John W. Laskey

Effects of in vitro cadmium exposure on ovarian steroidogenesis in rats.

The purpose of this study was to evaluate the direct effect(s) of in vitro cadmium (Cd) exposure on steroidogenesis in rat ovaries during different reproductive states. Sprague‐Dawley rats were killed on the day of proestrus, or on gestation day 6 or 16. Ovaries were removed, placed in medium and minced. Culture from each ovary was incubated with Cd2+ ions in concentrations of 0, 100, 500, 1000, 1500, or 2000 μM. One‐hour whole‐ovary production of progesterone (P4), testosterone and estradiol (E2) in culture medium was evaluated in the absence and presence of human chorionic gonadotropin (hCG) or hCG plus pregnenolone by specific radioimmunoassay. Under in vitro Cd exposure the most affected were productions of P4 and testosterone in proestrus rats and less in pregnant dams, whereas E2 was not affected at all. Cadmium appears to interfere with the ovarian steroidogenic pathway in rats at more than one site. Copyright

Effect of benomyl on reproduction in the male rat

Adult Sprague-Dawley male rats (65 days of age) received 10 daily treatments of 0, 200 or 400 mg benomyl/kg/day by gavage. Body weight, tissue weights, total epididymal sperm counts and sperm concentration from the vas deferens were measured 14 days after the last treatment. Testicular histology was evaluated in the 0 and 400 mg/kg/day groups. Significant findings included 35-48% depressions in the total epididymal sperm counts and in the vas deferens sperm concentrations in adult animals treated with 200 or 400 mg/kg/day. Histological evaluations of testicular sections from 6 adult animals in the 400 mg/kg/day group indicated a slight to moderately severe hypospermatocytogenesis in 2 animals and a slight to severe generalized hypospermatogenesis in 2 animals. Caudal epididymis weight were significantly (P less than 0.05) depressed with benomyl treatment. No treatment effects were found in body weight, liver, kidney, tests, or seminal vesicle weights.

Use of the fungicide carbendazim as a model compound to determine the impact of acute chemical exposure during oocyte maturation and fertilization on pregnancy outcome in the hamster

Early pregnancy loss due to acute chemical exposure is difficult to detect and essentially impossible to characterize in humans. Here we use a hamster animal model to identify early pregnancy loss due to an acute chemical exposure to the female during the perifertilization interval. The fungicide carbendazim (methyl 1H-benzimidazole-2-carbamate), a microtubule poison with antimitotic activity, was selected as a model compound because it would be expected to perturb microtubule-dependent events occurring in the oocyte during meiotic maturation and fertilization. Such effects would likely lead to aneuploidy in the zygote with subsequent early pregnancy loss. Female hamsters were given a single oral dose of carbendazim during meiosis I (the afternoon of proestrus) prior to breeding, or during meiosis II (the morning of estrus) following overnight breeding. Pregnancy outcome was assessed on Day 15 (the afternoon before parturition). When given during during meiosis I, carbendazim treatment (750 or 1000 mg/kg body weight) significantly reduced the percentage of pregnant hamsters. In those animals that became pregnant, the average number of live pups was significantly lower at all dosages of carbendazim used (250, 500, 750, and 1000 mg/kg), an effect attributable to both preimplantation and early postimplantation losses. When given early on the morning of estrus, shortly before and during fertilization (0500 or 0600 hr), carbendazim treatment (1000 mg/kg) produced a similar decrease in litter size. This effect disappeared when carbendazim was administered at a slightly later time (0800 or 0900 hr), after the microtubule-dependent events of fertilization have occurred. These results demonstrate that a single exposure to a microtubule poison such as carbendazim at critical times, coincident with microtubule-dependent meiotic events, can result in very early pregnancy loss. Such loss was readily measurable in this animal model and serves as the basis for further mechanistic studies which would be impossible to conduct in humans.

Some Effects of Lifetime Parental Exposure to Low Levels of Tritium on the F2 Generation

Rats were continuously exposed to constant activities of tritium (HTO) in drinking water from conception of the F1 generation through delivery of the F2. The activities employed were 0.01, 0.10, 1....

Low iron diet and parenteral cadmium exposure in pregnant rats: the effects on trace elements and fetal viability.

The effects of latent iron deficiency combined with parenteral subchronic or acute cadmium exposure during pregnancy on maternal and fetal tissue distribution of cadmium, iron and zinc, and on fetal viability were evaluated. Timed-pregnant Sprague-Dawley rats were fed on semisynthetic test diets with either high iron (240xa0mgxa0kg) or low iron (10xa0mgxa0kg), and concomitantly exposed to 0, 3 or 5xa0mg cadmium (as anhydrous CdCl2) per kilogram body weight. Animals were exposed to cadmium from gestation day 1 through 19 by subcutaneously implanted mini pumps (Subchronic exposure) or on gestation day 15 by a single subcutaneous injection (Acute exposure). All rats were killed on gestation day 19. Blood samples, selected organs and fetuses were removed and prepared for element analyses by atomic absorption spectrometry. Low iron diet caused decreases in maternal body weight, maternal and fetal liver weights, placental weights and tissue iron concentrations. By cadmium exposure, both subchronic and acute, tissue cadmium concentrations were increased and the increase was dose-related, maternal liver and kidney zinc concentrations were increased, and fetal zinc concentration was decreased. Cadmium concentration in maternal liver was additionally increased by low iron diet. Acute cadmium exposure caused lower maternal body and organ weights, high fetal mortality, and decreased fetal weights of survivors. In conclusion, parenteral cadmium exposure during pregnancy causes perturbations in essential elements in maternal and fetal compartments. Acute cadmium exposure in the last trimester of gestation poses a risk for fetal viability especially when combined with low iron in maternal diet.

