The purpose of the present investigation is to evaluate the restraining effects of protecting jackets attached from the pre-mating period and thereafter up to completion of the fetal organogenesis in rabbits. Forty (40) Kbl:NZW mated rabbits 6 to 10 months of age were divided into 2 groups of 20 animals each. Animals in the treatment group (hereinafter referred to as JK group) were dressed in protecting jackets from Day −9 prior to mating (hereinafter referred to as GD −9) to GD 19 and another group of animals without protecting jackets was used as a control. The major restraining effects noted were decreases in body weight gain and food consumption, which were marked in the first 9 days of jacket-attachment during the pre-mating period. The decrease in body weight was still apparent over the whole gestation period. However, the mean body weight of the JK group finally reached the baseline level of the study at around GD 11. These findings demonstrated that the restraining effects in the present study persisted longer than those in the previous study, in which protecting jackets were used from GD 0 to GD 19 or GD 6 to GD 19. The fertility function and cesarean section findings were comparable to those in the control group. It may be concluded that the use of protecting jackets from GD −9 to GD 19 induced more prolonged effects on body weight loss than in previous findings where the jackets were attached from GD 0 to GD 19 or GD 6 to GD 19 and the time of starting the acclimation with the jackets appears to play a great role in reducing body weight loss.
ABSTRACT Prenatal development of Kbl:Dutch rabbits was studied in comparison with Kbl:New Zealand white rabbits. Significantly accelerated ossification of the 5th and 6th sternebrae and a low incidence of fetuses with a 13th rib were characteristic features in the prenatal development of Kbl:Dutch rabbits in comparison with Kbl:New Zealand white rabbits. These characteristics were largely consistent with earlier studies of Dutch rabbits from different suppliers and are notable when Kbl:Dutch rabbits are used for the evaluation of skeletal ossification.
We surveyed 1053 pregnant rabbits of the Kbl:NZW strain collected from 27 developmental toxicity studies to reveal the prevalence and significance of gastric hairballs. The incidence of hairballs was 2/525 (0.4%) in the control group and 17/528 (3.2%) in the high dose group. In the high dose group, 16 dams resulted in abortion or death. In addition, decreases in body weight and food consumption were more severe in dams with hairballs than in their group-mates without hairballs.
Effects of hepatocyte growth factor were investigated in a two‐stage rat liver carcinogenesis protocol. Male F344 rats were first treated with diethylnitrosamine (200 mg/kg, i.p.) and then, starting two weeks later, with N‐ethyl‐N‐hydroxyethylnitrosamine (EHEN) for 6 weeks at a dose of 0.01% in drinking water. Hepatocyte growth factor, which was injected i.v. at a dose of 200 μg/kg body weight one (at week 3) or two times (at weeks 3 and 4) during EHEN administration, significantly increased the development of preneoplastic glutathione S‐transferase placental form‐positive foci. Although the observed effects of hepatocyte growth factor were weaker than that of the two‐thirds partial hepatectomy (PH) performed at week 3, the present results suggest that the enhancing effects of PH performed during the promotion stage may be largely mediated through induction of hepatocyte growth factor.
