Search PubMed⌕ Search

Biomedical subjects

W J Perkins

Publications and source records attributed to W J Perkins.

At least 19 recordsLinked to original sources
PubMed1991

Pretreatment with U74006F improves neurologic outcome following complete cerebral ischemia in dogs.

We examined the 21-aminosteroid U74006F, a potent inhibitor of lipid peroxidation, for potential neuroprotective effects in a canine model of complete cerebral ischemia. Two 1.5-mg/kg boluses were administered to six dogs, the first bolus 15 minutes prior to a 12-minute episode of complete cerebral ischemia and the second bolus after 11 minutes of ischemia, 1 minute prior to reperfusion. Using this dosage regimen, plasma U74006F levels of greater than 0.3 microgram/ml were maintained for up to an hour postischemia. An additional six animals received equal volumes of the citrate vehicle solution. At 24 and 48 hours postischemia, the dogs were neurologically evaluated by an observer blinded as to treatment selection. All six U74006F-treated animals had a normal neurologic outcome at 48 hours postischemia, while the citrate vehicle-treated animals all suffered moderate to severe neurologic deficits. The difference in outcome was significant at both 24 and 48 hours (p less than 0.005). Although U74006F is a 21-aminosteroid, it is not reported to possess glucocorticoid activity. This is supported by the present finding that no changes in plasma glucose concentration were observed following administration of the drug. The systemic vitamin E levels of citrate vehicle-treated animals decreased significantly (from 4.10 +/- 0.46 micrograms/ml to 2.95 +/- 0.38 micrograms/ml, p less than 0.05), whereas the vitamin E levels in U74006F-treated animals did not decrease significantly. These results suggest that U74006F may be of benefit in improving neurologic outcome when administered prior to an episode of complete cerebral ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

The effects of dizocilpine maleate (MK-801), an antagonist of the N-methyl-D-aspartate receptor, on neurologic recovery and histopathology following complete cerebral ischemia in primates.

The present study was designed to determine if the noncompetitive excitatory amino acid antagonist, dizocilpine maleate, when administered after a 17 min period of complete cerebral ischemia in primates, would improve postischemic neurologic function and hippocampal histopathologic outcome when compared to placebo-treated animals. Ten pigtail monkeys were anesthetized and subjected to complete cerebral ischemia using an established neck tourniquet model. Five minutes postischemia, five monkeys received dizocilpine 300 micrograms/kg i.v. over 5 min, followed by an infusion of 150 micrograms/kg/h for 10 h. This produced plasma levels of the drug in excess of 30 ng/ml for the duration of the infusion. An additional five monkeys were treated with an identical volume of saline placebo. All monkeys received intensive care for the initial 24 to 48 h postischemia. At 96 h postischemia, there was no significant difference in neurologic function between the two groups (p = 0.53, with the placebo group having the numerically better outcome). There also was no significant difference between hippocampal histopathology scores between dizocilpine and placebo-treated monkeys. The authors conclude that dizocilpine is not an efficacious therapy in the treatment of neurologic injury that occurs following complete cerebral ischemia in this primate model.

Animals↗
PubMed1990

Evaluation of a forced-air system for warming hypothermic postoperative patients.

Thirty adult surgical patients admitted to the recovery room with an oral temperature less than or equal to 35.0 degrees C were randomized into two groups. Group 1 patients were covered with cotton blankets warmed to 37.0 degrees C, and group 2 patients were treated with a forced-air warming system. Mean oral temperature on admission to the recovery room was the same in both groups (34.3 degrees C). Oral temperature and the presence or absence of shivering were recorded at 15-min intervals. After application of the selected warming method, patients in group 2 were warmer at all time intervals. Mean temperatures in the forced-air heating group and in group 1 were, respectively, 34.8 degrees C and 34.3 degrees C (P less than 0.05) at 15 min; 35.0 degrees C and 34.2 degrees C (P less than 0.01) at 30 min; 35.2 degrees C and 34.5 degrees C (P less than 0.05) at 45 min; 35.8 degrees C and 34.7 degrees C (P less than 0.001) at 60 min; 36.0 degrees C and 35.0 degrees C (P less than 0.01) at 75 min; and 36.0 degrees C and 35.0 degrees C (P less than 0.01) at 90 min. The incidence of shivering was significantly greater in group 1 at 15 and 45 min. In addition, time spent in the recovery room was significantly greater in group 1 than in group 2, 156.0 min versus 99.7 min (P less than 0.003).

