Residual effects of polybrominated biphenyls following perinatal exposure in rats

Rats were exposed to 0.5 ppm of ozone delivered for 23.5 hr per day for up to 180 days. One group of rats was allowed to breathe filtered air for about 2 months after the conclusion of the exposure. Lung collagen and total-protein synthesis rates were quantitated by biochemical analyses performed with lung minces. Other lung lobes from the same rats were used to quantitate collagen and total protein content. Increased levels of lung protein and of lung collagen (hydroxyproline) content were observed at all times sampled during exposure to ozone (3, 30, 50, 88, 180 days); the observed lung hydroxyproline content at 180 days persisted during the 2 months of postexposure recovery. Collagen synthesis rates measured in lung minces were elevated in the exposed rats at all times sampled, consistent with the observed increased lung collagen content seen throughout the study. The observed biochemical changes were consistent with concurrent morphological observations of the occurrence of mild pulmonary fibrosis.     

Action of exogenously administered steroid hormones following perinatal exposure to polybrominated biphenyls.

Polybrominated biphenyls (PBBs) have produced a variety of effects including alterations in the endocrine system and in the activity of microsomal mixed-function oxidases (MFOs). Because steroid hormones are substrates for MFOs, effects of PBBs on the endocrine system may be a consequence of enhanced steroid hormone catabolism. Therefore, as a first step in evaluating the effect of PBBs on steroid hormone catabolism. Therefore, as a first step in evaluating the effect of PBBs on steroid hormone metabolism, it was of interest to determine effects of perinatal exposure to PBBs on the response to exogenously adminstered steroid hormones. Rats were exposed to 0, 10, or 100 ppm PBBs from d 8 of gestation until d 28 postpartum, when experiments were conducted. Responses to labeled steroid hormones were generally modified in a manner directly related to PBB dose and were correlated with changes in serum and target tissue retroactivity. Stimulated metabolism of steroid hormones may account, at least in part, for endocrine-related alterations produced by PBBs. Although the potential for decreased reproductive capacity following PBBs cannot yet be accurately predicted, these experiments suggest that fertility may be reduced following PBBs as a consequence of accelerated steroid hormone metabolism and/or excretion.     

Cardiac and hepatic effects of pre- and postnatal exposure to polybrominated biphenyls in rats

Body weight gain and hepatic concentrations of vitamin A were reduced in Sprague-Dawley rats by pre- and postnatal exposure to 100 ppm polybrominated biphenyls (PBBs). The ratio of liver weight to body weight, activity of hepatic delta-aminolevulinic acid (ALA) synthetase, and urinary excretion of uro- and coproporphyrins were increased by PBBs. Treatment with PBBs also increased the left atrial inotropic response to calcium. However, PBBs had no effect on development of the adrenergic neuronal transport system in heart, left atrial baselike peak tension, or inotropic response to ouabain. Thus PBBs retarded body weight gain and produced a variety of alterations in liver, but had little effect on cardiac contractile function.     

The human health effects of exposure to polybrominated biphenyls

Polybrominated biphenyls (PBB) were inadvertently introduced into the food chain in Michigan in 1973. Fifty-one people with known exposure to PBB were studied. Twenty-three farmers with disabling health complaints, and 28 chemical workers involved in the PBB manufacturing process were systematically evaluated to determine if these highrisk groups suffered adverse effects from their known exposure to PBB. The farmers had a high frequency of constitutional symptoms, hepatomegaly and skin rashes, findings not commonly noted in the chemical workers. Biochemical and hematologic testing revealed few abnormalities, and electromyograms, nerve conduction velocities, endocrine studies, and lymphocyte transformation studies provided no objective findings that correlated with subjective complaints. There was no relationship between PBB levels and physical or laboratory abnormalities. Present evidence suggests that people exposed to PBB have few objective findings at this time, and reactive depression may be responsible for the high prevalence of constitutional symptoms.     

