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Based on the authors' own data and a review of current literature, the role of vasopressin (VP) in the mechanisms of age-related changes, development of stress-reactions and pathology onset is discussed. In aging, the VP concentration in blood and cerebrospinal fluid increased, its level in pituitary rose and that in hypothalamus fell. Under stress (emotional-painful stress, water deprivation) the potential capabilities of the VP-ergic system decreased with age. The role of weakening central monoaminergic influences with aging in changing the intensity of VP secretion is discussed. The results of an ultrastructural analysis and karyometry of the neurosecretory cells testify to an adequate preservation of their protein-synthesizing system and a high level of secretory activity in old age.

An internally contradictory character of individual development may suggest a new periodization of the latter. Etagenesis is an age-associated development of an organism from the zygote to death. Ontogenesis is the period of realization of the genetic program of the organism's development under effects of exogenic factors, the period of growth and shaping of its main structure and functions, and the period of formation of its reproductive function. Mesogenesis is the period of the relatively stable state which is characterized by changing the balance between the processes of aging and antiaging, i.e. the vitauct. Gerontogenesis is the period during which destructive processes of aging prevail over antiaging processes. No strict borderlines between the above periods exist.

In this work we used aorta coarctation as a model of myocardial hypertrophy. We studied the role of intracellular regulators of plasma membrane status-invertors-in the mechanisms of changes of membrane enzyme activities in the emergency stage of myocardial hypertrophy. We used Wistar rats of various ages: adult (6-8 months) and old (26-28 months) rats. It was shown that 4-6 days after aorta coarctation, in adult rats the activities of both Na,K-ATPase and Ca-ATPase of the sarcolemma of cardiomyocytes increased, but in old rats only the Ca-ATPase activity. Experiments with cell hybrids (cytosol of experimental rats and isolated sarcolemma of cardiomyocytes of intact rats) revealed that cytosol of cardiomyocytes of adult animals after aorta coarctation activated Na, K-ATPase and Ca-ATPase. Cytosol of old intact animals after aorta coarctation did not activate Na,K-ATPase, but activated Ca-ATPase. It was supposed that 4-6 days after aorta coarctation, intracellular regulators (invertors) activating Na,K-ATPase and Ca-ATPase of rat sarcolemma were synthesized in cytosol of adult animals. Invertors activating Na,K-ATPase did not appear after the aorta coarctation in old animals, but factors activating Ca2+-ATPase appeared. Cytosol of adult experimental rats activated Na,K-ATPase of sarcolemmas of cardiomyocytes of intact old animals. The data proved the ability of Na,K-ATPase of sarcolemma of old animals to respond to regulating factors. Based on the divergence between the results of experiments with the Na,K-ATPase and Ca-ATPase activities in old rats, it can be supposed that we were dealing with two different invertors.

Effect of the enzyme imprinting by phenobarbital upon alterations of hepatic microsomal monooxygenase activities and lifespan of Wistar rats has been studied. Phenobarbital-sodium (3.5 mg/100 g body weight per day, i.p.) was injected during 1-3 days after birth. This resulted in the enzyme imprinting of the liver microsomal monooxygenases, however, this effect being observed in female but not male rats. In the phenobarbital treated female rats of different age the duration of sleeping time was significantly lower than that in control animals, whereas it did not differ substantially in male rats. The cytochrome P-450 content increased by 34.5% in phenobarbital treated female rats in the age of 12 months in comparison with control animals. A mean lifespan of experimental female rats increased by 17.5% compared to the level of control animals and did not change in male rats. The analysis of survival of animals in Gompertz equation coordinates showed that enzyme imprinting by phenobarbital caused changes in the mortality patterns at different stages of ontogenesis in experimental female but not male rats. An inverse correlation was found between the duration of pentobarbital sleeping time and lifespan of female and male rats.

