PubMed Health⌕ Search

Biomedical subjects

A Mayevsky

Publications and source records attributed to A Mayevsky.

At least 91 records · Page 5Linked to original sources
PubMed1981

The effects of age on the metabolic and electrical responses to decapitation in the awake and the anesthetized rat brain.

The effects of age on the responses of the brain to decapitation (complete ischemia) were tested in the awake and anesthetized rat. The metabolic and reflected light activities were evaluated by the use of a DC fluorometer/reflectometer (one or two hemispheres) and the electrical activity was measured by electrocorticogram. In all 81 animals used in these experiments the above-mentioned parameters were measured, to enable comparison between the age groups. The rats were divided into six age groups ranging from 2 to 120 weeks and each age group was subdivided into awake and anesthetized animals. The results can be summarized as follows. (1) The rate of energy consumption was lower in the young (2 weeks) and the old rats (120 weeks) compared to the adult rats. (2) The effect of anesthetic was more pronounced in the young and the old rats than in the adult rats. (3) The electrical activity was in good correlation with the energy availability in all animals of various ages as well as in the awake and anesthetized rats.

Aging↗
PubMed1981

Sperm Motility Analyzer (SMA), a practical tool of motility and cell concentration determinations in artificial insemination centers.

A description of a new instrument, which analyzed objectively sperm cell concentration and collective motility of a fresh semen sample of bull or ram, is reported. A display read-out of sperm cell concentration for an aliquot of the undiluted semen sample in the range from 200 x 10(6) to 4000 x 10(6) cell/ml with an accuracy of +/- 5% is shown immediately by optical density units. A significant correlation coefficient (0.918, p < 0.01) was obtained between these units and cell concentrations, as determined in four A.I. centers in the U.S. and Canada. The intensity of the sperm collective motility is expressed as an objective index (SMI) which was significantly correlated to the fraction of the live motile cells in the semen sample. The SMI values were corrected for a possible error originating from the difference in sperm cell concentration by an empirical equation. Due to the accuracy, repeatability and objectivity of evaluating the semen quality and also the simplicity of operation, as well as the possibility of utilizing the measured semen sample for further processing, the Sperm Motility Analyzer (SMA) seems suitable as a standard tool for semen quality control in the A.I. centers.

Journal Article↗
PubMed1981

Ion transport and energy metabolism in brain.

The kinetics of extracellular K+ activity was compared to the availability of energy in the cortex of rats and gerbils exposed to anoxia, hypoxia, spreading depression, and ischemia. A combined K+/DC surface electrode was used alone or together with a fiber optic light guide in various experiments. All experiments were done on slightly anesthetized animals that were practically awake. The results can be summarized in the following conclusions: (1) Under conditions such as hypoxia or ischemia, K+0 showed a two-phase efflux kinetics, and a transition or critical point was reached where the response proceeds at a higher rate. This critical point was in the range of 10-16 mEq/1 potassium. (2) Availability of oxygen is necessary but not sufficient for a full rate of recovery from a long-term oxygen-deprivation insult. (3) There is an energy debt or energy-transduction bottleneck formed during a prolonged O2 insufficiency. This debt is reversed slowly during the recovery phase even when full restitution of O2 supply and blood flow has occurred.

Animals↗
PubMed1981

An experimental approach for evaluation of the O2 balance in local myocardial regions in vivo.

Quantitative evaluation of myocardial oxygen balance can be accomplished by measurement of oxygen supply, demand, and intracellular oxygen concentration. Experimentally, these parameters are often related to coronary blood flow, cardiac contractility, and mitochondrial NADH redox level, respectively. Methods were developed to measure these three parameters in a local region on the myocardial surface in open-chest dogs. Local coronary blood supply was measured with the aid of a small surface thermistor, and cardiac work with a miniature strain gauge arch. NADH oxidation--reduction state was recorded using surface fluorometry through a fibre optic light guide. Transient anoxia produced by nitrogen breathing caused a rapid but reversible elevation in NADH levels, which was not always accompanied by a concomitant change in contractile force. Elevation of heart rate resulted in a rise in intramitochondrial NADH followed by an increase in coronary flow. In spite of the increased flow, NADH levels remained elevated, indicating a change in the O2 balance; this may indicate that autoregulation does not necessarily result in total compensation.

