Effect of different weaning ages (21, 28 or 35 days) on production, growth and certain parameters of the digestive tract in rabbits.

The effect of different weaning ages, that is, 21 (G21), 28 (G28) or 35 (G35) days, on growth and certain parameters of the digestive tract was examined in rabbits to assess the risk of early weaning attributable to the less-developed digestive system. On days 35 and 42, G35 rabbits had 10% to 14% and 10% higher BW, respectively (P < 0.05), than those weaned at days 21 and 28. In the 4th week of life, early weaned animals had 75% higher feed intake than G28 and G35 rabbits (P < 0.05). The relative weight of the liver increased by 62% between 21 and 28 days of age, and thereafter it decreased by 76% between 35 and 42 days of age (P < 0.05), with G21 rabbits having 29% higher weight compared with G35 animals on day 35 (P < 0.05). The relative weight of the whole gastrointestinal (GI) tract increased by 49% and 22% after weaning in G21 and G28 rabbits, respectively (P < 0.05). On day 28, the relative weight of the GI tract was 19% higher in G21 than in G28 rabbits, whereas on day 35 G21 and G28 animals had a 12% heavier GI tract compared with G35 rabbits (P < 0.05). Age influenced the ratio of stomach, small intestine and caecum within the GI tract; however, no effect of different weaning age was demonstrated. The pH value of the stomach and caecum decreased from 5.7 to 1.6 and from 7.1 to 6.3, respectively, whereas that of the small intestine increased from 6.8 to 8.4 (P < 0.05); the differences between groups were not statistically significant. Strictly anaerobic culturable bacteria were present in the caecum in high amounts (108), already at 14 days of age; no significant difference attributable to weaning age was demonstrable. The concentration of total volatile fatty acids (tVFA) was higher in G21 than in G28 and G35 throughout the experimental period (P < 0.05). The proportion of acetic and butyric acid within tVFA increased, whereas that of propionic acid decreased, resulting in a C3 : C4 ratio decreasing with age. Early weaning (G21) resulted in higher butyric acid and lower propionic acid proportions on day 28 (P < 0.05). No interaction between age and treatment was found, except in relative weight of the GI tract and caecal content. In conclusion, early weaning did not cause considerable changes in the digestive physiological parameters measured, but it resulted in 10% lower growth in rabbits.

Rat as model for studying behavior effects of hCG.

The demonstration of receptors for luteinizing hormone (LH)/human chorionic gonadotropin (hCG) in several parts of rat brain suggested their novel functional role. Subsequent studies tested the effect of hCG (intraperitoneally or intracerebroventricularly) on brain arousal and different types of stress situations in an intact female rat model on the day of proestrus. Treatment resulted in changes of activity and several other behavioral patterns associated with sites of brain hCG/LH receptors. hCG given peripherally caused a longer sleeping time and a decreased activity level. Whereas administration of indomethacin alone had no effect, coadministration inhibited the effects of hCG. hCG increased immunoreactive prostaglandin D2 (PGD2) and decreased PGE2 in brain areas controlling activity and sleep. hCG effects were probably mediated via prostaglandin pathways. After central hCG treatment, animals were less active and showed less exploratory behavior in an open-field box than the control animals. Taste and odor neophobias were dramatically decreased following central injection of hCG. hCG-treated rats were less anxious and exhibited a higher level of maternal interest than the controls. hCG treatment also had a beneficial effect against stress ulcer, which was prevented by pretreatment with antisense receptor oligonucleotide, suggesting a direct hCG receptor-mediated effect. In summary, because hCG can cross the blood-brain barrier, both peripheral administration and central administration affect several behavioral patterns. This effect is similar to treatment with anxiolytics and suggests the functional relevance of brain LH/hCG receptors. Some observed behavioral changes have parallels in pregnant women.

Clinical importance of vascular LH/hCG receptors--a review.

It was believed for a long time that functional LH/hCG receptors were present only in gonads. Recent studies have demonstrated, however, that these receptors are also present in several nongonadal organs in the human body. Uterus is one of them. Besides two uterine layers, endothelial cells and smooth muscle of blood vessels in the uterus also contain these receptors. In vivo administration of hCG decreased vascular resistance in the human uterus and in vitro treatment increased vasodilatory and decreased vasoconstrictive eicosanoids in the vessels. These findings led us to investigate whether hCG administration to patients with signs of threatened abortion has any beneficial effect. Patients were treated with either magnesium or progesterone and/or hCG. The results showed that the frequency of patients reaching second trimester was higher when hCG was used, which was paralleled by a significant decrease in uterine vascular resistance. Patients who reached term after treatment had decreased incidence of preterm delivery and intrauterine growth retardation. In conclusion, we suggest that uterine vascular LH/hCG receptors play an important role in the peri-implantation period by increasing uterine blood flow through vasodilatation and also perhaps through angiogenesis and trophoblast invasion, resulting in therapeutic benefit.

