Biomedical subjects

J D Suarez

Publications and source records attributed to J D Suarez.

At least 19 recordsLinked to original sources

PubMed1998

Rat epididymal sperm quantity, quality, and transit time after guanethidine-induced sympathectomy.

Guanethidine, a chemical that selectively abolishes peripheral noradrenergic nerves, was used to investigate the role of sympathetic innervation in the maintenance of epididymal sperm quantity and quality. Four groups of 10 adult male rats each were treated daily for 21 days, by i.p. injections, with either 0 (saline vehicle), 6.25, 12.5, or 25 mg/kg guanethidine. Norepinephrine content was reduced to undetectable levels in the cauda epididymidis in all guanethidine groups after 3 wk of treatment and was reduced to 7.4% of the control values after 1 wk of 6.25 mg/kg treatment. While body weight gain was significantly decreased at 12.5 and 25 mg/kg compared to that in controls, there was a significant increase in the weights of the seminal vesicles/coagulating glands in all treated groups. The number of homogenization-resistant spermatids per testis and the daily sperm production per testis remained unchanged. The weight of the epididymis was significantly increased at 6.25 and 12.5 mg/kg. Moreover, the number of cauda epididymal sperm and the transit time were increased significantly at 6.25 mg/kg (10.2 days) compared to values in the control cauda (6.3 days). Neither serum testosterone levels nor LH was affected in a dosage-related manner. There were no effects of guanethidine treatment on cauda epididymal sperm motility or morphology. A quantitative analysis of detergent-extracted cauda epididymal sperm proteins by SDS-PAGE revealed no differences, but there were diminutions in seven proteins in homogenates of caput/corpus tissue. Histologic analysis of testis and epididymis sections revealed no differences between control and denervated animals. In a subsequent experiment the lowest effective dosage (6.25 mg/kg) was given to rats for 1 wk, and an increased number of cauda epididymal sperm and a delay in sperm transit were observed. Our results indicate that low-dosage guanethidine exposure denervates the epididymis within 1 wk, thereby delaying epididymal transit; however, neither 1- nor 3-wk exposure produces qualitative changes in the sperm.

Animals↗

PubMed1998

Fertility of rat epididymal sperm after chemically and surgically induced sympathectomy.

Guanethidine, a chemical that selectively blocks sympathetic noradrenergic neurons, was used to investigate the role of sympathetic innervation in the fertility of rat epididymal sperm, using both natural mating and in utero insemination protocols. This animal model correlates, at least in part, with spinal cord injury (SCI) in men. Adult male rats were treated daily by i.p. injections, for 21 or 42 days, with 0 or 6.25 mg/kg guanethidine. To compare the effects of guanethidine-induced sympathectomy with those following surgically induced sympathectomy, the inferior mesenteric ganglion and the proximal hypogastric nerves were removed in another group of rats. Both chemically and surgically induced sympathectomy increased the weight of the epididymis and seminal vesicles/coagulating glands as well as the number and the transit time of cauda epididymal sperm. Neither serum testosterone levels nor LH was affected by treatment with guanethidine. Using natural mating, no litters were produced by guanethidine-treated rats. Chemically denervated rats failed to produce copulatory plugs or ejaculate into the uterus. However, distal cauda epididymal sperm from chemically or surgically denervated rats displayed normal fertilization ability (80%) using in utero inseminations. In addition, the sperm of denervated rats did not show abnormal sperm chromatin structure using an assay that detects DNA damage. We conclude that sympathectomy delays the transit of sperm through the cauda epididymidis and produces ejaculatory dysfunction but does not compromise sperm quality in the distal cauda epididymidis. Moreover, these data provide compelling evidence that there is no association between the prolonged transit time of sperm within the epididymis, i.e., pre-ejaculatory sperm aging, and the fertility of those sperm, which has important implications for artificial insemination using sperm from men with SCI.

Animals↗

PubMed1998

The 12 kD FK 506 binding protein FKBP12 is released in the male reproductive tract and stimulates sperm motility.