The experiments were performed on adult (6-8 months) and old (22-24 months) Wistar rats. Insulin induced plasma membrane hyperpolarization and hepatocyte Na,K-ATPase activation in adult but not in old sham-operated rats. Partial hepatectomy had no effect on the invertor mechanism of Na,K-ATPase activity regulation in the liver of adult rats, while pronounced changes took place in old animals 4 weeks after partial hepatectomy. Insulin induced hyperpolarization in hepatocyte plasma membrane and activation of Na,K-ATPase both in old and adult hepatectomized rats. Invertors, intracellular regulators of the plasma membrane status, played an important role in the mechanism of this insulin-induced hyperpolarization. Four weeks after partial hepatectomy in old animals, the invertor mechanism of hepatocyte plasma membrane regulation appeared again, as well as membrane Na,K-ATPase capability to react to insulin action.

The labelled steroid hormones [3H]hydrocortisone and [14C]testosterone, being injected into the gray matter of the rat spinal cord L5-L6 segments, were shown to be transported at a high velocity along the ventral (anterograde) and dorsal (retrograde) root fibres. The maximum velocity of axonal transport along the ventral and dorsal roots in adult rats was, on average, 3006 +/- 101 and 3028 +/- 48 mm/day for [3H]hydrocortisone and 4594 +/- 186 and 5185 +/- 485 mm/day for [14C]testosterone, respectively. In old rats, axonal transport of steroid hormones was markedly slower. Its maximum velocity along the ventral and dorsal roots averaged to 756 +/- 64 and 738 +/- 48 mm/day for [3H]hydrocortisone and 624 +/- 54 and 608 +/- 80 mm/day for [14C]testosterone, respectively. In old rats the amount of labelled hydrocortisone incorporated into the ventral root fibres was sharply reduced (by more than an order of the value) as compared to that in adult animals. At the same time, the intensity of the labelled testosterone incorporation into the ventral root fibres did not demonstrate any significant age-related difference. The injection of low doses of steroid hormones (from less than one microgram to a few micrograms) into the lumbar spinal cord resulted in a significant hyperpolarization several hours later first of the gastrocnemius and then of deltoideus muscle fibres. In old rats, such a hyperpolarization occurred much later. It is suggested that axonal transport of steroid hormones is one of the mechanisms responsible for the effects of hormones on the tissues, which undergoes considerable changes with ageing.

The experiments on the isolated hearts from adult and old rats have shown that during first hours of prolonged perfusion the contractile function decreased to a greater degree in adult rats compared to the old. Following a 3-h perfusion, there occurred a marked fall of the contractile function in old animals. The creatine phosphokinase activity in a perfusate grew sharply in the old rats and changed insignificantly in the adult. The Na,K-ATPase got activated in adult rats, which was prevented by the preliminary injection of actinomycin D, and declined in the old. It appeared that adult hearts had a better endurance of prolonged perfusion and kept sustaining a definite level of performance almost twice as long as the old. Under prolonged perfusion conditions, there has been synthesized a regulatory factor (invertor) in the heart of adult animals, which reduced the myocardial contractile function. The latter was evidenced from a fact that perfusate from adult hearts 'donors' promoted the decrease of contractility of the adult hearts 'recipients'. The preliminary injection of actinomycin D to adult rats prevented a developing decrease of the contractile function but did not induce any changes in the old. This permits to conclude that synthesis of the regulatory peptide factor promotes an economization and adaptation of the adult animal heart.

Transfer of human apoAI gene, within the molecular construction which provides its expression, to the liver of adult and aged rats resulted in the appearance of human protein in their blood, and was accompanied by changes in the content of high-density lipoproteins, as well as by the shifts in their protein and lipid composition. Administration of the human ApoAI gene was followed by changes of the vasoactive effects of HDL. Gene implantation is capable of enhancing the direct vasodilatory effects of HDL in old animals, being weakened by ageing, even against the background of normal age changes in the vascular wall tone.

Experiments on adult and old rats have shown that blood lipoproteins (LP) exert a dilatatory effect on isolated-segments of the thoracic aorta in animals of different age. In old versus adult animals, the sensitivity of vessels in all LP fractions (LDL, VLDL and HDL (low, very low and high density LP)) was lower as a result of age changes in the reactivity of vessels. The capacity of HDL to produce a vasodilatory effect decrease with age, which may be linked to changes in the lipid and apolipoprotein composition. The results revealed a decrease in the level of phospholipids and an increase in the amount of total cholesterol in HDL observed in old age. The capacities of LDL and VLDL to exert a vascular dilatatory action remained unchanged with age.