Animals↗
PubMed1981

Effects of hyperbaric oxygenation on spermatozoan motility driven by mitochondrial respiration.

The effects of hyperbaric oxygen (HPO) on ram sperm motility driven by mitochondrial respiration are described. Sperm motility was assessed by a multichannel optical objective technique (Reflectospermiography). Motility was simultaneously measured from four semen sample at various pH levels in room air atmosphere and compared with four other samples exposed to various high oxygen (100%) levels 1, 3, 5, and 7 atmospheres absolute (ATA). Two main effects were observed under HPO oxygen: 1) shortening of motility durations, and 2) abolishment of motility regulation by pH. These effects were found to be attributed to the hyperoxic conditions. Above 3 ATA the effects of HPO with regard to the above-described parameters were considered toxic. Below this pressure level the effect of HPO was found to be moderate. The exposure of sperm cells to HPO (7 ATA) did not cause morphological alterations. Also, exposure of seminal plasma to HPO (7 ATA) for 150 min did not cause any toxic effects when added to washed spermatozoa. The ram semen preparation seems to provide a useful model for studying the mechanisms underlying HPO effects.

Animals↗
PubMed1981

A fluorometric-reflectometric technique for simultaneous measurement of pH and motility in ram semen.

An optical technique for simultaneous assessment of pH and motility in ram semen was described. Motility was evaluated by the measurement of changes in intensity of reflected light from semen samples illuminated with 366 nm light. pH was measured by using a pH-sensitive fluorescent indicator (umbelliferone). From the changes in fluorescence intensity (450 nm) as a function of the pH of the semen, a calibration curve was constructed. The relationship between pH changes and motility in various metabolic conditions were described. Different kinetics for pH changes occurred when sperm motility was driven by both mitochondrial respiration and fructolysis or by either one of them. An analysis of the fluorescence signal from extracellular or cellular fractions of semen suggested that the pH measurement reflected extracellular pH.

Animals↗
PubMed1981

Effect of coronary vasodilation produced by hypopnea upon regional myocardial oxygen balance.

An attempt was made to differentiate between autoregulatory coronary vasodilation and changes in vasomotor tone produced by factors extrinsic to the heart. this was done by investigating the relation between local cardiac force and local coronary blood supply. Intracellular NADH redox levels were also measured in order to further elucidate the oxygen balance under various experimental conditions. In anaesthetized open-chest dogs, local blood supply was estimated with the aid of a thermistor probe, and the oxidation-reduction state of mitochondrial pyridine nucleotide was measured by a surface fluorometric technique. Local myocardial contractile force, as well as blood pressure and ECG were recorded simultaneously with the above parameters. The heart was paced at frequencies from 60/min to 300/min with an electronic stimulator, under both normoxic and hypopneic conditions. It was found that elevation of heart rate caused a progressive increase in local blood flow during both normal and hypopneic ventilation. The absolute flow values during hypopnea were approximately double those during normoxia. Heart rates above 120/min or 150/min resulted in a progressive increase in NADH fluorescence. This response to elevated heart rate was less prominent or absent during hypopnea. Contractile force during hypopnea was greater at elevated heart rates than during normal breathing. Data are brought which suggest that whereas vasodilation following increased heart rate is probably due to an autoregulatory mechanism, the marked vasodilatatory effect of hypopnea is related to elevated arterial CO2 levels. It is suggested that hypercapnia markedly stimulates extrinsic coronary vasodilation thereby supplying enough oxygen to maintain contractility even at very high heart rates. Moreover, intracellular O2 concentration (mitochondrial NADH level) is maintained at a normal level despite the greatly increased demand.

Animals↗
PubMed1980

Metabolic changes induced in rat hippocampal slices by norepinephrine.

