Effects Of Early Exposure Research Articles

Symposium: Understanding the interaction of stress and gender in the prediction of major depression - Introduction

Three articles from a symposium on stress and depression in women are introduced. Women's exposure to stress, their cognitive and biological coping processes, and the stressful contexts of their lives may all contribute to the higher rates of depression in women compared with men. Mazure and Maciejewski discuss the role of women's cognitions about relevant stressors, Hammen discusses women's interpersonal environment and stress, and Penza, Heim and Nemeroff discuss biological stress reactions and the effects of early exposure to abuse.

Effects of early embryonal exposure to dexamethasone on malformations of neural-crest derivatives induced by nitrofen in rats.

Prenatal corticosteroids reverse to some extent lung and heart hypoplasia in nitrofen-exposed rat pups. The present study examines the effects of early exposure to dexamethasone on the neural crest-related malformations of the cardiovascular system, thymus, parathyroids, and thyroid observed in this model. Pregnant rats were exposed on gestational day 9.5 to either 100 mg 2-4-dichlorophenyl-p-nitrophenyl ether (nitrofen) alone or followed on days 10.5 and 11.5 by 0.4 mg/kg dexamethasone (dexa) i.p. Controls were treated with either oil alone or oil+dexa alone. The fetuses were recovered near term and diaphragmatic, lung, heart, and thymic malformations were sought after dissection. The parathyroids and thyroid were histologically investigated. Control fetuses had no malformations whereas 68% of nitrofen and 65% of nitrofen + dexa fetuses had congenital diaphragmatic hernias (CDH). Heart-outflow tract and pharyngeal artery anomalies were seen in 62% and 61%, respectively in both groups. Heart hypoplasia, which was severe in the nitrofen group, was fully reversed in nitrofen+dexa pups. In contrast, thymic hypoplasia was of similar severity in both groups. The hypoplastic thymus was malformed in 29% and 39%, the parathyroids in 50% and 41%, and the thyroid in 25% and 16% of fetuses, respectively. These differences were not significant. Early exposure to dexa in rat fetuses previously treated with nitrofen thus does not produce any benefit on the incidence or severity of malformations of the cardiac outflow tract and pharyngeal derivatives that accompany CDH in rats exposed to nitrofen. However, even administered so early, this medication prevents heart hypoplasia, suggesting a favorable effect on early heart organogenesis.

Effects of vitamin A on malformations of neural-crest-controlled organs induced by nitrofen in rats.

Vitamin A (vit A) alleviates the effects of nitrofen in exposed rat pups. The present study examines the effects of early exposure to vitamin A on the neural-crest-related cardiovascular, thymic, parathyroid, and thyroid malformations previously reported in the rat model of congenital diaphragmatic hernia (CDH). Pregnant rats were exposed on gestational day 9.5 to 100 mg 2-4-dichlorophenyl-p-nitrophenyl ether (nitrofen) alone or followed by 15,000 IU vit A. Controls were treated only with oil or oil + vit A. The fetuses were recovered near term and diaphragmatic, lung, heart, and thymic malformations were sought after dissection. The parathyroids and thyroid were histologically investigated. The hearts were also examined for protein, DNA, and proportion of proliferating cells. None of the control fetuses had malformations, whereas 41% of nitrofen and 27% of nitrofen + vit A fetuses had CDH. Anomalies of the heart outflow tract and pharyngeal arteries were seen in 64% and 43%, respectively, in both groups. Heart and thymic hypoplasia, which were severe in the nitrofen group with significant decreases of total DNA and percent proliferating cells, were significantly improved in the nitrofen + vit A group. The hypoplastic thymus was malformed in 53% and 27% of fetuses, respectively, and the parathyroids were abnormal in 48% and 35%, respectively. Only minimal anomalies of the thyroid were found. The significant improvement of heart and thymic hypoplasia associated with vit A was not seen for the other variables studied, but there was a trend in this direction for all of them. Vit A definitely improved heart hypoplasia induced by nitrofen by stimulating myogenesis. It also improved thymic hypoplasia, but had limited beneficial effects on malformations of the cardiac outflow tract and pharyngeal derivatives that accompany CDH in rats exposed to nitrofen.

