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Biomedical subjects

E Clark

Publications and source records attributed to E Clark.

14 recordsLinked to original sources
PubMed1992

Multicenter study of change in dialysis therapy-maintenance hemodialysis to continuous ambulatory peritoneal dialysis.

Serial prospective observations were made on 40 patients with end-stage renal failure who transferred voluntarily from long-term maintenance hemodialysis (MHD) to continuous ambulatory peritoneal dialysis (CAPD). Adequate data were available through 6 months on CAPD in 26 participants, whereas 20 completed the study (1 year on CAPD). There were 12 (30%) treatment failures, including two deaths. Standard CAPD (four 2-L exchanges per day) proved to be inadequate therapy in large, young males with low total urea clearances (Ktu) on MHD. There was a large variation in Ktu within MHD and CAPD therapies that employed apparently similar or identical dialysis prescriptions; this underscores the need to quantify dialysis by a measure such as Ktu. Hematocrit, white blood cell (WBC) and platelet counts, and serum bicarbonate levels were significantly higher, whereas blood urea nitrogen (BUN) and serum potassium levels were significantly lower on CAPD than on MHD. While body weight, blood pressure, bone disease, parathyroid hormone (PTH) levels, and lipid profile did not change significantly, nutritional indices tended to decline with time on CAPD. Urea generation rate (Gu) decreased significantly after transfer to CAPD and correlated with Ktu regardless of treatment modality. Central nervous system (CNS) function reflecting uremic symptomatology and as indexed by average quantified electroencephalogram (EEG) discriminant scores did not change significantly. Hospitalization rates and stays were similar during equal time intervals on both therapies. Sufficiently diverse responses followed the MHD to CAPD therapy change to warrant more extended observations on larger numbers of patients.

Body Constitution↗
PubMed1991

Two new photoaffinity polyamines appear to alter the helical twist of DNA in nucleosome core particles.

Two new photoaffinity derivatives of polyamines have been synthesized by the reaction of spermine or spermidine with methyl 4-azidobenzimidate. The new compounds were purified chromatographically and characterized by several methods including proton magnetic resonance spectroscopy. The spermine derivative is N1-ABA-spermine [(azidobenzamidino)spermine], and the spermidine derivative is a mixture of N1- and N8-ABA-spermidine. ABA-spermine stabilizes nucleosome core particles in thermal denaturation experiments, with similar but not identical effects when compared with the parent polyamine, spermine. In circular dichroism experiments, ABA-spermine was capable of producing a B----Z transition in poly(dG-m5dC) at a concentration of 30 microM, compared with 5 microM required to produce the same effect with spermine. On the other hand, ANB-spermine [(azidonitrobenzoyl)spermine; Morgan, J. E., Calkins, C. C., & Matthews, H. R. (1989) Biochemistry 28, 5095-5106] stabilized the B form of poly(dG-br5dC). ABA-spermine is a potent inhibitor of ornithine decarboxylase from Escherichia coli, giving 50% inhibition at 0.12 mM, while ANB-spermine is a modest inhibitor, comparable to spermine or spermidine. Under conditions of nitrogen-limited growth, yeast take up ABA-spermine and ABA-spermidine at approximately one-third to half the rate of spermidine or spermine. In contrast, ANB-spermine was not significantly taken up. The photoaffinity polyamines were used to photoaffinity label the DNA in nucleosome core particles, and the sites of labeling were determined by exonuclease protection. All photoaffinity reagents showed both nonspecific labeling and specific sites of higher occupancy. However, the positions of the sites varied: the ANB-spermine sites confirmed those previously reported (Morgan et al., 1989); the ABA-spermine and ABA-spermidine sites were spaced at 9.8 bp intervals from the 3' end of each DNA strand. This observation, together with the effect of spermine on the circular dichroism of DNA in nucleosome core particles, implies that polyamines alter the helical twist of DNA in nucleosome core particles. The ABA-polyamines are offered as general-purpose photoaffinity polyamine reagents.

Affinity Labels↗
PubMed1990

Componential analysis as a way to investigate age-related changes in information processing.

The purpose of this paper is to alert researchers to the methods and utility of componential analysis as a means to examine age-related changes within information processing models of cognition. This analysis allows the researcher to determine which hypothesized information processing components are significant and the amount of variance shared with the dependent variable(s). Individual differences are investigated by modeling data at the individual subject level. Unstandardized regression weights are correlated with performance on a number of standardized ability tests to determine which components contribute to which abilities. The procedure combines complementary aspects of information processing analysis and psychometric analysis. Componential analysis is illustrated in this study with data from 60 individuals, aged 20 to 79, who solved verbal forced-choice analogies of the form A:B::C: (D1 or D2). Solution time and error rate data were modeled using a regression model developed by Sternberg (1977).

Adult↗
PubMed1977

Ileocolic intussusception--a case report.

The ultrasonic findings of a case of ileocolic intussusception are presented. The clinical findings usually seen in this condition are reviewed. The atypical presenting symptoms of adult forms of this condition are emphasized.

Aged↗
PubMedDate not supplied

Changes in analogical reasoning in adulthood.

This study sought to investigate adult intellectual development through an analysis of a particular type of cognitive ability, verbal analogical reasoning. The performance of 60 individuals between the ages of 20 and 79 was compared on 100 verbal analogies. The subjects consisted of six groups of ten individuals each (five males and five females), matched as a group for education and gender. Solution times and error rates served as the dependent measures. Results showed that there was a significant trend for the older subjects (60- and 70-year-olds) to be slower than the young subjects (20-, 30-, 40-, and 50-year-olds), but not necessarily more error prone. These data suggest that verbal analogical reasoning changes with age. Supplemental data demonstrated a change in other abilities as well (i.e., decline in perceptual-motor speed and spatial skill).

Adult↗
PubMedDate not supplied

15-hydroxyeicosatetraenoic acid synthesis from exogenous arachidonate by bronchial mucosa.

Arachidonate metabolism in bronchial mucosa was investigated. Bronchial biopsies from four asthmatics and three non-asthmatic controls were challenged with 300, 465, 650 and 960 mOsm/kg saline in the presence of [3H]arachidonate. Supernatants were analysed by reverse-phase high-performance liquid chromatography. The major arachidonate metabolite was identified as 15-monohydroxyeicosatetraenoic acid (15-HETE), with significantly higher production in biopsies from asthmatics than controls. Statistical analysis of the full model explained 81% of the variation (F = 14.8; df = 6, 21; P less than 0.001). Hyperosmolarity and the presence of sarcoid had no significant effect on 15-HETE synthesis, reducing R2 by only 6%.

Adult↗
PubMedDate not supplied

New ideas about self-tolerance and auto-immunity.

Recent advances in our understanding of B cell ontogeny strengthen the theory that self-tolerance is generated principally by clonal deletion. B cells pass through a stage: the "baby B cell", during which they are particularly susceptible to receptor cross-linking. Further evidence of clonal deletion comes from studies on the maintenance of the liver differentiation alloantigen F. In spite of this accumulating evidence room can still be found for the concept of immunological silence: it is a prediction of the dual recognition theory of T cell receptors that differentiation macromolecules which occur only on the surface of Ia negative cells cannot be seen by T helper cells.

Animals↗