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Biomedical subjects

M C Hall

Publications and source records attributed to M C Hall.

At least 73 records · Page 4Linked to original sources
PubMed1992

A pleiotropic, posttherapy, enoxacin-resistant mutant of Pseudomonas aeruginosa.

An enoxacin-resistant Pseudomonas aeruginosa mutant (G49) isolated during patient therapy was characterized in detail. The G49 mutant was cross resistant to several classes of antibiotics including quinolones, beta-lactams, chloramphenicol, and tetracycline, but not imipenem or aminoglycosides. Compared with its paired pretherapy isolate G48, this mutant had several alterations in outer membrane proteins including a complete loss of the major porin protein OprF and a substantially altered lipopolysaccharide profile. Revertants were selected at a frequency of approximately 1% after enrichment for OprF+ cells on low-salt proteose peptone no. 2 medium. Ninety-seven of these OprF+ revertants were as susceptible to carbenicillin and norfloxacin as the pretherapy isolate. One of these revertants was characterized in more detail and shown to be indistinguishable in all properties from the pretherapy isolate. It is proposed that the multiple-antibiotic-resistance (Mar) phenotype of this mutant resulted from a single pleiotropic mutation.

Anti-Bacterial Agents↗
PubMed1992

Service quality in the health care industry: how are hospitals evaluated by the general public?

This paper investigates the "expectations" aspect of service quality in the health care industry. Specifically, an examination is made of the importance of various hospital characteristics to consumers, the dimensionality of service quality, and the relative importance of these dimensions across demographic groups. The results suggest that the competency and the behavior of physicians are the most important characteristics in the minds of consumers. Moreover, it was found that hospitals are evaluated along: (1) interpersonal, (2) amenities, (3) capabilities, and (4) accessibility dimensions. These findings are consistent with previous research in this regard. Additionally, significant differences in the importance of these factors were found across respondent gender, age, income, and education.

Adolescent↗
PubMed1991

Phenotypic characterization of quinolone-resistant mutants of Enterobacteriaceae selected from wild type, gyrA type and multiply-resistant (marA) type strains.

The NCTC type strains of Escherichia coli, Enterobacter cloacae, Serratia marcescens and Klebsiella pneumoniae were exposed to 3, 5 and 10 x MIC of nalidixic acid, enoxacin, ciprofloxacin, PD 117596 and PD 127391. From each strain a mutant with a high MIC of quinolones alone (gyrA) and a mutant with intermediate resistance to quinolones, some beta-lactams, chloramphenicol and tetracycline (multiply resistant, m-r) were selected on agar containing antibiotics. The gyrA mutants required a higher concentration of quinolone to inhibit DNA synthesis by 50% but quinolone uptake kinetics and outer membrane profile were the same as the wild type. The m-r mutants had similar DNA synthesis IC50 as the wild type, decreased quinolone uptake kinetics and had decreased expression of an OMP of approximately 40 kD. The gyrA and m-r mutants were then exposed to 3, 5 and 10 x MIC of the same quinolones and new mutants (F2) selected. The F2 mutants from the gyrA mutants displayed a further increase in quinolone MIC; the F2 mutants from the m-r mutants had several phenotypes: high quinolone MICs with cross resistance to other agents, high quinolone resistance alone, or intermediate quinolone resistance alone. Most F2 mutants had MICs above the recommended breakpoint concentrations for quinolones. The F2 mutants often had altered biochemical profiles (API 20E), however, only in the case of E. cloacae did this affect speciation with the strains being identified as Rhanella aquatalis.

Anti-Infective Agents↗
PubMed1991

Metabolic consequences of urinary diversion through intestinal segments.

The use of intestinal segments in the reconstruction of the urinary tract for a variety of malignant and nonmalignant conditions is generally accepted. Metabolic derangements may result any time urine is in contact with the intestinal mucosa. Numerous studies concerning the pathophysiology of this syndrome have demonstrated that it is in large part secondary to reabsorption of urinary acid as ammonium and, to a lesser degree, to bicarbonate secretion into the urine. The syndrome of metabolic acidosis resulting from urinary diversion has been most common after ureterosigmoidostomy, often in the setting of renal insufficiency secondary to pyelonephritis and obstruction. It became a lesser clinical problem with the popularization and frequent use of conduit urinary diversions. At present, with a greater emphasis on the construction of large-capacity continent urinary diversions, there is an increased likelihood of metabolic derangements, especially in the setting of renal insufficiency. Furthermore, although the reported incidence of clinically problematic metabolic derangements is low with the newer modes of continent urinary diversion, it is impossible to assess the significance of a mild or asymptomatic acidosis, which may occur even in the setting of normal serum electrolytes. Only with close long-term follow-up can the significance of this change be determined.

Acidosis↗
PubMed1990

Mechanism of action of lomefloxacin.

The inhibition of supercoiling activity of reconstituted Escherichia coli DNA gyrase by lomefloxacin, ciprofloxacin, and norfloxacin was determined. The concentrations of quinolones needed to inhibit DNA synthesis in Escherichia coli, Enterobacter cloacae, Serratia marcescens, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus were also measured. The kinetics of uptake of [14C]lomefloxacin and unlabeled lomefloxacin into whole cells of E. coli KL-16 and S. aureus NCTC 8532 and the induction of RecA in E. coli GC2241 were assayed. All strains had wild-type susceptibilities to quinolones. The concentration of quinolones needed to inhibit DNA synthesis by 50% correlated with the MIC for members of the family Enterobacteriaceae and P. aeruginosa. The concentration of quinolones needed to inhibit DNA synthesis by 50% for late-logarithmic-phase S. aureus also correlated with the MIC, unlike the data from early-logarithmic-phase cultures. E. coli and S. aureus showed a similar pattern of uptake kinetics of [14C]lomefloxacin and unlabeled lomefloxacin, indicating that the difference in the susceptibilities of the two species is probably due to different target site affinities. Essentially, lomefloxacin was less active than ciprofloxacin and ofloxacin and had activity similar to those of norfloxacin and enoxacin.