Altered metabolism of progesterone by hepatic microsomes from rats following dietary exposure to polybrominated biphenyls

The local anesthetic mepivacaine and various other drugs known to perturb sarcoplasmic calcium metabolism and/or sarcolemmal sodium conductance were injected into the gastrocnemius or subcutaneously over the gracilis muscles of rats. After 48 hr, the tissues were examined histologically, and muscle damage was rated on a single-blind basis. Following im administration, all of the agents tested which are capable of increasing the intracellular concentration of free calcium—mepivacaine-HCl, quinidine gluconate, A23187, caffeine, and 2,4-dinitrophenol-produced extensive and qualitatively similar myonecrosis. Damage to skeletal muscle was absent or negligible after im injection of control saline solutions or tetrodotoxin, a drug that blocks sodium channels without directly influencing the intracellular calcium distribution. The sc administration of mepivacaine caused extensive damage to fibers approximating the muscle surface, while saline was without effect. To assess the influence of a calcium antagonist on local anesthetic-induced myonecrosis, verapamil-HCl was administered sc, both alone and in combination with mepivacaine. Although verapamil by itself resulted in some minor surface injury, it almost completely blocked the damage produced by mepivacaine. It is concluded that the myotoxicity of local anesthetics is related to a disturbance of intracellular calcium homeostasis rather than to an influence on sarcolemmal sodium conduction.     

Mixed function oxidase activities in lactating rats and their offspring following dietary exposure to polybrominated biphenyls.

Exposure of pregnant rats to diet containing 50 ppm polybrominated biphenyls (PBBs) from day 8 of gestation to day 15 postpartum caused significant increases in hepatic and extrahepatic microsomal mixed function oxidase activity. Hepatic arylhydrocarbon hydroxylase (AHH), epoxide hydratase (EH), hexobarbital hydroxylase (hex-OH), and the 2- and 4-hydroxylation of biphenyl (2-OHBP, 4-OHBP) were increased 10, 3, 3, 23, and 6-fold respectively in animals fed diet containing PBBs. The hex-OH, 2-OHBP, and 4-OHBP activities were not detectable in the S9 fraction from maternal mammary glands of control or PBB-fed rats; however, exposure to PBBs increased mammary AHH 2.5-fold and decreased EH activity 45%. Renal AHH activity was increased 7-fold but renal EH activity was unaltered by feeding PBBs. Pups from control and PBB-exposed mothers were crossfostered at birth to give offspring which received PBB exposure prenatally, postnatally (via mothers milk), or both pre- and postnatally. Each type of exposure produced increases in hepatic AHH and EH activities over those found in pups born to and raised by mothers which received no PBBs. The results demonstrate that PBBs induce hepatic and extrahepatic mixed function oxidase activity in nursing rats and that the extrahepatic effects of the mixture are different from the hepatic effects. Furthermore, PBBs were effective stimulators of hepatic enzymes in 15-day-old rats when the neonates were exposed transplacentally and/or via the mothers' milk. The results suggest potential toxic interaction between PBBs and other agents which are of importance to both mother and young.     

Developmental and neurobehavioral effects of perinatal exposure to polychlorinated biphenyls in mice

Because behavioral deficits associated with gestational exposure to polychlorinated biphenyls (PCBs) have been a concern, we studied the developmental and neurobehavioral effects of perinatal exposure to Aroclor 1254 (A1254), a commercial mixture of PCBs, in mice. The PCB mixture (A1254; 0, 6, 18, and 54 mg/kg body weight) was administered to pregnant mice (C57BL/6Cr) every 3 days by gavage from gestational day (GD) 6 to postnatal day (PND) 20. Compared with the control, treatment with A1254 did not alter the maternal body weight during the gestation and lactation periods. The body weight of the offspring did not differ among treatments. To assess the effects on offspring following such exposure, physical and neurobehavioral development (i.e., pinna detachment, hair growth, eye opening, incisor eruption, grasp reflex, righting reflex, walking, negative geotaxis, and cliff avoidance) was observed before weaning. At PND 7, poor adult-like responses in negative geotaxis were observed in all exposed groups. When the offspring were at 8-week old, the PCB-treated (18 mg/kg body weight) mice showed a decreased walking speed in the open-field test, and a prolonged time to reach the platform in the water maze test. Spontaneous locomotion activity was not affected by PCB exposure at 9 weeks . These results showed that perinatal exposure to PCBs produces several behavioral alterations in mice. Although dose-dependent changes were not observed, the neurobehavioral effects such as a decreased walking speed in the open-field test and a prolonged time to reach the platform in the water maze test remained in adulthood after the seeming recovery from the transient delay in development before weaning.     

