Search PubMed⌕ Search

Biomedical subjects

D Brown

Publications and source records attributed to D Brown.

At least 955 records · Page 53Linked to original sources
PubMed1984

Differences in visual sensitivity among mindfulness meditators and non-meditators.

Tachistoscopic presentation of light flashes was used to test for differences in visual sensitivity among 3 groups of practitioners of Buddhist mindfulness meditation and non-meditator-controls. Meditation practitioners were able to detect light flashes of shorter duration than the non-meditators. There were no differences among the meditator groups. There were no differences among the groups in ability to discriminate between closely spaced successive light flashes. The lower detection threshold for single light flashes for the meditators may reflect an enduring increase in sensitivity, perhaps the long-term effects of the practice of mindfulness meditation on certain perceptual habit patterns. The lack of significant differences in the discrimination of successive light flashes probably reflects the resistance of other perceptual habit patterns to modification. The results support the statements found in Buddhist texts on meditation concerning the changes in perception encountered during the practice of mindfulness.

Buddhism↗
PubMed1984

Visual sensitivity and mindfulness meditation.

Practitioners of the mindfulness form of Buddhist meditation were tested for visual sensitivity before and immediately after a 3-mo. retreat during which they practiced mindfulness meditation for 16 hr. each day. A control group composed of the staff at the retreat center was similarly tested. Visual sensitivity was defined in two ways: by a detection threshold based on the duration of simple light flashes and a discrimination threshold based on the interval between successive simple light flashes. All light flashes were presented tachistoscopically and were of fixed luminance. After the retreat, practitioners could detect shorter single-light flashes and required a shorter interval to differentiate between successive flashes correctly. The control group did not change on either measure. Phenomenological reports indicate that mindfulness practice enables practitioners to become aware of some of the usually preattentive processes involved in visual detection. The results support the statements found in Buddhist texts on meditation concerning the changes in perception encountered during the practice of mindfulness.

Buddhism↗
PubMed1984

An improved macrophage spreading assay--a simple and effective measure of activation.

The development of a quantitative spreading assay of macrophage activation is described. The assay involved incubation of macrophages on glass coverslips for 1 hour and assessment of cell size using a microscope attached to a microcomputer-assisted digitising system which allowed the diameter of 200 cells to be assessed within 10 minutes. Mouse peritoneal macrophages were used in the development of the assay. Internal consistency of the assay was shown by minimal inter-observer, intra-observer and inter-animal variation. Validation of the assay as a measure of macrophage activation was confirmed by the use of in vivo and in vitro activating agents. Once validated the assay was used to detect activation in alveolar macrophages from rats exposed to airborne asbestos. The macrophage spreading assay described here is quick, reliable, consistent and easy to perform and has a potentially wide application in studies of macrophage function and dysfunction.

Animals↗
PubMed1984

Gardnerella vaginalis vaginitis. The current opinion.

Gardnerella vaginalis, a gram-negative bacillus, was first described in 1954. The associated clinical entity, vaginitis, first described in 1955, is controversial. The disease has specific symptoms, signs and diagnostic criteria. It has a symbiotic relationship with anaerobic bacteria. Whether G. vaginalis is a pathogen or normal inhabitant of the vagina is a subject of debate. The term nonspecific vaginitis should not be used for G. vaginalis vaginitis. G. vaginalis is sexually transmitted.

Bacteriological Techniques↗
PubMed1984

Comely Wenuhotep: computed tomography of an Egyptian mummy.

Computed tomography circumvents many of the problems encountered in the traditional radiographic investigation of mummies. This case report demonstrates that CT provides an improved evaluation of mummification techniques and bony pathology as well as a better capability of characterizing preserved soft tissue.

Egypt, Ancient↗
PubMed1984

Three-day treatment with butoconazole nitrate for vulvovaginal candidiasis.

A multicenter clinical trial of 274 patients compared the efficacy and safety of a new vaginal antifungal compound, butoconazole nitrate cream 2% (butoconazole), to clotrimazole vaginal tablets 200 mg/day (clotrimazole). Both drugs were administered for three days. The patients were randomly assigned to one or the other treatment regimen. Eight days after treatment completion, Candida albicans was absent in vaginal cultures of 95% of patients receiving butoconazole and of 91% of patients receiving clotrimazole; 30 days after treatment completion, 80% of patients receiving butoconazole were free of the fungal infection; the corresponding number for clotrimazole was 74%. Complete absence of the entrance signs and symptoms of vulvovaginal candidiasis was noted in 82% of patients receiving butoconazole and 72% of patients receiving clotrimazole. The phamacokinetic parameters were studied in three women volunteers who received one dose of radiolabeled butoconazole nitrate vaginal cream 2%. Measurable levels of radioactivity were not detected until two to eight hours after vaginal administration of the compound. Maximum plasma levels of radioactivity were achieved 24 hours after dosing and ranged from 19 to 44 ng/mL and fell to background levels after 96 to 120 hours. Total radioactivity was excreted to an equal extent in urine (2.7%) and in feces (2.8%).

