Biomedical subjects

W D Lust

Publications and source records attributed to W D Lust.

At least 37 records · Page 2Linked to original sources

PubMed1994

Temporary vessel occlusion in spontaneously hypertensive and normotensive rats. Effect of single and multiple episodes on tissue metabolism and volume of infarction.

Temporary occlusion of an intracranial artery is frequently necessary in the surgical management of intracranial aneurysms, arteriovenous malformations, and tumors. While the risks of vessel damage associated with clip application have been lessened by improved design, the threat of ischemic damage remains. It is unclear whether multiple, brief periods of clip application are more or less safe than a single period of occlusion, and whether the underlying cerebrovascular status influences the outcome from either method. The effect of each of these paradigms (single: 1-hour occlusion; multiple: three 20-minute episodes separated by 10 minutes of reperfusion) on histopathological outcome was assessed in a middle cerebral artery (MCA) occlusion model using both normotensive and spontaneously hypertensive rats. The mean volume of infarction (+/- standard error of the mean) was not different between the single-ischemic (49.4 +/- 17.3 cu mm) and the multiple-ischemic (42.9 +/- 12.9 cu mm) episode groups of normotensive rats, whereas in the spontaneously hypertensive rats a significant difference existed between the volume of infarction for the single-occlusion group (126.7 +/- 18.7 cu mm) and the multiple-occlusion group (162.4 +/- 15.5 cu mm) (p < 0.05). The metabolic data obtained from spontaneously hypertensive animals did not provide an explanation for the larger infarction in that there were no significant differences between the single- and multiple-occlusion groups with respect to tissue glucose, adenosine triphosphate, or lactate levels. The results suggest that intermittent reperfusion may have different effects depending not only on the degree and duration of ischemia and reperfusion, but also on the underlying cerebrovascular status.

Adenosine Triphosphate↗

PubMed1994

Early reversal of acidosis and metabolic recovery following ischemia.

Tissue acidosis is believed to be a key element in ischemic injury of neural tissue. The goal of this study was to determine whether persisting postischemic acidosis or the extent of acidosis would affect metabolic recovery following an ischemic event. Intracellular pH (pHi), adenosine triphosphate, phosphocreatine, and lactate levels were measured in the cerebral cortex during the early stages of reperfusion, following either 5 or 10 minutes of global ischemia in both normo- and hyperglycemic gerbils. A total of 130 gerbils were injected with a solution containing 1.5 ml Neutral Red (1%) (+/- 2.5 gm/kg glucose); 30 minutes later, the gerbils were placed under halothane anesthesia, and the carotid arteries were occluded for either 5 or 10 minutes. The brains were frozen in liquid nitrogen at 0, 15, 30, 60, and 120 seconds after reperfusion; they were sectioned and the block face was photographed to determine the pHi by using Neutral Red histophotometry. At the conclusion of the ischemia, the pHi in all groups had decreased significantly from a control value of 7.05 +/- 0.03) (mean +/- standard error of the mean). In normoglycemic brains, the pHi values fell to 6.71 +/- 0.04 and 6.68 +/- 0.11 after 5 and 10 minutes of ischemia, respectively. Hyperglycemic brains were more acidotic; values fell to 6.57 +/- 0.10 and 6.52 +/- 0.24 after 5 and 10 minutes of ischemia, respectively. Lactate levels were approximately fivefold greater than those of control tissue in normoglycemic brains, while lactate levels in hyperglycemic brains were increased eightfold. The adenosine triphosphate and phosphocreatine levels were depleted at the end of ischemia in all groups. After 2 minutes of reflow activity, the pHi levels in both normo- and hyperglycemic brains were restored to those of control values in the '5-minute ischemic group, while the pHi levels remained significantly depressed in the 10-minute ischemic group. Restoration of high-energy phosphates was similar in normoglycemic brains regardless of ischemic duration, recovering to only 20% of the restoration obtained in control tissue at 2 minutes. In hyperglycemic brains, however, there was complete recovery of high-energy phosphates by 2 minutes of reflow activity following 5 minutes of ischemia. Extending the ischemic period to 10 minutes in hyperglycemic brains slowed the rate of metabolic recovery to that observed in normoglycemic brains. The results indicate that the reflow period permits the rapid restoration of pHi levels substantially before the normalization of primary energetic compounds.(ABSTRACT TRUNCATED AT 400 WORDS)

Acidosis↗

PubMed1994

Aging increases ischemia-reperfusion injury in the isolated, buffer-perfused heart.

