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Biomedical subjects

D Hall

Publications and source records attributed to D Hall.

At least 19 recordsLinked to original sources
PubMed1992

Hyalin, a sea urchin extraembryonic matrix protein: relationship between calcium binding and hyalin gelation.

The protein hyalin, a major component of the sea urchin extraembryonic hyaline layer, was previously shown to undergo a Ca(2+)-induced self-association into large aggregates (gelation). This reaction represented a major step in assembly of the layer. In the experiments reported here, digestion with trypsin resulted in a rapid dissociation of hyalin into a mixture of peptides which retained the capacity to bind Ca2+. However, unlike intact hyalin, none of these peptides associated into large aggregates (gelation) in the presence of Ca2+, Mg2+, and NaCl. Loss of the ability to undergo gelation was not accompanied by any significant change in the content of acidic plus amide amino acid residues. Decreasing the pH to 5.6 resulted in a loss of 25% of hyalin's Ca(2+)-binding capacity but had no effect on the ability of the protein to undergo gelation. Peptide fragments were only partially effective at inhibiting hyalin gelation. Clearly, not all the Ca(2+)-binding sites were required for hyalin gelation and Ca2+ binding alone was insufficient to drive this reaction. In addition, hyalin appeared to possess two classes of protein-protein interaction domains, one of which was essential for gelation.

Amino Acids↗
PubMed1992

Gastroschisis wringer clamp: a safe, simplified method for delayed primary closure.

When primary abdominal wall closure in a newborn with gastroschisis cannot be accomplished safely, placement of a reinforced Silastic silo facilitates delayed primary closure (DPC). In this report we describe our experience with the gastroschisis wringer clamp (GWC). The GWC is an autoclavable, 140-g, aluminum alloy device reminiscent of an old wringer washing machine. It consists of two apposing serrated rollers that pull the Silastic silo through a slotted base plate. This protects the intestine and converts the circular defect into a vertical slit to ease DPC. The GWC is adjusted daily on the awake newborn in the nursery and the magnitude of each adjustment is gauged by the infant's cardiac and pulmonary status. For the past 10 years we have cared for 116 newborns with gastroschisis. The average birth weight was 2,530 g (range, 1,380 to 3,300 g). Eighty-six infants (74.1%) have undergone primary closure. The remaining 30 infants (25.9%) were treated by placement of a Silastic silo and application of the GWC, forming the basis of this report. The DPC operation was performed an average of 6.7 days (range, 3 to 23 days) following the application of the silo. Extubation was usually possible prior to the DPC, with the mean length of mechanical ventilation being 3.8 days. Three patients developed serious complications including two dehiscences of the silo-fascia interface. There were no deaths in this group of 30 patients. The GWC offers many technical advantages and can be easily reversed when the infant's cardiopulmonary status deteriorates. We advocate its adoption as a method of choice in the newborn with gastroschisis who requires DPC.

Abdominal Muscles↗
PubMed1992

Counteraction of the vasodilator effects of enalapril by aspirin in severe heart failure.

OBJECTIVES: This study was undertaken to determine if a standard dose of aspirin interacts relevantly with the circulatory effects of enalapril in severe heart failure. BACKGROUND: The frequent association of heart failure with coronary artery disease confers potential for combined treatment with an angiotensin-converting enzyme inhibitor and the prostaglandin synthesis inhibitor aspirin, the pharmacodynamic actions of which are, in part, mutually opposed. METHODS: In 18 patients, on 3 consecutive days, hemodynamic measurements were performed at baseline and 4 h after administration of a double placebo, enalapril (10 mg) plus placebo and enalapril plus aspirin (350 mg) according to a double-blind, randomized, crossover protocol. RESULTS: Enalapril given before aspirin led to significant decreases in systemic vascular resistance, left ventricular filling pressure and total pulmonary resistance together with a significant increase in cardiac output. When given with or on the day after aspirin, enalapril did not elicit significant changes in any of these variables. There was a clear tendency to lower values for pulmonary artery pressure on all regimens, and slowing of the heart rate was incurred whether or not aspirin had been given. Chi-square analysis of the individual responses showed that the probability of effecting a decrease in systemic vascular resistance > or = 300 dynes.s.cm-5 was six times greater when enalapril was given without aspirin (p < 0.01). CONCLUSIONS: In severe heart failure, the prostaglandin synthesis inhibition by aspirin counteracts the systemic arterial vasodilation of angiotensin-converting enzyme inhibition with enalapril and substantiates its dependence on the integrity of prostaglandin metabolism. Trends toward reductions of pulmonary artery pressure and slowing of the heart rate were still observed, presumably subsequent to lowered norepinephrine concentrations indicating maintenance of prostaglandin-independent actions of angiotensin-converting enzyme inhibition.

Adult↗
PubMed1991

The research imperative and bureaucratic control: the case of clinical research.

This paper examines the development of Research Ethics Committees and explores some of the conflicts of value and role which surround the practice of medical research. The case of medical research on children is discussed as one which raises in an acute form concerns about consent and risk/benefit analysis. The paper draws on a survey of Research Ethics Committees to illustrate their variety of structure and functioning, and to relate current practice to a model of bureaucratic control. Bureaucracy is considered both in its common-sense understanding of officious rule-making and delay, and in its theoretical formulation in terms of specialisation, standardisation, formalization and centralisation of procedures. It is argued that the concept of bureaucracy can aid an understanding of the problems of control over research, as well as providing a model for more informed, consistent and open decision making.

