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Biomedical subjects

W D Lust

Publications and source records attributed to W D Lust.

At least 55 records · Page 3Linked to original sources
PubMed1990

Impairment of metabolic recovery with increasing periods of middle cerebral artery occlusion in rats.

We examined the consequences of reflow on metabolic recovery following increasing periods of focal ischemia. The middle cerebral artery of 21 Sprague-Dawley rats was occluded with a snare ligature for 1, 2, or 6 hours followed by 5, 4, or 0 hours of reflow, respectively (seven rats in each group). All animals were injected with neutral red for visual confirmation that the affected regions were reperfused. The brains were frozen in situ, and the concentrations of adenosine triphosphate, phosphocreatine, glycogen, and lactate were determined in those areas corresponding to the normally perfused medial ipsilateral cortex, the perifocal region, and the ischemic focus. Values for the 6 hours' occlusion with no reflow group served as a control to demonstrate restoration of metabolite concentrations. In both groups with reflow, the levels of high-energy phosphates were greater than control, but this effect of reflow was primarily significant for the group with 1 hour's occlusion (p less than 0.05). The levels of glycogen and lactate provided additional evidence that the extent of metabolite restoration was graded; following 2 hours of occlusion, metabolite recovery was compromised (p less than 0.05). Our data strongly support the concept that the window of opportunity for effective treatment of focal ischemia by reperfusion is narrow (of short duration).

Adenosine Triphosphate↗
PubMed1989

Effect of several vasoactive agents on guanylate cyclase activity in isolated rat brain microvessels.

We tested the ability of the following putative vasoactive agents to stimulate guanylate cyclase activity in isolated rat cerebral microvessels: angiotensin II, arginine vasopressin, atrial natriuretic peptide, bradykinin, carbachol and thrombin; at concentrations ranging between 10(-3) and 10(-9) M. The ability of cerebral microvessels to increase their cyclic GMP generation was ascertained in the presence of sodium nitroprusside. Of all the agents tested, only atrial natriuretic peptide stimulated cyclic GMP generation in isolated rat cerebral microvessels. Such stimulation was dose-dependent, reaching its maximum at 1 microM concentration. These results are consistent with the finding of atrial natriuretic peptide receptors in brain microvessels, and suggest that this peptide has an important role in modulating the function of brain capillaries, which constitute the blood-brain barrier. If receptors for the other vasoactive agents exist in brain microvessels, their action does not seem to be mediated by cyclic GMP as a second messenger.

Angiotensin II↗
PubMed1989

Metabolism in the hamster brain during hibernation and arousal.

Hibernation was induced in hamsters by placing them in a cold room for an extended period of time, after which the hibernating state was confirmed by marked reductions in heart rate, body temperature, and the respiratory rate. The animals were either frozen intact in liquid nitrogen, or aroused and then frozen when body temperature reached 8, 12, 16, 20, 24 or 32 degrees C. A metabolite profile, including glucose-related metabolites, high-energy phosphates, gamma-aminobutyric acid (GABA) and cyclic nucleotides, was determined for both the cerebral cortex and cerebellum. In general, the metabolite changes in the two regions elicited by hypothermia were alike, although some differences were evident. The brains of hibernators were biochemically characterized by (1) a high concentration of energy reserves including glycogen, glucose, adenosine triphosphate, and P-creatine, (2) significantly elevated levels of lactate and GABA, and (3) near depletion of cyclic guanosine monophosphate with only a moderate depression of cyclic adenosine monophosphate. During arousal, the metabolites were restored to near normal values and there was little or no indication that the brain energy metabolism was compromised by the arousal process. The study provides certain insights into the metabolic adaptation of the brain to prolonged periods of profound hypothermia in a hibernating species.

Adenosine Triphosphate↗
PubMed1989

Cerebral ischemia: changes in monoamines are independent of energy metabolism.

The relationship of neurotransmitters and neuroeffectors to the energy state of the brain was examined in the gerbil model of ischemia after 5 and 15 min of bilateral common carotid artery occlusion only or with 1 hr of reperfusion. The gerbil brains were fixed by microwave irradiation and a total of 15 metabolites were measured from a single piece of tissue from either the hippocampus or the striatum. The rapid alterations in energy-related compounds and cyclic nucleotides appeared to be directly related both to the loss of oxygen and glucose during ischemia and the resupply of these nutrients during reflow. Significant reduction in the level of monoamines occurred principally during reflow, at a time when the energy-related metabolites were restored. It is proposed that the changes in monoamines were triggered by other ischemic-induced events unrelated to energy depletion.