Timing of exposure and mammary cancer risk.

We have tested the hypothesis that timing of exposure to hormonally active chemicals can predetermine susceptibility for mammary cancer. TCDD, the most potent man-made xenobiotic, when given to pregnant rats resulted in the offspring being more susceptible to chemically induced mammary cancer as adults. On the other hand, genistein, the primary isoflavone component of soy, given in the diet during the prepubertal period, or the prepubertal and adult periods, protected against chemically induced mammary cancer. There was an inverse relationship between cancer susceptibility and mammary gland differentiation. The initial effect of early exposure to genistein was to up-regulate the EGF-signaling pathway and to enhance cell differentiation, resulting in reduced EGF-receptor expression in mammary terminal end buds of adults. Genistein has been shown to be bioavailable to the mammary gland in postnatal rats. Differentiation effects are believed to occur via an imprinting mechanism that determines the "blueprint" from which the mammary cells respond to future hormonal and/or xenobiotic exposure.

Increases in ethanol ingestion by young rats following interaction with intoxicated siblings: a review.

Although there are a variety of animal models used in alcoholism research, there has been very little experimental investigation into possible environmental/experiential factors leading to an initial bout of alcohol ingestion. Adolescent alcohol abuse is a major problem in today's society and research is beginning to focus on the predisposing conditions toward alcohol consumption, particularly in this vulnerable age group. The results of recent research from our laboratory are reviewed in which voluntary ingestion of ethanol by preweanling and adolescent rats is increased following exposure to an intoxicated sibling. This paradigm centers on the notion that rodents, and perhaps other mammalian species as well, acquire information about foods to ingest based in part on interaction with a conspecific that has recently ingested a novel diet (e.g. Galef, 1981). Smelling food-derived cues on the breath of another animal is known to affect later food choice. The procedures described in this paper represent a potential new model for examining the effects of early exposure to ethanol through social interactions on the initiation of voluntary alcohol ingestion.

The effects of early exposure of cellulitis-associated Escherichia coli in 1-day-old broiler chickens

Two experiments were performed to test the effect of various field strains of Escherichia coli of cellulitis origin. In the first experiment, 1-day-old broiler chicks were challenged with one of two E. coli field strains using inoculation routes including oral gavage, swabbing of the navel and subcutaneous injection. No cellulitis lesions were produced, although the birds experienced high levels of septicemia/toxemia, characteristic of colibacillosis. The birds that received the E. coli by subcutaneous injection experienced the highest rate of mortality, while those that were challenged by gavage and those that had their navels swabbed experienced lesser rates of mortality. Birds in the second experiment were challenged at 1 day of age with one of three field strains of cellulitis-origin E. coli administered alone or in combination (1:1), which were serially diluted prior to subcutaneous injection. No significant differences in body weight, mortality or cellulitis rates were associated with specific isolates given; however, significant differences were seen with mortality and cellulitis rates according to the dilution of bacteria given. A linear effect was also noted with body weight at 3 weeks, again correlating to the dilution of bacteria that the chicks received.

Effects of Continuous Inhalation Exposure of Rats to Radon and Its Progeny at Various Levels of Dose and Dose Rate: Interim Results

Studies of rats at Harwell and CEA [Monchaux et al., Radiat. Res. 152 (Suppl.), S137-S140, 1999] are currently in progress to determine the factors affecting the risk of induction of lung tumors after exposure to radon and radon progeny. Knowledge of the effect of dose, dose rate and characteristics of the aerosol on lung tumor induction in rats may be used to improve estimates of risk from domestic exposure. At Harwell, three studies are in progress, studying the effect of dose, dose rate, and dose rate at low total exposures. Approximately 2000 adult male rats have been exposed. A small number of rats were taken to determine deposition in the respiratory tract and the early effects of exposure on cell proliferation and nuclear aberrations. The remaining animals have been held for their life span. To date 65% of the animals in the first study have been examined. Current results (for 421 rats) suggest that exposure to radon and radon progeny causes elevated incidences of both benign and malignant lung tumors. These findings are based on incomplete tumor incidences. Competing causes of death may affect the results, and full statistical analysis is required before firm conclusions can be drawn about the effect of dose and dose rate.

