Following bilateral lesions of the globus pallidus, rats living in a residential maze were hyperactive during the 12 hr dark cycle but not during the 12 hr light cycle. Lesioned rats were less exploratory during the light cycle than control rats but not during the dark cycle. Exploratory behavior of rats was photographed for 15 min during the light cycle. The duration of 6 behavior acts was significantly shorter than controls (scratching, grooming, sitting, sniffing, standing and rearing). The number of initiations of grooming, scratching, sniffing and smelling decreased while looking and walking increased in frequency. The linkage of behavior acts into sequences was diminished compared with controls. Similar, but not identical, changes were found when the structure of exploratory behavior of naive rats was compared with the exploratory behavior of experienced rats. It is concluded that naive control rats are hyperactive relative to experienced rats in this exploratory situation and that rats with pallidal lesions display changes in their behavior which are characteristic of hyperactive animals even when other tests under similar conditions, such as exploration during the light cycle in a maze, show the pallidal rats as hypoactive relative to control rats.

Animals↗

PubMedDate not supplied

Correlation of behavior with brain damage after in utero exposure to toxic agents.

Early postnatal behaviors involving sensorimotor integration were measured along with thickness of the sensorimotor cortex in rats irradiated with 1.0 Gy on gestational day 11 or 17. Body weight and morphology of anterior pituitary cells were recorded. Irradiation on day 17 was more effective in reducing cortical thickness and body weight and performance on behavioral tests and less effective in altering pituitary cells than irradiation on day 11. Prediction of behavioral effects, using cortical layers, body weight and pituitary morphology as predictors in stepwise multiple regression, was measured in both irradiated and control rats. Cortical Layer V more than I more than IV and VI as significant predictors of behavior. The best predictions accounted for about half of the variance in the data. When behavioral data were used to predict brain damage, the best predictor was negative geotaxis. Significant association of behavior with Layers V and VI was found. These experiments show the difficulties in correlating complex behaviors with specific brain areas and, at the same time, implicate especially Layer V of the sensorimotor cortex in these behaviors.

Animals↗

PubMedDate not supplied

Comparison of functional and morphological deficits in the rat after gestational exposure to ionizing radiation.

Ionizing radiation is a precise tool for altering formation of the developing cerebral cortex of the fetal rat. Whole body exposure of the pregnant rat on gestational day 13, 15 or 17 to 1.0 Gy of gamma radiation resulted in maximum thinning of the cortex on days 15 and 17. In the preweaning period, functional tests (negative geotaxis, reflex suspension, continuous corridor and gait) were most affected by irradiation gestational day 15, as was body weight. When a lower dose of radiation (0.75 Gy) was used on gestational day 15, the damage to the cortex was much less but behavioral changes were still present. Frontal, parietal and occipital areas of the cortex were approximately equally affected. Using stepwise multiple regression analysis, the linkage of functional tests and cortical thickness was examined. Functional variables which were most commonly included as predictors of frontal and parietal cortex were negative geotaxis and continuous corridor. Occipital cortical layers were not predicted by behavioral variables. In predicting function using cortical variables, frontal cortex was better than parietal and occipital cortex was the poorest predictor.

Animals↗

PubMedDate not supplied

Ionizing radiation and the developing brain.

The unique susceptibility of the central nervous system to radiation exposure is attributable to its extensive period of development, the vulnerability of its neuronal cells, the migratory activity of many of its cells, its inability to replace mature neurons, and the complexity of the system itself. Radiation effects may be due to glial or neuronal cell death, interruption of migratory activity, impaired capacity to establish correct connections among cells, and/or alterations in dendritic development. These structural changes are often manifested as behavioral alterations later in life. Sensitivity to radiation (dose-response) is markedly similar among all mammalian species when developmental periods are compared. This review compares and contrasts human and animal behavioral data. Neonatal and postnatal adult behavioral tests have been shown to be sensitive, noninvasive measures of prenatal radiation exposure, although currently their predictive validity for humans is uncertain. Additional research is needed to determine the presence and significance of postnatal morphologic and functional alterations due to prenatal exposure to low levels of ionizing radiation.

Animals↗

PubMedDate not supplied

Progressive behavioral changes in rats after exposure to low levels of ionizing radiation in utero.

The deleterious effects of ionizing radiation on the developing brain may be not only prolonged but progressive. Fetuses were exposed to 0.75 Gy of ionizing radiation on gestational day 15 through whole body exposure of the pregnant rat. Three behavioral tests (gait analysis, continuous corridor activity and photographic analysis of sequences of behavioral acts) were performed at 1 and 3 months, postnatally. Body weight and thickness of the cerebral cortex of irradiated rats were 10-15 percent below controls throughout the period of study. Behavior in all tests was more affected at 3 months than at 1 month of age. Gait of control rats, as measured by the angle of advanced of hind feet, widened about 20 percent for males and 40 percent for females from 1 to 3 months, as expected, while, in irradiated rats, the angle widened only about 10 percent. Continuous corridor activity increased less than 10 percent in controls and about 35 percent in irradiated rats over the same period. In photographic analysis of behavior, controls increased their time spent standing by about 50 percent in males and 20 percent in females from 1 to 3 months of age. Irradiated males increased time standing only about 10 percent and irradiated females decreased about 30 percent over the same period. The data obtained in these experiments support other evidence that some behavioral alterations from perinatal exposure to radiation become more marked with maturation.

Age Factors↗

PubMedDate not supplied

Moral reasoning among graduate students in nursing.

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Adult↗

PubMedDate not supplied

Trends in Medicaid physician fees, 1993-1998.

This study uses data on Medicaid physician fees in 1993 and 1998 to document variation in fees across the country, describe changes in these fees, and contrast how they changed relative to those in Medicare. The results show that 1998 Medicaid fees varied widely. Medicaid fees grew 4.6 percent between 1993 and 1998, lagging behind the general rate of inflation. This growth was greater for primary care services than for other services studied. Relative to Medicare physician fees, Medicaid fees fell by 14.3 percent between 1993 and 1998. Medicaid's low fees and slow growth rates suggest that potential access problems among Medicaid enrollees remain a policy issue that should be monitored.

Data Interpretation, Statistical↗