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Biomedical subjects

W Kuschinsky

Publications and source records attributed to W Kuschinsky.

At least 37 records · Page 2Linked to original sources
PubMed1998

Capillary patency after transient middle cerebral artery occlusion of 2 h duration.

Reperfusion after transient focal ischemia of 2 h duration is followed by secondary bioenergetic failure after 4 h of reperfusion. The objective of the present study was to explore whether or not this secondary deterioration is due to secondary microcirculatory compromise. Normal fasted rats were subjected to 2 h of MCA occlusion and allowed reperfusion for 2, 4, 6 and 8 h. At predetermined reperfusion times, rats were injected with Evans blue and decapitated. Capillary patency was determined using a fluorescent double-staining technique. No capillary perfusion deficits were detected in the ischemic neocortical penumbra, neocortical focus or striatal focus. We concluded that the secondary deterioration of bioenergetic state is not due to microcirculatory compromise. Since hyperglycemic animals show pan-necrotic lesions, a hyperglycemic group was added at 8 h of reperfusion to test if the adverse effect of hyperglycemia on ischemic damage is related to capillary compromise. The results showed that, in hyperglycemic rats, capillary perfusion in the striatal focus was compromised after 8 h of recirculation following 2 h of MCA occlusion. It is concluded that when normoglycemic rats are subjected to 2 h of MCA occlusion, capillary patency is not affected during the first 4-6 h of reflow. At 8 h of reflow, though, particularly in hyperglycemic rats, microcirculation is compromised in the caudoputamenal focus, probably reflecting infarction.

Animals↗
PubMed1998

Hyperglycemia-exaggerated ischemic brain damage following 30 min of middle cerebral artery occlusion is not due to capillary obstruction.

Transient focal ischemia of brief duration (15-30 min) gives rise to brain damage. In normoglycemic animals this damage usually consists of selective neuronal necrosis (SNN), and is largely confined to the lateral caudoputamen. In hyperglycemic subjects damage occurs more rapidly, involves also neocortical areas, and is often of the pan-necrotic type ('infarction'). Since experiments on forebrain ischemia of 30 min duration suggest that microcirculatory compromise develops during recirculation, we studied whether focal ischemia of the same duration, followed by reperfusion for 1, 2 or 4 h, leads to microcirculatory dysfunction. To test this possibility, we fixed the tissue by perfusion and counted the number of formed elements (leukocytes, macrophages and erythrocytes) in capillaries and postcapillary venules. Furthermore, capillary patency was evaluated following in vivo injection of Evan's blue. Histopathological examination of tissue fixed by perfusion after 1, 2 and 4 h of recirculation showed an increasing density of SNN in the caudoputamen of normoglycemic animals. Hyperglycemic, but not normoglycemic, animals showed pan-necrotic lesions ('infarction') after 4 h of recirculation. As a result, the total volume of tissue damage (SNN plus infarction) was larger in hyper- than in normoglycemic animals at 2 and 4 h of recirculation. In addition, hyperglycemic animals showed involvement of neocortex which increased with the time of reperfusion. In the ischemic hemisphere, between 5 and 10% of counted capillaries contained formed elements. However, since hyperglycemic animals contained an equal (or smaller) amount of cells the results did not suggest that capillary 'plugging' could explain the aggravated damage. Moreover, both normo- and hyperglycemic animals showed close to 100% capillary patency. The results thus fail to support the notion that the aggravation of focal ischemic damage by hyperglycemia is due to obstruction of microvessel by swelling or leukocyte adherence.

Animals↗
PubMed1998

Decreased glucose transporter densities, rate constants and glucose utilization in visual structures of rat brain during chronic visual deprivation.

The question was investigated whether local changes in glucose transporter densities and transport kinetics can occur when local cerebral glucose utilization (LCGU) is decreased in some brain structures. Unilateral visual deprivation was induced by monocular enucleation in 25 rats. After 1 week, the contralateral structures of the visual system were analyzed for (1) densities of glucose transporters Glut1 and Glut3 (immunoautoradiography), (2) LCGU (2-[14C]deoxyglucose method) and (3) local rate constants (3-O[14C]methylglucose method). The ipsilateral structures served as controls. During chronic visual deprivation Glut1 and Glut3 densities, LCGU and rate constants were significantly decreased in some structures of the visual system and remained unchanged in others. These results indicate a moderate degree of downregulation of glucose transporters, LCGU and rate constants in the visual system during visual deprivation.

Animals↗
PubMed1998

Autoradiographic determination of local cerebral blood flow and local cerebral glucose utilization during chemical stimulation of the nucleus tractus solitarii of anesthetized rats.