Making kinship in the wake of history: Gendered violence and older child adoption

In the United States children enter the state‐run foster care system because of a range of conditions considered to be “abuse and neglect.” Children entering the system are vulnerable to additional bureaucratically ordained violence, some of which is generic and some of which is gendered. This paper situates the exposure of children in state care to gendered violence in a context of poverty, the scaling back of state social welfare programs, and the interaction of gender, family, and race ideologies. The consequences of early exposure to gendered violence are explored through narratives by parents of girls adopted over the age of two who had been subject to sexual and other forms of gendered violence in or before foster care. The need for intervention on the conditions leading to foster care, better monitoring of children's well‐being in foster care, and training and support of foster and adoptive parents regarding recovery from gendered violence is stressed, as is the need to address the ideological conditions leading to the differential exposure of girls and boys to violation.

Effects of early exposure to mating on adult sexual behavior in male mice varying in their genetic disposition for aggressive behavior

This study examined whether the sexual behavior of adult male mice is influenced by exposure in early postnatal life to brief episodes of mating. Another focus of interest was the interplay between a genetic disposition for aggressive behavior and the early exposure experiences. The subjects used in the study were male mice of the fiftysixth generation of selection for high (Turku aggressive, TA) and low (Turku non-aggressive, TNA) levels of aggressiveness. Moderately aggressive males of the parental strain (normal, N) were also used. Subjects of each strain were exposed from 21 to 32 days of age to mating mice behind a wire mesh screen. Control subjects were placed in a comparable enclosure, but were exposed to nothing. The results showed that male mice exposed to mating early in life showed a higher rate of activities in the sexuality tests, including aggressive responses. A genetic potential for aggressive behavior was related to a higher degree of sexual activity, and the early exposures optimized the hereditary attributes. The relation between sexual and aggressive behavior is discussed. © 1994 Wiley-Liss, Inc.

Effects of Beer on Breast-fed Infants-Reply

In Reply. —I read Drs Mennella and Beauchamp's contribution to the debate about beer and lactation with interest. In my reply to a question about prescribing beer to breast-feeding mothers, I remarked that the possible long-term effects of early exposure to small amounts of ethanol in infants were unknown, but that physicians should be wary about ever prescribing alcohol as a drug to their patients for any indication. Since that reply was written, Little and colleagues 1 reported on a study of the relationship between child development at age 1 year and postnatal alcohol intake (through breast-feeding). The subjects were 400 infants born to members of a health maintenance organization, primarily white, middle-class, educated women. An estimate was made of each infant's total exposure to alcohol through breast milk, based on maternal intake and the number of days of breast-feeding for each month. The findings were controlled for levels of

Effects of early exposure to intermale aggression on the aggressiveness of adult male mice varying in their genetic disposition for aggressive behavior

This study examined whether adult male aggression is influenced by either visual or olfactory exposure in early postnatal life to brief episodes of aggression. Another focus of interest was the interplay between a genetic disposition for aggressive behavior and early exposure experiences. The subjects used in the study were male mice of the 49th generation of selection for high (Turku Aggressive, TA) and low (Turku Non-Aggressive, TNA) levels of aggressiveness. Moderately aggressive males of the parental strain (Normal, N) were also used. Subjects of each strain were exposed from 21 to 32 days of age to fighting males either behind a wire mesh or glass screen. Control subjects were isolated during the entire experimental period. At 90–100 days of age, each subjects was tested three times for its aggressiveness. Exposure to fighting males behind a wire mesh screen enhanced later aggressiveness of juvenile male mice. Juveniles exposed solely to visual cues were comparable to isolates, both groups showing less adult aggression. Early experience and the genetic disposition for aggression were correlated; TA males showing the greatest increase in aggressive behavior. The role of early olfactory learning is discussed. © 1993 Wiley-Liss, Inc.

