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A Baethmann

Publications and source records attributed to A Baethmann.

At least 37 records · Page 2Linked to original sources

Cerebral blood flow and the secondary growth of brain tissue necrosis after trauma.

A local brain tissue necrosis from trauma progresses during the following 24 hours or longer. A decrease in cerebral blood flow has been observed both in the necrotic as well as adjacent cortical region, which may influence expansion of the lesion into the perifocal brain tissue. Currently the regional cortical blood flow (rCBF) was assessed by using scanning laser Doppler fluxmetry. Brain tissue necrosis was induced by a highly standardised cold lesion. We attempted to inhibit the development of posttraumatic ischemia in and around the focal lesion by infusion of a hypertonic/hyperoncotic saline/starch solution. The infusion therapy resulted in a temporary improvement of posttraumatic blood flow in both necrotic and distant cortical regions. However, the expansion of the focal necrosis was not reduced. Additional investigations are in progress to determine whether further amelioration with a longer duration of rCBF increase is effective in combination with methods of neuroprotection to inhibit the secondary lesion growth after a traumatic insult.

Animals↗

Interstitial lactate in the peritraumatic penumbra of rat brain.

A traumatic brain tissue necrosis is expanding to approximately 150% within 24 h after lesion. This process is accompanied by marked reduction of the perifocal cerebral blood flow likely to activate anaerobic glycolysis from a reduced O2-supply leading to an accumulation of lactic acid. The current study was carried out to assess the interstitial levels of lactic acid as a potential factor of secondary brain damage. A microdialysis probe was stereotactically implanted approximately 2 mm below the brain surface of the parietal cortex in Sprague Dawley rats (250-300 g bw; n = 6) in chloralhydrate anaesthesia. The position of the probe was controlled by histology. 24 h later a standardised cortical cold injury was induced above the probe in halothane/N2O anaesthesia. Dialysate (2 microliters/min) was collected in 15 min intervals, starting 1 h prior to and continuing until 4 hrs after trauma. The lactate concentration in the dialysate was fluorometrically determined by an enzymatic assay. Under baseline conditions dialysate concentrations of 324 +/- 48 microM were observed. A release of lactate was not found initially after trauma. Between 70 and 105 min later, however, the interstitial lactate levels briefly increased to 416 +/- 34 microM (n.s.), while reaching baseline levels again thereafter. Thus, the current results do not confirm an increased accumulation of lactate in the interstitial compartment of the penumbra despite a marked perifocal hypoperfusion of the brain after focal injury. The transitory increase in lactate at 90 min after trauma is unlikely to have caused a severe tissue acidosis which might be held liable for the secondary growth of the brain lesion induced by the focal injury.

Animals↗

Attenuation of secondary lesion growth in the brain after trauma by selective inhibition of the inducible NO-synthase.

In previous studies we have demonstrate that aminoguanidine pretreatment attenuates the secondary necrosis growth after focal brain trauma. Purpose of the present investigation was to elucidate the therapeutic potential of this iNOS-inhibitor when administered post lesion. Sprague-Dawley rats were subjected to a highly standardized cortical freezing lesion and administered with aminoguanidine (100 mg/kg i.p.) 15 min and 8 hrs after trauma or with isotonic saline, respectively. Animals were assigned to one of three experimental groups. The animals of group I--which served as reference for the histomorphometric determination of the spread of the primary lesion--were sacrificed 5 min after trauma. Group II, receiving isotonic saline and group III with aminoguanidine were subjected to perfusion fixation 24 hrs after trauma for evaluation of the necrosis growth. In controls with saline, the volume of the cortical necrosis increased from 6.07 +/- 1.04 mm3 (5 min) to 8.39 +/- 1.57 mm3 at 24 hrs (group II) after trauma. Treatment with aminoguanidine (group III) led to significant attenuation of the expansion of the necrosis to 6.77 +/- 0.87 mm3 at 24 hrs. Thus, the pathological role of activation of the inducible NO-synthase in the phenomenon of secondary lesion growth is confirmed by the present data on iNOS-inhibition. Attenuation of expansion of the lesion is achieved even when initiating therapy after trauma.

