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Biomedical subjects

P M Foster

Publications and source records attributed to P M Foster.

At least 37 records · Page 2Linked to original sources
PubMed1991

Evidence that secretion of immunoactive inhibin by seminiferous tubules from the adult rat testis is regulated by specific germ cell types: correlation between in vivo and in vitro studies.

This study has assessed whether depletion of specific germ cell types is able to alter the secretion of immunoactive inhibin by adult Sertoli cells in vivo and in vitro. Pachytene and later spermatocytes were depleted (80-100%) by a single administration of methoxy acetic acid (MAA; 650 mg/kg) to adult rats. At intervals between 1 and 42 days posttreatment, rats were killed, and the blood levels of FSH, LH, and testosterone were determined together with the levels of immunoactive inhibin in plasma and testicular interstitial fluid (IF). At the same time intervals, seminiferous tubules (ST; 5 x 2 cm) were isolated from control and MAA-treated rats and cultured for 24-72 h in the presence or absence of rat FSH, (Bu)2cAMP, or MAA under rigorously optimized conditions. The hormonal changes observed were related to the presence/absence of specific germ cell types, as determined by assessment of testicular morphology in perfusion-fixed testes from similarly treated rats. One to 3 days after MAA treatment, coincident with the depletion of pachytene spermatocytes, blood levels of FSH were increased significantly compared with controls; FSH returned to control levels at 7-14 days (when early spermatids were depleted), but were increased again at 21-35 days (when late spermatids were depleted). In contrast, while the plasma levels of immunoactive inhibin were increased 2-fold 3 days posttreatment, they were comparable to controls at 7-14 days, but were decreased substantially at 21-28 days. The levels of immunoactive inhibin in testicular IF were more than doubled 1 and 3 days posttreatment, but were comparable to control levels at all other times. Blood levels of LH showed a similar pattern of change to FSH, although only at 21-28 days after MAA treatment was there a significant increase, while blood levels of testosterone were comparable at all times in control and MAA-treated rats. To confirm that the changes observed in vivo after MAA treatment were indicative of changes in Sertoli rather than Leydig cell secretion of immonoactive inhibin, its secretion by isolated ST was assessed, and a pattern of change similar to that in plasma was observed. Thus, when cultured for 24 h under basal conditions, ST from rats 1-3 days after MAA treatment showed a 2- to 3-fold increase in secretion of immunoactive inhibin, which returned to control levels at 7-14 days before being reduced substantially at 21-28 days and then recovering to control levels; similar changes were observed for FSH- and (Bu)2cAMP-stimulated secretion of immunoactive inhibin.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetates↗
PubMed1990

The in vitro effects of four isomers of dinitrotoluene on rat Sertoli and Sertoli-germ cell cocultures: germ cell detachment and lactate and pyruvate production.

The present study was undertaken to evaluate the in vitro effects of four isomers of a known testicular toxicant, dinitroluene (DNT). Rat Sertoli or Sertoli-germ cell cocultures were treated, after 3 days in culture, with DNT isomers (0.01 to 100 microM) or 1,3-dinitrobenzene (1,3-DNB) for 24 hr. Cellular morphology, germ cell detachment (GCD) and lactate pyruvate production were used as sensitive effect markers of in vitro toxicity. Morphologically the Sertoli cell monolayer remained intact 24 hr after exposure to DMSO, 1,3-DNB, or DNT isomers. Some apparent cytotoxicity was observed at 100 microM 3,4-DNT: the monolayer was disrupted with extensive vacuolation of the Sertoli cells. Cocultures treated with concentrations of 50 microM DNT isomers closely resembled cells treated with 100 microM 1,3-DNB. GCD increased in a dose-dependent manner (0.01 and 10 microM DNT isomers) increasing between 2- and 10-fold over control. Both lactate and pyruvate production increased with rising concentrations of DNT isomers. The most sensitive effect was seen with 3,4-DNT (10 to 25 microM). In the case of 2,6-DNT, despite increases in GCD and lactate production, only a minimal increase in pyruvate was demonstrated. Overall, the ratio of lactate to pyruvate production declined with increasing doses of DNT. These results indicate that the four isomers of DNT directly affected Sertoli cell morphology and function, effects comparable to those seen with the Sertoli cell toxicant 1,3-DNB. Further, the data support the hypothesis that DNT may be a Sertoli cell toxicant.