This study was conducted to determine whether the decrease in cerebral blood flow (CBF) observed during chemical stimulation of the nucleus tractus solitarius (NTS) can be explained by a decrease in cerebral metabolism. In anesthetized (urethane and chloralose), paralyzed and artificially ventilated rats, neurons in the NTS were chemically stimulated by microinjection of L-glutamate. Local cerebral blood flow (LCBF) and local cerebral glucose utilization (LCGU) were quantified in 43 brain structures by quantitative autoradiographic techniques using [14C]iodoantipyrine and 2-[14C]deoxyglucose, respectively. During chemical stimulation of the NTS (n = 6), LCBF decreased significantly in 32 of the 43 structures investigated when compared to either a control group with artificial cerebrospinal fluid injection (n = 6), or a controlled hemorrhage group (n = 5). In the controlled hemorrhage group, blood pressure was decreased to a degree comparable to that induced by microinjection of L-glutamate into the NTS. Mean blood flow of all structures investigated was significantly (P < 0.01) lower in the stimulation group than that in the control group and in the hemorrhage group. No significant differences in LCGU were observed between the three investigated groups in all structures examined except for an increase in LCGU in the chemically stimulated NTS site. It is concluded that the decrease in LCBF measured in most brain structures during chemical stimulation of the NTS is not caused by a decrease in LCGU in these structures and may therefore be explained by neurogenic influences on brain vessels.

Animals↗
PubMed1998

Preischemic hyperglycemia leads to rapidly developing brain damage with no change in capillary patency.

The present experiments were undertaken to explore whether exaggeration of ischemic brain damage by preischemic hyperglycemia is due to lack of capillary patency in the postischemic period. Normo- and hyperglycemic rats were exposed to 10 min of forebrain ischemia. Histopathological changes were evaluated after 6 and 16-18 h of recovery by light microscopy, and capillary patency was assessed at the same time points by a double-staining technique, depicting perfused and morphologically identifiable capillaries. The results demonstrate that some neuronal damage was detectable after 6 h of recirculation which was aggravated after 16-18 h of recirculation in hyperglycemic rats. In contrast, the degree of capillary patency was similar in normo- and hyperglycemic rats. In both groups the perfusion marker, Evans blue, perfused about 95% of all capillaries when injected 10 s before decapitation. Since preischemic hyperglycemia exaggerates brain damage without cessation of capillary perfusion the primary targets of hyperglycemic brain damage may not be capillaries but neurons or glial cells.

Animals↗
PubMed1998

Increase of glucose transporter densities (Glut1 and Glut3) during chronic administration of nicotine in rat brain.

Chronic infusion of nicotine is known to result in a distinct pattern of increases in local cerebral glucose utilization (LCGU). The present study addresses the question whether this increase in LCGU is paralleled by (1) a local increase in Glut1 and/or Glut3 glucose transporter densities and (2) a local increase in capillary density in the brain. Nicotine was infused by osmotic minipumps for one week. In cryosections of rat brains local densities of Glut1 (vascular) and Glut3 (neuronal) glucose transporters were measured by immunoautoradiographic methods whereas local capillary densities were determined by an immunofluorescent method. Densities of glucose transporters Glut1 and Glut3 were increased in 12 of the 27 structures investigated. Glut1 was elevated in four additional structures and Glut3 in two more structures. Comparison of the changes in transporter densities with the changes of LCGU measured in a previous study during chronic nicotine infusion showed that LCGU was also elevated in most of these structures. In contrast, capillary density remained unchanged in all structures investigated. It is concluded that one week of nicotine infusion is sufficient to raise the densities of Glut1 and Glut3 glucose transporters predominantly in those structures in which LCGU is elevated. The unchanged capillary density under these conditions indicates an increased density of Glut1 transporters per capillary.

Animals↗
PubMed1998

Local transport kinetics of glucose during acute and chronic nicotine infusion in rat brains.

Acute and chronic infusion of nicotine is known to result in a distinct increase in local cerebral glucose utilization (LCGU) in several brain structures. The present study addresses the question whether this increase in LCGU is paralleled by a local change in glucose transport in rat brain. Nicotine was infused either acutely for 3 hours or chronically by osmotic minipumps for one week. Local rate constants for glucose transport were measured in brain cryosections using the 3-O-[14C]methylglucose method. Local rate constants K1 and k2 were lower in part of the brain structures during acute (-10% to -20%) and in nearly all structures during chronic (-39% to -41%) nicotine. The finding of a decreased glucose transport during chronic nicotine was confirmed by additional experiments of 3-O-[14C]methylglucose transfer in an epithelial cell culture. It is concluded that acute and chronic nicotine infusion results in decreased glucose transport although LCGU is either unchanged or increased.

