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Biomedical subjects

P Mitchell

Publications and source records attributed to P Mitchell.

At least 505 records · Page 28Linked to original sources
PubMed1980

The prevalence of diabetic retinopathy: a study of 1300 diabetics from Newcastle and the Hunter Valley.

This paper examines the prevalence of retinopathy in 2 diabetic populations from the Newcastle and Hunter Valley regions. Overall, 49% of patients attending a large diabetic clinic had retinopathy. 15% had proliferative retinopathy, macular involvement or threatened macular involvement, the stages of retinopathy in which photocoagulation may be indicated to preserve vision. A comparable study of known diabetics in the town of Singleton demonstrated prevalence rates of 36% and 11% respectively. The close relationship of retinopathy prevalence to the duration and age at onset of diabetes is also presented, and simple guidelines for the planning of eye examinations for diabetics are proposed.

Adolescent↗
PubMed1980

Study of cardiac rhythm in healthy newborn infants.

Twenty-four-hour electrocardiograms were recorded in the first 10 days of life on 134 healthy full-term infants with birthweights greater than 2.5 kg. The highest heart rate a minute, measured over nine beats, was 175 +/- 19 (SD). The lowest rates, measured over three, five, and nine beats were 82 +/- 12, 87 +/- 12, and 93 +/- 12, respectively. At their lowest rates 109 infants had sinus bradycardia and 25 had junctional escape rhythms. Thirty-three infants showed changes in P wave configuration with or without pronounced variation in PR interval. Atrial premature beats were present in 19 infants but only one had more than 12 per hour. In a randomly selected subgroup of 71 infants sinus pauses were found in 51 (72%). Five (7%) had electrocardiographic patterns and rhythm disturbances that could not be differentiated from those previously described as complete sinuatrial exit block or sinus arrest, eight (11%) had patterns indistinguishable from 2:1 sinuatrial block, and 23 (32%) had pattern indistinguishable from sinuatrial Wenckebach block. This study shows that normal infants have variations in heart rate and rhythm hitherto considered to be abnormal.

Electrocardiography↗
PubMed1979

The Ninth Sir Hans Krebs Lecture. Compartmentation and communication in living systems. Ligand conduction: a general catalytic principle in chemical, osmotic and chemiosmotic reaction systems.

Chemical reactions, like osmotic reactions, are transport processes when looked at in detail. Chemical catalysis by enzymes or catalytic carriers, and osmotic catalysis by porters, may be conceived as occurring by specific ligand-conduction mechanisms. In chemiosmotic reaction systems, the pathways of specific ligand conduction are spatially orientated through anisotropic enzyme and catalytic carrier complexes in which the reactions of chemical group transfer occur as vectorial diffusion processes of group translocation down gradients of group potential that represent real spatially-directed fields of chemical force. Thus, it is easier to explain biochemistry in terms of transport than it is to explain transport in terms of biochemistry.

Animals↗
PubMed1978

Cytochrome c oxidase is not a proton pump.

We conclude that the reduction of O2 to 2 H2O by cytochrome c oxidase of rat liver mitochondria involves the translocation of 4-from cytochrome c at the outer surface of the cristae membrane per O2 reduced and protonated by 4 H+ ions that enter the reaction domain from the inner aqueous phase. This net electron-translocating function of cytochrome c oxidase plugged through the mitochondrial cristae membrane is not linked to a proton-pumping function, such as that proposed by Wikström [7,8].

Animals↗
PubMed1978

Cell wall-defective variants of pseudomonas-like (group Va) bacteria in Crohn's disease.

Several animal transmission studies have indicated that Crohn's disease may be caused by a filterable agent. Filtrates of homogenized tissues were prepared from 8 patients with Crohn's disease, 9 patients with chronic ulcerative colitis, and 20 control patients without inflammatory bowel disease. Conventional bacteriological cultures and hypertonic cultures for cell wall-defective bacterial variants were performed on the filtrates. Bacterial revertants (parent forms) of cell wall-defective variants were obtained from filtrates of various tissues including mesenteric lymph nodes of all patients with Crohn's disease. In no instance were revertants cultured from tissue filtrates of the other patients. The 11 revertants isolated from the 8 patients were identified as Pseudomonas-like bacteria, most closely identifiable with group Va.

Cell Wall↗