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Biomedical subjects

D F Brown

Publications and source records attributed to D F Brown.

At least 91 records · Page 5Linked to original sources
PubMed1990

A rapid technique for detection of resistance to chloramphenicol in Streptococcus pneumoniae and comparison with minimum inhibitory concentration and disk-diffusion methods.

Fifty-two strains of Streptococcus pneumoniae were examined for production of chloramphenicol acetyltransferase (CAT) by a rapid technique based upon induction of enzyme activity and chemical assay. This method was compared with one measuring the minimum inhibitory concentration (MIC) by agar dilution and a diffusion test with disks containing 10 micrograms, 30 micrograms and 50 micrograms of chloramphenicol. The MIC for 13 chloramphenicol-resistant strains was 16 mg/L and for 39 sensitive strains less than or equal to 4 mg/L. The chemical assay clearly distinguished resistant from sensitive strains; it was technically simple and provided results within 90 min. The distinction between sensitive and resistant bacteria in the disk diffusion assay was clearer with 10-micrograms than with 30-microgram and 50-micrograms disks. However, the chemical CAT assay, with enzyme induction, is recommended when a rapid result is required.

Bacteriological Techniques↗
PubMed1990

Effect of sample volume on yield of positive blood cultures from adult patients with haematological malignancy.

Six hundred and sixteen blood samples from patients with haematological malignancy were each distributed equally among three identical cells in a Malthus Microbiological Growth Analyser. The mean (SD) volumes inoculated into sets in which one, two, or three of the three bottles were positive were 37.7 (10.1) ml, 37.4 (12.9) ml, and 37.7 (10.5) ml, respectively. Overall, clinically important organisms were isolated from one bottle only with 18 cultures, from two bottles only with 19 cultures, and from all three bottles in a set with 104 cultures. If the yield from a single bottle inoculated with a mean volume of 12.6 ml blood is taken as 100%, the yield from 25.2 ml in two bottles was 110.7% and the yield from 37.7 ml in three bottles was 115.6%. The increased yield from increased volume was considerably lower than that reported from unselected groups of patients, which suggests that the magnitude of bacteriaemia is greater in patients with neutropenia. The isolation of infecting organisms from the blood of patients with neutropenia is, however, particularly important in directing chemotherapy and consequently 45 ml blood samples from these patients continue to be requested.

Adult↗
PubMed1989

Beta-thioglucose inhibits gold thioglucose lesions in the ventromedial hypothalamus.

Gold thioglucose (GTG) has been known to be an obesity causing agent for over 40 years. GTG works by affecting dendrites in the mouse ventromedial hypothalamus (VMH) producing a permanent VMH lesion and subsequent hyperphagia and obesity. We have investigated the effect of beta-thioglucose (BTG), a glucose antimetabolite, on GTG-induced lesions in the VMH of mice. Twenty-eight female CF-1 mice were used in this study. Seven micron sections were made of the mouse VMH, mounted on glass slides, and stained with hematoxylin and eosin. A previous report of BTG action on GTG-induced lesions has not supported a competitive inhibition between these two drugs. Our data demonstrate that at 1/2 hour, 6 hours, and 12 hours post BTG, BTG completely inhibited GTG-induced lesions in the VMH.

Animals↗
PubMed1989

Naloxone alteration of blood flow in a nonischemic region of the partially ischemic gerbil brain.

The effect of naloxone (NAL) treatment on cerebral blood flow in the partially ischemic gerbil brain was investigated. Under pentobarbital anesthesia, the right carotid artery in female gerbils was cannulated. A permanent ischemia was produced in the right anterior brain portion by carotid ligation. One hour after the surgical procedure, radioactive 51Cr, microspheres were injected via the carotid catheter before intraperitoneal administration of NAL (50 mg/kg) in saline solution. Five minutes later, radioactive 46Sc microspheres were injected via the carotid catheter. Controls were injected in the same manner with vehicle and microspheres. Brain quarters were assessed for 51Cr and 46Sc radioactivity with a gamma counter. A significant decrease in microsphere deposition was observed with NAL treatment in the right rear, nonischemic part of the brain. No changes in radioactivity were detected in the ischemic portion. These findings suggest that NAL may alter brain blood flow independently of ischemia.

