Influence of thyroidectomy on brain catecholamines during the postnatal period

The influence of early thyroidectomy (Tx) on changes in dopamine (DA) and noradrenaline (NA) during the postnatal period (30, 45 and 60 days old) was studied in the diencephalon and the rest of the brain of male and female rats. Thyroidectomy interfered with the normal growth of the animals, decreased brain weight and markedly influenced the developmental pattern of both DA and NA in the diencephalon. When compared with control values, the DA concentration, in 45- and 60-day-old Tx male rats, was 29 and 43% lower, respectively, and 21 and 43% lower, respectively, in Tx females. Diencephalic NA levels in Tx rats were also lower than those observed in controls, 15% inferior in 45- and 60-day-old males; 27 and 22% lower, respectively, in females. Thyroidectomy does not significantly alter the level of either amine in the rest of the brain.     

Effect of intrauterine exposure to ethanol on synthesis of various phospholipids in the rat brain during the postnatal period

Male rats, whose mothers were given ethanol during pregnancy, were injected inorganic P32 into lateral brain ventricles. Some animals during 1 hour before decapitation were subjected to stress. Phosphatidylethanolamine, phosphatidylcholine and phosphatidylserine were isolated from neocortex and hippocamp. Prenatal alcohol treatment led to 30% inorganic P32 incorporation increase into neocortex phosphatidylcholine. Stress was followed by phosphatidylcholine synthesis level decrease in neocortex by 13% and in hippocamp by 26%. Amplitude of phospholipid synthesis alterations increased after both prenatal alcohol treatment and stress. The results show that prenatal alcohol treatment results in essential disfunction of brain phospholipids synthesis.     

Effect of prenatal hypoxia during organogenesis on albino rat behavior during postnatal period

The survival rate, physical development, and spontaneous behavior has been evaluated in pups of albino rats exposed to acute hypobaric hypoxia on the 9–10th day of gestation corresponding to the onset of organogenesis. Prenatal hypoxia increased the mortality among the offspring, delayed their physical development, and affected their spontaneous behavior up to the age of 2 months. The females exposed to intrauterine hypoxia proved to be more sensitive to hypoxia than males.     

The effect of starvation during an early postnatal period on carbohydrate metabolism in the swine brain

Metabolism of carbohydrates in the brain of 110-day-feti, newborns (before taking the colostrum), 1-day-old and 5-day-old piglets, grown under sows or starved for 24 hours has been studied. Examination of brain slices with the use of 1-14C glucose and 6-14C glucose and determination of the glycolysis-limiting enzymes activity have shown that glycolysis is the main pathway of glucose utilization in the central nervous system of pigs during the transition from prenatal to postnatal development. The major portion of NADPH in the brain of new born piglets is supplied by dehydrogenases of the pentose-phosphate pathway. The increased activities of NADP-dependent malate and citrate dehydrogenases are found in the cytoplasm of astrocytes during the neonatal period. The decreased intensity of glycolysis and pentose-phosphate pathway in the brain of 1-day-old piglets is associated with the increased rate of malate and isocitrate oxidation. Starvation for 24 hours causes changes in the carbohydrate metabolism rates in the brain of piglets. The pentose-phosphate pathway rate increases by 70-80 per cent in the brain structures of piglets of the both groups. Besides, the iso-CDG activity also rises in the brain of 5-day-old animals. The high level of oxidation-reduction processes in the brain of older piglets at active glycolysis is supposed to be one of the peculiarities of energy metabolism in the central nervous system of animals which are resistant to starvation.     

Rat brain catecholamines in the initial period of acute radiation exposure

Total X-ray irradiation (0.21 C/kg of rats induces an hour later an increase in the dopamine and norepinephrine content in the grey matter by 11 and 60%, respectively. The spontaneous release of dopamine and norepinephrine from the brain synaptosomes of the irradiated rats falls causing a decrease of the initial rate of the process. Potassium chloride depolarization of synaptosome membranes of the control rat brain increases both the maximal and initial rate of the process of neuromediators' release; in irradiated animals only the maximal rate of the process grows, the initial rate of the dopamine release being unchanged and that of norepinephrine increasing but less that in the control. After irradiation maximal rate of the by synaptosomes dopamine uptake is 2.6 times as high, while that of norepinephrine is 4.6 times as low; Km of the highly specific uptake of norepinephrine decreases.     

