Phase-shift gradients of dominant cortical potentials in rabbits

Phase shifts of cortical potentials were studied in rabbits before and during photic stimulation and their importance for irradiation of excitation from the visual to the motor area was examined. Both before and during stimulation variations in phase relationships of various kinds were observed. In most cases, however, with an increase in distance between the electrodes, the phase shift of the theta-waves gradually increased. Most motor responses of the rabbits took place in the presence of a marked phase shift gradient. It is suggested that the state of the brain in which a spatial phase shift gradient of the theta-waves is recorded in the EEG is the optimal condition for realization of the motor response. Photic stimulation increases the number of in-phase waves in the EEG recorded from closely situated points and it reduces scatter of the phase shift values between components of the sensomotor and visual cortical EEG, i.e., it leads to an increase in coherence. Motor responses of the rabbits to stimulation take place in the presence of theta-waves with the most constant phase shift in the EEG of the sensomotor and visual cortex.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 16, No. 4, pp. 512–519, July–August, 1984.     

Genesis and functional role of cortical evoked potentials

Experiments on cats with recording electrodes implanted into the cranial bone showed that the evoked potential (EP) in the auditory cortex of the intact waking cat in response to clicks consists of five components with a total duration of up to 300 msec. Neurons of two types participate in the response to clicks: those with and without background activity. The former respond to clicks by various changes in background activity, the latter by one or several action potentials. The latent period of this response varies in different neurons from 6 to 250 msec. In response to clicks, several groups of neurons participate successively in the response, accounting for its long duration. From the beginning of the response, neurons of all cortical layers take part in it. At any moment of EP development, some neurons are in a state of excitation, others in a state of inhibition. About 80% of neurons responding to clicks respond before or during the initial electropositivity, 12% during the initial electronegativity, and only 8% during the late components of the EP. The importance of these findings is discussed relative to the question of the nature of the EP and of processes taking place in the brain after the arrival of an afferent volley.A. A Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neiofiziologiya, Vol. 2, No. 4, pp. 349–359, July–August, 1970.     

The functional significance of synchronization of cortical potentials in humans

The dependence between the level and the topography of spatial synchronization of cortical potentials and the manifestation of motor reactions to light stimuli was studied in humans. To evaluate the spatial synchronization of potentials the correlation coefficients () were calculated between three points of the motor area and each of three occipital points of the cortex. The calculation was made using a computer with direct input of the potentials. At a definite level of the machine switched on a light stimulus and a mechanism recording the motor reaction. The experiments have shown that the higher the number of pair derivations giving a high value of , the more often movements are caused. Moreover it became apparent that the pattern of correlation ratios between the derivations depends on the motor reactions. In the case of movements a significant constancy of the ratios between individual derivations was found. It is shown that the spatial synchronization of potentials in the human cerebral cortex has a functional significance. However, this synchronization does not reflect the realization of movements but only the conditions required for them.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 2, No. 2, pp. 166–172, March–April, 1970.     

Excitability of the sensomotor cortex and red nucleus of rabbits at different levels of spatial synchronization of cortical potentials

To determine the excitability of the rabbit sensomotor cortex and red nucleus the animal's motor response to electrical stimulation of these structures at threshold strength was investigated. In computerized experiments the excitability of these structures was compared in situations characterized by different degrees of correlation of cortical potentials. An increase in the level of spatial synchronization of cortical potentials was shown to be accompanied by an increase in the excitability of the sensomotor cortex and red nucleus. This increase in excitability is evidently a neurophysiological mechanism of the increase in probability of appearance of an effector response to sensory stimulation when the level of spatial synchronization of cortical potentials is raised.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 9, No. 1, pp. 19–24, January–February, 1977.     

Ultrastructural characteristics of osteoclasts in different functional states

By electron microscopy and autoradiography, a study was made of osteoclasts in the metaphyseal zones of the femora of 1-7-day old rabbits and rats. It was established that depending on the intensity of resorptive processes osteoclasts noticeably differed in their morphology (shape, size, number of nuclei, degree of development of intracellular organelles, "brush border"), as well as in the level of biosynthetic activity registered by incorporation intensity of 3H-uridine and 3H-methionine in these. According to these indices, osteoclasts were classified as young, mature functionally active, and non-active osteoclasts, as well as perishing ones. The defined morpho-functional states represent successive stages of the life cycle of osteoclasts.     