Animals↗
PubMed1990

Changes in Sertoli cell function in vitro induced by nitrobenzene.

Nitrobenzene (NB) has been identified as a testicular toxicant in vivo, but its site of action remains unknown. In the present study, the effect of NB on the Sertoli cell was assessed in vitro using Sertoli cell and Sertoli-germ cell cocultures. The parameters measured were the exfoliation of germ cells; the secretion of lactate, pyruvate, and inhibin; and gross cellular morphology. The effect of metadinitrobenzene (mDNB), a related compound which is a known Sertoli cell toxicant, was assessed for comparison. Gross morphological changes including vacuolation of Sertoli cells were observed following treatment of cultures with 10(-3) M NB. Exposure of cocultures to NB also resulted in dose-dependent exfoliation of predominantly viable germ cells. NB (greater than 5 X 10(-4) M) and mDNB at the single dose level used (10(-4) M) stimulated the secretion of lactate and pyruvate significantly by Sertoli cells, an effect that was more marked in the absence of germ cells. Comparable changes were observed in follicle stimulating hormone (FSH)-stimulated cultures. Inhibin secretion by Sertoli cells was also altered by exposure to NB but in a biphasic manner, with low (10(-8) to 10(-6) M) and high (10(-4) to 10(-3) M) doses enhancing inhibin secretion while intermediate (10(-5) M) doses had no effect. These effects were evident in both culture systems but inhibin secretion by Sertoli-germ cell cocultures was always greater than that by Sertoli cell cultures. However, these effects of NB on inhibin secretion were not evident in FSH-stimulated cultures. In contrast to the effects of NB, mDNB had no effect on basal secretion of inhibin but blocked the stimulatory effect of FSH. It is concluded that NB, like mDNB, is probably a Sertoli cell toxicant in view of its similar disruptive effects on various parameters of Sertoli cell function. However, NB is far less toxic than mDNB at equivalent concentrations in vitro. The present study is the first to evaluate the potential of inhibin secretion by Sertoli cells in culture as an additional marker of toxicant action, and concludes that it merits further study in this context.

Animals↗
PubMed1990

The use of in vitro fertilization to detect reductions in the fertility of male rats exposed to 1,3-dinitrobenzene.

1,3-Dinitrobenzene (DNB) is an intermediate chemical in the manufacture of dyes and explosives and its toxic effects include specific damage to the Sertoli cells of the testis. This investigation determined the effect a toxic insult to Sertoli cells had on the functional capacity of developing germ cells as assessed by in vitro fertilization. Male rats were given a single, oral dose of 5, 15, or 25 mg DNB/kg. At selected times after treatment, spermatozoa recovered from the cauda epididymidis were tested for fertilizing capacity using in vitro fertilization techniques and the testicular response to DNB was determined by histological examination. Treatment with 15 and 25 mg DNB/kg resulted in substantial exfoliation of germ cells between 0.5 and 3.5 weeks after exposure and again after 4.5 weeks; seminiferous tubules which were not depleted showed signs of disrupted spermatogenesis. Reduced sperm fertilizing capacity in vitro was observed from 1.5 to 5 weeks and between 7.5 and 8.5 weeks after treatment with 15 and 25 mg DNB/kg. There were slight, but significant, reductions in fertility at 3, 5.5, 7.5, and 8.5 weeks after dosing with 5 mg DNB/kg. These data suggested that DNB did not affect all Sertoli cells equally, but acted in a stage-specific manner. Stages III, IV, XII, and XIV were most vulnerable to the toxicant. Germ cells associated with an affected Sertoli cell were usually sloughed off, resulting in lowered fertility at the time when these cells should have reached maturity in the epididymis. The extent of the testicular lesions and the loss of fertility were dose dependent. This investigation confirmed the use of in vitro fertilization to detect the effects of testicular toxicants.

Animals↗
PubMed1990

Modulation of m-dinitrobenzene and m-nitrosonitrobenzene toxicity in rat Sertoli--germ cell cocultures.