3-O-Methylglucose↗
PubMed1998

Local fibrinolysis and aspiration of intracerebral hematomas in rats. An experimental study using MR monitoring.

Serial magnetic resonance (MR) imaging has not yet been validated in the therapy of experimental intracerebral hematomas in a rat model. It is possible to test the effect of local fibrinolysis and aspiration on the clot volume using serial magnetic resonance imaging and different MR-sequences. Experiments were carried out in 22 male Sprague-Dawley rats. Intracerebral hematoma was produced by injection of fresh autologous blood into the caudate nucleus using a double injection technique. Thirty minutes later 10 rats were treated by injecting 12 microliters of recombinant tissue plasminogen activator. MR-imaging was performed immediately after generation of the hematoma and after clot lysis. The clot volume measured in the magnetic resonance images was compared with that obtained in stained histological serial sections at the end of the experiment. Serial MR scanning demonstrated a significant reduction (p < 0.01) of hematoma volume after fibrinolysis followed by aspiration of the blood clot. The best correlation between MR- and histological volumetry was found on RF-spoiled FLASH 2D-images. This study documents the efficacy of MRI in detecting and delineating the size of acute intracerebral hematomas and its time course. Local fibrinolysis and aspiration can be simulated in an experimental rat model.

Animals↗
PubMed1998

Local cerebral blood flow, local cerebral glucose utilization, and flow-metabolism coupling during sevoflurane versus isoflurane anesthesia in rats.

BACKGROUND: Compared to isoflurane, knowledge of local cerebral glucose utilization (LCGU) and local cerebral blood flow (LCBF) during sevoflurane anesthesia is limited. METHODS: LCGU, LCBF, and their overall means were measured in Sprague-Dawley rats (8 groups, n=6 each) during sevoflurane and isoflurane anesthesia, 1 and 2 MAC, and in conscious control animals (2 groups, n=6 each) using the autoradiographic 2-[14C]deoxy-D-glucose and 4-iodo-N-methyl-[14C]antipyrine methods. RESULTS: During anesthesia, mean cerebral glucose utilization was decreased: control, 56+/-5 micronmol x 100 g(-1) x min(-1); 1 MAC isoflurane, 32+/-4 micromol x 100 g(-1) x min(-1) (-43%); 1 MAC sevoflurane, 37+/-5 micromol x 100 g(-1) x min(-1) (-34%); 2 MAC isoflurane, 23+/-3 micromol x 100 g(-1) x min(-1) (-58%); 2 MAC sevoflurane, 23+/-5 micromol x 100 g(-1) x min(-1) (-59%). Local analysis showed a reduction in LCGU in the majority of the 40 brain regions analyzed. Mean cerebral blood flow was increased as follows: control 93+/-8 ml x 100 g(-1) x min(-1); 1 MAC isofurane, 119+/-19 ml x 100 g(-1) x min(-1) (+28%); 1 MAC sevoflurane, 104+/-15 ml x 100 g(-1) x min(-1) (+12%); 2 MAC isoflurane, 149+/-17 ml x 100 g(-1) x min(-1) (+60%); 2 MAC sevoflurane, 118+/-21 ml x 100 g(-1) min(-1) (+27%). LCBF was increased in most brain structures investigated. Correlation coefficients obtained for the relationship between LCGU and LCBF were as follows: control 0.93; 1 MAC isoflurane, 0.89; 2 MAC isoflurane, 0.71; 1 MAC sevoflurane, 0.83; 2 MAC sevoflurane, 0.59). CONCLUSION: Mean and local cerebral blood flows were lower during sevoflurane than during isoflurane anesthesia. This difference cannot be explained by differing changes in glucose utilization because glucose utilization was decreased to the same extent in both groups.

Anesthesia↗
PubMed1997

Distribution of Glut1 glucose transporters in different brain structures compared to glucose utilization and capillary density of adult rat brains.

