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K A Hossmann

Publications and source records attributed to K A Hossmann.

At least 55 records · Page 3Linked to original sources
PubMed1998

Effect of mild hypothermia during and after transient in vitro ischemia on metabolic disturbances in hippocampal slices at different stages of development.

In the present study the neuroprotective effect of mild hypothermia (decrease of temperature from 37 degrees C to 33 degrees C) during and after transient ischemia in brain tissue at different stages of development was tested in vitro by measuring energy metabolism, glutamate release and protein biosynthesis rate (PSR) in hippocampal slices. Slices were taken from immature (E40) and mature (E60) guinea pig fetuses and adult guinea pigs. The slices were exposed to ischemia-like conditions (oxygen/glucose deprivation, OGD) for periods of between 10 to 40 min followed by a 2-h or 12-h recovery phase. During OGD, mild hypothermia slowed down the depletion of energy stores only in slices from immature fetuses, but had no effect on slices prepared from mature fetuses and adult animals. Hypothermia also reduced glutamate release significantly during oxygen/glucose deprivation. Lowering temperature to 33 degrees C had no effect on energy metabolism and only a minor effect on PSR of slices from mature fetuses and adult animals subjected to 2 h of recovery. However, 12 h after OGD PSR was markedly improved by mild hypothermia in slices from mature animals and in slices from adults that had been exposed to OGD for only 20 or 30 min. The inhibition of PSR was more severe in the slices from adults than in those from mature fetuses subjected to the same duration of OGD. Age- and temperature-related differences in glutamate release during OGD did not fully agree with corresponding disparities in the values for PSR obtained 12 h after OGD. These results indicate that the neuroprotective effect of mild hypothermia was not mediated by a temperature-dependent retardation of the depletion of energy stores during OGD. Age-related disparities in the vulnerability of the brain to ischemia and the neuroprotective efficiency of mild hypothermia appear to be only partially reflected by the varying levels of glutamate release during ischemia but best reflected by the extent of PSR inhibition. It is concluded that mild hypothermia may be a suitable therapeutical intervention for the suppression of hypoxic-ischemic cell damage during birth.

Adenine↗
PubMed1998

Differential expression of c-fos and hsp72 mRNA in focal cerebral ischemia of mice.

The heterogeneity of c-fos and hsp72 mRNA expression during focal ischemia was studied in mice by combining in situ hybridization with metabolic imaging. Focal ischemia was produced by middle cerebral artery occlusion for 3 h. The infarct core and the penumbra were differentiated by regional ATP and cerebral protein synthesis (CPS) imaging. hsp72 mRNA expression was restricted to the ischemic penumbra, as defined by the dissociation between preserved ATP and suppressed CPS. c-fos mRNA was expressed not only in the penumbra but also in the peri-ischemic normal brain tissue in which both ATP and CPS were preserved. These data demonstrate a highly selective differential expression of immediate-early and stress-related genes in the peri-infarct surrounding which is explained by different mechanisms of gene induction.

Adenosine Triphosphate↗
PubMed1998

Functional MRI of somatosensory activation in rat: effect of hypercapnic up-regulation on perfusion- and BOLD-imaging.

Functional activation of somatosensory cortex was studied in alpha-chloralose anesthetized rats by functional magnetic resonance imaging (fMRI), using both perfusion-weighted and T2*-weighted (blood oxygenation level dependent, BOLD) imaging. The sensitivity of functional activation was altered by ventilating animals for 3 minutes with 6% CO2. Before hypercapnic conditioning, electrical stimulation of the left forepaw at a frequency of 3 Hz led to an increase of signal intensity (relative to the unstimulated baseline condition) in the right somatosensory cortex by 6+/-2% (means+/-SD) in T2*-weighted images and by 45%+/-48% in perfusion-weighted images. After hypercapnic conditioning the signal intensity increase in perfusion-weighted images doubled to 91%+/-62% (P=0.034), whereas that of T2*-weighted images only marginally increased to 7+/-4% (not significant). This different behavior in both imaging modalities is interpreted as evidence for an increased flow response in combination with a higher oxygen extraction. Thus, the fMRI data reflect hypercapnia-induced resetting of the functional-metabolic coupling of the tissue during activation.

Animals↗
PubMed1998

Recovery of the rodent brain after cardiac arrest: a functional MRI study.

