Biomedical subjects

R A Hess

Publications and source records attributed to R A Hess.

106 records · Page 6Linked to original sources

PubMedDate not supplied

Acute effects and long-term sequelae of 1,3-dinitrobenzene on male reproduction in the rat. I. Sperm quality, quantity, and fertilizing ability.

Groups of eight adult male rats were given a single oral dose of 0 or 48 mg/kg of 1,3-dinitrobenzene and sacrificed at 1, 2, 4, 8, 16, 24, 32, 72, and 175 days posttreatment. The groups killed at 175 days were bred to untreated females during weeks 3, 4, 6, 9, 13, and 24. Decreased testis weight and testicular sperm numbers were observed by day 4; decreased cauda sperm reserves and epididymis weight occurred by day 8 and day 16, respectively. Reduced numbers of motile spermatozoa and abnormal sperm morphology were seen in spermatozoa from the cauda epididymidis by day 16. Fertilizing ability, as indicated by the presence of two pronuclei and a sperm tail in eggs flushed from the oviducts of inseminated females, was slightly reduced by week 4 and declined to zero by week 6. Group means for reproductive organ weights, sperm production, and sperm reserves failed to return to control levels although some individual animals approached full recovery. Normal fertilizing ability was restored in most animals by week 13, but two of seven remained infertile. Occlusion of some efferent ductules was observed in three of seven animals at 175 days. This study indicates that 1,3-dinitrobenzene is a potent testicular toxicant in the rat, capable of producing marked testicular damage, infertility, and possibly sterility from a single exposure.

Animals↗

PubMedDate not supplied

Acute effects and long-term sequelae of 1,3-dinitrobenzene on male reproduction in the rat. II. Quantitative and qualitative histopathology of the testis.

This study determined the quantitative and qualitative histopathologic effects of a single oral dose of 1,3-dinitrobenzene (48 mg/kg) on the rat testis from 1 to 175 days postexposure. The testis was damaged severely by hour 24, as evidenced by increased numbers of regressive seminiferous tubules that exhibited degenerating pachytene spermatocytes, chromatin margination in spermatids, giant cells, deformed spermatid heads, retained spermatids, and reduced numbers of meiotic figures. The major effects during the first 48 hours posttreatment were degeneration or exfoliation of pachytene spermatocytes and round spermatids and the retention of step 19 spermatids. These regressive effects continued until 24 days, after which the tubules either recovered or became atrophic. At the end of the study (175 days), three males were normal, one had regressed testicles, and three males had atrophic tubules (15 to 45%). Several cellular abnormalities were common throughout the period. In addition, the frequency of the stages of spermatogenesis was altered, an indication of a disturbance in the kinetics of spermatogenesis. 1,3-Dinitrobenzene produced profound and specific lesions in the seminiferous tubules, and recovery was slow and incomplete. Atrophic tubules seemed to form if the normal cellular associations were not reestablished within 24 days, possibly due to the inability of Sertoli cells to reorganize the synchrony of germ cell development.

Animals↗

PubMedDate not supplied

Inhibition of human lymphoproliferative responses and altered lymphocyte membrane phenotype by succinylacetone.

Succinylacetone (SA) proved to be a potent inhibitor of in vitro lymphoproliferative responses. This compound (3.0 mM) reduced the incorporation of 3HTdr by > 90% in mononuclear cell cultures stimulated with PHA, anti-CD3, IL-2 or phorbol dibutyrate-Ca2+ ionomycin. Furthermore, SA caused profound reduction in isotope uptake even if added to 3-day PHA-stimulated cultures as late as 6 h prior to harvest. Cells exposed to SA prior to mitogenic challenge and washed were not impaired in their proliferative activities. The addition of hematin to SA-containing cultures did not reverse the proliferative block. Phenotypic studies of stimulated cells suggested that SA does not preferentially affect one functional group of lymphocytes. However, it appeared that SA may act selectively to inhibit expression of transferrin receptors (CD71), a T-cell activation antigen. These data suggest that SA acts as a noncytotoxic immune inhibitor; this activity may be mediated, in part, by blocking cell activation and subsequent progress through the mitotic cycle.

