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Biomedical subjects

D L Brown

Publications and source records attributed to D L Brown.

At least 325 records · Page 18Linked to original sources
PubMed1983

The effect of complement-depletion or mannosyl receptor blockade on the in vivo clearance of antigen during a primary immune response in rabbits.

The effect of complement-depletion mediated by cobra venom factor or mannosyl receptor blockade induced by ovalbumin injections on the blood clearance of in vivo-generated soluble immune complexes were analysed in 2 variants of a primary immune elimination model system in rabbits. In the first variant, animals were immunized with particulate antigen to elicit high titre IgM antibodies, and received radiolabelled antigen on the first day of immunization. In the second variant, radiolabelled antigen was introduced on Day 8 of the immunization schedule. The results showed that (a) immune clearance of antigen (Days 6-8) was not inhibited by prior decomplementation of the animals with cobra venom factor, and (b) injection of ovalbumin just prior to immune clearance did not significantly alter the clearance kinetics of the resulting immune complexes. Thus, the results indicate that clearance of soluble immune complexes generated during a primary immune response is not mediated via C3b-C3b receptor interaction or via mannosyl-mannosyl receptor interaction in the reticuloendothelial system, but proceeds through other mechanisms perhaps involving Fc receptors.

Animals↗
PubMed1983

Antibody moieties within circulating immune complexes in heart transplant recipients.

Circulating immune complexes were isolated from the sera of cardiac allograft recipients by bovine conglutinin/anti-conglutinin co-precipitation, or by gel filtration and protein A-Sepharose affinity chromatography. The antibody moieties within these isolated immune complexes were tested for specificity against heterologous anti-thymocyte globulins by solid phase radioimmunoassay, and bacterial and viral antigens by indirect immunofluorescence. The results showed that in addition to possessing specific anti-equine anti-thymocyte globulin antibodies, immune complexes also contained cross-reacting antibodies to rabbit anti-thymocyte globulin and vice versa, despite the patients only having received antibody of one species. Similarly, antibodies directed against bacteria or viruses (cytomegalovirus, Herpes simplex, virus, Epstein-Barr virus) were found within immune complexes obtained during overt infection, but also where infection was not detected. These results demonstrate the heterogeneous nature of immune complexes in heart transplant sera, and suggest that various stimuli, including ATG therapy, infection and possibly polyclonal B cell activation, may be involved in their generation in cardiac transplantation.

Antibodies↗
PubMed1983

Organization of microtubules in dividing and elongating cells of Vicia hajastana Grossh. in suspension culture.

Cells of Vicia hajastana Grossh. cultured with 2,4-D showed coupled division and growth and formed multicellular files of small isodiametric cells. In GA without added 2,4-D, the cells stopped dividing and continued elongating for several days. Total growth was the same in both hormone conditions. An immunofluorescent technique was developed to study microtubule (MT) distribution. Cells in GA showed parallel MT arrays oriented transversely to the axis of elongation. In some cells the number of MT per unit length was maintained during growth while other elongating cells showed reduced frequency of MT. Microtubules often appeared as thickened, branched strands, probably as a result of lateral aggregation. In cells grown in 2,4-D some pre-prophase bands of MT were observed. Cells in mitosis lacked cortical MT, and all organized staining was in spindles or phragmoplasts. Interphase cells in 2,4-D showed variable organization of cortical MT ranging from disordered to transversely ordered. Cells in early interphase had disordered MT while larger cells showed order. These observations indicate that MT in cycling cells are continually changing organization, probably accounting for the different distributions observed in interphase cells. On cessation of the mitotic cycle, reorganization of MT stops and transverse arrays of cortical MT are maintained as cells elongate. These processes are similar to those observed in organized tissues; however, cultured cells offer distinct advantages for experimental manipulation and microscopic observation of cytoskeleton.

Cell Division↗
PubMed1983

Rapid and sustained oral theophylline loading. An alternative to intravenous aminophylline therapy.