Recovery of the cerebral cortex after 10 min of cardiac arrest was studied in rat using noninvasive MRI techniques. The apparent diffusion coefficient (ADC) of brain water was imaged to document reversal of the metabolic impairment. Perfusion-weighted imaging and blood oxygen level dependent (BOLD) imaging were performed to assess functional recovery. To this purpose, rats were anesthetized with alpha-chloralose, and somatosensory cortex was activated by electrical stimulation of the contralateral forepaw. In sham-operated controls, cortical ADC was 862 +/- 10 microm2/s, and stimulation of forepaw led to a focal increase of signal intensity in somatosensory cortex by 71 +/- 22% in perfusion-weighted images and by 6 +/- 1% in BOLD images. One hour after successful resuscitation following 10 min of cardiac arrest, ADC did not differ from control but functional activation was completely suppressed. After 3 hours of reperfusion, functional activity began to reappear but the recovery of the BOLD signal progressed faster than that of the perfusion-weighted signal. The differences in the recovery of ADC, BOLD, and perfusion imaging are related to differences between metabolic and functional recovery on one hand and between blood flow and oxygen extraction on the other. The combination of these MRI methods thus provides detailed qualitative information about the progression of brain recovery after transient circulatory arrest.

Animals↗
PubMed1998

Temporal and regional changes during focal ischemia in rat brain studied by proton spectroscopic imaging and quantitative diffusion NMR imaging.

The early development of focal ischemia after permanent occlusion of the right middle cerebral artery (MCA) was studied in six rats using interleaved measurements by diffusion-weighted NMR imaging (DWI) of water and two variants of proton spectroscopic imaging (SI), multiecho SI (TE: 136, 272, 408 ms) and short TE SI (TE: 20 ms). Measurements on a 4.7-T NMR imaging system were performed between the control phase and approximately 6 h postocclusion. In the center of the ischemic lesion of all rats, the apparent diffusion coefficient (ADC) decreased rapidly to 84.4 +/- 4.2% (mean +/- SD) of the control values approximately 2 min postocclusion. Approximately 6 h postocclusion, the ADC was reduced to 67.1 +/- 5.9%. In contrast, large differences between the animals were observed for the temporal increase of lactate (Lac) in the ipsilateral hemisphere. The maximum Lac signal was reached in four rats after 0.5-1.5 h, and in two rats was not reached even after 6 h postocclusion. Six h postocclusion, SI spectra measured at a TE of 136 ms revealed a decrease in the CH3 signal of N-acetylaspartate (NAA) to 67 +/- 13% of the control values. Differences were observed between the spatial regions of decreased NAA and increased Lac. In the lesions, a T2 relaxation time of Lac of 292 +/- 40 ms, considering a J-coupling constant of 6.9 Hz, was measured. Furthermore, a prolongation of the T2 of the CH3 signal of creatine/phosphocreatine (Cr/PCr) was observed in the lesion, from 163 +/- 22 ms during control to 211 +/- 41 ms approximately 6 h postocclusion. The experiments proved that DWI and proton SI are valuable tools to provide complementary information on processes associated with brain infarcts.

Animals↗
PubMed1998

Induction of protein inhibitor of neuronal nitric oxide synthase/cytoplasmic dynein light chain following cerebral ischemia.

Administration of inhibitors of neuronal nitric oxide synthase or deletion of the encoding gene in rodents provided evidence that neuronal nitric oxide synthase activity may contribute to neuronal cell death following global and focal cerebral ischemia. In the present study, we investigated by in situ hybridization the expression of an endogenous inhibitor of neuronal nitric oxide synthase activity, designated protein inhibitor of neuronal nitric oxide synthase and homologous to cytoplasmic dynein light chain, in the post-ischemic rat brain. Following global ischemia induced by cardiac arrest, messenger RNA expression of protein inhibitor of neuronal nitric oxide synthase was rapidly induced in pyramidal neurons of the hippocampal CA3 region and granule cell of the dentate gyrus which are resistant to ischemic damage. In vulnerable CA1 pyramidal neurons however, protein inhibitor of neuronal nitric oxide synthase expression remained at basal level after global ischemia and was associated with an increase in nicotinamide adenine dinucleotide phosphate-diaphorase activity and subsequent DNA fragmentation indicating ischemia-mediated neuronal cell death. Following focal cerebral ischemia induced by permanent occlusion of the middle cerebral artery, transcripts of protein inhibitor of neuronal nitric oxide synthase progressively accumulated in cortical neurons bordering the infarct area. After transient middle cerebral artery occlusion however, messenger RNA levels of protein inhibitor of neuronal nitric oxide synthase increased in the reperfused neocortex. Our findings indicate that cerebral ischemia leads to an increase in neuronal expression of protein inhibitor of neuronal nitric oxide synthase in brain regions where sustained or "uncoupled" nitric oxide synthase activity may be detrimental to neurons. Lack of post-ischemic induction of protein inhibitor of neuronal nitric oxide synthase in CA1 pyramidal neurons may result in high nitric oxide synthase activity after global ischemia and could contribute to delayed neuronal cell death.

