Orientation sensitive properties of visually driven neurons in extrastriate area 21a of cat cortex.

Orientation sensitive properties of extrastriate area 21a neurons were investigated. Special attention was paid to the qualitative characteristics of neuron responses to the different orientations of visual stimulus motion across neuron classical receptive fields (CRF). The results of experiments have shown that a group of neurons (31%) in area 21a with specialized responses to moving visual stimuli changed their direction selective (DS) characteristics depending on the orientation of the stimulus movement. Some neurons reveal an abrupt drop of the direction sensitivity index (DI) to certain orientation (58%), and some show significant increase of DI at one of applied orientations of stimulus motion (22%). Detailed investigation of response patterns of non-directional neurons to different orientations of stimulus motion have revealed clear-cut qualitative differences, such as different regularities in the distribution of inter-peak inhibitory intervals in the response pattern in dependence of the orientation of stimulus motion. The investigation of neuron CRF stationary functional organization did not reveal correlations between RF's spatial functional organization, and that of qualitative modulations of neuron response patterns. A suggestion was put forward, that visual information central processing of orientation discrimination is a complex integrative process that includes quantitative as well as qualitative transformations of neuron activity.

Spatial summation processes in the receptive fields of visually driven neurons of the cat's cortical area 21a.

The spatial summation in receptive fields (RF) of single neurons in cat's extrastriate area 21a was investigated as a basic neurophysiological substrate for central integration processing of visual information. The results showed that the majority of investigated neurons changed their response patterns with gradual increase of applied stimulus size. In approximately 82% of cases the suppression of neuron discharges was observed when the length of the moving strip exceeded that of the RF. In some neurons the increased size of the moving stimulus leads to the changes in the RF substructure. Receptive fields of neurons recorded at the same microelectrode penetration depth showed a great variety of RF superpositions distributed in a spatially asymmetric manner. As a result, every single RF consists of multiple sub-regions within the RF, differing from each other by the number of superimposed RF-s (density factor). We suggest that such complex spatial organization of the RF provides the neurophysiological basis for central integration processing of the visual information.

[Influence of mental and emotional stress on the levels of electrolytes in the saliva of senior schoolchildren]. / Vliianie umstvenno-émotsial'nogo napriazheniia na soderzhanie élektrolitov v sliune starsheklassnikov.

Salivary Na+,K+-excretory function was studied in senior schoolchildren-entrants during an academic year and entrance examinations. The time course of changes in the salivary levels of Na+ and K+ in entrants during an academic year was undulating. In late October that is coincident with the beginning of lessons given by tutors, the salivary content of Na+ reduced while that of K+ increased. The second peak of decreased excretion rates for Na+ and increased excretion rates for K+ and that of less Na+/K+ ratios was observed in May on the eve of entrance examinations. On the eve of the examinations, 70% were observed to have tachycardia, elevated levels of integral parameters of cardiac rhythm regulation, a considerable reduction in the concentration of Na+, and an increase in the level of K+ with less Na+/K+ ratios. The pattern of the observed changes also retained in the postexamination period. On the eve of the examinations, 30% were found to have lowered levels of integral parameters of cardiac rhythm regulation and elevated levels of Na+. After an examination, there was a reduction in Na+ excretion which did not yet achieve the initial level. The mechanisms responsible for ionic shifts in the composition of saliva during psychoemotional stress are discussed.

Increased nitric oxide deactivation by polymorphonuclear leukocytes in patients with intermittent claudication.