In rats the rate of axonal transport (AT) or radiolabeled material decreased in the ventral roots of the spinal cord and the vagal and hypoglossal nerves with aging. A maximum AT deceleration in old age was observed in the vagus. The uncoupling of oxidative phosphorylation, inhibition of glycolysis and hypoxia induced a greater AT deceleration in old rats as compared to adults. Small doses of sodium fluoride accelerated AT, and this correlated with a rise in cAMP levels in ventral roots. High doses of sodium fluoride decelerated AT more markedly in old rats. It was shown that anabolic hormones (sex steroids and thyroxine) accelerated AT in both adult and old rats, whereas insulin induced a rise in AT rate in only adults. The catabolic steroid, hydrocortisone decelerated AT. In old rats castration diminished AT, while thyroidectomy had no effect. It was also shown that hydrocortisone and testosterone were transported along axons, reached fibers of the skeletal muscles, and hyperpolarized the plasma membrane. In old age the latent period was extended. Following 73 to 74 days of irradiation, AT slowed down in all the nerves studied in both adult and old rats. Following irradiation hormonal effects on AT changed, for example, the stimulatory effect of estradiol became weak, especially in old rats. Changes in AT could be an important mechanism of disordering the growth of neurons and innervated cells in old age.

Effect of insulin on Na, K-ATPase activity and phospholipid (PL) composition of myocardiocytes' plasma membrane (PM) was investigated in adult (6 months old) and old (28 months old) male Wistar rats. Administration of insulin increases Na, K-ATPase activity and phosphatidilethanolamin content, and decreases phosphatidilinositol content of myocardiocytes' PM in adult animals. Administration of insulin doesn't change Na, K-ATPase activity and decreases phosphatidilethanolamin content of myocardiocytes' PM in old rats. In the experiments with cellular hybrids (cytosol + PM) it was found that cytosol of adult insulin-treated animals caused the activation of Na, K-ATPase in both adult and old rats. Cytosol of old animals did not influence enzyme activity either in old or adult animals. Actinomycin D inhibited a stimulating insulin effect on Na, K-ATPase activity. The obtained data may suggest the presence of insulin-induced synthesis of intracellular factors responsible for resultion of the state of PM invertors.

The aim of this study was to compare the functional and structural changes in similarly identified neurons of the small parietal ganglion in 56 molluscs (Lymnaea stagnalis) of two age groups: adult (10-12 months) and old (20-22 months). No age changes were found in the values of membrane potential, resistance of the neuronal membrane, amplitude, duration, or rate of increase of the anterior action potential front. With aging, the thresholds of direct stimulation were significantly increased, the rate of action potential repolarization decreased, and the amplitude of trace hyperpolarization decreased. The most marked age-dependent changes were observed in the frequency of neuronal spontaneous activity. A clear relationship was established between the frequency of action potentials of the neuron and its structure in adult and old individuals alike. In the molluscs of both age groups, the neurons with a high frequency of action potential displayed ultrastructural features of high activity in the organelles involved in protein biosynthesis. The cytoplasm of these neurons was filled with numerous ribosomes and had a well-developed rough endoplasmic reticulum. The structure of cells with low spontaneous activity in old molluscs differed considerably from that of the corresponding neurons of the adult individuals. The former had significantly marked morphological signs of reduction of the protein-synthesizing processes, as well as of destructive and dystrophic changes. A decrease in the lability of neurons may be an important mechanism of aging.

