Biomedical subjects

D Zucker

Publications and source records attributed to D Zucker.

22 records · Page 2Linked to original sources

PubMed1978

Dissociation of plasminogen activator from the transformed phenotype in a 5-bromodeoxyuridine dependent mutant of Syrian hamster melanoma cells.

The relationship between plasminogen activator levels and the expression of the transformed phenotype was studied in a 5-bromodeoxyuridine (BrdUrd) dependent mutant of Syrian hamster melanoma cells. In terms of cell morphology and cellular interactions, the BrdUrd dependent cells resemble transformed cells when grown in the presence of BrdUrd but resemble untransformed cells when grown in the absence of BrdUrd. It was found that the BrdUrd dependent cells release significant levels of plasminogen activator only when cultured in the absence of BrdUrd. In the presence of BrdUrd, the release of plasminogen activator by the dependent cells is suppressed, and the decreased level of plasminogen activator released in the presence of BrdUrd seems to be due to the decreased production of active enzyme. Growth tests revealed that the BrdUrd dependent cells, when attached to a substrate, required BrdUrd in order to attain high densities. Furthermore, the cells are able to grow well in soft agar only in the presence of BrdUrd. These results suggest that the production and release of high levels of plasminogen activator are not related (either as cause or effect) to the expression of the transformed phenotype in the BrdUrd dependent cells. The effect of dog serum (as a plasminogen source) on the BrdUrd dependent cells also was tested. It was found that cells cultured in medium containing dog serum exhibit a morphological alteration, but only in the absence of brdUrd. The morphological response of the cells to dog serum resembles that previously observed with virus-transformed cells. In the BrdUrd dependent cells, the morphological response to dog serum appears correlated with the release of plasminogen activator but separated from other transformed characteristics.

Blood↗

PubMedDate not supplied

Testing for differences in changes in the presence of censoring: parametric and non-parametric methods.

Some commonly used parametric and non-parametric methods for analysing repeated measures with incomplete observations are briefly reviewed. The performances of these methods in the presence of completely random, as well as informative censoring are compared in simulated experiments generated under the linear random effects model with parameter values derived from realistic examples. The effects of some moderate model deviations are also compared. The results indicate that in the presence of informative censoring, the usual parametric and nonparametric methods derived under the assumption of random censoring could either suffer severe loss of power or provide false positive results. The conditional linear model for informative censoring when used in conjunction with the bootstrap variance estimation procedure performed well under both random and informative censoring mechanisms. The non-parametric procedure obtained by ranking the individual summary statistics, although not as efficient as the conditional linear model with robust variance, also performed relatively well in most situations. Therefore, in situations in which informative censoring is likely to occur it is important to select the proper method of analysis to test for the informativeness of censoring and to account for its effects.

Bias↗

PubMedDate not supplied

Association between low plasma tryptophan and blackouts in male alcoholic patients.

Alcohol has been observed to alter various aspects of memory function. Some of the most extreme forms of memory impairment experienced by alcoholics are blackouts. There are at present very few data on the biological mechanisms underlying alcohol-related memory impairment. A variety of mechanisms including the cholinergic and catecholaminergic systems have been implicated in learning and memory. More recently, however, the importance of the serotonergic system in memory function has been demonstrated. We investigated whether patients with a history of blackouts had lower plasma levels of the serotonin precursor tryptophan than patients without such a history. Tryptophan values were significantly lower in patients who had experienced blackouts than in patients who had not. No significant differences between the two group of patients were observed for other amino acids sharing with tryptophan the same transport carrier into the brain. Drinking history variables did not differentiate among the two patient groups. Our data suggest that a decrease in plasma tryptophan (and concomitant lowered brain serotonin) could increase the vulnerability of certain individuals to manifestations of various aspects of memory impairment including one of its most extreme forms, the blackout.

Adult↗

PubMedDate not supplied

Variation in mortality among seven hemodialysis centers as a quality indicator.

OBJECTIVES: To identify patient attributes that were associated with increased mortality; variables that were associated with process of care that were correlated with mortality; and outlier centers after adjustment for patient attributes. DESIGN: Standard interviews were conducted by trained nurses with all patients. Detailed information regarding primary renal diagnosis, comorbidity, and results of laboratory tests were obtained from the medical charts. The vital status of the patients was obtained from the records of each of the centers. We used the Cox hazard method to identify variables that correlated with a 1-year mortality. Centers with observed mortality exceeding the 95% confidence interval (CI95) of the expected probability of death were marked as outliers. SETTING: Seven dialysis centers located in large teaching hospitals in Israel. PATIENTS: The current study included patients > 16 years of age who had undergone hemodialysis > 4 weeks prior to the day of data collection. RESULTS: The study included 564 patients. Significant differences were found in patient demographics and process variables among the centers. The following variables correlated with mortality; diabetes (odds ratio [OR], 2.03; CI95, 1.28-3.21); ischemic heart disease (OR, 2.2; CI95, 1.39-3.49); each year of age (OR, 1.04; CI95, 1.02-1.06); each 1 g% of albumin (OR, 0.51; CI95, 0.30-0.86). The average observed mortality in all centers was 17.4%. After adjustment for casemix, one center showed excess mortality (24% observed compared to 15% expected after adjustment for patient attributes; CI95, 6.2-23.7). CONCLUSIONS: The ability to compare mortality rates among dialysis centers to detect possible quality outliers depends on thorough consideration of patient attributes and random variation.

Adolescent↗