We evaluated an oral theophylline loading-dose procedure that was designed to rapidly achieve and sustain theophylline serum concentrations of approximately 10 to 12 micrograms/mL. Ten healthy adults were given an oral loading dose of approximately 6 mg/kg of aminophylline, (Aminophyllin) (ie, 4.8 mg/kg of theophylline). Two hours later, each subject was given approximately 6 mg/kg of a sustained-release theophylline tablet (Theo-Dur). Serum samples were collected at 1/2, 1, 2, 3, 6, 9, and 12 hours, then assayed for theophylline concentration. The mean theophylline concentration (+/- SD) one hour after the initial loading dose was 10.5 +/- 2.3 micrograms/mL. Subsequent theophylline concentrations demonstrated minimal fluctuation, with means ranging from 10.7 +/- 1.6 to 13.6 +/- 2.8 micrograms/mL. Four of the subjects reported headache; none vomited or experienced severe nausea. We conclude that this method of oral theophylline loading can be effective in achieving prompt and sustained therapeutic theophylline levels without significant side effects and that this may provide a valuable therapeutic alternative in those asthmatic patients who do not clearly require intravenous aminophylline therapy.

Administration, Oral↗
PubMed1982

High-performance liquid chromatographic assay of cytosolic glutathione S-transferase activity with styrene oxide.

A high-performance liquid chromatographic (HPLC) assay for measuring cytosolic glutathione S-transferase activity with styrene oxide is described. After incubating lung or liver cytosol with reduced glutathione and styrene oxide, unreacted styrene oxide is extracted into ethyl acetate. An aliquot of the aqueous phase is evaporated to dryness and reconstituted in the mobile phase for HPLC analysis. The two glutathione conjugates of styrene oxide [S-(1-phenyl-2-hydroxyethyl)glutathione and S-(2-phenyl-2-hydroxyethyl)glutathione] are separated in less than 10 min; quantitation of transferase activity is based on the comparison of the UV absorbance of the two conjugates at 254 nm with synthetic conjugate standards. As little as 1 nmole of either conjugate can be quantitated with good precision. This assay has advantages over previously published methods for measuring styrene oxide glutathione S-transferase activity as it does not depend on the use of relatively unstable and expensive radiolabelled substrates.

Animals↗
PubMed1982

Evidence for cytochrome P-450 mediated metabolism in the bronchiolar damage by naphthalene.

Intraperitoneal administration of the volatile hydrocarbon, naphthalene, resulted in severe bronchiolar epithelial cell necrosis in mice, while hepatic or renal necrosis was not observed. Pulmonary damage and mortality by naphthalene were increased by prior treatment with diethyl maleate and decreased by prior treatment with piperonyl butoxide (1600 mg/kg). SKF 525A pretreatment had no effect on naphthalene-induced pulmonary damage. Administration of [14C]naphthalene resulted in the covalent binding of radiolabel to tissue macromolecules. Highest levels of binding occurred in lung, liver and kidney. Levels of covalent binding reached a maximum 2--4 h after treatment and corresponded to rapid glutathione depletion in lung and liver. Covalent binding was dose-dependent and showed a threshold between 200 and 400 mg/kg which coincided with almost total depletion of tissue glutathione levels. Covalent binding of reactive metabolites was increased 3--4-fold by prior treatment with diethyl maleate, and was decreased 3--4-fold by pretreatment with piperonyl butoxide. These studies support the view that naphthalene-induced pulmonary damage is mediated by the cytochrome P-450-dependent metabolism of naphthalene and that glutathione plays an important role in the detoxification of the lung damaging metabolite(s).

Animals↗
PubMed1982

The minimum effective dose of glucagon in upper gastrointestinal radiography.

The effect of small intravenous doses (0.025 and 0.05 mg) of glucagon was evaluated in 22 patients. All 12 patients given 0.05 mg demonstrated by hypotonicity of the stomach and duodenum at 1 min and beginning return of peristalsis at 2 1/2 min. Subsequently, 100 patients with radiographically normal upper gastrointestinal examinations who received 0.05 mg of glucagon intravenously were compared to 100 patients with normal examinations without it. Comparison was made to determine the effect of glucagon on gastric mucosal coating and distention of the stomach and duodenum. In all areas of the stomach, mucosal coating was significantly improved in the glucagon group. There was also increased distention of the distal antrum, duodenal bulb, and duodenal loop. No adverse effects were reported. Because of the short duration of action of glucagon, the examination needs to be coordinated and done rapidly. The routine use of a small dose of glucagon increased the performance time slightly with small additional cost but was compensated for by the increased diagnostic quality of the examination.

