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N Zarchin

Publications and source records attributed to N Zarchin.

At least 19 recordsLinked to original sources
PubMed2003

Relationship between intracranial pressure and cortical spreading depression following fluid percussion brain injury in rats.

Traumatic brain injury (TBI) is known to be accompanied by an increase in intracranial pressure (ICP) and in some cases, by spontaneous generation of cortical spreading depression (CSD) cycles. However, the role of CSD in the pathophysiology of cerebral contusion is still unknown. A multiparametric monitoring assembly was placed on the right hemisphere of the rat brain to evaluate ICP, DC potential, extracellular K(+), cerebral blood flow (CBF), and electrocorticogram in 27 rats during 5 h. Fluid percussion brain injury (FPBI) with the magnitude of the impact 2.9, 3.3, 4.1, and 5.0 atmospheres was induced to the left parietal cortex in animal groups A, B, C, and D, respectively. A slow increase in ICP was evident, and was pronounced in group C and especially in group D, where four of nine animals died during the monitoring. At the end of the 5 h experiment, the mean ICP levels were 6.75 +/- 2.87, 8.40 +/- 2.70, 12.75 +/- 4.03, 29.56 +/- 9.25, and the mean total number of CSD cycles was 2.00 +/- 1.41, 4.29 +/- 4.23, 11.71 +/- 13.29, and 20.11 +/- 19.26 in groups A, B, C, and D, respectively. The maximal level of intensity of CSD cycle generation after FPBI was obtained in group D, where almost constant activity was maintained until the end of the experiment. A significant coefficient of correlation between ICP level and total number of CSD cycles was found for all ICP measurements (r = 0.47-0.63, p < 0.05, n = 27), however more significant (p < 0.001) was the coefficient during the period of monitoring between 2 and 4 h after FPBI. Our results suggest that numerous repeating CSD cycles are typical phenomena in moderate and especially severe forms of FPBI. The rising number of CSD cycles under condition of an ICP level >/=20 mm Hg may demonstrate, with high probability, the unfavorable development of TBI, caused by growing secondary hypoxic insult.

Animals↗
PubMed2002

Hyperbaric oxygenation affects rat brain function after carbon monoxide exposure.

The application of hyperbaric oxygenation (HBO2) has been recommended for correction of neurological injury in severely CO-poisoned patients. However, the mechanisms of HBO2 action on brain mitochondrial function under the circumstances is not yet understood completely. In the present study, the effect of HBO2 on the rat brain after CO exposure was evaluated by measuring the intramitochondrial NADH and its responses to anoxic test or repetitive induction spreading depression (SD) leading to brain activation. A unique monitoring system for bilateral monitoring of brain NADH redox state was used. Rats were exposed to 3000 ppm CO for 30 (group A) or 60 min (C). In groups B and D, after CO exposure, the rats were exposed to HBO2 (3 atm abs for 30 min). Following CO exposure in groups A and C, a definite decrease in the amplitude of the NADH response and significant increase in the number of waves of NADH was noted during induced cortical SD. Anoxic test in these two groups led to a significant decrease of maximum levels of NADH (reduction) at the end of observation. The amplitude, and the number of SD waves and magnitude of NADH deviation during anoxic test in group B after application of HBO2, was not significantly different from the values measured under the initial conditions. However, in group D, tendency of maintenance of the parameter's initial level was weaker or absent. The results obtained indicated that suppression of brain energy metabolism is a characteristic manifestation of CO poisoning in rats. Restoration of cerebral energy metabolism by adequate dosage of HBO2 may become an important factor for recovery of brain activities after CO poisoning.

Animals↗
PubMed2000

Brain multiparametric responses to carbon monoxide exposure in the aging rat.

The multiparametric monitoring system was applied to study the effects of 2000 ppm carbon monoxide (CO) on brain functions in vivo in the aging rat. The vasodilatory (non hypoxic) effects of CO on CBF in normal adult rats, which were shown in concentrations of 1000-2000 ppm involved the effect of nitric oxide (NO). Energy metabolism was evaluated by optical monitoring of CBF and mitochondrial function by fluorometry of NADH. Ionic homeostasis was evaluated by monitoring the extracellular level of K(+) and H(+) and the DC steady potential. Seven aging rats (24 months) were exposed to 2000 ppm for 60 min and 120 min of recovery, while five control rats were exposed to air under the same conditions. A comparison between the CO group and the control group showed that the changes in CBF, NADH and light reflectance were not statistically significant while extracellular K(+) was elevated and tissue pH became more acidic. Thus, the typical CO induced increase in CBF, was not recorded in the aging rats. We concluded that the brain vasodilatory response to CO was not active in the aging rat, while the ionic homeostasis responses were similar to those found in the adult rat.