Animals↗
PubMed1998

A reproducible model of middle cerebral artery occlusion in mice: hemodynamic, biochemical, and magnetic resonance imaging.

A reproducible model of thread occlusion of the middle cerebral artery (MCA) was established in C57 Black/6J mice by matching the diameter of the thread to the weight of the animals. For this purpose, threads of different diameter (80 to 260 microns) were inserted into the MCA of animals of different weights (18 to 33 g), and the success of vascular occlusion was evaluated by imaging the ischemic territory on serial brain sections with carbon black. Successful occlusion of the MCA resulted in a linear relationship between body weight and thread diameter (r = 0.46, P < 0.01), allowing precise selection of the appropriate thread size. Laser-Doppler measurements of CBF, neurological scoring, and 2,3,5-triphenyltetrazolium chloride staining confirmed that matching of animal weight and suture diameter produced consistent cerebral infarction. Three hours after MCA occlusion, imaging of ATP, tissue pH, and cerebral protein synthesis allowed differentiation between the central infarct core, in which ATP was depleted, and a peripheral penumbra with reduced protein synthesis and tissue acidosis but preserved ATP content. Perfusion deficits and ischemic tissue alterations could also be detected by perfusion- and diffusion-weighted magnetic resonance imaging, demonstrating the feasibility of dynamic evaluations of infarct evolution. The use of multiparametric imaging techniques in this improved MCA occlusion model opens the way for advanced pathophysiological studies of stroke in gene-manipulated animals.

Adenosine Triphosphate↗
PubMed1998

Reperfusion after thrombolytic therapy of embolic stroke in the rat: magnetic resonance and biochemical imaging.

The effect of thrombolytic therapy was studied in rats submitted to thromboembolic stroke by intracarotid injection of autologous blood clots. Thrombolysis was initiated after 15 minutes with an intracarotid infusion of recombinant tissue-type activator (10 mg/kg body weight). Reperfusion was monitored for 3 hours using serial perfusion- and diffusion magnetic resonance imaging, and the outcome of treatment was quantified by pictorial measurements of ATP, tissue pH, and blood flow. In untreated animals, clot embolism resulted in an immediate decrease in blood flow and a sharp decrease in the apparent diffusion coefficient (ADC) that persisted throughout the observation period. Thrombolysis successfully recanalized the embolized middle cerebral artery origin and led to gradual improvement of blood flow and a slowly progressing reversal of ADC changes in the periphery of the ischemic territory, but only to transient and partial improvement in the center. Three hours after initiation of thrombolysis, the tissue volume with ADC values less than 80% of control was 39 +/- 22% as compared to 61 +/- 20% of ipsilateral hemisphere in untreated animals (means +/- SD, P = .03) and the volume of ATP-depleted brain tissue was 25 +/- 31% as compared to 46 +/- 29% in untreated animals. Recovery of ischemic brain injury after thromboembolism is incomplete even when therapy is started as early as 15 minutes after clot embolism. Possible explanations for our findings include downstream displacement of clot material, microembolism of the vascular periphery, and events associated with reperfusion injury.

Adenosine Triphosphate↗
PubMed1998

Neuronal stress response and neuronal cell damage after cardiocirculatory arrest in rats.

