In pancreatic islets, glucose metabolism is a key process for insulin secretion, and pregnancy requires an increase in insulin secretion to compensate for the typical insulin resistance at the end of this period. Because a low-protein diet decreases insulin secretion, this type of diet could impair glucose homeostasis, leading to gestational diabetes. In pancreatic islets, we investigated GLUT2, glucokinase and hexokinase expression patterns as well as glucose uptake, utilization and oxidation rates. Adult control non-pregnant (CNP) and control pregnant (CP) rats were fed a normal protein diet (17%), whereas low-protein non-pregnant (LPNP) and low-protein pregnant (LPP) rats were fed a low-protein diet (6%) from days 1 to 15 of pregnancy. The insulin secretion in 2.8 mmol l(-1) of glucose was higher in islets from LPP rats than that in islets from CP, CNP and LPNP rats. Maximal insulin release was obtained at 8.3 and 16.7 mmol l(-1) of glucose in LPP and CP groups, respectively. The glucose dose-response curve from LPNP group was shifted to the right in relation to the CNP group. In the CP group, the concentration-response curve to glucose was shifted to the left compared with the CNP group. The LPP groups exhibited an "inverted U-shape" dose-response curve. The alterations in the GLUT2, glucokinase and hexokinase expression patterns neither impaired glucose metabolism nor correlated with glucose islet sensitivity, suggesting that β-cell sensitivity to glucose requires secondary events other than the observed metabolic/molecular events. 相似文献
A total of 51 seven-week-old English Cocker Spaniel puppies were measured for dominant–aggressive behaviour using the Campbell Test. The dogs consisted of a F1 full sibs and half sibs from matings of 4 sires with 10 dams. The purpose of this study was to determine if the variability observed in this behavioural characteristic has an additive genetic component and if so, to estimate heritability (h2). Coat colour and sex were examined as fixed effects.
According to the results of the study: (1) there are highly significant differences between sexes; with males being more dominant than females, regardless of coat colour; (2) there are highly significant differences in aggressive behaviour depending on coat colour with greater to lesser dominance found in golden, black and particolour coats in that order; (3) there is no interaction between sex and colour when exhibiting greater or lesser dominance; (4) heritability, estimated on sire components, is , indicating that the variability observed in dominant–aggressive behaviour is in part due to genetic factors; and (5) heritability estimated on dam components is , which implies that the maternal effect (genetic and environmental) is an important factor in this type of behaviour.
It is concluded that there is an additive genetic, and therefore, hereditary factor for dominant–aggressive behaviour in the English Cocker Spaniel. Some of the fixed factors include: sex (males are dominant over females), coat colour (golden-coated are the more dominant dogs followed by the black-coated and finally by the particolour coat dogs) and the common environmental effect due to litter. 相似文献
Communal care of young may occur when related females live in close proximity to each other. The degree of relatedness between females may affect discrimination of own from conspecific young. Retrieval tests were used to examine preference for own versus conspecific pups by inbred and outbred rats. Dams were given retrieval tests in a neutral arena every other day from day 1 through 10 postpartum. Outbred, but not inbred, dams showed a significant preference for their own pups. Outbred dams also retrieved pups more slowly than did inbred dams. Differences in the behavior of dams and/ or similarity of cues presented by pups may be responsible for the lack of preference for own pups shown by inbred dams. The results of this study suggest that indiscriminate care of young should occur when closely related females share a nest. 相似文献
Summary Morphological variability was studied in two populations of Plantago lanceolata using diallel analysis. In each population, reciprocal crosses between all possible pairs of ten plants were made. In the greenhouse, six members of each family were grown and many characters were measured. Using the model of Cockerham and Weir, the contributions of the different genetic variance components were calculated. From earlier papers it was postulated in advance to what extent and by which effect the characters in both populations were genetically determined. The populations had been differentiated for life history and morphological characters, and varied also in the relative contribution of genetic components to variability. In the Merrevliet (Me) population, where strong biotic selection was assumed, low levels of additive-genetic variability were present and the relative dominance appeared to be high. The contrasting population, Westduinen (Wd), which is abiotically controlled and shows strong environmental variability, possessed higher levels of additive-genetic variability and lower levels of relative dominance. It is possible that differential natural selection has diminished additive-genetic variability to different extents in both populations: plasticity and environmental heterogeneity prevented the loss of additive-genetic variability in Wd, whereas in the stable population, Me, natural selection had the opportunity of not only changing the means of the characters but also of diminishing additive-genetic variability to a great extent.Grassland Species Research Group Publication No. 146 相似文献
This paper estimates dynamic random effects models for intakes by dietary energy, protein, calcium, iron, zinc, niacin, riboflavin, thiamin, and vitamins A, C, D, and E 100 of Kenyan school children (6-9 years) within a multivariate longitudinal framework. The explanatory variables were socioeconomic and background variables, children's body mass index, and maternal education, cognitive test scores and morbidity spells. The model parameters are estimated using the maximum likelihood method controlling for unobserved between-children differences. The main finding is that while maternal education was usually not a significant predictor of dietary intakes, maternal scores on cognitive tests did strongly predict them. Moreover, the paternal cognitive scores and maternal morbidity levels were not significantly associated with the intakes, but an index of socioeconomic status and cash income was a significant predictor. The results indicate the need to consider broader measures of human development and of devising suitable educational programs for women without formal education. 相似文献
This study reports the findings of an integrated, comprehensive analysis of lactation energetics in harp seals conducted
using longitudinal measurements of mass, body composition and milk composition from mother-pup pairs in conjunction with water
flux measurements in pups. The nursing period of harp seals is a short, intense and relatively efficient period of energy
transfer from mothers to pups. The average daily milk intake for pups was 3.65±0.24 kg which is equivalent to 79.5 MJ of energy.
