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D Burton

Publications and source records attributed to D Burton.

14 recordsLinked to original sources
PubMed1992

A comparison of methods of measuring chromatic activity in the integument of a teleost.

1. Pallor induced by noradrenalin (5 x 10(-7) mol/kg) injection of dark Pseudopleuronectes americanus was measured as increase in skin reflectance and the degree of melanosome aggregation determined. 2. Mean skin reflectance increased approximately 30% on the Munsell neutral value scale. 3. At maximal mean reflectance, melanosomes were fully aggregated in most epidermal melanophores, but displayed more variable aggregation in dermal melanophores. 4. Individual reflectance estimates did not provide consistent indications of melanosome aggregation at maximum pallor. 5. The relative merits of reflectance and cellular methods of estimating melanophore activity are discussed with particular reference to this species.

Animals↗
PubMed1992

Skeletal muscle metabolism in the chronic fatigue syndrome. In vivo assessment by 31P nuclear magnetic resonance spectroscopy.

BACKGROUND: Previous study of patients with chronic fatigue syndrome (CFS) has demonstrated a markedly reduced dynamic exercise capacity, not limited by cardiac performance and in the absence of clinical neuromuscular dysfunction, suggesting the possibility of a subclinical defect of skeletal muscle. METHODS: The in vivo metabolism of the gastrocnemius muscles of 22 CFS patients and 21 normal control subjects was compared during rest, graded dynamic exercise to exhaustion and recovery, using 31P nuclear magnetic resonance (NMR) spectroscopy to reflect minute-to-minute intracellular high-energy phosphate metabolism. RESULTS: Duration of exercise was markedly shorter in the CFS patients (8.1 +/- 2.8 min) compared with the normal subjects (11.3 +/- 4.3 min) (p = 0.005). There were large changes in phosphocreatine (PCr), inorganic phosphate (Pi), and pH from rest to clinical fatigue in all subjects, reflecting the high intensity of the exercise. The temporal metabolic patterns were qualitatively similar in the CFS patients and normal subjects. There were early and continuous changes in PCr and Pi that peaked at the point of fatigue and rapidly reversed after exercise. In contrast, pH was relatively static in early exercise, not declining noticeably until 50 percent of total exercise duration was achieved, and reaching a nadir at 2 min postexercise, before rapidly reversing. There were no differences in pH at rest (7.08 +/- 0.04 vs 7.10 +/- 0.04), exhaustion (6.85 +/- 0.17 vs 6.76 +/- 0.17) or early (6.64 +/- 0.25 vs 6.56 +/- 0.24) or late recovery (7.09 +/- 0.04 vs 7.10 +/- 0.05), CFS patients vs normal subjects, respectively (NS). Neither were there intergroup differences (NS) in PCr or Pi. Although, quantitatively, the changes in PCr, Pi, and pH were marked and similar in both groups from rest to exhaustion, the changes all occurred much more rapidly in the CFS patients. Moreover, adenosine triphosphate (ATP) was significantly (p = 0.007) less at exhaustion in the CFS group. CONCLUSIONS: Patients with CFS and normal control subjects have similar skeletal muscle metabolic patterns during dynamic exercise and reach similar clinical and metabolic end points. However, CFS patients reach exhaustion much more rapidly than normal subjects, at which point they also have relatively reduced intracellular concentrations of ATP. These data suggest a defect of oxidative metabolism with a resultant acceleration of glycolysis in the working skeletal muscles of CFS patients. This metabolic defect may contribute to the reduced physical endurance of CFS patients. Its etiology is unknown. Whether CFS patients' overwhelming tiredness at rest has a similar metabolic pathophysiology or etiology also remains unknown.

Adenosine Triphosphate↗
PubMed1992

In vivo skeletal muscle metabolism during dynamic exercise and recovery: assessment by nuclear magnetic resonance spectroscopy.