Reproductive and genotoxic effects in zebrafish after chronic exposure to methyl methanesulfonate in a multigeneration study

There is still controversy whether adverse effects by genotoxic anthropogenic pollutants are linked to the decline of fish populations. Further investigations into the relationship between genotoxic stress and detrimental effects on development and reproduction in fish are required. For this end, zebrafish (F0 generation) were exposed in vivo to the alkylating model genotoxin methyl methanesulfonate (MMS) from fertilization to the age of 1 year. F0 fish were mated over 6 months to check for reproductive capacities. F1 fish grew up without exposure in order to allow for regeneration. Mortality of F0 fish depended on MMS concentrations. In MMS-exposed F0 fish, times of first spawning were delayed and fertility was reduced. Using the alkaline comet assay and the micronucleus test, significant genotoxic effects were found in the livers, gills and gonads of either sex in the F0 generation. No detrimental effects on growth were found. In F1 fish with parental exposure, teratogenic effects were increased, and larval survival was reduced. However, fertility capacities of the non-exposed F1 generation had recovered. Development and survival rates further recovered in the F2 generation. Anthropogenic genotoxicants may thus play a considerable role in the decline of wild fish populations.     

The effects of 4-nonylphenol in rats: a multigeneration reproduction study.

The alkylphenol breakdown products of alkylphenol ethoxylates have been shown in in vitro studies to be weakly estrogenic, but few in vivo data address this issue in mammals. Because estrogens have been found to be most potent during developmental/perinatal exposures, this study maximized developmental exposure to nonylphenol (NP) by treating 3.5 generations of Sprague-Dawley rats to NP in diet at 200, 650, and 2000 ppm to determine the range and severity of any toxicity. Dose rate was higher for younger rats; calculated dose ranges were 9-35, 30-100, and 100-350 mg/kg/d for the low (200NP), middle (650NP), and high (2000NP) dose groups, respectively. There were adult (F0, F1, F2) and postnatal day (pnd) 21 (F1, F2, F3) necropsies; the oldest F3 rats were killed on pnd 55-58. Body weight gain was reduced by 8-10% in the 650NP and 2000NP groups. Vaginal opening was accelerated by approximately 2 days (650NP) and approximately 6 days (2000NP) in F1, F2, and F3 generations. Uterine weights at pnd 21 were increased in 650NP (14%) and 2000NP (50%) F1 females, but not in other generations. Testis descent, anogenital distance, and preputial separation were not consistently changed. No consistent changes were seen in pup number, weight or viability, litter indices, or other functional reproductive measures. Relative ovary weight in F2 adults was decreased at 650NP and 2000NP by 12%; relative ovary was unchanged in other generations. Follicle counts were unchanged in F2 adults. Sperm indices, including CASA measures, were unchanged in F0 and F1 males. In F2 rats, epididymal sperm density was reduced by 8% and 13% at 650NP and 2000NP, respectively. Testicular spermatid count was reduced by 13% in 2000NP F2 males; testis and epididymis weights were unchanged. Erosion of gastric and duodenal mucosa was monitored grossly and microscopically, and never found. Kidney weights were increased in 650NP and 2000NP males, and renal medullary tubular dilatation and cyst formation were noted in all generations of males, and often at the lowest dose tested. These data show that NP had limited effects on the reproductive system in the presence of measurable nephrotoxicity. The F2 sperm effects are either statistical/biological "noise," or imply heretofore unknown pharmacokinetics or toxicodynamics. These sperm data should be interpreted cautiously until the findings are repeated.     

