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Biomedical subjects

D J Ratcliffe

Publications and source records attributed to D J Ratcliffe.

12 recordsLinked to original sources
PubMed1985

Experimental myocardial ischemia. Differential injury of mitochondrial subpopulations.

Distinct populations of subsarcolemmal (SS) and inter-fibrillar (IF) rat cardiac mitochondria were studied following 15 and 30 minutes of warm and cold global ischemia. The respiratory control index, state 3, state 4, adenosine diphosphate-oxygen ratio, and specific enzyme activities of these mitochondrial populations were examined. The subsarcolemmar and IF mitochondria were both severely uncoupled and inhibited by warm ischemia. However, IF mitochondria had a higher RCI at each ischemic interval. In cold ischemia, IF mitochondria were not injured compared with control specimens. Subsarcolemmar mitochondria showed a trend towards a lower RCI that was statistically significant at 30 minutes with succinate as a substrate. These data implicate a differential injury of ischemia on the compartmentalized bioenergy metabolism of the myocardial cell.

Animals↗
PubMed1983

Endotoxin, cellular function, and nutrient blood flow.

To study the effects of endotoxemia on hepatic mitochondrial function and nutrient blood flow, rats were given intraperitoneal Escherichia coli endotoxin at a lethal dose for 90% mortality of group. Controls received only diluent. Five hours after the onset of endotoxemia, paired experimental and control animals had indocyanine green (ICG) clearance determined as the half-life (t1/2) at low (5 mg/kg) or high (15 mg/kg) doses. Low-dose ICG clearance represented hepatic nutrient blood flow; a Lineweaver-Burke plot of clearance rate v dose of administration provided extrapolation to an infinite dose and served as a sensitive indicator of hepatocellular function. Additional endotoxic rats were killed at five hours, liver and kidney mitochondria were isolated, and isolates were studied by the polarographic technique; the respiratory control index was determined as a sensitive indicator of efficient cellular oxygen metabolism with glutamate and succinate as substrates. Our data indicated that (1) uncoupling of the mitochondrial function is not identified during the early phase of endotoxemia, (2) reduced nutrient blood flow occurs during this early phase of endotoxemia, and (3) subsequent cellular abnormalities in endotoxemia may be secondary to ischemia and not direct cellular injury.

Animals↗
PubMed1983

Erythrocyte sodium-potassium-stimulated adenosine triphosphatase activity is not related to obesity.

Altered erythrocyte sodium potassium (Na,K)-stimulated adenosine triphosphatase (ATPase) activity has been cited as having pathophysiologic significance in morbidly obese man. Previous studies have failed to consider obese patients after weight loss and, therefore, did not clarify the role of ATPase deficiency as a cause or effect of the obese state. To define more completely the possible alteration of cellular thermogenesis in obesity, a study was made of three groups of people: (1) normal weight controls; (2) morbidly obese; and (3) formerly morbidly obese patients who had lost over 100 pounds after gastric bypass surgery. Erythrocyte ATPase activity was determined by use of an assay that coupled ATPase activity with NADH oxidation in the presence of excess pyruvate kinase, lactic dehydrogenase, and phosphoenolpyruvate. This coupled assay produced a continuous slope so that activity could be calculated from the initial, maximal, linear portion of the decay trace. Results did not demonstrate any statistically significant differences in Na,K-ATPase activity between groups by analysis of variance. A nonsignificant correlation of 0.086 was seen between obesity index and Na,K-ATPase activity. It is concluded that (1) erythrocyte Na,K-ATPase activity is similar in both normal and obese individuals, (2) erythrocyte Na,K-ATPase does not change with weight loss, and (3) therefore, disordered erythrocyte thermogenesis does not have a role in the development or maintenance of obesity.

Adult↗
PubMed1983

The effects of hydrogen-ion concentration on the respiratory efficiency of human liver mitochondria.

To examine the effects of hydrogen ion concentrations on the coupled respirations of isolated human liver mitochondria, eight patients underwent incidental liver biopsies during the conduct of abdominal surgery. Mitochondria were studied by the polarographic technique at pH of 5.5, 6.0, 6.5, 7.0, 7.5, and 8.0. Results indicated severe inhibition of nicotinamide adenine dinucleotide (NAD)-linked substrates but succinate oxidations were minimally affected. Sodium succinate was then studied as a possible substrate in the resuscitation of hemorrhagic shock. Rats were subjected to bleeding to an arterial blood pressure of 50 mm Hg for 3 hours or until 25 per cent of shed blood had to be reinfused to maintain blood pressure. Resuscitation consisted of reinfusion of all shed blood plus a volume of one of four crystalloid regimens: Ringers lactate; isotonic sodium succinate; hypertonic sodium chloride (190 mEq/l): or twice-normal, hypertonic sodium chloride (308 mEq/l). Results indicated that those rats resuscitated with sodium succinate did poorer than animals receiving alternate regimens. The failure of succinate to diffuse across the plasma membrane may explain these data. Additional studies with succinate or a chemical analogue seem warranted.