Animals↗
PubMed1988

The reliability of methods for detecting chloramphenicol resistance in Haemophilus influenzae.

Eighty-eight strains of Haemophilus influenzae were examined for resistance to chloramphenicol by various techniques. Methods compared were a rapid chemical assay for chloramphenicol acetyltransferase (CAT), an agar dilution minimum inhibitory concentration (MIC) method, disc diffusion tests with 10, 30, and 50 micrograms discs, and a microbiological technique for detecting CAT. Fifty-eight chloramphenicol-sensitive strains had MICs less than or equal to 0.5 mg/l, while 30 resistant strains had MICs greater than or equal to 4 mg/l. The chemical CAT assay clearly distinguished resistant from sensitive strains, was simple to perform and provided results within 30 min. By disc diffusion, the lower the disc content the clearer the distinction between sensitive and resistant populations. Difficulties were encountered in interpretating the microbiological CAT assays as some sensitive strains appeared resistant. The chemical CAT assay is recommended for use when a rapid result is required. Rare chloramphenicol-resistant, CAT-negative strains have been described in the USA and these strains would only be detected by a disc diffusion or MIC test.

Chloramphenicol O-Acetyltransferase↗
PubMed1988

Prospective addition of beta-lactamase to blood culture medium.

The value of adding beta-lactamase to bottles of blood-culture medium before their distribution to wards was investigated. Significantly more bottles containing beta-lactamase were culture-positive than those without (p less than 0.002). In another series, when the enzyme was added to both bottles in each set there was no significant difference in isolation rates between the two bottles. The groups of organisms which were isolated more readily when beta-lactamase was present were staphylococci and streptococci. Storage of beta-lactamase (Genzyme broad-spectrum mixture) in blood-culture medium at room temperature resulted in rapid loss of cephalosporinase activity, whereas little decline in penicillinase activity was noted over a period of 118 days.

Anti-Bacterial Agents↗
PubMed1988

Changes in patients' stress and arousal levels associated with therapists' perception of their requests during crisis intervention.

This study examined changes in 32 patients' stress and arousal levels before and after an initial crisis intervention interview, according to the degree of mismatch between patient and therapist perceptions of requests made during the interview. A good match between patient and therapist perceptions was associated with a decrease in patients' stress following the interview. Although patients rated by therapists as more severely disturbed had the highest mismatch scores, it is unlikely that the observed mismatch between patients and therapists is accounted for solely by psychiatric condition. The findings suggest that measuring changes in stress may well provide a valuable means of evaluating patient response to the initial crisis interview.

Adult↗
PubMed1988

Antimicrobial susceptibility testing of Neisseria gonorrhoeae: a trial organised as part of the United Kingdom national external quality assessment scheme for microbiology.

Six strains of Neisseria gonorrhoeae were distributed to 411 United Kingdom laboratories who were asked to test the susceptibility of the strains to penicillin, cefuroxime, tetracycline and spectinomycin and to test for production of beta-lactamase. Details of methods used were requested by means of a questionnaire. The number of reports recording sensitive strains as resistant was 5% for penicillin, 0.7% for cefuroxime, 3% for tetracycline and 4% for spectinomycin. The number of reports recording resistant strains as sensitive was 7% for penicillin (0.2% with beta-lactamase producing strains, 20% with non-beta-lactamase producing strains), 96% for cefuroxime, 76% for tetracycline and 8% for spectinomycin. There was an association between greater error rates and the use of high content discs for testing tetracycline, the use of low content discs for testing spectinomycin, failure to dilute the inoculum, and use of acidimetric methods rather than methods that use a chromogenic cephalosporin for detecting beta-lactamase.

