Sequential maturation of skeletal muscle groups during postnatal ontogenesis of rats]

Experiments were conducted on rats during the early postnatal period; a study was made of the membrane potential (MP) establishment of the fibers of the skeletal muscles of the neck, the anterior and the posterior limbs. At birth the most mature were the muscles of the neck, and the least -- the muscles of the posterior limb. Establishment of the stationary MP level in the muscles of the neck occurred during the first week after birth, in the muscles of the anterior limbs -- by the 10th-12th day, and of the posterior limbs -- by the 15th-20th day. The order of maturation of various groups of the skeletal muscles was associated with the peculiarities of the neuro-trophic influences at various age periods. Muscles of the neck were characterized at all the developmental stages by a rhythmic low-frequency electromyographic activity. In the muscles of the limbs the rhythmic electromyographic activity was transformed into the discharge high-frequency activity by the period of termination of increase of the MP of the muscles.     

Monoaminergic influences of the caudate nucleus on conditioned food-getting reactions in rats]

Influence of microinjections of monoamines and glutamic acid into the caudate nucleus head on conditioned food-procuring reaction was studied in experiments on rats. Dopamine, noradrenaline and glutamic acid prolong the latency of the reflex, while serotonin reduces it. However, all the drugs tested reduce the number of conditioned food-procuring movements. The effects of dopamine are achieved through neurone receptors of the caudate nucleus which are sensitive to haloperidol and chlorpromazine; effects of serotonin are mediated through the D-serotoninoreactive systems, and those of noradrenaline, through the alpha-adrenoreactive systems of the neostriatum neurones. The inhibitory effect of glutamic acid is not due to the action on the serotonino-, adreno-, or dopamine receptors of caudate units.     

Phenylalanine in the caudate nucleus of dopamine depleted rats

Dopamine depleting lesions of the substantia nigra result in a reduction of the striatal accumulation of 2-phenylethylamine following monoamine oxidase inhibition. It is established that this effect may not be due to a change in availability of aromaticL-amino acid decarboxylase in striatum. Nevertheless, the possibility remains that striatal concentrations of phenylalanine (the precursor of 2-phenylethylamine) may be altered by dopamine-depleting lesions. The present experiments assessed the effects of dopamine depletion induced by 6-OHDA (7 days following 8 g/4 l unilateral substantia nigra injection) on striatal concentrations of phenylalanine, dopamine, 5-hydroxytryptamine and their metabolites. In addition, the effects of reserpine-induced (10 mg kg^–1, 2h, sc) amine depletion on these striatal levels were also assessed. Under equivalent conditions reserpine is reported to increase striatal accumulationof 2-phenylethylamine. 6-OHDA induced a significant unilateral depletion of dopamine, DOPAC and HVA and increased 5-HIAA but had no significant effect on phenylalanine levels. Reserpine decreased dopamine and 5-hydroxytryptamine and increased DOPAC, HVA and 5-HIAA levels, no changes in phenylalanine were observed. This pattern of results was also observed when lesioned animals or reserpine-treated animals were pretreated with (-)-deprenyl (2 mg kg^–1, 2 hr, sc), the treatment previously used to induce accumulation of 2-phenylethylamine. These data indicate that changes in 2-phenylethylamine previously observed under these conditions may not simply be secondary to a change in striatal phenylalanine concentrations.     

Age and changes in the splenic lymphoid tissue of germ-free rats during the postnatal period of ontogenesis]

In germfree rats the splenic lymphopoiesis is not demonstrated by the investigation to be suppressed, and lymphoid follicules undergo age changes. Up to 15 days, periarterial zone of T-lymphocytes, responsible for cell immunity, is determined, and by the 30th day, as in control animals, peripheral zone of B-lymphocytes, responsible for hormonal immunity, is distinctly observed. In 4-month-old germfree animals, a large amount of free iron crystals is detected in the spleen, while in the organ of control animals its amount is still small. In 10-month-old germfree rats, with the appearance of reactive centers, the zone of B-lymphocytes widens in lymphoid follicules and iron crystals integrate in the red pulp. Lymphopoiesis in the spleen of the germfree rats seems to be maintained by certain local conditions which are connected with increased haemolytic function of the organ. This produces a discharge of a large amount of the products of erythrocytosis which, like autoantigens, stimulate lymphopoiesis in the spleen even when microflora is absent in the organism, while lymphopoiesis in lymph nodes in germfree animals is sharply inhibited.     

Dynamics of organ blood flow in rats in postnatal ontogenesis

In the 4-, 13-, 30-, and 65–90-day old anestetized Wistar rats (8–15 rats in each group) the voluminous blood flow rate was measured in liver, kidney, small intestine wall, and in the predominantly white gracilis muscle of femur. A LAKK-01 laser-Doppler flowmeter and its cutaneous (for kidney) and needle (for other organs) probes were used; they provided estimation of blood flow to the tissue depth of about 1 mm. It has been found that the blood flow rates (per organ mass unit) fall in liver, intestine, and even more in muscle, whereas increase in kidney, particularly for the first month of life. Calculations show that in adult rats as compared with the 4-day old pups (with their mass exceeding 22 times) the blood flow to muscle, liver, intestine, and kidney should rise (with taking into account the increase of mass of the organs) 14, 17, 18, and 43 times, respectively.     