Cardiocirculatory arrest is the most common clinical cause of global cerebral ischemia. We studied neuronal cell damage and neuronal stress response after cardiocirculatory arrest and subsequent cardiopulmonary resuscitation in rats. The temporospatial cellular reactions were assessed by terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end-labeling (TUNEL) staining of DNA fragments, in situ hybridization (heat shock protein hsp70; immediate early genes c-fos and c-jun), and immunocytochemical (HSP70; and myeloperoxidase, specific marker of polymorphonuclear leukocytes [PMNL]) techniques. Cardiac arrest of 10 minutes' duration was induced in mechanically ventilated male Sprague-Dawley rats anesthetized with nitrous oxide and halothane. After cardiopulmonary resuscitation, animals were allowed to reperfuse spontaneously for 6 hours, 24 hours, 3 days, and 7 days (n = 6 per group). Five sham-operated animals were controls. The TUNEL staining revealed an early onset degeneration in the thalamic reticular nucleus (TRN) at 6 hours that peaked at 3 days. In contrast, degeneration was delayed in the hippocampal CA1 sector, showing an onset at 3 days and a further increase in the number of TUNEL-positive cells at 7 days. A minor portion of TUNEL-positive nuclei in the CA1 sector showed condensed chromatin and apoptotic bodies, whereas all nuclei in the TRN revealed more diffuse staining. After 6 hours of reperfusion, levels of mRNA for hsp70 and c-jun were elevated in circumscribed areas of cortex, in all hippocampal areas, and in most nuclei of thalamus, but not in the TRN. After 24 hours, a strong expression of mRNA for hsp70 and c-jun could be observed in the second layer of the cortex and in hippocampal CA1 sector; hsp70 also was observed in hippocampal CA3 sector. Some animals showed expression of hsp70 and c-jun in the dentate gyrus. After 3 days, hsp70 and c-jun were detected mainly in the CA1 sector of hippocampus. At 7 days, mRNA for both returned to control values. Therefore, delayed cell degeneration in the CA1 sector corresponds to a prolonged expression of hsp70 and c-jun in this area. In situ hybridization studies for c-fos revealed a strong signal in CA3 and dentate gyrus and a less prominent signal in TRN at 6 hours. At 24 hours, CA4 and amygdalae were positive, whereas at 3 and 7 days, the signal reached control levels; no prolonged or secondary expression was observed in the CA1 sector. Immunohistochemical study confirmed translation of HSP70 in various areas corresponding to the detection of mRNA, including the CA1 sector. The number of PMNL increased significantly at 6 hours and 7 days after cardiac arrest; PMNL were distributed disseminately and were not regionally associated with neuronal cell damage. The current data support the view that CA1 neurons might undergo an apoptosis-associated death after cardiac arrest, but PMNL are not directly involved in this process. The marked differences in the time course and the characteristics of TUNEL staining and the neuronal stress response in CA1 sector and TRN point to different mechanisms of neuronal injury in the two selectively vulnerable areas.

Animals↗
PubMed1998

Attenuated c-fos mRNA induction after middle cerebral artery occlusion in CREB knockout mice does not modulate focal ischemic injury.

To elucidate the mechanism of ischemia-induced signal transduction in vivo, we investigated the effect of the targeted disruption of the alpha and delta isoforms of the cAMP-responsive element-binding protein (CREB) on c-fos and heatshock protein (hsp) 72 gene induction. Permanent focal ischemia was induced by occlusion of the middle cerebral artery of the CREB mutant mice (CREB(-/-), n = 5) and the wild-type mice (n = 6). Three hours after onset of ischemia, the neurologic score was assessed and pictorial measurements of ATP and cerebral protein synthesis (CPS) were carried out to differentiate between the ischemic core (where ATP is depleted), the ischemic penumbra (where ATP is preserved but CPS is inhibited), and the intact tissue (where both ATP and CPS are preserved). There were no significant differences in neurologic score or in ATP, pH, and CPS between the two groups, suggesting that the sensitivity of both strains to ischemia is the same. Targeted disruption of the CREB gene significantly attenuated c-fos gene induction in the periischemic ipsilateral hemisphere but had no effect on either c-fos or hsp72 mRNA expression in the penumbra. The observations demonstrate that CREB expression, despite its differential effect on c-fos, does not modulate acute focal ischemic injury.

Adenosine Triphosphate↗
PubMed1997

Expression of nuclear redox factor ref-1 in the rat hippocampus following global ischemia induced by cardiac arrest.

The Ref-1 protein is a bifunctional nuclear enzyme involved in repair of DNA lesions and in redox regulation of DNA-binding activity of AP-1 family members, such as Fos and Jun transcription factors. In the present study, we demonstrate by in situ hybridization that transient global ischemia induced by cardiac arrest activates ref-1 mRNA expression in the granular cells of the rat dentate gyrus after 6 h and in CA1 pyramidal neurons of the hippocampus proper after 24 h, respectively. Immunohistochemical analysis revealed nuclear accumulation of Ref-1 protein in granular cells of the ischemia-resistant dentate gyrus, whereas Ref-1 protein expression progressively decreased in vulnerable CA1 neurons of the post-ischemic hippocampus from 24 h onwards. At the same time point, intense nuclear c-Jun immunoreactivity was observed in both neuronal cell populations. Our data suggest that oxidative stress induced by ischemia-reperfusion may increase neuronal ref-1 expression. However, inability of ref-1 mRNA translation and nuclear translocation of encoded protein in CA1 pyramidal neurons may inhibit repair of oxidative DNA damage or cellular adaptive responses leading to delayed neuronal cell death.