Peripheral and intracerebroventricular administration of human chorionic gonadotropin alters several hippocampus-associated behaviors in cycling female rats.

Our recent demonstration of receptors for luteinizing hormone (LH)/human chorionic gonadotropin (hCG) in rat brain with the highest density within the hippocampus and dentate gyrus suggests novel functional roles for gonadotropic hormones within the brain. The present study investigated whether 125I-hCG can cross the blood-brain barrier and reach hippocampus and the possible role of hCG in the regulation of several behavioral activities associated with the hippocampal formation in the rat. About 1/100th of peripherally injected 125I-hCG crossed the blood-brain barrier in an intact form and was found in cerebrospinal fluid and in hippocampus. Intraperitoneal (IP) or intracerebroventricular (ICV) injections of highly purified hCG on the morning of proestrus of cycling female rats resulted in changes in several hippocampus-associated behaviors. hCG-treated animals were generally less active and showed less exploratory behavior as compared to saline-injected control animals. There was no difference, however, in latency to enter the open field between hCG-treated and control animals. Taste neophobia was dramatically decreased following IP as well as ICV injection of hCG. No differences were found in the memory component of T-maze performance; however, the hCG-treated rats exhibited decreased stereotypic behavior. In summary, hCG can cross the blood-brain barrier, and peripheral or central administration of hCG affects several hippocampus-associated behaviors suggesting that hippocampal LH/hCG receptors are most likely involved in mediating these effects. Some of the observed behavioral changes have parallels in pregnant women.

Administration of human chorionic gonadotropin affects sleep-wake phases and other associated behaviors in cycling female rats.

We investigated the possible effects of human chorionic gonadotropin (hCG) on sleep-wake phases and other associated behaviors controlled by the medial preoptic area, cerebral cortex and hippocampus. Chronic epidural electroencephalographic (EEG) and temporal muscle electromyographic (EMG) electrodes were placed in cycling female rats. After a week of recovery, rats were injected intraperitoneally at 3.00 pm on the day of proestrus with either saline or highly purified hCG or indomethacin or hCG plus indomethacin. Three hours after injection, EEG, EMG and behavioral activities were recorded for 3.5 h. The administration of hCG increased high and low amplitude sleep, resting phase and decreased active awake phase, walking, sniffing and chewing as compared to the controls. While the administration of indomethacin alone had no effect, coadministration inhibited hCG effects. Medial preoptic area, cerebral cortex and hippocampus contain immunostaining for LH/hCG receptors. The administration of hCG resulted in an increase of immunoreactive PGD2 and a decrease of PGE2 in median preoptic area, cerebral cortex and hippocampus as compared to the controls. In summary, hCG administration affects sleep-wake phases and other associated behaviors in rats which can collectively be described as decreased activity. These effects are probably mediated by increasing PGD2 and decreasing PGE2 in areas of brain which control these activities. The above findings may be relevant to pregnant women who experience decreased activity when hCG is present in the circulation and cerebrospinal fluid.

Dexamethasone suppression test and coping behavior in psychosocial stress.

The dexamethasone suppression test (DST) and the Minnesota Multiphasic Personality Inventory (MMPI) were administered to 144 healthy inductees on day 2 of military service. One hundred and four of them completed a 120-item questionnaire describing their coping responses to this particular challenge. Thirty-six subjects (25%) failed to suppress plasma cortisol adequately. Their mean scores on the MMPI clinical standard scales were within the normal range. High postdexamethasone cortisol levels were associated with denial and passivity, and with low demand for social support. These results suggest that the DST might be more related to coping with a stressor than to a specific diagnosis. The authors speculate that high hypothalamic-pituitary-adrenal activity may have a primary role in psychological defense promoting inattention to the aversive aspects of stressful situations.

Ultrasonic fetal weight estimation in multiple and singleton pregnancy.

Thirty-five multiple and 168 singleton fetal weight estimations were made in an Australian population using the tables of Warsof et al., which have been computed from a North American population. The estimated fetal weights were compared to the actual birth weights within 96 h of estimation. Correlation coefficients of the actual birth weight with the estimated fetal weight for the total group, singleton and multiple pregnancies respectively, were 0.967, 0.969 and 0.933. The percentages of estimated fetal weights falling within 10% of the actual birth weight were for the three groups, 79.3%, 77.9% and 85.7% respectively. Individual weight sub-groups, less than 1500 g, 1500-2500 g, 2500-4000 g and greater than 4000 g, showed correlation coefficients of 0.84, 0.838, 0.839 and 0.759 respectively, which compare favourably to published studies of North American populations using this method. It is concluded that ultrasonic fetal weight estimation using the North American computerized tables of Warsof et al. is appropriate for an Australian population and is valid for both singleton and multiple pregnancies.