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The cell populations of the occipital cortex were examined in young rats subjected to different sensory experiences. In one series recently weaned animals were reared in enriched, impoverished or control environments. The enriched environment was obtained by keeping the animals among "toys" and other rats; the impoverished environment, by rearing the animals one per cage in a darkened, quiet room; and the control environment, by housing the animals three per cage under usual animal room conditions. Six recently weaned rats were kept in each environment for 30 days and ten, for 80 days. In a second series suckling rats were handled daily. Handling consisted of touching, holding and rubbing rat pups for 15 minutes per day during the first ten days after birth; twelve rats were studied, six handled and six unhandled controls. In the two series, the animals were sacrificed under anesthesia by perfusion with mixed aldehydes. Semithin epon sections of occipital cortex were stained with toluidine blue; neurons and the three main types of glia were enumerated. In addition, the thickness of the cortex was measured and the glial cells of corpus callosum counted in the animals exposed to the three environments for 80 days. Under the influence of the enriched environment, the occipital cortex enlarged, the number of oligodendrocytes increased over the controls by 27-33% in the 30- and 80-day groups and the number of astrocytes, by 13% in the 80-day group. Within the cortex, only certain layers showed the increase in glial numbers. In the corpus callosum, however, the numbers of glial cells did not differ from those in controls. In the animals exposed to the impoverished environment, neither the size of the cortex nor the number of oligodendrocytes and astrocytes differed from controls. The animals subjected to handling also showed evidence of cortical enlargement, but the only significant change in glial cells was a 12% increase in astrocytes. It is concluded that handling and enrichment produce changes in anatomical indices of neural function including depth of cortex and numbers of glial cells. The glial response was specific to the type.of manipulation since astrocytes were predominantly affected by handling and oligodendrocytes, by enrichment. The effect of handling on astrocytes may be attributed to the stimulation being applied at a time of astrocyte proliferation, whereas the effect of enriched environment on oligodendrocytes occurred at a time of active production of these cells. The differences in cell numbers were explained by changes in the rate of cell population growth; since the impoverished did not differ from the control animals, the changes probably consisted of growth acceleration in the enriched animals rather than diminution in the impoverished ones.
The parents chosen to continue 10 independent selection lines of Schizophyllum commune over eight successive generations of selection, along with unselected controls, have been retrospectively examined for their response to growth at 15 degrees, 20 degrees, 25 degrees, 30 degrees and 35 degrees C. The regression of rate of growth on temperature was essentially linear over the range 15 degrees to 30 degrees C for all lines in all generations as was also the regression of rate of growth on various biological assessments of the environments over the whole temperature range. Either regression, therefore, provided linear regression coefficients which adequately accounted for the relative sensitivities of the lines to temperature in each generation of selection. These measures of environmental sensitivity confirmed our earlier report that selection for high mean performance in a good environment or for low mean performance in a poor environment leads to selections that are more sensitive to environmental variation than selections for high mean performance in a poor environment or for low mean performance in a good environment. These differences in sensitivity emerge as correlated responses during selection and the magnitude of these correlated responses is higher in the good environment than in the poor environment irrespective of the direction of selection. The environmental sensitivity of selection lines can be modified in either direction as required by either selecting for sensitivity simultaneously with the selection for mean performance or by selecting for mean performance in an above or below average environment. The quality of environments in which artificial selection is usually carried out is likely to have led to high selections with maximum environmental sensitivity and low selections with minimum sensitivity.
Within-line family selection was carried out at an optimum (33 degrees C) and two stress temperatures (28 degrees C and 38 degrees C) for increasing egg number laid by virgin females of Tribolium castaneum from the 7th to the 11th day after adult emergence. A control was maintained throughout the experiment. Two replicated lines were selected at each temperature and all selected lines were tested in each of the three environments. Direct and correlated responses to selection in different environments have been analysed in order to study implications of genotype-environment interaction on the selection outcome. Although selection at the optimum environment has been the most effective it did not confer the specialisation needed for performance in stress environments. However, selecting in adverse environments led to a broader range of performance over environments, which in one case (38 degrees C) included the optimum one. The degree of adaptation to adverse environments was mainly determined by the magnitude of the genetic correlation between performances in the adverse and the optimum environments. The evolution of such correlations through selection has also been investigated.
Two trials involving 96 weanling pigs were conducted in which pigs were maintained in constant thermal environments of 20 degrees (cool) or 32 degrees C (hot) and self-fed fortified corn-soybean meal-whey diets that contained three amino acid regimens (.7, 1.0, or 1.3% lysine; approximately 13.6, 17.8, and 22.0% CP) without and with 5% added fat (choice white grease) for 42 d. The pigs were weaned between 28 and 32 d of age (8.07 +/- .58 kg) and penned in groups of two. Pigs in the cool environment consumed more (P < .01) feed and ME, gained more (P < .01) weight, and retained more (P < .01) body protein, fat, and water than those housed in the hot environment. As dietary lysine level increased, daily BW gain and body protein and water accretion increased linearly (P < .01) from d 0 to 21 and quadratically (P < .01) from d 21 to 42 in both environments. However, the magnitude of these responses was less (P < .05) in the cool than in the hot environment. Dietary fat addition decreased (P < .05) gain:ME ratios and body protein and water accretion from d 0 to 21 in both environments, but the magnitude of the reduction was greatest in pigs fed the low lysine diets in the hot environment. Based on these data, the growth response of weanling pigs to dietary lysine and fat levels is dependent on the thermal environment in which the animals are housed.
