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Biomedical subjects

K Cooper

Publications and source records attributed to K Cooper.

At least 235 records · Page 13Linked to original sources
PubMed1986

Postischemic ATP-MgCl2 provides precursors for resynthesis of cellular ATP in rats.

Postischemic administration of ATP-MgCl2 is known to enhance recovery of renal function and accelerate the restitution of cellular ATP levels. To differentiate between a direct and indirect effect of the exogenous nucleotide, rats were subjected to 45 min of bilateral renal ischemia and were infused with either ATP-MgCl2, AMP-MgCl2, or normal saline. The immediate recovery of the cellular ATP was similar in all three groups of animals, whereas the subsequent recovery was accelerated by the infusion of either nucleotide. Since ATP-MgCl2 and AMP-MgCl2 produced similar results, this study provides evidence that exogenous ATP may act by providing precursors for the resynthesis of the cellular adenine nucleotide pool rather than being a direct source of energy.

Adenosine Triphosphate↗
PubMed1984

Oxalate absorption and postprandial urine supersaturation in an experimental human model of absorptive hypercalciuria.

The effect of 1.25-dihydroxyvitamin D [1,25-(OH)2D] on dietary oxalate absorption and postprandial urine supersaturation with calcium oxalate was determined in 11 normal subjects. 1,25-(OH)2D increased the urinary excretion of orally administered [14C]oxalate in the 8 h period after a liquid meal containing 1.875 mmol of calcium and 0.83 mmol of oxalate (P less than 0.01), and during a 48 h period when the subjects ingested a diet containing 25 mmol of calcium and 3.3 mmol of oxalate/day (P less than 0.01); however, 1,25-(OH)2D administration had no effect on [14C]oxalate excretion when calcium was removed from the liquid meal. 1.25-(OH)2D increased 24 h urinary oxalate excretion from 28.7 +/- 2.1 mmol/mol of creatinine to 36.8 +/- 2.6 mmol/mol of creatinine (P less than 0.05) on the 10 mmol/day calcium diet and from 26.4 +/- 2.9 to 33.2 +/- 2.2 mmol/mol of creatinine (P less than 0.1) on the 25 mmol/day calcium diet. A linear correlation (r = 0.72) was found between plasma 1,25-(OH)2D levels and urinary [14C]oxalate excretion after the liquid meal. 1,25-(OH)2D administration produced postprandial supersaturation of urine with calcium oxalate and calcium oxalate crystalluria. These studies suggest that 1,25-(OH)2D increases oxalate absorption (and urinary excretion) by increasing calcium absorption, which results in less binding of calcium to oxalate in the intestine; therefore more oxalate is available for absorption. The combined effect of increased calcium and oxalate absorption results in postprandial supersaturation of urine with calcium oxalate, with resultant crystalluria.

Adult↗
PubMed1984

Induction of airway collapse with subatmospheric pressure in awake patients with sleep apnea.

To determine whether the pharyngeal airway is abnormal in awake patients with obstructive sleep apnea (OSA), we measured the ability of the pharyngeal airway to resist collapse from subatmospheric pressure applied to the nose in awake subjects, 12 with OSA and 12 controls. Subatmospheric pressure was applied to subjects placed in the supine position through a tightly fitting face mask. We measured airflow at the mask as well as mask, pharyngeal, and esophageal pressures. Ten patients developed airway obstruction when subatmospheric pressures between 17 and 40 cmH2O were applied. Obstruction did not occur in two patients with the least OSA. Obstruction did not occur in 10 controls; one obese control subject developed partial airway obstruction when -52 cmH2O was applied as did another with -41 cmH2O. We conclude that patients with significant OSA have an abnormal airway while they are awake and that application of subatmospheric pressure may be a useful screening test to detect OSA.

Adult↗
PubMed1984

An experimental human model of 1,25-dihydroxyvitamin D-mediated hypercalciuria.

An increase in fasting calcium excretion occurs in hypercalciuric patients and has been interpreted by many investigators as evidence for a primary renal tubular leak of calcium. In a recent series of 50 patients with absorptive hypercalciuria, we found a mean increase in fasting fractional calcium excretion (calcium clearance) and provided data suggesting that this leak of calcium was secondary to intestinal hyperabsorption of calcium and suppression of parathyroid secretion. To examine this question, a model of 1,25-dihydroxyvitamin D [1,25-(OH)2D]-mediated hypercalciuria was created by administering a large dose of 1,25-(OH)2D to normal subjects. In addition to the expected features of absorptive hypercalciuria during 1,25-(OH)2D administration, the subjects had an increase in fasting calcium excretion and a marked increase in calcium excretion during a restricted calcium diet, points that might be interpreted as favoring a resorptive and/or renal component to the net hypercalciuria. However, total hydroxyproline excretion remained unchanged (18.0 vs. 19.0 mg/g creatinine), and the increase in fasting calcium excretion was found to reflect an increase in calcium clearance; the latter was inversely correlated with parathyroid function, as determined by fasting measurements of nephrogenous cAMP excretion (r = -0.77; P less than 0.01). We conclude that measurements of calcium excretion in the fasting state or on a restricted calcium diet do not represent valid criteria for differential diagnosis of the hypercalciurias.

Adult↗
PubMed1981

In vitro activity of 2-alkyl-3-hydroxy-1,4-naphthoquinones against Theileria parva.

A variety of naphthoquinones have veen prepared and evaluated in vitro against the causative agent of the cattle disease East Coast Fever-Theileria parva infection. It is concluded from structure-activity studies that a 2-hydroxyl moiety es essential for high activity. The most active compounds tested were 2-hydroxy-3-alkyl-1,4-naphthoquinones in which the alkyl moiety was cyclohexyl, cyclohexylcyclohexyl, tridecyl, or tetradecyl.

Animals↗
PubMed1980

Aerobics.

Explore the source record for details and available documents.

Cardiovascular Diseases↗
PubMed1978

Effect of modified sham feeding on jejunal transport and pancreatic and biliary secretion in man.

Because previous evidence suggested that intestinal secretion was under parasympathetic control, we investigated the effect of modified sham feeding on the intestinal transport of water and electrolytes by jejunal perfusion using a triple lumen tube. By measuring the concentration of amylase, protein, and bile acids entering the intestinal test segment, we were also able to obtain data on the influence of sham feeding on pancreatic and biliary secretion. Gastric contents were aspirated throughout the experiment. Although we observed a clear-cut cephalic phase of gastric acid secretion, sham feeding had no effect on jejunal transport of water and electrolytes or on the rate at which bile acids, protein, or amylase were secreted into the duodenum.

Adult↗