Anti-Infective Agents↗
PubMed1989

Validity of bioelectric impedance for body composition assessment in children.

Whole-body bioelectrical impedance analysis (BIA) was evaluated for its reliability and accuracy in estimating body composition in children. The hypothesis that the index, body height2 divided by resistance (RI), can accurately predict fat-free body mass (FFB) and percent fat (%FAT) in children was tested on 94 caucasian children 10-14 yr old. Criterion variables were FFB and %FAT estimated using multicomponent equations developed for children. BIA measurements (resistance and reactance) were found to be reliable. Prediction accuracy (standard error of the estimate, SEE) for FFB from RI alone was 2.6 kg and for %FAT from RI and body weight was 4.2%. For RI, anthropometric variables and reactance, the SEE improved to 1.9 kg FFB. For RI and anthropometric variables, the SEE was 3.3% FAT. For anthropometric variables alone, the SEE's were 2.1 kg FFB and 3.2% FAT. Adult FFB and %FAT prediction equations cross-validated with this sample resulted in SEE's similar to those for adult samples. We conclude that RI together with anthropometry is a reliable and an acceptably accurate method of estimating FFB mass and %FAT in children.

Adipose Tissue↗
PubMed1977

Eustachian tube blockage and Meniere's disease.

On the basis of our clinical experience, it has been noted that an unusually large proportion of patients with Meniere's disease have intermittent eustachian tube blockage. A review of the tympanograms of 81 patients with Meniere's disease, representing 107 ears, showed that 25 (30.9%) of the patients and 35 (32.7%) of the ears had abnormal negative middle ear pressure. The maximum compliance peak was in at a pressure point in excess of --100 mm H2O. Further investigation of these patients has led us to conclude that intermittent eustachian tube blockage frequently accompanies Meniere's disease, yet it is not necessarily the cause of the symptomatic disorder.

Adult↗
PubMed1976

Cardiac monitoring during exercise tests in the horse. 2. Heart rate responses to exercise.

Data on resting heart rates, pre-exercise heart rates, the anticipatory rises before exercise, the influence of speed of work and recovery heart rates have been presented. Some observations on differences in the heart rate response on slow and fast working days are also recorded. In conformity with other workers, a linear relationship between heart rate and working speed within the range of 400-800 metre/min was observed. When the speed of work was between 400-800 metre/min, horses with resting ECG's classed as abnormal had significantly higher heart rates than those regarded as normal. It was also observed that the abnormal animals showed lower heart rates than a small number classed as borderline. The significance of these findings is discussed and the need for further work indicated.

Animals↗
PubMed1976

Cardiac monitoring during exercise tests in the horse. 3. Changes in the electrocardiogram during and after exercise.

Changes that occur in the equine ECG during and after exercise have been described and compared with resting ECG's obtained from the same horses. When the speed of work equals or is greater than "three-quarter pace" (i.e. "even time" or 200 metres in 15 seconds) the high heart rates developed cause the loss of ECG waveforms that are readily discernible at rest. Although differences in the waveforms between horses with normal and abnormal resting ECG's have been observed, the more definitive useful information is the fact that abnormal horses showed significantly higher heart rates than normal horses at a particular speed of work. When this occurs in combination with a resting ECG classified as borderline or abnormal and the exercise ECG shows positive, low amplitude, broad rounded T waves or transient bursts of sine-waves suggestive of ventricular flutter, racing performance is likely to be impaired. Although more work needs to be done and improvements in technology are necessary, the exercise ECG has potential for improving understanding of physical fitness and the significance of resting cardiac abnormalities.

Animals↗
PubMedDate not supplied

Transrectal ultrasound and biopsy in the early diagnosis of prostate cancer.

BACKGROUND: Historically, the prostate was evaluated for cancer by simple digital rectal examination, and biopsy to obtain a tissue diagnosis of cancer was performed blindly. The advent of ultrasound technology offered a new way to evaluate the prostate, and biopsy techniques were soon developed to incorporate ultrasound guidance. METHODS: The authors review the role of transrectal ultrasound (TRUS) of the prostate and ultrasound-guided biopsy of the prostate in the diagnosis of prostate cancer. These techniques are traced from their origins to the current standards of care, with attention paid to developments and controversies in recent literature. RESULTS: Early experience with TRUS led to the description of "classic" sonographic findings of prostate cancer. To obtain a tissue diagnosis of cancer, these regions were initially targeted in ultrasound-guided biopsies. Concomitant with the development of TRUS, though, was the development of the prostate-specific antigen (PSA) assay. Over the past decade, there has been a profound stage migration due to earlier detection of prostate cancer. Most patients now diagnosed with prostate cancer have no palpable abnormality or specific sonographic findings. In response, ultrasound-guided biopsies have become more systematic, rather than lesion-specific, in nature. CONCLUSIONS: TRUS continues to play an important role in the evaluation of the prostate when malignancy is suspected. Although the optimal method of prostate biopsy is controversial, ultrasound is critical in ensuring accurate sampling of the gland.

Adult↗