In four trials, 480 weanling pigs were housed in a conventional nursery maintained at 20 or 30 degrees C, which represented a cool and hot thermal environment, respectively. They were allowed ad libitum access to corn-soybean meal-dried whey diets containing .7, 1.0, or 1.3% lysine and 0 or 5% added fat (choice white grease). The pigs were weaned between 27 and 33 d of age (7.27 +/- .90 kg) and penned in groups of five for the duration of the 42-d trials. Pigs housed in the cool environment consumed more feed (P < .01), gained more weight (P < .01), and utilized feed more efficiently (P < .01) than those in the hot environment. As dietary lysine levels were increased in the 20 and 30 degrees C environments, daily weight gains and gain:feed ratios increased linearly (P < .01) from d 0 to 21 and quadratically (P < .01) from d 21 to 42. However, the magnitudes of the increases were less in the cool environment, resulting in temperature x lysine interactions (P < .05). As the pig's feed intake, body weight, and heat production increased over time, the 20 and 30 degrees C environments became progressively warmer relative to the animal's zone of thermoneutrality. The associated reductions over time in energy and lysine intakes relative to the pigs' maintenance needs resulted in an increase in the concentration of dietary lysine needed to maximize rate and efficiency of gain in the 30 degrees C environment but not in the 20 degrees C environment (temperature x lysine x period interaction, P < .10).(ABSTRACT TRUNCATED AT 250 WORDS)
This study was designed to determine whether brief exposure to an enriched environment around the time of weaning would affect learning and memory processes in young rats. In addition, this study sought to determine if experience in an enriched environment would alter hippocampal protein kinase C (PKC) which is thought to be a possible neural substrate that underlies learning and memory processes. Animals were either reared in an enriched environment or standard laboratory cages starting at 15 days old. After 6 (21 days old) or 12 (27 days old) days subjects were either tested in the Morris water task, or had the hippocampus removed for biochemical analysis of PKC activity. Morris water task results showed that compared to laboratory reared controls, the performance of subjects reared in the enriched environment for 12 days, but not 6 days, was improved. In addition, 12 days of exposure to the enriched environment, but not 6 days, produced more cytosolic hippocampal PKC activity. The particulate fraction appeared not to be affected by rearing in the enriched environment. Brief exposure to an enriched environment around weaning, therefore, both improved Morris water task performance and increased hippocampal PKC activity. These outcomes suggest that performance in the Morris water task and hippocampal PKC may be functionally related.
The objective of this study was to learn the course of child's adaptation process to school and family environment following the neoplastic disease. The study also aimed select the environment and personality factors influencing adaptation effect. The study pertains to the child's personality and how it works at home and at school. It also tries to get to know the child's environment. 65 children of different social environment were studied. Motor functions of these children were limited as the result of tumour disease. Special scale of adaptation was prepared when the research was over. By means of this sale two groups of children were distinguished: those who were well adapted to the environment and those who were not. Statistical analysis was used to compare the groups on account of the following factors: health factors including: a kind of tumour, duration of the disease, prevalence of pain, manipulation and locomotive abilities, visibility of handicap; sociological factors including: age and sex of studied persons, the place of residence and education of parent's, living standard of the family, a degree of family participation in cultural life of the society, mother's attitude towards the insane child. These factors allow to formulate the following dependences: The more a level of the child's locomotive functions, following neoplastic disease approaches to the standard, the more favourable course takes the process of child's adaptation to the family and peers. If a neoplastic disease leaves permanent and always visible handicap then child's adaptation effect to the environment is not favourable. An active participation of the family in socially life is beneficial for regular adaptation of a child. Personality development as the result of participation in cultural life allows socially accepted defence mechanism to work in stress situations connected with the disease. Parent's rational attitude towards an insane child correlates with a beneficial child's adaptation to an environment. Other factors did not differentiate the two groups statistically. During clinicalontgenetic analysis concerning particular studied cases, 3 models of nonfunctional adaptation were distinguished: maladjustment of aggressive type prevailing among the children with permanent physical handicap coming of families characteristic for socially nonaccepted standard of behaviour; maladjustment of neurotic type prevailing among the children coming of compliant families whose adult members manifest neurotic vegetative reactions in difficult situations.(ABSTRACT TRUNCATED AT 400 WORDS)
KEY MESSAGE: Perennial ryegrass shows extensive genotype x environment interactions at the limit of its ecological niche. Accounting for GxE may improve prediction even when environmental and genetic samples are highly diverse. BACKGROUND: In breeding the aim is to identify and accumulate beneficial variants. However, detection of these variants may be challenging in the presence of extensive genotype x environment interactions (GxE). METHODS: The study assesses the performance of 264 diploid perennial ryegrass accessions in a multi-environment field trial. We investigate the extent of GxE, for yield (total dry matter) and persistence traits under environmental conditions experienced in Nordic and Baltic regions at the limit of the species distribution. Two different approaches to modelling GxE were tested and validated under three different breeding scenarios. RESULTS: Our analysis documented the presence of significant GxE for all traits. Validation showed improvements in prediction accuracy when accounting for GxE: up to 4% for yield when predicting in unobserved environments, and up to 22% and 9% for spring cover and winter kill, respectively, when predicting unobserved germplasm. Genome-wide-association-studies (GWAS) were utilized to detect genetic variants with marginal effects (environment-independent effect) and conditional effects (environment-dependent effects). Results showed the presence of large-effect genetic variants with marginal effects, in addition to few Quantitative Trait Loci (QTL) whose effects were adaptive under specific environmental conditions while neutral or deleterious under different environmental conditions. CONCLUSION: This study demonstrates the usefulness and limitations of genomic prediction models for predicting GxE in highly diverse samples and describes the extent of GxE at the limit of species distribution for perennial ryegrass. Our study points towards adaptive variation which may enhance persistence of perennial ryegrass populations in Nordic and Baltic growing conditions.