Biomedical subjects

J E Fletcher

Publications and source records attributed to J E Fletcher.

At least 91 records · Page 5Linked to original sources

PubMed1991

Psychomotor performance after desflurane anesthesia: a comparison with isoflurane.

Recovery and psychomotor performance were studied in 80 ASA physical status I-III adult patients undergoing outpatient surgery. Patients were divided into four equal groups: thiopental induction of anesthesia followed by desflurane in nitrous oxide and oxygen (Th-DES-N2O/O2), thiopental induction of anesthesia followed by isoflurane in nitrous oxide and oxygen (Th-ISO-N2O/O2), thiopental induction of anesthesia followed by desflurane in oxygen (Th-DES-O2), and desflurane inhaled induction followed by desflurane in oxygen (DES-DES-O2). Patients were excluded from analysis if they required opioids or antiemetics postoperatively. The use of desflurane was associated with more rapid awakening compared with isoflurane (time to eye opening 9.45 +/- 0.67 min [Th-DES-N2O/O2] and 13.8 +/- 1.59 min [Th-ISO-N2O/O2], P less than 0.05). Psychomotor performance was measured using the choice reaction time and critical flicker fusion threshold. At 30 min after discontinuing anesthesia, five patients in the Th-ISO-N2O/O2 group and one patient in the Th-DES-N2O/O2 group were too sleepy to perform psychomotor tests. In addition, five patients who received Th-DES-O2 and one patient who received the inhaled induction and maintenance of anesthesia with desflurane in oxygen were too sleepy to perform tests at 30 min. Patients receiving Th-DES-N2O/O2 showed less impairment of choice reaction time than those receiving Th-ISO-N2O/O2. Critical flicker fusion threshold, however, showed no difference between groups. The use of thiopental was associated with delayed recovery. Compared with isoflurane, desflurane anesthesia is associated with more rapid initial awakening and less impairment of choice reaction time.

Adult↗

PubMed1991

Comparison of ocfentanil and fentanyl as supplements to general anesthesia.

Three doses of ocfentanil (1, 3, and 5 micrograms/kg), a new narcotic, were compared with fentanyl (5 micrograms/kg) as a supplement to general anesthesia. Sixty adult ASA I-III patients undergoing elective surgery were studied. The drugs were given as a bolus injection during induction of anesthesia in a double-blind manner. With the stimulus of tracheal intubation, systolic arterial blood pressure increased (mean +/- SE) from 127 +/- 6.9 to 183 +/- 7.4 mm Hg and heart rate increased from 82.1 +/- 4.8 to 104 +/- 6.4 beats/min in patients who had received 1 microgram/kg of ocfentanil intravenously. In comparison to patients who received 1 microgram/kg of ocfentanil, the increases in heart rate and systolic arterial blood pressure at the time of tracheal intubation were less with 3 and 5 micrograms/kg of ocfentanil and 5 micrograms/kg of fentanyl (P less than 0.05). At incision, heart rate decreased after the intravenous administration of 5 micrograms/kg of ocfentanil when compared with patients who received 1 microgram/kg of ocfentanil. There were differences between study groups in the mild increase in arterial blood pressure observed at incision. The authors conclude that ocfentanil and fentanyl appear to be similar in action, with 3 micrograms/kg of ocfentanil being approximately equivalent in effect to 5 micrograms/kg of fentanyl.

Adjuvants, Anesthesia↗

PubMed1991

Altered [3H]ryanodine binding is not associated with malignant hyperthermia susceptibility in terminal cisternae preparations from swine.

Based on comparisons between Pietrain malignant hyperthermia susceptible swine and Yorkshire control swine, other investigators have reported a 3-fold lower Kd for [3H]ryanodine binding to terminal cisternae in the malignant hyperthermia swine. However, the Kd of [3H]ryanodine binding did not correlate with malignant hyperthermia susceptibility when examined within the same strain (a Yorkshire/Duroc cross) in the present study. The values of Kd for the malignant hyperthermia susceptible and control swine in the present study were similar to those previously reported for the Pietrain strain, suggesting that the control strain chosen, not malignant hyperthermia susceptibility, accounts for what appeared to be a low Kd in Pietrain muscle.