The experiments on adult (6-8 months) and old (24-26 months) male Wistar rats have shown that treatment of animals with phenobarbital results in a significant increase in hepatic microsomal enzyme content, plasmatic membrane Na+, K(+)-ATPase activities and the elevation of hepatocyte membrane potential value. It is presumed that the changes in plasmatic membrane characteristics during microsomal monooxygenase induction are related to the synthesis of specific intracellular factors (invertors). This assumption was verified by the experiments with 'cellular hybrid' system (cytosol--plasmatic membranes). Using this cross-systems, it was shown that the hepatocyte cytosol of rats treated with phenobarbital produced Na+, K(+)-ATPase activity. The extent of Na+, K(+)-ATPase activation was essentially lower when cytosol derived from old rat hepatocytes was used. The presence of specific factors that activated Na+, K(+)-ATPase in hepatocyte plasmatic membrane was also discovered in blood serum of induced adult and old rats.

It has been shown that a number of hormones (insulin, testosterone, thyroxine, and adrenaline) can stimulate synthesis of plasma membrane regulators-- "invertors" in a cell. The synthesis of "invertors," which is under genomic control, decreases with age. As a result, insulin, testosterone, and thyroxine do not provoke Na,K-ATPase activation and plasma membrane hyperpolarization of hepatocytes and myocardiocytes in old rates. Also, due to desensitization of the heart to adrenaline, a smaller decrease occurs in adenylate cyclase activity in old animals. The Na,K-ATPase of plasma membranes of old animals maintain their ability to respond to the "invertors." The decrease in the synthesis of "invertors" represent an important mechanism of change in the cell's reaction to hormones.

Some indices of aging, metabolism and life span were studied in the male Wistar rats, raised during the suckling period (up to 21 days) in nest of 8-10 pups (control) and 2 pups/dam (experiment). The milk intake of the rat pups was controlled by adjusting litter size at birth. After weaning, the rats of both groups each received the same standard diet ad libitum. Postnatal overfed rats had higher values of body weight, epididymal fat pads and lipid metabolism (total cholesterol, triglycerides, etc.) throughout their whole life. Rats from small nests had increased levels of insulin, thyroxine and decreased proteinase activity of hepatic lysosomes. Overfeeding in the early postnatal period was found to influence the dynamics of mortality and survival rates. It may be concluded that the modification of nutrition in the early period of life may influence an organism's aging process and the dynamics of age-related changes in metabolism and its regulation during an animal's life.

With aging a set of neurohormonal, tissue and cellular changes develop which can be defined as stress-age syndrome. They include irregular changes in the excitability of structures of the limbic system and hypothalamus, rise of the blood concentration of catecholamines, vasopressin, ACTH and cortisol, fall of the concentration of testosterone, thyroxin and other substances, change of the concentration of opioid peptides, immunodepression, dyslipoproteidemia hypercoagulation and free-radical damage of cells. One group of components of the above syndrome is of adaptive importance, while the other is damaging. Symptoms of stress-age syndrome have their individual peculiarities and cannot explain the whole complexity of symptoms of the organism's aging. Against the background of stress-age syndrome the course of developing stress reactions undergoes a change.

Experiments on adult (6-8-month-old and 26-28-month-old) Wistar rats revealed the hyperpolarization of plasmic membranes and activation of Na,K-ATPase of adrenocorticocytes in animals of both age groups and of hepatocytes of adult rats. No effect of testosterone was observed on the level of membrane potential and the activity of Na,K-ATPase of hepatocytes of old rats. The effect of testosterone was prevented by inhibitors of protein biosynthesis (actinomycin D and cycloheximide) and a specific inhibitor of Na,K-ATPase (ouabain), but not by K(+)-channel blocker 2-aminopyridine. Testosterone was assumed to synthesize the specific factor, capable of activating Na,K-ATPase of plasmic membranes. The cytosole of hepatocytes and the blood serum of adult testosterone-treated rats activated the Na,K-ATPase of isolated plasmic membranes of hepatocytes of adult and old intact rats. During aging there was a decrease in the capacity of cells to synthesize the specific factor, which activated Na,K-ATPase of plasmic membranes.