Perinatal exposure to polychlorinated biphenyls alters social behaviors in rats

Perinatal exposure to polychlorinated biphenyls (PCBs) leads to significant alterations of neural and hormonal systems. These alterations have been shown to impair motor and sensory development. Less is known about the influence of PCB exposure on developing emotional and motivational systems involved in social interactions and social learning. The present study examined the impact of perinatal PCB exposure (mixture of congeners 47 and 77) on social recognition in juvenile animals, conspecific-directed investigation in adults and on neural and hormonal systems involved in social functions. We used a standard habituation–dishabituation paradigm to evaluate juvenile recognition and a social port paradigm to monitor adult social investigation. Areal measures of the periventricular nucleus (PVN) of the hypothalamus were obtained to provide correlations with related hormone and brain systems. PCB exposed rats were significantly impaired in social recognition as indicated by persistent conspecific-directed exploration by juvenile animals regardless of social experience. As adults, PCB exposure led to a dampening of the isolation-induced enhancement of social investigation. There was not a concomitant alteration of social investigation in pair-housed PCB exposed animals at this stage of development. Interestingly, PVN area was significantly decreased in juvenile animals exposed to PCB during the perinatal period. Shifts in hypothalamic regulation of hormones involved in social behavior and stress could be involved in the behavioral changes observed. Overall, the results suggest that PCB exposure impairs context or experience-dependent modulation of social approach and investigation. These types of social-context deficits are similar to behavioral deficits observed in social disorders such as autism and other pervasive developmental disorders.     

Long-term effects of a single oral dose of polybrominated biphenyls on serum and liver lipids in rats

Adult (5 months) male Sherman strain rats received a single dose of either 0 or 500 mg polybrominated biphenyls (PBB) in corn oil/kg body weight by stomach tube. After an 18-month recovery period, serum and liver samples were examined. The primary serum lipid response was an increase in cholesterol (both free and esterified) and in total phospholipids. The percentage of esterified cholesterol was not significantly different from that of the controls, and no significant differences in the cholesterol ester fatty acid composition were observed. Serum triglycerides were also unaffected. In the PBB-dosed animals, the total hepatic fatty acids contained significantly less palmitic acid and more stearic acid, consistent with an increase in palmitic acid chain elongation activity. No significant differences could be detected in the n-3 or n-6 acids except for a slight decline in the content of 22:6 (n-3). Hepatic microsomal phospholipids were slightly higher (per milligram protein) in the PBB-dosed animals, and the cholesterol content was lower. Consequently, the cholesterol-phospholipid ratio was reduced, and microsomes from the latter group appeared to have an altered lipid domain on the basis of steady-state fluorescence anisotrophy measurements. In addition, total hepatic thiobarbituric acid-reactive substances (assayed as malondialdehyde) were significantly increased in the PBB-dosed animals. This observation appeared to reflect an increased susceptibility to peroxidative stress in the latter group, probably resulting from reduced membrane antioxidant concentrations. The PBB-dosed rats had significantly lower serum retinol levels and a reduced content of this vitamin in liver microsomes. Microsomes were also deficient in alpha-tocopherol in the PBB-dosed animals, although serum levels were normal.     

Endocrinological, neurochemical, and anabolic effects of polybrominated biphenyls in male and female rats

Pregnant rats were placed on a control diet or on a diet containing 100 ppm polybrominated biphenyls (PBBs, Firemaster PB-6) on Day 8 of gestation. On Day 28 postpartum the pups were weaned onto the same diet as their mothers, and maintained on this diet until sacrificed during the ninth week. Body weight gain was reduced in both the male and female rats exposed to PBBs. The absolute weights of some organs (ventral prostate and seminal vesicles in males, and adrenal and pituitary glands in females) were reduced in animals maintained on the PBB diet, but when expressed as a percentage of body weight only the ventral prostate weight remained significantly reduced. Exposure to PBBs did not affect plasma concentrations of luteinizing hormone, prolactin, or corticosterone; nor did it affect the increase in the plasma concentration of the latter two hormones in response to a mild environmental stress. Exposure to PBBs did not alter the steady-state concentrations of norepinephrine or dopamine in the posterior pituitary or selected brain regions. Furthermore, treatment with PBBs did not alter the rates of synthesis of these catecholamines (as estimated by the rate of accumulation of dihydroxyphenylalanine following inhibition of dihydroxyphenylalanine decarboxylase) in the brains of female rats on the day of diestrus or estrus. On the basis of vaginal cytology, exposure to PBBs significantly lengthened the estrous cycle of female rats.     

