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J V Passonneau

Publications and source records attributed to J V Passonneau.

At least 37 records · Page 2Linked to original sources
PubMed1984

Metabolic stability of hippocampal slice preparations during prolonged incubation.

Hippocampal slices were prepared under three conditions: (1) in medium containing glucose and oxygen at 4 degrees C; (2) as in (1), but at 37 degrees C; (3) in medium devoid of glucose and oxygen at 37 degrees C. The rates of recovery to roughly steady-state levels and through 8 h of incubation were monitored for energy metabolite levels and related parameters. In vitro stable values are compared with in situ hippocampal levels. Regardless of the conditions under which slices were prepared, metabolite levels required up to 3 h to stabilize, and these levels were maintained or improved through 8 h of incubation. Further, the maximal concentrations of metabolites were independent of the conditions of slice preparation. Total adenylates and total creatine levels reached 55% of those in vivo. Lactate decreased from the decapitation-induced high levels, but stabilized at concentrations about twice those in rapidly frozen brain. Cyclic AMP and cyclic GMP exhibited peak levels at 30 min of incubation, and cyclic GMP remained elevated for 3 h. Although all three methods of slice preparation resulted in similar metabolite profiles on incubation, the initial decreases in high energy phosphates were delayed by chilling. Most striking, the slices prepared in the absence of glucose and oxygen exhibited much smaller orthodromic evoked potentials in the dentate gyrus. The presence of glucose and oxygen during preparation of the slices appears to be critical to the electrophysiological response of the tissue.

Adenosine Triphosphate↗
PubMed1984

An in vitro model of ischemia: metabolic and electrical alterations in the hippocampal slice.

The transverse guinea pig hippocampal slice preparation was used to model the metabolic changes which occur in vivo during ischemia and recovery. Perfusing brain slices with medium devoid of glucose and oxygen elicits rapid decreases in phosphocreatine, ATP, intracellular pH, and in the evoked field potential recorded in the dentate gyrus. AMP and creatine rise during this period, while ADP and lactate levels remain unchanged. Cyclic AMP exhibits a transient increase in concentration. With the exception of ADP and lactate, these responses are very similar to those observed during in vivo ischemia. The return of glucose and oxygen to the incubation medium reverses these metabolic and electrophysiological effects and also leads to pronounced elevations in cyclic nucleotide concentrations. Metabolite concentrations approach, but do not reach, in vitro steady state levels during the first 30 min of recovery. Total adenylate and creatine steady state levels are approximately 50% of in vivo concentrations. The results suggest that, although hippocampal slices differ metabolically from in vivo tissue, they exhibit a similar pattern of metabolic responses to ischemic and reflow conditions.

Adenosine Monophosphate↗
PubMed1983

Regulation of glycogen metabolism in primary and transformed astrocytes in vitro.

Glycogen metabolism was studied in primary and Herpesvirus-transformed cultures of neonatal rat brain astrocytes. A small fraction of the glucose consumed was conserved in glycogen in both the primary and the transformed astrocytic cell cultures. After addition of culture medium containing 5.5 mM glucose, glycogen increased to maximal levels within 2.5 h, the approximate time at which half of the medium glucose was consumed, and rapidly declined thereafter in both the primary and transformed astrocytic cultures. Maximum levels of glycogen were apparently related to the cell density of the Herpesvirus-transformed cultures, but primary cultures did not show this behavior. At any given cell density, maximal levels of glycogen were dependent on the concentration of extracellular glucose. Administration of glucose caused a transient activation of glycogen synthase alpha and a rapid inactivation of glycogen phosphorylase alpha.

Animals↗
PubMed1983

Regulation of glycogenolysis in transformed astrocytes in vitro.

Cultured astrocytes, transformed by Herpesvirus, were used as a model system to study several aspects of the control of glycogenolysis. Adrenergic agonists such as norepinephrine and isoproterenol caused an immediate and dose-dependent increase in the intracellular levels of cyclic AMP. Concomitant with the initial phase of cyclic AMP increase, conversion of phosphorylase b to a and glycogenolysis were observed. The elevation of cyclic AMP, phosphorylase conversion, and glycogenolysis were simultaneously blocked by beta-adrenergic blockers, but not by alpha-adrenergic blocking agents. Repeated administration of norepinephrine caused an attenuated response in both cyclic AMP accumulation and glycogenolysis. Glycogen degradation is also partially regulated by glucose availability. In the presence of glucose, norepinephrine-induced glycogenolysis is blocked, despite elevations in cyclic AMP. The direct role of glucose is postulated, since glucose analogs mimic the effects of glucose.