Adult↗
PubMed1989

The effect of the excitatory amino acid receptor antagonist dizocilipine maleate (MK-801) on hemispheric cerebral blood flow and metabolism in dogs: modification by prior complete cerebral ischemia.

The effect of the N-methyl-D-aspartate (NMDA) receptor antagonist dizociplipine maleate (MK-801) on cerebral blood flow (CBF), cerebral metabolic rate for oxygen (CMRO2), intracranial pressure and systemic variables was examined in 6 normal dogs (Group I). In 6 additional dogs (Group II), the effects of a prior 11 min episode of complete cerebral ischemia on the response to dizocilipine was studied. CBF was measured with a sagittal sinus outflow technique and CMRO2 was calculated as the product of CBF and the arterial to sagittal sinus O2 content difference. Dizocilipine was administered as a 150 micrograms/kg i.v. bolus followed by a 75 micrograms.kg-1.h-1 infusion for 90 min. Plasma dizocilipine levels were greater than 25 ng/ml for the duration of the infusion. The CSF levels were approximately half the plasma levels. Five minutes after initiation of dizocilipine treatment, Group I dogs experienced a 63% increase in heart rate (P less than 0.01) and an 8% decrease in the mean arterial blood pressure (P less than 0.05). Over the same time interval. CBF increased by 85% (P less than 0.01) and intracranial pressure nearly doubled (P less than 0.05). In addition, dizocilipine treatment in all Group I animals resulted in EEG quasiperiodic bursts of delta-waves and polyspikes on a background of beta-activity. With the exception of the intracranial pressure, the above changes in systemic and cerebral variables persisted for the duration of the drug infusion. Intracranial pressure was no longer significantly elevated after 80 min of drug infusion. Hemispheric CMRO2 was unchanged by dizocilipine in Group I dogs. There was a decrease in the cortical glucose level at the end of the study, but no significant change in phosphocreatine, ATP, lactate, or energy charge when compared with 6 laboratory normals. An identical dose of dizocilipine administered after an 11 min episode of complete cerebral ischemia resulted in no significant changes in either cerebral or systemic variables. The absence of systemic effects in Group II dogs suggests that dizocilipine administration in normal dogs results in a centrally mediated activation of the peripheral sympathetic nervous system. The uncoupling of CBF and CMRO2 observed following dizocilipine treatment is similar to that reported for two other known NMDA antagonists, ketamine and phencyclidine. If administration of dizocilipine results in improved histopathological and neurological outcome following an episode of complete cerebral ischemia, this improvement is unrelated to changes in postischemic CBF or hemispheric CMRO2.

Animals↗
PubMed1989

Evaluation of the glutamate antagonist dizocilipine maleate (MK-801) on neurologic outcome in a canine model of complete cerebral ischemia: correlation with hippocampal histopathology.

This study was designed to determine if dizocilipine maleate (MK-801), administered following 11 min of complete ischemia in dogs, could favorably alter neurologic outcome and hippocampal damage. Eighteen dogs were anesthetized and subjected to complete cerebral ischemia by temporary occlusion of the ascending aorta and the venae cavae via a thoracotomy. Five min postischemia, 9 dogs were given dizocilipine 150 micrograms/kg, followed by an infusion of 1.25 microgram/kg/min for 8 h. Control dogs were given equal volumes of placebo. Dogs were evaluated neurologically at 24, 48, and 72 h; thereafter, the brains were perfused, fixed and harvested. There was no significant difference in outcome between dizocilipine- and placebo-treated dogs: 5 of 9 given dizocilipine were normal, 1 was mildly injured and 3 were severely injured or dead. In the control animals given placebo, 3 of 9 were normal, 2 were mildly injured and 4 were moderately to severely injured. Histopathologic examination was limited to the hippocampus. CA1 and CA2,3,4 pyramidal neurons were graded according to degree of injury on a 5-point scale. There were no differences in histopathologic grades between the two groups. However, in both groups combined there was a significant correlation between neurologic outcome grade and histopathologic grade. The only notable systemic effect of dizocilipine appeared to be prolonged sedation which extended beyond 24 h postischemia but was not evident at 48 h postischemia. The authors conclude that more outcome studies in more sensitive models are needed.