Animals↗

PubMed1990

The binding of palmitoyl-CoA to bovine serum albumin.

Bovine serum albumin (BSA) is routinely utilized in vitro to prevent the adverse detergent effects of long-chain acyl-CoA esters (i.e., palmitoyl-CoA) in enzyme assays. Determination of substrate saturation kinetics in the presence of albumin would only be valid if the relationship between bound and free substrate concentrations was known. To elucidate the relationship between bound and free palmitoyl-CoA concentrations in the presence of BSA, several different techniques including equilibrium dialysis, equilibrium partitioning, fluorescence polarization and direct fluorescence enhancement were investigated. Direct fluorescence enhancement using a custom synthesized fluorescent probe, 16-(9-anthroyloxy)palmitoyl-CoA (AP-CoA), was the best approach to this question. Measurement of the relationship between mol of palmitoyl-CoA bound per mol of BSA (nu) versus -log[free palmitoyl-CoA] revealed that the binding of palmitoyl-CoA to BSA, like palmitate was nonlinear, suggesting the presence of more than one class of acyl-CoA binding sites. Computer analyses of the binding data gave a best fit to the 2,4 two-class Scatchard model, suggesting the presence of two high-affinity primary binding sites (k1 = (1.55 +/- 0.46) x 10(-6) M-1) and four lower affinity secondary binding sites (k2 = (1.90 +/- 0.09) x 10(-8) M-1). Further analyses using the six parameter stoichiometric (stepwise) ligand binding model supports the existence of six binding sites with the higher affinities associated with the binding of the first mole of palmitoyl-CoA and weaker binding occurring after the first two sites are occupied. The association constants from this model of multiple binding diminish sequentially (i.e., K1 greater than K2 greater than K3 greater than...greater than or equal to K6), suggesting that each mol of long-chain acyl-CoA binds to BSA with decreasing affinities.

Acyl Coenzyme A↗

PubMed1990

Gene candidate.

Explore the source record for details and available documents.

Chromosomes, Human, Pair 19↗

PubMed1990

The importance of calcium ions for in vitro malignant hyperthermia testing.

Intracellular Ca++ levels in skeletal muscle are elevated during the in vitro contracture response of muscle from subjects with malignant hyperthermia. The role of Ca++ in the bathing medium and the consequences of substitution of Sr++ for Ca++ in the response to agents associated with malignant hyperthermia were examined. When Ca++ was omitted from the bathing medium the contractures induced in human vastus lateralis by halothane (three per cent) or succinylcholine (50 mM) were reduced by 80 and 100 per cent, respectively, while contractures induced by caffeine (8 mM) were only reduced by 50 per cent. Substitution of Ca++ by another divalent cation, Sr++, completely restored contractures induced by caffeine, but only partially restored contractures induced by halothane or succinylcholine (to 50 and 30 per cent of Ca(++)-containing medium, respectively). Mepacrine (10 microM) was effective in antagonizing contractures by caffeine, whereas verapamil and nifedipine (10 microM) were not. These results support an essential role for extracellular Ca++ not fulfilled by Sr++ in contracture induction by halothane and succinylcholine, but not by caffeine.

Caffeine↗

PubMed1990

Contribution of bee venom phospholipase A2 contamination in melittin fractions to presumed activation of tissue phospholipase A2.