A study was made concerning the role of adrenergic and cholinergic neural regulation in the functional activity of enzymes of microsomal oxidation in the liver. Experiments were performed on adult and old rats using surgical denervation of liver (vagotomy and sympathotomy). The results obtained showed changes that occurred in the monooxygenase activity (aminopyrine demethylase and aniline hydroxylase), as well as in the isoform composition and inductive synthesis of cytochrome P-450. The neural control over liver detoxication function was found to weaken in old age.

Syndromes of aging are classified according to the rate of their development and the sequence of aging of different systems within an organism. Syndromes of aging are characterized by individual and populational specifics. Determination of syndromes of accelerated aging or retarded aging permits the prediction of age pathology development and life span. Comparison of aging peculiarities in animals with different species-specific life spans permits the definition of species-specific changes, chronobiological changes that correlate with chronobiological age, ontobiological changes that correlate with biological age, and parameters that do not change with age. Different correlation of the above parameters forms the basis for species-specific variations in the aging process. Neurohumoral shifts observed in aging are identical to stress effects, and therefore may be referred to as the stress-age syndrome.

Transfer of human ApoA1 gene within the molecular construction which provides its expression, to the liver of the adult and aged rats resulted in the appearance of human protein in their blood, and was accompanied by changes in the content of high-density lipoproteins and of their subclasses HDL(3) and HDL(2), as well as by the shifts in their protein and lipid composition. Synthesis of human ApoA1 was more marked in the organism of adult rats, and gene-regulatory shifts in aged rats.

The experiments on Wistar rats of different age-groups have shown that insulin (1.6 units/kg) provokes hyperpolarization of hepatocyte plasmatic membranes in adult rats, but not in old ones. The hyperpolarization can be prevented by actinomycin D and ouabain, while 2-aminopyridine is ineffective in this case. The appearance of hyperpolarization correlates with the activation of Na,K-ATPase in hepatocyte plasmatic membrane. It is shown that insulin injection provokes the appearance of Na,K-ATPase activation factor in the hepatocyte cytosol. The synthesis of this factor reduces with age.

Aging is accompanied by occurrence of a set of neurohormonal, tissue and cellular changes, which can be defined as stress-age-syndrome. One group of components of the above syndrome is of adaptive importance, while the other--of damaging one. Symptoms of stress-age syndrome have their individual peculiarities and cannot explain the whole complexity of symptoms of the organism aging.

During aging changes occur in the function of potential-dependent Ca channels of plasmic membrane of identified neurons in the mollusc Lymnaea stagnalis, i.e. the value of Ca inward current of neurons in old vs. adult molluscs was much higher at holding potential -50 - -30 mV. When held at -20 mV, the amplitude of Ca current decreased in the neurons of old molluscs, but continued to increase in those of adult molluscs. Various populations of potential-dependent Ca channels are assumed to have irregular age-related changes. The norepinephrine-induced inhibition of Ca current was more significant in old vs. adult molluscan neurons.

Experiments on isolated hearts from adult and old rats have proved an age-dependent decrease in the resistance of contractile function and cardiac rhythm to ischemia and reperfusion. The restriction of coronary flow by 70% produced significant changes in various links of the Ca2+ transport system (an increase in sarcolemmal permeability for Ca2+ and a decrease in Ca(2+)-accumulating capacity of sarcoplasmic reticulum included). These changes, more marked in old animals, seemed to play an important role in the mechanisms of disturbances in cardiac function following coronary insufficiency.

Samples of 7-8 microl of aqueous solution of L-[(14C)]leucine (spec. act. 12543 MBq/mmol) were introduced in the zone of the ventral horn (L(5)-L(6)) of the spinal cord of adult (8-12 month) and old (26-28 month) male Wistar rats. The radioactivity of all 3-mm parts of the corresponding ventral roots was measured. Anabolic hormones (including sex steroids and small doses of thyroxine) increase the rate of axoplasmic transport of substances both in adult and old rats, while insulin accelerates the rate of axoplasmic transport in adult rats and has no effect in old animals. There is a more marked increase in the rate due to administration of estradiol dipropionate in old rats and due to testosterone propionate in adult animals. The catabolic hormone hydrocortisone slows down the flow. In old rats the effect of castration on the axoplasmic flow is weakened, while thyroidectomy induces no change. The data obtained revealed age-related change in hormonal regulation, being linked with hormonal effects upon protein biosynthesis in tissues of the zone of the ventral horns of the spinal cord. With aging, the effects of many hormonal systems on the axonal transport are weakened, which is one of the reasons for its slowdown in old age.

