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Biomedical subjects

L Brown

Publications and source records attributed to L Brown.

At least 253 records · Page 14Linked to original sources
PubMed1990

[Hypoxemia after general anesthesia in healthy adults].

It has been shown that a variable percentage of patients who receive a general anesthetic are significantly hypoxemic when they arrive at the recovery room. Pulse oximetry has proved to be a reliable method to determine arterial oxygen saturation when compared to arterial or mixed venous blood oxygen saturation measurements. The authors determined the incidence and severity of hypoxemia by pulse oximetry in 45 healthy adult patients, (non obese, non smokers) who underwent non thoracic surgery under general anesthesia. Arterial oxygen saturation was measured without premedication before surgery (control), when they arrived at the recovery room, and 5 and 15 minutes later. The axillary temperature was taken at the same times. The results were expressed as the median and standard deviation and were analyzed with Student T Test, and p LO.05 was considered significant. Nine patients (20%) showed unacceptable oxygen saturation when they arrived at the recovery room (88.4 +/- 2.50%, LO.05). All patients showed significant hypothermia (35.3 +/- 0.54 degrees C). The authors conclude that a significant number of healthy adult patients who are given a general anesthetic show severe hypoxemia when they arrive at the recovery room. The severe hypothermia found in these patients can aggravate the hypoxemia. They consider it is mandatory to control the temperature of and to administer oxygen in the recovery room to all patients who receive a general anesthetic.

Adult↗
PubMed1989

Abnormal brain-stem function (brain-stem auditory evoked response) correlates with acoustic cry features in term infants with hyperbilirubinemia.

We hypothesized that changes in brain-stem auditory evoked responses related to bilirubin would be associated with changes in cry because of the anatomic proximity in the brain stem of cranial nerves 8 (auditory) and 9 to 12 (vagal complex, which controls cry). Brain-stem auditory evoked responses and computerized cry analysis were used to study the concurrent effects of moderate hyperbilirubinemia on auditory function and cry. Fifty term infants were divided equally into two groups on the basis of serum bilirubin concentrations: low (less than 8 mg/dl; 136) mumol/L and moderate (10 to 20 mg/dl, 170 to 342 mumol/L). Forty-three infants had successful tracings of brain-stem auditory evoked responses recorded with a Cadwell model 5200A evoked response unit during two successive trials, and a cry recording of each infant was analyzed by computer. The moderate serum bilirubin group had an increase in percent cry phonation (p less than 0.02) and an increase in the variability of the first formant (p less than 0.04) in comparison with the low serum bilirubin group. Serum bilirubin values correlated positively with brain-stem conduction time (r = 0.36, p less than 0.01), percent phonation (r = 0.42, p less than 0.004), and variability of the first formant (r = 0.39, p less than 0.02). Percent phonation, the voiced component produced by increased neural control, correlated with the interpeak of waves latencies I to III (r = 0.32, p less than 0.03) and brain-stem conduction time (wave I to V) (r = 0.35, p less than 0.01). We conclude that hyperbilirubinemia affects adjoining areas of the brain stem that control hearing and cry production.

Brain Stem↗
PubMed1989

Do not resuscitate discussions in a hospital-based home care program.

Discussion of code status of a patient is usually raised in the inpatient setting, when patients are unable to participate because of their critical condition. In order to increase patient participation, code status was discussed in the homes of 37 chronically ill patients enrolled in a hospital-based home care program. Twenty patients or conservators did not want resuscitation performed in case of cardiac arrest. In this small, select group, outpatient code discussions benefited the patients, families, and health care providers.

Aged↗
PubMed1989

Comparison of a new rapid test (TestPack Rotavirus) with standard enzyme immunoassay and electron microscopy for the detection of rotavirus in symptomatic hospitalized children.

We compared a new, rapid, qualitative test for rotavirus (TestPack Rotavirus; Abbott Laboratories, North Chicago, Ill.) with another enzyme immunoassay (Pathfinder Rotavirus; Kallestad Laboratories, Inc., Austin, Tex.) and electron microscopy to determine its clinical utility in a population of symptomatic hospitalized children. In the first part of the study, 100 frozen stool samples were tested. The results after resolution with a blocking reagent showed a sensitivity of only 50% and a specificity of 88% for TestPack Rotavirus. In the second part of the study, we tested TestPack Rotavirus on 100 fresh, unfrozen samples. The results (sensitivity/specificity) were as follows: TestPack Rotavirus, 95/90%; Pathfinder Rotavirus, 84/98%; direct electron microscopy, 63/100%. Although it was not as sensitive or specific as immune electron microscopy, TestPack Rotavirus was more sensitive than direct electron microscopy or Kallestad Pathfinder Rotavirus. TestPack Rotavirus represents a rapid, qualitative method for the detection of rotavirus in stools of symptomatic children.

