Susceptibility to cyclophosphamide and thalidomide of fetal rat limb buds grafted in athymic (nude) mice

Limb buds of day-14 rat fetuses were cut into pieces and transplanted into athymic (nude) mice. On the 7th and 9th days after grafting, the host nude mice were given cyclophosphamide intraperitoneally (10–120 mg/kg) or thalidomide orally (30–240 mg/kg). On the 20th day, the grafted tissue was examined maeroscopically and histologically. The grafts maintained in vehicle-treated nude mice showed considerable growth and tissue differentiation similar to in vivo. Growth and histogenesis of the grafts were significantly inhibited by treatment with cyclophosphamide ( 20 mg/kg). There was no indication that treatment with thalidomide ( 240 mg/kg) adversely affects the development of grafted limbs. Thus, the susceptibility of transplanted rat limb buds to these two human teratogens was identical to the susceptibility of living rat fetuses. The heterotransplantation method of embryonic tissues may be of potential use for the study of teratogenic mechanisms and for the screening of human teratogens.     

Role of γ-glutamyltranspeptidase and β-lyase in the nephrotoxicity of hexachloro-1,3-butadiene and methyl mercury in mice

Male Swiss OF1 mice received a single oral dose of either 80 mg/kg hexachloro-1,3-butadiene (HCBD) or 80 mg/kg methyl mercury (MeHg). Examination of cryostat kidney sections stained for alkaline phosphatase (APP) revealed damage to about 50% of the proximal tubules after 8 h. Pretreatment with the γ-glutamyltranspeptidase (γ-GT) inactivator AT-125 (Acivin, 50 mg/kg i.p., plus 50 mg/kg p.o., reduced the number of damaged tubules by 59 and 58% in mice treated with HCBD and MeHg, respectively. Pretreatment with the two β-lyase inhibitors, amino-oxyacetic acid (AOAA, 3 × 100 mg/kg p.o.) and -propargylglycine (PPG, 300 mg/kg i.p. plus 300 mg/kg p.o), reduced HCBD nephrotoxicity by 46 and 59%, respectively, but did not protect against MeHg nephrotoxicity. The results support a role for γ-GT and β-lyase in the mouse renal toxicity of HCBD and implicate γ-GT but not β-lyase in MeHg-induced nephrotoxicity in mice.     

Effects of Δ-tetrahydrocannabinol and mescaline on self-stimulation

The effects of two psychotomimetic drugs, Δ⁹-tetrahydrocannabinol (Δ⁹-THC) and mescaline on intrahypothalamic self-stimulation behavior were investigated to test their action on the central reward system. Rats were trained to press a lever to receive intracranial electric stimulation through a set of stereotaxically implanted bipolar electrodes in the posterior lateral hypothalamus. Both Δ⁹-THC (1–25 mg/kg in 4% Tween in saline) and mescaline (6.3–25 mg/kg) injected i.p. caused a decrease in self-stimulation responding. A rough doseresponse relation was observed with both the drugs at these doses. Following repeated injection of a particular daily dose, tolerance developed to both these drugs within 9 days. However, no cross-tolerance was observed between these two drugs in this schedule.     

Effect of lindane on nitroreductase and dechlorinase enzyme activity in the gastrointestinal tract

A previously reported acceleration of parathion metabolism in the gastrointestinal (GI) tract of lindane-pretreated rats could have been due to either a prolonged residence time of parathion or increased GI nitroreductase activity or both. Thus to determine the effect on GI nitroreductase and dechlorinase activity, 20 mg/kg lindane or 535 mg/kg neomycin were administered daily, by gavage, to weanling F-344 rats. Enzyme activity in the small intestine and cecum were assayed after 2 weeks and 5 weeks of treatment. Neomycin treatment inhibited the activity of both enzymes in the cecum but had no significant effect on enzyme activity in the small intestine, suggesting the presence of mucosal nitroreductase and dechlorinase in the small intestine. In contrast, lindane, which had no effect on enzyme activity in the cecum, significantly increased nitroreductase activity in the small intestine after treatment for 5 weeks. This increased nitroreductase may account for the previously reported lindane-parathion interaction and could influence the metabolism, toxicity, and risk assessment of many other environmental nitro-compounds that become toxic, mutagenic or carcinogenic upon reduction of their nitro-groups.     