Child↗
PubMed1991

The St Croix disaster and the National Disaster Medical System.

The National Disaster Medical System was designed to respond to a catastrophic disaster by creating a group of specially trained civilian disaster medical assistance teams. The teams would be transported to the periphery of the event to triage, stabilize, and then prepare victims for evacuation to facilities elsewhere in the United States that have agreed in advance to accept such patients. Hurricane Hugo's devastation in St Croix offered the first opportunity to test the system. The event was an example of a type of medical disaster that resulted in a sudden reduction in medical resources without a great increase in casualties. Background information and operation of the New Mexico disaster medical assistance team are presented with a clinical profile of the patients seen during the disaster. We describe the first actual deployment of a disaster medical assistance team and the issues that must be addressed before future deployments.

Disaster Planning↗
PubMed1991

Clumsiness in children--do they grow out of it? A 10-year follow-up study.

The question of whether problems of motor co-ordination in early childhood recede with age has rarely been addressed. This paper reports the findings from a follow-up study of 17 children, identified by their teachers as having poor motor co-ordination at age six. Now age 16, these children and their matched controls completed a battery of assessments. The results suggest that the majority of children still have difficulties with motor co-ordination, have poor self-concept and are experiencing problems of various kinds in school. However, there are individual differences in the extent to which the children have learned to cope with their continuing difficulties over the years.

Achievement↗
PubMed1991

Copper loading of hearts increases postischemic reperfusion injury.

We studied the role of copper as a potential mediator of postischemic reperfusion injury in the isolated, perfused rat heart. Hearts were equilibrated with Krebs-Henseleit buffer for 10 minutes and then loaded with copper by way of perfusion with buffer containing 20 microM copper(II)-bis-histidial for 30 minutes. Control hearts were perfused with Krebs-Henseleit buffer alone during the loading period. Hearts than were washed with buffer for 10 minutes and subjected to 20 minutes of normothermic global ischemia followed by 30 minutes of reperfusion. Atomic absorption spectroscopy revealed a 67% increase in total copper content in loaded hearts by the end of the wash. By the end of the 30-minute period of reperfusion, control hearts demonstrated a 50-60% recovery of myocardial function as determined by peak systolic pressure, contractility, and heart rate. In contrast, copper-loaded hearts exhibited virtually no functional recovery within the 30-minute time period. Using salicylate as a probe, we determined that peak and duration of .OH formation appears to be increased in copper-loaded hearts during reperfusion. Furthermore, efflux of lactic dehydrogenase was significantly increased in copper-loaded hearts. Our results clearly demonstrate that increasing cardiac content of copper results in enhanced postischemic reperfusion injury associated with increased formation of .OH, thus suggesting an important catalytic role for this transition metal.

Analysis of Variance↗
PubMed1990

Comparison of enzyme immunoassay with radioimmunoassay for the detection of antibody to hepatitis B core antigen as the only marker of hepatitis B infection in a population with a high prevalence of hepatitis B.

Enzyme immunoassay (EIA) and radioimmunoassay (RIA) for the detection of antibody to hepatitis B core antigen (anti-HBc) were compared using serum specimens from Alaska Natives screened during a hepatitis B control program that were initially positive by EIA for only anti-HBc. Of 36 specimens from persons previously HBsAg positive but who were now only anti-HBc positive by EIA, 94.4% were anti-HBc positive by both assays, with anti-HBc levels exceeding 93% inhibition. Low-level antibody to hepatitis B surface antigen (anti-HBs) (less than 10 SRU) and antibody to hepatitis Be (anti-HBe) were also present in 50% and 48% of specimens positive for anti-HBc, respectively. Of 148 specimens from persons initially positive for only anti-HBc by EIA who had no previous documentation of any hepatitis B virus (HBV) infection, 64.5% were positive by repeat testing for anti-HBc by both assays, and anti-HBc levels in this sample exceeded 70% in 91.6% and 80.2% of specimens by EIA and RIA, respectively. Low-level anti-HBs and anti-HBe were present in 45.8% and 15.6%, respectively. EIA detection of anti-HBc was found to be less specific than RIA. Of specimens positive for anti-HBc by EIA, 14.8% were negative by RIA. The specificity of the EIA could be improved with respect to RIA by increasing the cut-off from 48% to 68%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Use of salicylate as a probe for .OH formation in isolated ischemic rat hearts.

Salicylic acid was used as a probe for .OH formed during reperfusion of the ischemic myocardium. .OH adds to the phenolic ring of salicylate to yield dihydroxybenzoic acid species. The two principal dihydroxybenzoic acids formed are the 2,3- and 2,5-derivatives and can be isolated and quantitated using HPLC combined with electrochemical detection. In these experiments, dihydroxybenzoic acids were detectable in the f molar range. Rat hearts were perfused in the Langendorff mode with Krebs-Henseleit buffer containing 100 microM salicylate. Following 20 min of global ischemia a 173% increase in tissue content of 2,5-dihydroxybenzoic acid was detected after 2.5 min of reperfusion. The duration of ischemia did not significantly affect tissue content of 2,5-dihydroxybenzoic acid peaked at 250 to 300% of control within 2.5 min of reperfusion. The inclusion of 100 microM salicylate in the perfusion buffer had no effect on myocardial function during the duration of the experiments. The results indicate that salicylate can be used as a very sensitive probe for .OH in the isolated ischemic heart.

Animals↗