[Fatty acids of phospholipids of brain cell nuclei in rat ontogenesis].

Experiments were carried out on the 19-day old rat embryos, the 5- and 45-day old rat pups, and the 1.4-1.5-year old rats. Phospholipids and their fatty acid composition in brain cell nuclei were studied using methods of extraction, two-dimensional thin-layer chromatography, and spectrofluorimetry. In the course of ontogenesis, the percentage of different classes of nuclear phospholipids was changed; at the postembryonic period, the unsaturation index of lipids (phosphatidylcholine and phosphatidylethanolamine) and the content of unsaturated (especially polyenic) fatty acids decreased. Microviscosity of nuclear membranes increased; this changes were also shown earlier in phylogenesis of vertebrates. Thus, the facts revealed in the present work correspond to the recapitulation law. It is suggested that such change of lipid ratio and of composition of their fatty acids as well as of the membrane microviscosity serve for regulation of functions of membrane proteins and have adaptive character.

[Preadaption to nitrogen anesthesia and impairment of brain cortex structure in rats during hypoxia].

The attenuating effect of various variants of hypoxia on hyperbaric anesthesia in rats was studied. The most efficient turned out to be the daily 8-fold one-hour interval 6% hypoxia that decreased manifestations of the anesthesia by 60-67%. The immunocytochemical light optical microscopy showed that in the brain cortex after the 8th séance of such hypoxia the number of neurons with the strong and moderate reaction to heat shock proteins (HSP-70) increased essentially, whereas the number of neurons with the weak reaction to these proteins decreased significantly. After the first hypoxia séances the number of cells with no reaction for the nuclear protein NeuN increased, while after its 8th séance the areas of the absence of neurons appeared. It is believed that one of the main causes of an increase of resistance of the rat organism to nitrogen anesthesia after séances of the many-day interval 6% hypoxia is accumulation of HSP-70 in brain motor cortex cells. At the same time, taking into account a possible cell death and areas of deletion of neurons in cortex at use of the hypoxic action, it is better to use as a preadaptogen the more moderate or not too frequent hypoxia.

[Disturbances in the development of various hippocampal fields in rats as a long-term effect of acute perinatal hypoxia].

The aim of this study was to determine the long-term effects of acute normobaric hypoxia in the perinatal period on the development of a hippocampal formation in rats. The experiments performed have shown that the exposure to hypoxia on postnatal day 2 resulted in a significant damage to the hippocampal field structure. Differential field sensitivity to the damaging factor was also detected. At postnatal day 20, the cell death was found in all the fields and the thinning of pyramidal neuron layers was observed. The neuronal death was mostly expressed in CA4 and CA3 fields. At postnatal day 30, the neuronal death remained significant in CA4 field, while it was reduced in CA3 field and was not found in CA1 field, however, in fascia dentata the death of neurons of the granular layers was increased. Along with it, the dimensions of the pyramidal neuron cell bodies were reduced in all the hippocampal fields. Also, in all the hippocampal fields, the activation of astrocytic reaction was found, which was more expressed in CA4 field, where gliosis was found to remain until prepuberal age (day 30).

[Role of heat-shock proteins of Hsp70 family in changes of narcotic activity of hyperbaric nitrogen during increasing hypoxic stimulus].

The spontaneous motor activity and pose reflexes of male adult rats (Wistar) were observed in the course of high pressure nitrogen compression up to 4,1 MPa. The experiments were carried out under normoxic and hypoxic conditions. Stabile rat motor cortex oxygen tension was recording during the nitrogen compression up to 7,1 MPa under normoxic condition. Sensitivity to nitrogen high pressure to be on the increase under hypoxic conditions. In its turn, resistibility to nitrogen high pressure to be on the decrease under hypoxic conditions (oxygen partial pressure from 0,012 to 0,004 MPa). Quantity of high dencity heat shock proteins (Hsp70) rats motor cortex neurons was 3,44 times higher after course of high pressure nitrogen compression up to 4,1 MPa. For hypoxic exposure (6% O2) the difference was less pronounced - 2,2 times. Data about rat motor cortex neurons Hsp70 concentration under high nitrogen pressure and low oxygen pressure may turn to be a clear base for explanation hypoxic influence on processes of nitrogen narcosis.