Melittin from bee venom has been suggested to activate tissue phospholipase A2 (PLA2) activity, and subsequently has been used as a specific PLA2 probe. The melittin in most cases was obtained commercially and used without further purification or treatment. To test the hypothesis that commercially obtained melittin specifically activates tissue PLA2, we radiolabeled the lipids of immortalized epithelial cells by incubating the cells for 22 hr with 14C-linoleic acid. The cells were then incubated with 2 microM melittin, 2nM bee venom PLA2, 2 microM melittin treated with p-bromophenacyl bromide (p-BPB) or PLA2 plus p-BPB-treated melittin. Lipids were extracted and separated by thin-layer chromatography. The radioactivity in each lipid fraction was then quantitated. The melittin-stimulated PLA2 activity observed in cells was primarily associated with phosphatidylcholine. Fatty acid release was decreased by 75% when the melittin fraction was pretreated with p-BPB to reduce contaminating venom PLA2 activity. Adding PLA2 to the p-BPB-treated melittin at an amount about equal to the original contamination (0.1%) resulted in the same PLA2 activity in cell as observed with the untreated melittin fraction. These findings suggest that bee venom PLA2 contamination, even at very low levels, can account for approximately 75% of the PLA2 activity in cells treated with commercial melittin fractions.

Acetophenones↗

PubMed1990

Interactions in red blood cells between fatty acids and either snake venom cardiotoxin or halothane.

Phospholipase A2 (PLA2) activity enhances snake venom cardiotoxin (CTX)-induced and general anesthetic (halothane)-induced hemolysis of red blood cells. In the case of halothane-induced hemolysis, this effect appears to be related primarily to free fatty acids. In the present study, the interaction between CTXs and halothane and the effects of different free fatty acids on cardiotoxin and halothane-induced hemolysis were examined. The hemolytic actions of halothane and a CTX from Naja naja kaouthia venom were examined in erythrocytes with different phospholipid and free fatty acid composition from five species. The extent of hemolysis by CTX or halothane was dependent upon the species examined and appeared to be inversely related to the amount of saturated free fatty acid in the membrane. The order of susceptibility of red blood cells from five species to hemolysis was similar for halothane- and N. n. kaouthia CTX-induced hemolysis, but very different for osmotic fragility. The slope of the hemolysis dose-response curve was considerably steeper for halothane than for CTX. Hemolysis due to N. n. kaouthia CTX was greatly increased by halothane in erythrocytes from humans and horses and to a lesser extent in erythrocytes from sheep, goats and cows. Hemolysis induced by halothane and the N. n. kaouthia or Naja naja atra CTXs was enhanced by unsaturated fatty acids. In contrast, hemolysis induced by halothane was decreased and that caused by the two CTXs was relatively unaffected by saturated fatty acids. Halothane and CTXs differ in their exact mechanisms, but appear to act upon similar fatty acid-sensitive processes.

Animals↗

PubMed1990

Caffeine and halothane contracture testing in swine using the recommendations of the North American Malignant Hyperthermia Group.

Caffeine and halothane contracture testing is widely used to detect malignant hyperthermia (MH) susceptibility. The accuracy and reliability of the 3% halothane test and the incremental caffeine test, as recommended by the North American MH Group, were assessed in 11 swine (five MHS, six control). Nine swine were tested twice, 4-6 weeks apart. Accuracy of the in vitro diagnosis was also assessed by in vivo anesthetic challenge. Of all muscle bundles from MH-susceptible swine, 65% reacted positively to 3% halothane and 70% to 2 mM caffeine. Only 35% had a positive caffeine-specific concentration, and 25% developed an increase in baseline tension greater than or equal to 7% at 2 mM caffeine. However, when only the most positive response to 3% halothane or to 2 mM caffeine was used (a minimum of three fresh muscle strips is recommended), these two tests were highly sensitive and specific. In control swine one of 30 muscle bundles reacted positively to 3% halothane. A positive caffeine-specific concentration developed in one of 25 control muscle bundles exposed to caffeine. The variability in the results of these tests mandated that at least three muscle bundles be used for each test. Nonviable muscle bundles could not be relied upon to provide accurate results. In this porcine model, MH susceptibility could be detected by performing the Caffeine Halothane Contracture Test (CHCT) according to the guidelines of the North American MH Group. However, only the 3% halothane test and the response to 2 mM caffeine produced adequate diagnostic results in this breed of swine.