Glut1 is a specific transporter system that mediates glucose transfer across the blood-brain barrier (BBB). Although the main location of Glut1 is in the capillary endothelium of the brain, its local distribution in different brain regions is not as well defined. In the present investigation, the local pattern of Glut1 distribution was determined in 13 brain structures using an immunoautoradiographic method developed for this purpose. A polyclonal antibody directed against the C-terminal amino acid sequence of Glut1 was applied to cryosections of rat brains. A secondary antibody was added that had been coupled to [35S]. Results show a heterogeneous distribution of Glut1 in the brain with activities of [35S] ranging from 65% below to 15% above the mean. White matter activity was lower than gray matter activity. For comparison, capillary sections were counted in corresponding cryosections by indirect immunofluorescence using fibronectin antibodies. In addition, local cerebral glucose utilization (LCGU) was analyzed in identical brain structures of conscious rats by the quantitative autoradiographic 2-deoxyglucose method. Significant correlations were found between Glut1 density and either LCGU or capillary density. Results indicate a tight coupling of Glut1 transporter density and capillary density to the LCGU of different BBB structures in adult rats.

Animals↗
PubMed1997

Flow-independent heterogeneity of brain capillary plasma perfusion after blood exchange with a Newtonian fluid.

Previous studies from our group have indicated a heterogeneity of plasma transit times in brain capillaries. The heterogeneity was decreased with increasing cerebral blood flow during hypercapnia. In the present study, the hypothesis was tested that these apparent changes in microvascular plasma perfusion heterogeneity depend on the existence of red blood cells (RBC). To this end, the blood of anesthetized and paralyzed rats was replaced by a shear rate-independent oxygen-carrying substitute, ultrapurified polymerized bovine hemoglobin (UPBHB). Cerebral blood flow ([14C]iodoantipyrine technique) or microvascular perfusion pattern (intravenous bolus injection of Evans blue and decapitation 3-4 s later) was measured. After exchange transfusion with UPBHB, cerebral blood flow still varied with arterial PCO2, whereas in contrast to the unexchanged condition, the heterogeneity of the intracapillary Evans blue concentration remained unchanged. Compared with the unexchanged normocapnic condition, the heterogeneity of intracapillary dye concentration was decreased by one-quarter. It is concluded that RBC contribute to the microvascular perfusion heterogeneity in the brain.

Animals↗
PubMed1996

Altered expression of Bcl-2, Bcl-X, Bax, and c-Fos colocalizes with DNA fragmentation and ischemic cell damage following middle cerebral artery occlusion in rats.

Permanent occlusion of the middle cerebral artery in rats was used to assess the effects of focal ischemia on the expression of members of the bcl-2 family which have been implicated in the regulation of programmed cell death. Intraluminal occlusion of one middle cerebral artery for 6 h resulted in histologically detectable brain damage within the ipsilateral caudate putamen, basolateral cortex and parts of the thalamus. In the infarcted basolateral cortex and thalamus fragmentation of DNA was detected in many nuclei using in-situ end-labeling of DNA breaks by terminal transferase, whereas only scattered labeled nuclei were visible in the infarcted caudate putamen. Immunohistochemical analysis revealed activation of c-Fos in the infarcted cortex and thalamus and in the non-infarcted cingulate cortex as has been shown by others. A decrease in immunoreactivity for Bcl-2, and Bcl-X and an increase in immunostaining for Bax was observed exclusively in neurons within the ischemic cortex and thalamus. Within the infarcted caudate putamen, however, protein levels of all bcl-2 family members declined and c-Fos remained absent. By reverse transcription and polymerase chain reaction it was demonstrated that levels of bcl-2 mRNA markedly decreased in the ipsilateral hemisphere, whereas the amount of bax mRNA was elevated. These findings suggest that a shift in the ratio of cell death repressor Bcl-2 to cell death effector Bax and a concomitant activation of c-Fos may contribute to neuronal apoptosis in the infarcted thalamus and cortex.

Animals↗
PubMed1996

Evidence for apoptotic cell death in the choroid plexus following focal cerebral ischemia.

Focal cerebral ischemia in rats subjected to middle cerebral artery (MCA) occlusion results in apoptotic DNA fragmentation and activation of putative cell death effector genes in neurons and functional impairment of the plexus choroideus. In the present study we investigated whether cerebral ischemia may induce apoptotic cell death in the choroid plexus. Using in situ end-labeling by terminal transferase and fluorescein-dUTP, nuclear DNA breaks were detected in the choroid plexus of the lateral ventricle of the ischemic hemisphere after 6 h but not after 1.5 h of MCA occlusion. Intense cytoplasmic immunostaining for pro-apoptotic Bax protein and moderate immunolabeling for Bcl-X was observed in the epithelium of the choroid plexus of the lateral and third ventricles. However, constitutive expression of Bax and Bcl-X proteins in the plexus choroideus did not change significantly following focal ischemia. Thus, cells of the choroid plexus may die by apoptosis after several hours of cerebral ischemia. Modulation of cell death effector genes of the bcl-2 family however, may not be required for apoptotic cell death to occur.