Developmental coexposure to polychlorinated biphenyls and polybrominated diphenyl ethers has additive effects on circulating thyroxine levels in rats

Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are widespread environmental contaminants found in seafood and dairy products. PCBs and PBDEs are structurally similar chemicals and affect thyroid hormone function and behavior in children and laboratory rodents. Although coexposure frequently exists, the in vivo developmental effects of combined exposure to PCBs and PBDEs on thyroxine (T4) levels are unknown. We examined the effects of PCB and PBDE coexposure from gestational day 6 through postnatal day (p) 21, alone and in combination, on T4 levels in rat offspring. In males, exposure to PCBs and PBDEs at 1.7, 5, 10, 20, 40, and 60 μmol/kg/day induced equivalent and dose-dependent reductions in T4 from p 7 to p 21. Exposure to equimolar mixtures of PCBs and PBDEs at 3.4, 10, 20, 40, and 80 μmol/kg/day additively reduced T4 from p 7 to p 21 in males. In a second series of experiments, we determined sex effects on the mixture exposures and found that coexposure to PCBs and PBDEs had similar additive effects on T4 levels in male and female offspring. This study demonstrates that equimolar exposure to PCBs and PBDEs induces similar reductions in T4 levels and that coexposure to a mixture of PCBs and PBDEs has additive effects on T4 levels. These thyroid hormone effects of coexposure to PCBs and PBDEs are important when considering the cumulative effects of coexposure to multiple environmental thyroid hormone-disrupting agents in risk assessment for developmental disorders.     

Renal and hepatic microsomal enzyme stimulation and renal function following three months of dietary exposure to polybrominated biphenyls.

Polybrominated biphenyls (PBB) stimulate microsomal enzyme activity and produce a variety of toxic manifestations, including renal and hepatic histopathological changes. Therefore, it was of interest to determine the effect of chronic exposure to PBB on renal and hepatic microsomal enzyme stimulation and renal function. Adult Sprague-Dawley rats were fed diets containing 0 or 100 ppm of PBB for 3 months. Treatment with PBB retarded weight gain and increased the liver to body weight ratio but did not alter kidney to body weight ratio. Biphenyl-4-hydroxylase (BP-4-OH) and biphenyl-2-hydroxylase (BP-2-OH) activities were elevated in the kidney and liver following treatment with PBB. Exposure to PBB increased aryl hydrocarbon hydroxylase (AHH) activity in the kidney and liver. Epoxide hydratase (EH) activity was increased in the liver but decreased in the kidney following exposure to PBB. A three-month exposure to PBB had no effect on blood urea nitrogen, the clearance of inulin, p-aminohippurate (PAH), or fractional sodium excretion. Similarly, the in vitro accumulation of PAH and N-methylnicotinamide (NMN) in thin renal cortical slices and ammoniagenesis and gluconeogenesis in renal cortical slices were not affected by PBB. In conclusion, chronic exposure to PBB resulted in significant alterations in renal and hepatic microsomal enzyme activities but had no detectable effect on renal function. These experiments suggest that alterations in microsomal enzyme activities following PBB do not lead to impairment of renal function; however, this compound may sensitize the kidney to toxicity produced by agents administered subsequent to PBB.     

Differential tissue distribution of various polybrominated biphenyls of Firemaster FF-1 in male rats

Gas chromatography with an electron-capture detector was used to identify the major components of the polybrominated biphenyls (PBB's) in Firemaster FF-1. The distribution and clearance of the PBB's in rat whole blood, grey and white matter, cerebellum, heart, kidney, liver, spleen, lung, jejunum, testes, and subcutaneous fat from the inguinal region were determined at various times after a single dose of 10 mg/kg of Firemaster FF-1 given orally. Peak blood levels of PBB occurred within 4 hr whereas levels in inguinal subcutaneous fat peaked 7--14 days after the single oral dose. Concentrations in other tissues peaked usually within 12 hr and showed complex logarithmic decline over time. 2,2',4,5,5'-Pentabromobiphenyl (PnBBa) was cleared much more rapidly from the rat than 2,3',4,4',5-pentabromobiphenyl (PnBBb) or any of the higher molecular weight analogs. Furthermore, PnBBa penetrated the brain more rapidly. Each of the PBB analogs was found in all tissues examined but varied in both rate of absorption and clearance.     

