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Biomedical subjects

D F Brown

Publications and source records attributed to D F Brown.

At least 145 records · Page 8Linked to original sources
PubMed1977

Survey of effects of variety and growing location of cotton on cardroom dust composition.

Electrostatically precipitated respirable dusts from six major U.S. varieties and growing areas were analyzed. From 81-95% by weight, was under 15 micronm diameter. Composition was affected more by growing location than by variety. Dusts contained 16-28% ash, 8-9% moisture, and 62-76% organic matter, including 16-31% protein and 2-12% cellulose. Inorganic composition reflected soil type and minerals. Major elements were silicon, calcium, potassium, phosphorus, magnesium, and aluminum. Infrared spectra of dusts resembled proteins, but water extract spectra did not. Possible implications concerning byssinosis are discussed.

Air Pollutants↗
PubMed1977

Enteropathogenicity of Vibrio parahaemolyticus in the ligated rabbit ileum.

The enteropathogenicity of Vibrio parahaemolyticus was investigated by contrasting the effects of whole cells, cell fragments, cell-free preparations, and media constituents injected into rabbit ileal loops. Three of 20 cultures utilized were Kanagawa-negative strains from seawater and sea fish. The remaining 17 cultures included both Kanagawa-positive and -negative strains from Japanese victims of gastroenteritis. Broth culture filtrates concentrated 10-fold by dialysis against 30% Carbowax were unreactive, whereas lyophilized filtrates, regardless of Kanagawa type, as well as all sterile broth preparations containing greater than or equal to 5% NaCl gave positive reactions in the rabbit gut. In contrast, crude lysates derived from broth cultures of Kanagawa-positive strains caused loop dilatation; lysate supernatants were unreactive. Lysates of cells washed from brain heart infusion agar were more reactive than lysates from Trypticase soy agar-grown cells. When agar-grown cell lysates prepared by disruption in saline were dialyzed against distilled water, they were devoid of gut reactivity. Reactivity was restored in dialysands resuspended in saline and in dialysates concentrated 10-fold. The agar-grown cell lysates exhibited Kanagawa-type hemolysis. Our data support the conclusion that the rabbit loop reactivity observed with lyophilized, cell-free culture filtrates may result from excessively elevated NaCl concentrations, and that a toxic factor associated with large-cell particles may be dialyzable, depends on saline for expression, and resembles the Kanagawa hemolysin.

Animals↗
PubMed1977

Pericardial constriction as a late complication of coronary bypass surgery.

A 55-year-old man had progressive dyspnea, recurrent atrial arrhythmias, and severe right heart failure following coronary bypass surgery. His condition improved only slightly with the usual decongestive therapy. When transferred for further studies 5 months after the operation, he had typical clinical and hemodynamic findings of constrictive pericarditis. Review of chest films following the bypass operation revealed a large pericardial effusion or hematoma, the incomplete resolution of which probably caused the pericardial constriction confirmed at thoracotomy. The man was treated by pericardiectomy. A recent report on the incidence of overt tamponade soon after bypass surgery suggests that a significant volume of pericardial fluid accumulates in the early postoperative course in many instances and that late constriction may not be a rare complication. In treating patients who have circulatory congestion after such operations, it is important that the physician consider constrictive pericarditis and not assume that the clinical findings are the consquence of myocardial failure.

Coronary Artery Bypass↗
PubMed1976

Gentamicin resistance in Staphylococcus aureus.

A clinical isolate of Staphylococcus aureus was resistant to gentamicin, kanamycin, and tobramycin by virtue of the production of a drug-inactivating enzyme. Attempts to establish the cellular location of the genetic determinants for enzyme synthesis have given equivocal results.

Anti-Bacterial Agents↗
PubMed1976

Chemical properties of cotton dust.

Byssinosis, a respiratory disease, is caused by dust in cotton textile mills. The heterogeneous, complex dust varies in composition and activity in different "cotton-related" processing operations. Information concerning the constitution of "cotton dust" is reviewed. Relevance of a single dust standard for all cotton operations is discussed.

Air Microbiology↗
PubMed1976

Pacemaker-induced change in prosthetic valvular sounds.

Variable intensity and timing of valvular sounds were noted in two patients with permanent pacemakers and prosthetic valves. In the first patient, who had a mitral and a tricuspid prosthesis, valvular opening sounds became widely separated with a change from nodal to ventricular paced rhythm. In a second patient, who had a mitral prosthesis in sinus rhythm with first-degree atrioventricular block, a very quiet closing sound increased markedly in intensity with the onset of ventricular pacing. The mechanism for these changes is described using a technique which at brief intervals throughout the cardiac cycle permitted documentation of simultaneously recorded phonocardiogram, electrocardiogram, and pulse tracings with a visible image of the prosthesis. In the usual patient with a prosthetic valve auscultatory changes should arouse a suspicion of malfunction; however, in the relatively uncommon patient with a prosthesis and an artificial pacemaker, it should be recognized that auscultatory changes may well have a physiologic explanation.

