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Biomedical subjects

S Brown

Publications and source records attributed to S Brown.

At least 487 records · Page 27Linked to original sources
PubMed1991

A modified broth dilution assay for antibiotic sensitivity testing of Mycobacterium avium-intracellulare using paraffin slide cultures.

Mycobacterium avium-intracellulare (MAI) can utilize paraffin wax as the sole carbon source in basal media. Paraffin slide culture (Para SL/C) has been employed for isolation and speciation of MAI derived from clinical sources. We have evaluated an adaptation of this method for antimicrobial sensitivity testing. Sixteen clinical isolates of MAI were tested against ciprofloxacin amikacin, and azithromycin by Para SL/C and compared with sensitivities obtained with a conventional broth microtiter procedure. The system can be performed rapidly over a median time interval of 6-8 days. The MIC was defined as the lowest concentration of antimicrobial agent necessary to inhibit growth on paraffin wax coated slides. With Para SL/C, the MIC values were determined at the time when the corresponding control tubes showed confluent growth. The procedure was reproducible with all of the agents tested. The MIC50 and MIC90 values obtained from the Para SL/C assay and from serial broth microtiter dilutions correlated well for ciprofloxacin and amikacin. However, results of the MIC50 and MIC90 for azithromycin did not correlate.

Amikacin↗
PubMed1991

Bacterial contamination of human milk: container type and method of expression.

Common questions from nursing women include: is the bacterial contamination of expressed milk different if collected manually versus mechanically and is there a large increase in bacterial contamination if the milk is collected into clean versus sterile containers. Similarly, there are mixed reports, and secondarily confusion, among lactating women regarding the benefit of discarding the initial portion of a milk expression to limit bacterial contamination with skin flora. To answer these concerns, we have measured the number of colony-forming units (CFU)/milliliter in expressed milk from 16 women. The experimental design, used in a randomized fashion with each woman, employed both sterile and clean containers for collection and both the manual and mechanical techniques for milk expression. The number of milk specimens containing greater than 10(4) CFU/ml was not different between those collected in clean versus sterile containers or between those collected with a manual versus a mechanical technique. Finally, the initial milk expressed did not have a significantly greater amount of bacterial contamination than the milk collected later in the milk expression.

Adult↗
PubMed1991

The effects of early postoperative radiation on vascularized bone grafts.

The effects of early postoperative radiation were assessed in free nonvascularized and free vascularized rib grafts in the canine model. The mandibles of one-half of the dogs were exposed to a cobalt 60 radiation dose of 4080 cGy over a 4-week period, starting 2 weeks postoperatively. The patency of vascularized grafts was confirmed with bone scintigraphy. Histological studies, including ultraviolet microscopy with trifluorochrome labeling, and histomorphometric analyses were performed. Osteocytes persist within the cortex of the vascularized nonradiated grafts to a much greater extent than in nonvascularized, nonradiated grafts. Cortical osteocytes do not persist in either vascularized or nonvascularized grafts subjected to radiation. New bone formation is significantly retarded in radiated grafts compared with nonradiated grafts. Periosteum and endosteum remained viable in the radiated vascularized grafts, producing both bone union and increased bone turnover, neither of which were evident to any significant extent in nonvascularized grafts. Bone union was achieved in vascularized and non-vascularized nonradiated bone. In the radiated group of dogs, union was only seen in the vascularized bone grafts.

Animals↗
PubMed1991

Activation of human platelets by exposure to a monoclonal antibody, PM6/248, to glycoprotein IIb-IIIa.

Monoclonal antibody PM6/248, which recognizes the GPIIb-IIIa complex on human platelets, causes platelet aggregation in platelet-rich plasma or in gel-filtered platelet suspensions. Aggregation follows a concentration-dependent lag phase and reaches a maximum at 8 micrograms/ml. High concentrations of antibody (less than 30 micrograms/ml) produce complete inhibition of the aggregation response. Aggregation is accompanied by serotonin secretion and thromboxane A2 synthesis, neither of which are inhibited by high concentrations of antibody, and by the mobilization of intracellular Ca2+. The F(ab')2 fragment of PM6/248 does not cause platelet activation and pre-incubation of platelets with this fragment inhibits all platelet responses stimulated by the whole antibody. Pre-incubation with the F(ab')2 fragment of the anti-Fc gamma RII Mab, IV. 3, also inhibits all responses to PM6/248. These data indicate that platelet activation stimulated by PM6/248 is caused by cross-linking of GPIIb-IIIa to the Fc gamma RII which stimulates signal transduction across the plasma membrane through a conformational change in the Fc gamma RII.