Previous work has shown that m-dinitrobenzene is a testicular toxicant in rats in vivo, and in vitro produces comparable morphological changes in rat testicular Sertoli-germ cell cocultures. m-Dinitrobenzene is metabolized both in vivo and in the in vitro system to m-nitroaniline m-nitroaniline and m-nitroacetanilide. These metabolites do not provoke testicular toxicity in vivo or in vitro. We have therefore proposed a pathway for the metabolism of m-dinitrobenzene to m-nitroaniline and m-nitroacetanilide, which involved the intermediate m-nitrosonitrobenzene (1-nitroso-3-nitrobenzene, NNB). When tested, m-nitrosonitrobenzene, at equimolar doses to m-dinitrobenzene, produced similar morphological changes in the culture system to those exhibited by m-dinitrobenzene. However, m-nitrosonitrobenzene produced a greater toxicity than did m-dinitrobenzene (as measured by germ cell detachment). When the intracellular thiol levels were reduced in the cocultures pretreated with diethyl maleate, the toxicity of both m-dinitrobenzene and m-nitrosonitrobenzene was enhanced. In contrast, pretreatment of cocultures with agents known to increase cellular thiol (cysteamine) or scavenge reactive intermediates (cysteamine or ascorbate) reduced the toxicity of m-dinitrobenzene and m-nitrosonitrobenzene. We propose that m-dinitrobenzene requires metabolic activation before it can exert its toxicity to Sertoli cells, and it appears that the toxic species is m-nitrosonitrobenzene or a further metabolite of m-nitrosonitrobenzene.

Animals↗
PubMed1990

The use of rat in vitro fertilization to detect reductions in the fertility of spermatozoa from males exposed to ethylene glycol monomethyl ether.

An in vitro fertilization (IVF) assay sensitive enough to detect changes in the fertilizing capacity of spermatozoa would be a useful tool with which to investigate the action of testicular toxicants. A known testicular toxicant, ethylene glycol monomethyl ether (EGME), was used to induce specific lesions in the germinal epithelium so that the ability of a rat IVF system to detect changes in fertility could be tested. Male rats were given single, oral doses of 50, 100, and 200 mg EGME/kg. Spermatozoa were recovered from the cauda epididymides of these males at intervals after treatment; their fertility was assessed using IVF, and the testes were processed for histologic examination. The fertility of the control males was consistently greater than 65%. Spermatozoa from males treated with EGME had reduced fertility at specific times after dosing. Thus, after 50 mg EGME/kg there was reduced fertility at 5 weeks; after 100 mg EGME/kg there was reduced fertility at 3.5, 4.5, 5, 6, and 6.5 weeks, and after 200 mg EGME/kg there was reduced fertility at 2 and 3 weeks, between 4.5 and 6 weeks, and at 7 weeks. This corresponded to damage to the elongated spermatids (2, 3, and 3.5 weeks), pachytene spermatocytes (4.5 to 6 weeks), and leptotene and preleptotene spermatocytes (7 weeks). This accords well with the data from serial breeding trials and reports of histologic damage after exposure to EGME. Therefore, using IVF it was possible to detect EGME-induced changes in fertilizing capacity which correlated closely with observations of testicular damage. It was also possible to demonstrate a clear dose response to EGME.

Animals↗
PubMed1989

The effects of 1,3-dinitrobenzene and mono-(2-ethylhexyl)phthalate on hormonally stimulated lactate and pyruvate production by rat Sertoli cell cultures.

Lactate and pyruvate production by rat Sertoli cell cultures was measured after treatment with two toxicants (1,3-dinitrobenzene, DNB; mono-(2-ethylhexyl)phthalate, MEHP) in the presence or absence of follicle-stimulating hormone (FSH) or dibutyryl-cAMP (dbcAMP). 1,3-DNB together with FSH or dbcAMP produced increases in media lactate and pyruvate concentrations significantly greater than those induced by individual treatments. MEHP in conjunction with either hormone also produced greater increases in lactate concentrations compared with separate additions. However, MEHP produced a significant diminution in the hormonal stimulation of pyruvate secretion. Thus, 1,3-DNB appears to act independently of these hormones in stimulating the secretion of both metabolic products, whereas MEHP interferes with the hormonal stimulation of pyruvate (but not lactate) production.

Animals↗
PubMed1988

Effect of mono-(2-ethylhexyl)phthalate on follicle-stimulating hormone responsiveness of cultured rat Sertoli cells.