Survival after acute myocardial infarction is decreased in elderly patients as compared with the overall adult population. Although several cardiac and noncardiac causes could contribute to the increased mortality rate, little is known regarding the relative susceptibility of aging myocardium to injury during ischemia and reperfusion. We hypothesized that the elderly heart is intrinsically more susceptible to damage than the adult heart. The recovery of isolated, buffer-perfused rat hearts from elderly animals (Fischer 344 rats, 24 months of age) was compared with that of adult hearts (6 months of age) obtained from the same strain. Hearts underwent 25 minutes of ischemia followed by 30 minutes of reperfusion. Hemodynamic recovery was decreased in elderly (n = 5) as compared with adult (n = 5) hearts, including developed pressure (% of preischemic baseline: elderly 31% +/- 4% vs adult 57% +/- 4%, p < 0.01). Elderly hearts also sustained greater tissue damage, with a markedly increased release of creatine kinase (elderly 2950 +/- 500 U vs adult 860 +/- 345 U, p < 0.01) during the 30-minute reperfusion period. The release of total protein and lactate dehydrogenase, other markers of myocyte injury, was also increased. Thus the elderly rat heart is more susceptible than the adult rat heart to ischemia-reperfusion injury. Greater injury during ischemia and reperfusion in an experimental model of aged myocardium raises the possibility of a more rapid progression of ischemic damage in elderly patients suffering acute myocardial infarction.

Aging↗

PubMed1993

The amyloid precursor protein in ischemic brain injury and chronic hypoperfusion.

We studied changes in the spatial and temporal distribution of the beta amyloid precursor protein (APP) of Alzheimer's disease (AD) in experimental ischemic brain injury. Rats with repeated reversible occlusions of one middle cerebral artery showed striking APP reactivity in astrocytic processes in perifocal regions and adjacent white matter. APP reactive dystrophic axons and neurons were also evident in the cortex and hippocampus ipsilateral to the MCA occlusion. Such changes were similarly apparent in animals subjected to partial forebrain ischemia induced by bilateral occlusion of the carotid arteries. Our studies suggest that focal ischemic insults or chronic hypoperfusion leads to increased accumulation or induction of APP in surviving cellular elements that may relate to the processes involved in beta amyloid deposition in AD.

Amyloid beta-Protein Precursor↗

PubMed1993

Regional blood-brain lactate influx.

Regional blood-to-brain lactate transport was studied in chloral hydrate anesthetized rats using the single pass, dual-label, indicator fractionation, right atrial injection method. Lactate influx was resolved into two components, a saturable, stereospecific (to the L-enantiomer) component and a non-saturable, non-stereospecific diffusional component. The saturable component was found to have a low efficiency and moderate capacity with transport affinity coefficients between 6 and 14 mM and transport maxima of 23-40 mumol/100 g/min in the various brain regions. Lactate transport was not inhibited by probenecid. The diffusional component was determined from D-lactate influx measurements and the regional linear diffusion coefficients ranged from 0.020 to 0.036 ml/g/min. At the usual levels of plasma lactate (1-1.5 mM) these two influx components were about equal. The relative contribution of the non-stereospecific diffusional component was increased at higher plasma lactate concentrations. Lactate clearance, estimated by the total apparent permeability x surface area products was between 6 and 8 ml/100 g/min.

Animals↗

PubMed1993

Accumulation of the beta amyloid precursor protein at sites of ischemic injury in rat brain.

We used various antibodies to the beta amyloid precursor protein (APP) of Alzheimer's disease to study changes in the cellular distribution of APP in experimental ischemic brain injury. In contrast to sham operated controls, rats with repeated reversible occlusions of one middle cerebral artery showed striking APP reactivity in astrocytic processes in perifocal regions and white matter tracts. Dystrophic axons and neurons with accumulated APP were also evident in the ipsilateral neocortex and hippocampus. Such changes were also apparent in rats subjected to partial forebrain ischemia by bilateral occlusion of the carotid arteries. Our studies suggest that focal ischemic insults or chronic hypoperfusion leads to increased accumulation of APP in surviving brain cells that may pertain to enhanced beta amyloid deposition in Alzheimer's disease.

