Search PubMed⌕ Search

Biomedical subjects

W Paschen

Publications and source records attributed to W Paschen.

At least 109 records · Page 6Linked to original sources
PubMed1986

Triple-tracer autoradiography of cerebral blood flow, glucose utilization, and protein synthesis in rat brain.

A triple-tracer autoradiographic technique is described that permits the simultaneous measurement of cerebral blood flow, glucose consumption, and protein synthesis using 131I-iodoantipyrine (131I-IAP), [14C]deoxyglucose ([14C]DG), and 3H-amino acids as radioactive tracers. Autoradiographic differentiation between isotopes was performed by taking advantage of different half-lives, solubility of labeled tracers in a wash solution, and sensitivity of the photographic material to disintegrations of the radionuclides. Blood flow autoradiograms using 131I-IAP were obtained by immediate exposure of brain sections to Kodak NMB film for 24 h. During 131I autoradiography contamination by 3H was absent and by 14C was negligible at tissue concentrations of less than 0.45 microCi/g brain tissue. After complete decay of 131I, reexposure of brain sections to Kodak NMB film for 2 weeks provided autoradiograms that stemmed exclusively from 14C disintegrations without contamination by either 131I or 3H and that represented regional glucose utilization. Brain sections were then wash-incubated for 12 h to remove [14C]DG, [14C]DG-6-phosphate, and free 3H-amino acids from the tissue, and exposed to 3H-sensitive LKB Ultrofilm for 2 weeks for autoradiography of 3H-amino acid incorporation into proteins. 14C radioactivity remaining in the tissue section after wash-incubation was determined by exposing sections again for 2 weeks to Kodak NMB film; the resulting contribution to the blackening of 3H-autoradiograms was corrected for by means of digital subtraction using an image-processing system. The triple-tracer autoradiographic technique was validated in rats under various physiological and pathophysiological conditions. In intact animals extinction correction was necessary only for 3H-autoradiograms. Under pathophysiological conditions, however, significant contamination of 131I by 14C occurred in regions with low blood flow and increased glucose utilization rate; this also required correction by digital subtraction. The interpretation of triple-tracer autoradiographic results is limited by the same restrictions as single-tracer autoradiography, but the simultaneous assessment of the three parameters considerably facilitates the interpretation of the flow/metabolic relationship, particularly under pathological conditions.

Animals↗
PubMed1985

Regional changes in tissue pH and glucose content during cortical spreading depression in rat brain.

After eliciting a single passage of spreading depression in rat brain cortex, regional alterations in glucose content and tissue pH were studied in relation to changes in cortical steady potential. Migration of spreading depression into non-invaded cortex was accompanied by a drastic decrease in glucose concentration and tissue pH which persisted longer than the transient depolarization of cortical cells. This delay in metabolic recovery is probably accounted for by severe tissue acidosis which results from the stimulation of anaerobic glycolysis.

Animals↗
PubMed1985

Superoxide dismutase activity in experimental focal cerebral ischemia.

The activity of the free radical scavenger, superoxide dismutase, was studied in focal cerebral ischemia produced in Mongolian gerbils (Meriones unguiculatus) by occluding the right common and left external carotid arteries under halothane anesthesia. After recovery from anesthesia animals were classified according to their neurologic symptoms. Five animals exhibiting neurologic symptoms such as hemiparesis and rolling seizures were reanesthetized 120 min after vascular occlusion and their brains frozen in situ with liquid nitrogen. A series of 20-micron-thick coronal sections was cut in a cryostat; pictorial representations of tissue pH, ATP, and glucose were obtained using fluorescent and bioluminescent techniques. Using a highly sensitive bioluminescent technique, Cu,Zn-superoxide dismutase (Cu,Zn-SOD) and Mn-superoxide dismutase (Mn-SOD) activities were then measured in samples from both ischemic and nonischemic regions of the remaining tissue block. Cu,Zn-SOD and Mn-SOD activities were, respectively, 13.9 +/- 0.7 X 10(3) units/g and 5.4 +/- 0.3 X 10(3) units/g in the nonischemic tissue, and 13.2 +/- 0.6 X 10(3) units/g and 5.0 +/- 0.2 X 10(3) units/g within the ischemic tissue. Thus focal cerebral ischemia does not lead to a global decrease in SOD activity, as observed by others after heart and liver ischemia.

Animals↗
PubMed1985

Neurologic deficit, blood flow and biochemical sequelae of reversible focal cerebral ischemia in cats.