Adenosine Triphosphate↗
PubMed1989

Role for gamma-aminobutyric acid in selective vulnerability in gerbils.

We tested the efficacy of various putative neuroprotective agents in the gerbil model of delayed neuronal death. The selective loss of anterior CA1 neurons of the hippocampus 4 days after 5 minutes of bilateral ischemia was complete in greater than 90% of the gerbils examined. We tested 11 agents for their ability to protect against neuronal loss. Only those agents that were associated with the GABAergic system exhibited protection and only when administered before the ischemic insult. The possibility that delayed neuronal death is the result of a primary defect in inhibitory neurotransmission is considered.

Animals↗
PubMed1988

Delayed hypometabolism induced by bilateral ischemia in the gerbil: regional metabolic thresholds.

The common carotid arteries were occluded in gerbils for 5 min and the metabolic rate was estimated by measuring the loss of high-energy phosphate equivalents at 4 days of reperfusion in the cerebral cortex, hippocampus, and striatum. Metabolites values at 4 days of reperfusion were not different from those of controls with the exception of glycogen, which was significantly elevated in the hippocampus. The metabolic rate, as determined by the "closed-box" method at 4 days of reflow, was decreased by more than 50% in all three regions after 5 min of bilateral ischemia. The ischemic time necessary to elicit the hypometabolic response at 4 days of reflow was 2, 3 and 4 min for the striatum, hippocampus, and cortex, respectively. It is suggested that delayed postischemic hypometabolism may be a component of an adaptive process which counteracts, to varying degrees, the deleterious effects of ischemia depending on the region examined.

Adenosine Triphosphate↗
PubMed1988

A role for gamma-aminobutyric acid (GABA) in the evolution of delayed neuronal death following ischemia.

A series of putative neuroprotective agents was tested to determine their efficacy in preventing the loss of the CA 1 neurons of the hippocampus at 4 days following 5 min of bilateral ischemia in the gerbil. Agents associated with the GABAergic system were determined to be the most effective, but only when given prior to the ischemic episode, suggesting that there was a gamma-aminobutyric acid (GABA)-related event during ischemia which triggers the delayed neuronal death of these cells. In this report, the unidirectional release of GABA and glutamate from gerbil hippocampal slices was determined under conditions mimicking anoxia and/or ischemia. Pentobarbital, the most effective of the GABAergic agents, had little or no effect on the time-dependent release of glutamate. In contrast, pentobarbital reduced in release of GABA in both anoxia and ischemia, but only after 25 to 30 min of incubation.

Animals↗
PubMed1988

Metabolic alterations in fiber layers of the CA 1 region of the gerbil hippocampus following short-term ischemia: high-energy phosphates, glucose-related metabolites, and amino acids.

The CA 1 neurons of the gerbil hippocampus die at 4 days following 5 min of bilateral ischemia. The fiber and somal layers of the CA 1 region of the gerbil hippocampus were analyzed for high-energy phosphates, glucose-related metabolites, and amino acids from 0.75 hr to 4 days of postischemia. The results were compared to those from two layers of the CA 3 region and the cerebral cortex. The metabolite changes in the fiber layers of the CA 1 region were qualitatively similar to those in the somal layer. The energy status of the tissues taken from the CA 1 region was never compromised for up to 2 days of recirculation, after which the ATP and P-creatine in the somal layer decreased to 43 and 56% of the control, respectively, whereas the average decreases in the CA 1 fiber layers were only 71 and 88% of the control, respectively. Thus, the high-energy phosphate response of the neuronal elements in the fiber layers was temporally similar to that found in the somal layer of the CA 1 region. The biphasic increases in glycogen, glucose, glucose-6-phosphate, and high-energy phosphates to values greater than the control indicated that the metabolic restoration following transient ischemia is a dynamic process which persists for up to 2 days of recirculation, even in resistant tissues. A similar pattern of delayed changes was observed in glutamate, gamma-aminobutyric acid (GABA), and glutamine, but the change in each amino acid appeared to be independent of the others despite their close metabolic relationship. The delayed decreases in GABA would favor a loss of inhibition to the CA 1 neurons and may be related to the phenomenon of delayed neuronal death.