Mono-(2-ethylhexyl)phthalate (MEHP) is one of a number of phthalate esters known to damage the rat testis with the Sertoli cell as its target. These effects can be modeled using primary testicular cell cultures. Stimulation of rat Sertoli cells by follicle-stimulating hormone (FSH) results in an increase in release of cAMP into the culture medium. However, cultures pretreated with MEHP (10(-7)-10(-4) M) showed a dose-related reduction in FSH-stimulated cAMP production (maximally greater than 50%), suggesting that MEHP is interfering with the FSH receptor-adenyl cyclase system. Detailed investigations of the system were conducted utilizing forskolin and choleratoxin, which both stimulate adenyl cyclase but bypass the FSH receptor to produce an increase in cAMP secretion. Cultures pretreated with MEHP (10(-9)-10(-5)M) showed no reduction in either forskolin- or choleratoxin-stimulated cAMP production. However, at low doses (10(-8)-10(-6)M) MEHP produced a potentiation (up to three times) of both forskolin- and choleratoxin-stimulated cAMP secretion, but gave slight inhibition at 5 X 10(-5) and 10(-4) M. These data indicate that MEHP produces a perturbation at the level of the FSH receptor, causing an inhibition of FSH action. This finding may be related to the age-dependent toxicity of the compound, since FSH is critical for the initiation of spermatogenesis in young animals, but is not necessary for the maintenance of spermatogenesis in adults. Thus an effect on FSH responsiveness in vitro may provide an indication of the mode of action of MEHP in vivo.

Animals↗
PubMed1988

The production of lactate and pyruvate as sensitive indices of altered rat Sertoli cell function in vitro following the addition of various testicular toxicants.

Lactate and pyruvate are hormonally stimulated products of the Sertoli cell, which are essential for germ cell survival. The utility of measuring these products as indices of Sertoli cell function was examined using toxicants targeted to this cell type. Hence, 1,3-dinitrobenzene (1,3-DNB; 10(-6) - 10(-4) M), and mono-(2-ethylhexyl)phthalate (MEHP; 10(-8) - 10(-4) M) were tested in rat Sertoli cell cultures. Both compounds produced significant dose-related increases (maximally three- to fourfold) in lactate concentrations in the culture medium. Only 1,3-DNB produced significant dose-related increases (up to eight- to ninefold) in pyruvate concentrations. All increases occurred within 24 hr of exposure, with the earliest changes occurring within 1-2 hr. The specificity of the responses was examined by comparison with the nontoxic isomers, 1,2 and 1,4-DNB, and the parent compound of MEHP, di-(2-ethylhexyl) phthalate and its inactive metabolite, 2-ethylhexanol. None of these compounds showed significant effects on lactate or pyruvate production. The spermatocyte toxicant, ethylene glycol monomethyl ether (EGME), and its major metabolite, methoxyacetic acid (MAA), were also tested. EGME had no effect on lactate or pyruvate production, and MAA produced a decrease in lactate concentration only at the maximum dose employed (5 mM). These results show that dose-related increases in lactate production were only observed for the two Sertoli cell toxicants, and only for 1,3-DNB in the case of pyruvate production. Inactive isomers, metabolites, and germ cell toxicants did not produce these changes. Thus, lactate (and pyruvate) production by rat Sertoli cell cultures may be a sensitive index of altered function as induced by 1,3-DNB and MEHP.

Acetates↗
PubMed1988

Trifluoroethanol and its oxidative metabolites: comparison of in vivo and in vitro effects in rat testis.

Trifluoroethanol (TFE) and trifluoroacetaldehyde (TFALD) produced a reduction in testis weight 3 days after a single oral dose of 10 mg/kg. In contrast, administration of trifluoroacetic acid (TFAA) caused no observable testicular effects. Reduction in testis weight was accompanied by morphological changes, involving specific damage to pachytene and dividing spermatocytes, and round spermatids. In an in vitro Sertoli/germ cell co-culture system, only TFALD was found to produce dose-related effects at concentrations of 10(-3) and 10(-4) M. There was increased germ cell loss from the cultures, particularly loss of pachytene and dividing spermatocytes, accompanied by leakage of the pachytene spermatocyte marker enzyme, lactate dehydrogenase-X. TFE and TFAA did not produce these effects in the culture system at concentrations equimolar with TFALD. These results suggest that TFALD may play a critical role in the development of the testis lesion seen with TFE in vivo. The effects seen both in vivo and in vitro were remarkably similar to those previously reported for another substituted alcohol and its metabolites, ethylene glycol monomethyl ether. It is postulated that the two series of compounds may have a similar mode of action on rat testis.