Animals↗
PubMed1982

Bioenergy metabolism of gastric mucosa during stress.

Previous studies have identified a cellular energy deficit in gastric mucosa after ischemia. We studied the processes of energy generation (mitochondrial function) and energy utilization (microsomal adenosine triphosphatase [ATPase] activity) in an experimental model of stress. Rabbits were divided into four groups: I, fed controls (n = 7); II, 24-hour fasted controls (n = 7); III, fasted, anesthetized, and cannulated controls (n = 7); and IV, fasted, anesthetized, cannulated, and bled rabbits. Bleeding consisted of 25 ml blood/kg into a reservoir for 60 minutes; the blood was then reinfused. Animals were killed 30 minutes after reinfusion; antral, corpus, and fundus mucosae were dissected; each region of mucosa was homogenized; and mitochondrial and microsomal fractions were isolated by differential centrifugation. No animals in group I or II had gastric ulcerations. Three of seven animals in group III and all group IV animals had corpus and fundus ulcers. No antral ulcers were seen in any group. The respiratory control index (RCI) of antral mitochondria was increased in groups II, III, and IV but was unchanged in all groups of corpus and fundus mitochondria. Studies of microsomal ATPase activity indicated increased activity of potassium-stimulated ATPase in the corpus mucosa. In the corpus mucosa, total ATPase activity was increased primarily as a consequence of increased potassium-stimulated ATPase. These data indicate that increased RCI is associated with gastric mucosal integrity in the antrum. Accelerated utilization of available adenosine triphosphate by corpus membrane ATPases may further compromise energy homeostasis during stress.

Adenosine Triphosphatases↗
PubMed1982

Hepatocellular function and nutrient blood flow in experimental peritonitis.

The pathophysiologic basis of organ failure and reduced oxygen consumption in peritoneal infection remains undefined. Plausible explanations include alteration of tissue nutrient blood flow and a primary cellular injury that impairs oxygen metabolism. To define this controversy, we created peritonitis in rats by cecal ligation and puncture. Controls had sham operation. Rats were sacrificed at 6 or 18 hours, liver mitochondria were isolated, and oxidative phosphorylation was studied polarographically. In additional animals indocyanine green (ICG) clearance was studied at low (5 mg/kg) or high (15 mg/kg) doses. The low-dose ICG clearance reflects total hepatic blood flow; a Lineweaver-Burk plot of clearance versus the dose permits extrapolation of clearance to an infinite dose as an indicator of cellular function. Mitochondria studied at 6 hours (n = 10) and 18 hours (n = 10) indicated no differences when compared to paired controls. ICG clearance was unchanged between peritonitis and control rats at 6 hours. However, at 18 hours peritonitis rats had a prolonged half-life of 2.49 +/- 0.31 minutes for the low-dose and 5.29 +/- 0.41 minutes for the high-dose compared to 1.65 +/- 0.07 and 4.34 +/- 0.10 minutes, respectively, for the controls. The Lineweaver-Burk plot of clearance versus dose resulted in peritonitis and control clearance rates intercepting each other at an extrapolated infinite dose. These data indicate that hepatocellular function measured by mitochondrial function and ICG clearance was unaltered. Low-dose ICG clearance indicated reduced total hepatic blood flow. The reduced oxygen consumption in peritonitis appears to have its genesis in altered nutrient blood flow.

Animals↗
PubMed1982

The effects of peritonitis on murine renal mitochondria.

To examine the coupled respiratory functions of murine kidney mitochondria, peritonitis was created in 29 male Sprague-Dawley rats; 29 rats were paired-controls. Peritonitis was created by cecal ligation and perforation. Experimental and control animals were sacrificed at two hours (N = 12), four hours (N = 8), and 6 hours (N = 9), mitochondria were isolated, and state 3, state 4, and Respiratory Control Indices (RCI) were determined. The state 3, state 4, and RCI were unchanged from control values by analysis of variance. From these data, we conclude that the defective oxygen consumptions and organ failure in sepsis is not due to a primary cellular insult to the kidney mitochondria.

Animals↗
PubMed1980

The effects of acidosis on canine hepatic and renal oxidative phosphorylation.

The intracellular effects of acidosis remain poorly defined. To examine the effects of acidosis on oxidative phosphorylation, liver biopsies and weight nephrectomies were performed on 10 adult German shepherd dogs. The mitochondria were isolated from each tissue and their respiratory activity was studied by the polarographic technique with the pH of the reaction media varied from 5.5 to 8.0. Glutamate and succinate substrates were employed. Results showed a dramatic reduction in the efficiency of oxygen utilization by mitochondria with glutamate as the reaction medium became more acidic. The efficiency of succinate oxidation was significantly (P less than 0.01) preserved. These findings were confirmed by both the respiratory control indices and by ADP:O ratios. Acidosis appears to result in severe inhibition of NAD-linked energy substrate oxidation.

Acidosis↗