Adenosine Triphosphate↗
PubMed1987

Visually defined zones of focal ischemia in the rat brain.

A technique to guide brain tissue sampling in experimental focal ischemia is described. This technique allows visual identification for accurate metabolic analysis of regions with variable tissue perfusion. After 2.5 hours of unilateral middle cerebral artery occlusion (MCAO) in the rat, intravenous infusion of the vital dye, neutral red (NR), identified three distinct regions: (a) an intensely stained region consisting of the entire contralateral hemisphere and the medial ipsilateral hemisphere; (b) a blanched region in the lateral ipsilateral hemisphere; and (c) a zone of intermediately stained tissue interposed between the medial and lateral ipsilateral regions. Close regional correlation between NR staining and the iodoantipyrine intensity of adjacent brain slices suggests that NR distribution is a qualitative indicator of brain perfusion. Using the NR staining pattern to guide tissue dissection for metabolite analysis of high energy phosphates (adenosine triphosphate and phosphocreatine) and glucose-related metabolites showed that the blanched region contained ischemic tissue, whereas values from the contralateral cortex resembled those of control tissue. The intermediately stained region exhibited a gradient of metabolic perturbation. Tissue near intensely stained regions resembled control tissue, and tissue near blanched regions resembled ischemic tissue. These results confirm the concept of a metabolic penumbra. When present, it occupies only the most medial area of the intermediate region at 2.5 hours after MCAO.

Adenosine Triphosphate↗
PubMed1986

Energy metabolism in delayed neuronal death of CA1 neurons of the hippocampus following transient ischemia in the gerbil.

The delayed death of CA1 neurons in the gerbil has been reported to occur at 4 days of reflow following 5 min of bilateral ischemia. Samples of the CA1 and CA3 somal region of the hippocampus, as well as of the parietal cortex, were dissected from frozen dried sections of gerbil brains frozen in situ between 1.5 and 96 hr of reflow following 5 min of bilateral ischemia and the concentrations of the adenylates, P-creatine, glucose, glycogen, and lactate were determined. The values for high-energy phosphates were restored by 1.5 hr of recirculation in all three regions and remained at or above control in the CA3 region and cortex for up to 96 hr. In contrast, the P-creatine and ATP decreased in the CA1 region at 48 and 96 hr of reflow, respectively. The total adenylates also decreased in the CA1 region at 96 h, but the normal energy charge in this area indicated that the surviving tissue was metabolically viable. A glucose overshoot was exhibited in the three regions at all time periods except 6 and 96 hr. At 6 hr of reflow, there was a transient return of glucose levels toward those of control. By 96 hr, the glucose in the CA3 region and cortex was not significantly different from control but was elevated in the CA1 region. The lactate levels were depressed from 1.5 to 12 hr of recirculation in all areas, but the decrease was significant only in the cerebral cortex. The concentration of glycogen was significantly elevated at 6 hr in all regions, then was restored by 24 to 48 hr, only to increase once again in the affected CA1 region. The results clearly indicate that metabolic perturbations persist for long periods of time after ischemic durations that are compatible with the survival of the animal but that the loss of the CA1 neurons cannot be attributed to a failure in energy metabolism.

Adenine Nucleotides↗
PubMed1986

Regional metabolite profiles in early stages of global ischemia in the gerbil.

The present experiments were designed to determine the short-term regional changes in the cyclic nucleotides, certain glucose metabolites, high-energy phosphates, gamma-aminobutyric acid (GABA), glutamate, and glutamine in the gerbil brain following bilateral ligation of the common carotid arteries. The brains of the animals were microwaved at 20, 40, 60, 90, 120, and 300 sec of ischemia and the metabolites were measured in the cerebral cortex, hippocampus, and striatum. There were significant decreases in ATP, P-creatine, and glucose within the first 20 sec of ischemia in all three regions examined, whereas the increases in phosphate and lactate, as well as the loss of glycogen, were evident only after 40 sec of ischemia. The high-energy phosphates were essentially depleted (less than 15% of control values) in all three regions by 2 min of ischemia, indicating that the energy imbalance elicited by ischemia was comparable in the three regions. In contrast, the magnitude of the changes in the cyclic nucleotides was greater in the hippocampus than in the cerebral cortex or striatum. In addition, the decrease in cyclic GMP levels at 20 sec of ischemia preceded the increases in cyclic AMP observed at 40 sec in all three regions. The use of microwave irradiation to fix the gerbil brains not only provides a more accurate assessment of the time course of the metabolite changes but also permits studies on the deeper regions of the brain than is possible with freezing techniques.