Animals↗

PubMed1990

Safety of general anesthesia in patients previously tested negative for malignant hyperthermia susceptibility.

Anesthetic management and outcome were examined in patients with negative in vitro contracture tests for malignant hyperthermia (MH). Contracture testing was performed in a standardized fashion using 3% halothane alone and incremental doses of caffeine alone. Medical records were examined for 54 anesthetic exposures in 42 MH(-) patients who had received anesthesia since their MH testing. Sixteen patients received anesthesia with known MH triggering agents on 23 occasions, all without incident. In six MH(-) patients with previous masseter muscle rigidity, no adverse reactions occurred in response to volatile anesthetic agents. Succinylcholine was avoided in these patients. Eleven MH(-) patients were managed as if MH-susceptible, although it was known that these patients had tested MH(-). Two of these patients also receive prophylactic iv dantrolene. These results suggest that "triggering" anesthetic agents may be safely administered to patients who test MH(-) by in vitro contracture testing. However, until the anesthetic experience of larger numbers of MH(-) patients is known, these results should be interpreted cautiously.

Anesthesia, General↗

PubMed1990

Calcium accumulation by sarcoplasmic reticulum in whole muscle homogenate preparations of malignant hyperthermia diagnostic patients and pigs.

Calcium accumulation by the sarcoplasmic reticulum in whole muscle homogenate preparations of malignant hyperthermia-susceptible (MH+) and non-susceptible (MH-) humans and pigs was investigated using a calcium electrode at 35 degrees C. Sarcoplasmic reticulum of MH+ humans and pigs showed normal Ca2+ accumulation, with no difference being observed in the rate and the time taken to achieve maximal accumulation. However, the capacity for Ca2+ accumulation by the sarcoplasmic reticulum in MH+ humans and pigs is considerably less stable than normal after prolonged ageing of the whole muscle homogenate preparations in ice. In MH+ patients, the capacity for Ca2+ accumulation by the sarcoplasmic reticulum showed a decline of 62% at 22 h ageing and 70% at 48 h ageing, as compared with a reduction of only 23% in MH- patients. In MH+ pigs, the sarcoplasmic reticulum showed a 96% deterioration in the capacity for Ca2+ accumulation as compared with a loss of only 40% in MH- pigs at 7 h ageing in ice. In both humans and pigs, the decline in Ca2+ accumulation was prevented by incubating the whole muscle homogenate preparations for 2 h at 35 degrees C prior to ageing the preparations. The diminished Ca2+ accumulating capacity of the sarcoplasmic reticulum in whole muscle homogenate preparations of MH-susceptible individuals in our experimental protocol provides a potential diagnostic test for malignant hyperthermia susceptibility.

Animals↗

PubMed1990

Importance of fasting in the lymphocyte calcium test for malignant hyperthermia.

Anaesthetic-induced increases in cytoplasmic free Ca2+ have been reported to be greater in lymphocytes from malignant hyperthermia (MH) susceptible patients than in those from controls, suggesting that this may be the basis for a less invasive test for MH susceptibility. In the present study the cytoplasmic Ca2+ concentrations of lymphocytes were monitored with indo-1 in 14 control subjects (nine fasted and five nonfasted) and five fasted MH susceptible and three fasted nonsusceptible patients, diagnosed by the halothane and caffeine contracture tests. No relationship was observed between MH susceptibility and Ca2+ concentrations in lymphocytes in the absence or presence of halothane. There was, however, a relationship in control subjects between fasting and the response of lymphocytes to halothane, with the halothane-induced Ca2+ increase being considerably larger in nonfasted subjects.

Adolescent↗

PubMed1990

Fatty acids modulate calcium-induced calcium release from skeletal muscle heavy sarcoplasmic reticulum fractions: implications for malignant hyperthermia.