Animals↗
PubMed1984

Characterization of the properties of ethenoadenosine nucleotides bound or trapped at the active site of myosin subfragment 1.

The fluorescent nucleotide analogue of ADP, 1,N6-ethenoadenosine diphosphate (epsilon ADP), has been used to probe the active site of myosin subfragment 1 (SF1). The Mg complex of ADP was shown to be trapped stoichiometrically at the active site by a variety of thiol cross-linking agents having sulfur to sulfur spanning lengths of 2-14 A. Previous studies [Wells, J. A., & Yount, R. G. (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 4966-4970] had suggested ADP was trapped by direct closure of a postulated active site cleft by cross-linking two activity critical thiols, SH1 and SH2. This model was tested by measuring the polarization of trapped and reversibly bound epsilon ADP, the off-rate of trapped epsilon ADP, and the solute quencher accessibility of trapped epsilon ADP on SF1 modified with thiol cross-linking agents of different spanning lengths. The lack of correlation of all of these properties with the length of the cross-linking span suggests that trapping occurs by indirect stabilization of a conformation favoring bound nucleotides rather than by sterically preventing the release of nucleotide. Measurement of the fluorescent properties of epsilon ADP bound to SF1 vs. epsilon ADP free gave a 20% increase in emission intensity, a 7-nm blue shift in the emission maximum, and a 70% increase in the absorbance at the excitation wavelength (330 nm). Trapping of epsilon ADP by the thiol cross-linking agent p-phenylenedimaleimide gave a further 24% increase in emission intensity. This change was shown to be the result of an increase in absorbance of trapped epsilon ADP at 330 nm rather than an increase in the quantum yield.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylamides↗
PubMed1984

Introduction of a donor-acceptor pair by a single protein modification. Förster energy transfer distance measurements from trapped 1,N6-ethenoadenosine diphosphate to chromophoric cross-linking reagents on the critical thiols of myosin subfragment.

The fluorescent ADP analog, 1,N6-ethenoadenosine diphosphate (epsilon ADP), has been trapped at the active site of myosin subfragment 1 (SF1) by the chromophoric cross - linkers, 1,5 - difluoro - 2,4' - dinitrobenzene (F2DNB) and 4,4'-difluoro-3,3'-dinitrophenylsulfone (F2DPS). The cross-linking agents were shown to react with the kinetically reactive cysteines SH1 and SH2 (i) by virtue of their effect on the characteristic K+-EDTA and CaATPase activities of SF1, (ii) by the loss of two thiols after reaction of enzyme with equimolar concentrations of cross-linking agent, and (iii) by comparison of the uv absorption spectra of cross-linked SF1 with those of the thiol adducts of F2DPS and F2DNB. In addition, F2DPS was shown to be located predominantly on the 20 kDa heavy chain tryptic peptide fragment known to contain SH1 and SH2. The fluorescence decay of the epsilon ADP-SF1 complex was found to be heterogenous by phase modulation methods after reaction with the cross-linking reagents F2DPS and F2DNB. The resolved lifetimes were found to be 26.1 and 7.0 ns for the F2DPS system and 25.2 and 3.1 ns for the F2DNB system, indicating the presence of some free, as well as trapped and quenched, nucleotide in both systems. The shorter lifetimes (Förster energy transfer quenched) and the spectral overlap for the two systems were used to calculate distances of 26 A and 23 A between the purine binding site and the enzyme adducts of F2DPS and F2DNB, respectively. These distance measurements demonstrate that both SH1 and SH2 are too far from the active site to be directly involved in either the binding or the hydrolysis of ATP.

