Ultrastructural changes in the cerebral cortex of the cat 30 to 60 minutes after anoxia

The ultrastructural changes in the cat sensorimotor cortex during 30- to 60-minute recovery after a 2.5- to 6-minute anoxia have been studied. The most prominent changes were hypertrophy of Golgi apparatus, reorganization of the neuronal endoplasmic reticulum (including the formation of lamellar bodies), increase of the number of lysosomes within nerve cell bodies, formation of deep invaginations of the neuronal cytoplasm into the nucleus, intensification of endocytosis and phagocytosis in the dendrites, appearance of the ultrastructural heterogeneity of the synapses (from normal synapses to depleted ones), normalization of ultrastructure of the part of mitochondrial pool. Glycogen granules were revealed in glial cell processes. The ultrastructural changes after a 6-minute anoxia followed by a 30- to 60-minute recovery were more expressed than after a 2.5-minute one.     

Anoxia-induced changes in cAMP contents in the cat cerebral cortex]

Effect of the cessation of oxygen supply on cAMP content and neuronal spike activity (NSA) in the cortex brain was studied. The interruption of oxygen supply during in first decades of seconds evoked changes in the pattern of NSA, followed with the decrease of cAMP content (to 56 +/- 10%). Then the phase of neuronal hyperactivity and increase of cAMP level (to 198 +/- 26%) took place. The content of cAMP approximated the basal one in 2.5 min anoxia. Anoxia during 5 min resulted in direct opposite shifts of cAMP content in two groups of cats (an increase up to 223 +/- 11%, and decrease up to 75 +/- 8%, respectively, which correlated with individual features of NSA recovery in postanoxic period and values of cAMP basal level in the cortex of different animals. Upon 30 min reoxygenation after 2.5 min anoxia a decline of the content of cAMP (to 63 +/- 12%) accompanied enhance of NSA. This period of reoxygenation after 5 min anoxia demonstrated two types of reactions, observed in different groups of cats: the first type--NSA tended to normalization with the level of cAMP 44 +/- 8% below basal level, and the second type--insufficient recovery of NSA attended by value of cAMP 90 +/- 13% above basal level.     

Effect of hydrocortisone on phosphoinositide metabolism in rat cerebral cortex slices]

Hydrocortisone administered in a dose of 1 and 5 mg per 100 g of mass has increased the rate of 32P turnover in di- and triphosphatidyl inositides up to 170-230% and has no influence on the content of these phospholipids.     

Modification of redox sites of N-methyl-D-aspartate receptors affects changes in bioelectrical activity of olfactory cortex slices induced by anoxia in rats

The effects of the thiol oxidative agent 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB) inhibiting NMDA receptors activity on changes of the evoked focal potentials generation (the NMDA and non-NMDA components EPSP) in response to long-term (LA) and short-term (SA) anoxic exposure which induced functional disturbances or promoted increasing of neurons resistance to LA, were studied on the rat olfactory cortex slices (Wistar-Kyoto). It was revealed that DTNB (200 mkM) effectively protected the depression of the EPSP generation induced by LA in the most tested neurons. In addition, DTNB eliminates the protective effect of the SA on focal EPSP generation evoked by LA. Nevertheless this dependence concerns the NMDA component and, to a lesser extent, the non-NMDA component EPSP. A possible role of changes of the NMDA receptor modulatory redox sites in mechanisms of functional disturbances and increasing neuronal resistance induced by hypoxic influences, is discussed.     

Ultrastructure of the cerebral cortex of the cat in the early recovery period after short-term anoxia

The ultrastructure of cat sensomotor cortex has been studied during a 15-minute recovery after 2.5-6-minute oxygen supply cessation. An increase of osmopholia of free and endoplasmic reticulum bound ribosomes was detected in addition to a great number of altered mitochondria with longitudinal crystal arrangement. Besides, numerous activated synapses, local destructive changes of membrane complexes in dendrite and myelinated axons cytoplasm and glycogen granule accumulation in neuroglia were noticed. During the recovery period more prominent changes were shown after a 6-minute anoxia than after a 2.5-minute one.     

Canges in the monoamine content in the cat brain in a unilateral lesion of the cerebral cortex]

A spectrofluorometric study of the changes in serotonin and noradrenalin content was carried out in the cortex of large hemispheres, the hypothalamus and the midbrain on the 5th-6th day after creation of a pathological focus in the area of the occipital portion of the cortex in 12 cats. Diffuse changes in the bioelectrical activity of the brain were revealed on the EEG at this period: there appeared peak-like variations and slow waves of increased amplitude. There was noted a marked decrease in serotonin content in the cortex of the large hemispheres with the prevalance of an effect in the area directly adhering to the focus of affection. A tendency to reduction in serotonin level was revealed in the hypothalamus and the midbrain. The content of noradrenalin in the mentioned structures of the brain showed no significant change. The significance of the serotoninergic structures of the brain in the mechanisms participating in the restoration of the functional condition of the brain after its experimental injury is discussed.     