Animals↗

PubMedDate not supplied

Intratubular spermatic granulomas of the canine efferent ductules.

Spermatic granulomas are inflammatory lesions that occur in the efferent ductule and epididymis of humans, goats, rats, and bulls. Three clinically normal dogs from a control group had histologic lesions of the initial segment of the caput epididymis consisting of intratubular spermatic granulomas. The granulomas were located within the efferent ductules, and the inflammatory response consisted primarily of aggregates of spermiophagic macrophages in the ductules. Sperm stasis of the affected ductules was evident by the dilation and accumulation of large numbers of spermatozoa in adjacent cross-sections of efferent ductules. Blind-ending efferent ductules were demonstrated by serially sectioning the initial segment of the epididymis. The intratubular granulomas did not completely occlude the outflow tract because spermatozoa were present in the cauda epididymis. While spermatic granulomas can be induced by trauma, infection, or toxins, spontaneous granulomas due to blind-ending ductules should be considered as a differential. Clinical history, location of the granuloma, and serial sectioning can help determine the most likely etiology in early cases.

Animals↗

PubMedDate not supplied

Evaluation of a motion fidelity criterion with visual scene changes.

An experiment examined how visual scene and platform motion variations affected a pilot's ability to perform altitude changes. Pilots controlled a helicopter model in the vertical axis and moved between two points 32-ft apart in a specified time. Four factors were varied: visual-scene spatial frequency, visual-scene background, motion-filter gain, and motion-filter natural frequency. Drawing alternating black and white stripes of varying widths between the two extreme altitude points varied visual-scene spatial frequency. The visual-scene background varied by either drawing the stripes to fill the entire field of view or by placing the stripes on a narrow pole with a natural sky and ground plane behind the pole. Both the motion-filter gain and natural frequency were varied in the motion platform command software. Five pilots evaluated all combinations of the visual and motion variations. The results showed that only the motion-filter natural frequency and visual-scene background affected pilot performance and their subjective ratings. No significant effects of spatial frequency or motion system gain were found for the values examined in this tracking task. A previous motion fidelity criterion was found to still be a reasonable predictor of motion fidelity.

Aerospace Medicine↗

PubMedDate not supplied

Modeling human pilot cue utilization with applications to simulator fidelity assessment.

An analytical investigation to model the manner in which pilots perceive and utilize visual, proprioceptive, and vestibular cues in a ground-based flight simulator was undertaken. Data from a NASA Ames Research Center vertical motion simulator study of a simple, single-degree-of-freedom rotorcraft bob-up/down maneuver were employed in the investigation. The study was part of a larger research effort that has the creation of a methodology for determining flight simulator fidelity requirements as its ultimate goal. The study utilized a closed-loop feedback structure of the pilot/simulator system that included the pilot, the cockpit inceptor, the dynamics of the simulated vehicle, and the motion system. With the exception of time delays that accrued in visual scene production in the simulator, visual scene effects were not included in this study. Pilot/vehicle analysis and fuzzy-inference identification were employed to study the changes in fidelity that occurred as the characteristics of the motion system were varied over five configurations. The data from three of the five pilots who participated in the experimental study were analyzed in the fuzzy-inference identification. Results indicate that both the analytical pilot/vehicle analysis and the fuzzy-inference identification can be used to identify changes in simulator fidelity for the task examined.

Aerospace Medicine↗

PubMedDate not supplied

Morphologic changes in efferent ductules and epididymis in estrogen receptor-alpha knockout mice.