Anti-Bacterial Agents↗
PubMed1988

Automated screening of blood cultures with the Malthus microbiological growth analyser.

A total of 3347 blood cultures from patients in all hospital wards were examined on a Malthus microbiological growth analyser and by a conventional system. There was no significant difference in the total numbers of positive cultures of clinical importance between the two systems (p greater than 0.05). Staphylococcus aureus, however, was isolated more often by the conventional method (p less than 0.05). Failure of the automatic detection routine limited the potential of the Malthus system for earlier detection of positive cultures. Daily visual examination of Malthus curves and subculture of bottles not promptly attached to the apparatus were necessary to avoid missing some positive cultures. False positive rates were 13% for the Malthus system and 2% for the conventional system. The contamination rate was considerably lower in the Malthus system (p less than 0.001). Further development would be necessary for the apparatus to be acceptable for routine screening of blood cultures.

Bacteria↗
PubMed1987

Gold thioglucose-induced brain lesions in hamsters.

Previous studies suggest species differences in the central neural effects of gold thioglucose (GTG). To further assess these differences, we studied the effects of single intraperitoneal injections of GTG on the brains of golden hamsters (Mesocricetus auratus). Within 48 hr of treatment, each of the GTG doses tested (500, 1000 and 1500 mg/kg) had produced lesions in the ventromedial hypothalamus and area postrema. These findings are of interest since they identify the hamster as the first animal known to be susceptible to GTG-induced lesion formation, but resistant to the hyperphagia commonly associated with glucose analog glucoprivation.

Animals↗
PubMed1987

Age-related changes in social and psychological models predicting dental care in children.

Social and psychological factors associated with dental care were examined in two groups of children ages 6-8 and 9-11 years. Level of surface plaque, measures of dental health status (that is, total number of primary teeth decayed, missing, and filled [dmft] and total number of permanent teeth decayed, missing, and filled [DMFT] ), and frequency of dental visits were used as indicators of preventive behavior. The importance of social and psychological factors associated with these indicators was shown to vary with age group and with the specific preventive behavior indicator. Perceived level of dental anxiety and dental vulnerability were significantly associated with dental care, with dental anxiety being an important factor only in the lower group. Accessibility to a free school dental service was an important predictor of dental health status (DMFT) in the older age group, however, the data indicate that only when this service was offered within an organized structure of referral and transport was there an optimal effect on subsequent dental health.

Age Factors↗
PubMed1987

Social and psychological factors associated with adolescents' self-acceptance of occlusal condition.

Studies using plaster models of teeth and photographs simulating the full range of occlusal conditions have found high agreement between measures of adolescent social acceptability of these conditions and perceived need for orthodontic treatment. This study examined the association between adolescents' acceptability of their own occlusal condition, severity of malocclusion, and likelihood of undergoing orthodontic treatment. The factors predicting the acceptability of occlusal condition of 13-yr-olds, as assessed by the SASOC scale, were measurements of acceptability of general physical appearance, and the severity of occlusal condition. Variability in SASOC scores appeared to be independent of gender, socioeconomic status, and ethnicity. Gender, and severity of occlusal condition were important differences between subjects who had received, planned, or were undergoing orthodontic treatment, and those who had not. Neither SASOC scores nor perceived need for treatment accounted for a significant proportion of the variance between these groups. Although adolescents seeking orthodontic treatment had a greater severity of malocclusion than those not, little difference was observed between these groups in acceptance of occlusal condition.

Adolescent↗
PubMed1986

Kinetic properties of glycogen synthase from skeletal muscle after phosphorylation by glycogen synthase kinase 4.