Immunologic effects of perinatal exposure of rats to dioctyltin dichloride

Studies were conducted to determine the period of immune system development that was most sensitive to perturbation by the known immunotoxicant di-n-octyltin dichloride (DOTC). Fischer 344 rats were exposed prenatally, both pre- and postnatally, or postnatally to DOTC by oral gavage of pregnant and/or lactating females. At various ages, ranging from 3 to 16 wk of age, offspring were examined for a number of immune functions. These included body and lymphoid organ weights; lymphoproliferative responses to B- and T-cell mitogens; natural killer cell activity; and primary antibody response to sheep erythrocytes. Prenatal (10-20 of gestation), pre- and postnatal (d 11-20 of gestation and 2-11 d of age), or postnatal (2-13 d of age) oral dosing of dams with 20-50 mg/kg DOTC resulted in no consistent alteration in immune function in offspring. However, direct oral dosing of rat pups to 5-15 mg/kg DOTC, beginning at 3 d of age and then 3 times per week up to 24 d of age for a total of 10 doses, resulted in significant suppression of the lymphoproliferative response of splenocytes to a T-cell mitogen in 10-wk-old rats (i.e., 7 wk after the last exposure to DOTC). Lymphoproliferative responses returned to control levels by 12 wk of age. In comparison young adult (8 wk old) rats dosed with 10 or 20 mg/kg DOTC under an identical dosing schedule (i.e., 3 times per week for a total of 10 doses) showed no suppression in the mitogen response of splenocytes 4 wk after the last exposure to DOTC. These results suggest that direct dosing of pups during early postnatal life may be the most effective means of inducing immunosuppression with DOTC during immune system development. The results also provide evidence for the greater sensitivity of the developing immune system compared with the fully developed immune system for a known immunotoxicant.     

Ouabain lethality as a measure of biliary function in developing mice and rats and effect of polybrominated biphenyls.

Ouabain is excreted by the liver into the bile in rats and mice. Furthermore, newborn rats are immature in their ability to excrete ouabain and are particularly susceptible to ouabain toxicity. The purpose of this study was to determine whether or not newborn mice are also sensitive to ouabain toxicity, whether or not ouabain toxicity is a suitable index of biliary function, and whether or not perinatal exposure to polybrominated biphenyls (PBBs) results in altered hepatic function in rats and mice. Ouabain toxicity was assessed by determining 24-hr LD50 values and the hepatic excretion of ouabain was determined by measuring radioactivity in plasma, liver, and intestine following a single injection of [³H]ouabain in mice and rats of various ages. The LD50 of ouabain in 10-day-old mice was 1.85 mg/kg (ip) and increased with age until the animals were 18 days of age when LD50 values were the same as values obtained from adults (16.50 mg/kg). In addition, following ip injection of [³H]ouabain, plasma concentrations of ouabain were higher in young mice relative to adults. Treatment with PBBs through the mother's diet did not affect ouabain LD50 values in 15-day-old mice but did result in a significant increase in liver weight and enhanced disappearance of ouabain from the plasma in these animals. In developing rats exposed to PBBs, a similar enhancement of liver weight and hepatic transport of ouabain was observed; however, in rats, enhanced ouabain transport correlated with protection against ouabain toxicity. These results suggest that ouabain lethality is not a good index of biliary function in developing mice. However, ouabain toxicity can be used to estimate hepatic function in rats. In this regard, perinatal exposure to PBBs resulted in a significant drug (ouabain) interaction.     

Human exposure to polychlorinated biphenyls and health effects: a critical synopsis

Polychlorinated biphenyls (PCBs) are a mixture of chemicals. Some congeners of the mixture are highly persistent both in the environment and in humans. Although PCBs have not been used commercially since about 1977 in the US, they can still be detected in human blood and tissues in this country. PCB levels are declining and are often no longer detectable in younger people. A cursory review of recent animal studies is provided. Studies to determine whether PCBs cause cancer in humans, neurobehavioural effects, abnormal thyroid and immune function in children and low birth weight are discussed in more detail. These studies are inconclusive and do not provide clinical evidence that PCBs at levels encountered with human exposure produce adverse health effects. The differences in PCB blood or tissue concentrations between controls and cases, or between the upper and lower end of various environmentally exposed groups of children or adults, are small. Although some effects are statistically significantly different, they do not appear to be biologically significant. Many studies on the effects of PCBs are difficult to interpret because the range of normal values for clinical and neurobehavioural tests are not provided or appropriately considered, there was no, or inadequate, control for potential confounders. In occupational mortality studies, exposures were much higher. In some studies, various specific cancers were elevated. However, these appear to be chance observations resulting from multiple comparisons since the increase of specific cancers was not consistent between studies and was no longer present in some cohorts when studies were repeated at a later date with longer follow-up. Overall, the data fail to demonstrate conclusive adverse health effects of PCBs at concentrations encountered with human exposures.     