Estrogen has been shown to have an important role in fluid reabsorption in efferent ductules of the testis. Our previous study of the estrogen receptor-alpha knockout mouse (ERKO) showed that the efferent ductules and rete testis were primary targets of estrogen receptor function. In the present study, a more comprehensive evaluation of the ERKO male reproductive tract was performed to determine the severity of effects in efferent ductules as well as the epididymis. The following observations were found in ERKO males: 1) blind-ending efferent ductules were more prevalent in ERKO than in wild type (WT) tissues; 2) glycogen-containing cells were observed at the rete testis-efferent ductule junction; 3) the tubular diameters of the efferent ductules and initial segment epididymides were dilated; 4) efferent ductules were dilated between 130 to 300% over wild type ductules; 5) efferent ductule epithelial height was reduced nearly 50%; 6) microvilli of nonciliated cells of efferent ductules were 64% shorter in length; 7) cilia were reduced in number; 8) initial segment epithelium was displaced into regions adjacent to the rete testis and in short segments of the common region of efferent ductule; 9) apical, narrow, and clear cells of the epididymis also were abnormal in some regions; 10) in the corpus and cauda regions, sperm granulomas were noted in one third of the ERKO males. In conclusion, the entire reproductive tract is affected in ERKO males. The cells showing the greatest effects were estrogen receptor-positive cells. It appears that in the ERKO mouse there are developmental anomalies that must be considered separately from adult dysfunctional changes in the male reproductive tract.

Animals↗

PubMedDate not supplied

Acute and long-term effects of a single dose of the fungicide carbendazim (methyl 2-benzimidazole carbamate) on the male reproductive system in the rat.

The effects of carbendazim (methyl 2-benzimidazole carbamate) on the testis, efferent ductules, and sperm were determined in the adult rat after a single oral dose. Two experimental trials were performed: a time response between 2 hours and 32 days after exposure using 0 and 400 mg/kg, and a dose response at 2 and 70 days after exposure using 0 to 800 mg/kg doses. In experiment 1, effects were seen throughout the 32-day period, beginning 8 hours after exposure; the effects included first an increase in testis weight, then decreases in testicular spermatid numbers and in the percentage of morphologically normal cauda sperm. In experiment 2, significant testicular and efferent ductal alterations occurred in animals treated with doses of 100 mg/kg or greater. A dose-dependent increase in testicular weight 2 days after treatment was accompanied by increases in seminiferous tubular diameter and excessive loss of immature germ cells in a stage-dependent manner. There was also a dose-dependent increased incidence of occlusions in the efferent ductules. The occluded ductules were characterized by severe inflammation and exhibited disorganization of the epithelium. At 70 days, there were dose-dependent decreases in mean testis weight and mean seminiferous tubular diameter; however, only minimal long-term effects were seen at 50 mg/kg. In testes exhibiting seminiferous tubular atrophy of greater than 25% (100 mg/kg or greater doses), all of the testes were associated with efferent ductules containing occlusions. Caput sperm numbers were significantly reduced in these testes. Occlusions, abnormal ductules, fibrosis, spermatic granulomas, and mineralization were observed in the ductuli efferents. Long-term effects of carbendazim on the testis were induced primarily by ductal occlusions. Results show that carbendazim produces more severe short- and long-term effects on the male reproductive system than the fungicide benomyl.

Administration, Oral↗

PubMedDate not supplied

Computer tracking of germ cells in the cycle of the seminiferous epithelium and prediction of changes in cycle duration in animals commonly used in reproductive biology and toxicology.

A computer program called Stages was written to aid the tracking of germ cells and stages forward and backward through time in the cycle of the seminiferous epithelium. The program incorporates the basic kinetics of spermatogenesis in the rat, mouse, hamster, guinea pig, dog, rabbit, bull, stallion, ram, boar, quail, monkey, and man. The program is flexible and permits the user to alter the cycle duration time and the frequency of each stage. Compiled for use on personal computers and available on floppy disks free of charge, Stages is menu-driven and requires no knowledge of programming. The program was tested using published data of testicular toxicity and vitamin A synchronization of stages. In general, predicted cell types were similar to those observed; discrepancies between observed and predicted data are discussed. When cycle duration time was changed, predicted data for stage synchronization coincided with the observed data. This program will improve the speed and accuracy of studying factors that affect spermatogenesis. By using Stages, it is possible to predict the target cell types in a toxicity study and to track affected cells over long periods of time. Predicted cell types may also indicate which cells to examine biochemically as well as morphologically in subsequent experiments. The program will also be useful to beginning students learning the complex patterns of cellular associations and the progression of germ cells in the cycle of the seminiferous epithelium.