Animals↗

Influence of the bradykinin B1/B2-receptor-antagonist B 9430 on the cerebral microcirculation and outcome of gerbils from global cerebral ischemia.

The influence of the bradykinin B1/B2 antagonist B 9430 on the cerebral microcirculation following global cerebral ischemia was investigated in a closed cranial window preparation in Mongolian gerbils by intravital fluorescence microscopy. Global cerebral ischemia (GCI) was induced by occlusion of both common carotid arteries for 15 min. Leukocyte-endothelium interactions, vessel diameters, and the segmental microvascular blood flow were observed by intravital microscopy before and up to three hours after global cerebral ischemia. Following the early reperfusion period the animals survived up to 4 days after ischemia. The neurological deficit and the body weight were assessed daily. On day 4 animals were subjected to perfusion fixation and the brain was removed. Nerve cell damage from ischemia was quantified histologically in cortex, hippocampus, and striatum. Animals with treatment received the bradykinin B1/B2 receptor antagonist B 9430 before (i.v.), during, and after ischemia (s.c.) until the end of the experiment. The frequency of leukocytes (cells/100 microns x min) rolling along the venular endothelium post ischemia was significantly decreased (p < 0.05) in treated animals as compared to untreated controls (33.0 +/- 6.2 vs. 8.5 +/- 2.3) as well as the number of leukocytes attached to the endothelial surface (7.2 +/- 3.0 vs. 2.0 +/- 1.0, n.s.). The neuroscore on day 4 (pre-ischemic control: 22 points) was reduced to 13.4 +/- 3.2 in untreated animals, while to 4.7 +/- 3.2 points in the treatment group. No differences between animals with and without treatment were found as to the number of viable neurons. Although bradykinin is released in the brain during global cerebral ischemia, its antagonisation does not improve outcome despite the effective inhibition of leukocyte-endothelium interactions.

Animals↗

Neuroprotective effects of the novel brain-penetrating antioxidant U-101033E and the spin-trapping agent alpha-phenyl-N-tert-butyl nitrone (PBN).

Literature on the therapeutic efficacy of free radical scavengers suggests that drugs that are able to cross the blood-brain barrier are more effective in protecting the brain from ischemic damage. However, the exact mechanisms by which brain-penetrating antioxidants act have yet not been delineated. We compared the neuroprotective potential of the newly discovered pyrrolopyrimidine U-101033E with that of alpha-phenyl-N-tert-butyl nitrone (PBN) and investigated their influence on cerebral blood flow. Thirty male Sprague-Dawley rats were subjected to 90 min of middle cerebral artery (MCA) occlusion by an intraluminal filament. Local cerebral blood flow (LCBF) was bilaterally recorded by laser Doppler flowmetry. Neurological deficits were quantified daily. Infarct volume was assessed after 7 days. MCA occlusion reduced ipsilateral LCBF to 20-30% of baseline. After reperfusion, postischemic hyperemia was followed by a decrease in LCBF to about 70% of baseline. There was no difference in LCBF among groups. U-101033E improved neurological function and reduced infarct volume by 52% (P < 0.05). Improvement of neurological function and reduction of infarct volume (-25%) in animals treated with PBN was not significant. We conclude that U-101033E has superior neuroprotective properties compared with PBN. Neither drug improves blood flow during ischemia and 1 h of reperfusion. The mechanisms by which these brain-penetrating antioxidants act remain to be clarified.

Animals↗

Leukocyte-endothelium-interaction in pial vessels following global, cerebral ischaemia.