The oxidative metabolic activity of restricted regions of hippocampal slices was assessed by a continuous measurement of the fluorescence of intramitochondrial nicotinamide-adenine dinucleotide (NADH). A large increase in NADH fluorescence was triggered by substituting the oxygen supply to the slice by nitrogen gas. A large and transient increase in NADH fluorescence was also produced by superfusion of the the slice with a high (50 mM) potassium-containing medium. Addition of norepinephrine (NE) to the superfusion medium caused a propranolol-inhibited increase in NADH fluorescence. Furthermore, ouabain, which inhibits the Na-K pump, blocked the effects of NE. An analog of cyclic adenosine monophosphate (cAMP), 8-bromo cAMP, mimicked the effect of NE. Finally, effects of NE could still be produced in a kainic acid-treated hippocampus, where most neurons were previously destroyed by the drug. It is suggested that NE activates a Na-K-ATPase, that this effect might be mediated by cAMP, and that these interrelations may underly the physiological action of NE in the brain.

Animals↗
PubMed1980

The interrelation between brain PO2 and NADH oxidation-reduction state in the gerbil.

The present investigation was aimed at studying the interrelation between hemodynamic, metabolic and oxygen tension in the brain of the gerbil exposed to various physiological and pathological conditions in the awake and anesthetized states. The hemodynamic and metabolic activities were evaluated by the DC fluorometer/reflectometer and were correlated to the pO2 values obtained by a surface electrode. When the awake brain was exposed to spreading depression (SD), a typical oxidation cycle of the NADH was recorded concomitant with a decrease cycle of the pO2. Under anesthetic effect the same dip in pO2 response was found but the NADH showed a "reduction cycle." The pO2 values were in a very good correlation with the changes in the reflectance trace, namely, the pO2 was a good indicator of the vasoconstriction-vasodilatation responses under various conditions. The same model was used under hypoxic and ischemic conditions, as well as under the effects of anesthetics.

Anesthesia, General↗
PubMed1980

The interrelation between brain oxidative metabolism and extracellular potassium in the unanesthetized gerbil.

The unanesthetized gerbil model was used to study the interrelation between metabolic, electrical and ionic activities in the brain. A combined K+DC surface electrode with a fiber optic light guide was implanted above the parietal cortex and cemented to the skull. The subjects were exposed to various pathological and physiological conditions such as anoxia, hypoxia, spreading cortical depression, and ischemia. During anoxia a leakage of cellular K+e was detected simultaneously with an increased level of NADH. The recovery phase in a few animals was followed by a spreading depression phenomenon. Exposing the brain to spreading depression led to a typical oxidation cycle of NADH, and the shape of this cycle was affected by hypoxia. Unilateral carotid artery ligation induced localized ischemia that affected cellular and K+e responses to spreading depression. Bilateral carotid artery occlusion increased NADH concentration to its maximum level; as a result, K+e also accumulated. Complete restoration of NADH and K+e to normoxic levels occurred after a few minutes, depending on the duration of the occlusion.

Animals↗
PubMed1980

High pressure oxygenation in unanesthetized brain: mitochondrial activity, pyridinenucleotide redox state, and electrical activity.

The effects of hyperbaric oxygenation (HPO) on mitochondrial activity, NADH oxidation-reduction state, and electrical activity were studied in the unanesthetized rat brain. Mitochondrial activity was measured in vitro after isolation of the mitochondria from brains exposed to HPO in mitochondria from brains exposed to HPO in vivo for various time intervals. The results showed that exposure of the brain to HPO in vivo decreased state 3 respiration of the mitochondria within 5-10 min of exposure. The level of respiration remained low until the final step of exposure. Despite this low respiration rate in vitro, the brain from which the mitochondria were isolated showed an oxidized state that, in comparison to the normoxic level of NADH, suggested a higher rate of respiration had occurred as a response to the convulsion appearing in vivo.

Animals↗
PubMed1980

Flying spot studies of brain flavoproteins in the gerbil.