Amyloid beta-Protein Precursor↗

PubMed1992

Evaluation of experimental early acute cerebral ischemia before the development of edema: use of dynamic, contrast-enhanced and diffusion-weighted MR scanning.

The ability of dynamic, contrast-enhanced, magnetic susceptibility-weighted scanning to delineate early experimental acute cerebral infarction was compared with that of heavily T2-weighted and diffusion-weighted spin echo scanning. Spontaneously hypertensive rats, which had undergone right middle cerebral artery occlusion, were studied from 15 min to 3 h post ligation on a 1.5-T clinical whole-body imager. In contrast to the diffusion- and T2-weighted spin echo scans, the dynamic, contrast-enhanced technique clearly and consistently delineated the nonperfused regions as early as 15 min post ligation.

Acute Disease↗

PubMed1992

Glutamate-induced energetic stress in hippocampal slices: evidence against NMDA and glutamate uptake as mediators.

The introduction of exogenous glutamate to normally respiring hippocampal slices produced substantial reductions in ATP, phosphocreatine (PCr) and intracellular pH (pHi) when the concentration exceeded 1 mM. These changes were not prevented by addition of MK-801 (an NMDA receptor antagonist), nor were they mimicked by NMDA or high potassium. In addition, the glutamate-induced metabolic alterations were not prevented by addition of aspartate-b-hydroxymate or sodium substitution by choline, both of which should inhibit high-affinity sodium-dependent glutamate uptake. These results suggest that glutamate alone can produce marked energetic stress in neural tissue, even when glucose and oxygen are maintained at control levels; and that the energetic stress does not appear to be specifically mediated by NMDA-induced depolarization, or by high-affinity uptake of glutamate.

Animals↗

PubMed1992

Intracellular pH in rat brain in vivo and in brain slices.

Intracellular pH can be measured quantitatively in rat brain in vivo and in vitro using spectrophotometric detection of the vital dye neutral red. This method preserves spatial information and is compatible with microhistochemistry. The intracellular pH indicated by this method is in close agreement with that indicated by 31P-NMR spectroscopy. During ischemia, intracellular acidification is correlated with tissue lactate accumulation. The spatial distribution of pH values becomes more heterogeneous as the tissue becomes more acidic. Resuscitation from total cerebral ischemia produced by cardiac arrest results in rapid intracellular realkalinization. This realkalinization is at least partially inhibited by amiloride pretreatment. Some neuronal populations, especially in the hippocampal CA1 and CA4 regions, may become more acidic during ischemia and realkalinize more slowly after reperfusion than other tissue regions. The intracellular pH of hippocampal brain slice preparations is more alkaline than expected from in vivo studies. The intracellular pH of the brain slice can be acidified to near neutrality by specific inhibitors of the sodium/hydrogen ion exchanger.

Amiloride↗

PubMed1992

[Effect of metabolic stress on the release of glutamic acid and GABA in the brain tissue of Mongolian hamsters].

The concentrations of glutamic acid and GABA were determined in the brain tissue in gerbils under conditions simulating "metabolic stress", that is ischaemia, aglycaemia and anoxia. The material for the determinations was taken from fragments of the hippocampus incubated under these conditions in artificial cerebrospinal fluid, and the concentrations of these neurotransmitters were determined by histochemical methods in vitro. The release of glutamic acid and GABA into the extracellular space increased with longer duration of the incubation in a linear fashion in all experimental groups and was most pronounced in ischaemia. In case of calcium absence in the extracellular space inhibition was observed of the release of these neurotransmitters which suggested an important role of bivalent cations in the regulation of the studied process, especially under control conditions. During anoxia and ischaemia a considerable part of the release of glutamic acid and GABA seems to be calcium-independent which may suggest presence of additional sources of release of the amino acid neurotransmitters, apart from their release from the direct pool. It is possible that these sources are activated during metabolic stress involving nerve cells.

Animals↗

PubMed1992

[Metabolic effects of experimental thermal damage of the brain in rats--cold lesion].