Animals↗
PubMed1997

Improved model of thromboembolic stroke and rt-PA induced reperfusion in the rat.

We report the technical details and validation of an improved rat model for thromboembolic stroke and rt-PA induced reperfusion, which closely resembles clinical embolic stroke. The middle cerebral artery (MCA) was proximally occluded by injection of twelve medium sized (1.5 x 0.35 mm), fibrin-rich autologous blood clots. On inspection, densely packed clot material was found at the ipsilateral MCA origin in all untreated animals. Autoradiographic rCBF measurements showed severe ischemic deficit throughout the ipsilateral MCA territory in untreated animals. The volume in which flow values fell below 30 ml/100 g per min was 54 +/- 14% of the hemispheric volume. In all rt-PA treated animals the proximal MCA was recanalised, and the volume with flow values below 30 ml/100 g per min was reduced to 29 +/- 17%. Histological findings paralleled the spatial spread of the CBF deficit. The rat model presented is well-suited for investigations of the specific pathophysiology of thromboembolic stroke. Furthermore it allows detailed studies of thrombolytically induced reperfusion, beyond the question of successful recanalisation.

Animals↗
PubMed1997

Relation of neuronal endoplasmic reticulum calcium homeostasis to ribosomal aggregation and protein synthesis: implications for stress-induced suppression of protein synthesis.

Results from experiments performed with permanent non-neuronal cell lines suggest that endoplasmic reticulum (ER) calcium homeostasis plays a key role in the control of protein synthesis (PS). It has been concluded that disturbances in ER calcium homeostasis may contribute to the suppression of PS triggered by a severe metabolic stress (W. Paschen, Med. Hypoth., 47 (1996) 283-288). To elucidate how an emptying of ER calcium stores of these cells would effect PS and ribosomal aggregation of non-transformed fully differentiated cells, experiments were run on primary neuronal cell cultures. ER calcium stores were depleted by treating cells with thapsigargin (TG, a selective, irreversible inhibitor of ER Ca(2+)-ATPase), cyclopiazonic acid (CPA, a reversible inhibitor of ER Ca(2+)-ATPase), or caffeine (an agonist of ER ryanodine receptor). Changes in intracellular calcium activity were evaluated by fluorescence microscopy using fura-2-loaded cells. Protein synthesis was determined by measuring the incorporation of [3H]leucine into proteins. The degree of aggregation of ribosomes was evaluated by electron microscopy. TG induced a permanent inhibition of PS to about 10% of control which was only partially reversed within 2 h of recovery. CPA caused about 70% inhibition of PS, and PS recovered completely 60 min after treatment. Caffeine produced an inhibition of PS to about 50% of control. Loading cells with the calcium chelator BAPTA-AM (33.3 microM) alone suppressed PS without reversing TG- or caffeine-induced inhibition of PS, indicating that the suppression of PS was caused by a depletion of ER calcium stores and not by an increase in cytosolic calcium activity. TG-treatment of cells induced a complete disaggregation of polysomes which was not reversed within the 4 h recovery period following TG-treatment. After caffeine treatment of cells, we observed a heterogenous pattern of ribosomal aggregation: in some neurons ribosomes were almost completely aggregated while in other cells a significant portion of polyribosomes were disaggregated. The results indicate that a depletion of neuronal ER calcium stores disturbs protein synthesis in a similar way to the effects of transient forms of metabolic stress (ischemia, hypoglycemia or status epilepticus), thus implying that a disturbance in ER calcium homeostasis may contribute to the pathological process of stress-induced cell injury.

Animals↗
PubMed1997

Neurological effects of microwave exposure related to mobile communication.

Due to the wide and growing use of mobile communication, there is increasing concern about the interactions of electromagnetic radiation with the human organism, and, in particular, with the brain. In the present report, experimental studies on putative electrophysiological, biochemical and morphological effects of continuous or pulsed microwave radiation are briefly reviewed. Such effects have been described in vitro and in vivo using animals and humans. Particularly, effects on neuronal electrical activity, cellular calcium homeostasis, energy metabolism, genomic responses, neurotransmitter balance and blood-brain barrier permeability have been reported. However, some results have either been disputed, since experimental replication led to contradictory findings, or been related to procedural side effects. Since neurological disturbances induced by mobile telephone devices would be of considerable interest for public health, the authors recognize that further experimental studies, involving strict positive and negative control conditions, will be required in the future. At the present state of knowledge there is no positive evidence that pulsed or continuous microwave exposure in the non-thermal range confers elevated risk to the health of the brain.