The age changes of neural control over the function of the thyroid, adrenal cortex and testicles were examined in adult (6 months) and old (28 months) male rats. In old age, there was a weakening of adrenergic control of thyroidogenesis, alpha-adrenergic and M-cholinergic control of glucocorticoid function of the adrenal cortex and reduction of adrenergic and M-cholinergic influences in the regulation of steroidogenic function of the testicles.

The paper presents experimental data on extrathyroidal metabolism of thyroid hormones in rats of various ages (1.5--32 months):: T4-131I distribution in an organism, indices of T4 and T3 kinetics, tissue deiodinative capacity, formation of T4 tissue metabolism products and their clearance from cells and organism, T4 binding with tissue proteins. Essential changes in T4 peripheral tissue metabolism have been found with aging: T4 binding by tissues is decreased; T4 distribution space and metabolic clearance are increased; 125I clearance with urine is decreased; T4 half-time in blood remains unchanged; tissue deiodinative capacity is enhanced. Indices of T3 peripheral metabolism in old rats remain unchanged. All these findings result in shifts of the T4/T3 ratio in favour of the latter and in invariability of its content in tissues, alongside with a decrease of functional activity of the thyroid gland with aging.

Age-dependent changes in the polarization of plasma membranes (PM) of various cell types and the mechanisms responsible for its regulation were studied in the experiments on the adult (6-8 and old (28-32 months) Wistar male rats. It was found that the effect of the hormones on the PM polarization level is altered during aging. This being related to shifts in the number and affinity of the hormonal receptors, energetic processes and protein synthesis in the cell.

Plasmic membrane hyperpolarization resulted in a significant activation of the cell genome and a stimulation of the synthesis of total RNA and protein of hepatocytes. Changes in the level of membrane potential are thought to be one of the mechanisms of regulation of cell's genetic apparatus. In old age the stimulating effect of hyperpolarization is weakened that may be a cause of a change in protein biosynthesis.

Experiments with animals with various species-specific life span (rats, rabbits, cats, dogs) and different models (in situ heart, isolated perfused heart, isolated papillary muscle) have proved the reduction of functional capacity of the ageing heart. Diversely directional age-dependent shifts have been established involving myocardial Ca2+ transport system, i.e. an increase in the rate of Na+-Ca2+ exchange and passive Ca2+ transport across sarcolemma and a decrease in its Ca2+-binding capacity and a decrease in Ca2+ accumulation by sarcoplasmic reticulum and mitochondria (Ca2+ uptake). The experiments revealed a decrease in the Ca2+ ATPase myosin activity in the myocardium of aged animals and absence of age changes in the K+ ATPase activity. The findings obtained suggest that the development in the cardiac contractile function disorders in ageing largely depends on the age-related changes in the Ca2+ transport system.

The structural and functional changes of the three identified neurons of the small parietal ganglion were investigated during experiments on the mollusc Lymnaea stagnalis, in two age groups: adult (10-12 months) and old (22-24 months). Old molluscan neurons showed, along with the destructive changes (destruction of mitochondrial cristae, formation of autophagosomes, residual bodies, etc.), the appearance of important adaptive mechanisms (hypertrophy of the mitochondria, hyperplasia of the Golgi apparatus, increased area of nuclear membranes). With aging no changes have been observed in the values of membrane potential, resistance of the neuronal membrane, amplitude and duration of action potential. Considerable changes have been noticed in the values of excitability, frequency of the impulse activity, rate of decrease of the posterior action potential front, and its trace hyperpolarization in the neurons from 22-24-month-old molluscs. The sensitivity of the molluscan neuronal membrane to acetylcholine, norepinephrine and serotonin increased with age.