Adult↗
PubMed1982

Immunological studies in patients with rheumatoid arthritis receiving azathioprine and myocrisin in combination.

Thirty-one patients with classical or definite rheumatoid arthritis (RA), on treatment with azathioprine and sodium aurothiomalate in combination were studied. Absolute lymphocyte counts and IgA levels were reduced but this did not reach statistical significance. Lymphocyte transformation with phytohaemagglutinin (PHA) showed no significant difference from a control group. However, antibody dependent cell-mediated cytotoxicity was significantly impaired compared to rheumatoid controls (p less than 0.001). There was no relation to the degree of impairment of ADCC and the current dose of azathioprine nor to the total dose or duration of therapy. Inhibiting material to cell-mediated cytotoxicity was present in the sera of 23 patients but its presence showed no relation to the degree of cytotoxicity exhibited by cells in the same patient. Our studies of cellular cytotoxicity have revealed alterations in cellular function possibly attributable to azathioprine.

Adolescent↗
PubMed1982

We bit the bullet.

Explore the source record for details and available documents.

Nursing Service, Hospital↗
PubMed1982

Utilization of pneumococcal vaccine in a family practice residency.

Pneumococcal diseases continue to account for a significant amount of morbidity and mortality in family practice. Daily charts audits revealed significant underutilization of pneumococcal vaccine in a family practice residency. Identified primary factors for pneumococcal vaccine underutilization were inadequate physician knowledge regarding the vaccine and failure to consider vaccine need during physician-patient encounters. A physician education update regarding vaccine indications and use was completed. A questionnaire was developed and given to each patient, allowing the physician to quickly evaluate each patient's need for pneumococcal vaccine. Evaluation of the first 1,000 questionnaires revealed the approximately 20 percent of the patients had indications for pneumococcal vaccine. Evaluation of immunization records revealed significant increased utilization of the pneumococcal vaccine following initiation of the questionnaire. Patient questionnaires such as this can prove to be a useful tool in the evaluation and provision of preventive medicine services in the family practice setting.

Bacterial Vaccines↗
PubMed1981

Does the Mauthner cell conform to the criteria of the command neuron concept?

The relationship between the Mauthner (M) cell action potential of the bullfrog tadpole and the rapid tail-flip was studied with electrophysiological and video-recording techniques. Single action potentials were elicited in the M-cell by vibratory stimulation or electrical stimulation of the eighth cranial nerve. These impulses were followed by a tail-flip to the side contralateral to the M-soma. Similarly, a tail-flip was produced by direct intracellular stimulation of the M-cell. Hyperpolarization of the M-soma blocked orthodromic action potentials and prevented the tail-flip. Therefore, the M-cell action potential appears to be sufficient and necessary to produce a rapid tail-flip which is associated with a naturally observed startle behavior.

Action Potentials↗
PubMed1981

Suppression of amphetamine-induced EEG arousal in the hippocampus of haloperidol-treated rabbits.

Changes of hippocampal EEG activity resulting from administration of d-amphetamine were investigated in rabbits before, during and after chronic treatment with haloperidol. Cross-zero analysis of EEG data showed that chronic treatment with haloperidol (3 mg/kg/day, i.p. for 9 days) attenuated the amphetamine-induced increase in hippocampal theta rhythm. The increase of theta activity by amphetamine was fully restored 30 days after withdrawal of haloperidol. Further, haloperidol reduced the incidence of spontaneous theta rhythm in 3 out of 4 animals. It is suggested that the enhancement of hippocampal theta by d-amphetamine is mediated in part by dopaminergic mechanisms which are susceptible to the action of haloperidol.

Animals↗