The flying spot fluorometer/reflectometer for flavoprotein (Fp) was used in the present study in order to evaluate energy metabolism in the anesthetized gerbil brain. This model was exposed to various conditions, such as anoxia, spreading depression, and ischemia. The fluorescence and reflected light were analyzed in terms of intensities of histograms, and the fractional changes were calculated and compared between the metabolic states. The results show that under various conditions, the fluorescence of Fp changed together with the reflectance change, and the net mitochondrial change was not always clear. The results presented in the study are in good agreement with the previously-published results.

Animals↗
PubMed1980

A new optical technique for evaluating collective motility of ram and bull ejaculated spermatozoa.

A new, non-destructive, objective technique for measuring collective motility of highly-concentrated ram and bull semen is described. The principle is based on changes in the reflected light scattered by motile spermatozoa. These changes can be recorded as a continuous analog wave pattern (Reflectospermiogram-RSG) and are correlated to the intensity of the turbulent motility as evaluated subjectively with an ordinary light microscope. Ram spermatozoa have, after ejaculation, a typical motility pattern, i.e., high, stable activity for about 20 min, then a period during which the motility decreases at a constant rate, and finally, a period with a low but rather constant activity. The usefulness of the technique has been demonstrated in various types of experiments.

Animals↗
PubMed1980

A multi-channel system for the measurement of spermatozoan collective motility.

A new multi-channel optical system for objective evaluation of sperm motility is described. The principle of the technique is based on the measurement of changes in the intensity of light scattered from semen samples thermoregulated at 38 degrees C. These changes were recorded continuously as analog waves (Reflectospermiogram--RSG). Changes in the intensity of sperm motility as a function of time from ejaculation were simultaneously measured in 8 equal semen samples from single ejaculate. By analyzing the variations in results, the sensitivity of the technique was defined. In order to demonstrate the use of the technique, the effect of various concentrations of ethanol on sperm motility has been described. The exposure of sperm cells to 366 nm light used in the system did not alter their ultrastructure, as was observed by electron microscopy. This objective, relatively easy to perform and highly informative technique can be of great value in research studies.

Animals↗
PubMed1980

The effect of pH on ram sperm collective motility driven by mitochondrial respiration.

Ram sperm cells treated with 0.02 M 2-deoxy-D-glucose exhibit collective motility which is driven only by mitochondrial respiration. This motility was measured, by means of multichannel optical objective technique, under various [H+] concentrations (pH range 5.6-7.2) buffered by 0.125 M phosphate buffers. Semen was divided into 8 aliquots and motility was monitored simultaneously for intensity and duration within 10 min of ejaculation until its complete cessation. The optimal pH range found for the two above-mentioned parameters was in the range of 6.0-6.5. A certain characteristic of the pattern of sperm motility intensity (an oscillations phenomenon) was similarly related to pH. It is suggested that the mechanisms underlying the relationship between pH and motility are rather metabolic. Concerning the results, some practical implications are introduced.

Animals↗
PubMed1980

Factors affecting the development of hyperbaric oxygen toxicity in the awake rat brain.

Hyperbaric oxygen toxicity (HPO), under various environmental and physiological conditions, was identified by measuring the electrical, hemodynamic, and metabolic activity of the awake brain in rats. The electrical activity was evaluated by the electrocorticogram; the hemodynamic and metabolic activity were measured by use of the surface fluorometry/reflectometry technique. The oxidation-reduction state of NADH (metabolic activity) was measured by using the quartz fiber-optic system to excite the tissue and transmit the fluorescence-emitted light from the brain. The hemodynamic responses were evaluated from the reflectance signal. In three sets of experiments we tested the effects of pressure level, age, and protection agents (pentobarbital and diazepam) on the various parameters measured from the brain. The results can be summarized as follows. 1) The effect of the pressure level of the toxicity process is significant; the higher the pressure, the greater the toxicity. 2) The 60-psi level of pressure is a turning point in the toxicity process, and the kinetic of the process is different below and above this point. 3) The 14-day-old rats showed resistance to the HPO exposure as compared to the older aged rats. 4) The pentobarbital and diazepam protect against the toxicity at 60 and 90 psi, as evaluated by various parameters measured.

Aging↗