The studies concerned age-dependent peculiarities of the vasopressin effect on the hemodynamics and tone of the coronary vessels in dogs, the contraction of the isolated vascular strip in rats, and the hemodynamic and ECG indices in rabbits and in rats. The data obtained indicate the great sensitivity of old vessels to vasopressin. In aging, both humans and animals show a rise of vasopressin concentration in the blood. Age-dependent differences of the vasopressin effect on the kallikrein-kinin system, adenosine metabolism, the contents of prostaglandins and cyclic AMP have been established. High sensitivity to vasopressin in combination with its increased concentration in the blood is an important factor that contributes to the development of arterial hypertension and ischemic heart disease.

The effect of repeated courses of enterosorption upon the mean and maximal lifespan and some functional and metabolic indices was determined in 28-month-old Wistar rats. Significant increase of mean and maximal lifespan of old rats was noted at certain regimens of enterosorption. The experimental animals demonstrated less marked age-related structural and ultrastructural changes in the liver, kidneys, myocardium, intestines, pancreas, as compared with control animals. Enterosorption leads to a reduction of pentobarbital-induced sleep, decrease of content of cytochrome P-450, blood cholesterol and triglycerides, cardiac and cerebral tissue cholesterol, total lipids, liver cholesterol and triglycerides. Enterosorption was found to increase the RNA and protein biosynthesis in the liver, kidneys and adrenals of old animals.

It was shown that kallikreinogen content was decreased in blood of old rabbits, kallikrein activity was somewhat increased, kininase activity was significantly decreased. In old animals, adenosine metabolism was activated, this being evident from the rise of 5'-nucleotidase and adenosine deaminase activity in blood and myocardium. Hypothalamic stimulation resulted in significant activation of the kallikrein-kinin system and sharp increase of kallikrein activity, the shifts being less marked in old animals than in adults. In adult animals, vasopressin administration elicited more marked activation of the kallikrein-kinin and adenosine metabolism systems.

Experiments were performed on Wistar male rats, starting from the 28th month of age. The effect of dietary sorbent (non coated nitrogen-containing carbon administered as 10 day courses at 1 month intervals in dosage of 10 ml/kg) on lifespan and a number of biological indices were studied. Enterosorption resulted in the increase of mean and maximal lifespan by 43 and 34% respectively. Analysis of the effect of enterosorption on activity of microsomal enzymes, intensity of total RNA and protein biosynthesis, lipid metabolism, formation of free radicals etc. showed that it produced a positive influence on the functional state of the studied systems and increased the organism's adaptive capacities. Enterosorption was found to delay the rate of onset of age-related structural changes in the organs and tissues.

This article presents questions for discussion and proposes trends for further studies of neurohumoral mechanisms of aging at all stages of the vital activities of the organism.

The experiments on adult (4-6 months) and old (28-30 months) rats revealed changes that develop in old age in various links of the regulatory system of aldosterone secretion: the hypothalamic-hypophyseal control of mineralocorticoid secretion decreased, and the sensitivity of the glomerular zone to ACTH, vasopressin, and K+, as well as that of the myocardium, skeletal muscle and kidney to aldosterone increased. Changes in tissue sensitivity to aldosterone may be due to the increased affinity of mineralocorticoid receptors to aldosterone in old age.

Changes in hemodynamics and myocardial contractile capacity following the stimulation of extracardial nerves and administration of various doses of acetylcholine, norepinephrine, propranolol, phentolamin, atropine, serpasil and benzohexonium were studied in albino rats, rabbits and cats of various age. The shifts in cardiac acetylcholine and norepinephrine content and the activity of some enzymes of their catabolism were determined as well. Functional changes were compared with the structural shifts in intramural nervous system. In old animals there was a rise in threshold of voltage, which induced threshold reaction at stimulation of n. vagus and n. sympaticus and there was a change in heart sensitivity to acetycholine and norepinephrine, propranolol, atropine, serpasil and benzohexonium. A relationship was shown between age changes in nervous regulation of heart and transmitter metabolism. The intensity of acetylcholine and norepinephrine synthesis was decreased in old age, the transmitter metabolism in various parts of the heart was not uniformly altered, the sensitivity of epicardial chemoreceptors to nicotine, veratrum, acetylcholine was increased. The reflexes from cardiac mechanoreceptors were diminished.