[Morphological manifestations of astrocyte local functional activation produced by a short-term total brain ischemia].

The goal of this work was to study changes structural and cytochemical organization of rat hippocampus activated astrocytes after a brief total brain ischemia. By methods of immunocytochemical determination of proteins of intermediate filaments, in was established that 7 days after the ischemia the functional activation of dorsal hippocampus astrocytes is morphologically manifested both as changes of size and shape of the cells and their processes and as accumulation of the intermediate filament proteins -GFAP and nestin. Two populations of the activated astrocytes are formed - more dispersed GFAP-positive astrocytes and nestin-positive astrocytes located predominantly in the area of massive death of nerve cells. The obtained data allow suggesting that the postischemic activation of astrocytes is accompanied by their acquistition of properties characteristic of immature cells of the nervous tissue; however, the absence of morphological signs of dedifferentiation does not permit these cells to be considered responsible for reparational neurogenesis in hippocampus.

[Morphological changes in the fetal part of the allantoic placenta in rats exposed to acute hypoxia].

The aim of this study was to analyze the response of cyto- and syncytiotrophoblast elements of fetal part of allantoic placenta to general acute hypoxia and to determine their morphologic characteristics, which provide the basis for structural changes in placenta and for the disturbances in placental blood flow. Female Wistar rats on day 16 of gestation were exposed to hypoxia (8% oxygen concentration in the gas mixture) for 1 hr. Placenta was studied 1 and 3 days later. Short-term acute hypoxia during pregnancy was shown to induce an impairment of formation and maturation of the fetal part of placenta. In the labyrinth zone, apoptosis was enhanced and a significant number of hyperchromatic nuclei appeared in cyto- and syncytiotrophoblast, which lead to the loss of some cells of cytotrophoblast and resulted in the retardation of its development and transformation into syncytiotrophoblast. One day following hypoxia, a stimulation of adaptive processes was evident as demonstrated by a dramatic rise of mitotic activity in the cytotrophoblast of the labyrinth zone of placental fetal part. However, a delay of the labyrinth zone development persisted till the end of pregnancy. Number and volume of fetal blood vessels were decreased as compared to those in control. A sharp decline of number and size of sinusoids containing maternal blood as well as a significant decrease of blood volume in the sinusoids, suggest a spasm of the uterine and placental vessels causing an impairment of utero-placental blood circulation and development of placental insufficiency.

Intracerebroventricular administration of creatine protects against damage by global cerebral ischemia in rat.

Although a large body of evidence shows that pretreatment of brain tissue with creatine protects against anoxic injury in vitro, only a couple of papers have investigated creatine protection in vivo, and they yielded conflicting results. We attempted to clarify how creatine may be protective in an in vivo model of global cerebral ischemia (GCI). We administered creatine either before of after GCI. We decided to administer it by intracerebroventricular infusion, to maximize its bioavailability to the brain. Our findings show that creatine is clearly protective in vivo when administered before ischemia. In that case, histological evaluation of damage was consistently improved in all regions examined, and neurological score was better in creatine-treated rats than in controls. When administered after ischemia, histology was improved in the hippocampus, while only a not significant trend toward improvement was observed in the cerebral cortex and in the caudo-putamen. Neurological score was not improved by creatine administration after GCI. Our findings show that creatine administration is protective in vivo. Such protection was clear in the case of pretreatment, and was present, to a lesser degree, when treatment was started after ischemia. Our results should encourage further research in the possible role of creatine therapy in neuroprotection.

Structural organization of astrocytes in the rat hippocampus in the post-ischemic period.