Animals↗
PubMed1996

Postnatal distribution of Glut1 glucose transporter and relative capillary density in blood-brain barrier structures and circumventricular organs during development.

In the adult brain, Glut1 is associated with capillaries that form a tight barrier whereas Glut1 is lacking in capillaries with non-barrier properties, i.e. the circumventricular organs. In the present study the postnatal developmental changes of brain capillaries and Glut1 were compared in different tight and non-barrier structures. Rats were investigated at birth, 5th postnatal day (P5), P10, P15, P20, P30 and at the age of one year. Antibody stains of brain capillaries (fibronectin) and of Glut1 were visualized by fluorescent microscopy in identical brain cryosections. All brain capillaries of structures that have a tight barrier in adult animals showed the existence of Glut1 during postnatal development. Most non-barrier structures lacked Glut1 in their capillary endothelium after birth although Glut1 was found in the area postrema and subfornical organ at P0 and disappeared thereafter. The relative capillary density in tight barrier structures of the gray matter was more than doubled from birth to P20 with minor changes later. In contrast white matter structures missed any significant increase during development. It is concluded that Glut1, as an indicator of barrier properties, is existing in all blood-brain barrier structures at birth already. The capillary densities observed in different brain structures at birth are not related to the values found in adult animals.

Age Factors↗
PubMed1996

Regional heterogeneity of cerebral blood flow response to graded volume-controlled hemorrhage.

OBJECTIVE: Of the animal models of human hemorrhagic shock, the volume-controlled hemorrhage model appears to come closer to the clinical situation than the commonly used pressure-controlled model, since the volume-controlled model allows regulatory adjustment of blood pressure. The effects of volume-controlled hemorrhage on local cerebral blood flow (LCBF) of conscious animals are not known. The present study investigates specific reaction patterns of LCBF in comparison to mean cerebral blood flow (CBF) during graded volume-controlled hemorrhagic shock in conscious rats. METHODS: Conscious, spontaneously breathing, and minimally restrained rats were subjected to different degrees of volume-controlled hemorrhage (taking either 25, 30, 35, or 40 ml arterial blood/kg body weight (b.w.). Thirty minutes after the completion of blood taking, LCBF was determined during hemorrhagic hypovolemia using the autoradiographic iodo (14C) antipyrine method. A group of untreated rats (no hemorrhage) served as controls. LCBF was determined in 34 defined brain structures and mean CBF was calculated. RESULTS: During less severe hemorrhage (25 and 30 ml/kg b.w.) mean CBF was significantly higher than in the control group (+19% and +25%). During severe hemorrhage (35 and 40 ml/kg b.w.) mean CBF remained unchanged compared to the control values, although significant increases in LCBF could be detected in many of the brain structures analyzed (maximum +44%). The mean coefficient of variation of CBF was increased, indicating a larger heterogeneity of LCBF values at shed blood volumes of 35 and 40 ml/kg b.w. CONCLUSIONS: A comprehensive and novel description of the local distribution of CBF during graded volume-controlled hemorrhage in conscious rats shows unexpected increases in LCBF and mean CBF. This "hypovolemic cerebral hyperemia" might be caused by endogenous hemodilution, thus maintaining the blood supply to the brain during hypovolemic shock.

Animals↗
PubMed1996

Experimental intracerebral hemorrhage: description of a double injection model in rats.

For experimental purposes, the most common technique of producing an intracerebral hematoma in rats is the injection of unclotted autologous blood. All modifications of this model share the problem that size and extension of the hematoma are not reproducible, because the injected blood either ruptures into the ventricular system or it extends to the subarachnoid or subdural space. Therefore a double injection model of experimental intracerebral hemorrhage in rats has been developed using 19 male Sprague-Dawley rats. After inducing anesthesia a cannula was stereotactically placed into the caudate nucleus and an intracerebral hematoma was produced with the double injection method in which first a small amount of fresh autologous blood is injected which is allowed to clot (preclotting) in order to block the way back along the needle track; the actual hematoma is produced in a second step of the injection. The clot volume was measured on stained serial sections. A total injection volume of 50 microliters of autologous blood produced intracerebral hematomas of 41.1 +/- 10.0 microliters and of similar shapes. The double injection method allows to generate reproducible hematomas in rats. This new model of intracerebral hemorrhage will allow further investigation of fibrinolytic and cytoprotective therapies.

Animals↗