Aging↗
PubMed2000

The effect of hyperbaric hyperoxia on brain function in the newborn dog in vivo.

Age is a natural factor that has been found to significantly affect sensitivity to hyperbaric hyperoxia (HBO). Exposure to HBO may lead to damages in the energy metabolism of the brain cells. The aim of this study was to test the effect of HBO on the metabolic, hemodynamic and electrical activities in the newborn dog. The study was performed using one-day- to 70-day-old puppies. The puppies were placed in a pressure chamber. The pressure of pure O2 in the chamber was raised by 5 atmospheres (ATA, 75 psi = 6 ATA) within 10 min. The first biochemical change to take place during HBO was oxidation of mitochondrial NADH. The age of the puppy was found to affect the time to the initiation of seizures. In the puppies under the age of 24 days, the average time was 35.1 +/- 5.9 min. In the puppies of 24 days old and older, the average time was 5.1 +/- 0.8 min. In the younger puppies, there was a later occurrence of blood vessel contractions and a longer life span compared to the older puppies. The comparison between the puppies of different ages during exposure to HBO showed differences in the metabolic response, hemodynamic changes and electrical activity. These differences can partially explain the higher resistance in the younger puppies to HBO.

Age Factors↗
PubMed2000

Brain metabolic and ionic responses to global brain ischemia in the newborn dog in vivo: 1. Methodological aspects.

A variety of methods has been used in order to obtain a state of acute cerebral ischemia. Most of these methods suffered from drawbacks such as irreversible ischemia, difficult to obtain total ischemia and heart injury. The aim of this study was to develop a new method for induction of global or partial cerebral ischemia in the newborn dog at various post-natal ages. A multi-parameter monitoring system (MPA) measures the metabolic (mitochondria NADH oxidation/reduction state), hemodynamic (reflectance), ionic (extracellular potassium and calcium) and electrical changes (ECoG) continuously and simultaneously in the puppy's brain in vivo. A hole was made in the chest cavity, the two large arteries supplying blood to the brain, the brachiocephalic and the subclavian arteries (B + S) were isolated and occluded during the monitoring. In most of the animals, occlusion of these two arteries alone resulted in partial ischemia. For obtaining 100% ischemia, we occluded both the B + S arteries as well as the aortic arch. Immediately at the onset of ischemia, an increase (reduction) of NADH begins. During complete ischemia the average time until maximal increase was 4 min, compared to ischemia of up to 50% of the maximal reduction of the NADH where the average time was 1 min. After reperfusion of the brain, mitochondria recovery was very rapid and the average time until return of this parameter to its pre-ischemic level was 1.4 +/- 0.2 min. The ionic changes which occurred immediately upon the onset of ischemia were the accumulation of extracellular potassium ions was recorded. The rate of potassium ion accumulation was dependent on the severity of the ischemia (range 0.19 +/- 0.08-2.2 +/- 0.4 mM min-1). The increase in the extracellular potassium ion concentration occurs in two stages, an initial slow stage and a second rapid stage (13.0 +/- 1.8 mM). The results presented in this paper suggest and prove the usefulness of a new approach for global and partial ischemia in the newborn dogs. In addition, our results assess the brain metabolic, ionic, hemodynamic and electrical responses to brain ischemia in the puppies.

Animals↗
PubMed2000

Metabolic and ionic responses to global brain ischemia in the newborn dog in vivo: II. Post-natal age aspects.

