PubMed Health⌕ Search

Biomedical subjects

W Wong

Publications and source records attributed to W Wong.

9 recordsLinked to original sources
PubMed1992

Suppression of longitudinal versus transverse conduction by sodium channel block. Effects of sodium bolus.

BACKGROUND: Arrhythmias resulting from treatment with sodium channel-blocking antiarrhythmic drugs have been successfully treated with sodium infusion, although the mechanism underlying this effect is uncertain. METHODS AND RESULTS: In this study, we used a multielectrode array to examine the effects of O-desmethyl encainide (ODE), a potent sodium channel-blocking metabolite of encainide, on conduction in canine ventricle. ODE depressed both longitudinal and transverse conduction velocities in a plasma concentration-related fashion (r = -0.74, -0.60; p less than 0.001). At ODE concentrations less than or equal to 300 ng/ml (n = 34), conduction velocity was depressed to the same extent in the longitudinal (-21.9 +/- 8.4%, SD) and transverse orientations (-22.0 +/- 8.8%). However, at concentrations greater than 300 ng/ml (n = 17), conduction was significantly more impaired longitudinally than transversely (-44.5 +/- 11.7% versus -34.4 +/- 13.7%, p less than 0.02). In 12 animals with high concentrations (mean, 432 +/- 32 ng/ml), a 5-meq/kg bolus of sodium chloride over 1 minute immediately increased conduction velocity; this effect was significantly greater and longer lasting in the longitudinal orientation. In two animals, conduction block in the longitudinal orientation was documented at high plasma ODE and was immediately reversed by sodium bolus. CONCLUSIONS: We conclude that the major effect of sodium in animals with excess sodium channel block is improvement of longitudinal propagation; this effect may underlie the antiarrhythmic action of sodium in the analogous clinical setting.

Animals↗
PubMed1979

Cell envelope of Neisseria gonorrhoeae CS7: peptidoglycan protein complex.

Treatment of cells grown to exponential phase with 4% sodium dodecyl sulfate for 3 h at 100 degrees C resulted in solubilization of all cellular components except for peptidoglycan. In most strains, cells cultured in liquid gonococcal broth at pH 7.2 yielded a peptidoglycan composed primarily of N-acetylmuramic acid N-acetylglucosamine, alanine, glutamic acid, and diaminopimelic acid in a molar ratio of 1:1:2:1:1. The peptidoglycan in these cells accounted for 1 to 2% (dry weight) of the cells. However, in cells cultured at pH 6.0, the dry weight of peptidoglycan increased to 4 to 13%. Preliminary investigations indicated that the apparent increase in weight is strain dependent and is due in part to associated protein(s). Neisseria gonorrhoeae strain CS7 had elevated amounts of protein associated with the peptidoglycan regardless of growth pH. The peptidoglycan-protein complex could not be dissociated by additional extraction with sodium dodecyl sulfate, 10 M LiCl2, or ethylenediaminetetraacetate or by 7.5% polyacrylamide gel electrophoresis. The complex could be degraded by lysozyme, trypsin, chymotrypsin, Pronase B, and Chalaropsis sp. muramidase.

Amino Acids↗
PubMed1979

Local xenogeneic graft-vs-host reaction: a practical assessment of T cell function among cancer patients.

The local xenogeneic graft-vs-host reaction (XGVHR) was used as a practical bioassay to assess T lymphocyte function and immunocompetence among cancer patients. Positive XGVHR was found in 99.5% of normal donors, 70% of cancer patients with early stage disease, and 30% of cancer patients with metastatic disease (p less than 0.001). A minimum of 4.5 x 10(6) immunocompetent T lymphocytes are necessary in order to elicit a positive XGVHR. Negative reactions among cancer patients are characterized by the lack of edema fluid accumulation and the appearance of the most basophils at the test site. This suggests that insufficient amounts of lymphokines are being released by the incompetent T lymphocytes, whereas the host is capable of mounting a rejection reaction as evidenced by the appearance of the basophils. Preliminary evidence suggests that the immunologic defect detected by the XGVHR cannot be corrected by monocyte depletion. The identification of putative suppressor T cell subsets may bear immunotherapeutic implications in the future.

Animals↗
PubMed1978

Regulation of bacterial cell walls: correlation between autolytic activity and cell wall turnover in Staphylococcus aureus.

Cell wall turnover was examined in parent and mutant strains of Staphylococcus aureus. Peptidoglycan and teichoic acid were observed to undergo turnover in the wild-type strain during exponential growth; however, the rate of turnover did not decrease when the growth rate slowed, as the culture entered stationary phase. Isolated native cell walls and crude soluble autolytic enzyme were prepared from cells harvested during exponential and postexponential phases of growth. Native cell walls from both phases of growth autolyzed in buffer at identical rates; similarily, crude soluble enzyme from both preparations degraded radioactive cell walls at the same rate. Therefore, the activity of the autolysin in both exponential and postexponential cells was similar. The autolysis of whole cells of a mutant tar-1 was enhanced by 1.0 M NaCl. When 1.0 M NaCl was present under growing conditions, the rate of cell wall turnover was greatly increased. The presence of chloramphenicol, which inhibits whole-cell autolysis, also inhibited turnover. Analysis of the cell wall material recovered from spent medium revealed products consistent with the known mode of action of the endogenous autolysin. It is concluded that cell wall turnover in S. aureus is independent of the stage of culture growth but is dependent instead on the activity of the autolysin.

Bacteriolysis↗
PubMed1976

Isolation and characterization of a mutant of Staphylococcus aureus deficient in autolytic activity.

A mutant of Staphylococcus aureus H (RUS3) uas isolated after mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine. The rate of autolysis of whole cells and isolated cell walls of RUS3 was less than 10% of the parent strain. In addition, the ability of the crude soluble enzyme isolated from RUS3 to degrade cell walls was negligible compared with the parent strain. The cell wall composition and the generation time of RUS3 were comparable to the parent strain. Unlike S. aureus H, RUS3 grew in clumps and did not undergo cell wall turnover. Both strains exhibited identical kinetics of killing by penicillin G. This may indicate that autolytic enzymes play a role in cell wall turnover and cell separation, but in S. aureus most of the autolytic activity is unrelated to the lethal effect of cell wall antibiotics.

Amidohydrolases↗
PubMed1975

Radiologic detection and prostatic carcinoma by double contrast retrograde urethrocystography.

A method of radiologic visualization of the male urethra especially for detecting prostatic carcinoma is reported. This method is called double contrast retrograde urethrocystography and is similar to that of Flocks in combining air cystography and retrograde urethrography but it differs in the manner of making the exposure. In our method the exposure is made with the patient in an exaggerated Trendelenburgs position to allow the contrast medium injected into the bladder to accumulate at the dome. Thus, in the urethrocystogram obtained by this method, the bladder neck and the prostatic urethra immediately adjacent to it are always clearly visualized unlike that obtained by conventional retrograde urethrography, evacuation cystourethrography and sometimes even the method of Flocks, in which these regions are prone to be covered and masked by the contrast medium injected and accumulated in the bladder. Therefore, with our method the radiological detection and differentiation of the malignant lesion involving these regions are more accurate and definite. From our clinical experiences the mode of compression and displacement caused by benign prostatic hypertrophy is continuous and regular, while that caused by prostatic carcinoma is interrupted, irregular and with moth-eaten and granular defects. Four cases are reported.

Aged↗