BACKGROUND: Investigations have shown an increase of leukocyte-endothelium-interaction in a variety of organs following an ischaemic insult. To elucidate the role of leukocyte-endothelium-interaction following global, cerebral ischaemia the present study was performed. METHODS: Global, cerebral ischaemia was induced for twenty minutes by four-vessel-occlusion (PULSINELLI). Leukocyte-endothelium-interaction was studied in the cerebral microcirculation using a rat closed cranial window and intravital microscopy. Leukocytes were stained intravenously using rhodamine 6G. Diameters of pial vessels, leukocyte centreline velocity and number of rolling or adhering leukocytes were determined off-line up to 2 h following global cerebral ischaemia. To confirm these results immunohistochemistry of the brain was performed. FINDINGS: Four-vessel-occlusion induced an iso-electric EEG, venular stasis and minimal rest flow in arterioles. Reperfusion yielded a significant increase of the arteriolar (p < 0.001) and a smaller increase of the venular diameters (p < 0.01). Up to 2 h after ischaemia no significant increase of the number of rolling or adhering leukocytes was measured which was confirmed by immunohistochemistry. INTERPRETATION: In contrast to other studies, in particular regarding focal cerebral ischaemia, an increase of leukocyte-endothelium-interaction in rat brain following 20 min of global cerebral ischaemia was not observed despite histological evidence of ischaemic damage. Thus in our model leukocytes seem not to contribute to the brain damage following global ischaemia.

Animals↗

Contribution of anion transporters to the acidosis-induced swelling and intracellular acidification of glial cells.

This study examines the contribution of anion transporters to the swelling and intracellular acidification of glial cells from an extracellular lactacidosis, a condition well-known to accompany cerebral ischemia and traumatic brain injury. Suspended C6 glioma cells were exposed to lactacidosis in physiological or anion-depleted media, and different anion transport inhibitors were applied. Changes in cell volume and intracellular pH (pH(i)) were simultaneously quantified by flow cytometry. Extracellular lactacidosis (pH 6.2) led to an increase in cell volume to 125.1 +/- 2.5% of baseline within 60 min, whereas the pH(i) dropped from the physiological value of 7.13 +/- 0.05 to 6.32 +/- 0.03. Suspension in Cl(-)-free or HCO(3)(-)/CO(2)-free media or application of anion transport inhibitors [0.1 mM bumetanide or 0.5 mM 4, 4'-diisothio-cyanatostilbene-2,2'-disulfonic acid (DIDS)] did not affect cell volume during baseline conditions but significantly reduced cell swelling from lactacidosis. In addition, the Cl(-)-free or HCO(3)(-)/CO(2)-free media and DIDS attenuated intracellular acidosis on extracellular acidification. From these findings it is concluded that besides the known activation of the Na(+)/H(+) exchanger, activation of the Na(+)-independent Cl(-)/HCO(3)(-) exchanger and the Na(+)-K(+)-Cl(-) cotransporter contributes to acidosis-induced glial swelling and the intracellular acidification. Inhibition of these processes may be of interest for future strategies in the treatment of cytotoxic brain edema from cerebral ischemia or traumatic brain injury.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

Leukocyte-endothelium interactions in pial venules during the early and late reperfusion period after global cerebral ischemia in gerbils.