Experimental thermal brain injury leads to significant reduction of glucose utilization in the damaged hemisphere particularly evident in the cortex 3 days after the injury. The rate of development of these changes is not parallel with the observed damage to the blood-brain barrier, coexistent brain oedema and slight disturbances of cerebral blood flow. In a series of experiments it was possible to demonstrate significant accumulation of glucose, high-energy phosphate compounds and their metabolites in the areas of the brain near the damaged part. The authors think that this is an evidence of reduced glucose uptake by the brain resulting from reduced energy needs of the damaged brain tissue despite sufficient supply of energy-yielding substances. Since cerebral metabolism and functions are in close interrelationship reduced glucose metabolism in the damaged tissue leads to reduced activity of the cortex, which contributes to transient (or permanent) functional neurological deficits observed after cranio-cerebral trauma in humans. The knowledge and understanding of these processes regulating the development of local depression of cerebral metabolic processes may help in better results of treatment in such cases.

Adenosine Triphosphate↗

PubMed1991

The stability of proton T2 effects of oxygen-17 water in experimental cerebral ischemia.

The gerbil model of unilateral cerebral ischemia has been used to test the temporal and spatial stability of the MRI T2 effects of oxygen-17 water. Following unilateral carotid ligation, symptomatic animals were given a single large intraperitoneal injection of H2(17)O and the distribution and stability of the brain T2 effects were followed with a spin-echo sequence. In contrast to the ischemic areas, the perfused tissue shows a marked and prolonged loss in intensity with little evidence of diffusion of the T2 effect of 17O into the ischemic tissue.

Animals↗

PubMed1991

Regional changes in intracellular pH determined by neutral red histophotometry and high energy metabolites during cardiac arrest and following resuscitation in the rat.

Intracellular pH was determined by neutral red color histophotometry in cerebral tissue from rats subjected to 10 minutes of cardiac arrest and from rats that had recovered for 1 and 6 hours following 8-10 minutes of total cerebral ischemia (TIA). Tissue concentrations of ATP, lactate and glucose were measured corresponding to the pH determinations. As expected, tissue ATP was depleted while tissue lactate was markedly elevated after 10 minutes of ischemia without reflow in the cerebral cortex, striatum and hippocampus. However, both metabolites were near control following 1 and 6 hours of recovery in all three regions. Tissue glucose was not significantly different from control following 1 and 6 hours of reperfusion. During ischemia, the intracellular pH dropped to 6.5-6.7 in all three regions (p less than 0.05). But, since the initial pH of the hippocampus was 7.79 while that of the cerebral cortex and striatum was approximately 7.02, the net drop in pHi the hippocampus was greater than in the other two regions. Following 1 hour of reperfusion, a trend towards tissue alkalosis was observed in the cerebral cortex and striatum.

Adenosine Triphosphate↗

PubMed1991

Rapid metabolic failure in spontaneously hypertensive rats after middle cerebral artery ligation.

The metabolic characteristics of the penumbral region were examined in spontaneously hypertensive rats one hour after permanent middle cerebral artery occlusion. The effect of hyperglycemia on this region was examined by providing a glucose load prior to occlusion. The depressed concentrations of adenosine triphosphate and elevated levels of lactate in the penumbral region were similar to those found in the ischemic focus. The purported neuroprotective effect of hyperglycemia in the penumbral region was not reflected in an increased high-energy phosphate level in the penumbral region. The rapid deterioration of the metabolic status of this region in this strain of rat suggests that the increased consistency of infarction may come at the expense of the penumbral region, and thus this model may not be well suited for the study of metabolic changes and perhaps even therapeutic intervention.

Adenosine Triphosphate↗

PubMed1991

Effects of focal cortical freezing lesion on regional energy metabolism.

Freezing lesions have been shown to cause a depression in glucose use, particularly in cortical areas of the brain ipsilateral to the lesion, and this effect was interpreted to be caused by a depressed functional activity in these regions. The metabolic status of the affected areas has not been previously examined and could be a factor in the observed changes in local CMRglc. In frozen-cut and dried sections taken from brains 3 days after freeze lesioning, discrete pieces of the median and lateral parietal cortex, striatum, hippocampus, and hypothalamus were dissected and analyzed for ATP, P-creatine, glucose, and lactate. CMRglc measurements were also made in the same animals. The concentrations of the four metabolites were significantly increased in the lesioned hemisphere, with the most predominant effects observed in the cortical areas that exhibited the greatest depression in CMRglc. The enriched metabolite profile, particularly in the cortical areas, is consistent with the hypothesis that decreased glucose use in the traumatized brain is caused by diminished need rather than by decreased supply of energy. Because the lumped constant in the operational equation of the deoxyglucose method for determination of CMRglc is a function of brain glucose content and decreases gradually in hyperglycemia, the degree of metabolic depression in cortical areas of lesioned hemisphere probably have been somewhat overestimated in this and previous publications. However, provisionally recalculated local CMRglc in the lesioned hemisphere remain significantly lower than in the contralateral hemisphere and in the normal brain.

