Cytofluorometric analysis of small intensively fluorescent atrial cells at various stages of postnatal ontogenesis

The number and fluorescence intensity of small intensely fluorescent (SIF) cells in the nerve ganglia of the rat atria were determined after the treatment, using modified Falk's method. The animals were 1, 7, 14, 28 days and 30 months of age. Similar changes were found in the amount of SIF cells and fluorophore content in all the atrial regions. A marked increase in the number of SIF cells and maximum values were determined between the second and fourth week after birth. The first two weeks of age corresponded to the decrease and the forth week to the increase in SIF cells fluorescent intensity. The data of the investigation made it possible to suggest the connection between principal stages of SIF cell pool formation and processes of autonomic ganglia innervation development.     

Role of non-coronarogenic injuries of the myocardium in sudden death at various stages of postnatal ontogenesis

The study was performed on white inbred young (1 and 3 weeks old), sexually immature (1.5 months old), sexually mature (6 months old) and old (over 24 months old) male rats, who were subcutaneously administered noradrenaline at a dose of 2 mg/kg body weight. The degree of myocardial injury was assessed on frontal histotopographic heart sections stained by the method of Leigh and Regaud, obtained from dead and killed rats 6 hours after noradrenaline injection. The reaction of the adrenal cortical substance was investigated, using quantitative histofluorescent method. It has been shown that young rats have low sensitivity to catecholamine stress, with the sensitivity increasing by the period of sexual maturation and again decreasing in old animals. The animals' death is associated with higher degree of myocardial injury that accompanies a drastic increase in catecholamine secretion by the adrenals.     

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.     

Self-similarity in variability of human heart variability at various stages of ontogenesis

We consider the potential of applying wavelet analysis to fluctuations found in physiological systems. We focus on cardiac interbeat interval time series (RR-intervals) from a group of young adults and children and fetus heart beat rate time series (antepartum cardiotocography), because the wavelet analysis of these heart rate dynamics may provide important practical diagnostic and prognostic information not obtainable with current approaches. We show that all the signals analyzed are self-similar and propose a method for estimating this scaling feature.     

Cortico-subcortical interrelationships in the visual analyzer system at various stages of ontogenesis]

The influence of a corticofugal volley produced by single electrical stimulation of the visual projection cortical zone on the neuronal activity of LGB was studied in non-anaesthetized rabbits aged from three to thirty-five days. A coincidence was found between the time of appearance of nonspecific inhibitory corticofugal influences on the spontaneous activity of LGB neurons and the emergence of the first phasic-specific responses of the neurones of this level to a visual stimulus. It has been shown that the sensory flow at the LGB level can be controlled by non-specific inhibitory corticofugal influences at early periods of postnatal development. The appearance from the 15th day of life of specific responses to a corticofugal volley, including activation phases, leads to a greater complexity of the regulating Cortical influences on conduction of the afferent signal at the thalamic level. The data obtained are considered from the standpoint of integration of various levels of the visual analyser at different stages of ontogenesis.     

Correlations of convulsive and hypoxic resistance in rats at different stages of ontogenesis

Hypoxic and convulsive resistances were studied in 3, 7, 14, 21, 40-day-old rats and in adults. Susceptibility to hypoxia was determined in pressure chamber by "lifting" the animals to the altitude of 12,000 metres. Convulsions were caused by intraabdominal injections of corazol. A correlation between hypoxic and convulsive resistances was found from 3 day after the birth. Their indexes were maximum at this period. Similar decrease of hypoxic and convulsive resistances was observed with the growth of the animals. Moreover the reduction in hypoxic resistance was more dramatic and reached its minimum on the 40th day. In grown up animals, resistance to hypoxia was higher, than in 40-day-old rats. Minimum latency period for development of status epilepticus was detected in 21-day-old rats.     

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.     

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.     

Effect of pentagastrin on choline acetyltransferase and acetylcholinesterase activities in various tissues of the digestive tract of rats

The activity of choline acetyltransferase and acetyl-cholinesterase in different tissues of the digestive tract was measured after a single injection of pentagastrin. Thirty minutes after pentagastrin injection choline acetyltransferase activity in the stomach and ileum was 25 and 32% increased, respectively. The enzyme activity in the stomach returned to the control level 60 min after the hormone treatment, while in the duodenum, ileum and colon it was found to be 26, 35 and 23% higher, respectively, compared to the corresponding saline control. Acetylcholinesterase activity was measured only in the stomach and ileum at 7, 30 and 60 min after pentagastrin injection. Only 7 min after pentagastrin administration acetylcholin-esterase activity in the stomach and ileum showed 12 and 23% enhancements, respectively. The increment in the stomach was not statistically significant.     

Effect of serotonin deficit at different stages of prenatal ontogenesis on behavior of adult male and female rats

Effects of maternal parachlorophenilalanine (PCPA) administration on the offspring behavior were studied in the open field, Porsolt forced swimming, and Morris water maze tests. PCPA was administered in two different gestational periods: on gestational days (GD) 8-11 or GD 14-17, at doses 200/100/100/50 mg/kg. It was found that prenatal exposure to PCPA results in fetal serotonin (5-HT) depletion and changes in both open field activity and depression-related behavior, as well as impairments in spatial learning in the adult offspring. The most pronounced effects on behavior were observed in the male and female offspring whose mothers were depleted of serotonin by PCPA during the third trimester of pregnancy. These results provide further evidence that adverse factors have the most severe effects on the development of rat brain function when exposed during the final trimester of pregnancy than during the second trimester.