Acetaldehyde↗
PubMed1988

A comparison of the effects of the three isomers of dinitrobenzene on the testis in the rat.

Sexually mature Alpk/AP (Wistar derived) rats were killed 5 days after a single oral dose of 50 mg/kg of the 1,2-, 1,3-, or 1,4-isomers of dinitrobenzene. Testis weight reductions accompanied by testicular lesions were observed in the animals dosed with 1,3-dinitrobenzene (1,3-DNB) while the 1,2- and 1,4-isomers were without effect on the testis. However, 1,4-dinitrobenzene, but not 1,2-dinitrobenzene, was of a potency similar to that of 1,3-DNB in producing cyanosis and splenic enlargement in these animals, indicating that different mechanisms are probably responsible for these two toxic effects. In a subsequent study the pathogenesis of the testicular damage resulting from a single oral dose of 5, 10, 15, or 25 mg 1,3-DNB/kg was studied in sexually mature rats. Animals were killed 6, 12, 24, 48, and 96 hr after dosing and a detailed histopathological examination of the testes and selected tissues was made. At 12 hr after a single oral dose of 25 mg/kg, 1,3-DNB produced testicular lesions limited to Stages VIII to XI of the spermatogenic cycle. By 24 hr widespread Sertoli cell damage was evident and in some tubules was associated with degeneration of primary spermatocytes. Ultrastructural examination at this time confirmed that there were effects on Sertoli cells in the absence of germ cell damage. Similar effects were seen 48 hr after a single oral dose of 15 mg 1,3-DNB/kg. Doses of 5 or 10 mg 1,3-DNB/kg were without effect on the testis. The Sertoli cell is implicated as the prime target for the toxic action of 1,3-DNB with germ cell damage a secondary event.

Administration, Oral↗
PubMed1987

Comparison of the in vivo and in vitro testicular effects produced by methoxy-, ethoxy- and N-butoxy acetic acids in the rat.

Methoxy-, ethoxy- and n-butoxy acetic acids, known urinary metabolites of the corresponding alkoxyethanol solvents, were administered by gavage to rats as a single oral dose equimolar with 500, 250 or 100 mg 2-methoxyethanol/kg body weight. Testicular weight and morphology were monitored over a 14-day period post-treatment. Methoxyacetic acid (MAA) was the only compound which produced a significant decrease in testicular weight. Histological examination of the testes from treated animals indicated that MAA at all doses and ethoxyacetic acid (EAA) at the highest dose, produced damage specific to spermatocytes undergoing meiotic maturation and division (particularly stages XIII-XIV) within 24 h of treatment. n-Butoxyacetic acid (BAA) had no discernable effect on the testis at any dose level or time, although there was evidence of haematuria produced by the compound. Addition of MAA, EAA and BAA to testicular cell cultures at concentrations approximately equivalent to the steady state plasma levels of MAA determined after a testicular toxic dose (500 mg/kg) of methoxyethanol (5 mM) produced a specific loss of pachytene spermatocytes (the target population in vivo) from the system by MAA and EAA (MAA greater than EAA). BAA did not produce any specific changes to testicular cell populations in vitro. Thus the production of testicular toxicity by alkoxyacetic acids diminishes with increasing chain length, and a good correlation exists between in vivo and the in vitro system.

Acetates↗
PubMed1985

The role of metabolism in 2-methoxyethanol-induced testicular toxicity.