Development of EEG seizure activity during and after chronic ketamine administration in the rat

Daily assessment of gross behavior and periodic EEG brain wave activity was performed in rats receiving daily ketamine administration for 1,2 and 3 months. Three groups were used for these studies; the first group received 80 mg/kg ketamine intraperitoneally (i.p.), a dose which produces a cataleptoid-like behavior and characteristic EEG hypersynchronous patterns; the second group received 30 mg/kg ketamine i.p. which induces behavioral excitation followed by ataxia and desynchronized EEG; the third group received saline control with no change in EEG or behavior noted. Abnormal spike and hypersynchronous bursting activity appeared in both the amygdala and dorsal hippocampus during the course of chronic administration of both the low and high dose of ketamine. The incidence of abnormal brain wave spiking was approximately 50% with 3 out of 5 animals demonstrating abnormal brain wave activity at the high dose and 1 out of 3 at the lower dose. During the course of the three months' administration of both the low and high dose of ketamine there was no evidence of tolerance or potentiation of the drug effect based on EEG or behavioral criteria. Withdrawal of the drug for 5 days following three months of treatment resulted in the appearance of a progressive increase in epileptiform activity without gross behavioral manifestations. The abnormal spike and slow wave EEG activity was not correlated with an observable abnormality in behavior.     

The induction of dominant lethal mutations upon chronic administration of khat (Catha edulis) in albino mice

The mutagenicity of a methanolic extract of khat has been evaluated on male germ cells using the dominant lethal test in albino mice. An aqueous solution of khat extract was administered orally in doses of 50, 100 and 200 mg/kg body wt., respectively, to 3 different groups of male mice for a period of 6 weeks. At the end of treatment each male mouse was allowed to mate with 2 different groups of 3 females each, on 2 consecutive weeks. These females were necropsied on the 13th day of their presumptive mating, and the number of implants in each female and the ratio of live and dead embryos were determined. The results of this study showed that the treatment of male mice over a period of 6 weeks produced a dose-dependent reduction in the rate of fertility in the first week after mating, which was irreversible in the second week at the highest dose (200 mg/kg). Khat extract also induced post-implantation loss during the first week following treatment. However, a comparison of the results of the first and second weeks showed a reversible pattern of dominant lethality.     

Effects of amethopterin (methotrexate) on the evolution of pregnancy in rats.

Amethopterin (4-amino-N-10-methyl-glutamic acid) was given to pregnant rats in varying doses at different periods of gestation to evaluate its effects upon both the mother and the fetoplacental unit. The maternal organism is more sensitive to this drug at days 14 to 17 than at a larger stage of gestation. When administered to rats from day 14 to day 18 of pregnancy the drug is capable of inducing a series of deleterious effects: maternal weight loss, resorption, abortion or hypotrophy of fetuses. Day 16 appears to be a critical moment in the evolution of rat pregnancy, after which injection of amethopterin does no longer impair fetoplacental growth. Before this date, the drug directly inhibits fetal weight gain, whereas the sensitivity of the placenta is only transient at day 16 resulting in maximum weight decrease of this organ 24 h later. Its action on rat pregnancy follows a direct dose-effect relationship reflecting increasing damage to the products of conception (resorption, abortion and hypotrophy).     

Cocaine toxicity in cultured rat hepatocytes

Cocaine hydrochloride was added to primary cultures of hepatocytes isolated from naive and phenobarbital-induced (80 mg/kg i.p. for 3 d) Sprague-Dawley rats. Cocaine was cytotoxic, as measured by lactate dehydrogenase release, to cells from naive rats in concentrations of 1 mM or greater. Phenobarbital induction greatly increased the cytotoxic potency of cocaine in vitro, with nearly complete loss of cell viability at cocaine concentrations in culture as low as 0.01 mM. The addition of 10 μM SK&F-525-A to the cultures blocked cocaine cytotoxicity in cells from both naive and phenobarbital-induced rats. These results suggest that the metabolic pathways leading to cocaine hepatotoxicity identified in the mouse also exist in the rat hepatocyte.     

Cardiovascular effects of cholinergic agents in the ventral-lateral midbrain periaqueductal gray of the rat

Local injection of the cholinergic agonist carbachol (1–5 nmol) into the ventral lateral periaqueductal gray region of the midbrain produced a dose-dependent bradycardia with minimal effects on blood pressure in the urethane-anesthetized rat. The decrease in heart rate was maximal in the region of the nuclei of the third and fourth cranial nerves. Intravenous injection of carbachol (5 nmol) had little effect on the heart rate. Injection of (−)-nicotine (5 nmol) into this region of the brain produced a slight, but significant, increase in heart rate. Pretreatment with an intracranial injection of atropine greatly reduced the bradycardia response, whereas local injection of mecamylamine or hexamethonium had no effect. The bradycardia resulting from cholinergic stimulation in this area of the brain appears to result from an enhanced vagal influence on the heart, as pretreatment with intravenous atropine methyl nitrate (1 mg/kg) prevented the carbachol-induced bradycardia. The possible physiological significance of this response is discussed.     