Adult↗
PubMed1984

Appearance of Helix pomatia lectin-binding sites on podocyte plasma membrane during glomerular differentiation. A quantitative analysis using the lectin-gold technique.

The visceral glomerular epithelial cells (podocytes) of newborn rat kidneys were examined by the lectin-gold technique to determine the distribution of Helix pomatia lectin-binding sites during glomerular development. Previous work has shown that this lectin, which primarily recognizes terminal N-acetyl-D-galactosamine residues of glycoconjugates (but also N-acetyl-D-glucosamine to a lesser extent), specifically labels the plasma membrane glycocalyx of podocyte foot process bases, whereas the plasma membrane of the podocyte cell body that is in contact with the urinary space is unlabeled. In neonatal glomeruli, the labeling was most intense in those podocytes whose pedicel development corresponded to that seen in adult rat kidneys, whereas immature podocytes were poorly labeled. A quantitative evaluation of the labeling showed a highly significant correlation between the degree of podocyte development (as assessed by counting the number of pedicels per micrometer of basal lamina) and the intensity of H. pomatia lectin-gold particle labeling. These results show that the appearance of pedicels on developing podocytes is accompanied by the appearance of a specific cell coat component(s), detectable using H. pomatia lectin-gold complexes.

Acetylgalactosamine↗
PubMed1984

Perturbation of podocyte plasma membrane domains in experimental nephrosis. A lectin-binding and freeze-fracture study.

Alterations in the ultrastructural organization of podocyte plasma membrane domains were quantitatively assessed in puromycin aminonucleoside-treated rats by the use of 1) Helix pomatia lectin-gold complexes for detection of a specific glycocalyx component(s) normally associated with foot process bases and 2) freeze-fracture for detection of intramembrane particles and endocytotic invaginations on the plasma membrane. Lectin-binding sites were significantly reduced on podocyte foot process bases during the 7-day treatment period; and in freeze-fracture, the plasma membrane of the foot process base showed an increase in intramembrane particle number and size and an increased number of endocytotic invaginations, compared with the numbers in control animals. The cell body of nephrotic animals also had a significantly increased intramembrane particle density, compared with the control animals. These results provide direct evidence that the normal structure of specific plasma membrane regions is perturbed in podocytes that have lost their characteristic array of foot processes and support a role for these domains in the maintenance of normal podocyte architecture.

Animals↗
PubMed1983

A comparison of oxmetidine and cimetidine in the treatment of duodenal ulcer.

Oxmetidine (1 g/day), a new histamine H2-receptor antagonist, or cimetidine (1 g/day) was given to 30 patients with endoscopically proven duodenal ulcers in a randomised, double-blind trial. Ulcer healing was assessed endoscopically after four weeks' treatment, and again at eight weeks in those who had not healed in the first four weeks. Of the 15 patients receiving oxmetidine, 11 (73 percent) had healed their ulcers in four weeks, while 14 (93 percent) had healed their ulcers in eight weeks. Comparable healing rates were found with cimetidine, namely 13 of 15 (87 percent) after four weeks and all 15 patients (100 percent) after eight weeks. The patients were relieved of their symptoms to a comparable degree with both drugs. Weekly clinical, haematological and biochemical monitoring failed to reveal any relevant adverse effects except for a mild asymptomatic rise in serum creatinine levels with both oxmetidine and cimetidine.

Anti-Ulcer Agents↗
PubMed1983

Studies on the phi X174 gene A protein-mediated termination of leading strand DNA synthesis.