Based on studies in swine, the malignant hyperthermia syndrome has been postulated to result from an enhanced sensitivity (low threshold) of the Ca2(+)-induced Ca2(+)-release process. However, fatty acid production is elevated in homogenates of skeletal muscle from pigs and humans susceptible to malignant hyperthermia. In the present study, we demonstrate that the threshold of Ca2(+)-induced Ca2+ release is normal in susceptible humans and in susceptible swine depleted of triglycerides. Exogenously added unsaturated fatty acids decreased the threshold of Ca2(+)-induced Ca2+ release to a much greater extent in porcine and equine muscle than in human muscle. When triglyceride and free fatty acid values were reduced to about 40 and 60%, respectively, of control values, malignant hyperthermia-susceptible swine did not exhibit muscle rigidity when challenged in vivo with halothane and succinylcholine and the threshold of the Ca2(+)-induced Ca2(+)-release process in heavy sarcoplasmic reticulum fractions was normal. Despite the reduced triglyceride and fatty acid levels, these swine had a positive in vitro contracture test for malignant hyperthermia. A low Ca2(+)-induced Ca2(+)-release threshold is not essential for malignant hyperthermia susceptibility, but appears to be the result of excessive free fatty acids produced during organelle isolation.

Animals↗

PubMed1990

Fatty acid uptake and catecholamine-stimulated phospholipid metabolism in immortalized airway epithelial cells established from primary cultures.

The incorporation of [14C]oleic and [14C]linoleic acid into phospholipids and neutral lipids was compared in two recently immortalized airway epithelial cell lines. In addition, the effects of adrenergic stimulation on phospholipid turnover was examined. Both cell lines readily incorporated the fatty acids into all phospholipid and neutral lipid fractions. Isoproterenol (1 microM) induced Ca2+ transients in both cell lines, indicating a functional beta-adrenergic response. Epinephrine (10 microM; 15 min) stimulation of cells prelabeled with [14C]linoleic acid increased the percentage of label in phosphatidylcholine in one cell line. Lipid metabolism can now be extensively studied in human airway epithelia.

Calcium↗

PubMed1990

A modeling analysis of monoclonal antibody percolation through tumors: a binding-site barrier.

For successful use of radiolabeled monoclonal antibodies (MAbs) for diagnosis and therapy, it is helpful to understand both global and microscopic aspects of antibody biodistribution. In this study, antibody distribution in a tumor is simulated by splicing together information on global pharmacokinetics: transport across the capillary wall, diffusive penetration through the tumor interstitial space, and antigen-antibody interaction. The geometry simulated corresponds to spherical nodules of densely packed tumor cells. This modeling analysis demonstrates that: 1) antigen-antibody binding in tumors can retard antibody percolation; 2) high antibody affinity at a given dose tends to decrease antibody percolation because there are fewer free antibody molecules. The result is a more heterogeneous distribution; 3) the average antibody concentration in the tumor does not increase linearly with affinity; and 4) increasing antibody dose leads to better percolation and more uniform distribution. This mathematical model and the general principles developed here can be applied as well to other biologic ligands.

Antibodies, Monoclonal↗

PubMed1989

Modeling analysis of the global and microscopic distribution of immunoglobulin G, F(ab')2, and Fab in tumors.