Electroorientation effect of isolated mitochondria in different functional states

For the first time, the electroorientation effect of isolated rat liver mitochondria has been investigated in a nonuniform alternating electric field at frequencies from 50 to 10(7) Hz. Two relaxation regions of mitochondria electroorientation have been revealed; they are due to the presence of low-frequency alpha - and high-frequency beta-dispersion. It has been shown that incubation of mitochondria in a medium with a low electroconductivity as well as in the presence of ionophores (valinomycin, 2,4-dinitrophenol) results in a decreased electroorientation value in the region of the high-frequency structural polarization. This is explained by a marked lowering of the effective electroconductivity of mitochondria due to changes in the permeability of the inner membrane of organelles. Upon the addition of ionophores, the decrease in the electroorientation effect value becomes more pronounced. Inhibition of respiration of mitochondria by antimycin A resulted in a slight diminution of the effect, followed by time-dependent stabilization, probably due to a lowered electroconductivity of the mitochondrial matrix, induced by the reduction of pH in the intramitochondrial space, change in the ionization of inner enzyme structures, and a partial limitation of the inner ion mobility.     

Electrochemical potentials of potassium in skeletal muscle under different metabolic states.

Intracellular potassium and membrane potential were measured simultaneously by means of double-barrelled liquid ion-exchange microelectrodes in single fibers of rat thigh muscle in vivo in rats maintained in seven different metabolic states. The K+ equilibrium potential (EK) was more negative than the simultaneously measured membrane potential (Em) in the normal state by 18.4 mV. K+ loading, acute and chronic, resulted in depolarization of Em due to increased serum K+ (hyperkalemia) with no increase in intracellular K+. K+ depletion resulted in hyperpolarization of Em as plasma K+ decreased proportionately more than intracellular K+. Low Na+ diet had no effect. Intracellular K+ was decreased in acute acidosis but not in the chronic state. Thus K+ depletion and acute acidosis are associated with intracellular K+ decrease. The fact that hyperpolarization exists in the former and not the latter is a reflection that hypokalemia accompanies the former condition. The hyperpolarizing states of K+ depletion and chronic acidosis are accompanied by decreased excitability and muscle weakness.     

左旋四氢巴马汀加强电针对兔大脑皮层牙髓诱发电位的...

Cortical potentials evoked by stimulation of the contralateral tooth-pulp were recorded epidurally from the SI cortex of rabbits anesthetized with urethane and chloralose. It was found that nociceptive components of the evoked potential consisted of P1 and P2 wavelets with a relative stable peak latency of 22.5 +/- 1.2 ms and 66.1 +/- 1.9 ms respectively. Higher intensity of tooth pulp stimulation was required for appearance of P2 than P1. Diazepam, a non-analgesic sedative, reduced P1 but not P2 amplitude. On the contrary, dolantin, an analgesic, suppressed P2 but showed no significant influence on P1. The results suggest that P2, but not P1 might be related to pain. The effects of l-tetrahydropalmatine (1-THP) and electroacupuncture on P2 were observed on 12 animals. The results showed that both iv l-THP 8mg/kg and electroacupuncture brought forth a decrease in P2 amplitude by 40.3 +/- 14% and 59.3 +/- 10% respectively, while electroacupuncture combined with l-THP produce a further decrease in P2 amplitude by 92.8 +/- 7%. Furthermore, the inhibitory periods of P2 amplitude were significantly prolonged after electroacupuncture combined with l-THP. The results indicated that l-THP enhanced the suppression of P2 by electroacupuncture.     