Animals↗

PubMedDate not supplied

Deformation of the rat Sertoli cell by oral administration of carbendazim (methyl 2-benzimidazole carbamate).

Carbendazim (methyl 2-benzimidazole carbamate; MBC) has been reported to disrupt the microtubules of Sertoli cells in the rat, suggesting that the cells exposed to carbendazim would fail to maintain their shape due to the loss of their cytoskeleton. The present study was performed to determine whether exposure to carbendazim induced Sertoli cell deformation. For this purpose, changes in the shape and position of Sertoli cell nuclei, that appear to be associated with changes in the shape of the cells themselves, were observed in stage VI-VII seminiferous tubules of rat testis at 3 hours following treatment. Light microscopy and computer-aided three-dimensional reconstruction were also performed to survey the outline of the body. In the controls, parallel-positioned nuclei (nuclei with their longer axis parallel to the basement membrane), perpendicular-positioned nuclei (nuclei with their longer axis perpendicular to the basement membrane), and round-shaped nuclei (nuclei showing a round or regular triangular profile) accounted for approximately 52%, 35%, and 13% of the total, respectively. In Sertoli cells showing carbendazim-induced sloughing of germ cells, however, parallel-positioned nuclei accounted for 21% and the round-shaped nuclei for 51% of the total. Approximately 69% of perpendicular-positioned nuclei were located in the basal part of the cells in the controls, compared with 95% in tubules showing carbendazim-induced sloughing. These changes in individual parameters were significantly different (alpha < 0.05). Light microscopy and computer-aided reconstruction indicated that the body region of Sertoli cells in the control testis was columnar in shape, whereas that of Sertoli cells that showed sloughing was conical. These findings suggest that Sertoli cell cytoplasm, following carbendazim-induced sloughing, moves toward the base of the cellular axis.

Administration, Oral↗

PubMedDate not supplied

Mouse epididymal sperm contain active P450 aromatase which decreases as sperm traverse the epididymis.

Recently we reported that mouse germ cells in the testis contain active P450 aromatase (P450arom), the enzyme that converts androgens to estrogens. This finding suggested that germ cells have the ability to produce estrogen. Further studies have shown that germ cells in the testis of several species contain P450arom. The goal of this study was to determine if epididymal sperm contain P450arom and if P450arom activity in sperm changes during traversion of the epididymis in the adult mouse. P450arom was localized in sperm present in the efferent ductules and epididymis by immunocytochemistry using an antiserum generated against purified human placental cytochrome P450arom. P450arom immunostaining in sperm was most prominent in sperm located in the proximal caput epididymis, decreased as sperm traversed the corpus epididymis, and was only slightly apparent in sperm in the cauda epididymis. The immunolocalization of P450arom in epididymal sperm was supported by the measurement of P450arom activity in sperm by the 3H2O assay. We found that P450arom activity in sperm significantly decreases as sperm traverse the epididymis. Based upon these observations, we conclude that sperm can synthesize estrogen and that the synthesis of estrogen by sperm present in the efferent ductules and caput epididymis could be important in the process of sperm maturation.

Animals↗

PubMedDate not supplied

Increased proliferation of Leydig cells induced by neonatal hypothyroidism in the rat.

