Effect of sympathectomy on the heart pump function in rats during postnatal ontogenesis

The influence of guanetidine sympathectomy (30 mg/kg) on the heart pump function in rats during 3 weeks in postnatal ontogenesis has been investigated. Sympathectomy restrains age-dependent establishment of stroke volume, cardiac output and heart rate. The adaptation effects of regular physical training do not develop in the animals with sympathectomy, i.e. heart rate does not decrease and stroke volume does not increase. The initial stage of adaptation of the sympathectomized animals to physical training is accompanied by decrease in stroke volume and remarkable increase in heart rate which indicates the reduction of contractile activity in the myocardium.     

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.     

The action of proinflammatory cytokines on formation of behavior during early postnatal ontogenesis

The study is devoted to the role of proinflammatory cytokine-interleukin-1beta during early postnatal ontogenesis in formation of behavioral programs. Cytokine was injected in pyrogenic and subpyrogenic doses during 1 week (1, 2 or 3 weeks of life). The behavior was tested in the young (40-45 days) and adult (3 months) rats in the "open field" and "elevated plus maze". The greatest behavior disordes (elevation of act's number and of motor activity, the decrease of investigation activity) are revealed in the young animals treated with IL-Ib during 1 and 3 weeks of life. These behavioral changes were marked in rats injected with pyrogenic and subpyrogenic doses of cytokine. They had a similar tendency in male and female rats. At the age of 3 months, behavior changes revealed in juvenile rats were insignificant.     

Compensatory hypertrophy of golden hamster ovaries during early postnatal ontogenesis]

The right-side ovariectomy in the golden hamster females during the prepubertate period resulted in the compensatory hypertrophy of the rest paired organ. The morphological rearrangement of the hypertrophied ovary represented the shift in the quantitative distribution of follicles by the maturation stages towards the predominance of mature forms. The accelerated growth and differentiation along the path of normal postnatal ontogenesis led to the earlier ovulations in the hypertrophied ovary.     

Action of novocain on cardiac and somatomotor autorhythmical functions in early postnatal ontogenesis in rats

In conscious rat pups aged 2–3, 10–11, and 22–23 postnatal days, it has been shown that intraperitoneal administration of 0.5% Novocain at a dose of 25 mg/kg body mass leads to phasic changes of the level of spontaneous periodic motor activity—from increased at once after the administration to depression and subsequent restoration. They are accompanied by the cardiac rhythm fluctuations that change with age their direction on the background of an increased motor activity from brady to tachycardia. All the changes are the most pronounced in newborns. At comparison of the results with the afferent impulsation level fluctuations recorded under the same conditions in the peripheral vagus segment, it is suggested that the revealed reactions are associated with changes of the interoceptive afferentation flow. The conclusion is made that at early stages of ontogenesis, interoception plays an important role in regulation of autorhythmical functions and that this role decreases with age.     

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.     

Effect of long-term hypoxia upon the activity of some enzymes in the brain of rats during early postnatal ontogenesis and in adulthood.

Enzymatic activities were determined in the prosencephalon of rats which had been exposed repeatedly for 8 hrs, either from the age of 1 to 17 days or in adulthood, to an altitude of 7,000 m in a barometric chamber (up to a total of 104 hrs). The activity of enzymes was assayed 20 hrs after the last exposure. The results were compared with values obtained 20 hrs after a single 8-hour exposure to a stimulated altitude of 7,000 m in 17-day-old and adult rats. In young rats a single exposure to hypoxia, the most elevated was the activity of LDH and isoCDH, while GPT and CPK were decreased. After repeated hypoxia, the most significant increasw was noted in the activity of PK and again a decrease in GPT and CPK. In adulthood, a single exposure to hypoxia causes the greatest increase in CPK, while LDH and GOT are reduced. Following repeated hypoxia, none of the enzyme activities were increased by more than 20%, while LDH, GOT, GIDH and CPK were again lower. It is concluded from these results that a single exposure to hypoxia increases anaerobic glycolysis in the immature nervous tissue and improves its oxygen utilization. The relationship between glycid and amino acid metabolism are not appreciably altered. On the other hand, a general reduction of bioenergetics and biosynthesis occurs in adulthood. Repeated hypoxia, on the contrary, has similar after-effects in both age groups, namely inhibition of aerobic metabolism and of the relations between glycid and amino acid metabolism.     

Effect of vasopressin on water permeability of epithelial cells in the kidney collecting duct during postnatal ontogenesis in rats

Desmopressin caused a statistically significant increase in the water permeability of the outer medullary collecting ducts (OMCD) in 22-days old rats. Concentration of specific V2 receptors increased during postnatal period. Comparison of the V2 receptors concentration, mRNA contents, and changes of water permeability in response to desmopressin suggests that parts of transduction mechanism is situated deeper than the receptors, determines the physiological mechanism at the end of weaning period.     

The glomerular apparatus and renal blood flow in rats during postnatal ontogenesis

In anesthetized Wistar rats of the age of 4, 12, 30 and 65 days, the renal blood flow (RBF) with laser-Doppler flowmetry, diameter, number and density of glomeruli, diameter of afferent and efferent arterioles were measured. We found that during rat development the RBF increased 2.8-fold, the diameter of glomeruli--3.6-fold, diameter of afferent arterioles--1.8-fold, and the efferent arterioles--rose 1.3-fold. The number of glomeruli increased 1.3-fold, but their density decreased 16-fold.     

Peptidergic mechanisms of hypothermia-induced seizures in rats during early ontogenesis

Arginine-vasopressin reduced the tonic-clonic seizures' latency as well as the duration of the seizures brain-stem generalisation on the 3rd and 5th postpartum days in rats. The reduced latency was also observed after the PACAP38 low doses administration, whereas higher doses diminished and then enhanced the threshold of generalised hyperthermia-induced seizures on the 3rd and 5th days and the 7th and 9th days, resp. The arginine-vasopressin-treated animals had a dramatically enhanced duration of the tonic-clonic seizures up to the epileptic status on the 9th postpartum day. The findings suggest the PACAP involvement in mechanisms of experimental febrile seizures through its effect upon arginine-vasopressin neurosecretion.     

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.