Influence of Litter Reduction in the Neonatal Period at Different Times after Birth on the Parameters of Brain Development in Rats.

We studied the brain of 5- and 14-day-old intact (control group) rats and rats of the same age from litters experimentally reduced on days 1 and 5 after birth (experimental groups). In animals of both experimental subgroups, the brain had morphological signs of advanced development: greater weight of the brain and hemisphere, greater thickness of the cortex, its molecular layer, lower numerical density of neurons in the anterior parietal and proper parietal lobes, greater sizes of neurons, their nuclei, and nucleoli in the neocortex of these zones, and increased concentration of RNA in the cytoplasm of neurons. These data suggest that the rate of brain development in rats can be accelerated under the influence of environmental changes that occur after litter reduction during the neonatal period at different times after birth.

Effect of Experimental Litters Reduction during the Neonatal and Suckling? Periods of Ontogeny on Some Parameters of Brain Development in 30-Day-Old Rats.

We compared the effect of litter reduction on day 1 (series I) and day 14 after birth (series II) on the weight of the brain and right hemisphere and on the morphometric indicators of the development of the anteroparietal lobe in rats. Animals from both experimental series showed signs of acceleration (higher body weight and weights of the testes and ovaries). In series I, the weight of the brain and hemisphere and the thickness of the cortex surpassed the control values; the numerical density of neurons in layers II and V was lower and the numerical density of gliocytes was higher than in the control. The size of the neuronal nuclei of these layers as well as the size of perikaryons of layer V neurons also surpassed the control. These differences can be considered as evidence of advanced brain development in experimental animals. In contrast, gravimetric and morphometric parameters in series II did not differ significantly from the control values. Thus, the factors that determine accelerated development of the brain after reduction of litter size in the neonatal period produced no similar effect after litter reduction on day 14 after birth.

Dependence of Some Indicators of Brain Development in 30-Day-Old Rats on the Dynamics of Body Weight Gain in the Neonatal and Suckling Periods in Litters of Different Sizes.

We analyzed the dependence of the weight of the brain, its hemispheres, and morphometric parameters of the parietal cortex and the hippocampus in 30-day-old Wistar rats on their body weight at the age of 1, 7, 14, 21, and 30 days. All the animals were from medium-sized litters. In 6 litters (experiment), 6 rat pups were left in each litter 1 day after delivery; in 6 other litters (control), their number remained unchanged (8-13 pups). In both groups, a positive correlation was revealed between the brain weight and body weight at the age of 1, 7, 14, 21, and 30 days. At the same time, the body weight in rats aged 7, 14, 21, and 30 days and the brain and hemisphere weight at the age of 30 days in the experimental group was significantly greater than in the control group. Rats of the experimental group had higher numerical density of gliocytes in layer II and V of the neocortex and a greater ratio of glia/neurons in these layers. The cortical neurons in the experimental rats were larger than in the control in field I of the hippocampus (p<0.05) and in layer II (p<0.05) and layer V (p>0.05) of the neocortex. The neuronal nuclei in rats from reduced litters were significantly larger than in control animals.

Immediate and Delayed Effects of Food Restriction on Some Parameters of Brain Development in Rats.

The effects of 15-day restriction diet (from 1 to 1.5 months of age) on some parameters of brain development were studied in rats. The immediate and delayed (15 days after transfer to normal ration) effects were evaluated. The immediate effects included a significant decrease of the absolute weights of the brain and hemispheres. The relative weight of the brain was significantly higher. The thickness of the cortex of the parietal lobe proper and its layer I decreased. The absolute weights of the brain and hemispheres were less than in the control 15 days after the rats were transferred to ad libitum feeding, while the relative weight of the brain was higher than in controls. The thickness of the parietal and anterior parietal cortex and the numerical density of neurons in layers II and V did not differ from the control. In the neurons of layers II and V of the anterior parietal and parietal lobe proper the nuclei were larger, while the nucleoli were enlarged in the neurons of these locations and the hippocampus, the shifts being significant in the anterior parietal layer V. The concentrations of RNA in the parietal, anterior parietal, and hippocampal lobe neurons in different groups were similar directly and 15 days after the diet. Changes in the gravimetric and morphometric parameters of the brain were paralleled by the development of oxidative stress.

Formation of Hyaline Membranes in the Lungs of Albino Rat as a Result of Exposure to Bleomycin During the Neonatal Period.

We studied the effect of bleomycin (1 mg/kg) in 1-day-old rat pups (single intraperitoneal injection) and 4-day-old pups (3 injections on postnatal days 1, 2, and 3). The formation of hyaline membranes against the background of oxidative stress was documented in all bleomycin-treated rats. Repeated injection of bleomycin (4-day-old pups) led to more pronounced destructive alterations in the lungs characterized by the formation of microcysts and atelectases as well as hypertrophy of the interstitial connective tissue. These alterations persisted in 14-day-old rats. Administration of bleomycin during the neonatal period can be a promising approach to simulation of hyaline membrane disease (respiratory distress syndrome).