Higher susceptibility of taurine-deficient rats to seizures induced by 4-aminopyridine

The susceptibility of rats made deficient of taurine by treatment with guanidinoethane sulfonate (GES), to seizures induced by 4-aminopyridine was examined. Guanidinoethane sulfonate, at a concentration of 1% was administered to pregnant rats, in the drinking water 2–3 days prior to delivery and the treatment was continued during nursing. Pups were weaned to the same treatment until 6 weeks of age. This treatment decreased levels of taurine in the cerebral cortex by 70%. 4-Aminopyridine was injected intraperitoneally at doses ranging from 4–7 mg/kg. Taurine-deficient rats showed a greater susceptibility to seizures, as demonstrated by a lowered latency for clonic seizures, an increased incidence of tonic seizures and a higher postseizure mortality. These results suggest an involvement of endogenous taurine in nervous excitability.     

Enhancement of a diazepam withdrawal symptom by bicuculline and yohimbine

The role of the GABA system in producing a pentylenetetrazol-like interoceptive discriminative stimulus during withdrawal from diazepam was investigated in rats by determining the sensitivity of this system to GABAergic drugs before and after chronic treatment with diazepam. Food-restricted rats were trained to obtain a reward of food by responding on one lever following an injection of pentylenetetrazol (PTZ; 20 mg/kg) and the other lever following an injection of saline (1 ml/kg). After rats had acquired this discrimination, the effectiveness of Ro 15–1788, bicuculline and yohimbine to substitute for pentylenetetrazol was determined. Prior to chronic treatment with diazepam, rats selected the appropriate lever for saline after Ro 15–1788 and the appropriate lever for pentylenetetrazol after bicuculline (0.04–2.5mg/kg) or yohimbine (0.16–5.0mg/kg). Although the selection of the appropriate lever for pentylenetetrazol was dose-dependent, full substitution for pentylenetetrazol was not obtained with either drug as larger doses of bicuculline produced convulsions while the rats began to select the appropriate lever for saline after larger doses of yohimbine (bell-shaped curve). Diazepam blocked the pentylenetetrazol-like interoceptive discriminative stimulus for bicuculline. The rats were then injected with diazepam (80mg/kg/8 hr) for 24 days. Upon termination of the administration of diazepam, the animals were tested for lever-selection following the administration of saline, Ro 15–1788 (10mg/kg), bicuculline (0.32, 0.64 and 1.25mg/kg) or yohimbine (0.16, 0.64 and 2.5mg/kg). After saline, 33% of the rats selected the appropriate lever for pentylenetetrazol whereas selection of this lever was enhanced after Ro 15–1788, bicuculline or yohimbine. Thus, either displacement of diazepam or further reduction of GABAergic activity increased the subjective effect of the withdrawal from diazepam. These data support the hypothesis that the chronic administration of diazepam produces a reduction in the activity of the GABA/benzodiazepine complex, which is manifested during withdrawal as a pentylenetetrazol-like stimulus.     

TCDD decreases brain inositol concentrations in the rat

A single dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) reduced significantly brain regional inositol levels in both the most TCDD-susceptible (Long-Evans; LD₅₀9.8 μg/kg) and the most TCDD-resistant (Han/Wistar; LD₅₀ > 7200 μg/kg) rat strain. The decrease emerged earlier in Long-Evans rats but was similar in magnitude at 8 days in both strains. There were some inconsistent and largely dose-independent changes in inositol-1- and inositol-4-monophosphate concentrations at 2 days. On day 8, a tendency towards reduced levels was seen especially in H/W rats. We conclude that TCDD reduces brain inositol levels presumably by inhibiting its synthesis by way of substrate deficit (hypoglycemia), but this effect does not appear to be causally related to the lethal action of TCDD.     

Teratogenic effects of carboplatin, an oncostatic drug, administered during the early organogenetic period in rats

In the preceding study, no teratological effects against rat fetuses were observed when carboplatin, an oncostatic platinum coordination complex, was dosed to their dams from days 7 to 17 of gestation at a dose level of 4 mg/kg/day. However, there are a few reports which show the teratogenic action of carboplatin injected from days 6 to 15 of pregnancy at a dose level of 6 mg/kg/day. In the present study, carboplatin was administered intravenously to pregnant female Crj: CD (Sprague-Dawley) rats from days 6 to 9 or 7 to 10 of gestation at a dose level of 6 mg/kg/day in order to know the teratogenicity of this drug. Carboplatin were highly embryolethal in dams when dosed from days 6 to 9 of gestation, but not in animals when injected from days 7 to 10 of pregnancy. Carboplatin also produced external, internal and skeletal anomalies in fetuses such as gastroschisis, dilatation of cerebral ventricles, cleft sternum, fused ribs, malformed thoracic vertebra when administered from days 6 to 9 of gestation, but not in conceptuses when dosed from days 7 to 10 of pregnancy. However, the delayed ossification which was ascribed to the fetal growth retardation was observed in rats treated with this drug during both administration periods. These results suggest that carboplatin is embryotoxic, inducing intrauterine death and congenital malformations in rats, when injected during the early stages of gestation including day 6 of pregnancy.     