Temporary focal cerebral ischemia was induced in 23 cats by occluding the left middle cerebral artery (MCA) for 2 h. Animals then were divided into groups for unforced reperfusion of varying duration ranging from 2 to 48 h. Regional blood flow (rCBF) at the borders of the ischemic area was measured repeatedly using the hydrogen clearance technique, and neurological ratings were obtained, both during ischemia and reperfusion. At the scheduled end of reperfusion brains were frozen in situ with liquid nitrogen, and regional distributions of biochemical substrate contents as well as tissue pH were visualized using bioluminescence and fluorescence techniques. During focal ischemia collateral flow in the border zone dropped to 55 +/- 20.3% of control level, and all animals developed a neurologic deficit with a median of 6 points on a disability scale from 0 to 10, rCBF and functional impairment being closely correlated (tau = -0.47, P1 less than 0.005). After reopening of the MCA there was an immediate and rather uniform increase in border zone flow to 105 +/- 25.7% of control level, while neurologic recovery was quite variable. In all but one animal reversible ischemia led to persistent disturbances in the energy-producing metabolism as demonstrated by the low regional ATP content, which in part was accompanied by a diminished NADH fluorescence and an alkaline pH shift at high tissue glucose levels. These findings suggest that disturbances in cerebral energy metabolism induced by temporary ischemia may be caused by inhibition of the glycolytic pathway that is hardly reversed by unforced reperfusion and, therefore, results in permanent damage.

Adenosine Triphosphate↗
PubMed1985

Multiparametric imaging of blood flow and metabolism after middle cerebral artery occlusion in cats.

In anesthetized adult cats, acute stroke was produced by transorbital occlusion of the left middle cerebral artery. A battery of imaging techniques was used for simultaneous evaluation of regional blood flow, glucose utilization, protein synthesis, pH, and the regional tissue content of glucose, ATP, and potassium. The electrophysiological impact of stroke was monitored by EEG frequency analysis and recording of somatosensory evoked potentials. Two hours after vascular occlusion, a close correlation existed between the degree of electrophysiological changes and biochemical alterations, in particular with the extent of tissue acidosis, ATP depletion, decrease of tissue potassium content, and suppression of protein synthesis. However, there was only a poor correlation with blood flow and glucose utilization. Both of these exhibited a greatly inhomogeneous pattern with regions of reduced, normal, or increased rates. In areas remote from the infarct, the content of biochemical substrates was normal but blood flow was reduced globally by approximately 50% and glucose utilization by approximately 20%. An anatomically defined regional pattern of cerebral or cerebellar diaschisis was not observed. It is concluded that during the acute phase of stroke, imaging of blood flow and glucose utilization does not provide an accurate estimate of the actual functional or metabolic disturbance. For the clinical evaluation of the development or treatment of stroke, in consequence, alternative noninvasive techniques such as imaging of protein synthesis and/or pH may be more relevant.

Adenosine Triphosphate↗
PubMed1985

Regional quantitative determination of brain glucose in tissue sections: a bioluminescent approach.

A bioluminescent technique is described for the regional quantitative determination of brain glucose. A close linear interrelationship was obtained between the optical density of the bioluminescent images and the glucose content in tissue samples. The regression coefficients of this correlation permit the quantification of glucose bioluminescent pictures using an image-processing system. Regional distribution of glucose was correlated to regional tissue pH under both physiological and pathophysiological conditions.

Animals↗
PubMed1985

Regional quantitative determination of lactate in brain sections. A bioluminescent approach.

Regional lactate distribution in brain was assessed quantitatively in coronal sections using a bioluminescent technique. This bioluminescence can be induced by covering freeze-dried and heat-inactivated brain sections with a frozen solution containing enzymes and coenzymes both for lactate-dependent NADH formation and NADH-dependent bioluminescence, which was recorded photographically. Quantification and density coding of bioluminescent images were carried out by utilizing the regression coefficients of the correlation between the optical density of bioluminescent pictures and the lactate content measured in tissue samples. Regional quantitative lactate images were obtained from brain tissue taken from brain tumors or after experimental cerebral ischemia.

Animals↗
PubMed1984

Regional changes of blood flow, glucose, and ATP content determined on brain sections during a single passage of spreading depression in rat brain cortex.

Hemodynamic and biochemical substrate changes are associated with cortical spreading depression (CSD). Regional methods were used to measure blood flow, and glucose and ATP concentrations in intact brain sections in rats undergoing a single passage of cortical spreading depression. Changes were expressed as the percentages of the contralateral homotopic area of the unaffected cortex. A depression in tissue ATP content preceded the negative DC potential shift and ATP was reduced by 12% (P less than 0.01) despite unaltered blood flow and glucose concentration. When the negative shift of DC potential reached its maximum, glucose content decreased to 72% of control (P less than 0.01) and was accompanied by a further ATP decrease to 54%. When the cortical steady potential declined, blood flow was elevated twofold (P less than 0.01). The ATP content gradually returned to normal; however, cortical glucose concentrations remained at 55% of control values. The relationship of blood flow and glucose and ATP concentration with other known changes during spreading depression are discussed. With the advantage of higher resolution the provided techniques may be a useful tool for studies on hemodynamic and biochemical changes of other pathophysiologic conditions.