The contribution of leukocytes to secondary brain damage after cerebral ischemia is still under discussion. The purpose of the present study was to examine the pial microcirculation after global cerebral ischemia while focusing on leukocyte-endothelium interactions during the early and late reperfusion period of up to 4 days. A closed cranial window technique that leaves the dura mater intact was used. Global cerebral ischemia of 15 minutes' duration was induced in male Mongolian gerbils (n = 91). Pial microcirculation was observed by intravital fluorescence microscopy. Leukocyte-endothelium interactions (LEIs) in pial venules, vessel diameters, capillary density, and regional microvascular blood flow measured by laser Doppler flowmetry were quantified during 3 hours of reperfusion and in intervals up to 4 days after ischemia. Within 3 hours of reperfusion, the number of leukocytes (cells/100 microm x minute) rolling along or adhering to the venular endothelium increased from 0.1 +/- 0.2 to 28.4 +/- 17.4 (P < 0.01 vs. control) and from 0.2 +/- 0.2 to 4.0 +/- 3.8 (P < 0.05), respectively. There was no capillary plugging by leukocytes; capillary density remained unchanged. In the late reperfusion period, at 7 hours after ischemia, LEIs had returned to baseline values. Furthermore, from 12 hours to 4 days after ischemia, no LEIs were observed. Changes in regional microvascular blood flow did not correlate with LEIs. Global cerebral ischemia of 15 minutes' duration induces transient LEIs that reach a maximum within 3 hours of reperfusion and return to baseline at 7 hours after ischemia. LEIs are not related to changes in microvascular perfusion, which suggests mainly that the expression of adhesion receptors is necessary to induce LEIs rather than rheologic factors. It seems unlikely that this short-lasting activation of leukocytes can play a role in the development of secondary brain damage.

Animals↗

No additional neuroprotection provided by barbiturate-induced burst suppression under mild hypothermic conditions in rats subjected to reversible focal ischemia.

OBJECT: Mild-to-moderate hypothermia is increasingly used for neuroprotection in humans. However, it is unknown whether administration of barbiturate medications in burst-suppressive doses-the gold standard of neuroprotection during neurovascular procedures-provides an additional protective effect under hypothermic conditions. The authors conducted the present study to answer this question. METHODS: Thirty-two Sprague-Dawley rats were subjected to 90 minutes of middle cerebral artery occlusion and randomly assigned to one of four treatment groups: 1) normothermic controls; 2) methohexital treatment (burst suppression); 3) induction of mild hypothermia (33 degrees C); and 4) induction of mild hypothermia plus methohexital treatment (burst suppression). Local cerebral blood flow was continuously monitored using bilateral laser Doppler flowmetry and electroencephalography. Functional deficits were quantified and recorded during daily neurological examinations. Infarct volumes were assessed histologically after 7 days. Methohexital treatment, mild hypothermia, and mild hypothermia plus methohexital treatment reduced infarct volumes by 32%, 71%, and 66%, respectively, compared with normothermic controls. Furthermore, mild hypothermia therapy provided the best functional outcome, which was not improved by additional barbiturate therapy. CONCLUSIONS: The results of this study indicate that barbiturate-induced burst suppression is not required to achieve maximum neuroprotection under mild hypothermic conditions. The magnitude of protection afforded by barbiturates alone appears to be modest compared with that provided by mild hypothermia.

Anesthetics, Intravenous↗

A new multiparameter flow cytometer: optical and electrical cell analysis in combination with video microscopy in flow.

BACKGROUND: Flow cytometers, which are commercially available, do not necessarily meet all demands of actual biomedical research. This is the case for the investigation of mechanisms involved in cell volume regulation, which requires electrical volume measurement and ratiometric multichannel fluorescence analysis for the simultaneous assessment of different physiologic parameters (intracellular pH and the intracellular concentration of calcium ions, etc). METHODS AND RESULTS: We describe the construction of a new nonsorting flow cytometer designed for the simultaneous acquisition of seven parameters including fluorescence signals, forward and perpendicular light scatter, cell volume according to the electrical Coulter principle, and flow cytometric imaging. The instrument is equipped with three different light sources. A tunable argon-ion laser generates efficient excitation of the most standard fluorescent probes in the visible spectral range, and an arc lamp provides the means for ultraviolet excitation at low cost. Because of the spatial filtering by the excitation and detection optics, two independent sets of dual fluorescence measurements can be performed, a prerequisite for flexible ratiometric fluorescence analysis. A flow video microscope integrated into the optical system optionally generates either brightfield or phase images of selected flowing particles. Only particles whose individual datasets meet predefined gating conditions are imaged in real time. To avoid smear effects, the motion of the object to be imaged (speed approximately 8 m/s) is frozen on the target of a CCD camera by flash illumination. For this purpose, a high radiance gas discharge lamp with 25-mJ electric pulse energy provides an illumination time of 18 ns (full width half maximum). Test results obtained from latex spheres and cells are shown. CONCLUSIONS: Test results indicate that our instrument can perform Coulter measurements in combination with flexible optical analysis. Moreover, integration of an adapted video microscope into a flow cytometer is an approach to overcome the gap between flow and image cytometry.