2-Chloroadenosine↗
PubMed1982

Effects of excitation-contraction uncoupling by stretch and hypertonicity on metabolism and tension in single frog muscle fibers.

Metabolism and tension were examined in single fibers of the semitendinosus muscle of Rana pipiens at 15 degree C after excitation-contraction uncoupling by stretch and hypertonicity. Interrupted tetanic stimulation at 20 HZ for 150 s, of control fibers in isotonic Ringer at a rest sarcomere length (SL) of 2.3 micrometers, resulted in a steadily declining tension, stimulated glycolysis, and significantly reduced fiber phosphocreatine (PCr) and ATP concentrations. Stretching resting muscle fibers to an SL of 4.7 micrometers did not alter metabolite concentrations, but glucose-6-phosphate rose and PCr fell markedly when the stretched fibers were stimulated tetanically, although tension was absent. Immersion of untetanized fibers in 2.5 X isotonic Ringer produced a transient rise in resting tension, an increase in glucose-6-phosphate, and a significant reduction in PCr. During the transient rise in resting tension, PCr consumption per unit of tension-time integral was the same as that in fibers stimulated tetanically in isotonic Ringer. Tetanization of fibers in hypertonic solution did not further alter metabolite concentrations or produce tension. The results indicate that exposure to hypertonicity induces an increase in both tension and consumption of high-energy phosphate bonds (approximately P) in resting fibers, but stretch does not. during tetanic stimulation, stretch interferes with contraction but does not prevent activation, whereas hypertonicity inhibits activation as well as contraction.

Adenosine Triphosphate↗
PubMed1981

Light-induced changes in energy metabolites, guanine nucleotides, and guanylate cyclase within frog retinal layers.

Freeze-dried sections were prepared from retinas of frogs which were dark-adapted or exposed to varying periods of light. Samples of the discrete layers were dissected, weighed, and analyzed for energy metabolites, guanylate compounds, and the enzyme guanylate cyclase. ATP and P-creatine were measured in both dark- and light-adapted retinas. There was a gradient in ATP and P-creatine levels in dark-adapted retinas, with the lower concentrations in the photoreceptors, and increasing concentrations in the inner retina. After light adaptation, concentrations increased, an observation which supports the concept that transmitter release occurs in the dark and ceases in the light. The sum of GTP plus GDP, GDP, and cyclic GMP were analyzed in dark-adapted retinas and after exposure to 2 min or 2 h of room light. GDP was rather uniformly distributed in the retinal layers, was increased by 2 min of light in all layers but the outer nuclear, and remained elevated at 2 h in the inner retina. GTP values showed a marked localization in the outer nuclear layer, which increased after 2 min or 2 h of illumination; in all other layers GTP was decreased by light. Cyclic GMP in the dark was highest in the photoreceptor cells, decreasing to one-third after 2 min of light; there were significant increases in the outer plexiform and inner nuclear layers at this time. Cyclic GMP remained low in the photoreceptor cells even after 2 h of light, while the inner layers returned to dark values. Guanylate cyclase, like cyclic GMP, was largely confined to the photoreceptor cells and showed a maximal increase after 2 min of light exposure.

Adenosine Triphosphate↗
PubMed1981

Fatigue and metabolism of frog muscle fibers during stimulation and in response to caffeine.

Tension and metabolite concentrations were measured in single frog muscle fibers at 15 degrees C in vitro, in response to electrical stimulation or to immersion in caffeine- or potassium chloride-Ringer. Sarcomere length equaled 2.3 micrometers. Interrupted stimulation for 150 s at 20 Hz or stimulation for 7.5 min at 1 Hz was followed by at least 20 min of fatigue, evidenced by a reduced 200-ms test contraction. Fatigued fibers contracted maximally in potassium chloride- or caffeine-Ringer. They had high lactate and glucose 6-phosphate concentrations and a reduced phosphocreatine (PCr) concentration. Adenosine 5'-triphosphate (ATP) concentration was approximately normal but was markedly reduced by a caffeine contracture. A plot of PCr consumption against the tension-time integral at different stimulation frequencies (25, 35, or 50 Hz) and durations had an intercept of 25.5 nmol PCr/mg protein at time zero and a corrected slope of 0.65 nmol approximately P/mg protein per kg . s . cm-2. Prolonged fatigue is not due to energy exhaustion or to the inability of muscle fibers to consume residual ATP but probably arises from long-lasting interference in excitation-contraction coupling, which can be reversed by KCl- or caffeine-induced release of Ca2+ from intracellular stores.

