PubMed Health⌕ Search

Biomedical subjects

S Wasserman

Publications and source records attributed to S Wasserman.

12 recordsLinked to original sources
PubMed1992

Ordering gene function: the interpretation of epistasis in regulatory hierarchies.

The order of action of genes in a regulatory hierarchy that is governed by a signal can often be determined by the method of epistasis analysis, in which the phenotype of a double mutant is compared with that of single mutants. The epistatic mutation may be in either the upstream or the downstream gene, depending on the nature of the two mutations and the type of regulation. Nevertheless, when the regulatory hierarchy satisfies certain conditions, simple rules allow the position of the epistatic locus in the pathway to be determined without detailed knowledge of the nature of the mutations, the pathway, or the molecular mechanism of regulation.

Animals↗
PubMed1992

Anti-CD4 antibodies are associated with HIV-1 seroconversion and may be detectable before anti-HIV-1 antibodies. The Multicenter AIDS Cohort Study.

We examined the sera from 14 HIV-1 seroconverters for the presence of autoantibodies against CD4. Anti-CD4 antibodies were detected in the serum of 11 of 13 HIV-1-infected persons at the time of HIV-1 seroconversion. In 6 of 14 persons from whom a serum was obtained prior to HIV-1 seroconversion, anti-CD4 antibodies were found 90 to 540 days before antibodies to HIV-1 were detectable. In comparison, anti-CD4 antibodies were present in only 7 serum samples from 62 HIV-1 seronegative individuals, including 50 from a seronegative homosexual male cohort. These results suggest that anti-CD4 antibodies are generated in response to early HIV-1 infection and possibly could be used as a marker for HIV-1 infection in some infected persons who are seronegative for HIV-1.

Autoantibodies↗
PubMed1991

Participation of Colorado pediatricians and family physicians in the Medicaid program.

The Pediatric Health Policy Group of the University of Colorado Health Sciences Center (Denver) surveyed 650 family physicians and 296 pediatricians in 1988, with 50% of family physicians and 48% of pediatricians responding. Half of the pediatricians in private practice and 35% of family physicians in private practice accepted all children who were Medicaid beneficiaries into their practice; 42% of pediatricians and 50% of family physicians accepted all non-Medicaid patients but only some new Medicaid patients; and 8% of pediatricians and 15% of family physicians accepted new non-Medicaid patients but no Medicaid patients. Practice location was associated with the level of Medicaid participation for these primary care physicians: Significantly more rural pediatricians and family physicians than those with urban practices accepted Medicaid patients. The average reimbursement level for these physicians was shown to be an important determinant of whether physicians would accept Medicaid patients. Nonparticipatory physicians were more concerned about excessive paperwork compared with physicians with limited participation. Among physicians with limited participation, family physicians and pediatricians both cited problems of excessive paperwork, reimbursement delays, and retroactive denials of payment as important deterrents to accepting Medicaid patients.

Colorado↗
PubMed1989

Bootstrapping: applications to psychophysiology.

This paper presents the statistical technique known as the bootstrap to the general audience of psychophysiologists. The bootstrap, introduced by Efron (1979), allows data analysts to study the distribution of sample statistics that might otherwise be too complicated to consider. The technique, which requires simple calculations, involves drawing repeated samples (with replacement) from the empirical--or the actual--data distribution and then building a distribution for a statistic by calculating a value of the statistic for each sample. The bootstrap can be used to obtain confidence intervals, standard errors, and even higher moments for the statistic. It is similar to the well-known jackknife of Quenouille and Tukey. After discussing the history and theory of both the bootstrap and the jackknife, we illustrate the use of the bootstrap in the statistical analysis of correlation coefficients and the general linear model.

Algorithms↗
PubMed1988

Dynamic measurement of human capillary blood pressure.

1. Capillary blood pressure was measured in man using a dynamic servo-nulling system and direct micropuncture. This enabled assessments of the normal variations in pressure which influence fluid filtration and reabsorption. 2. Seventy-eight capillaries in 19 subjects were punctured in one of three positions around the capillary loop with the hand at the level of the sternal angle. Mean pressure around the loop fell from 37.7 +/- 3.7 mmHg (arteriolar limb, mean +/- SEM, n = 12) to 19.4 +/- 1.0 mmHg (apex, n = 25) to 14.6 +/- 0.5 mmHg (venular limb, n = 41) at skin temperatures of 18.7-33.1 degrees C. These values agree closely with Landis' original studies in 1930 [E. Landis (1930) Heart, 15, 209-228]. 3. The mean filtration/reabsorption state of any particular capillary limb was not static because of cardiac, vasomotor and respiratory fluctuations in capillary pressure. From a total of 38 capillaries in which recordings were analysed for 30 s, the fluctuations in pressure were such that 27 capillaries probably had periods of both filtration and reabsorption. 4. Computerized superimposition and coherent averaging of trains of capillary pulses enabled an accurate description of the pulse waveform to be made in three capillaries. This was remarkably similar to waveforms from the radial artery, albeit at reduced amplitude (average 3.6 +/- 3.4 mmHg, mean +/- SD overall). The time for the pulse to travel between the radial artery and the finger capillary was approximately 10 ms, which implies a propagation velocity of several metres per second.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1977

Metabolism in rat lung tissue slices: technical factors.

We compared several sets of conditions used to estimate metabolism in rat lung slices. 14CO2 production from [14C]glucose, oxygen consumption, lactate production, and glucose consumption were used as measures of metabolic activity. The calculated results differed when we used 1) different techniques for estimating tissue weight, 2) tissue slices of 0.3-, 0.5-, 0.7-, and 1.0-mm thickness, 3) 95% air or 95% oxygen with 5% CO2 4) a delay after slice preparation and 4 degrees C and room temperature or periods of anoxia before incubation, 5) shaking rates of 60, 90, 120, or 150/min, 6) phosphate or bicarbonate buffers. Conditions of maximal activity were found using 95% O2 with 1.0-mm tissue slices, shaking at 120/min in phosphate buffer without periods of hypoxia or undue delays before incubation. Tissue weight should be obtained without exposure to aqueous solutions or dehydration by contact with cotton gauze or filter paper.

Animals↗
PubMedDate not supplied

Decision-making in child abuse and neglect.

Social attachment theory can be of value in examining the wide variety of abuse and neglect situations that come to the attention of authorities. We consider evaluation of the parent-child relationship as a crucial part of the judicial process. We have suggested parameters that can be used to evaluate the relationship. We have outlined some of the more common distortions in this relationship that have, in our experience, been associated with the mistreatment of children. The use of social attachment theory has been of great help in understanding the emotional reactions of the many children we have seen for evaluation and treatment. The theory also serves as a potential guide for improvements in social policy. If we are more sensitive to the psychological world of these children, we will be better able to truly protect them.

Affective Symptoms↗