Effects of Early Exposure to Diethylstilbestrol on Cellular Protein Expression by Mouse Vaginal Epithelium and Fibromuscular Wall

Epithelia and fibromuscular walls were dissociated from the vaginae of ovariectomized BALB/cCrgl mice (ca. 41 days old) exposed neonatally to diethylstilbestrol (DES) or sesame oil and purified by centrifugation through Percoll density gradients. Neonatal exposure to DES caused the vaginal epithelium to become permanently proliferated and partially keratinized; the control epithelium was low cuboidal. The major cellular proteins expressed in each tissue compartment were examined by two-dimensional gel electrophoresis of [35S]methionine-labeled tissues. The epithelia and fibromuscular walls displayed distinctive two-dimensional protein patterns. In the DES-exposed vaginal epithelium, the expression of two proteins (one had a molecular size of 65 kDa and a pl of 6.0, and the other had a molecular size of 38 kDa and a pl of 6.3) was increased, while the expression of three proteins with molecular sizes of 25, 30, and 140 kDa and pls of 5.6, 5.6 and 6.7, respectively, was reduced, relative to the control epithelium. In the DES-exposed vaginal fibromuscular walls, the expression of 9 proteins was increased whereas the levels of 21 specific proteins, distinct from those in the epithelium, were decreased. Thus, long-term tissue-specific alterations in the synthesis of a select number of cellular proteins occur in the DES-exposed vagina.

Prior intra‐uterine position of lactating mice: Effects on attackability by adult resident females

Abstract The foetus intra‐uterine position of lactating mice neither modifies the degree to which they are attacked by resident females in adult life nor their aggressive response towards those females. It thus appears that the effects of early exposure to testosterone from adjacent male siblings has no influence on either odour‐cue production or the types of behaviour associated with this form of attack. This is yet another point of contrast with ≪intermale≫ type behaviour as it is well established that the intra‐uterine position (and the associated changes in the CNS) has a profound influence on a female's willingness to attack adult males.

Effect of early exposure to family medicine on students' attitudes toward the specialty.

In the study reported here, the authors examined the influence of clinical experiences of students on their choice of family medicine as a specialty. Attitudes toward family medicine were investigated among 172 first-year and 174 second-year students at the University of Minnesota Medical School--Minneapolis. Neither early exposure to role models in family medicine nor the order in which specialty clerkships were taken had a significant effect on the students' choice of family medicine as a specialty.

Symptoms of car painters with long-term exposure to a mixture of organic solvents.

Symptoms as an early sign of the effect of low-level exposure to organic solvents were studied among 102 male car painters and 102 referents with the aid of a symptom questionnaire. The exposure level was about one-third of the current administrative threshold limit value recommended in Finland. In addition to the comparisons of the appearance of single symptoms among the exposed and reference groups partial correlation and factor analyses were performed. Symptoms of fatigue and disturbances in memory and vigilance occurred statistically significantly more often among the exposed than among the referents. When the symptoms during the workshift (acute symptoms) were compared, irritation symptoms and "prenarcotic" symptoms were reported significantly more often in the exposed group. Correlation and factor analyses of the acute symptoms among the car painters suggested that acute symptoms are related at the individual level, as hypothesized on the basis of earlier literature. By means of a questionnaire sent to 124 men who changed employment in the 5 a before this investigation, it was found that health was an important reason for having left the car painting trade for those who had taken jobs without exposure to organic solvents. This finding indicates that those car painters included in this study may have undergone some degree of health selection. The results suggest that a symptom inquiry is helpful for detecting the possible early effects of exposure to a mixture of organic solvents.

Social olfaction: a review of the ontogeny of olfactory influences on vertebrate behavior

Research on the postnatal development of behavior involving olfaction is reviewed. Included are investigations of olfactory responses of human neonates and young children, the development of preferences in various mammals, the ontogeny of the fright reaction in fish and amphibia, and the attraction of maternal odors for small mammals. The effects of early exposure and conditioning to olfactory stimuli on adult behavior in mammals and fish are reported including a survey of the status of the olfactory hypothesis in fish migration. Deprivation experiments suggest disruption of later behavior. Limitations of the present knowledge and directions for future research are presented.

Effect of early exposure to photic stimulation on brightness discrimination and exploratory behavior.

Effect of early exposure to photic stimulation on brightness discrimination and exploratory behavior.