Effect of Antioxidant Echinochrome A on Bleomycin-Induced Pulmonary Fibrosis.

We studied the protective effect of antioxidant echinochrome A on bleomycin-induced pulmonary fibrosis in rats at the early stages of postnatal ontogeny. Administration of echinochrome A was shown to reduce the severity of bleomycin-induced oxidative stress in the lungs, prevented the development of hypertrophy of interalveolar connective tissue and peribronchial lymphoid infiltration, and normalized the ratio of volume densities of interalveolar septa and alveolar lumen.

3ß-hydroxysteroid dehydrogenase in the brain ependymocytes.

We studied activity of 3ß-hydroxysteroid dehydrogenase in rat brain ependymocytes. Enzyme activity was found in the cytoplasm of cells lining the villi in the vascular plexuses in the lateral ventricles and cells lining the ventricles. These data suggest that ependymocyte can synthesize neurosteroids.

Effect of gonadectomy on activity of neuronal 3ß-hydroxysteroid dehydrogenase in some brain structures.

3ß-Hydroxysteroid dehydrogenase is a key enzyme in the synthesis of steroid hormones in steroid-producing organs, including the brain producing neurosteroids. 3ß-Hydroxysteroid dehydrogenase activity can be a marker of steroid-producing cells. We present the results of histochemical assay of this enzyme in the neocortex, hippocampus, and cerebellar cortex of gonadectomized prepubertal rats. The positive reaction was detected in hippocampal neurons, ganglionic layer cells of the cerebellar cortex (Purkinje cells), and solitary neocortical neurons of male and female rats. Gonadectomy significantly increased enzyme activity in neocortical (layer V) and hippocampal neurons and had no effect on the intensity of the reaction in Purkinje cells.

Effect of treatment with testosterone derivatives on morphometric characteristics and free radical oxidation in rat cerebral cortex.

Morphometric characteristics and free radical oxidation in neurons of the neocortex and hippocampus of male and female rats were studied 1 month after administration of Sustanon-250 in a dose of 8 mg/kg during the pubertal period of ontogeny. The weight of the brain was shown to decrease in males. In both female and male rats, the width of the anterior parietal lobe and the numerical density of neocortical and hippocampal neurons decreased. Sex differences were found in free radical oxidation in the cerebral cortex. The intensity of this process increased significantly in females, but decreased in males.

Histochemical detection of 3ß-hydroxysteroid dehydrogenase in neurons of rat brain.

Here we present the results of histochemical detection of 3ß-hydroxysteroid dehydrogenase in neurons of the neocortex, cerebellum, and brainstem. The positive reaction was observed in a low number of neocortical, midbrain, and pontine neurons. The maximum number of positive neurons was detected in the cerebellar cortex (Purkinje cells) and hippocampus.

Morphometric and histochemical characteristics of the neocortex and hippocampus of experimentally enlarged rat brain during the suckling period of ontogeny.

Enlargement of the brain weight was attained in rats by reducing the number of neonates in the litter. The brain of 14- and 30-day-old animals was examined (controls: intact animals from litters of average numbers). Difference between the brain weight at 14 and 30 days was about 200 mg. The parameter in the experimental rats was higher than in control: by 19.9 and 15.8% at the age of 14 and 30 days, respectively. The neocortex and hippocampus of the experimental rat brain differed by the size of the neuron cytoplasm and nucleus, these cells' count in a visual field, and activities of NADH- and NADPH-dehydrogenases in the neuron cytoplasm. During the suckling period, the differences in the weights of experimentally enlarged brain were paralleled by specific features of the cortex, morphometric and histochemical characteristics of the neurons.

Effects of infant rat fostering in artificially formed litters on the development of brain, adrenals and gonads.

Morphometric and histochemical properties of neurons in the frontoparietal and parietal lobes and CA1 hippocampal area, thickness of the neocortex, histochemical and morphometric properties of adrenals and gonads, and concentrations of sex hormones were compared in 40-day rats fostered in artificially formed (experimental group) and natural (control) litters. Animals of the experimental group had lower body and brain weight, thickness of the neocortex in the parietal lobe, sizes of nuclei and cytoplasm of layer 2 and layer 5 neurons of the frontoparietal and parietal lobes and in the hippocampus, lower NADPH-dehydrogenase activity in the hippocampus, and lower NADH- dehydrogenase activity in layer 2 neurons of the parietal lobe in comparison with control rats. RNA concentration in neuronal cytoplasm in neocortex and hippocampus was higher in rats from experimental group, than in animals from the control group. Higher estradiol concentration, higher activity of 3ß-hydroxysteroiddehydrogenase in thecal cells of ovarian follicles were found in females from experimental group; decreased testicle weight, reduced diameter of seminiferous tubules, reduced activity of 3ß-hydroxysteroiddehydrogenase in Leydig's cells, and trend forward lowering of testosterone concentration were found in males from experimental group.

Effect of long-term constant illumination of female rats on the parameters of brain development in their 40-day-old progeny.

