Teratogenicity of ethanol in different chicken strains.

This study investigated the teratogenicity of ethanol in several different strains of chickens. The chick embryo provides a useful model for studying the fetal alcohol syndrome. Two broad classifications of chicks, each containing many strains, are commercially available for use: broilers and layers. Teratogenicity of ethanol in broilers and layers was studied by examining three different parameters: embryo weight, ratio of torso weight to head weight, and embryo viability. Broilers and layers experienced similar ethanol-induced reductions in embryo weight, Broiler embryos experienced a preferential ethanol-induced suppression of head growth. Differences in viability between different strains were found, but no clear pattern between broilers or layers could be determined, possibly due to environmental conditions. The data presented here suggest that the strain of chick and the handling of the eggs are important considerations when studying the teratogenicity of ethanol. An ethanol dose-response test should be periodically performed as a check on environmental conditions affecting the eggs--conditions that are beyond the control of the researcher.

Ameloblast cycling patterns as measured by fluorochrome infiltration of rat incisor enamel.

Rapid modulation of maturation ameloblasts between smooth-ended and ruffle-ended forms may play an important part in the development of normal dental enamel. Previous studies of modulation rates relied upon measurements of stained or fluorescing bands on the enamel surface of whole incisors along with separate histological sections for cell-band dimensions. The present study utilized direct measurement of maturation-ameloblast bands and fluorescing regions of underlying enamel in the same histological sections, which increased the accuracy and ease with which modulation rates could be determined. Rats were injected with calcein at various times before killing and preparation of survey midsagittal sections of the lower incisors. The lengths of bands of smooth-ended ameloblasts and underlying fluorescing regions of enamel were measured throughout the maturation zone. Modulation rates were found to range from 238 microns/h (early maturation) to 91 microns/h (late maturation). Calcein diffused into enamel to varying degrees depending upon the location within the maturation stage. This new approach of direct measurement greatly facilitates the investigation of ameloblast modulation and provides additional insights into progressive structural changes in enamel during maturation.

Infant and child mortality estimates in two counties of Liberia: 1984.

To estimate baseline infant and child mortality in Liberia, a survey was carried out in 1984 as part of the Combatting Childhood Communicable Diseases (CCCD) project. The project, a collaborative effort of the Liberian Ministry of Health, the US Agency for International Development, and the US Centers for Disease Control, is aimed at reducing childhood morbidity and mortality through oral rehydration therapy, vaccination and treatment for malaria. As a measure of programme impact, mortality estimates from this survey will be compared with those from a second survey after 4-5 years. A sample of 40 clusters (50-70 households per cluster) was used. The size is sufficient to detect a 25% reduction in mortality of children under 5 years of age. Mortality was estimated from a pregnancy history questionnaire asked of women aged 15-49 residing in cluster households. A reliability survey was conducted and pregnancies were matched to determine the level of omission of births and deaths. Results show a very high level of mortality with a risk of death in infancy above 20% and a risk of dying before the fifth birthday of one-third. Since the extent of omission of deaths in the first survey proved substantial, the reinterview survey was essential.

Immunization, oral rehydration therapy and malaria chemotherapy among children under 5 in Bomi and Grand Cape Mount counties, Liberia, 1984 and 1988.

As part of an evaluation of child survival programmes in 13 African countries, cluster surveys were carried out in two Liberian counties in 1984 and 1988 to measure use of three primary health care services: immunization of infants, antimalarial treatment of children with fever, and oral rehydration of childhood diarrhoea. Immunization rates increased (30-53% for DPT-1 and 13-33% for measles), treatment of malaria with drugs available in the home increased from 5 to 35%, and home use of sugar-salt solution to prevent dehydration remained essentially unchanged, 5.9% in 1984 and 3.8% in 1988.

Infant and child mortality in two counties of Liberia: results of a survey in 1988 and trends since 1984.

A baseline survey of childhood mortality in two counties of Liberia in 1984 found the risk of dying before age 5 to be almost one-third. Three years into the Combatting Childhood Communicable Diseases (CCCD) project, a survey using a pregnancy history questionnaire was conducted in the same clusters to determine if any change in mortality had occurred. Reinterviews were done in a subsample and pregnancies were matched from the two surveys to determine levels of missing events. After adjustment for omission, infant mortality was estimated at 180 per 1000, a 25% decline from the estimated 1984 level. Childhood mortality declined by an estimated 28%. Tabulations of death by reported cause using a verbal autopsy questionnaire showed that the risks of neonatal tetanus and fever associated deaths declined significantly. These reductions might have been a direct result of programme activities which were shown by a marked increase in tetanus toxoid immunization and access to antimalarial drugs in the study area.

Endocrine and body growth traits in heifers exposed to testosterone-propionate during early fetal development.

