[Electrophysiological analysis of functional state of spinal cord motoneurons in rats with parathyroprivous tetany].

In normal rats and of those with parathyroprivous (hypocalcemic) tetany the comparative analysis of background activity (BA), tetanic and posttetanic increase and decrease of frequency of spinal cord (SC) motoneurons (MNs) responses under high-frequency (50, 100Hz) stimulation (HFS) of flexor (G) and extensor (P) hind-limb nerves have been conducted. The on-line selection and program analysis of the spikes was produced. On the 3-7 and 21-22 days of development of acute and chronic tetany, respectively, the significant tetanic and posttetanic changes of MNs activity without meaningful changes in BA was registered. Along with the abrupt increase of excitatory manifestation of activity to HFS in a period of development of acute tetany was observed their relative weakening in animals with chronic tetany. Simultaneously the weakening or total disappearance of depressor reaction, especially expressed in the period of development of acute tetany was noted. It was concluded on the causal dependence of the parathyroprivous convulsions due to disturbances of correlation of inhibitory-excitatory processes in SC MNs.

[Inclusion of the calcium-regulating hormones, cortisol, and blood electrolytes into early adaptive responses of the body]. / O vkliuchenii kal'tsiireguliruiushchkh gormonov, kortizola i élektrolitov krovi v rannie prisposobitel'nye reaktsii organizma.

Comparative study of calcium-regulating hormones, cortisol and electrolytes content in blood as well as of the cardiac contractions and respiration rate before and in early terms (the 5th min., the 45th min., the 5th hour) of the motor activity maximal limitation (immobilisation) was performed in rats. It as ascertained that the maximal, limitation of motor activity even at the earliest stages are accompanied with activation of the adaptive accessory responses as well as with a significant increase in content of calcium, sodium and potassium in the blood, along with a relatively minor decrease in content of parathyroid hormone, thereocalcitonine and phosphorus. Possible mechanisms of the revealed changes as well as the role of the above endogenic factors in the organism's early adaptive responses, were discussed.

[Parathyroid hormone--an endogenous modulator of vascular functional activity]. / Paratireoidnyi gormon--éndogennyi moduliator funktsional'noi aktivnosti sosuda.

Parathyroidin was found to exert a dose-dependent effect on the systemic arterial pressure irrespective of its hypercalcemic effect. The former effect seems to depend in vitro on the term of the parathyroidin incubation with a tissue under study. Endogenous parathyroid hormone seems to play a specific role in modulation of the vessels functional activity.

[Effects of parathormone on 45Ca2+ accumulation in neurosecretory cells and contents of vasopressin in blood after administration of parathyroidin in parathyroid gland insufficiency]. / Vliianie paratgormona na nakoplenie 45Ca2+ v neirosekretornykh kletkakh i soderzhanie vazopressina v krovi pri vvedenii paratireoidina i nedostatochnosti okoloshchitovidnykh zhelez.

The functional state of hypothalamic-hypophyseal-neurosecretory complex was studied in parathyroidin injection and hypofunction of the parathyroid glands. In these conditions vasopressin levels in blood of the rats increased. The incubation of the hypothalamus with parathormone and 45Ca2+, as well as the injection of parathyroidin increased 45Ca2+ transfer to the neurosecretory cells and vasopressin release in the blood. Various mechanisms of similar influence of the parathormone and hypofunction of the parathyroid glands on a vasopressin level in blood are discussed.

[Morphofunctional state of the rat supraoptico-neurohypophyseal system in hypoparathyroisis]. / Morfofunktsional'noe sostoianie supraoptiko-neirogipofizarnoi sistemy krys pri gipoparatireoze.

Volumes of nuclei and nucleoli of neurosecretory cells of the hypothalamic supraoptic nucleus were investigated morphometrically, and the amount of neurosecretion in the posterior hypophyseal lobe was determined photometrically in rats at varying time of parathyroprivic hypocalcemia. The data obtained were indicative of increased function of the hypothalamic supraoptic nucleus on the 5th day of parathyroprivic hypocalcemia and a decrease in the amount of neurosecretion in the posterior hypophyseal lobe that can be interpreted as a sign of an increased discharge of neurosecretion into the blood flow. A decrease in function of neurosecretory cells of the supraoptic nucleus in parallel with an increase in the amount of neurosecretion in the posterior hypophyseal lobe on days 15 and 30 of development of parathyroprivic hypocalcemia indicated retention of a discharge of neurosecretion. Return of neurosecretion to normal tended to occur on day 60.