Child↗
PubMed1989

Anomaly in western blot band intensities perceived by visual inspection.

Quantitation of Western blots from polyacrylamide gels is commonly accomplished by either visual inspection or densitometry. However, due to absorption of protein and staining reagents by the blotting membrane it is possible that visual inspection and reflectance densitometry will given anomalous results. In this paper we show such an example, and discuss how transmission densitometry can provide more accurate results.

Blotting, Western↗
PubMed1988

A pharmacological analysis of the rat spinal cord serotonin (5-HT) autoreceptor.

The pharmacological characteristics of the presynaptic 5-HT receptor associated with the modulation of 5-HT release were investigated in a preparation of rat spinal cord synaptosomes (nerve terminals) superfused with a Tris-buffered Krebs solution containing fluoxetine (1 microM). The 5-HT receptor agonists serotonin (1-100 nM), lysergic acid diethylamide (10 nM-1 microM) and the 5-HT1B receptor agonists 1-(m-trifluoromethylphenyl)piperazine (100 nM-1 microM) and 1-(m-chlorophenyl) piperazine (100 nM-3 microM) concentration dependently decreased [3H]5-HT release, while 8-hydroxy-2-(di-n-propylamino)tetralin, a selective 5-HT1A receptor agonist, was inactive. The actions of the effective agonists were reversed by quipazine, an antagonist with high affinity for 5-HT1B binding sites, but not by spiperone, a 5-HT1A receptor antagonist. Furthermore, mesulergine, a 5-HT1C receptor antagonist was ineffective in reversing the action of 5-HT on [3H]5-HT release. These data indicate that the rat spinal cord nerve terminal autoreceptor has characteristics similar to the 5-HT1B binding site.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1988

Positive inotropic effects of the calcium channel activator Bay K 8644 on guinea-pig and human isolated myocardium.

1. The positive inotropic effects of the dihydropyridine calcium activator Bay K 8644 were studied in guinea-pig isolated contracting myocardium and human papillary muscle strips obtained from patients undergoing mitral valve replacement or cardiac transplantation. 2. Bay K 8644 produced a slowly developing, concentration-dependent positive inotropic response in all cardiac tissues studied. In guinea-pig papillary muscle, the increase in force of contraction was half-maximal at 3.9 x 10(-8) mol/l and the maximal inotropic effect was comparable to that obtained with ouabain, dobutamine or calcium. The guinea-pig left atrium (EC50, 2.1 x 10(-7) mol/l) was fivefold less sensitive than the papillary muscle. 3. The maximal inotropic response to dihydroouabain was significantly increased after preincubation with Bay K 8644 (1 x 10(-6) mol/l) in papillary muscles from both guinea-pig and human. In guinea-pig papillary muscles, the maximal inotropic response to dobutamine was not changed by preincubation with Bay K 8644 whereas in human papillary muscle strips, Bay K 8644 increased the inotropic response to dobutamine. 4. Bay K 8644 increased force of contraction (EC50, 4 x 10(-8) mol/l) in human papillary muscle strips from patients undergoing mitral valve replacement. However, the maximal inotropic response to Bay K 8644 was reduced to 32 +/- 4.4% that of calcium (15 mmol/l) measured in the same muscle strips. 5. A further reduction in maximal inotropic response to Bay K 8644 to 13 +/- 1.2% that of calcium (15 mmol/l) with no change in potency was measured in human papillary muscle strips taken from terminally failing hearts of cardiac transplant recipients.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1988

Inverse relationship between colonic (Na+ + K+)-ATPase activity and degree of mucosal inflammation in inflammatory bowel disease.

In inflammatory bowel disease (IBD), mucosal damage and loss of colonic function are regarded as major consequences of inflammation. Decreased colonic (Na+ + K+)-ATPase activities with diminished reabsorption of sodium and water have been found in active stages of ulcerative colitis. In this study, we report an inverse relationship between colonic (Na+ + K+)-ATPase activity and the degree of mucosal inflammation in 19 patients with IBD of mild to moderate disease activity. Various macroscopic and histologic types of mucosal lesions were differently associated with the (Na+ + K+)-ATPase activities. 5'-nucleotidase activity was not associated with the degree of mucosal inflammation or the kind of macroscopic or histologic lesions. Our findings support the view that, in contrast to 5H-nucleotidase, (Na+ + K+)-ATPase activity may better reflect the severity of mucosal damage and the degree of inflammation in IBD.