Experiments on rats and rabbits using models of arrhythmias induced by vasopressin, epinephrine, strophanthin, and CaCl2 showed that antioxidants derived from 1,4-dihydropyridines, dibunol, and alpha-tocopherol possessed antiarrhythmic effects. Administration of these antioxidants decreased the occurrence of extrasystoles, disturbances of atrioventricular conductivity and ventricular fibrillation. These drugs also prevented changes in membrane phospholipid composition, inhibited activation of peroxidation, decreased phospholipase activity, prevented a decrease of Ca2+ ATPase and Ca2+ binding and uptake by sarcoplasmic reticulum, and increased sarcolemmal Na+, K+-ATPase, sarcoplasmic reticulum creatine phosphokinase.

Studies were undertaken on the effect of intravenously administered ribonuclease agent on the development of experimental osteoporosis produced by cutting of N. femoralis and N. obturatorius in rabbits of different ages. It was found that after chronic (4 months) intravenous ribonuclease administration the osteoporosis of femoral bone stopped to develop in the operated rabbits. The effect of ribonuclease on the RNA synthesized in the conditions of denervation and resulting in activation of the pathological process may be suggested.

Seven to eight microliters of aqueous solution of L-[14C]Leucine (spec. act. 339 mCi/mmol) were introduced in the zone of ventral horn (L5-L6) of the spinal cord of adult (8-12 months) and old (26-28 months) rats. The radioactivity of various parts of the corresponding ventral roots was measured 1-2.5 h thereafter. Labelled substances (including protein) were found to migrate with fast flow in adult rats at the rate of 408 +/- 10.9 and 380 +/- 22 mm/24 h, respectively, as compared with 217 +/- 11.3 and 200 +/- 40 mm/24 h in old rats. The axoplasmic flow slows down in old rats with the increase of distance from the neuronal body. Uncoupling of oxidation and phosphorylation by the administration of 2,4-dinitrophenol, inhibition of glycolysis with NaF, hypoxemia produce more marked deceleration of axoplasmic flow in old rats, while small doses of NaF accelerate the flow, which correlates with the rise of cAMP in ventral roots. Sex steroids accelerate significantly the rate of axoplasmic flow. There is a marked increase in the rate due to the administration of estradiol dipropionate in old rats and due to testosterone propionate in adult animals. Changes in resting membrane potential and direct excitability thresholds of some muscles following colchicine blockade of axoplasmic transport are less marked in old rats that evidences for the weakening of neurotrophic control in old age.

With age marked changes in metabolism and function of muscle fibers appear: electroexcitability thresholds rise, critical polarization level and membrane resistance decrease, time of action potential increases and its amplitude decreases, lability is reduced. The level of intracellular sodium increases and that of potassium decreases. Shifts in ionic asymmetry of muscle fibers are connected with changes in their membrane permeability and a modified function of the sodium-potassium pump. Along with the impairment of nervous influences on muscle fibers in old age, their sensitivity to many hormonal factors increases. Loading levels all age differences in the regulation of skeletal muscle vascular tone. The relationships between the activity of the genetic apparatus and electrical properties of the cell are altered.

Age-dependent changes in the polarization of the plasma membranes (PM) of various cell types and the mechanisms responsible for its regulation were studied in the experiments on the adult (6-8 months) and old (28-32 months) Wistar male rats. The relationship was found between the specificity of cellular function and the pattern of changes in resting potential (RP) and action potential (AP). In senility, changes occur in the ratio of different pathways of energy provision of the ionic transport: the contribution made by enzymic reactions to the mechanism of maintenance of the PM polarization level is diminished. Changes in the PM phospholipid composition influences considerably the character of the PM electric reactions in aging. An anti-oxidant, dibunol (butilated hydroxytoluene, BHT) has appeared to restore many reactions of the cellular PM in the old animals.