Animals↗

Neuroprotective efficacy of combination therapy with two different antioxidants in rats subjected to transient focal ischemia.

The vascular endothelium and parenchyma of the brain have both potential pathways to generate free radicals under pathological conditions. We evaluated the neuroprotective efficacy of two different antioxidants, a microvascularly acting 21-aminosteroid (U-74389G) and a brain-penetrating pyrrolopyrimidine (U-101033E) alone and in combination. Forty Sprague-Dawley rats were randomly assigned to one of four treatment groups: (1) vehicle-treated controls, (2) U-74389G, (3) U-101033E, (4) U-74389G+U-101033E. Drugs were administered in a dosage of 3x3 mg/kg i.v. before, during, and after ischemia. All animals were subjected to 90 min of middle cerebral artery occlusion. Local cortical blood flow (LCBF) was continuously recorded by bilateral laser Doppler flowmetry. Functional deficits were quantified by daily neurological examinations. Infarct volume was assessed after 7 days. There were no significant differences in LCBF among groups. U-101033E improved neurological function from postoperative day 4 to 7, while U-74389G did not improve neurological recovery. Animals treated with both drugs showed significantly less deficits from postoperative day 1 to 7. U-101033E and combination therapy reduced total infarct volume by 53% and 54% (P<0.05). U-74389G non-significantly reduced total infarct volume by 25%. Cortical infarct volume was significantly reduced in all treatment groups but only U-101033E and combination therapy protected the basal ganglia from infarction. In conclusion, brain-penetrating antioxidants have superior neuroprotective properties compared to microvascularly acting agents. Combination therapy, affording antioxidation plus radical scavenging in blood vessels and brain parenchyma, might yield the highest degree of neuronal protection from peroxidative damage. The neuroprotective efficacy seems to be independent of CBF.

Analysis of Variance↗

EEG burst suppression is not necessary for maximum barbiturate protection in transient focal cerebral ischemia in the rat.

Barbiturates have been demonstrated to reduce the cerebral metabolic rate (CMR) in a dose-dependent manner but investigations of a dose-response relationship for their neuroprotective efficacy are scant. It has been suggested that barbiturates possess other mechanism of action that may be critical to their protective effect. If so, it is conceivable that the peak effect of such mechanisms does not parallel the reduction in CMR. Thus, maximal neuroprotection may be achieved with a substantially lower dose of the drug. Thirty Sprague-Dawley rats were subjected to 2 h of middle cerebral artery occlusion while either anesthetized with (1) halothane (control) or (2) intravenous thiopental titrated to cause mild EEG suppression or (3) thiopental titrated to maintain EEG burst suppression. Cortical blood flow was recorded by continuous bilateral laser Doppler flowmetry (LDF). Infarct volume was assessed after 3 h of reperfusion. Low-dose thiopental decreased blood flow to 80% of baseline and high-dose thiopental to 70% of baseline. LDF did not indicate improvement of blood flow by thiopental in the ischemic area. Compared to controls, low-dose thiopental significantly decreased infarct volume by 28% and high-dose thiopental by 29%. The results of this study and a review of literature indicate that barbiturates provide cerebral protection but that the magnitude of this effect has been overestimated. Other mechanisms than CMR reduction seem to contribute to their beneficial effects, and high doses administered to the point of burst suppression may not be required to obtain maximal protection.

Animals↗

Glial cell swelling--effect of hypothermia.