This study was conducted to determine the effects of testosterone-propionate exposure during fetal development on sexual differentiation and growth rates in heifers. Ten pregnant cows were given subcutaneous injections of testosterone-propionate (250 mg/injection) every other day during d 40 to 60 of gestation. Four cows aborted after the end of testosterone treatment, while four heifers (androgenized females) and two bulls (androgenized males) were produced from the six remaining pregnant, testosterone-propionate treated cows. Calves from cows that did not receive exogenous hormone treatment were used as controls. At 8 mo of age, the androgenized heifers and control heifers and control steers were challenged with 1 mg estradiol-17 beta to induce a preovulatory luteinizing hormone (LH) surge. Two weeks later, pituitary responsiveness to exogenous luteinizing hormone releasing hormone (LHRH; 75 micrograms) was evaluated in androgenized heifers and in control heifers and control steers. To monitor growth rates, all animals were weighed at 28-d intervals from birth to 380 d of age. Androgenized females exhibited a partially masculinized phenotype as well as internal male reproductive structures. Treatment with estradiol-17 beta first depressed (P less than .05) serum LH concentrations in all animals, then induced (P less than .05) a preovulatory-like LH surge in control and androgenized females. Control steers did not (P greater than .05) exhibit a preovulatory-like LH surge following administration of estradiol-17 beta. Exogenous LHRH treatment stimulated peak LH concentrations (P less than .05) to a greater extent in control and androgenized females than in control steers.(ABSTRACT TRUNCATED AT 250 WORDS)

Bioavailability of residues: current status.

1. Bioavailability studies and current methodologies provide a very useful system for assessing the safety of radioactive drug related residues in food-producing animals. 2. Two year chronic toxicity studies provide useful information regarding the toxic properties of the parent drug but they have limited value for the assessment of safety for "second-pass" exposure of radioactive drug related residues of food-producing animals. The relevancy of the traditional two year toxicity study is seriously questioned as a method to determine the safety of drug related residues on the basis of a "second-pass" exposure. 3. More relevant toxicologic information can be gained by using the food-producing animal target species in toxicology studies. Comparative pharmacologic and toxicologic differences between laboratory animals and food-producing animals would be reduced.

Pituitary uptake of 125I-D-Leu6, Des-Gly N2(10) LH-RH-ethylamide in ovariectomized rats pretreated with oestradiol-17 beta.

The objective of this study was to determine if pretreatment of ovariectomized rats with oestradiol-17 beta affects the anterior pituitary uptake of 125I-D-Leu6, Des-Gly NH2(10)-LH-RH-ethylamide (125I-D-Leu6-LH-RH). Oestradiol-17 beta (0.5 microgram/0.5 ml oil) or oil was administered to ovariectomized rats at 2, 4, 8, 12, 16, 20 or 24 h before death, and at 30 min before death, 5 ng 125I-D-Leu6-LH-RH were injected intravenously. The serum LH response to analogue administration in oil-treated rats did not change over time, but that in oestradiol-treated rats was depressed for 4 h and restored 8-24 h after oestradiol treatment, with the greatest response being at 16 h. However, the pituitary (adrenal, CNS cortex and thyroid) uptake of 125I-D-Leu6-LH-RH in oestradiol-treated and control rats did not change over the 24-h time period. These data suggest that oestradiol-17 beta does not affect pituitary responsiveness to 125I-D-Leu6-LH-RH by inhibiting or facilitating the uptake of this analogue by the anterior pituitary.

The source of the 5-alpha-pregnanes that occur during gestation in mares.

[1,2,6,7-3H]Progesterone was injected into the uterine artery of umbilical vein of 4 pregnant Ponies to determine whether 5 alpha-pregnane-3,20-dione (DHP), 20 alpha-hydroxy-5 alpha-pregnan-3-one (20 alpha-ol), and 3 beta-hydroxy-5 alpha-pregnan-20-one (3 beta-ol) are produced by the placenta, fetus, or mare during late gestation. Plasma samples were collected from indwelling catheters in the uterine artery and vein and the umbilical artery and vein at frequent intervals until 6 h after isotope injection. The plasma samples were extracted with organic solvents and the respective pregnanes were isolated by thin-layer chromatography. Mean plasma levels of radioactive DHP in the umbilical vein were greater (P less than 0.05) than those in the umbilical artery but were similar to those in the uterine artery and vein. Plasma levels of radioactive 20 alpha-ol in the umbilical artery and vein were less (P less than 0.05) than those in the uterine artery but similar to those in the uterine vein. Levels of radioactive 3 beta-ol in the umbilical artery were greater (P less than 0.05) than those in uterine artery and vein and similar to those in the umbilical vein. We suggest that DHP was produced by the placenta and a maternal source, that 20 alpha-ol was primarily of maternal origin, and that 3 beta-ol was formed primarily by the fetus.