Animals↗
PubMed1991

Cognitive performance of alcoholics: a longitudinal evaluation of the role of drinking history, depression, liver function, nutrition, and family history.

To assess the role of drinking history, depression, liver function, nutrition, and family history on cognitive performance, 171 detoxified male alcoholics were administered a brief neuropsychological examination at admission and discharge from an inpatient treatment program and at a 3-month follow-up evaluation. Regression analyses showed that at admission, depression and liver function were significant predictors of neuropsychological performance, whereas at discharge 3 to 4 weeks later only age and an estimate of premorbid intelligence were significant predictors. At the 3-month follow-up, estimates of drinking following discharge and severity of depressive symptoms were major significant predictors of neuropsychological performance. Indices of drinking prior to admission to the treatment program, nutrition, and family history for alcoholism did not predict performance on any of the three test occasions. These findings indicate that in addition to the chronic neurotoxic effect of alcohol a number of different medical and psychiatric factors, as well as the acute effects of alcohol, contribute to the cognitive scores of patients at various points in the clinical course.

Adult↗
PubMed1991

Emergence of quinolone resistance among clinical isolates of methicillin-resistant Staphylococcus aureus in Ontario, Canada.

One hundred two isolates of methicillin-resistant Staphylococcus aureus (MRSA) randomly selected from across the Canadian province of Ontario were tested for their susceptibility to ciprofloxacin, norfloxacin, and nalidixic acid by the agar dilution method. Forty-nine percent (50 of 102) had high levels of resistance to these quinolone compounds. For the 50 resistant isolates, ciprofloxacin and norfloxacin had high MICs for 90% of isolates (MIC90s) of 128 micrograms/ml and greater than 128 microgram/ml, respectively; for these isolates, the nalidixic acid MIC90 was greater than 640 micrograms/ml. The majority (98%) of the 50 isolates were also resistant to tobramycin (MIC90, greater than 128 micrograms/ml), while 42% of the isolates were resistant to gentamicin (MIC90, 64 micrograms/ml). Quinolone-resistant MRSA isolates were susceptible to bacteriophages from several groups, indicating independent selection of resistant strains. These results suggest that a reappraisal of the use of fluoroquinolones against MRSA in Canada is necessary.

4-Quinolones↗
PubMed1991

Velocity changes, long runs, and reversals in the Chromatium minus swimming response.

The velocity, run time, path curvature, and reorientation angle of Chromatium minus were measured as a function of light intensity, temperature, viscosity, osmotic pressure, and hydrogen sulfide concentration. C. minus changed both velocity and run time. Velocity decreased with increasing light intensity in sulfide-depleted cultures and increased in sulfide-replete cultures. The addition of sulfide to cultures grown at low light intensity (10 microeinsteins m-2 s-1) caused mean run times to increase from 10.5 to 20.6 s. The addition of sulfide to cultures grown at high light intensity (100 microeinsteins m-2 s-1) caused mean run times to decrease from 15.3 to 7.7 s. These changes were maintained for up to an hour and indicate that at least some members of the family Chromatiaceae simultaneously modulate velocity and turning frequency for extended periods as part of normal taxis.

Cell Movement↗
PubMed1991

Genes for 7S RNAs can replace the gene for 4.5S RNA in growth of Escherichia coli.

4.5S RNAs of eubacteria and 7S RNAs of archaebacteria and eukaryotes exist in a hairpin conformation. The apex of this hairpin displays structural and sequence similarities among both 4.5S and 7S RNAs. Furthermore, a hyphenated sequence of 16 nucleotides is conserved in all eubacterial 4.5S RNAs examined. In this article I report that 7S RNAs that contain this 16-nucleotide sequence are able to replace 4.5S RNAs and permit growth of Escherichia coli.