We studied the progeny from female rats exposed to constant illumination for 1 month and mated with intact males 14 days after this exposure. At the age of 40 days, the progeny from experimental rats differed from the control by lower body weight, thickness of the adrenal cortex, and diameter of convoluted seminal tubules. The weight of the brain was similar in both groups. The thickness of the cortex in the parietal lobe, and especially, in the frontoparietal lobe was decreased; the neuronal density in these lobes (layers II and V) was reduced. In layer II and V neurons of the parietal lobe, the size of neuronal nuclei reduced, the concentration of RNA and activities of NADH and NADPH dehydrogenases in the cytoplasm were considerably increased. Elevated concentration of lipids was found in layer I of cerebral and cerebellar cortex and in the white matter, which attests to higher myelinization degree compared to the control.

Long-term consequences of prenatal exposure to lead on brain development in rats.

Administration of singe doses of lead citrate (200 mg/kg) to pregnant rats (on day 18 of pregnancy) was followed by the appearance of destructive changes in brains at age 40 days, with cysts, foci of gliocyte proliferation, pyknotic neurons, and decreases in NADH and NADPH diaphorase activities in neocortical and hippocampal neurons. Decreases in the density of neurons in the cortex and decreases in cortical thickness were also observed. The intensity of free-radical oxidation in the cortex increased three-fold, along with a 3.9-fold increase in the concentration of lipid peroxides, providing evidence of oxidative stress. The possible mechanisms by which these alterations develop are analyzed.

Effect of experimental litter reduction in female rats on parameters of brain and endocrine gland development in the progeny.

We studied the relationship between parameters of brain development, elevated plus-maze behavior, and the status of the endocrine glands in the progeny of 4.5-5- and 8-9-month-old females after litter reduction by removal of one uterine tube. The progeny of young experimental females differed from the progeny of control animals by brain weight (at the age of 1 day), morphometrical characteristics of the cortex and its neurons, activity of 3beta-hydroxysteroid dehydrogenase in the adrenal cortex (at the age of 1 and 40 days), and behavioral reactions in the elevated plus-maze (at the age of 30 days). The differences in these parameters between the progeny from old females with experimentally reduced litter size and control females were significantly less pronounced.

Effect of administration of lead nitrate to pregnant rats on the lungs in their offspring.

Lead nitrate in a dose of 200 mg/kg was administered to female rats via a gartric tube on days 5 and 12 of pregnancy. The lungs of their offspring were examined on day 40 of life. We found a decrease in the ratio between the specific volumes of alveolar lumens and interalveolar septa and hypertrophy of lymphoid tissue in the bronchial wall (compared to the offspring of intact females). Chemiluminescent analysis revealed activation of lipid peroxidation and decrease in antioxidant antiradical activity of the lungs.

Morphometric and statistical analysis of macro- and microscopic characteristics of the brain and their relationships with adrenocortical histophysiology in newborn rats.

A direct relationship between the weights of the brain and hemisphere and parameters characterizing the development of the cortex and its neurons in intact newborn rats was revealed. Parameters of brain development in newborn rats correlate with 3beta-hydroxysteroid dehydrogenase activity in the adrenal zona glomerulosa.

Effect of testosterone derivatives administered to pregnant rats on the brain of their offspring (delayed consequences).

We examined the offspring of rats receiving sustanon with testosterone derivatives on day 19 of pregnancy. At the age of 1 month, these rats differed from control animals in the indexes of higher nervous activity. The relative weight of the brain increased in 54-day-old rats receiving the hormone. Female rats were characterized by increased sudanophilia of the white matter in cerebellar hemispheres and high RNA content in layer V neurons of the parietal lobe, increased volume of nuclei in hippocampal neurons, weight of the ovaries (tendency), size of the largest follicles, and high activity of 3beta-ol-steroid dehydrogenase. The weight of the adrenal glands and 3beta-ol-steroid dehydrogenase activity in adrenocortical cells of the fascicular zone increased in male rats.

Effect of the age of pregnant females on brain development in the offspring.

We examined offspring of 9-10 and 3.5-4 month-old female rats. Female offspring (14, 21, 28, 35, and 40 days) of old rats had higher body weight than offspring of young animals. No intergroup differences were revealed in the body weight of male offspring. At the age of 40 days the offspring of old females differed from the offspring of young rats by higher absolute weight of the brain (females), lower size of ganglionic neurons in the parietal lobe (males and females), and lower blood testosterone concentration (males). Thirty-day-old offspring of old rats exhibited higher locomotor activity and lower degree of anxiety compared to the offspring of young animals.

Morphology of the cerebellum in the progeny of female rats exposed to long-term emotional stress before pregnancy.

The structure of the cerebellum was studied in 40-day-old progeny of female rats exposed to 3-week emotional stress and mated with intact males after 10 days and in controls (progeny of intact females). The cerebellum in the experimental group was smaller, the nucleus and cytoplasm of Purkinje cells were smaller, the concentration of RNA in their cytoplasm and increased, the percentage of dark Purkinje cells increased, and the concentration of lipids in the molecular cortical layer and white matter decreased.