BACKGROUND: The 12 kD FK506 binding protein FKBP12 is a cytosolic receptor for the immunosuppressant drugs FK506 and rapamycin. In addition to its critical role in drug-induced T-cell immunosuppression, FKBP12 associates physiologically with ryanodine and inositol 1,4,5-trisphosphate (IP3) receptors, regulating their ability to flux calcium. We investigated a role for FKBP12 in male reproductive physiology on the basis of our identification of extremely high levels of [3H]FK506 binding in male reproductive tissues. MATERIALS AND METHODS: [3H]FK506 binding studies were performed to identify tissues enriched with FK506 binding sites. The abundant [3H]FK506 binding sites identified in the male reproductive tract were localized by [3H]FK506 autoradiography. FK506 affinity chromatography was employed to purify FKBP from epididymal fluid. Anti-FKBP12 Western analysis was used to confirm the identity of the purified FKBP. The binding of exogenous FKBP12 to sperm was evaluated by [32P]FKBP12 binding studies and [33P]FKBP12 autoradiography. The effect of recombinant FKBP12 on sperm motility was investigated using a Hamilton Thorne motility analyzer. RESULTS: Male reproductive tissues contained high levels of [3H]FK506 binding. The localization of [3H]FK506 binding sites to the tubular epithelium of the caput epididymis and the lumen of the cauda and vas deferens suggested that FKBP is released in the male reproductive tract. FKBP12 was purified from epididymal plasma by FK506 affinity chromatography. Radiolabeled FKBP12 specifically bound to immature but not mature sperm. In sperm motility studies, FKBP12-treated caput sperm exhibited double the curvilinear velocity of untreated controls. CONCLUSIONS: High levels of FKBP12 are released in the male reproductive tract and specifically associate with maturing sperm. Recombinant FKBP12 enhances the curvilinear velocity of immature sperm, suggesting a role for FKBP12 in motility initiation. The highest concentrations of soluble FKBP12 in the male reproductive tract occur in the lumen of the vas deferens, a site of sperm storage and the conduit for ejaculated sperm. Preservation of mammalian sperm for reproductive technologies may be optimized by supplementing incubation or storage media with FKBP12.

Animals↗

PubMed1995

Dibromoacetic acid affects reproductive competence and sperm quality in the male rat.

Recently, we demonstrated with short-duration tests that dibromoacetic acid (DBAA), a commonly occurring by-product of water disinfection, alters sperm morphology and motility in the male rat. These results suggested that the effects of DBAA on sperm quality were likely to compromise reproductive competence of the male rat early in subchronic exposure. The present studies were undertaken to investigate the dose response and time course of alterations in fertility and sperm quality. Proven breeder male rats were gavaged daily with 0, 2, 10, 50, or 250 mg DBAA/kg for up to 79 days; interim and terminal measurements of sperm quality and reproductive outcome were made. Because of the known neurotoxicity of the analogue, dichloroacetic acid, both natural breeding and artificial inseminations were evaluated in untreated females to distinguish between possible behavioral and spermatogenic effects. DBAA compromised male fertility during the second treatment week in naturally bred rats dosed with 250 mg/kg. The early antifertility effect appeared to be the result of behavioral changes since females artificially inseminated with sperm collected on Day 9 successfully produced offspring. However, sperm morphology and motility also were rapidly affected by DBAA treatment so that no offspring via natural insemination and only one litter via artificial insemination were produced subsequent to Day 15. Through 31 days, substantial effects on sperm motility, sperm morphology, and epididymal sperm numbers were observed, but there was no demonstrable effect on serum testosterone or sperm production. Because severe toxicity developed in the group given 250 mg/kg, exposure of these animals was prematurely terminated after 42 doses and their recovery was monitored through a 6-month posttreatment period; decreased testis weights and only limited recovery of reproductive performance were observed. Exposure to 50 mg/kg resulted in moderate changes in sperm morphology and motility and moderate decreases in epididymal sperm counts in rats dosed for 31 or 79 days. However, these males remained fertile, litter size was unaffected, and no paternally mediated developmental defects were noted in their offspring. No effects on sperm quality were detected at dosages of 2 or 10 mg/kg. However, compared to controls, naturally bred DBAA-treated rats tended to have fewer inseminations, fewer copulatory plugs, and fewer multiple litters, suggesting that DBAA may have altered mating behavior at dosages as low as 10 mg/kg.