Effect of reserpine administered during infancy on brain catecholamines and adult behaviour in the rat

Reserpine (0.1 mg/kg/day) was administered to rats from 11 through 30 days of age. During and after administration of reserpine, concentrations of catecholamines, epinephrine and norepinephrine, in the brain were estimated. Levels of catecholamines were about 30 per cent of normal during the period of reserpine administration. Approximately 3 weeks were required for these levels to return to normal. When animals were 95-100 days of age, they were deprived of food and were trained to press a bar for food. When the rate of responding became stable, the animals were subjected to three successive extinctions at daily intervals and the increase in response rate after the onset of each extinction was determined. This extinction-induced increase in response rate was greater for previously reserpinized animals than controls during the second and third extinctions, but not the first. These findings are interpreted as a decreased ability of the animals, reserpinized during infancy, to learn to respond discriminatively during non-reinforcement (extinction). Thus, an effect of reserpine administration during infancy on a type of behaviour in the adult has been demonstrated. This occurs after the catecholamine-depleting effect of the reserpine has been fully dissipated.     

Effect of prenatal gamma irradiation during the late fetal period on the postnatal development of the mouse

Pregnant Swiss albino mice were exposed to 0.3, 0.5, 1.0, or 1.5 Gy of gamma radiation on day 17 of gestation. Sham-exposed controls were examined for comparison. Exposed mice as well as controls were left to complete gestation and parturition. Pups were observed up to age 6 weeks; appearance of physiological markers (pinna detachment, eye opening, fur development, vaginal opening, and testes descent), postnatal mortality, body weight, body length, head length, head width, and tail length were recorded. A significant delay in fur development was observed at 0.3 Gy and in other physiological markers at doses above 0.3 Gy, while a significant increase in mortality and growth retardation occurred only at 1.0 and 1.5 Gy. Although congenital anomalies such as syndactyly and bent tail were observed at doses of 0.5-1.5 Gy, only syndactyly showed a statistically significant increase in frequency. A statistically significant lower body weight was observed during the first week of postnatal life, but body weights increased to normal levels by the second week in animals exposed to doses less than 1.0 Gy. At higher doses, low body weight persisted throughout the postnatal period. Head length and tail length showed a significant decrease from controls at 0.5-1.5 Gy, and the effect was evident from birth to age 6 weeks. But a similar effect on body length and head width was noticed only at 1.0 and 1.5 Gy. These studies indicate that even in the absence of any major morphological changes, normal development of physiological landmarks and postnatal growth can be impaired by fetal irradiation at 17 days p.c. (post coitus). Morphological changes appear to have a threshold between 0.3-0.5 Gy, while physiological marker effects may occur with a lower threshold.     

Glutatmine synthetase activity in the chick brain during postnatal growth. Effect of MSO

Glutamine synthetase activity was estimated in the chick cerebral hemispheres, optic lobes and cerebellum between the 1st and the 30th day of postnatal growth. Glutamine synthetase activity is higher in the cerebellum than in the cerebral hemispheres and lowest in the optic lobes at 1 day after hatching; at 30 days after hatching, it is the same in the optic lobes and in the cerebellum and lowest in the cerebral hemispheres. The great increase of glutamine synthetase activity between the 1st and the 4th day after hatching corresponds to the appearance of the heterogeneity of the chick brain glutamate metabolism. The glutamine synthetase activity is inhibited by MSO $\text{in vivo}$ at a concentration of 100 mg kg ^?1 at values of 87, 90 and 89 % in cerebral hemispheres, optic lobes and cerebellum of 1, 2 and 4-day-old chicks. The enzyme inhibition is less pronounced $\text{in vitro}$ and reaches values of about 25 and 75 % for 1 and 10 mM MSO concentrations respectively in the three brain areas of the 1 to 4-day-old chick and values slightly lower in the 30-day-old chick brain.     

Influence of stress of a maternal organism on the turnover of catecholamines in the brain of early postnatal rats

Effects of prenatal stress (daily 1-h-long immobilization of pregnant females at the 15th–21st days of pregnancy) on the formation of sex-related dimorphism of the turnover of noradrenaline (NA) and dopamine (DA) in the preoptic area (POA) of the brain and mediobasal hypothalamus (MBH) were studied in 10-day-old rats. Sex-related differences of the turnover of a functional NA pool in the POA and DA pool in the MBH were demonstrated in intact control rats: a higher rate of the monoamine turnover was observed in males. Prenatal stress abolished these sex-related differences and, at the same time, induced such differences in the DA turnover in the POA. It is supposed that prenatal stress-evoked early modifications of sex-related dimorphism of the catecholamine turnover in the brain can result in the development of remote disturbances in the neuroendocrine control of reproduction and adaptation.     

