic divisions and/or degenerating secondary spermatocytes were responsible, almost half of the potential sperm production in these 25 men was lost during postprophase of meiosis.