Sensitivity to diethylstilbestrol-(DES)-induced abortions is influenced by the Whitten effect

Group-housed female mice, when introduced to a male, will undergo a synchronized estrous cycle with a characteristic pattern of mating where the majority of animals mate on the third day. This phenomenon is termed the Whitten effect. Exposure of pregnant mice to diethylstilbestrol (DES), a potent nonsteroidal estrogen, is capable of inducing premature parturition. The purpose of this study was to evaluate abortion induced by a single injection of DES on day 15 of gestation and compare the sensitivity depending on the day of mating. Initial observations confirmed that those animals that mated on day 3 were significantly more susceptible to DES-induced abortion than animals that mated on any other day. The possibility that this increase in sensitivity to abortion may be the result of differences in number or size of embryos at the time of DES exposure was examined. No significant difference was observed in the number of embryos at day 4 of gestation, at day 15 of gestation, or at birth. There was no difference in the weight of embryos at day 15 of gestation or at birth. A significant increase in the ratio of embryos between uterine horns was observed in the animals that mated on day 3 (ratio = 2.13) compared to animals mating on other days (ratio = 1.23 to 1.48). The cause of increased sensitivity to DES in animals that mated on day 3 is unclear. Our results may indicate that the induction of ovulation associated with the Whitten effect causes unequal embryo distribution leading to functional differences in sensitivity of the pregnancy to exogenous stimuli.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immediate and long-term effects of 3,4-methylenedioxymethamphetamine on serotonin pathways in brain of rat

In the rat, administration of the psychoactive analog of amphetamine 3,4-methylenedioxy-methamphetamine (MDMA), causes selective, pronouced decreases in markers of central serotonergic function. The time course of these neurochemical changes was examined in several serotonergic nerve terminal regions of the brain. Fifteen min after subcutaneous injection of MDMA (10 mg/kg), the enzymatic activity of tryptophan hydroxylase (the rate-limiting enzyme for the biosynthesis of serotonin) was significantly decreased in the frontal cortex; by 1 hr after the injection, the activity of tryptophan hydroxylase had significantly declined in the neostriatum, hippocampus and hypothalamus as well. Although extensive recovery had occurred by 2 weeks, the activity of the enzyme remained significantly depressed in most regions. Decline of the regional content of 5-hydroxytryptamine (5-HT) closely paralleled, but was usually preceded by, that of the enzyme. Concentrations of the primary metabolite of 5-HT, 5-hydroxyindoleacetic acid (5-HIAA), were less responsive: in most regions levels of 5-HIAA had significantly decreased by 3 hr, but not by 1 hr, following treatment. Markers of dopamine function were altered transiently but had returned to control values by 24 hr.

Administration of multiple doses of MDMA (5 doses over a 24-hr period) resulted in significant decreases in serotonergic parameters for up to 110 days after treatment. The rate and extent of recovery varied according to both the dose administered and the region examined. The persistence of these serotonergic deficits suggests that MDMA induced the destruction of serotonin-containing axon terminals.     

A teratogenicity study with amaranth in cats.

Cats of heterogeneous stock and in good health were given daily oral doses of 92, 187, or 264 mg amaranth/kg/day for a time period extending from 0–22 days before the onset of gestation to Days 61–62 of gestation (mean gestation period = 65 days). The pregnancies were timed by having controlled copulation of females that were in an estrous state which occurred spontaneously or was stimulated by gonadotropin treatment. Cesarean section was performed on Day 61 or 62 of gestation. Maternal values including body weight gain, number of corpora lutea, and incidences of pregnancy, abortion, and nonpregnancy showed no amaranth-related adverse effect. There was no evidence of embryotoxicity as evaluated from the data on total implants, ratio of corpora lutea to total implants, dead fetuses, deciduomas, live fetuses, 24-hr viability of the live fetuses in an incubator, mean live fetal weight, sex ratio of live fetuses, and fetal anomalies.     