[Effect of parathyroid hormone on 45Ca2+ absorption in various rabbit tissues]. / Vliianie paratireoidnogo gormona na pogloshchenie 45Ca2+ v razlichnykh tkaniiakh krolika.

The 45Ca2+ absorption by the different tissues under PTH influence was studied by the radioisotope method as dependent on the incubation time. In all cases it was found that the tissue faculty of 45Ca2+ accumulation increases especially in the early period of the incubation. This effect results from a more intense activity of the membrane channels.

[The systems analysis of the central hemodynamics in parathyroprival hypocalcemia]. / Sistemnyi analiz tsentral'noi gemodinamiki v usloviiakh paratireoprivnoi gipokal'tsiemii.

In experiments on cats under parathyroid hypocalcemia the reaction of cardiovascular system on adrenalin and physiological solution administration was investigated. It is shown that after removing the parathyroid glands, parathyroid hypocalcemia decreases the parameters of central hemodynamics. In this case, administration of adrenalin causes an extreme pressor effect due to vascular component of common hemodynamic reaction. Parathyroid deficiency decreases the cardial component in response to the action of physiological solution and adrenalin. The role of calcium-regulating hormonal system in the changes of central hemodynamics before and after physiological loads is discussed.

[Morphofunctional characteristics of neurosecretory cells of the supraoptic nucleus of rats with parathyroprival hypocalcemia]. / Morfofunktsional'naia kharakteristika neirosekretornykh kletok supraopticheskogo iadra u krys s paratireoprivnoi gipokal'tsemiei.

Humori-positive neurosecretory cells of the supraoptic nucleus of the hypothalamus have been investigated during various time of parathyroprival hypocalcemia after extirpation of the parathyroid glands. Contents of total and ionized calcium, phosphorus in blood serum have been estimated. Volume of nuclei and nucleoli has been measured. In 5 days functional activity of the supraoptic nucleus increases (lightly stained cells predominate, volume of the nuclei and nucleoli increases). In subsequent 15-30 days its activity decreases (increase in amount of dark-stained cells, nucleolar volume decreases). In 60 days there is a tendency to restoration of neurosecretion.

[Parathyroid hormone stimulation of nerve cell calcium conduction]. / Stimuliatsiia paratireoidnym gormonom kal'tsievoi provodimosti nervnykh kletok.

Parathyroid hormone (PTH) has been studied for its effect on the voltage-sensitive calcium channels in voltage-clamp experiments on intracellularly perfused snail neurons. A two-stage action of the hormone on the calcium current (Ica) was shown. An initial stage was a short-term one and consisted in an increase of ICa by 7-10%. The second stage developed slowly for 60-70 min, ICa increased twice. The exogenous cAMP and cGMP did not produce such an effect as PTH did. It is suggested that the phosphoinositide pathway mediates the PTH effect.

[Excitatory and inhibitory processes in the spinal cord in alcoholic intoxication]. / Vozbuditel'nye i tormoznye protsessy v spinnom mozge pri alkogol'noi intoksikatsii.

The reflex reactions of the cat spinal cord were studied in chronic alcohol intoxication The extension of the monosynaptic response latency with simultaneous decrease of its amplitude and the suppression of posttetanic potentiation as well as the breaking of inhibitory processes in spinal cord were found after i. v. injection of alcohol. The disordered functional stat of the spinal cord's segmental apparatus seems to be due to depolarizing effect of alcohol and may be one of the causes of the motor breakdown in alcohol intoxication.

[Background activity of neurons of the intermediate nucleus of the cerebellum in cats with parathyroid hypocalcemia]. / Fonovaia aktivnost' neironov promezhutochnogo iadra mozzhechka s paratireoprivnoi gipokal'tsemiei.

Firing rate of unstable type dominated in the cerebellar nucleus interpositus, the interspike interval histograms were right-asymmetrical, and the number of high-frequency neurons and bimodal 1-rate histograms were considerably increased in cats with hypoparathyrosis. Besides, the time interval between adjacent spikes was shortened and the probability of occurrence of the next spike was increased. The curves of post-pulse probabilities were monotonously raising thus indicating that the process under study was not haphazard.