Acetates↗

PubMed1994

Acute spermatogenic effects of bromoacetic acids.

Chlorine and bromine can react with natural organic substances in source waters to form haloacetic acids, major disinfection by-products of water chlorination. Several toxic effects including testicular damage have been attributed to the chloroacetic acids but little information is available on the bromine analogues. In this report we present the results of acute toxicity and acute spermatotoxicity studies of monobromoacetic acid (MBAA) and dibromoacetic acid (DBAA). In adult male rats the acute oral toxicity of MBAA was 10-fold that of DBAA (LD50 177 vs 1737 mg/kg). No reproductive-related endpoints were affected in rats given a single dose of 100 mg MBAA/kg or 14 daily doses of 25 mg MBAA/kg/day. In rats dosed with DBAA, serum testosterone fell to 17% of control 2 days after a single dose of 1250 mg/kg but returned to control levels by Day 14. Marked effects on sperm motion were seen on post-treatment Days 14 and 28. Degenerative flagellar changes in cauda sperm were present on Day 14 while abnormal sperm head shapes and flagellar degeneration were observed in both caput and cauda sperm on Day 28. Histopathology indicated altered spermiation at all time-points as evidenced by retention of Step 19 spermatids beyond Stage VIII of the cycle of the seminiferous epithelium. Disorganization, distortion, and degeneration of late spermatids were also observed. On Day 14 structures resembling residual bodies were rarely seen in the testis but were numerous in the epididymis. Caput sperm counts were decreased on Day 2 and cauda sperm counts were decreased on Days 14 and 28.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗

PubMed1994

Chloroethylmethanesulfonate-induced effects on the epididymis seem unrelated to altered Leydig cell function.

Decades ago it was reported that when male rats were exposed to chloroethylmethanesulfonate (CEMS) for 5 days prior to weekly matings with untreated females, the second mating resulted in reduced litter size. Since fertility was not assessed at earlier time points, it was not possible to determine whether CEMS exerted any effects on sperm in the epididymis. In this study, we used a 4-day exposure and assessed multiple reproductive endpoints on Day 5 to characterize effects of CEMS exposure (6.25-25 mg/kg) on Leydig cells and the epididymis. Exposure to CEMS caused a dose-related decline in serum testosterone (T) levels. This occurred at a dose lower than that required to decrease T production in vitro by testicular parenchyma. The in vitro decline was not attributed to a decrease in maximal hCG-stimulated T production, but to a decrease in unstimulated T production. CEMS was 5-fold less sensitive than ethane dimethanesulfonate (EDS) in reducing maximal hCG-stimulated T production. To control for alterations in the epididymis resulting from decreased serum T alone, T was implanted in CEMS-treated animals to maintain serum T at a concentration similar to that found in normal rats. This exogenous T failed to prevent the CEMS-induced decrease in the weight of the caput/corpus epididymidis but did prevent the CEMS-induced decrease in seminal vesicle weight. Implantation of T failed to prevent the CEMS-induced reduction in sperm reserves in the cauda epididymidis, and it failed to prevent the CEMS-induced alterations in the histology of both the corpus and proximal cauda epididymidis. The height of the epithelium in both of these regions was increased, and clear cells disappeared from the proximal cauda epididymidis. These results demonstrate that CEMS might alter the ability of the Leydig cell to respond to LH stimulation in vivo, and that alterations in the structure and function of the epididymis occur even when the serum concentration of T is maintained.