The main difference between newborn and adult brains is expressed in the relative resistance of the newborn brain to oxygen deprivation. The aim of the present study was to examine the effect of global ischemia in canine puppies of three different ages on the metabolic, ionic and electrical activity of the brain and to study the basic mechanisms underlying the relative resistance of the newborn brain in ischemic episode. The puppies were divided into three age groups. The young group included 0-6-day-old puppies (n = 16), the intermediate group included 7-19-day-old puppies (n = 21), and the 'adult' group included puppies aged 20 days or more (n = 17). Statistical analysis of the results led to the following conclusions: The younger the puppy, the longer is the time until the occurrence of the secondary reflectance increase SRI (13.0 +/- 1.9 min vs. 5.3 +/- 0.5 min). The younger the puppy, the longer the time until onset of potassium leakage from the cells (0.9 +/- 0.1 min vs. 0.35 +/- 0.05 min) and the lower the amount of potassium leakage (9.6 +/- 2.8 mM vs. 21.7 +/- 4.8 mM). The rate of pumping of the potassium ions into the cells during the recovery stage was higher in the oldest group (1.2 +/- 0.2 mM min-1 vs. 0.38 +/- 0.1 mM min-1). It was possible to speculate that in the young puppies there is uncoupling of the oxidative phosphorylation from respiration and as a result, there is a lower, if any, rate of ATP synthesis. It seems that the newborn brain is able to cope with a decrease in available energy for a longer period of time. This is apparently due to differences in membrane characteristics and an improved ability to retain ionic equilibrium across both sides of the membrane.

Aging↗
PubMed1999

Inter-relation between hemodynamic, metabolic, ionic and electrical activities during ischemia and reperfusion in the gerbil brain.

The aim of this study was to examine the inter-relation between the hemodynamic events, energy metabolism, extracellular potassium and electrical activity during the acute phase of transient ischemia in the gerbil brain. It has already been shown that partial ischemia in the gerbil brain causes changes in the blood flow, oxygen tension, electrical activity and potassium ion efflux. However, the description of the event during brain recovery from transient ischemia is not documented. In order to enable a better understanding of the pathophysiology during the ischemia as well as during reperfusion, we used the multiparametric assembly system. This system enables simultaneous and continuous monitoring of CBF, intra-mitochondrial NADH, extracellular potassium, DC potential and ECoG. Twenty anesthetized gerbils underwent reversible carotid artery occlusion procedure for 3-4 min. While monitoring the various parameters until complete recovery was reached, we found high correlation between the CBF and the NADH during occlusion as well as during the reperfusion period. However, CBF at the reperfusion period increased above the basal level while NADH returned to base line without an undershoot, suggesting that the mitochondrial need for oxygen necessary for the production of ATP is not the only factor influencing CBF during reperfusion. Furthermore, NADH returned to its normal level before extracellular potassium ion levels recovered to the baseline. This may suggest that ATP was no longer the limiting factor and ion pump activity became the factor determining and affecting the recovery processes.

Animals↗
PubMed1999

Brain metabolic and ionic responses to systemic hypoxia in the newborn dog in vivo.

Newborns are less sensitive than adults to hypoxic/ischemic injury. However, research into the mechanism of the newborn's relative resistance to reduced brain oxygen levels is relatively scarce, and the time-scale for the disappearance of resistance is not known. The multiprobe assembly (MPA) has enabled us to examine the resistance of puppies at various ages to hypoxia via continuous, simultaneous, on-line measurement of various ionic, metabolic and electrical parameters from the cerebral cortex. The parameters measured included electrocorticogram (ECoG), direct current (DC) steady state potential, extracellular potassium (Ke+) and calcium ion concentrations and intra-mitochondrial Nicotine amide adenine dinucleotide NADH redox levels. These parameters were measured under various degrees of hypoxia (fraction of inspiration oxygen was between 0-10%) in 6-h-old to 24-week-old puppies (n = 44). Sensitivity to hypoxia increased with age, being expressed in the leakage of potassium ions out of the cells (0.3 +/- 0.07 mM in the younger puppies and 3.0 +/- 1.3 mM in the older puppies) following an increase in intra-mitochondrial NADH redox levels. Potassium ion (Ke+) leakage was apparently due to depleted energy stores resulting from an impairment in the balance between oxygen supply and demand. Although the overall effect was similar, the kinetics of these changes were much faster in the older puppies. The time to initial increase of extracellular K+ was 2.5 +/- 0.1 min in the younger puppies and 0.9 +/- 0.1 min in the older puppies. The time to maximum increase of NADH was 3.2 +/- 0.2 min in the younger puppies and 1.4 +/- 0.1 min in the older puppies. Our results indicate that the older puppies utilize the existing oxygen faster than the younger puppies. It is concluded that the increased resistance of newborn puppies to hypoxia is due to intrinsic properties of the brain itself, like the ability of the membrane to maintain ionic homeostasis.