The effect of mild to moderate hypothermia (32/27 degrees C) was analyzed on the cell volume of C6 glioma cells and primary cultured astrocytes at normal pH, during lactacidosis (pH6.2) and during exposure to glutamate or arachidonic acid in vitro. The cells were suspended in an incubation chamber under continuous control of pH, pO2 and temperature. Cell swelling was quantified by an advanced Coulter-system. Following a control period at 37 degrees C, the ambient temperature was decreased to 27 and 32 degrees C for 30 min. Hypothermia alone led to an immediate and significant cell volume increase of 107.3 +/- 0.4% (mean +/- SEM) of control after 30 min at 32 degrees C. Yet, hypothermia (27 degrees C) afforded partial protection against the acidosis-induced cell swelling at pH 6.2, attaining 120.4 +/- 0.9% in the normothermic control group after 60 min, while only 111.3 +/- 0.9% at 27 degrees C. Hypothermia, however, was not associated with a reduction of the glutamate- or arachidonic acid-induced cell swelling. The results demonstrate that mild hypothermia per se induces glial cell swelling, but simultaneously inhibits cell swelling from acidosis, while not from glutamate- or arachidonic acid.

Acidosis, Lactic↗

System analysis of patient management during the pre- and early clinical phase in severe head injury.

Head injury with or without polytrauma is the most important cause of death and severe morbidity in an age bracket of up to 45 years. Two major factors are determining its outcome, the extent and nature of the primary irreversible brain injury, and the subsequently developing manifestations of secondary brain damage, which in principle can be prevented by the management procedures and therapeutical interventions. Therefore, a better outcome from severe head injury depends exclusively on a higher efficiency of the management and treatment in order to inhibit secondary brain damage. In a novel nationwide research program on "Neurotraumatology and Neuropsychological Rehabilitation" sponsored by the Federal Government, the University of Munich in collaboration with the Max-Planck-Institute of Neurobiology, Martinsried, formed a research consortium with major city hospitals in Munich, Augsburg, Ingolstadt, Murnau, Vogtareuth, and the Southern Bavaria rural area, which are caring for neurotrauma patients with severe head- or spinal cord injury. Together with the corresponding rescue- and emergency organizations, such as the Red Cross, fire brigades, etc. the consortium is carrying out a system analysis as a joint venture on the organization, logistics, management, patient referral, etc. in severe head injury. The analysis includes the assessment of outcome-relevant time intervals of providing emergency care during the preclinical phase until admission of the patient to the hospital, until termination of the diagnostic procedures after hospital admission, and of the clinical management. The present findings and results are based on these comprehensive investigations by the study group in collaboration with more than 30 hospitals, institutions, organizations, and of more than forty physicians, students, and statisticians. In total 194 patients suspected to suffer from severe head injury were prospectively documented with onset of the assessment in the preclinical rescue phase. Confirmation of severe head injury according to a priori established selection criteria was obtained in 100 patients, the remaining number of cases was excluded. The protocol by purpose did not impose study-specific requirements outside of the routine procedures, which are established for the preclinical care and early hospital management. An exception, however, was to collect arterial blood samples, if possible prior to intubation and ventilation, or administration of O2, in order to obtain early information on the acute respiratory state as a potential risk factor of the outcome. Arterial blood samples could be collected in 60 cases at the scene, in no less than 37 patients prior to intubation and ventilation. The data collected during the prehospital and early clinical phase on the temporal course of these patients provide valuable information with unmatched accuracy for evaluation of the management efficiency of the rescue system, transportation, and the clinical care. In conclusion, the prospective system analysis on the organization and management of patients with severe head injury is the first study of this type carried out in Germany. Due to the specific efforts of quasi on-line documentation of the patients' state and course of events, beginning at the scene of an accident and covering the first days at the hospital, data of high quality were obtained. The data flow during the investigation was maintained among others by regular conferences of the Study Group including the crew of documentation assistants at regular intervals. The presently reported phase-1 study was concluded in October 1997. It is followed by a phase-2 study with the attempt to collect prehospital- and early clinical management and care data in the catchment area on an epidemiological basis. (ABSTRACT TRUNCATED)

Craniocerebral Trauma↗

Technical note: a new model for quantitative analysis of brain oedema resolution into the ventricles and the subarachnoid space.