Alkanesulfonates↗

PubMed1993

Optimization of the Hamilton-Thorn computerized sperm motility analysis system for use with rat spermatozoa in toxicological studies.

To optimize the Hamilton-Thorn Motility Analyzer (HTM; Hamilton-Thorn Research, Beverly, MA) for use in reproductive toxicology studies with rat spermatozoa, the accuracy and precision of the instrument were assessed under a variety of instrument settings. Videotapes of both fast- and slow-swimming sperm were analyzed repeatedly to obtain data across a range of sperm velocities as might be encountered as a consequence of exposure to reproductive toxicants. Acquisition rates were varied across the HTM menu choices (30, 19, 10, or 7 frames/sec) as were the number of frames analyzed (5 to 20) at each framing rate. For fast-swimming samples (mean straight-line velocity (VSL) approximately 130 microns/sec) generally good agreement between computer-assisted sperm analysis (CASA) and manually obtained data was found for percentage of motile sperm and straight-line velocity; i.e., CASA values were within 10% of manual values for most frame/rate combinations. The accuracy of these measures held true over a wide range of sperm concentrations and percentage motilities. However, CASA measures were less accurate for sperm samples of lower velocities (mean VSL approximately 50 microns/sec and mean VSL approximately 30 microns/sec) in that the velocity of very slow sperm was overestimated (particularly at 30 frames/sec). A soft-ware change (6.5R) and performing analyses at 19 instead of 30 frames/sec improved straight-line accuracy for the slow sperm and enhanced the discrimination between fast (presumably control) and slow (presumably treated) sperm samples. These data show that this motility analyzer could be successfully configured to evaluate rodent sperm samples. The use of such CASA systems in toxicology studies will provide valuable information that may improve human reproductive risk assessment.

Animals↗

PubMed1992

Endpoints of spermatotoxicity in the rat after short duration exposures to fourteen reproductive toxicants.

Multiple endpoints of spermatotoxicity in short duration tests (1-5 days exposure; 2.5-week assay interval) were investigated in a number of chemicals reported to produce minimal to severe reproductive effects when administered subchronically. Six of these chemicals (boric acid, dinoseb, 2,5-hexanedione, methoxychlor, metronidazole, ornidazole) produced substantial spermatotoxicity after 1 to 5 doses. Spermatotoxic effects of chlordimeform were equivocal while p,p'-DDT, n-hexane, and sodium chlorite were judged negative. Four chemicals with known acute effects (benomyl, busulfan, ethylene glycol monomethyl ether, nitrobenzene) elicited expected histopathologic responses after a single dose. Testicular histology, testicular sperm head counts, cauda sperm counts, sperm morphology, and sperm velocity proved to be the most toxicologically sensitive endpoints in one or more of the studies, but histopathology of the testis and epididymis was the most consistent indicator of reproductive damage. The percentage of motile sperm and sperm concentration in the epididymal fluid were the least sensitive measurements. The data suggested that most chemicals with the potential to produce moderate to severe sperm damage are detectable with a short duration test. Complementary multiple endpoints enhanced the interpretation of results, often identified cellular targets, and provided insight on possible mechanisms. Specific responses were often similar to specific effects reported for subchronic exposures. A short duration test could be of value as a screen in structure-activity studies or to set priorities for chemicals requiring further evaluation. As a supplement to breeding studies, the data generated in the short test could also be used to enhance the design and interpretation of the longer tests.

Animals↗

PubMed1991

Rat sperm motility analysis: methodologic considerations.