The effect of topical application of diethyl- -fluoroglutarate on the metabolism and electrical activity in vivo of cat cerebral cortex

Abstract— The effect of topical application of diethyl-α-fluoroglutarate on the primary response of cat cerebral cortex to thalamic stimulation was investigated, and samples of the involved tissue and of homologous contralateral control tissue were removed at appropriate times for biochemical analyses. Changes in electrocortical response were first noted 30–40 min after topical application of 10 μ1 (52.7 μmol) of the drug to the pericruciate gyrus. A rapid reduction in amplitude of the surface negative component of the primary response was observed initially, followed by amplitude reduction and rapid disappearance of the primary response throughout the cortical field within a few minutes after the change first observed at the surface. The effects were interpreted either as a direct action of the drug on the somadendritic membrane or an inhibition of the excitatory synaptic impingement. Analyses of the tissues removed at the time of maximum electrocortical response indicated profound metabolic changes, including depletion of energy reserves and several Krebs cycle intermediates. Large increases in tissue levels of glucose, glucose 6-phosphate, and pyruvate were found. Changes in amino acids comprised depletion of glutamate with increased tissue levels of aspartate, GABA, NH₃, threonine, serine and alanine. Tissues were also removed at 10 min after topical application of the drug but before the advent of electrocortical changes. Decreased levels of glutamate were associated with a rise in tissue aspartate. Tissue levels of the other amino acids were unchanged. Glucose, glucose 6-phosphate and pyruvate levels were increased, lactate and ATP levels were unchanged, and P-creatine, α-KG and malate levels were reduced. We believe that the observed pattern of changes represents responses of the cerebral cortex to either a block in the synthesis of glutamate or in oxidation of pyruvate, with consequent interference with oxidative and energy metabolism and eventual depression of cortical electrical activity.     

Character of neuronal functional associations according to the content of RNA and SH-groups in the cat cerebral cortex]

A new principle of taxonomy was used for determination of the spaceal character of the neuron cortex associations based on RNA and SH-group contents. The experiments were performed on the intact cat's somatosensory cortex, and after epileptiform activity induced by electrical stimulation. In the intact cortex, the neuronal mosaic of metabolic activity (determined by RNA and SH-group contents) was meshed, whereas in the hemisphere with epileptiform activity this mosaic was formed by less numerous but larger groups of cells. The functional significance of these groups is discussed.     

Effects of oxymethacil on microcirculation and neuronal impulse activity in the cat cerebral cortex in acute fosfakol poisoning]

By using the methods of vital microscopy and extracellular registration of the neuronal activity the effect of oxymethacil (OM) on microcirculation and NSA in cat brain cortex was studied after grave poisoning by organophosphate paraoxon. The rapid depression of NSA together with the pronounced disturbances of microcirculation in cortical vessels were showed after intravenous injection of paraoxon (0.8 mg/kg). The prophylactic injection of OM (5 mg/kg) induced protective effect on the studied parameters. This effect was more pronounced when OM injection was combined with the M-cholinolytic amyzyl. The present data show the reasonableness of antioxidants using for the correction of a brain functional condition damaged by organophosphates.     

Frequency-decrement electroencephalogram analysis by model of rhythmic processes of bioelectrical activity of the cerebral cortex

The results obtained earlier showed that the electroencephalogram is represented as convolution of harmonic functions having negative decrements with discrete evenly discontinuous white Gaussian noise. The method of EEG decrements calculation has been proposed and tested on model processes with set-up parameters and on real rat encephalograms. Studies of decrement characteristics along with amplitude-frequency characteristics of encephalograms in different functional states of animals will extend the possibilities of the mathematical processing of brain signals.     

Ultrastructural changes in the cerebral cortex following transcranial micropolarization]

Electron microscopy of the cerebral cortex in cats and monkeys following transcranial micropolarization (TCMP) demonstrated ultrastructural changes whose degree was dependent on the electric current intensity and the stimulation period. In the focus of stimulation the current affected the brain tissue directly, different elements of the cerebral cortex showing unegual sensitivity to various TCMP regimens. The glia was the first to respond, then the neuronal bodies, and the last -- the synaptic structures. In the areas distant from the TCMP focus synaptic components altered first. The ultrastructural changes revealed were not of pathological character.