醋酸棉酚与米索前列醇对大鼠和小鼠的抗早孕研究

用抗早孕实验和大鼠子宫离体实验,研究了醋酸棉酚与米索前列醇抗早孕的协同作用。结果表明,早孕小鼠单服米索,其终止早孕作用微弱;当与棉酚合用时,对小鼠的抗早孕作用增强。对离体大鼠子宫,米索有明显的增强宫缩作用,而棉酚则无影响,但早孕大鼠po棉酚80mg·kg^-1·d^-1,3d后其子宫对米索的敏感性较对照组有显著提高。大鼠于妊娠d 6～8 po棉酚或米索,或两药剂量的一半合并用药,可使子宫蜕膜组织损伤,而以两药合用组最为严重,但子宫孕酮受体含量和分布与对照组相似。结果提示,两药合用有协同抗早孕作用。     

Comparative teratological study of stobadin in vivo and in vitro

Stobadin (STO) is a prospective cardioprotective drug with antiarrhythmic and antihypoxic effects on the myocardium. Single iv injections of stobadin administered to rats on days 3, 6, 9 or 12 of gestation at doses of 2 and 6 mg/kg had no teratogenic effect. Slight foetal toxicity was manifested by decreased foetal weight (day 3 of gestation, 6 mg/kg) and increased incidence of delayed ossification of the skull (day 12 of gestation, 6 mg/kg). In vitro studies were performed on chick embryos explanted at Hamburger and Hamilton (HH) stages 4–5 and cultivated in a medium with stobadin concentration ranging from 10⁻³ to 10⁻⁸ mol/litre under standard conditions. Concentrations of 10⁻³ and 10⁻⁴ mol/litre were lethal. Embryos treated with concentrations from 10⁻⁸ to 10⁻⁵ mol/litre were comparable to those of the control group. The results of in vivo and in vitro tests showed that the antiarrhythmic agent stobadin at concentrations up to the maximal iv therapeutic dose had no overt effects on different developmental stages of the rat embryo and early chick embryogenesis.     

Evaluation of dimethoate toxicity on pregnancy in albino mice

We investigated whether dimethoate, an organophosphorus insecticide, causes abortion or fetal resorption in pregnant albino mice. Graded doses of 16, 20, 24, and 28 mg/kg body weight/d were administered orally from days 7 to day 15 of pregnancy. Laparotomy was performed on day 8 of pregnancy to note the number of implantations, and the animals were autopsied on day 19. The results revealed no inhibition of pregnancy in all dimethoate treated mice relative to a suitable control group. Treatment with 24 or 28 mg dimethoate caused a significant decrease in the number of implantations, live fetuses, and corpora lutea, but a decreased percent fetal survival and increased percent post-implantation loss and gestation length were not significant when compared with control mice. In all mice treated with 28 mg dimethoate, a significant decrease occurred in the body weight of the ovaries, uterus, and liver when compared with control mice. Following treatment with 16 or 20 mg dimethoate, however, no significant change was found in body and organ weights or in the number of implantations, live fetuses, and corpora lutea, percent post-implantation loss, and fetal survival, or gestation length compared with the corresponding parameters in control mice. The results of this study clearly indicate that dimethoate does not cause abortion or fetal resorption in pregnant mice. A significant decrease in the number of corpora lutea and percent fetal survival observed at higher doses of dimethoate could be due to a toxic effect on the embryo or to a hormonal imbalance.     

2种药流方法终止8～14周妊娠临床疗效比较

目的探讨2种药流方法终止8～14周妊娠的临床效果。方法将要求终止妊娠的8．14周正常早孕女性135例,随机分成两组：复方组67例,晨服复方米非司酮1片／24h02次（总量：米非司酮60mg,双炔失碳酯10mg）,首次服药后48h加服米索前列醇0．6mg,每隔4小时阴道内放置米索前列醇0．4mg,米索前列醇最多一天不超过9片（1．8mg）;单方组68例,一次顿服米非司酮150mg,米索前列醇用法同复方组。用药后观察患者的不良反应、阴道开始出血情况、腹痛情况、胎儿娩出距首次阴道塞药时间、胎儿娩出时阴道出血量、米索前列醇用量,是否需要清宫,同时随访流产后15天、45天,观察患者阴道出血持续时间、出血量的多少及月经转经时间。结果复方组在流产成功率、完全流产率优于单方组,但在米索前列醇用量及妊振物排出时间、流产后阴道流血持续时间、出血量及下次月经转经时间上两组之间差异无显著性（P〉0．05）。结论复方米非司酮配伍米索前列醇能安全有效终止8—14周正常妊振,疗效较好,流产成功率较满意。具有米非司酮剂量小,服药简便等优点。