OBJECTIVE: The aim of the current study was to develop an experimental animal model for quantitative analysis of oedema resolution via the subarachnoid space and the ventricular system using fluorescent oedema markers. METHODS: Artificial cerebrospinal fluid (CSF) containing TRITC-albumin (MW 67.000D) and Na(+)-fluorescein (MW 376D) was continuously infused into the white matter of the left frontal lobe of New Zealand white rabbits (n = 6) at a rate of 100 microliters/h for 3 hrs. A closed cranial window for superfusion of the brain surface with artificial CSF fluid (3 ml/h) was implanted above the left parietal cortex for measurement of the fluorescence markers in the subarachnoid space. Uptake of the fluorescence indicators into the ventricles was quantified by ventriculo-cisternal perfusion (3 ml/h). The effluates were collected at 30 min intervals for 3 hrs after the start of infusion. Clearance of the oedema fluid into the perfusates was measured by fluorescence spectrophotometry. RESULTS: At an intracranial pressure of 15.0 +/- 1.7 mm Hg (mean +/- SEM) both indicators started to accumulate in the subarachnoid and ventricular perfusates at 90 min following onset of oedema fluid infusion. The concentrations of the indicators in the ventricular system increased to 7.7 +/- 5.1% of Na(+)-fluorescein and 16.1 +/- 13.0% of TRITC-albumin of the total amount infused were recovered in the ventricular system at 3 hours after start of the oedema infusion, while 3.4 +/- 3.2% of Na(+)-fluorescein and 3.7% +/- 3.2 of TRITC-albumin, respectively, were found in the effluates of the subarachnoid space. CONCLUSION: The present study demonstrates that resolution of vasogenic brain oedema into the cerebral ventricular system and the subarachnoid space following its entry into cerebral white matter can be quantitatively analysed using fluorescence markers, which serve as oedema fluid indicators. The results indicate that the oedema fluid is cleared not only into the ventricular system but also via the subarachnoid space.

Animals↗

Effect of lactacidosis on cell volume and intracellular pH of astrocytes.

Acute traumatic or ischemic cerebral lesions are associated with tissue acidosis leading to cytotoxic brain edema, predominantly affecting astrocytes. Glial swelling from acidosis is believed to be the attempt of cells to maintain a physiological intracellular pH (pHi). However, this concept, potentially important for the development of new treatment strategies for cytotoxic brain edema, has not been validated experimentally. In the present study, cell volume and pHi of astrocytes were measured simultaneously in vitro. Exposure of suspended astrocytes to levels of acidosis found in vivo during ischemia and trauma (pH 6.8-6.2) led to a maximal increase in cell volume of 121.2% after 60 min (n = 5, p < 0.05) and to immediate intracellular acidification close to extracellular levels (pH 6.2, n = 5, p < 0.05). Inhibition of membrane transporters responsible for pHi regulation (0.1 mM amiloride for the Na+/H+ antiporter or 1 mM SITS for HCO3- -dependent transporters) inhibited cell swelling from acidosis but did not affect the profound intracellular acidification. In addition, acidosis-induced cell swelling and intracellular acidification were partly prevented by the addition of ZnCl2 (0.1 mM), an inhibitor of selective proton channels not yet described in astrocytes (n = 5, p < 0.05). In conclusion, these data demonstrate that glial swelling from acidosis is not a cellular response to defend the normal pHi, as had been thought. If these results obtained in vitro are transferable to in vivo conditions, the development of blood-brain barrier-permeable agents for the inhibition of acidosis-induced cytotoxic edema might be therapeutically useful, since they do not enhance intracellular acidosis and thus cell damage.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗

Neuroprotective effects of combination therapy with tirilazad and magnesium in rats subjected to reversible focal cerebral ischemia.