Treatment of male rat pups with the reversible goitrogen 6-n-propyl-2-thiouracil (PTU), administered by adding 0.1% PTU to the mother's drinking water from birth through weaning, increases adult testis size, number of Sertoli cells, and daily sperm production. Adult Leydig cell numbers are also increased by 70%, despite permanent suppression of serum luteinizing hormone (LH). The present study was designed to test whether this effect results from an increase in proliferation of Leydig cells or the mesenchymal precursors. The labeling indices (LI) of six interstitial cell types were measured by tritiated thymidine autoradiography. With the exception of Leydig cells, LI declined after birth for all interstitial cell types in both control and PTU-treated rats, but mesenchymal cell proliferation was not significantly different in control and treated rats. In contrast, the LI of Leydig cells from PTU-treated rats rose by day 10, remained elevated through day 45 (highest on day 35 at 3.6-fold higher than control, P < 0.05), and declined to control values by day 50. The LI of Leydig cells in control rats was unchanged during the experiment. Proliferating Leydig cells were immature, as shown by their cytoplasmic lipid droplets. Adult Leydig cells, which lack lipid droplets, did not proliferate. Mesenchymal and immature Leydig cells contained thyroid hormone receptor mRNA; levels in adult Leydig cells were reduced but detectable. In conclusion, proliferation of Leydig cells, rather than increased proliferation of their mesenchymal precursors, is the principal mechanism responsible for the increase in Leydig cell number after neonatal hypothyroidism. Increased Leydig cell proliferation could result from direct effects of hypothyroidism on these cells. Alternatively, the increased Sertoli cell population that results from PTU treatment could also stimulate increased Leydig cell proliferation, or both of these mechanisms could contribute to the Leydig cell increase.

Animals↗

PubMedDate not supplied

P450 aromatase messenger ribonucleic acid expression in male rat germ cells: detection by reverse transcription-polymerase chain reaction amplification.

We have previously demonstrated that cytochrome P450 aromatase (P450arom) protein, an estrogen-synthesizing enzyme, is present and active in germ cells of the adult mouse testis. To establish that P450arom mRNA is expressed in germ cells of other species, we examined expression of P450arom in adult rat germ cells by employing reverse transcription-polymerase chain reaction (RT-PCR). Total RNA was extracted from Staput separated germ cells and reverse transcribed. The resulting cDNA was amplified by nested PCR reactions using oligonucleotide primers selected from a highly conserved region of the P450arom gene. RT-PCR analysis yielded cDNA products of 334 bp in length that corresponded to the predicted size expected from the final nested amplification. The identity of the germ cell P450arom PCR products was confirmed by restriction enzyme analysis and direct nucleotide sequencing. Rat genomic DNA was subjected to PCR to verify that P450arom DNA products were not obtained from genomic DNA contamination. Rat genomic DNA yielded a nested PCR product for P450arom of approximately 2000 bp, suggesting that, as is the case with the human P450arom gene, the rat P450arom gene contains an intron in the amplified region. In addition, a semiquantitative technique was utilized to eliminate the possibility that the P450arom RT-PCR products were derived from Leydig cell contamination of Sta-put-separated germ cell preparations. RT-PCR for P450arom and 3-beta-hydroxysteroid dehydrogenase (3 beta-HSD), a Leydig cell-specific steroidogenic enzyme, was carried out on Sta-put-separated germ cells and interstitial cell preparations containing Leydig cells. P450arom and 3 beta-HSD RT-PCR reactions were stopped at three cycle intervals to detect and compare the earliest appearance of RT-PCR reaction products in various cell types. Results indicated that P450arom mRNA is detected in round spermatids before it is detected in interstitial cells, whereas 3 beta-HSD was detected only in interstitial cells, suggesting that the P450arom mRNA detected in germ cells is not due to interstitial cell contamination of germ cell preparations. Therefore, our results indicate that P450arom mRNA is expressed in adult rat germ cells and that testicular germ cells are a potential source of estrogen in the male reproductive tract.

Amino Acid Sequence↗

PubMedDate not supplied

Estrogen receptors are present in the epididymis of the rooster.

