Search PubMed⌕ Search

Biomedical subjects

E Clark

Publications and source records attributed to E Clark.

At least 73 records · Page 4Linked to original sources
PubMed1996

Children and adolescents with neurofibromatosis 1: a behavioral phenotype.

Twenty 6- to 17-year-old children with neurofibromatosis 1. (NF1) were compared to 20 age- and sex-matched siblings on a wide range of neuropsychological and behavioral dimensions. In familial cases, diagnostic status was confirmed by gene linkage with greater than 98% accuracy. Visual examinations that included assessments of visual evoked responses (VER) were performed on subjects with NF1. Forty-two percent of NF1 subjects had abnormal VER and underwent magnetic resonance imagery or computed tomography scans of the brain. On a variety of skills, subjects with NF1 performed more poorly than unaffected siblings. Children with NF1 were found to be less competent on measures of cognitive, language, and motor development, visual-spatial judgment, visual-motor integration, and academic achievement. Learning disabilities were common in children with NF1. Parents and teachers reported that NF1 subjects had internalizing problems and difficulty interacting with peers. A behavioral phenotype for NF1 and recommendations for preventative interventions are proposed.

Adolescent↗
PubMed1995

High morbidity rate after converted laparoscopic colorectal surgery.

Sixteen of 65 laparoscopically assisted colorectal operations were converted to an open procedure, usually because of dissection difficulties. Conversion was decided early in the procedure in four cases without perioperative morbidity and later in 12 cases, after a mean of 56 min. The results in patients undergoing converted operation were compared with those in 252 having a planned open colorectal procedure during the same period. The groups were comparable with regard to age, health status, factors influencing intestinal healing and grade of surgeon. A higher postoperative morbidity rate (50 versus 21 per cent) and more anastomotic leakages (25 versus 8 per cent) were apparent in the converted group. Operating time, postoperative ileus and hospital stay were longer in those requiring a converted operation. These poor results suggest that careful preoperative patient selection for laparoscopic procedures and a rapid decision to convert in case of difficulty are important.

Adolescent↗
PubMed1995

Effects of recombinant human hemoglobin on motor functions of the opossum esophagus.

Chemically altered hemoglobins are being investigated as blood substitutes. They may affect numerous biological processes since free hemoglobin binds nitric oxide (NO). Nitric oxide is a neural mediator of relaxation of the lower esophageal sphincter (LES) and esophageal peristalsis. We hypothesize that recombinant human hemoglobin (rHb1.1) alters esophageal motor function by scavenging NO. Contraction of transverse muscle strips from the opossum esophagus and LES was monitored. Transmembrane potential differences of circular smooth muscle from the esophagus were recorded using glass microelectrodes. Intrinsic esophageal nerves were stimulated electrically. Esophageal manometries were performed with a low-compliance perfused-catheter system. The activity of the enzyme NO synthase was determined with the citrulline assay. Recombinant hemoglobin diminished nerve-induced relaxation of LES muscle but did not alter LES tone. Circular esophageal muscle responded to nerve stimulation with an inhibitory junction potential and a mechanical off response. Recombinant hemoglobin diminished the inhibitory junction potential and shortened the latency of the off response. It increased the velocity of esophageal peristalsis, decreased the amplitudes of these contractions and diminished LES relaxation. Cyanomethemoglobin had little effect on nerve- or swallow-induced responses. Hemoglobin did not inhibit the activity of NO synthase. Recombinant human hemoglobin appears to alter esophageal motor function by scavenging NO.

Amino Acid Oxidoreductases↗
PubMed1994

Cloning cassettes containing the reporter gene xylE.

Two pUC-derived vectors containing the promoterless xylE gene (encoding catechol 2,3-dioxygenase) of Pseudomonas putida mt-2 were constructed. The t(o) transcriptional terminator of phage lambda was placed downstream from the stop codon of xylE. The new vectors, pXT1 and pXT2, contain xylE and the t(o) terminator within a cloning cassette which can be excised with several endonucleases. When inserted into a transcribed sequence, this xylE cassette reports promoter activity and interrupts downstream transcription of the target sequence.

Bacteriophage lambda↗
PubMed1994

The impact of laparoscopic cholecystectomy in Canada and Australia.

The introduction of laparoscopic cholecystectomy in Canada and Australia has been associated in each country with an increase in the rates of all cholecystectomies following a period where these had remained constant. Estimated costs of cholecystectomies to health programs declined by about 13% in Canada after the laparoscopic procedure became widely available, and about 2% in Australia. Days lost to patients because of surgery, and associated costs to them, decreased in each country. Neither country is realising the potential savings through use of laparoscopic cholecystectomy because of the increase in the number of procedures. The utility of these additional operations remains unclear. These trends associated with the advent of laparoscopic cholecystectomy suggest the need for caution in the introduction and application of other minimal-access surgery techniques.

Australia↗
PubMed1994

Open learning: the state of the art in nursing and midwifery.

In this paper the authors examine the differences between open and distance learning and describe a framework based on the two dimensions of contiguity and openness to identify four 'ideal type' teaching situations. In the second part of the paper, recent developments in higher education are summarised and the shift towards increased flexibility of education provision is highlighted. Finally, it is argued that alongside the debate about definitions and educational philosophies, there is an urgent need to evaluate the effectiveness of open and distance learning systems. Personal beliefs and assertions about the benefits of open/distance learning need to be replaced by sound evidence.

Education, Nursing↗
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↗
PubMed1989

Analogical reasoning abilities of recovering alcoholics.

This study investigated analogical reasoning abilities of alcoholics who had been abstinent from alcohol for at least 1 year. Their performance was compared to that of nonalcoholic controls matched as a group for education, age, and gender. Solution times and error rates were modeled using a regression model. Results showed a nonsignificant trend for alcoholics to be faster, but more error prone, than controls. The same componential model applied to both groups, and fit them equally well. Although differences have been found in analogical reasoning ability between controls and alcoholics immediately following detoxification, we find no evidence of differences after extended periods of sobriety.

Adult↗
PubMed1988

Alpha-2-adrenoceptor function in alcohol withdrawal: a pilot study of the effects of iv. clonidine in alcoholics and normals.

Central alpha-2-adrenoceptor function was studied in seven withdrawing alcoholics and compared with seven normal controls using the clonidine challenge test. The alcoholic group had significantly elevated basal levels of blood pressure and plasma 3-methoxy-4-hydroxy-phenyl glycol. The percentage of fall in blood pressure produced by clonidine was blunted in the alcoholics. There was disruption of the neuroendocrine effects of clonidine on growth hormone release. Physiological indices of withdrawal, in particular plasma 3-methoxy-4-hydroxyphenyl glycol and blood pressure correlated with measures of previous withdrawal experiences, supporting the idea that kindling might occur with repeated episodes of withdrawal.

Adult↗