Available sulphydryl groups of mammalian ribosomes in different functional states

The numbers of sulphydryl groups on NH₄Cl-washed rat liver polyribosomes in different functional states were measured under carefully standardized conditions with ¹⁴C-labelled N-ethylmaleimide and ³⁵S-labelled 5,5-dithio-bis(2-nitrobenzoic acid). Ribosomes denatured with urea had 120 titratable sulphydryl groups, 60 on each subunit, whereas native ribosomes invariably showed fewer available sulphydryl groups. Ribosomes stripped of transfer RNA (S-type ribosomes) had 55 available sulphydryl groups. Ribosomes bearing the growing peptidyl-tRNA at the acceptor site had 41 sulphydryl groups available. If these A-type ribosomes were labelled with ¹⁴C-labelled N-ethylmaleimide and dissociated into subunits, 23 of the labelled sulphydryl groups were found on the 60 S subunit and 19 on the 40 S subunit. After translocation of the peptidyl-tRNA to the donor position on ribosomes (D ribosomes), the number of available sulphydryl groups increased to 72, of which 43 were on the 60 S subunit and 29 on the 40 S subunit. This demonstrates that both subunits participate in the change of peptidyl-tRNA from the A to D positions. When the D ribosomes were reacted with EF2 (elongation factor) and GTP, the available sulphydryl groups increased to 82; addition of EF2 alone or with GDP, GDPCP or ATP failed to cause this increase, which has accordingly been attributed to an energy-dependent conformational change in the ribosome.Ribosomes were reconstructed from subunits with poly(U) and Phe-tRNA. In the presence of poly(U) only, a ribosome with 55 available SH groups was formed, thus corresponding to the stripped ribosomes. When both poly(U) and Phe-tRNA were present, a ribosome was formed with 44 available sulphydryl groups, corresponding approximately to an A-type ribosome. Since no EF1 or GTP was used in reconstructing this ribosome, these data indicate that the conformation of A-type ribosomes is not dependent on EF1 or GTP, but is due to the presence of tRNA at the acceptor site.We therefore incline to the view that the observed changes in available SH groups reflect conformational changes, with an opening up of ribosome structure as it progresses from having the peptidyl-tRNA at the A position to the D position and then binds EF2 and GTP, followed by a restoration of the more compact from when the incoming aminoacyl-tRNA is then bound.     

Nitric oxide and NO-synthases in mammals in different functional states

This review deals with the physical and chemical properties of nitric oxide as well as with the mechanisms and enzymes synthesizing this compound in animals including humans. The cytotoxic, vasodilatory, neuromediatory, and other properties of NO are analyzed. Polyfunctionality of NO in the norm and in pathologies of different genesis is shown. It is suggested that the analysis of the mechanisms of cyclic conversion of nitric oxide and the elucidation of the role of all NO metabolism products in living organisms would allow us to approach a more profound understanding of the NO problem in biology and medicine. It is reasonable to think the knowledge obtained in the course of the studies will permit an elaboration of the strategy and tactics of medical treatment of many diseases occurring on the background of disturbance in the mechanisms of formation and utilization of this compound.     

Comparative effect of thiopental sodium on cortical evoked potentials of different origin

The minimal doses of thiopental sodium (TS) to suppress each of seven varieties of cortical evoked potentials tested were determined in experiments on cats. The preparation had the strongest effect on the following responses: interzonal, arising in the motor cortex to stimulation of somatosensory area I; the reflex pyramidal and late components of the direct pyramidal response. The oligosynaptic transcallosal potential is less sensitive than the above responses but more so than the callosal response. The action of TS on the response depends on the complexity of its organization. The level at which the given cortical response takes place must also be considered. Comparison of the action of TS on the I₁ wave of the pyramidal response and on the dendritic component of the direct cortical response showed that, given equal complexity of its organization, the response arising in deep layers of the cortex is depressed more by TS than the response arising wholly at the level of surface layer I.Institute of Pharmacology, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 4, No. 3, pp. 264–271, May–June, 1972.     

Phase relationships of cerebral cortex potentials in the rabbit during the execution of motor responses

EEG waves phase relations in the sensorimotor and visual cortical areas were studied in 12 rabbits before and during a motor reaction in response to light stimulation. Phase relations in the background activity were characterized by a considerable dispersion (from 26 to 45 degrees). Light stimulation increased the quantity of synphasic EEG oscillations in adjacent cortical points and stabilized the phase shift between EEG waves in the sensorimotor and visual cortical areas. Motor reactions of rabbits to light occurred when theta-rhythm with the most constant phase shift was observed in the EEG of these areas.