PURPOSE: Local activation of polymorphonuclear leukocytes (PMNLs) is considered an important aspect of the pathogenesis of intermittent claudication, although concrete mechanisms of their effects on circulatory homeostasis in peripheral atherosclerotic disease remain unclear. This study evaluated the ability of PMNLs to deactivate nitric oxide (NO), a key regulator of regional circulation, as a possible factor determining PMNL involvement into ischemic disorders in patients who have intermittent claudication before and after vascular reconstruction. METHODS: A total of 57 patients who had peripheral occlusive disease in an aortofemoral segment before surgical treatment (group 1) and 65 patients who had similar occlusive lesions and other clinical and demographic data 6 to 12 months after undergoing inflow vascular reconstruction (group 2) were examined. All patients from group 2 had anatomically patent grafts; their satisfaction and level of function after surgical treatment were assessed by a five-point questionnaire. The sex- and age-matched control group included 35 subjects. NO activity was bioassayed by measuring its ability to increase cyclic guanosine monophosphate (cGMP) accumulation in rat fetal lung-cultured fibroblasts (RFL-6 cells). The ability of PMNLs to deactivate NO was characterized as the percent decrease in NO-induced cGMP accumulation in RFL-6 cells. RESULTS: Stimulated PMNLs caused inhibition of the activity of authentic NO; accumulation of cGMP induced by sodium nitroprusside was not affected. PMNLs from patients with peripheral atherosclerotic disease either before or after vascular reconstruction had a more marked capacity of NO inactivating than the cells from healthy subjects. For both groups of patients, levels of PMNL-induced NO deactivation were higher for patients with diabetes, and especially both diabetes and arterial hypertension. For both groups of patients, there was no correlation between levels of PMNL-induced NO deactivation and resting ankle-brachial indexes (ABIs). In contrast, close correlation was revealed between levels of PMNL-induced NO deactivation and postexercise ABIs and percent decrease in resting ABIs after exercise in patients evaluated either before or after surgical treatment. CONCLUSIONS: The ability of stimulated PMNLs to deactivate NO is elevated in peripheral occlusive disease and may be implicated in the pathogenesis of intermittent claudication. In patients who underwent successful recanalization of magistral arteries, levels of PMNL-induced NO deactivation remained higher than in control subjects. The increase in the ability of PMNL to deactivate NO positively correlated to ABI decreases after exercise in patients with peripheral occlusive disease either before or after surgical treatment.

Responses of cat's dorsal hippocampal neurones to moving visual stimuli.

Response properties of visually driven neurones in the cat's hippocampal region were investigated. Out of 688 single cells observed 181 (26%) were visually driven. Ocular dominance was determined for 147 of those cells, 90 of which were driven only by the contralateral eye, 20 were driven exclusively by ipsilateral eye and 37 neurones could be activated by both eyes. Receptive field boundaries were outlined for 157; 152 of those neurones were movement-sensitive, and 125 neurones were sensitive to stationary stimuli. A small group of neurones (13%) showed more pronounced reactions to the vertical direction of motion. Some neurones (22%) revealed sensitivity to the shape and size of the applied visual stimuli. These results confirmed earlier data indicating that visually driven neurones in hippocampal region possess complex properties. They are probably involved in a higher level of visual information processing.

Spatial summation processes in visually driven neurones of cat's pretectal region.

The spatial summation processes of single neurones of cat's pretectal region were investigated with moving and stationary visual stimuli. The results indicate that the majority of the investigated neurones changed their responses essentially at the gradual increase of size of the applied stimuli (i.e. showed negative or positive summation). Particularly, direction non-sensitive neurones showed symmetrical changes of spatial summation curves in response to two opposite directions of movement. By contrast, in some direction sensitive neurones different characteristics of responses for the two opposite directions of movement were observed. Thus the number of discharges in the responses to the preferred direction could increase or decrease at the gradual increase of the moving stimulus size, while the responses to the null direction could remain stable or vice versa. The same was observed for the "ON" and "OFF" responses in the ON-OFF neurones. Thus, it appears that the pattern of responses of a given neurone to different directions of movement and to the "on" and "off" periods of stationary stimulation are shaped by independent mechanisms.

[Evaluation of the degree of ischemia of the lower extremities in arteriosclerosis obliterans based on the levels of toxic metabolites in the blood]. / Otsenka glubiny ishemii nizhnikh konechnostei pri obliteriru- iushchem ateroskleroze arterial'nogo rusla po urovniu toksichnykh metabolitov krovi.

An attempt is made to elaborate biochemical criteria of the depth of ischemia in atherosclerotic lesions of the lower limb arterial channel, based on the degree of manifestation and character of the metabolic changes. The study revealed increased content of toxic metabolites--middle mass molecules (MMM), hydroperoxides, and circulating immune complexes (CIC) in the blood of patients. The content of MMM and hydroperoxides correlated with the degree of limb ischemia. Determination of MMM, hydroperoxides, and CIC may help in evaluating the severity of the pathological process and solving problems of preoperative management of patients from the standpoint of prescribing extracorporeal methods of detoxification.