BACKGROUND: The purpose of this study was to define temporally phosphorus metabolism and pH in the gastrocnemius muscles of 21 normal adult subjects during rest, dynamic exercise to exhaustion, and early and late recovery. METHODS: In vivo nuclear magnetic resonance spectroscopy. RESULTS: At rest, the ratio of phosphocreatine to the alpha peak of ATP averaged 2.26 +/- 0.25, the inorganic phosphate to ATP ratio averaged 0.31 +/- 0.08 and pH averaged 7.10 +/- 0.04. The phosphorus metabolites exhibited immediate and progressive changes with exercise, reaching their minimum (phosphocreatine, 0.95 +/- 0.41) or maximum (inorganic phosphate, 1.95 +/- 0.75) values at exhaustion, after an average exercise of 11 +/- 4 mins. In contrast, pH changed slowly during early exercise, but fell abruptly thereafter and averaged 6.76 +/- 0.17 at exhaustion. Phosphocreatine and inorganic phosphate began to return rapidly towards preexercise values immediately on cessation of exercise. However, pH declined further in the period immediately following cessation of exercise, reaching a nadir of 6.56 +/- 0.24 an average of 2 mins into recovery. Exercise duration did not correlate highly with any metabolic variable. CONCLUSIONS: The data support the concept that the metabolic physiology underlying physical exhaustion of dynamic exercising muscle is multifactorial. The post exercise drop in pH also suggests that normal subjects have a greater contribution to high energy phosphate production from glycolysis, as opposed to oxidative metabolism, in early recovery.

Acid-Base Equilibrium↗
PubMed1979

Nitrogen control in Salmonella: regulation by the glnR and glnF gene products.

The product of the glnR gene is required for nitrogen regulation of the synthesis of glutamine synthesis (Gln synthetase) [L-glutamate:ammonia ligase (ADP-forming), EC 6.3.1.2] and two periplasmic transport proteins that are subject to nitrogen control in Salmonella. Strains with mutations to loss of function of the glnR product [e.g., a strain with a Tn10 insertion or one with an ICR-induced (frameshift) mutation in glnR] have about 3% as much Gln synthetase as a fully derepressed wild-type strain and are unable to increase synthesis of this enzyme or periplasmic transport proteins in response to nitrogen limitation. The structural gene for Gln synthetase, glnA, and those for the periplasmic transport proteins are unlinked on the chromosome; thus, glnR appears to encode a diffusible positive regulatory element. Consistent with this, the mutant glnR allele is recessive to the wild-type allele with regard to expression of glnA (synthesis of Gln synthetase). Although glnR is closely linked to glnA, strains with mutations to complete loss of function of the glnR product can be distinguished from glnA strains by their ability to produce detectable Gln synthetase and to grow in the absence of glutamine. To demonstrate unequivocally that glnR is distinct from glnA, we have purified and characterized Gln synthetase from a strain with a Tn10 insertion in glnR. Because the properties of Gln synthetase from the insertion mutant, most importantly the carboxyl-terminal sequence of amino acids, are the same as those of synthetase from wild type, the Tn10 insertion cannot be in glnA (if it were, the carboxyl terminus of Gln synthetase would have to be altered); therefore we conclude that the Tn10 insertion is in a regulatory gene, glnR, which is distinct from glnA. A model for the function of the glnR product together with the previously defined glnF product in mediating nitrogen control is discussed.

Carrier Proteins↗
PubMed1979

[Dietary fiber].

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Cellulose↗
PubMed1978

Demonstration by immunoperoxidase histochemistry of calcitonin in the anterior lobe of the rat pituitary.

We have demonstrated by a specific immunoperoxidase procedure the presence of calcitonin-containing cells in the rat pituitary gland. These cells are widely distributed throughout the anterior lobe and seem to constitute the entire population of cells of the intermediate lobe. No such cells were seen in the posterior lobe. The presence of calcitonin-containing cells in the pituitary provides novel implications about the physiological significance of this hormone.

Animals↗
PubMed1977

Preliminary observations on an intervention program for heavy smokers.

Each of 571 smokers selected one of three methods of smoking cessation: group therapy, individual counseling, and hypnosis. One-year results suggest little difference between the three methods in producing ex-smokers. All methods produced an average success rate of approximately 20%. It should be noted, however, that with all types of verbal or verbally related therapy it is not known precisely how these techniques work or whether the outcomes are really a function of what is put into the therapy by the treatment agent and/or the recipient. It was generally found that younger, more educated smokers chose hypnosis; older, more educated smokers chose group therapy; and older, less-formally educated smokers chose individual counseling while the youngest and generally less educated smokers chose to become nonattenders and not take part in therapy. These results have important implications for designing optimal treatment programs which will be acceptable and effective for the greatest number of smokers.

Adult↗