Adenosine Triphosphate↗
PubMed1981

Distribution of cyclic nucleotides in layers of the cerebellum after decapitation.

The distribution of the cyclic nucleotides was examined in layers of the mouse cerebellum following decapitation. Cyclic AMP increased and cyclic GMP decreased in all three layers of the cerebellum examined. The increase in cyclic AMP in the granular layer was far greater than in either the molecular or white layers. In the cerebellum from control mice, the cyclic GMP concentration was highest in the molecular layer and lowest in the white layer. Even after decapitation, this cyclic GMP gradient in the cerebellum was maintained.

Animals↗
PubMed1979

Sparing of metabolic stress in Purkinje cells after maximal electroshock.

Experimental seizures were induced in mice by application of 50 mA for 0.2 sec via corneal electrodes. The reproducible conclusive behavior was characterized by a sequence of 2 sec of tonic flexion, 13 sec of tonic extension, and 8 sec of clonus followed by a postictal depressive stage. The animals were frozen and tissues were prepared for analysis according to Lowry and Passonneau [Lowry, O. H. & Passonneau, J. V. (1972) A Flexible System of Enzymatic Analysis (Academic, New York)]. Freeze-dried samples (1-10 ng) of pyramidal cell bodies and adjacent neuropil from the parietal cortex and of Purkinje cell bodies and adjacent neuropil from the cerebellum were analyzed for glucose, ATP, and P-creatine (0.01-0.05 pmol). There were marked decreases in these energy stores after the maximal electroshock in three of the areas examined. In the Purkinje cell bodies, however, the metabolic stress was dampened; glucose concentrations decreased, but the levels of ATP were maintained and, to a lesser extent, those of P-creatine. The results indicate that the output from the Purkinje cells is less than in the other regions examined in the excitable stages of the convulsion. The lesser energy debt probably reflects lower energy demand as well as a lower discharge intensity. The fact that Purkinje cells are spared from the metabolic stress imposed on other regions may be a partial explanation of the seizure activity. A diminished output from the Purkinje cells could be a situation that permits cortical convulsive activity.

Adenosine Triphosphate↗
PubMed1978

Metabolic correlates of fatigue and of recovery from fatigue in single frog muscle fibers.

Fatigue and recovery from fatigue were related to metabolism in single fibers of the frog semitendinosus muscle. The fibers were held at a sarcomere length of 2.3 microm in oxygenated Ringer solution at 15 degrees C and were stimulated for up to 150 s by a schedule of 10-s, 20-Hz tetanic trains that were interrupted by 1-s rest periods, after which they were rapidly frozen for biochemical analysis. Two kinds of fatigue were produced in relation to stimulus duration. A rapidly reversed fatigue occurred with stimulation for under 40 s and was evidenced by a decline in tetanic tension that could be overcome by 1 s of rest. A prolonged fatigue was caused by stimulation for 100-150 s. It was evidenced during stimulation by a fall in tetanic tension that could not be overcome by 1 s of rest, and after stimulation by a reduction, lasting for up to 82 min, in the peak tension of a 200-ms test tetanus. Fiber phosphocreatine (PCr) fell logarithmically in relation to stimulus duration, from a mean of 121 +/- 8 nmol/mg protein (SEM, n = 12) to 10% of this value after 150 s of stimulation. PCr returned to normal levels after 90-120 min of rest. Stimulation for 150 s did not significantly affect fiber glycogen and reduced fiber ATP by at most 15%. It is suggested that the prolonged fatigue caused by 100-150 s of tetanic stimulation was caused by long-lasting failure of excitation-contraction coupling, as it was not accompanied by depletion of energy stores in the form of ATP. One possibility is that H+ accumulated in fatigued fibers so as to interfere with the action of Ca2+ in the coupling process.

Adenosine Triphosphate↗