Animals↗
PubMed1997

Activation of CPP-32 protease in hippocampal neurons following ischemia and epilepsy.

Recent in vitro studies indicate an involvement of members of the interleukin-1beta converting enzyme (ICE) family of proteases in programmed neuronal cell death. Cell death of hippocampal neurons in animal models of cerebral ischemia and epilepsy shows morphological features of apoptosis and can be prevented by administration of protein synthesis inhibitors suggesting that de novo synthesis of components of the cell death program is necessary for neuronal apoptosis. In the present study we demonstrate by in situ hybridization analysis that expression of CPP-32, an ICE-related protease, is significantly upregulated in CA1 hippocampal neurons following global ischemia induced by cardiac arrest and in hippocampal neurons of the CA3/CA4 region after kainate-mediated epilepsy, respectively. Moreover, an increase in CPP-32-like proteolytic activity was detected in hippocampal extracts 24 h after ischemia using the fluorogenic CPP-32 substrate Ac-DEVD-AMC. Activation of CPP-32 clearly preceded cell death of hippocampal neurons as assessed by in situ end-labelling of nuclear DNA fragments. These results indicate that CPP-32 protease may be activated at both the transcriptional and post-translational level during neuronal apoptosis and that activation correlates with the selective vulnerability of hippocampal pyramidal neurons to ischemic and epileptic insults.

Animals↗
PubMed1997

Quantitative measurement of cerebral protein synthesis in vivo: theory and methodological considerations.

The true rate of cerebral protein synthesis can be calculated from the ratio of labeled proteins to integrated arterial plasma amino acid specific activity (SA) only when the fraction of amino acid precursor pool dilution is known. In the following, current experimental designs on the measurement of cerebral protein synthesis are discussed and compared to our own approach in which the determination of regional precursor pool dilution by recycled unlabeled leucine is combined with the quantitation of regional cerebral protein synthesis rates. For this purpose, a constant arterial plasma leucine SA level is maintained for 45 min by programmed intravenous infusion which is sufficient for complete equilibrium between tissue leucine pool SAs and plasma free leucine SA. In addition to the regional assessment of the precursor dilution factor, protein radioactivity can be determined in the same tissue sample or in parallel brain sections of the same animal by quantitative autoradiography. It is then possible to calculate the actual rate of protein synthesis using the correct fraction of precursor pool dilution. This renders our approach particularly suitable for the quantitative measurement of regional CPS under pathological conditions.

Amino Acids↗
PubMed1997

No effect of glutamate on metabolic disturbances in hippocampal slices of mature fetal guinea pigs after transient in vitro ischemia.

The involvement of glutamate in the development of cerebral metabolic disturbances in mature fetuses after transient ischemia was studied using a hippocampal slice model. We investigated the effects of exogenously applied glutamate or glutamate antagonists on the recovery of energy metabolism and protein synthesis rate (PSR) in hippocampal slices of mature guinea pigs after in vitro ischemia. The slices were incubated in a thermostatically controlled flow-through chamber and gassed with carbogen (95% O2/5% CO2). In vitro ischemia was induced by transferring the slices to an aglycemic, artificial cerebrospinal fluid (aCSF) equilibrated with 95% N2/5% CO2. In a first set of experiments slices were exposed to 10 mM glutamate during a 20-40 min period of in vitro ischemia. In a second set slices were incubated in aCSF containing MK-801 (100 microM) or kynurenic acid (0.5 mM) 30 min before, during and 2 h after in vitro ischemia. After a 12 h recovery phase, the concentrations of adenylates in the slices were measured by HPLC after extraction with perchloric acid. PSR was calculated from the rate of incorporation of [14C]leucine into tissue proteins. Neither glutamate nor glutamate antagonists had any effect on the postischemic recovery of energy metabolism and PSR when applied during in vitro ischemia. It is therefore concluded that glutamate does not play a major role in the development of metabolic disturbances in hippocampal slices from mature guinea pig fetuses subjected to transient in vitro ischemia.

Adenosine Triphosphate↗