Eighty-one per cent of the energy received in the milk was metabolisable and 66% of the energy was stored by the pups as body
tissue. The field metabolic rate of pups was 3.9±0.4 time basal metabolic rate. The pups were growing at a rate of 2.2 kg
per day during the nursing period. The distribution of this mass gain varied in terms of tissue composition, depending on
the age of the pups, but over the whole nursing period approximately half of the tissue was stored as fat. Harp seal mothers
lost an average of 3.1 kg per day during lactation which was composed of 37% water, 50% fat, 11% protein and 2% ash. Mothers
spent half of their time during the lactation period actively diving and only one-third of their time on the surface of the
ice. Milk compositional changes followed the normal phocid pattern with increasing fat content and decreasing water content
as lactation progressed. The mean mass transfer efficiency was 73%. However, this value cannot be used without qualification
because female harp seals in this study fed to varying degrees, consuming an estimated 0–4.8 kg of fish per day. Feeding does
not appear to be required in order to achieve the energy requirements for lactation, given the energy stores possessed by
females, and some females do fast through the entire period so feeding may be considered opportunistic in nature.
Accepted: 25 April 1996 相似文献
The need to rebuild Pacific ocean perch, Sebastes alutus, populations on the west coast of the United States has precipitated a need to better understand the life history characteristics
of this rockfish species. One such characteristic is mating behavior, which has the potential to influence the amount of genetic
diversity in a population. We documented and examined the frequency of multiple mating in Pacific ocean perch collected off
the Oregon coast using five microsatellite loci. We found that 47 of 66 (71.2%) females examined had broods sired by multiple
males. The mean number of sires per brood was 1.92 (SD = 0.76) and ranged from 1–4. Polyandrous females were significantly
larger and had an older average age than monogamous females. Our results suggest that polyandrous behavior among female Pacific
ocean perch off the coast of Oregon is prevalent, is related to female size and age, and should be preserved by maintaining
a natural age structure in this population. 相似文献
The possible association between a high fat diet and increased breast cancer risk has remained controversial. This largely reflects the conflicting data obtained from migrant, case control and animal studies, which generally support this association, and cohort studies which often fail to show a link between fat and breast cancer. The mammary gland is particularly sensitive to estrogens during the fetal development, leading us to hypothesize that dietary fat levels during this period may significantly influence breast cancer risk. Using chemically-induced mammary tumors in rats as our experimental model, we have demonstrated the ability of a maternal diet, high in the polyunsaturated fatty acid (PUFA) linoleic acid, to alter mammary gland differentiation, accelerate the onset of sexual maturation, and increase breast cancer risk. The mammary glands of female rats exposed to a highfat diet in utero have more of the undifferentiated structures (terminal end buds) and fewer of the differentiated structures (alveolar buds) than the glands of rats exposed to a low-fat diet in utero. Furthermore, these mammary glands contain lower levels of total estrogen receptors and have reduced total protein kinase C activity. These effects appear to be mediated by an increase in tne serum estradiol levels of pregnancy, which are elevated at least 30% in pregnant dams fed a high fat diet. Furthermore, the administration of estradiol to pregnant dams produce effects on mammary gland development, onset of puberty and sensitivity to chemical carcinogenesis comparable to those seen in the offspring of rats fed a high fat diet during pregnancy. Our results, thus, support the hypothesis based on epidemiological data that high maternal estrogen levels increase daughters' breast cancer risk. The results also suggest that a high-fat diet may be an important factor in increasing pregnancy estrogenic activity. 相似文献