Adenosine Triphosphate↗

PubMed1991

Formation of free choline in brain tissue during in vitro energy deprivation.

Free choline and ATP contents were measured in Mongolian gerbil hippocampal slices (tissue) and incubation media (media) during exposure to 30 min of aglycemia, high potassium, anoxia, or ischemia. Changes in choline levels reflected the degree of energy reduction, lower ATP levels being associated with high choline (4-fold increase during exposure to high potassium and anoxia, and 11-fold increase during ischemia). Media (extracellular) choline was particularly affected and increased about twofold during relatively mild energy depletion (e.g., aglycemia), but tissue choline content was less sensitive to energy reduction. A plot of choline vs. ATP levels indicated a nonlinear correlation, and the sharp increase in choline occurred when ATP values fell to about 2.5 nmol/mg of protein. Inhibition of acetylcholine sterase by 10 microM physostigmine during ischemia did not prevent an increase in choline contents but rather enhanced them, indicating that acetylcholine hydrolysis was not the source of free choline. Formation of free choline was Ca2+ independent. These findings suggest the involvement of phospholipase D and phosphatidylcholine hydrolysis in free choline formation during energy stress. The extent of choline formation may be an indicator of the degree of membranal damage, which in turn reflects damage to the metabolic machinery of the cell.

Acetylcholinesterase↗

PubMed1990

The evolution of focal ischemic damage: a metabolic analysis.

Focal cerebral ischemia in the rat was induced by left middle cerebral artery occlusion. The area of ischemia was determined by infusion of a qualitative perfusion indicator, neutral red. The temporal evolution of alterations in regional energy metabolism was assessed by direct microquantitative histochemical analysis of high-energy phosphates, glucose, glycogen, and lactate content of the tissue. Perfusion analyses demonstrated a perifocal region of diminished, but not absent perfusion up to 6 hr after occlusion. By 24 hr, there was an abrupt demarcation between perfused and nonperfused regions. Profound metabolic alterations were seen as early as 20 min after occlusion. Although there was an area of intermediate metabolic derangement in the more medial portions of the lateral ipsilateral cortex up to 6 hr, by 24 hr there was an abrupt transition from normal to abnormal cortex. No evidence of metabolic recovery was seen in this model of permanent occlusion.

Adenosine Triphosphate↗

PubMed1990

Lactate compartmentation in hippocampal slices: evidence for a transporter.

Lactic acid accumulation has been implicated in the evolution of brain damage after ischemia. Since compartmentation of lactate may play a role in acid-base balance, lactate release from gerbil hippocampal slices was examined during a number of metabolic stresses including elevated [K+]e, ischemia, anoxia, and aglycemia. Slices were preincubated for 1 hr in artificial cerebrospinal fluid (ACSF) equilibrated with 95% O2/5% CO2 (pH 7.4 at 37 degrees C) and then transferred to tubes containing 300 microliters of test medium. The rate of lactate release in control slices was 9.64 nmol/min/mg protein and increased 2.6- and 3.2-fold in the presence of 60 mM potassium and anoxia, whereas the rate of lactate release was decreased by 50 and 25% during ischemia and aglycemia. Lactate release was temperature dependent and was only minimally influenced by removing Ca2+ or by adding 5 mM d-lactate to the ACSF. In contrast, pyruvate inhibited lactate release with an apparent Ki of 2.4 mM. The results suggest that lactate can be released from cells via a saturable and stereospecific lactate transporter with an apparent Km of 10.7 mM and Vmax of 43.7 nmol/mg protein/min. Such a relatively high-capacity transporter system can rapidly equilibrate brain lactate but is probably not involved in regulating intracellular acid-base balance.

Adenosine Triphosphate↗