Properties of visually driven neurons in cats pretectal region.

Properties of visually driven neurons in the cat pretectal region were studied. A detailed investigation of the receptive field (RF) structure revealed, in the majority of neurons, irregular shapes of RF contours. Dark-sensitive and bright-sensitive zones of a neuronal RF had different spatial locations. The majority of pretectal neurons were movement-sensitive and reacted weakly to stationary flashing spots. Although no clear-cut orientation sensitivity was found in the pretectal neurons, some orientations of motion were, nevertheless, more effective. In some cases a non-directional response could be transformed into a directionally-sensitive one by changing the orientation of motion. Out data confirm earlier observations that the pretectal region is involved in the central processing of visual information.

[The action of heart factor H1 on the synthesis and uptake of dopamine and noradrenaline in the rat heart]. / Deistvie serdechnogo faktora H1 na sintez i zakhvat dofamina i noradrenalina v serdtse krys.

The action of heart factor H1 on the synthesis and uptake of dopamine and noradrenaline in the atria and ventricle of rat heart and also the participation of Ca2+ and ATP in the action of H1 was studied. It has been shown, that H1 in the doses of 2 and 20 mU/ml increases the synthesis of 14C-dopamine in the atria by 43-44% and does not effect on this process in ventricle. The synthesis of 14C-noradrenaline in the atria increases in the presence of H1 (2-20 mU/ml) by 64 and 40%. A dose-dependent decrease of 3H-dopamine uptake in the atria under the influence of H1 was observed. The uptake of 3H-noradrenaline in the ventricle as well as in the atria is not altered in the presence of H1. In the absence of Ca2+ H1 in not caused any stimulation of 14C-dopamine and 14C-noradrenaline synthesis in the atria. But in the absence of both Ca2+ and ATP the stimulating effect of H1 on the synthesis of 14C-noradrenaline is maintained.

[Responses of neurons of dorsal hippocampus field CA1 to visual stimulation in the cat]. / Otvety neironov polia CA1 dorsal'nogo gippokampa koshki na zritel'nye razdrazheniia.

In acute experiments on cats with pretrigeminal brain-stem section responses of 46 hippocampal neurons were investigated. Most neurons (71%) had small sizes of visual receptive fields. The responses of neurons to stationary stimuli were of phasic (66%), as well as tonic (34%) types. All neurons investigated responded to dark and bright spots moving across their receptive fields. 27% of sensitive neurons were direction-selective. Some neurons respond more intensively to moving dark spots in comparison with bright spots or bars. The results presented confirmed the suggestion that certain neurons in the CA1 field of the dorsal hippocampus have highly organized visual sensory input.

[Organization of the substructure of the receptive fields of neurons of the lateral suprasylvian area of the cat cortex]. / Organizatsiia substruktury retseptivnykh polei neironov lateral'noi suprasil'vievoi oblasti kory koshki.

The substructure of receptive fields of the lateral suprasylvian area neurons was investigated in cats. It was shown that the majority of receptive fields investigated were organized of subelements with different qualitative characteristics according to their responses to moving visual stimuli. With the unmasking method of stimulation, small amplitudes of the motion evoked, as a rule, directional responses, whereas with the masking method the same amplitude of the motion produced nondirectional responses. Some receptive fields of the investigated neurons responded vigorously to the motion of borders of the visual stimuli. The heterogeneity in organization of the substructure of the receptive fields was explained by the convergence of different inputs to the investigated neurons.

[Receptive fields of lateral suprasylvian neurons in the cat]. / Retseptivnye polia neironov lateral'noi suprasil'vievoi oblasti kory mozga koshki.

The receptive field structure of single neurons in lateral suprasylvian area was investigated in cat. Receptive fields were of larger sizes comparing with visual cortex (up to 2000 sq. deg.). The dimensions of receptive fields measured by black objects and light spots revealed differences, the receptive fields being usually larger when black objects were used. The experiments showed that the visually sensitive neurons of the lateral suprasylvian area could be activated by stationary flashing light stimulus. The neurons were qualified in three groups as on, off and on-off. Distribution of the activity all over the receptive field surface was investigated using flashing light spots. Receptive fields with the plural discharge centres were revealed.