Biomedical subjects
Publications and source records attributed to J L Wyatt.
This paper develops the network theory of chemical reaction systems from first principles. The network approach is then used to derive a canonical set of differential equations for reaction--diffusion systems, and an analysis of the Brusselator is presented as an example.
During November/December 1976 we surveyed 255 children of known age 5 years and under, and we questioned their parents about the foods given to them. We compared our results with previous survey results from this area. Despite the much earlier introduction of solid foods, there was no significant change in the mean weights of infants in this area since 1967. Sixty-four percent of the children were below 80% of the standard weight for age, and 57% of the children over one year of age had a mid upper-arm circumference of less than 14 cm. Health education needs to be supplemented by the use of high density weaning foods and the control of infection to overcome the very high prevalence of malnutrition.
Phosphorylation of spectrin in whole cells occurs on a single tryptic peptide and indicates a specific and limited modification of spectrin. Phosphorylation of spectrin in soluble extracts and isolated membranes is less specific. Diamide is an inhibitor of erythrocyte spectrin kinase and casein kinase. This agent also inhibits the restoration of biconcave morphology to metabolically depleted erythrocytes reincubated with adenosine.
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Rabbit muscle pyruvate kinase is irreversibly inactivated upon incubation with the adenine nucleotide analogue, 5'-p-fluorosulfonylbenzoyladenosine. A plot of the time dependence of the logarithm of the enzymatic activity at a given time divided by the initial enzymatic activity(logE/Eo) reveals a biphasic rate of inactivation, which is consistent with a rapid reaction to form partially active enzyme having 54% of the original activity, followed by a slower reaction to yield totally inert enzyme. In addition to the pyruvate kinase activity of the enzyme, modification with 5'-p-fluorosulfonylbenzoyladenosine also disrupts its ability to catalyze the decarboxylation of oxaloacetate and the ATP-dependent enolization of pyruvate. In correspondence with the time dependence of inactivation, the rate of incorporation of 5'-p-[14C]fluorosulfonylbenzoyladenosine is also biphasic. Two moles of reagent per mole of enzyme subunit are bound when the enzyme is completely inactive. The pseudo-first-order rate constant for the rapid rate is linearly dependent on reagent concentration, whereas the constant for the slow rate exhibits saturation kinetics, suggesting that the reagent binds reversibly to the second site prior to modification. The adenosine moiety is essential for the effectiveness of 5'-p-fluorosulfonylbenzoyladenosine, since p-fluorosulfonylbenzoic acid does not inactivate pyruvate kinase at a significant rate. Thus, the reaction of 5'-p-fluorosulfonylbenzoyladenosine with pyruvate kinase exhibits several of the characteristics of affinity labeling of the enzyme. Protection against inactivation by 5'-p-fluorosulfonylbenzoyladenosine is provided by the addition to the incubation mixture of phosphoenolpyruvate. Mg-ADP or Mg2+. In contrast, the addition of pyruvate, Mg-ATP, or ADP and ATP alone has no effect on the rate of inactivation. These observations are consistent with the postulate that the 5'-p-fluorosulfonylbenzoyladenosine specifically labels amino acid residues in the binding region of Mg2+ and the phosphoryl group of phosphoenolpyruvate which is transferred during the catalytic reaction. The rate of inactivation increases with increasing pH, and k1 depends on the unprotonated form of an amino acid residue with pK = 8.5. On the basis of the pH dependence of the reaction of pyruvate kinase with 5'-p-fluorosulfonylbenzoyladenosine and the elimination of cysteine residues as possible sites of reaction, it is postulated that lysyl or tyrosyl residues are the most probably candidates for the critical amino acids.
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To assess the importance and severity of measles in the Port Moresby area, 101 cases seen in hospital Out-Patients, and 26 cases seen in urban clinics during 1974, and 277 cases admitted during 1973-74, are analysed. The majority of cases were in children under 3 year of age. Of the 101 out-patients, only 19 had uncomplicated measles. 61 had pneumonia and 28 had gastro-enteritis. 19 needed admission to hospital. There were no deaths. Of the 277 admitted patients, 73% had pneumonia, 26% had gastro-enteritis and 22% were dehydrated. There were 6 deaths (a case mortality rate of 2.2%). All the children who died had pneumonia; 4 children developed tuberculosis. The disease appears to be more severe in Papua New Guinea than in most developed countries tough less severe than in many other developing countries. We estimate that the cost of treating measles is about K25,205 per annum. The introduction of measles vaccination might reduce the cost of measles to the community by K14,000 per annum, and would save children from an unpleasant and often serious disease.
A preliminary study of nine children under five years of age admitted to Port Moresby General Hospital with acute gastro-enteritis showed that five (56%) were excreting duovirus in their stools as shown by electron microscopy. Duovirus was not demonstrated in the stools of any of eight children with gastro-enteritis seen at Kainantu Health Centre.