Statin drugs markedly inhibit testosterone production by rat Leydig cells in vitro: Implications for men

Statin drugs lower blood cholesterol by inhibiting hepatic 3-hydroxy-3-methylglutaryl-Coenzyme-A reductase. Statins are known to inhibit sterol production in the testis, but effect of statins on testosterone production has not been studied critically in vitro and clinical data are controversial. We measured 18-h testosterone production in vitro, using highly purified rat Leydig cells exposed to atorvastatin, mevastatin, or simvastatin and also determined if statin-induced inhibition of testosterone production could be bypassed with substrate distal to cholesterol. Statins had no effect on testosterone production during culture without LH. However, with 10ng/mL LH, testosterone production was ≥12-fold higher and markedly inhibited (-40%) by ≥0.3μM statin. Leydig cells provided sub-saturating pregnenolone or progesterone to bypass the site of statin action, maintained LH-stimulated testosterone production at or above amounts observed with LH stimulation and no statin. Pregnenolone resulted in greater testosterone production, but LH responsiveness was lost. With progesterone, LH responsiveness was maintained.

Some effects of chronic tritium exposure during selected ages in the rat.

LASKEY, J. W., AND BURSIAN, S. J. Some Effects of Chronic Tritium Exposure during Selected Ages in the Rat. Radiat. Res. 67, 314-323 (1976). To assess the implication of age at the time of exposure to chronic irradiation, rats were exposed to constant tritium (HTO) activities of 10 yCi/ml of body water for 42 days beginning either on the first day of pregnancy or at birth, or at 42 days or 74 days of age. This activity level provided a calculated whole-body dose rate of 3 rad/day. The indicators of radiobiologic damage employed were reproductive, endocrine, and neurochemical parameters and were assessed at 49, 120, or 300 days of age. A significant reduction in the testes weight and sperm content in rats exposed either from the first day of pregnancy or birth was evident upon examination at 49 days of age. Females exposed from the first day of pregnancy had a significant reduction in their F2 litter size and an increase in the number of resorbed embryos. Analysis for norepinephrine (NE) and dopamine (DA) concentration in the brain and follicle-stimulating hormone (FSH) concentration in the pituitary was performed at 49 and 300 days. Rats exposed from conception had increases in NE and DA and a decreased FSH concentration when examined at 49 days of age. When examined at 300 days of age all groups had decreased NE and DA concentrations. At the same time, all treatment groups showed increased FSH concentration with the groups exposed later in life showing the greatest increase. From the parameters examined all age groups showed some effects due to the HTO exposure, but the group most sensitive to the effects of chronic irradiation was the

The use of cultured ovarian fragments to assess toxicant alterations in steroidogenesis in the sprague-dawley rat

This study was conducted to determine the utility of using steroid production by cultured ovarian fragments to assess toxicant-induced alterations in ovarian steroidogenesis in Sprague-Dawley rats. To this end, serum steroid concentration and steroid production (progesterone (P4), testosterone (T), estradiol (E2)) by cultured ovarian fragments is described during a normal 4-day estrous cycle. This culture system was then used to profile the effects of aminoglutethimide shown to have two sites of steroidogenic inhibition, side chain cleavage enzyme and aromatase. LH, FSH, P4, and E2 concentrations in serum during the 4-day estrous cycle confirmed that described in the literature for untreated rats. All of the steroids measured had peak production levels during proestrus. The patterns of P4 and E2 production by the ovaries in an unstimulated culture mimics that seen in serum. Stimulation with hCG (100 mIU/mL) after the initial 1 h culture tends to even out the production of P4, while T production rises faster and peaks earlier. The pattern and levels of estradiol production in hCG-stimulated cultures are very similar to those in the unstimulated culture, both in pattern and in production levels. When cultured ovarian fragments from proestrous rats were treated in vitro with aminoglutethimide (1 to 16 microM), the pattern of steroid production that characterized the inhibitory effects were similar to those reported in the literature using isolated cell culture procedures. This pattern showed a rapid decrease in E2 production (IC50 of 2.43 microM), a concurrent rise in T production, and a decrease in P4 production (IC50 of 15.5 microM). This culture system is an appropriate system to rapidly assess toxicant effects on ovarian steroidogenesis following in vivo or in vitro exposure.

Hatch Weight Selection: Effect on Post-Hatch Growth in the Japanese Quail 'Coturnix Coturnix Japonica'

The post-hatch growth of Japanese quail, weight selected at hatch, was investigated. The quail were grouped according to hatch weight as follows: Group I, 5.5-6.2 g; Group II, 6.3-7.0 g; and Group III, 7.1-7.6 g. Group III quail were 25 and 12% heavier at hatching than Group I and II quails, respectively, and reached a mature body weight which was 38 and 12% heavier than Group I and II quails, respectively. Gompertz growth parameters were not different in any of the groups. Feed and water consumption (g/kg body weight) rates were not significantly different among the three groups.

Some Aspects of Brain Neurochemistry after Intrauterine Exposure to Tritium

Rats were continuously exposed to tritiated water (0, 1, 10 and 100 muCi HTO/ml body water) from conception to birth. Calculated, cumulative whole-body doses to the embryo and foetus were approximately 0, 6-6, 66 and 660 rad. The levels of several enzymes and established or presumptive central nervous system neurotransmitters were examined postnatally in whole brains. These were norepinephrine (NE), dopamine (DA), acetylcholinesterase (AChE) and monoamine oxidase (MAO). Intrauterine exposures to doses as low as 66 rad produced measurable and persistent decreases in brain weight and increases in NE concentrations at 21 and 45 days postnatally. No differences from control values were seen in the rate of turnover of NE or the concentrations of DA, AChE or MAO at 45 days. Exposure in utero to 6-6 rad produced no detectable postnatal effects on the brain neurochemical parameters measured.