The role of metabolism in 2-methoxyethanol (ME)-induced testicular toxicity has been investigated with Sprague-Dawley rats. Following administration of [14C]ME (250 mg/kg, ip) to a group of animals, there was evidence of testicular damage, identified as depletion of the spermatocyte population. Radioactivity detected in urine over 48 hr after treatment accounted for 55% of the dose. The major urinary metabolites were identified by HPLC and isotope dilution analysis, as methoxyacetic acid (MAA) and methoxyacetylglycine (accounting for 50 to 60% and 18 to 25%, respectively, of urinary radioactivity). Analysis of plasma revealed a rapid conversion of ME to MAA (t1/2 for disappearance of ME = 0.6 +/- 0.03 hr) and gradual clearance of radioactivity (t1/2 = 19.7 +/- 2.3 hr). Pretreatment of animals with pyrazole (400 mg/kg, ip) 1 hr prior to [14C]ME dosing gave complete protection against the testicular toxicity of ME. Radioactivity detected in the urine from the pyrazole-pretreated groups over 48 hr (18%) was significantly lower than in the ME-only group. The major radioactive peak co-chromatographed with ME (30 to 36% of the total urinary radioactivity). MAA and methoxyacetylglycine were not major metabolites. Analysis of plasma revealed almost complete inhibition of the conversion of ME to MAA (t1/2 for disappearance of ME = 42.6 +/- 5.6 hr, clearance of radioactivity t1/2 = 51.0 +/- 7.8 hr). The results demonstrate that metabolic activation is required for 2-methoxyethanol to exert toxicity to the male reproductive system.

Acetates↗
PubMed1984

The morphological development of glycol ether-induced testicular atrophy in the rat.

The testicular effects of daily oral dosing with two glycol ethers--either ethylene glycol monomethyl ether (EGM) or monoethyl ether (EGE) were studied in the prepubertal rat by histological examination of the testes. Over the 11-day dosing period studied, EGM was found to produce testicular damage at dose levels of and in excess of 100 mg/kg/day with a no-effect level at 250 mg/kg/day. The findings at sequential time intervals throughout the dosing period indicated that primary spermatocytes undergoing pachytene development constituted the initial and major site of morphological damage. Within this population, differential sensitivity was demonstrated depending on the precise stage of meiotic maturation. A consistent order of spermatocyte susceptibility emerged from the results: dividing spermatocytes (Stage XIV) greater than early-pachytene spermatocytes (Stages I-III) greater than late-pachytene spermatocytes (Stages IX-XIII) greater than midpachytene spermatocytes (Stages IV-VIII). Leptotene/zygotene spermatocytes and Step 1 spermatids also showed degenerative changes but only after prolonged dosing at high-dose levels. The significance of the findings with respect to mechanisms of cellular toxicity in the testis is discussed.

Animals↗
PubMed1984

Testicular toxicity produced by ethylene glycol monomethyl and monoethyl ethers in the rat.

Ethylene glycol monomethyl ether (EGME) and ethylene glycol monoethyl ether (EGEE) were administered orally to young male rats at doses varying from 50 to 500 mg/kg/day and 250 to 1000 mg/kg/day for EGME and EGEE, respectively, for 11 days. At sequential times animals were killed and testicular histology examined. The initial and major site of damage following EGME treatment was restricted to the primary spermatocytes undergoing postzygotene meiotic maturation and division. EGEE produced damage of an identical nature, but a larger dose was required to elicit equivalent severity (500 mg EGEE/kg being approximately equivalent to 100 mg EGME/kg). Additionally, within the spermatocyte population, differential sensitivity was observed depending on the precise stage of meiotic maturation: dividing (stage XIV) and early pachytene (stages I-II) greater than late pachytene (stages VIII-XIII) greater than mid-pachytene (stages III-VII). Equivalent doses of methoxyacetic acid (MAA) and ethoxyacetic acid (EAA) gave injury similar to the corresponding glycol ether. When animals were pretreated with inhibitors of alcohol metabolism followed by a testicular toxic dose of EGME (500 mg/kg), an inhibitor of alcohol dehydrogenase (pyrazole) offered complete protection. Pretreatment with the aldehyde dehydrogenase inhibitors disulfiram or pargyline did not ameliorate the testicular toxicity of EGME. In mixed cultures of Sertoli-germ cells, MAA and not EGME produced effects on spermatocytes analogous to that seen in vivo, at concentrations approximately equivalent to steady-state plasma levels after a single oral dose of EGME (500 mg/kg). It would seem likely that a metabolite (MAA or possibly methoxyacetaldehyde) and not EGME is responsible for the production of testicular damage.

Acetates↗