Age Factors↗
PubMed1998

Responses of rat brain to induced spreading depression following exposure to carbon monoxide.

Until recently carbon monoxide (CO) was known only for its noxious effects. Exposure to CO results in an autoregulatory increase in cerebral blood flow (CBF). Little information is available on brain energy metabolism under low CO concentrations and on the effect of CO on the stimulated brain. In this study cortical spreading depression (SD) was induced in order to cause transient brain depolarization and increased energy demand. The multisite assembly (MSA), which contains four bundles of optical fibers for monitoring the intramitochondrial NADH redox state and tissue reflectance as well as four DC electrodes enabling measurement from four consecutive points on the cerebral cortex, was used to measure energy metabolism and the propagation of SD waves during exposure to CO. CBF in the contralateral hemisphere was measured using the laser Doppler technique. Three experimental groups of animals were examined: SD was induced during exposure to 1000 ppm CO, immediately after exposure to CO and 90 min after cessation of exposure to CO. Three control groups were also examined, in which the animals underwent the same procedures but were not exposed to CO. In all animals exposure to CO was followed by a significant increase in CBF. The greatest effect was found when SD was induced immediately after cessation of exposure to CO. SD wave frequency decreased when induced immediately after exposure to CO, whereas it increased when SD was induced 90 min after exposure. The amplitude of the NADH oxidation waves and their integral were smaller during SD induced immediately after exposure to CO. The DC potential did not change, suggesting that CO did not affect the SD initiation mechanism but rather resulted in energy depletion during recovery from SD. This study demonstrates that even at a concentration of 1000 ppm CO interferes with the metabolic activity of the brain during repolarization of the SD-induced negativity.

Animals↗
PubMed1998

Thiopental induced cerebral protection during ischemia in gerbils.

Temporary interruption or reduction of cerebral blood flow during cerebrovascular surgery may rapidly result in ischemia or cerebral infarction. Thiopental has been shown to have cerebroprotective effects. However, the cerebroprotective dose of thiopental causes burst suppression of the EEG, thus this parameter cannot be used continuously for the detection of metabolic changes in the brain during thiopental anaesthesia. This study was performed in order to examine whether the multiparametric assembly (MPA), which measures energy metabolism CBF and mitochondrial (NADH) as well as extracellular ion concentrations (K+), can shed light on the mechanism of the cerebroprotective effects of thiopental. The MPA was placed on the brain of Mongolian gerbils and burst suppression of the ECoG was induced by thiopental. Cerebral ischemia was induced by occlusion of carotid arteries after burst suppression. Burst suppression of the ECoG was accompanied by a significant decrease in cerebral blood flow. In animals that received thiopental prior to ischemia, NADH increased to a lesser degree and extracellular potassium ion concentration increased to a lesser degree than in the control animals, indicating that thiopental affords protection of the brain under ischemic conditions due to improved energy metabolism. This study also demonstrates that the MPA can monitor changes occurring in the cerebral cortex even after the ECoG can no longer be used. Those findings have a significant value in the development of a new clinical monitoring device.

Animals↗
PubMed1998

Effect of hyperbaric oxygen therapy on survival after global cerebral ischemia in rats.

BACKGROUND: Hyperbaric oxygenation (HBO) has been considered for many years for the treatment of severe brain ischemia. However, its efficacy has not been proven. The aim of this study was to shed light on this question. METHODS: Acute global cerebral ischemia was induced in 18 rats using the four-vessel occlusion model. Regional cerebral blood flow (CBF) was determined by laser-Doppler flowmetry using a flexible 1 mm fiberoptic probe. Two stainless steel screws were used to measure the spontaneous electrical activity from the contralateral hemisphere. After ischemia monitored by laser-Doppler flowmetry and ECoG, the animals were divided into two groups: (1) control animals that breathed air at atmospheric pressure and (2) rats exposed to HBO at three atmospheres absolute pressure (ATA) for 1 hour. Survival time and rate were recorded for both groups of animals for 14 days. RESULTS: The survival rate in the study group was significantly higher (45%) than in the control group (0%). In the animals that did not survive the 14-day period, those exposed to HBO survived longer than the control animals (59.8+/-9.1 hour versus 17.9+/-2.7 hours, p < 0.05). CONCLUSION: This investigation demonstrates that HBO administered after global cerebral ischemia can increase survival in a rat stroke model.