Adult↗
PubMed1975

Impedance monitoring of bacterial activity.

Bacterial activity and growth were monitored by following the changes of electrical impedance of cultures in liquid media. The signal is expressed automatically as a curve similar to grwoth curves produced by other methods. The technique offers a new, rapid and sensitive means of detecting active micro-organisms and is potentially the basis of rapid automated systems in this field. The impedance changes indicate that the micro-organisms metabolise substrates of low conductivity into products of high conductivity and that the changes are due to the activity of the micro-organisms rather than increase in their numbers. The activity of strains of Escherichia coli, Klebsiella aerogenes, Pseudo-monas aeruginosa, Staphyloccus aureus, and Streptococcus faecalis was detected within 2 h with inocula of 10-3 minus 10-5 organisms per ml. Different reactions of bacteria in various media suggest that the method may be applied to the rapid identification of micro-organisms. The inhibitory effect of antibiotics on bacteria was demonstrated within 2 h, indicating that the method may be useful for the rapid determination of bacterial sensitivity to antibiotics and the rapid assay of antibiotics in serum. Correlation of response time to initial inoculum allows estimatin of numbers of viable organisms. The sensitivity of the method allowed detection of activity due to Myoplasma argininii within 3 h; this suggests that the method might be applicable to the rapid detection of other slowly growing organisms, such as mycobacteria.

Ampicillin↗
PubMed1975

Comparison of antibiotic discs from different sources.

Antibiotic discs from Oxoid, Mast, AB Biodisk, Difco, and Baltimore Biological Laboratories were compared, where discs of similar antibiotic content were available, in diffusion-sensitivity tests against organisms of known sensitivity. Discs from Oxoid and Mast gave zones 1-5 mm larger than discs from other manufacturers with penicillin 2 units, ampicillin 10 mug, cephalothin 30 mug, methicillin 10 mug, carbenicillin 100 mug, erythromycin 15 mug, chloramphenicol 50 mug, and trimethoprim 1-25 mug, while discs containing aminoglycoside antibiotics, lincomycin, fusidic acid, tetracycline, nalidixic acid, penicillin 10 units, and polymyxin B gave similar zone sizes whatever the source. Where tested, different batches of single discs from the same source did not vary significantly in antibiotic content as indicated by variation in zone size; but with some antibiotics Multodisks gave larger zones than single discs from the same source. The implications of these differences are discussed.

Anti-Bacterial Agents↗
PubMed1975

Comparison of tablets and paper discs for antibiotic sensitivity testing.

The value of tablets and paper discs as reservoirs of antimicrobial agents for use in sensitivity testing was compared. Antibiotics that were unstable in paper discs showed no demonstrable loss of activity in tablets over a period of 50 days under adverse storage conditions. The antibiotic content of commercially prepared tablets is very high in comparison with the accepted content of paper discs used in Britain, but not all of the agent is released from tablets during tests. Comparison of the size of zones of inhibition around tablets and standard paper discs indicated that the amount of the various agents released from the tablets varied between 2-6% and 69% of the stated content. In tests of the sensitivity of a range of common pathogenic organisms, the results obtained with the tablet method--when interpreted as recommended by the manufacturer--were generally similar to those obtained with a paper disc method commonly used in British laboratories. In 47% of tests with aminoglycoside antibiotics, however, strains sensitive by the disc method were 'intermediate' or resistant by the tablet method. As with paper discs, it was necessary to press the tablets on to the medium. With adjustment of the 'effective antibiotic content of tablets to bring it into line with the accepted content in paper discs, the stability of antibiotics in the tablets might make them an acceptable alternative to paper discs.

Anti-Bacterial Agents↗
PubMed1974

The reliability of methicillin sensitivity tests on four culture media.

The influence of culture medium, incubation temperature, and antibiotic content on the reliability of methicillin disc-sensitivity tests on strains of Staphylococcus aureus was evaluated. Tests were performed with an inoculum giving semiconfluent growth of colonies on four media, with 5-mug and 10-mug methicillin discs at incubation temperatures of 30, 35, and 37 degrees C. With Sensitest agar and Mueller-Hinton agar at 35 degrees C or below, methicillin resistance was reliably detected. On DST agar and Wellcotest agar discrimination between sensitive and resistant strains was possible only at 30 degrees C. On Wellcotest agar and DST agar it was not possible to detect methicillin resistance in one resistant strain at any temperature. For sensitive and resistant strains, the use of a 5-mug disc allowed greater differentiation than the 10-mug disc.

Culture Media↗