The objective of these studies was to optimize conditions for computer-assisted sperm analysis (CASA) of rat epididymal spermatozoa. Methodologic issues addressed include sample collection technique, sampling region within the epididymis, type of diluent medium used, and sample chamber depth. In addition, sources of variation were identified and accuracy of the analysis was examined. All samples in this report were analyzed using a Hamilton Thorn Motility Analyzer (HTM-2000; Hamilton Thorn Research, Danvers, MA). We found that allowing the sperm to swim out from cuts made in the distal cauda epididymidis yielded samples with percentages of motile sperm 60% higher than samples collected using an aspiration method. Furthermore, sperm isolated from the distal cauda epididymidis exhibited slightly but significantly greater percentages of motile sperm and swimming speeds than sperm isolated from the proximal cauda epididymidis. Of the four motility media examined, all maintained a high percentage of motile sperm over an hour-long incubation period, but Medium 199 and modified Hanks' Balanced Salt supported substantially greater sperm velocity than Dulbecco's Phosphate Buffered Saline (with Ca++ and Mg++), with or without glucose. Motility and velocity endpoints were comparable in 200-, 100-, or 40-micron deep chambers, but significantly lower in 20-micron-deep chambers. Since these and presumably other variables in the preparation and analysis of rat sperm do influence the assessed motility endpoints, it is important to standardize these methods and to consider these issues when interpreting CASA data.

Animals↗

PubMed1991

The method of sperm collection significantly influences sperm motion parameters following ethane dimethanesulphonate administration in the rat.

Sperm motion analysis following exposure to a reproductive toxicant is one means of evaluating the functional integrity of the testis and epididymis. In this study we sought to determine whether the method used to collect sperm from the proximal cauda epididymidis, where sperm are not completely mature, has a significant influence on sperm motion parameters. Two methods of collecting rat sperm for motion analysis were used: one based on an aspiration technique selected from the literature; the other, a new approach based on diffusion of sperm from the epididymal tubule. The two methods were tested for sensitivity to effects on sperm motility parameters 4 days after a single exposure to ethane dimethanesulphonate (EDS). Since EDS is known to decrease serum testosterone (T), an additional group of rats received T-filled implants just prior to dosing to determine if the decrease in serum T alone had an effect on sperm motility. The results of the study yielded strikingly different interpretations of the effect of a 65 mg/kg BW dose of EDS on the motility of sperm taken from the proximal cauda epididymidis. Sperm collected by "aspiration" showed no significant decrease in the percentage of motile or progressively motile sperm compared to vehicle-treated animals. On the contrary, sperm collected by "diffusion" showed large, significant decreases in the percentages of both motile and progressively motile sperm. This difference was due largely to lower percentages of motile and progressively motile sperm in control sperm samples collected by aspiration. Similarly, the motion parameters of sperm collected by the aspiration method were unaffected by EDS/T treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Multiple effects of ethane dimethanesulfonate on the epididymis of adult rats.

Ethane dimethanesulfonate (EDS), a Leydig cell toxicant which results in transient infertility, was used in a 4 day postexposure experimental protocol designed to identify any effects this compound might exert on the epididymis. The techniques of efferent duct ligation and testosterone (T) implantation were used to negate the role of testicular effects on the epididymal parameters. Numerous evaluations were performed including light and electron microscopy, computer assisted sperm motion analyses, and electrophoresis of sperm membrane proteins. EDS was shown to affect the epididymis in a dose-dependent fashion. The action of EDS on the epididymis is in part due to Leydig cell cytotoxicity and the resulting decrease in circulating androgen since T implantation prevented some of the changes in sperm proteins and motility. However, neither efferent duct ligation nor T implantation prevented the formation of sperm granulomas in the caput epididymidis, the distinct morphological alterations of the corpus epididymidis, the modification of certain sperm membrane proteins, or the decrease in the progressive motility and velocity of sperm following EDS treatment. Although we cannot prove these effects of EDS are due to a direct action on the epididymis, it is now clear that EDS has a distinct action on the epididymis which is unrelated to circulating T or testicular fluid.

Animals↗

PubMed1990

Acute inhalation exposure to epichlorohydrin transiently decreases rat sperm velocity.