Animals↗
PubMed1998

Multiparametric monitoring of brain oxygen balance under experimental and clinical conditions.

In order to evaluate the relationship between brain oxygen supply and demand (O2 balance) in real time, it is necessary to use a multiparametric monitoring approach. Cerebral blood flow (CBF) is a representative parameter of O2 supply. The extracellular level of K+ is a reliable indicator of O2 demand since more than 60% of the energy consumed by the brain is utilized by active transport processes. Mitochondrial NADH redox state can represent the balance between O2 supply and demand. In order to monitor the brain of experimental animals or patients, we constructed the multiparametric assembly (MPA) and the following parameters were monitored simultaneously and in real time: CBF, CBV, NADH redox state, extracellular K+, DC potential, EEG, tissue temperature and ICP. Animals were exposed to hypoxia, ischemia, hypercapnia, hyperoxia and spreading depression (SD) and the relative changes in CBF and NADH were calculated and found to be significant indicators of brain energy state. Monitoring these two parameters increases the possibility of differentiating between various pathophysiological states. Each added parameter increases the power of diagnosis and determination of the functional state of the brain. Preliminary results obtained in patients monitored in the ICU or in the OR show that the responses to hypercapnia, spreading depression or ischemia are similar to those measured in experimental animals.

Brain↗
PubMed1996

Cortical spreading depression recorded from the human brain using a multiparametric monitoring system.

The number of parameters (i.e., EEG or ICP-intracranial pressure) routinely monitored under clinical situations is limited. The brain function analyzer described in this paper enables simultaneous, continuous on-line monitoring of cerebral blood flow (CBF) and volume (CBV), intramitochondrial NADH redox state, extracellular K+ concentrations, DC potential, electrocorticography and ICP from the cerebral cortex. Brain function of 14 patients with severe head injury (GCS < or = 8), who were hospitalized in the neurosurgical or general intensive care unit was monitored using this analyzer. Leao cortical spreading depression (SD) has been reported in many experimental animals but not in the human cerebral cortex. In one of the patients monitored, spreading depression was observed. This is the first time that spontaneous repetitive cortical SD cycles have been recorded from the cerebral cortex of a patient suffering from severe head injury. Typical SD cycles appeared 4-5 h after the beginning of monitoring this patient. During the first 3-4 cycles the responses of this patient were very similar to the responses to SD recorded in normoxic experimental animals. Electrocorticography was depressed whereas extracellular K+ levels increased. The metabolic response to spreading depression was characterized by oxidation of intramitochondrial NADH concomitant to a large increase in CBF. During brain death, an ischemic depolarization, characterized by decrease in CBF and an irreversible increase in extracellular K+, was recorded.

Brain↗
PubMed1996

Effects of carbon monoxide on the brain may be mediated by nitric oxide.

Carbon monoxide (CO) is known to be a toxic molecule due to the high affinity of hemoglobin for it. However, it has recently been shown that low doses of CO may play a physiological role. The aim of the present study was to examine processes occurring in the brain during exposure to 1,000 parts per million CO that result in an increase in cerebral blood flow (CBF) but are not accompanied by changes in oxidation metabolism. This study was carried out in awake rats with the multiprobe assembly developed in this laboratory for the simultaneous continuous measurement of CBF, intramitochondrial NADH redox levels, direct current potential, and extracellular concentrations of K+, Ca2+, and H+ as well as the electrocorticogram. Exposure to 1,000 parts per million CO in air resulted in an increased CBF without any concomitant changes in any of the other metabolic or ionic parameters measured. This indicates that tissue hypoxia was not the trigger for this vasodilation. Injection of N omega-nitro-L-arginine (L-NNA), a nitric oxide synthase inhibitor, before exposure to CO effectively blocked the increase in CBF that was observed when the animal was exposed to CO without prior injection of L-NNA. Furthermore, electrocorticographic depression was observed after the combined treatment of L-NNA and CO. In conclusion, exposure to relatively low doses of CO apparently does not have a deleterious effect on oxidative metabolism because the increase in CBF after this exposure is sufficient to prevent changes in oxidative metabolism, as indicated by the fact that NADH levels remained constant. This protective autoregulatory effect may be mediated by nitric oxide.

Animals↗