Our recent discovery that testicular germ cells and epididymal sperm contain active P450 aromatase suggests that the reproductive tract may be a target for estrogen. Therefore, the objective of this study was to determine if estrogen receptors (ER) are present in the avian epididymis using immunocytochemistry, northern blot analysis, and in situ hybridization. Immunoperoxidase staining for ER was found principally in nuclei of nonciliated epithelial cells of proximal and distal efferent ductules and the epididymis duct. The ciliated cells also appeared to be slightly positive in the efferent ductules. Week immunostaining was also observed in the connective tissue of the epididymis duct. Immunostaining was more intense in epithelial cells of the efferent ductules than in epithelial cells of the epididymal duct of connective tissue cells. Strong specific hybridization signals for ER mRNA corresponded to the same areas exhibiting immunocytochemical localization. The presence of ER mRNA in the epididymis was confirmed by northern blot analysis, which showed a single band corresponding to approximately 7.8 kb, similar to that found in chicken oviduct. Based on these data, we suggest that the efferent ducts of the rooster are a primary target for estrogen and that estrogen may have a role in the regulation of avian epididymal function.

Animals↗

PubMedDate not supplied

Estrogen receptor (alpha and beta) expression in the excurrent ducts of the adult male rat reproductive tract.

The understanding of estrogen's function in the male reproductive tract is limited, and estrogen receptor (ER) localization in the reproductive tract of the adult male rat has not been described. In the present study, ERalpha was localized by immunohistochemistry using ER21 antibody, which recognizes only ERalpha. Strongest immunoreactivity was seen in epithelia of ductuli efferentes and the initial segment of the epididymis. Nuclei of both ciliated and nonciliated cells were positive. The epithelium of the rete testis, and caput, corpus, and cauda epididymides stained less intensely for ERalpha. The vas deferens epithelium was ERalpha-negative. Stromal tissue in the excurrent ducts was also ERalpha-positive. Using 3H-estradiol autoradiography, specific binding of estradiol was seen in nuclei of ductuli efferentes. Estrogen receptor alpha mRNA expression was greatly enhanced in ductuli efferentes compared to other regions of the male tract and was 3.5x greater than in the uterus. For comparison, the presence of ERalpha was determined using reverse transcription-polymerase chain reaction (RT-PCR) amplification. Estrogen receptor beta mRNA was expressed throughout the male tract and in the prostate. These results indicate that all organs in the male excurrent ductal system of the rat express ERalpha and are potential targets of estrogen. However, the ductuli efferentes are the site of the most intense ERalpha expression. The role of ERbeta remains to be determined, but its expression appears ubiguitous in the male tract.

Animals↗

PubMedDate not supplied

Rat testicular germ cells and epididymal sperm contain active P450 aromatase.

Although testosterone is the principal sex steroid produced by the testis, estrogen is known to be produced by both Leydig and Sertoli cells during different developmental periods. Additionally, evidence is unfolding to suggest that germ cells might also participate in the synthesis of estrogen within the male reproductive tract. We have recently reported that the messenger ribonucleic acid (mRNA) for P450 aromatase (P450arom), the enzyme that converts androgen to estrogen, is synthesized by rat germ cells. Therefore, the present study was conducted to determine which germ cell types synthesize active P450arom and to measure the activity of this enzyme in germ cells throughout spermatogenesis and in maturing sperm during epididymal transit. First, P450arom activity was measured in pachytene spermatocytes, round spermatids, and a mixture of round spermatids, elongating spermatids, and residual bodies using the tritiated water (3H2O) assay. Second, sperm isolated from different regions of the epididymis were assayed for P450arom activity. Sperm isolated from the caput epididymis with attached efferent ductules had the higher P450arom activity, whereas sperm isolated from the corpus and cauda epididymides had lower P450arom activity. The decrease in P450arom activity in cauda sperm was further confirmed by immunocytochemistry. On the basis of these observations, we conclude that rat testicular germ cells from pachytene spermatocytes through elongating spermatids and epididymal sperm contain active P450arom and that sperm lose aromatase activity as they mature during epididymal transit. Therefore, both post-pachytene rat germ cells and epididymal sperm are capable of estrogen synthesis and are an additional, potentially significant, source of estrogen in the male reproductive tract.

Animals↗