Adenosine Triphosphate↗
PubMed1984

Neurologic deficit and cerebral ATP depletion after temporary focal ischemia in cats.

Focal ischemia was induced in 23 cats by occluding the left middle cerebral artery for 2 h. The animals were then divided into groups for unforced reperfusion of variable duration ranging from 2 to 48 h. Neurological ratings were obtained during both ischemia and reperfusion. Following planned sacrifice the regional ATP content was assessed by means of a bioluminescence method showing spatial distribution and degree of ATP depletion. All the animals developed a neurologic deficit, with a median of 6 points on a disability scale of 0-10. After reopening of the middle cerebral artery, neurologic recovery was quite variable depending on the initial neurologic deficit (partial phi = 0.67, p1 less than 0.05): Animals with mild initial functional impairment improved and those with severe neurologic disturbances either died early or developed a more severe neurologic deficit, irrespective of the duration of reperfusion. The degree of ATP depletion and the amount of brain tissue involved exhibited a significant correlation with the neurological outcome (tau = 0.50, p1 less than 0.05), but they were even more closely related to the initial neurologic deficit (partial phi = 1.00, p1 less than 0.001), suggesting an early definitive manifestation of deficiencies in regional energy metabolism.

Adenosine Triphosphate↗
PubMed1983

A topographic quantitative method for measuring brain tissue pH under physiological and pathophysiological conditions.

A technique was developed for the quantitative regional assessment of brain pH by a modification of the umbelliferone method. Twenty micron thick sections were brought into contact with umbelliferone-soaked paper strips and the fluorescence (450 nm) following excitation at 370 nm and 340 nm was recorded photographically. The 340 nm excitation image was subtracted from 370 nm picture, using a computerized image-processing system. Regional pH values were measured in rats and cats under normal and ischemic conditions.

Acid-Base Equilibrium↗
PubMed1983

Pathophysiological aspects of blood-brain barrier disturbances in experimental brain tumors and brain abscesses.

Experimental tumors and abscesses were produced by intrahemispheric inoculation of a blastomatous glial cell clone and of staphylococcus aureus, respectively. In both models severe vasogenic brain edema developed. The site of the barrier lesion was identified by systemic application of Evans blue or peroxidase, and the spread of edema by immunoautoradiographic localisation of extravasated serum proteins. In both experimental conditions, serum proteins accumulated diffusely in the white matter of the ipsilateral hemisphere, although the barrier lesion was strictly confined to the pathological focus. Water content of the edematous white matter in the vicinity of tumors and abscesses increased from 69.1 to 80.6 and 82.3 ml/100g w.w., respectively. This increase was associated with a volume-dependent decrease of flow, a parallel increase of sodium and an increase of extravasated serum proteins. The latter was determined by a newly developed immunochemical approach with appropriate corrections for the intravascular fraction of total serum protein content. The calculated concentration of sodium in edema fluid of tumors and abscesses amounted to 132 and 129 ueq/ml, respectively. The concentration of serum proteins was 8.7 and 6.4 mg/ml, respectively. Protein content of edema fluid, in consequence was less than 10% of blood serum. This suggests that fluid accumulation in vasogenic edema cannot be explained by the oncotic properties of extravasated proteins alone.

Animals↗
PubMed1983

Biochemical changes during graded brain ischemia in gerbils. Part 1. Global biochemical alterations.

In Mongolian gerbils (Meriones unguiculatus) cerebral ischemia was produced by occlusion of the right common and the left external carotid arteries. Gerbils were classified according to their neurological appearance as "symptom-negative" (8 animals), "mild symptoms" (unilateral hemiparesis, 10 animals) and "severe symptoms" (hemiparesis and rolling seizures, 8 animals). Two hours after vascular occlusion various substrates and enzymes related to the energy-producing metabolism, were assessed in tissue samples from both hemispheres. In symptom-negative animals, the only change was a slight decrease of glycolytic intermediates in the right hemisphere. In animals with mild symptoms, the right hemisphere additionally exhibited an impairment of the redox and energy state and an enhancement of the activity of most enzymes of the glycolytic pathway, except hexokinase. In animals with severe symptoms, these changes were even more pronounced and affected--to a lesser degree--also the left hemisphere. The results obtained demonstrate that the neurological appearance of the animals after vascular occlusion correlates with the biochemical alterations and, therefore, can be used for estimating the density of graded ischemia.