The effect of inhaled epichlorohydrin on rat sperm motility characteristics was evaluated. Male F-344 rats were exposed to 100 ppm epichlorhydrin via inhalation for 4 hr in the morning of Day 0 and killed immediately and on Days 1, 2, 6, and 14 postexposure. Videotapes of cauda epididymal sperm were analyzed (300-350 sperm/sample) with a Hamilton Thorn motility analyzer (HTM-2000, Hamilton Thorn Research, Danvers, MA). Epichlorohydrin did not affect the percentage of motile sperm at any time. However, transient changes in sperm velocity were found. On Day 1 postexposure mean progressive (straight line) and mean path (smoothed curvilinear) velocity were significantly decreased to 80 and 85% of control, respectively. The progressive velocities of sperm from both control and treated rats were normally distributed, indicating a general effect of epichlorohydrin on all sperm as opposed to a more severe effect on a specific sperm subpopulation. Sperm velocity was not significantly affected at later times. Other endpoints (testis and epididymis weights, testicular spermatid counts, and cauda epididymal sperm reserves) were unaltered by epichlorohydrin. Thus, inhaled epichlorohydrin at 100 ppm produced specific, transient decreases in rat sperm velocity. Furthermore, computer-assisted sperm analysis was able to detect these relatively subtle, toxicant-induced changes in rat sperm velocity, demonstrating the utility of this technology in reproductive toxicology studies.

Administration, Inhalation↗

PubMedDate not supplied

Spermatotoxicity of dibromoacetic acid in rats after 14 daily exposures.

Halogenated acetic acids are major disinfection by-products of water chlorination and ozonation. Limited data in experimental animals indicate that repeated doses of dichloroacetic acid (DCA) or single doses of dibromoacetic acid (DBAA) cause testicular damage. In the present study, spermatotoxic effects were investigated in rats given oral doses of 0, 10, 30, 90, or 270 mg DBAA/kg/day for 14 days. In rats dosed with 270 mg/kg/day, there were marked effects on epididymal sperm motility and morphology including the flagellar fusion of 2 or more sperm. Testis weight, epididymis weight, and testicular sperm head counts were mildly reduced relative to control, whereas epididymal sperm counts were substantially decreased. Histologic changes in the testis included retention of Step 19 spermatids in Stages IX to XII, abnormal development of late spermatids, and the formation of atypical structures resembling residual bodies that were observed predominantly in Stages X to XIV and I of the cycle of the seminiferous epithelium. At the dosage of 90 mg/kg/day, effects on spermiation, spermatid development, epididymal sperm counts, sperm motility, and sperm morphology were less severe than at the higher dosage. Reduced caput sperm counts and mild effects on spermiation also occurred at 30 and 10 mg/kg/day. These studies indicate that subchronic exposure to DBAA has the potential to affect reproductive outcome in the rat. Compared to previous studies of DCA (12), DBAA, on a molar basis, appears to be a stronger testicular toxicant than the dichloro analogue.

Acetates↗

PubMedDate not supplied

Preliminary screening for the potential of drinking water disinfection byproducts to alter male reproduction.

There is increasing epidemiologic interest in the role drinking water disinfection byproducts (DBPs) may play in adverse reproductive outcomes such as inability to conceive, spontaneous abortion, and low birth weight. Although dozens of DBPs already have been identified, only a few studies have attempted to determine whether DBPs alter male reproductive parameters such as testicular and epididymal histology, testicular and epididymal sperm numbers, and epididymal sperm morphology and motility in laboratory animals. In these studies, alterations in epididymal sperm motility seemed to be predictive of more generalized toxicity of the male reproductive system. Because there is a need to prioritize DBPs for thorough reproductive and developmental toxicity testing, preliminary screening for the potential of DBPs to alter reproductive function seems warranted. Here, we elected to examine only cauda epididymal sperm motion parameters and testicular and epididymal histopathology. The effects of exposure to two commonly occurring DBPs, bromodichloromethane (BDCM) and chloral hydrate (CH), via drinking water were evaluated in F344 rats at an interim (52 week) necropsy during cancer bioassay studies. Exposure to 22 and 39 mg/kg BDCM and 55 and 188 mg/kg CH did not produce any systemic toxicity. Histopathologic evaluation revealed no gross lesions in the reproductive organs, and no tumors were detected in any tissues. In contrast, exposure to 39 mg/kg BDCM significantly decreased the mean straight-line, average path, and curvilinear velocities of sperm recovered from the cauda epididymidis. This BDCM exposure shifted the average path velocity distribution to a lower modal velocity range. Exposure to 188 mg/kg CH significantly decreased both the percentage of motile and progressively motile sperm. This CH exposure shifted the straight-line velocity distribution to a lower modal velocity range. These are the first reproductive toxicity data from exposure to BDCM and CH. The observed effects on sperm motion occurred in the absence of carcinogenesis. Because the effects of BDCM on sperm motility occurred at a lower exposure than that of other DBPs that compromise sperm motility, a thorough reproductive evaluation now is underway.