In order to understand the pharmacology of monoclonal antibodies and their conjugates, one must consider both global and microscopic aspects of antibody distribution. Here we present an analysis of antibody distribution in tumors based on the following factors: (a) molecular weight and valence of the antibody; (b) global pharmacokinetic profile following i.v. bolus injection; (c) penetration through the vascular wall; (d) diffusive and convective transport through interstitial space in the tumor; (e) antigen-antibody interaction; (f) antibody metabolism. Partial differential equations were developed to incorporate these factors and then solved numerically using parameter values from animal experiments, from clinical protocols at our institution, from studies of antibody binding characteristics in vitro, and from the literature. Salient findings from this model are that (a) antigen-antibody interaction in the tumor can retard antibody percolation away from blood capillaries, thus constituting a "binding site barrier"; (b) high antibody affinity tends to decrease antibody penetration and result in a more heterogeneous distribution; (c) high molecular weight [IgG greater than F(ab')2 greater than Fab] slows percolation and results in less uniform spatial distribution; (d) the average antibody concentration in the tumor does not increase linearly with antibody dose; (e) raising the rate of antibody metabolism results in low concentration and poor percolation; (f) perhaps most interesting, there is predicted to be a range of antibody dose and affinity within which the specificity ratio and average concentration could be kept high while limiting the heterogeneity of distribution. PERC, the computer program package developed for these analyses, provides a convenient and flexible way to assess the impact of global and microscopic parameters on the distribution of immunoglobulin in tumors. For calculations presented here, the input data were obtained from experimental sources, and qualitative features of the output proved consistent with the few interpretable observations available. However, detailed validation would require much more data than are currently at hand. The mathematical findings should therefore be considered as aids to concept development and as a set of null hypotheses with which to guide experimentation. Experiments and simulations will continue in tandem. It should be noted that the PERC package (and also the general principles delineated here) can be applied as well to biological ligands other than antibodies.

Antibody Affinity↗

PubMed1989

Skeletal muscle mitochondrial respiration of malignant hyperthermia-susceptible patients. Ca2+-induced uncoupling and free fatty acids.

1. Skeletal muscle mitochondria of malignant hyperthermia (MH)-susceptible patients showed normal oxidative phosphorylation but were more easily uncoupled than normal by exogenous Ca2+. 2. Fatty acids, in stimulating the mitochondrial ATPase activity, are responsible for the enhanced State 4 respiration in MH-susceptible patients. 3. These results imply that skeletal muscle mitochondria and free fatty acids are associated with the development of MH syndrome.

Calcium↗

PubMed1989

Effects of divalent cations on snake venom cardiotoxin-induced hemolysis and 3H-deoxyglucose-6-phosphate release from human red blood cells.

At a low concentration of Naja naja kaouthia cardiotoxin (3 microM) Ca2+, Sr2+ and Ba2+ (2 mM), had little to no effect on 3H-deoxyglucose-6-phosphate (3H-dGlu-6-p) or hemoglobin release. At higher concentrations of N. n. kaouthia cardiotoxin (greater than or equal to 10 microM), Ca2+ (2 mM), but not Sr2+ or Ba2+, significantly enhanced 3H-dGlu-6-p and hemoglobin release. Mn2+ (2 mM) almost completely inhibited 3H-dGlu-6-p release and hemolysis at both the 3 microM and 10 microM concentrations of cardiotoxin. At a fixed concentration of N. n. kaouthia cardiotoxin (3 microM). Ca2+ at low concentrations (0.5 mM) enhanced 3H-dGlu-6-p and hemoglobin release, but at higher concentrations caused a dose-dependent inhibition of cardiotoxin action. The cardiotoxin from N. n. kaouthia venom (3 microM) induced 3H-dGlu-6-p release and hemolysis release with similar time courses and to similar extents. 3H-dGlu-6-p release induced by cardiotoxin was greatly enhanced as the pH of the medium was increased from 7.0 to 8.5. Similarities between 3H-dGlu-6-p and hemoglobin release do not support opening of pores in the plasmalemma of all red blood cells as the mode of action of cardiotoxins, but suggests that complete lysis of a subpopulation of cells occurs. Cardiotoxins have two components of lysis, only one of which is Ca2+-dependent. The Ca2+-dependent lysis is only evident at higher cardiotoxin concentrations and is likely due to trace phospholipase A2 contamination in the toxin fraction. Mn2+ is an effective antagonist of cardiotoxin action.

Barium↗