OBJECTIVE: Cell death after cerebral ischemia is mediated by release of excitatory amino acids, calcium influx into cells, and generation of free radicals. We examined the hypothesis that concurrent administration of tirilazad, a well-known antioxidant, and magnesium, an antagonist of calcium and excitatory amino acids, would result in a synergistic neuroprotective effect. METHODS: Sprague-Dawley rats were subjected to transient middle cerebral artery occlusion and assigned to one of four treatment arms (n = 10 in each): 1) vehicle, 2) tirilazad, 3) MgCl2, or 4) tirilazad and MgCl2. Cortical blood flow was recorded using laser Doppler flowmetry. Functional deficits were quantified by performing daily neurological examinations. Infarct volume was assessed after 7 days. RESULTS: There was no difference in cortical blood flow among groups. Animals that received tirilazad or MgCl2 monotherapy had significantly better neurological function compared with control animals only on postoperative Days 3 and 4, whereas animals treated with both drugs had significantly better neurological function than did control animals from postoperative Days 2 through 7. Magnesium reduced total infarct volume by 25% (nonsignificant), tirilazad by 48% (P<0.05), and combination therapy by 59% (P<0.05) compared with control data. CONCLUSION: Combined therapy with antagonists of excitatory amino acids and free radicals provides better neuroprotection from the effects of transient focal ischemia than does therapy with either antagonist alone. In contrast to many experimental agents, tirilazad and magnesium offer the advantage of being licensed for clinical use. This drug combination could be of great benefit when administered before temporary artery occlusion in patients undergoing cerebrovascular surgery.

Animals↗

Influence of platelet-activating factor on cerebral microcirculation in rats: part 1. Systemic application.

BACKGROUND AND PURPOSE: Platelet-activating factor (PAF) has been demonstrated to have a mediator function in shock, with some of its deleterious effects being attributed to its influence on microcirculation. Systemic PAF concentrations as found in shock could also compromise the cerebral microcirculation. Our purpose in the present study was to examine the influence of systemically applied PAF on microvascular perfusion and leukocyte-endothelium interactions in cerebral microvessels. METHODS: A closed cranial window technique was used for intravital fluorescence microscopy of the brain surface. PAF was infused in concentrations of 10(-12), 10(-9), and 10(-6) mol/L into the carotid artery (5 mL/h for 20 min) of Sprague-Dawley rats (n=30). The selective PAF receptor antagonist WEB 2170BS (2 mg/kg body weight) was used to inhibit specific PAF effects. RESULTS: The number of leukocytes (cells/100 microm. min) rolling along or adhering at the venular endothelium increased following infusion of PAF 10(-6) mol/L from 7.7+/-2.5 to 24.4+/-8.9 (P<0.05) and from 1.9+/-0.5 to 6.9+/-2.2 (P<0.05), respectively, within 2 hours. Mean arterial pressure decreased from 92+/-22 mm Hg to 49+/-17 mm Hg (P<0.05). The lower concentrations of PAF were less effective to decrease mean arterial pressure but also induced leukocyte-endothelium interactions. The intravenous administration of WEB 2170BS 15 min before the infusion of PAF 10(-6) mol/L prevented both systemic hypotension and activation of leukocyte-endothelium interactions. CONCLUSIONS: Increased systemic blood levels of PAF as found during shock can not only cause systemic arterial hypotension but also induce leukocyte-endothelium interactions in cerebral venules. The activation of leukocytes was found to be independent of PAF-induced arterial hypotension. The specificity of these results is confirmed by the findings that WEB 2170BS could inhibit the PAF-induced systemic hypotension as well as the activation of leukocytes.

Animals↗