Animals↗

PubMedDate not supplied

Histopathologic changes in the testes of rats exposed to dibromoacetic acid.

The present report details histopathologic changes in the testis and epididymis of rats gavaged daily for 2 to 79 d with a by-product of water disinfection, dibromoacetic acid (DBAA). On treatment day 2 abnormal retention of Step 19 spermatids was observed in animals given the highest dosage of 250 mg/kg. Additional changes on day 5 included the fusion of mature spermatids and the presence of atypical residual bodies (ARB) in the epithelium and lumen of Stage X-XII seminiferous tubules. By day 9, ARB were seen in most stages of the seminiferous epithelial cycle and in the caput epididymidis. On day 16 distorted sperm heads were recognized in Step 12, and older spermatids, and luminal cytoplasmic debris was found throughout the epididymis. On day 31, there was vacuolation of the Sertoli cell cytoplasm, extensive retention of Step 19 spermatids near the lumen of Stage IX and X tubules, and vesiculation of the acrosomes of late spermatids. Marked atrophy of the seminiferous tubules was present 6 months after 42 doses of 250 mg/kg. ARB and retention of Step 19 spermatids were observed after 31 and 79 doses of 50 mg/kg and increased retention of Step 19 spermatids was seen in several rats dosed with 10 mg/kg. No abnormalities were detected at the dosage of 2 mg/kg. The changes suggest that the testicular effects of DBAA are sequelae to structural and/or functional changes in the Sertoli cell.

Acetates↗

PubMedDate not supplied

Toxicant-induced acceleration of epididymal sperm transit: androgen-dependent proteins may be involved.

Previously we established that a 4-d exposure to chloroethylmethanesulphonate (CEMS), a chemical that significantly reduces serum testosterone (T) levels, resulted in a significant decrease in cauda epididymal sperm reserves in adult male rats while homogenization-resistant testicular spermatid numbers were unaffected. This epididymis-specific alteration occurred whether or not circulating T levels were maintained using T-filled Silastic implants. To determine whether this epididymis-specific decrease in sperm number was the result of decreased epididymal transit time, the vas deferens was ligated at its midpoint just prior to the first of 4 d of exposure to CEMS with and without T implantation. If epididymal sperm transit was accelerated due to treatment, there would be fewer sperm in the caput/corpus and more sperm in the cauda/vas of the treated animals compared to control. The number of sperm in the caput/corpus decreased significantly (P < 0.05) while the number of sperm in the cauda/vas increased significantly in both the CEMS and CEMS + T animals. Daily sperm production was unaffected, but transit time through the caput/corpus epididymidis was decreased significantly in both treatment groups. To determine if testicular fluid played a role in the epididymis-specific decline in sperm numbers, the efferent ducts were ligated at the same time the vas deferens was ligated. Again, the number of sperm in the caput/corpus decreased significantly with treatment while there was a reciprocal increase in the number of cauda/vas sperm relative to controls. Finally, to determine whether an androgen-mediated process might be involved, the known antiandrogen hydroxyflutamide (HFLUT) was given to castrated, T-implanted animals in which the fertilizing ability of epididymidal sperm is maintained over 4 days. Once again, the number of sperm in the caput/corpus decreased significantly while there was a reciprocal increase in cauda/vas sperm. A quantitative evaluation of the protein profile in homogenates of the caput/corpus epididymidis revealed treatment-related diminutions in two proteins CC9 (M(r) = 42 kDa, pI = 4.2) and CC34 (M(r) = 35 kDa, pI = 5.5), and the level of each of these proteins in the caput/corpus was significantly correlated with the decrease in caput/corpus sperm number. Thus, both CEMS and HFLUT accelerate sperm transit through the proximal segment of the epididymis; and, while this effect is not dependent on the testis, it may involve a lesion in androgen-dependent epididymal function.