The aim of the present work was to study the location and structural organization of astrocytes in the rat hippocampus, which contain immunoreactive glial fibrillary acid protein (GFAP) after ischemic damage to the brain after intracerebroventricular administration of the neuroprotective agent creatine and without treatment. Light microscopy and immunocytochemical methods were used to study the brains of 26 adult male Sprague-Dawley (Koltushi) rats, some of which were subjected to total cerebral ischemia (12 min) under anesthesia with subsequent reperfusion (seven days). Creatine was given to 11 animals intracerebroventricularly using an osmotic pump (Alzet Osmotic Mini-Pump). The results showed that GFAP-immunoreactive hippocampal astrocytes were concentrated in two main zones (the stratum lacunosum-moleculare of field CA1 and the stratum polymorphae of the dentate fascia). The neuroprotective effect of creatine had the result that moderate ischemic damage to the hippocampus did not lead to changes in the zones containing activated astrocytes. The redistribution of GFAP-positive astrocytes in the post-ischemic period was associated with loss of pyramidal neurons in cytoarchitectonic field CA1. Complete loss of pyramidal neurons in this area of the hippocampus leads to a qualitatively new level of astrocyte activation--proliferation.

The roles of nitric oxide and carbon dioxide gas in the neurotoxic actions of oxygen under pressure.

The hypothesis that in conditions of hyperbaric oxygenation, nitric oxide (NO) modulates the vasodilatory effect of CO2 in the brain and thus accelerates the neurotoxic action of oxygen was verified experimentally. Conscious rats breathed atmospheric air or oxygen at 5 atm and blood flow in the striatum was measured before and after inhibition of carbonic anhydrase with acetazolamide, which causes retention of CO2 in the brain. Acetazolamide (35 mg/kg) increased blood flow in the animals when breathing air by 38 +/- 7.4% (p < 0.01), while preliminary inhibition of NO synthase with N(omega)-nitro-L-arginine-methyl ester (L-NAME, 30 mg/kg) significantly weakened its vasodilatory action. Inhibition of carbonic anhydrase in animals breathing hyperbaric oxygen at 5 atm prevented cerebral vasoconstriction, increased brain blood flow, and accelerated the development of oxygen convulsions. The vasodilatory effect of acetazolamide in hyperbaric oxygenation was significantly reduced in animals pretreated with the NO synthase inhibitor, such that the latent period of convulsions increased. The results obtained here provide evidence that in conditions of extreme hyperoxia, NO modulates the cerebral hyperemia developing in conditions of CO2 retention in the brain and accelerates the development of the neurotoxic actions of hyperbaric oxygen.

[Nitric oxide and carbon dioxide in neurotoxicity induced by oxygen under pressure]. / Rol' oksida azota i uglekislogo gaza v neirotoksicheskom deistvii kisloroda pod davleniem.

Hyperbaric oxygen (HBO2) causes CO2 retention in the brain that leads to the increase in cerebral blood flow (CBF) by poorly understood mechanisms. We have tested the hypothesis that NO is implicated in CBF-responses to hypercapnia under hyperoxic conditions. Alert rats were exposed to HBO2 at 5 ata and blood flow in the striatum measured by H2 clearance every 10 min. Acetazolamide, the inhibitor of carbonic anhydrase, was used to increase brain PCO2. CBF responses to acetazolamide administration (30 mg/kg, i.p.) were assessed in rats breathing air at 1 ata or oxygen at 5 ata with and without NOS inhibition (L-NAME, 30 mg/kg, i.p.). In rats breathing air, acetazolamide increased CBF by 34 +/- 7.4% over 30 min and by 28 +/- 12% over 3 hours while NOS inhibition with L-NAME attenuated acetazolamide-induced cerebral vasodilatation. HBO2 at 5 ata reduced CBF during the first 30 min hyperoxia, after that CBF increased by 55 +/- 19% above pre-exposure levels. In acetazolamide-treated animals, no HBO, induced vasoconstricton was observed and striatal blood flow increased by 53 +/- 18% within 10 min of hyperbaric exposure. After NOS inhibition, cerebral vasodilatation in response to acetazolamide during HBO2 exposure was significantly attenuated. The study demonstrates that NO is implicated in acetazolamide (CO2)-induced cerebral hyperemia under hyperbaric oxygen exposure.