5'-Nucleotidase↗
PubMed1988

Comparison of a protein-stabilized Rotazyme II test, with standard Rotazyme II, and electron microscopy for detection of rotavirus.

We compared the performance of Rotazyme II with protein-stabilized diluent to standard Rotazyme II and to direct electron microscopy, for the detection of rotavirus. Sensitivity and specificity were: standard Rotazyme II, 79 and 100%, respectively; Rotazyme II with protein stabilizers, both 100%, and electron microscopy, 75 and 100%, respectively. Commercial availability of this product should improve rotavirus detection for laboratories utilizing Rotazyme II methodology.

Child↗
PubMed1988

Enzymatically controlled drug delivery.

An approach for providing feedback control for polypeptide drugs in a polymeric controlled-release system uses a trigger molecule and a polymer-bound enzyme that, in the presence of that trigger molecule, will cause an acid or a base to form. When the pH inside the polymer system changes, the solubility of the drug shifts dramatically, which changes the diffusion or dissolution driving force, and hence the release rate changes correspondingly. This concept was tested using a controlled-release system of ethylene/vinyl acetate copolymer containing insulin and immobilized glucose oxidase. The enzymatic reaction of glucose to gluconic acid reduces the pH in the polymer microenvironment. Since insulin solubility increases with decreasing pH (at physiologic pH, this is true for an insulin with an isoelectric point of 7.4 or higher), the release of insulin increases in response to glucose concentration. The feasibility of this concept has been shown using trilysyl insulin with an isoelectric point of 7.4. Multiple exposures to buffered glucose solutions over several weeks caused insulin release to reversibly increase during each exposure. Polymer-implanted diabetic rats infused with glucose solutions showed a significant increase in insulin concentration in 30 min-an effect not observed in three different sets of control rats.

Animals↗
PubMed1988

The risk of cytomegalovirus infection in seronegative transfusion recipients not receiving exogenous immunosuppression.

We studied 637 transfusion recipients seronegative for cytomegalovirus (CMV) in the following categories: neonates; pregnant women; and patients experiencing trauma, burns, cardiovascular surgery (adult or pediatric), major surgery, or gastrointestinal hemorrhages. Cultures and serological tests were used to follow up subjects for evidence of CMV infection for a period of three months after their last transfusion. Six (0.9%) developed CMV infection. No significant differences in risk among patient categories were observed. Infected patients received a significantly larger mean number of units of cellular blood products (CBP; 50.0 +/- 38.9 vs. 6.2 +/- 8.5; P less than .001) and plasma (23.7 +/- 15.3 vs. 2.6 +/- 4.6, P less than .001) than did uninfected patients. This result represents a risk per unit of CBP transfused of 0.14%, or approximately 0.38% per unit of seropositive CBP transfused. We observed, however, that patients exposed to CBP from greater than 30 donors had a higher risk of acquiring CMV infection than would be predicted if infectious units were randomly distributed among all donors (P less than .01).

Adult↗
PubMed1988

Reduction of beta-adrenoceptor density and evaluation of positive inotropic responses in isolated, diseased human myocardium.

Cardiac beta-adrenoceptors and the positive inotropic effects of adenylate cyclase-dependent (dobutamine, histamine, forskolin) and adenylate cyclase-independent agents (isobutylmethylxanthine (IBMX), dibutyryl-cAMP (db-cAMP), digoxin, digitoxin and calcium were measured in papillary muscle strips from severely failing (NYHA IV), moderately failing (NYHA II-III) and non-failing (NYHA I) human hearts. The density of beta-adrenoceptors in three NYHA I patients were 40.0, 42.0 and 42.9 fmol mg-1 protein. The density of cardiac beta-adrenoceptors was significantly reduced in NYHA II-III to 18.0 +/- 1.1 fmol mg-1 protein (n = 16) and further reduced in NYHA IV to 9.5 +/- 1.6 fmol mg-1 protein (n = 7). The KD values did not differ between the groups. Correspondingly, the positive inotropic effect of dobutamine was significantly reduced in NYHA II-III and almost lost in NYHA IV. The positive inotropic effect of histamine was similar in non-failing and moderately failing myocardium but reduced in preparations from severely failing hearts (NYHA IV). The positive inotropic effect of IBMX was diminished in moderately and severely failing myocardium depending on the functional class of heart failure. In contrast, the effects of forskolin, db-cAMP, digoxin and digitoxin were not impaired in NYHA IV when compared with the maximal positive inotropic effect of calcium. It is concluded that in the failing human heart (a) the number of cardiac beta-adrenoceptors is reduced proportional to the severity of heart failure; (b) the receptor coupling of H2-receptors to adenylate cyclase may be impaired, but only in severe heart failure; (c) the basal cAMP formation may be diminished; and that (d) the catalytic subunit of the adenylate cyclase and the cAMP-dependent protein kinases may be promising targets for drugs to restore force of contraction in human heart failure.