Adenosine Triphosphate↗
PubMed1986

Effects of hypoxia on rat brain metabolism: unilateral in vivo carotid infusion.

An in vivo brain perfusion technique was used to examine effects of hypoxia on cerebral cortical metabolism in barbiturate-anesthetized rats. Dulbecco's phosphate-buffered solution (PBS), or Dulbecco's PBS + 6 mM glucose, was infused into the right carotid circulation for 0 to 3 min, at a rate that reduced regional cerebral blood flow to the ipsilateral parietal lobe by more than 40% and O2 delivery by about 50%. The duration of infusion of either solution was correlated negatively with the ipsilateral parietal lobe concentrations of glucose, ATP, and phosphocreatine (PCr), and positively with parietal concentrations of lactate and cAMP. cGMP increased in relation to infusion duration of Dulbecco's PBS. Statistically significant elevations of brain lactate occurred after 1 min of infusion of Dulbecco's PBS; lactate was elevated and glucose was reduced after 2 min of infusion of either solution. Brain ATP, PCr, and glycogen concentrations decreased in relation to the elevation in brain lactate, and the [PCr]:[ATP] ratio declined. The results demonstrated that limited hypoxia stimulated cerebral glycolysis and produced a concurrent decrease in brain ATP and PCr. However, ATP was spared to a degree, at the expense of PCr.

Adenosine Triphosphate↗
PubMed1985

Isonicotinic hydrazide causes seizures in scrapie-infected hamsters with shorter latency than in control animals: a possible GABAergic defect.

Isonicotinic hydrazide, a drug that decreases the level of GABA, when injected subcutaneously in control and scrapie-infected hamsters induced tonic-clonic seizures in scrapie hamsters significantly earlier (P less than 0.0001) than in control animals. This suggests depression of the GABAergic system in scrapie-infected hamsters. To determine whether this lesion is pre or postsynaptic we measured the level of GABA, glutamate, cGMP and cAMP and the GABA-benzodiazepine receptor complex.

Animals↗
PubMed1985

Changes in brain energy metabolism and protein synthesis following transient bilateral ischemia in the gerbil.

The time course of the reduction in brain protein synthesis following transient bilateral ischemia in the gerbil was characterized and compared with changes in a number of metabolites related to brain energy metabolism. The recovery of brain protein synthesis was similar following ischemic periods of 5, 10, or 20 min; in vitro incorporation activity of brain supernatants was reduced to approximately 10% of control at 10 or 30 min recirculation, showed slight recovery at 60 min, and returned to 60% of control activity by 4 h. Protein synthesis activity was indistinguishable from control at 24 h. One minute of ischemia produced no detectable effect on protein synthesis measured after 30 min reperfusion; longer periods of ischemia resulted in progressive inhibition, with 5 min producing the maximal effect. Pentobarbital (50 mg/kg) increased by 1-2 min the threshold ischemic duration required to produce a given effect. Whereas most metabolites recovered quickly following 5 min ischemia, glycogen showed a delayed recovery comparable to that seen for protein synthesis. These results are discussed in relation to possible mechanisms for the coordinate regulation of brain energy metabolism and protein synthesis. An improved method for the fluorimetric measurement of guanine nucleotides is described.

Adenine Nucleotides↗
PubMed1984

An in vitro amino acid incorporation method for assessing the status of in vivo protein synthesis.

A quantitative in vitro amino acid incorporation assay is described which can be used to assess the status of in vivo protein synthesis. The preparation and incubation conditions employed result in constant precursor specific activity and limit amino acid incorporation to completion of nascent peptide chains. Results obtained with this method correlate well with measurements of polyribosome profiles using sucrose gradient centrifugation. The assay is easily applied to a large number of samples, and requires only a fraction of the time and tissue necessary for conventional measures of polysome aggregation. The method has been found suitable for studies of protein synthesis in mouse brain and liver, and in gerbil brain, but not in mouse kidney. Products of in vitro protein synthesis can be separated by standard electrophoretic techniques, allowing a characterization of proteins whose mRNAs are actively translated in vivo.

Amino Acids↗
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↗