The induction of hepatic microsomal metabolism in rats following acute administration of a mixture of polybrominated biphenyls.

A high frequency of congenital limb defects after maternal treatment with the nitrogen mustard chlorambucil suggested that cytotoxic effects could be analyzed as correlates of teratogenic action of this alkylating agent. Limb buds from $\text{ICR}\text{DUB}$ mouse embryos were exposed in vivo or in vitro to teratogenic doses of chlorambucil. At 0.5- to 72-hr intervals following exposure, the limbs were processed for observation with the light and electron microscopes. Light microscopy of limb buds exposed to the drug in vivo or in vitro showed evidence of cellular involvement within 4 hr following treatment. The effects were manifested in the form of cytoplasmic inclusions which increased in number as the time following exposure increased, and, in vivo, reached a maximum at 24 hr. Increased doses of the drug also produced increased numbers of affected cells. In limb buds exposed to chlorambucil in vitro, the number of affected cells reached a plateau at 48 hr after treatment and decreased significantly by 72 hr, at which time exposure to a second dose of the drug had little or no effect. Affected cells were restricted almost exclusively to regions of undifferentiated mesenchymal cells. Electron microscopic examination of the cytoplasm of affected cells demonstrated the presence of membrane-bound vacuoles containing cellular organelles in various stages of degeneration. The number and size of these vacuoles increased with time following exposure until finally the cells fragmented. Nuclear material was not involved until fragmentation of the cells occurred, at which time the nucleus became pyknotic. Following cellular fragmentation and destruction, macrophages were observed in association with the cellular debris. Acid phosphatase was demonstrated within the vacuoles (by the presence of lead phosphate precipitates) with the electron microscope after incubating limb bud tissue in a buffered solution of β-glycerophosphate/lead nitrate. The amount of demonstrable enzyme was found to increase as the degree of breakdown within vacuoles increased. These results and the histological information provided evidence consistent with a process of autophagocytosis.     

Effects of perinatal exposure to delta-9-tetrahydrocannabinol on the emotional reactivity of the offspring: a longitudinal behavioral study in Wistar rats

RATIONALE: The endocannabinoid system plays a crucial role in the control of emotionality and recent clinical findings have shown that heavy prenatal exposure to cannabis is significantly associated with self-reported anxiety symptoms in exposed children. However, the long-term neurobehavioral consequences of in utero exposure to low-moderate doses of cannabinoid compounds have never been investigated. OBJECTIVE: The objective of this study was to investigate whether perinatal exposure to moderate doses of the active constituent of cannabis, the CB(1) cannabinoid receptor agonist delta-9-tetrahydrocannabinol (THC), influences the emotional reactivity of rat offspring. METHODS: Primiparous Wistar rats were treated during pregnancy and lactation with doses of THC equivalent to the current estimates of moderate cannabis consumption in humans (2.5-5 mg kg(-1), per os, from gestational day 15 to postnatal day 9). The emotional reactivity of infant, adolescent, and adult offspring was investigated using the isolation-induced ultrasonic vocalization, social interaction, and elevated plus-maze tests, respectively. RESULTS: Perinatal THC treatment did not affect parameters of reproduction; however, at the dose of 5 mg kg(-1), it increased the number of ultrasounds emitted by rat pups removed from the nest, inhibited social interaction and play behavior in the adolescent offspring, and induced an anxiogenic-like profile in the adult offspring tested in the elevated plus-maze test. CONCLUSION: These results suggest that the endocannabinoid system is involved in the control of emotionality since early developmental stages. Thus, even moderate doses of cannabinoid compounds, when administered during the perinatal period, can have profound consequences for brain maturation, leading to long-lasting neurodevelopmental alterations.