Protein binding glucocorticoid hormones (transcortin) during peri-and postnatal ontogenesis and pregnancy in rats]

The constants of association and the energy of interaction between transcortin and cortisol, the binding ability and other characteristics of transcortin have been studied in the embryos, sexually immature and mature young and old females, females on the 14th and 21st days of pregnancy, immature and mature males. The constant of association in all the groups amounted to ca. 10(8) and the energy of interaction ca. 10 Cal/mole. The embryos and immature rats of both sexes are characterized by relatively low levels of the binding ability of transcortin. During the sexual maturation, the level of transcortin increased--insignificantly in males and markedly in females. The level of transcortin in the latter remained almost invariable during pregnancy and senescence. By the electrophoretic and sedimentation properties transcortin was the same in different groups. The high level of transcortin during pregnancy corresponded to the high level of hormones bound by transcortin, the level of these hormones in the embryos being much lower than in the mother.     

Functional activity of leucocytes in postnatal ontogenesis of dogs]

Studies have been made on motile and phagocytic activity, osmotic fragility of neutrophilic leucocytes, as well as on their glycogen content in dogs of various age groups. Within the first 3 months of postnatal life of animals (especially during the 1st month), functional activity of leucocytes is lower than in adult dogs. With respect to functional activity of leucocytes, 6-month puppies stand closer to adult dogs, although exhibit some differences from the latter.     

The effect of cervical sympathetic ganglia extirpation on the growth of rats during postnatal ontogenesis]

Bilateral extirpation of the superior cervical sympathetic ganglia carried out during the first month after the birth of ratlings caused a delay in growth by 40-60%. Section of pre-ganglionic sympathetic fibers and also sham operations failed to lead to any significant changes. Normal growth and skeletal development were disturbed in gangliectomized rats: the zone of growth of the proximal end of the tibia was much narrower in the operated animals than in the intact ones and there was a delay in the spread of secondary ossification centres.     

Dynamics of hematological blood parameters of white rats in postnatal ontogenesis

In experiments on Wistar rats, dynamics of blood hematologic and rheological parameters was studied from birth to the 3-month age. Results of this study indicate an intensive activity of the red bone marrow anlagen for the first 3 weeks of postnatal ontogenesis. This is manifested as an increase of the number of cells in the erythron system, a change of the erythrocyte acidic resistance, and a shift in the leukocytic formula. The boundary between the 2nd and 3rd weeks of ontogenesis is a critical period: there occur a sharp deceleration of erythropoiesis and a change of the age-related erythrocyte composition and of the blood leukocyte ratio towards the parameters characteristic of adult rats. The rise in the number of leukocytes and erythrocytes does not stop after this period. Until the 4-week age, the deformability index increases to be accompanied by an increase of hemoglobin hydration and improvement of the erythrocyte toroid shape. Subsequently, inversion of these processes occurs.     

Cataractogenic and lethal effect of selenite in rats during postnatal ontogenesis.

Male rats aged 5, 10, 15, 20, 30, 40, 50 and 60 days were injected with a single dose of sodium selenite (20 or 40 mumol/kg b.w.). For two months after the injection, all the rats were observed daily for mortality (acute up to 24 h after the injection, subacute 2--7 days after) and the incidence of permanent and intermittent cataract. With the higher dose, both forms of lethal effect were found to shift to earlier phases of ontogenetic development, subacute mortality appearing sooner than acute mortality. The cataractogenic effect produced by the administration of both 20 and 40 mumol/kg b.w. dependent on the age of the experimental animals. It appeared only in the early phases of ontogenetic development (up to the age of 15 days); cataract was not observed during later development.     

Nociceptin differentially affects morphine-induced dopamine release from the nucleus accumbens and nucleus caudate in rats

The effects induced by nociceptin on morphine-induced release of dopamine (DA), 3,4-dihydroxyphenilacetic acid (DOPAC) and homovanillic acid (HVA) in the nucleus accumbens and nucleus caudate were studied in rats by microdialysis with electrochemical detection. Nociceptin administered intracerebroventricularly (i.c.v.) at doses of 2, 5 and 10 nmol/rat changed neither DA nor metabolites release in the shell of the nucleus accumbens or in the nucleus caudate. Morphine administered intraperitoneally (i.p.) (2, 5, and 10 mg/kg) increased DA and metabolites release more in the shell of the nucleus accumbens than in the nucleus caudate. When nociceptin (5 or 10 nmol) was administered 15 min before morphine (5 or 10 mg/kg), it significantly reduced morphine-induced DA and metabolites release in the shell of the nucleus accumbens, whereas only a slight, nonsignificant reduction was observed in the nucleus caudate. Our data indicate that nociceptin may regulate the stimulating action associated with morphine-induced DA release more in the nucleus accumbens than in the nucleus caudate, and are consistent with recent observations that nociceptin reversed ethanol- and morphine-induced conditioned place preference. Therefore, the nociceptin-induced reduction of DA release stimulated by morphine in the nucleus accumbens, and the results obtained with nociceptin in the conditioned place preference procedure suggest a role for nociceptin in the modulation of the behavioral and neurochemical effects of abuse drugs.     

Effect of incomplete starvation on development of compensatory testicular hypertrophy during postnatal ontogenesis of rats]

The incomplete starvation of rats during the first month of life resulted in the inhibition of development of the spermatogenic epithelium cells in 80% of seminiferous tubules, preserved the increased permeability of hematotesticular barrier with respect to rivanol and the ability of rats to react by the increase of testis volume in response to unilateral castration. The data obtained confirm our hypothesis according to which there is a definite correlation between the degree of spermatogenesis completion, the function of hematotesticular barrier and the ability of animals for compensatory hypertrophy of testis.