Alanine Transaminase↗
PubMed1983

Biochemical changes during graded brain ischemia in gerbils. Part 2. Regional evaluation of cerebral blood flow and brain metabolites.

Regional changes of cerebral blood flow and biochemical substrates were assessed in the gerbil brain following different grades of cerebral ischemia. Ischemia was produced by occlusion of the right common carotid and left external carotid arteries. Gerbils were classified according to the severity of neurological symptoms as animals without, with mild and with severe neurological deficits. Brains were frozen in situ, sliced in 20-microns sections and processed for pictorial presentation of glucose and ATP, using bioluminescence techniques. Cerebral blood flow was determined in adjacent brain sections, using [14C]iodoantipyrine autoradiography. NADH fluorescence was recorded by illuminating the surface of the tissue block with ultraviolet light. Most animals without visible neurological symptoms exhibited reduced blood flow in circumscribed regions of cortex and basal ganglia of the right hemisphere without concomitant changes of biochemical substrates. In animals with mild neurological symptoms, blood flow in the right hemisphere was reduced, glucose and ATP decreased, and NADH fluorescence unhomogeneously enhanced. In animals with severe neurological symptoms blood flow was almost arrested in the right hemisphere and was distinctly reduced in the medial parts of the left hemisphere. The ischemic tissue was depleted from glucose and ATP, and exhibited bright NADH fluorescence. The severity of neurological symptoms, in consequence, correlated closely with both the degree and the size of biochemical lesions observed in the ischemic territory.

Adenosine Triphosphate↗
PubMed1983

Regional assessment of energy-producing metabolism following prolonged complete ischemia of cat brain.

The regional content of biochemical substrates of energy-producing metabolism was assessed in cat brains following prolonged cerebral ischemia. Ischemia was produced by intrathoracic occlusion of the innominate, the left subclavian, and both mammarian arteries, and additional lowering of the systolic blood pressure to 80 mm Hg. After 60 min of global ischemia and 3 h of recirculation, the regional distribution of glucose, ATP, and NADH was evaluated on intact brain sections by bioluminescence and fluorescence techniques. Additionally, the content of different substrates related to energy and redox state was assessed in small tissue samples. Recirculation following global ischemia led to three different patterns of biochemical substrates: in 6 of 14 animals, regional distribution of glucose, ATP, and NADH was similar to that of control animals. These animals exhibited recovery of evoked potentials and reappearance of low-voltage EEG activity. In five animals, ATP was decreased in small circumscribed regions belonging to border zones of cerebral vessels. In these regions, glucose was high and NADH-fluorescence was low, indicating that glucose deficiency was not the limiting factor for ATP depletion. In this group, evoked potentials recovered, but the EEG did not. In three animals, glucose and ATP were low throughout the whole brain, and electrophysiological recovery was absent. The pattern and localization of biochemical lesions and the correlation with hemodynamic and electrophysiological parameters suggest that disturbances of energy-producing metabolism are caused by regional ischemic episodes during the recirculation period and can be prevented by the immediate and homogeneous blood reperfusion of the brain after cerebrocirculatory arrest.

Adenosine Triphosphate↗
PubMed1981

A bioluminescence method for the demonstration of regional glucose distribution in brain slices.

Regional glucose distribution in brain slices was assessed by a bioluminescence technique. The reaction is based on light emission of luminiferous marine bacteria, Vibrio fischeri, induced by NADPH. Freeze-dried brain slices were covered by a solution which contained: (a) enzymes and substrates for glucose oxidation and NADPH formation and (b) an extract of Vibrio fischeri for the bioluminescence reaction. Glucose-induced bioluminescence was recorded on photographic film. Patterns of regional decrease in glucose concentration were demonstrated in cat brains after occlusion of the left middle cerebral artery. This decrease correlated well with a concomitant depletion of ATP and an increase in NADH-fluorescence.

Adenosine Triphosphate↗
PubMed1979

Aggregation of activated platelets with Walker 256 carcinoma cells.

Walker 256 carcinoma cells form irreversible aggregates with rat platelets activated by ADP or serotonin. Since serotonin induces platelet shape change but not platelet aggregation the degree of activation indicated by the disc-sphere transformation is sufficient for platelets to interact with these tumor cells. This is confirmed by experiments with spheroid washed platelets which form irreversible mixed aggregates with Walker 256 carcinoma cells without a stimulus being required. This type of tumor cells could react with platelets in vivo, provided the platelets are activated by disturbed blood flow or contact with subendothelium. Our observations can explain why other authors found no interaction between Walker 256 carcinoma cells and non-activated platelets in vitro even though platelets contributed to the formation of bloodborne metastases of this tumor.

Adenosine Diphosphate↗