Adenosine Diphosphate↗
PubMed1983

Chemical inhibitors of phagosome-lysosome fusion in cultured macrophages also inhibit saltatory lysosomal movements. A combined microscopic and computer study.

The effects on lysosomal movements produced by the weak base ammonium chloride and by a representative polyanion poly-D-glutamic acid (PGA), previously reported to inhibit phagosome-lysosome (P-L) fusion, have been studied in cultured mouse macrophages using direct visual phase-contrast microscopy, a previously described (1, 3, 7) fluorescence assay of fusion, and computer analysis techniques. Treatment of the macrophages with 5-10 mM NH4Cl for 0.5-2 h or with 100 micrograms PGA/ml for 5 d caused a striking inhibition of saltatory lysosomal movements, as well as the expected inhibition of P-L fusion. Two other anionic fusion inhibitors tested, dextran sulphate and suramin, inhibited movements similarly. Removal of the NH4Cl from the cell medium reversed the lysosomal stasis and restored P-L fusion. Computer analyses of changes in lysosomal positions in treated and untreated macrophages during 2, 10, and 30-s intervals, using data from photomicrographs, computer graphics, and quantitative nearest-neighbour techniques developed for this purpose, supported the qualitative visual observation of the inhibition of lysosomal movements by the fusion inhibitors NH4Cl and PGA. Over the chosen intervals, from 80 to 96% of the lysosomes could be paired within 1 micron of each other in the NH4Cl- and PGA-treated cells in comparison with 50-70% in normal cells. The differences between the drug-treated and normal cells were highly significant. In an analogous system, the lysosomal stasis induced by hypertonic sucrose was examined and it was observed that P-L fusion too was inhibited. Both effects were reversible. We conclude that inhibition of P-L fusion and of lysosomal movement are associated. We suggest a causal relationship between these changes, namely, that the lysosomotropic inhibitors of fusion under study produce their effects largely, though perhaps not exclusively, by reducing saltatory lysosomal motion and consequently periphagosomal assembly, rather than directly and independently on P-L contact or on the fusion process itself. The possibility is raised that microtubules may be involved in the effector mechanism of these modulations.

Acridine Orange↗
PubMed1979

A system for the three-dimensional construction, manipulation and display of microbiological models.

A system is described for building up serial sections into a three dimensional structure, incorporating density, that can be displayed and then further manipulated by rotation about three orthogonal axes. The initial application was to produce a computer model of a protein structure and to compare the diverse images obtained from rotation with the two dimensional images observed in related electron micrographs. To obtain sufficient contrast in the electron microscope images of protein structures, the specimens need to be stained and since this can cause some deformation of the observed images, it is also necessary to simulate ths possible effects of stain on the protein model. Because of the need to compare numerous orientations of the combined model, techniques are available either for speeding up the comparison or for obtaining better accuracy. The methods have been applied to the interpretation of electron micrograph images of microbiological specimens, where the three dimensional structure of the specimen is an important aid in understanding its biological function, but the techniques are also applicable to more general serial reconstruction requirements.

Adenoviridae↗
PubMed1979

The transfer of selected image data to a computer using a conductive tablet.

The processing and analysis of images in a computer often requires the selection of particular features of a complex image for more detailed study. Sometimes such decisions are empirical, in which case it would be extremely difficult to describe a rigorous algorithm for detecting these features automatically in a computer. In this situation graphic tablets can be very useful as they allow an operator to use experience in deciding which features are to be transferred into a computer. A tablet is described which uses a conductive glass plate and pencil probe. A number of subroutines are available in a general purpose program for conventional processing, calculation and displays to be effected by simple option selection on the tablet for specific applications in cell growth, modeling and three dimensional reconstruction of serial sections, special programs were developed which could include appropriate subroutines. The categorisation of subsections by an operator was particularly useful in allowing different methods of analysis and display to be applied to each. For example they could be displayed separately or given different dentisy levels by choosing the appropriate option in the program.

Analog-Digital Conversion↗