Hypoxia-induced lipid peroxidation in the brain during postnatal ontogenesis

Reactive oxygen species (ROS) are common products of the physiological metabolic reactions, which are associated with cell signaling and with the pathogenesis of various nervous disorders. The brain tissue has the high rate of oxidative metabolic activity, high concentration of polyunsaturated fatty acids in membrane lipids, presence of iron ions and low capacity of antioxidant enzymes, which makes the brain very susceptible to ROS action and lipid peroxidation formation. Membranes of brain cortex show a higher production of thiobarbituric acid-reactive substances (TBARS) in prooxidant system (ADP.Fe(3+)/NADPH) than membranes from the heart or kidney. Lipid peroxidation influences numerous cellular functions through membrane-bound receptors or enzymes. The rate of brain cortex Na(+),K(+)-ATPase inhibition correlates well with the increase of TBARS or conjugated dienes and with changes of membrane fluidity. The experimental model of short-term hypoxia (simulating an altitude of 9000 m for 30 min) shows remarkable increase in TBARS in four different parts of the rat brain (cortex, subcortical structures, cerebellum and medulla oblongata) during the postnatal development of Wistar rat of both sexes. Young rats and males are more sensitive to oxygen changes than adult rats and females, respectively. Under normoxia or hypobaric hypoxia both ontogenetic aspects and sex differences play a major role in establishing the activity of erythrocyte catalase, which is an important part of the antioxidant defense of the organism. Rats pretreated with L-carnitine (and its derivatives) have lower TBARS levels after the exposure to hypobaric hypoxia. The protective effect of L-carnitine is comparable with the effect of tocopherol, well-known reactive species scavenger. Moreover, the plasma lactate increases after a short-term hypobaric hypoxia and decreases in L-carnitine pretreated rats. Acute hypobaric hypoxia and/or L-carnitine-pretreatment modify serum but not brain lactate dehydrogenase activity. The obtained data seem to be important because the variations in oxygen tension represent specific signals of regulating the activity of many specific systems in the organism.     

The brain catecholamines during domestication of the silver fox Vulpes fulvus

Studies have been made on the content of catecholamines (noradrenaline and dopamine) as well as metabolites of dopamine (3,4-dihydroxyphenylacetic and homovanillic acids) in the brain structures of silver foxes which differ in their handling reactions. The level of noradrenaline was found to be significantly higher in the anterior hypothalamus of domesticated animals; no differences in noradrenaline content were found in the frontal cortex, hippocamp, posterior hypothalamus and midbrain in animals from aggressive and domesticated groups. Dopamine content was higher in the tuberculum olfactorium of domesticated animals, being lower in the striatum and n. accumbens. Metabolite level remained unaffected which is presumably due to changes in dopamine synthesis in the investigated structures. It was concluded that domestication of animals favours the specimens with an altered state of catecholaminergic system of the brain.     

Polysomes during early postnatal development of brain in the rat

We have attempted to show eventual modifications in the brain protein synthesis apparatus of rat during the first three weeks after birth. Through this time we noted a steady decrease (about 60%) in the free polysomes, when expressed relative to tissue weight. This decrease does not correlate with changes in the polysome profile, indicating that no loss in the efficiency of protein synthesis was involved. Translation in a reticulocyte lysate also failed to reveal differences.     

Cellular proliferation in the anterior pituitary of the rat during the postnatal period

Summary Cellular proliferation in the anterior pituitary of 2-, 8-, 15- and 30-day-old rats was examined by injection of bromodeoxyuridine 1 h before autopsy. Bromodeoxyuridine incorporated into DNA was detected immunohistochemically by use of a monoclonal antibody. The highest rate of cell proliferation was found in 2-day-old animals; it decreased thereafter during the postnatal period. Possible toxic effects of colchicine on cellular proliferation were examined. Colchicine treatment (10 mg/kg in 8- and 30-day-old animals) significantly decreased the number of bromodeoxyuridine-labelled cells/mm² in 8-day-old rats. Some sections were doubly immunostained for bromodeoxyuridine and various pituitary hormones. The proportion of doubly-immunostained cells to all proliferating cells was generally low, ranging from 23% at 2 days to 32% at 30 days of age.On leave from the Department of Human Anatomy and Histology, Faculty of Medicine, University of Salamanca, Salamanca, Spain