[Structural characteristics of astrocytes from the rat hippocampus in postischemia]. / Strukturnaia organizatsiia astrotsitov gippokampa krysy v postishemicheskii period.

The aim of this investigation was to study the distribution and structural organization of rat hippocampal astrocytes containing immunoreactive glial fibrillary acidic protein (GFAP) after ischemic damage of the brain in the animals treated with intraventricular infusion of creatine as a neuroprotective drug, and in those which received no treatment. Using the methods of light microscopy and immunocytochemistry, the brain of 26 mature Sprague-Dawley (Koltushi) rats was studied. Some animals were narcotized and subjected to general brain ischemia (lasting for 12 min) followed by a reperfusion (for 7 days). Creatine was infused intraventricularly to 11 animals using an automatic Alzet osmotic minipump. It was found that GFAP-immunoreactive hippocampal astrocytes were concentrated within two major areas (stratum lacunosum-moleculare CA1 and fascia dentata stratum polymorphae). As a result of neuroprotective effect of creatine, moderate ischemic damage of the hippocampus was not followed by the changes in the zones of activated astrocyte localization. Redistribution of GFAP-positive astrocytes in postischemic period was caused by the loss of pyramidal neurons in cytoarchitectonic field CA1. Complete loss of pyramidal neurons in this hippocampal area resulted in a qualitatively new level of astrocyte activation--their proliferation.

Brain blood flow modulates the neurotoxic action of hyperbaric oxygen via neuronal and endothelial nitric oxide.

Studies on conscious rats with inhibition of NO synthase were used to assess the dynamics of brain blood flow and EEG traces during hyperbaric oxygenation at 4 or 5 atm. Oxygen at a pressure of 4 atm induced cerebral vasoconstriction in intact animals and decreased blood flow by 11-18% (p < 0.05) during 60-min exposure to hyperbaric oxygenation. Paroxysmal EEG activity and oxygen convulsions did not occur in rats at 4 atm of O2. At 5 atm, convulsive activity appeared on the EEG at 41 +/- 1.9 min, and blood flow decreased significantly during the first 20 min; blood flow increased by 23 +/- 9%, as compared with controls, (p < 0.01) before the appearance of convulsions on the EEG. Prior inhibition of NO synthase I (NOS I) and NO synthase III (NOS III) with N(omega)-nitro-L-arginine methyl ester (L-NAME, 30 mg/kg) or inhibition only of NOS I with 7-nitroindazole (7-NI, 50 mg/kg) prevented the development of hyperoxic hyperemia and paroxysmal spikes on the EEG during hyperbaric oxygenation at 5 atm. These results show that hyperbaric oxygen induces changes in cerebral blood flow which modulate its neurotoxic action via nitric oxide synthesized both in neurons and in cerebral vessels.

[Cerebral blood flow modulates hyperbaric oxygen induced neurotoxicity by neuronal and endothelial nitric oxide]. / Mozgovoi krovotok moduliruet neirotoksicheskoe deistvie giperbaricheskogo kisloroda s pomoshch'iu neironal'nogo i endotelial'nogo oksida azota.

The goal of work was to reveal changes in microcirculation of the rat brain and the role of nitric oxide (NO) in development of seizures at hyperbaric oxygen exposure. The Wistar rats with implanted paired platinum electrodes in left and right striatum were used for experiments. The latency of seizures was defined by the EEG, the cerebral blood flow (CBF) was measured by hydrogen clearance. One group of animals was exposed to a 5-ata oxygen, while the others before oxygen treatment were injected with: Nw-nitro-L-arginine methyl ester (L-NAME), blockator of constitutive NO synthase; 7-nitroindozol (7NI), specific inhibitor of neural NO synthase. The latency of seizures was 41 +/- 1.9 min at 5 ata oxygen exposure. CBF was decreased to 10-14% but before seizures it increased to 23 +/- 9%. L-NAME and 7NI prevented development of hyperoxygen hyperemia and onset of seizures. The results indicate occurrence of hyperbaric oxygen changes of the CBF that modulate neurotoxic effects of NO in neurons as well as in cerebral vessels.