Recombinant RF (replicate form) I DNAs containing the bacteriophage phi X174 gene A protein-recognition sequence are cleaved by the phi X A protein yielding a phi X RF II X A protein complex (Zipursky, S.L., Reinberg, D., and Hurwitz, J. (1980) Proc. Natl. Acad. Sci. U.S.A. 77, 5182-5186). Such complexes support DNA synthesis in both RF I leads to SS(c) and RF I leads to RF I phi X DNA replication reactions in vitro. Two phi X A protein-recognition sequences were inserted into plasmid pBR322. Both sequences were contiguous with the same strand of the vector DNA and separated by 667 and 4275 base pairs. This recombinant plasmid (G27-4) was cleaved by the phi X A protein at either insert and both inserts support the initiation of RF leads to SS(c) DNA synthesis. This was verified by the finding that replication products were circular molecules of 667 and 4275 nucleotides. This finding is in keeping with the multifunctional activities associated with the phi X A protein; these include the site-specific nicking of RF I DNA which initiates DNA synthesis and site-specific termination resulting in the circularization of the displaced DNA strand. The phi X A protein and the Escherichia coli rep and SSb proteins catalyze the unwinding of phi X RF I DNA in vitro (Scott, J.F., Eisenberg, S., Bertsch, L.L., and Kornberg, A. (1977) Proc. Natl. Acad. Sci. U.S.A. 74, 193-197). Recombinant plasmid G27-4 RF I DNA was also unwound in vitro by this enzyme system; in this case, both circular and linear single-stranded DNA molecules of 667 and 4275 nucleotides, as well as full length circular single-stranded DNA were formed. Full length linear DNA was not detected. The two single-stranded circular DNA products formed as leading strands in RF leads to SS(c) reaction mixtures containing G27-4 RF I DNA differed in their ability to support lagging strand DNA synthesis. It was shown that the large single-stranded circular product included DNA sequences homologous to a replication factor Y effector sequence required for RF leads to RF and SS(c) leads to RF replication (Zipursky, S.L., and Marians, K.J. (1980) Proc. Natl. Acad. Sci. U.S.A. 77, 6521-6525). The 4275-nucleotide, but not the 667-nucleotide, single-stranded circular DNA product was converted to a duplex structure.

Bacteriophage phi X 174↗
PubMed1983

Thiazides. VIII: Dissolution survey of marketed hydrochlorothiazide tablets.

The dissolution profiles of 50-mg hydrochlorothiazide tablets representing all approved manufacturers (at the time of the study) were determined in two vehicles [purified water and dilute (1:100) hydrochloric acid] by three methods (rotating basket at 150 rpm; spin filter at 300 rpm; paddle method at 50 rpm). The paddle method was preferred on the basis of overall ease of operation, reproducibility, and discrimination. The paddle data were validated in both vehicles on the same lots of tablets by a second laboratory. A standard of not less than 80% dissolution in 60 min by the paddle method in water is proposed for hydrochlorothiazide tablets.

Chemistry, Pharmaceutical↗
PubMed1983

A comparison between a single agent short course chemotherapy regimen and a quadruple prolonged course regimen for small-cell bronchogenic carcinoma of limited extent.

Sixty-eight patients with inoperable but 'limited' stage small-cell carcinoma of the bronchus were treated with two different chemotherapy regimens. Thirty-four patients received methotrexate, cyclophosphamide, procarbazine and vincristine in standard dose over a 2-year schedule. Thirty-four patients received cyclophosphamide alone over a period of 3 months. The groups were evenly balanced with respect to clinical details which are fully described. Toxicity was acceptable. The median actual survival for the whole group was 11 months, the 1-year, 2-year and 4-year survival being 48%, 30% and 1.5% respectively. There was no statistically significant difference in survival between those classified as responders and those as non-responders, nor between the groups treated with the two different regimens. There was a high local recurrence rate.

Adult↗
PubMed1983

Ice nucleation and freezing in undercooled cells.

DSC has been employed to study the effect of cooling on a range of cells under exclusion of extracellular ice and in the absence of chemical cryoprotectants. In contrast to earlier reports, all the cells studied were found to freeze at temperatures above that indicated for homogeneous nucleation of ice in undercooled liquid water. In the case of human erythrocytes this temperature difference was only 0.5 degrees, but for yeast cells and cells of plant origin the difference amounted to congruent to 9 degrees. Nucleation of ice within the cell (or at the cell wall/membrane) must therefore be initiated by a heterogeneous mechanism. A kinetic analysis of the temperature dependence of nucleation shows the rates to be consistent with the dimensions of the plant cells (or organelles), if these were to be the active nucleators. However, the nucleation kinetics of human erythrocytes are extremely temperature sensitive, and the kinetic parameters only differ by small, though significant, extents from those of the suspension medium. Possible nucleation mechanisms are discussed in terms of the experimental data and the cell dimensions. Finally, one of the underlying assumptions of the kinetic analysis, i.e., that ice growth must be rapid compared to nucleation, has been tested and validated by freeze-fracture electron microscopy.

Calorimetry, Differential Scanning↗