Glycogen synthase I (EC 2.4.1.11) from rat and from rabbit skeletal muscle was phosphorylated in vitro by glycogen synthase kinase 4 (EC 2.7.1.37) to the extent of 0.8 phosphates/subunit. For both phosphorylated enzymes, the activity ratio (activity without glucose 6-P divided by activity with 8 mM glucose 6-P) was 0.8 when determined with low concentrations of glycogen synthase and/or short incubation times. However, the activity ratio was 0.5 with high enzyme concentrations and longer incubation times. It was found that the lower activity ratios result largely from UDP inhibition of activity measured in the absence of glucose 6-P. Inhibition by UDP was much less pronounced for glycogen synthase I, indicating that a major consequence of phosphorylation by glycogen synthase kinase 4 is an increased sensitivity to UDP inhibition.

Animals↗
PubMed1986

Psychological and behavioral factors associated with dental anxiety in children.

This study of the relationship between dental anxiety and psychological and behavioral variables suggests that the most important factor in explaining the variance in children's perceived dental anxiety is their level of general anxiety. The negative relationship found among the frequency of dental visits, deciduous diseased, missing, and filled teeth (dmft), and dental anxiety implies that dental anxiety does not develop through simple exposure to dental settings. Perceived locus of control and perceived health vulnerability did not appear to be associated in any significant way with dental anxiety. The results indicate that dental anxiety may reflect a more general class of anxiety behaviors, rather than fears learned in response to a specific situation.

Anxiety↗
PubMed1986

Inhibition of gold thioglucose lesion formation in the ventromedial hypothalamus by a glucocorticoid.

A single intraperitoneal injection of gold thioglucose (GTG) yields a lesion in the ventromedial hypothalamus (VMH), eventually producing obesity. The anti-inflammatory compounds, aspirin or glucocorticoid (GC), have been shown previously to block GTG lesion formation in the VMH when examined at the light microscopic level. Ultramicroscopic changes in the VMH have been observed to account for the inhibition of GTG-induced lesions with aspirin. We sought to determine whether or not GC action in the prevention of GTG lesion formation was also accompanied by VMH morphological changes at the ultrastructural level. Our results demonstrated that hydrocortisone pretreatment completely protected the VMH from any GTG-induced necrosis. We hypothesize that this inhibition of GTG lesion formation is not mediated by GC anti-inflammatory activity, but related to an anti-insulin activity of GC, GC-induced changes in VMH cell membrane receptor function, and/or alterations in serotonin metabolism.

Animals↗
PubMed1986

Glucose analog effects on glucose oxidation in the ventromedial hypothalamus.

The effect of the glucose analogs 2-deoxyglucose (2DG), glucosamine (GLA), mannoheptulose (MAN), and gold thioglucose (GTG) on glucose utilization in the mouse ventromedial hypothalamus (VMH) was assessed by using an in vitro incubation system. The amount of 14C-CO2 generated from uniformly labelled 14C-glucose was measured in VMH tissue cubes. MAN and GTG did not alter glucose oxidation at any of the concentrations compared with controls. GLA inhibited glucose utilization but only when the amount of GLA was 3 times that of glucose in the medium. However, this difference was not significant. The 2DG inhibited glucose oxidation significantly (50%; P less than 0.005), but only when 2DG was used in a quantity three-fold greater than glucose. These results imply that the VMH, a reputed central area for controlling feeding behavior, may possess a high affinity for glucose, which is not effectively altered by competitive inhibitors.

Animals↗
PubMed1986

An ultrastructural study of gold thioglucose lesion formation in the ventromedial hypothalamus: subnecrotic gold thioglucose dose.

In an ultrastructural study of gold thioglucose (GTG) lesion formation in the mouse ventromedial hypothalamus (VMH), a single intraperitoneal subnecrotic dose of GTG (100 mg/kg) was used to induce a VMH microlesion, visible only by electron microscopy. Definitive neuronal alterations were not evident until eight hours after GTG injection. Large pericapillary processes, probably dendrites, displayed a loss of cytoplasmic density and distention, while the capillary endothelium appeared normal. Some intercellular distention also was apparent. By 24 hours after GTG administration, degenerating neurons were visible. Swollen and disrupted synaptic profiles were seen. However, no vascular damage was evident. These results support the evidence that GTG is a neurotoxin for structures in the mouse VMH.

Animals↗