Animals↗

PubMedDate not supplied

Spermatotoxicity of dichloroacetic acid.

The testicular toxicity of dichloroacetic acid (DCA), a disinfection byproduct of drinking water, was evaluated in adult male rats given both single and multiple (up to 14 d) oral doses. Delayed spermiation and altered resorption of residual bodies were observed in rats given single doses of 1500 and 3000 mg/kg; these effects persisted to varying degrees on post-treatment days 2, 14, and 28. Delayed spermiation and formation of atypical residual bodies also were observed on days 2, 5, 9, and 14 in rats dosed daily with 1440, 480, 160, and 54 mg/kg. Distorted sperm heads and acrosomes were observed in step 15 spermatids after 14 doses of 480 and 1440 mg/kg. Decreases in the percentage of motile sperm occurred after 9 doses of 480 and 1440 mg/kg and 14 doses of 160 mg/kg. Increased numbers of fused epididymal sperm were observed on days 5, 9, and 14 in rats dosed with 1440, 480, and 160 mg/kg, respectively; other morphologic abnormalities occurred at 160 mg/kg and higher. On day 14, a significant decrease in epididymis weight was observed at 480 and 1440 mg/kg, and epididymal sperm count was decreased at 160 mg/kg and higher. These studies demonstrate that the testicular toxicity induced by DCA are similar to those produced by the analogue, dibromoacetic acid. However, the testicular toxicity of DCA is less severe at equal molar concentrations. Moreover, the DCA-induced testicular lesions occur with greater potency as the duration of dosing increases, indicating the importance of using low-dose subchronic exposures to assess the health risk of prevalent disinfection byproducts.

Acetates↗

PubMedDate not supplied

Direct effects of ethane dimethanesulphonate on epididymal function in adult rats. An in vitro demonstration.

It was recently demonstrated that the Leydig cell toxicant ethane dimethanesulphonate (EDS) produces multiple effects on the epididymis after a single in vivo exposure. To determine whether any of the perturbations were mediated by a direct action of the compound, we used a novel system for the coculture of epididymal epithelial cells and sperm from the caput epididymidis. This system maintains the morphologic integrity and cell polarity of the epididymal epithelial cells before and during coculture, and the sperm recovered after coculture have intact plasma and acrosomal membranes. In addition, several functions required for epididymal sperm maturation are expressed, including the secretion of protein by the epididymal epithelium, the association of secreted protein with the plasma membrane of cocultured sperm, and the acquisition of progressive motility by cocultured sperm. In vitro exposure of epididymal epithelial cells and sperm to EDS results in a significant decline in protein secretion by the epithelial cells during coculture, and in particular, a dose-dependent decline in a 36- to 38-kd protein (PI 4.0 to 4.5) and a 34- to 36-kd protein (PI 4.5 to 5.0). Moreover, these and other proteins are not recovered from the sperm membrane of cocultured sperm after EDS treatment. Finally, EDS results in a dose-dependent decline in the percentage of both motile and progressively motile sperm recovered after coculture compared with that of sperm from untreated cocultures. These effects on sperm motility were not observed when sperm were pretreated with EDS and subsequently cocultured with untreated epithelial cells. We conclude that EDS alters epididymal sperm maturation by acting directly on the epididymal epithelium to mediate changes in sperm membrane protein, and that this may subsequently alter the development of the progressive motility of sperm.

Animals↗