1-Methyl-3-isobutylxanthine↗
PubMed1988

Spinal cord injury and concomitant traumatic brain injury. Results of a longitudinal investigation.

One-hundred fifty persons with traumatic onset spinal cord injury (SCI) were administered a comprehensive neuropsychologic test battery an average of 7 weeks after SCI, and 67 were retested using the same battery an average of 38 weeks after initial testing. It was hypothesized that if traumatic brain injury were a significant sequela of SCI, retesting would reveal evidence of cognitive recovery over time and would further enable a clearer separation of preinjury cognitive capacity from the effects of injury. Significant improvement in test performance occurred across time to the degree and in a pattern similar to that noted in persons who have sustained mild to moderate traumatic brain injury. Hypothesized relationships between level and extent of SCI, etiology of injury and presence/absence of loss of consciousness and neuropsychologic test scores were not observed. Implications for the rehabilitation process are discussed.

Brain Injuries↗
PubMed1988

Positive inotropic effects in isolated ventricular myocardium from non-failing and terminally failing human hearts.

The positive inotropic responses to isoprenaline, dobutamine, histamine, forskolin, isobutyl-methylxanthine (IBMX), dibutyryl-cyclic adenosine monophosphate (db-cAMP), ouabain and calcium were studied in isolated, electrically driven papillary muscle strips from either terminally failing human hearts or non-failing donor myocardium. The positive inotropic effect of calcium has been taken to evaluate the maximal force of contraction of each individual muscle strip ('contractile reserve'). In the non-failing heart, the maximal positive inotropic effect of isoprenaline, dobutamine, IBMX, ouabain and calcium were not significantly different, but were significantly greater than histamine. In terminally failing hearts, the positive inotropic effects of agents stimulating the adenylate cyclase by a receptor-dependent mechanism (isoprenaline, dobutamine and histamine) and the phosphodiesterase inhibitor IBMX are less than in the normal heart. Furthermore, these compounds gave a markedly reduced inotropic effect compared with forskolin, db-cAMP and ouabain, which gave maximal responses similar to calcium in the failing hearts. The data did not differ when the increase of force of contraction was related to the diameter of each preparation. These results indicate that a defect in adenylate cyclase occurs in the failing human heart, presumably located at the regulatory stimulatory subunit (Gs) of the adenylate cyclase since effects through stimulatory receptors were reduced. Responses from activation of the catalytic subunit or through cAMP-dependent protein kinases were less affected. Since the positive inotropic effect of IBMX is also impaired, it is suggested that the basal rate of cAMP production is also reduced in heart failure.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-3-isobutylxanthine↗
PubMed1988

N-acetylation and serotonergic measures in a group of psychiatric patients.

Serotonin is N-acetylated to melatonin. The purpose of this study was to explore the possibility of N-acetylation of dapsone reflecting serotonergic activity. The ratio of monoacetyldapsone/dapsone (MAD/DDS) in plasma, 5-HIAA in CSF, and imipramine-binding to platelets were investigated in a group of psychiatric patients, diagnosed according to the DSM-III as affective disorders, schizophrenia, and personality disorders. There was no significant correlation between either of the serotonergic estimates and N-acetylation in the whole patient group or in diagnostic subgroups of patients. Sixty-four percent of the patients were slow N-acetylators (MAD/DDS less than 0.4), which is a ratio in line with several other studies of psychiatric patients. Among patients with affective disorders, all unipolar patients were slow N-acetylators, while five out of six bipolar patients were fast N-acetylators. The N-acetylation of patients with a history of suicide attempt did not differ from those without. The discrepancy in N-acetylation between uni- and bipolar patients might again address the issue of them representing two different biochemical and genetic disorders.

Acetylation↗