Base Sequence↗
PubMed1991

Metabolic clearance rate of testosterone in male epileptic patients on anti-convulsant therapy.

There are several reports which state that male epileptics on anti-convulsant therapy have reduced sexual activity. We and others have shown that, although total testosterone is raised, the free testosterone concentration is reduced in this patient population. This could be a result of an increased metabolic clearance rate (MCR) of testosterone, inadequate secretion of LH to stimulate testosterone synthesis or inappropriately low testosterone production by the Leydig cells. We have examined these possibilities by measuring the MCR of testosterone in 15 male epileptics on anti-convulsant therapy. In this group of patients, the mean LH (9.3 +/- 5.9 IU/l) and sex-hormone binding globulin (SHBG) (54.5 +/- 22.9 nmol/l) concentrations were significantly greater than those of five normal control subjects (4.7 +/- 1.11 IU/l and 26.0 +/- 7.0 nmol/l respectively). Mean total testosterone concentrations of the two groups were not significantly different but the mean percentage of free testosterone and free testosterone concentration were significantly lower in the patient population (2.06 +/- 0.43 vs 2.98 +/- 0.27 and 0.56 +/- 1.1 vs 0.79 +/- 0.07 pmol/l). The MCR of testosterone was significantly lower in the patients (773 +/- 322 vs 1354 +/- 443 l/day) and showed a positive correlation with the percentage of free testosterone. Therefore, our results suggest that the lowered free testosterone in male epileptics on anti-convulsant therapy is not due to an increased MCR of testosterone. The increased LH concentration suggests primary hypogonadism. This, in turn, could be responsible for low free testosterone levels in the presence of normal testosterone.

Adult↗
PubMed1991

4.5S RNA: does form predict function?

4.5S RNA is a stable RNA of Escherichia coli, and functional homologs of the molecule apparently exist in all prokaryotes: eubacteria, archebacteria, and mycoplasma. Genetic and physiological measurements of the function of 4.5S RNA in E. coli indicate a role for this RNA in protein synthesis. A conserved domain of 4.5S RNA displays structural similarity with the eukaryotic 7S RNA that functions in protein secretion. Although complementation by eukaryotic 7S RNAs remains to be demonstrated, a number of archaebacterial 7S RNAs are able to replace 4.5S RNA for growth of E. coli, and 4.5S RNA is able to mediate a number of 7S RNA functions in vitro. Surprisingly, no effects on protein secretion in E. coli have been directly attributed to 4.5S RNA. These observations raise the question of whether molecules of similar structure necessarily perform the same function.

Base Sequence↗
PubMed1991

Adult children of alcoholics. The history of a social movement and its impact on clinical theory and practice.

This chapter proposes that the popular social movement of adult children of alcoholics (ACOA) has had a profound impact on theory development and clinical practice in the fields of mental health and chemical dependence. The birth of the social movement is first traced, looking back to the origins of Alcoholics Anonymous in the self-help movement and the corresponding professional development of a systems perspective that included the notions of alcoholism as a "family disease" and the "alcoholic family," which included young children. Extending the idea to adults followed. This chapter examines why this movement could not originate in either professional field, accenting narrow theoretical base, oversimplification, professional denial, and bias in beliefs and values. Implications of the label ACOA are next addressed. Finally, a new integrated theory is proposed which bridges mental health, chemical dependence, and self-help disciplines. This theory includes environmental, systems, and individual development perspectives and integration of behavioral, cognitive, and dynamic psychotherapies. The chapter concludes with new challenges for diagnosis and reimbursement.

Adult↗
PubMed1990

Selection for mutations in the PR promoter of bacteriophage lambda.

Insertion of DNA containing PR, the early rightward promoter of bacteriophage lambda, is lethal to M13-derived vectors when the promoter directs transcription (using the '+' strand as template) toward the M13 origin of replication (ori). Lethality can be relieved by mutation of PR, repression of the promoter by the lambda cl repressor, or by insertion of a strong transcription terminator between PR and ori. We have used selection for plaque formation in the absence of repressor to isolate 14 different mutations at 8 sites in PR. This method of isolating promoter mutants in vivo is applicable generally to strong promoters whose activity is regulated either positively or negatively.

Bacteriophage lambda↗