[45Ca2+ and 3H-GABA transport in nerve endings separated from the cerebral cortex of rats with hypoparathyroidism]. / Transport 45Ca2+ i 3H-GAMK v nervnykh okonchaniiakh, vydelennykh iz kory golovnogo mozga krys s gipoparatireozom.

Ca2+ blood serum level was reduced by 34.5% in rats with hypoparathyroidism (HPT) on the 7th-12th day after the damage of parathyroid glands. Synaptosomes isolated from the brain cortex of rats during this period accumulated in a normal medium more 45Ca2+ than synaptosomes from healthy animals. In potassium depolarization, control and experimental synaptosomes accumulated more 45Ca2+, however in HPT the increment in 45Ca2+ uptake in high potassium medium was less temperature-dependent. In normal medium 3H-GABA uptake and release by synaptosomes from the brain of rats with HPT slightly differed from those in the control. On the contrary, 3H-GABA release induced by synaptosome depolarization was depressed in HPT. It is suggested that nerve terminal excretory function disturbances contribute to increased excitability of the central nervous system in hypoparathyroidism.

[Effect of parathyroid hormone on the transport of 45Ca2+ and 3H-GABA in nerve endings isolated from the rat cerebral cortex]. / Vliianie paratireoidnogo gormona na transport 45Ca2+ i 3H-GAMK v nervnykh okonchaniiakh, vydelennykh iz kory golovnogo mozga krys.

Parathyroid hormone (PTH) (0.1-10 ng/ml) evokes a dose-dependent increase in 45Ca2+ accumulation in synaptosomes isolated from the rat brain cortex. In the presence of PTH the fast (I sec) potential-dependent 45Ca2+ uptake was less than in the control. PTH had no effect on 3H-GABA uptake by synaptosomes (P2 fraction). Synaptosomes preincubated in the presence of PTH in Ca2+-free medium and transferred into Ca2+-containing normal medium released more 3H-GABA than control synaptosomes. In this case depolarization-evoked 3H-GABA release was diminished.

[Mechanisms of thrombocyte aggregation in experimental hypoparathyroidism]. / Issledovanie mekhanizmov agregatsii trombotsitov pri éksperimental'nom gipoparatireoze.

Inhibitors of thromboxane synthetase (imidazole), cyclooxygenase (indomethacin), phospholipase A2 (Mepacrine) were used in the experiments on rabbits with experimental hypoparathyroidism to study the role of aggregation factors in the changes of ADP- and collagen-induced platelet aggregation. The enhancement of arachidonic acid metabolism and the release of platelet aggregation factor are discussed.

[Status of thrombocytic-vascular homeostasis in rabbits with parathyroid-depleted hypocalcemia]. / Sostoianie trombotsitarno-sosudistogo gomeostaza u krolikov s paratireoprivnoi gipokal'tsiemiei.

The experiments on 40 rabbits have revealed the increase in antiaggregation activity of the aortic wall in specific hypocalcemia induced by parathyroid gland removal. Participation of plasmic and vascular factors in the changes of platelet-vascular homeostasis in this pathological condition is discussed.

[Changes in the ultrastructure of synapses and neurons of the ventral horns of the spinal cord in cats with tetany as a result of the removal of the parathyroid glands]. / Izmeneniia ul'trastruktury sinapsov i dvigatel'nykh neironov ventral'nykh rogov spinnogo mozga u koshek s paratireoprivnoi tetaniei.

An electron microscopic investigation on ultrastructure of synapses and ventral horns of the lumbar thickening in the spinal cord of cats with parathyroprival tetany has been performed. When motor disorders are clearly seen on the 2d - 4th days after removal of the parathyroid glands, together with the changes demonstrating functional activity of the synapses, certain irreversible degenerative changes of the "dark" type are seen in the axodendritic and axosomatic synapses. A complex of structural-metabolic changes has been revealed in the motor neurons, they have both functional-compensatory and degenerative character. It is possible to suggest that the changes revealed at parathyroprival tetany result from a disturbed metabolism and increased afferent influences.

[Ca2+ content of rat liver and brain mitochondria in hypoparathyroidism]. / Soderzhanie Ca2+ v mitokhondriiakh pecheni i golovnogo mozga u krys pri gipoparatireoze.

Rats with experimental hypoparathyrosis showed an increase in the content of Ca2+ in liver and brain mitochondria, discovered by fluorescent testing with chlorotetracycline. That increase correlated with the degree of hypofunction of the parathyroid glands.