Studies of [125I]-EGF binding to the rat placenta, amnion and yolk sac were carried out on days 14, 17 and 20 of gestation. In the placenta EGF binding was detectable on all 3 days; in the amnion EGF binding was undetectably low on day 14 but was present on days 17 and 20, while in the yolk sac EGF binding was undetectably low on all 3 days. Although Scatchard analysis of EGF binding to placental tissue raised the possibility of high and low affinity receptors, a statistical analysis of the ligand binding data was consistent with the presence of only one type of EGF receptor. The overall affinity of the receptors did not change with stage of gestation. However, the concentration of EGF receptors was lower in placental tissue on day 17 than on days 14 or 20 of gestation; the receptor concentrations were similar on days 14 and 20. It is suggested that EGF binding to the placenta, amnion, and yolk sac may reflect the levels of cell proliferation in those tissues in the latter part of gestation.

Amnion↗

PubMedDate not supplied

Neurobehavioural development of the golden hamster.

The aim of this study was to establish a developmental profile for the golden hamster by using a systematic sequence of test procedures. One experimentally naive litter was tested each day from 0 to 25 days of postnatal age. The appearance of developmental landmarks (physical features and reflexes), spontaneous behaviour in an open field, homing behaviour and rota rod performance were studied. Infant mortality through infanticide was recorded in undisturbed and tested hamsters. The results indicated that most of the tests employed in the present study can be applied usefully in the evaluation of the neurobehavioural development of the golden hamster. The developmental profile for this species is described in detail. In comparison to rats and mice, hamsters display accelerated development of a number of characteristics, most notably incisor eruption and vaginal opening. Infanticide, the most troublesome problem in studies in which hamster litters must be disturbed, did not occur after day 3. As most reflexes and sensory abilities develop after this age, hamster pups can be used successfully in behavioural teratology evaluation.

Aggression↗

PubMedDate not supplied

Quantitative histological changes in the small intestine of rats artificially reared on different milk substitutes.

Growth of the small intestine was studied in rats reared normally by their mothers (MR) or artificially reared (AR) by intragastric infusion of milk substitutes from postnatal day 5. Two milk substitutes were used: one high in carbohydrate and low in protein as compared with rats' milk (Messer) and the other closely resembling rats' milk in its composition (Auestad). Pups reared on these formulae are termed ARM and ARA, respectively. Pups were killed at 7, 12, and 20 days for quantitative histological measurements on transverse sections of duodenum and ileum. They included cross-sectional areas of muscle and of mucosa and submucosa combined (other tissue), internal and external perimeters, and length of longest villus profile. Artificial rearing affected mucosal and submucosal measures, but did not affect muscle. The effects depended on age, type of milk substitute, and site within the small intestine. There was a tendency for deficient growth of small intestine in the early stages of artificial rearing, especially in the ileum of ARA pups. Enhancement of growth as shown by cross-sectional area of mucosa and submucosa and by longest villus profile occurred later--by 12 days in the duodenum and by 20 days in the ileum of ARM pups. Enhanced growth was less evident in ARA rats, being apparent only in the duodenum, and not until 20 days were the cross-sectional area of mucosa and submucosa and the longest villus profile increased.

Animal Nutritional Physiological Phenomena↗