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Biomedical subjects

R C Rose

Publications and source records attributed to R C Rose.

At least 109 records · Page 6Linked to original sources
PubMed1980

Heat injuries among recreational runners.

With the increasing popularity of jogging and competitive running, more people are participating in races, particularly during the warm months. In the Southeastern United States, the combination of high temperatures and high relative humidity appears to be responsible for many heat-associated injuries. We studied the training, racing, and selected personal characteristics of heat-injured and age- and sex-matched uninjured recreational runners at four races. The major differences between the two groups were that injured runners had not been running as long, ran fewer miles per week, ran fewer miles per training run, and were more likely to be caught up in the excitement of the event.

Athletic Injuries↗
PubMed1979

Absorption of 2-acetylaminofluorene in the guinea-pig colon.

Absorption of the known chemical carcinogen, 2-acetylaminofluorene has been measured in the colon of guinea pigs. Unidirectional influx across the luminal cell membrane was determined in vitro, and transmural absorption across colonic mucosa was evaluated in vivo. The kinetics of unidirectional influx into colon in vitro do not indicate that absorption proceeds by simple diffusion. The observed saturable uptake is indicative of binding of 2-acetylaminofluorene to a cellular component. With 2-acetylaminofluorene present in the lumen in vivo at an initial concentration of 3.5 microM, the rate of absorption decreases over a 20 min period, which also indicates some form of specific interaction between 2-acetylaminofluorene and the intestinal mucosa. We have evaluated the hypothesis that surfactants and a bile salt act as cocarcinogens by increasing the rate of intestinal absorption of 2-acetylaminofluorene. The results lend no support to this possibility.

2-Acetylaminofluorene↗
PubMed1979

Erythema and conjunctivitis. Outbreak caused by inadvertent exposure to ultraviolet light.

During August to November 1977, fifty-eight episodes of erythema or conjunctivitis or both occurred among nursing-service employees at a large state hospital. Epidemiologic investigation implicated an ultraviolet-light-producing germicidal bulb in a nursing station's desk lamp as the causative agent. Removal of the lamp from the nursing station controlled the outbreak. Analysis of the spectral irradiance from the bulb suggested that the National Institute of Occupational Safety and Health exposure standards were exceeded in five to 20 minutes, depending on the individual's distance from the lamp.

Antisepsis↗
PubMed1978

Folic acid transport by mammalian small intestine.

The unidirectional influx of folic acid across the mucosal border of hamster duodenum and rat jejunum was determined. Influx follows saturation kinetics, is sodium-dependent, and is inhibited by methotrexate and is sodium-dependent, and is inhbited by methotrexate and folinic acid in the mucosal bathing solution. In hamster duodenum, the maximal influx is 1.2 nmol/(cm2.h), and the folic acid concentration required to give a half maximal influx (Km) is 7.2 micron.. At mucosal folic acid concentration of 1.5 micron, influx is reduced at least 65% by removal of sodium from the bathing solution. The influx process is significantly inhibited by cyanide and 2,4-dinitrophenol. The possibility was evaluated that the acidic microclimate at the brush border regulates the rate of folic acid transport and that inhibition of transmural transport by sodium-free media, ouabain, and methotrexate is brought about indirectly by an increase in pH of the microclimate. The data favor the alternative concept of a sodium-dependent carrier mechanism for entry of folic acid into the cells. The information presented is consistent with active transport of folic acid by a sodium-gradient mechanism, but additional information will be necessary to substantiate such a model.

Animals↗
PubMed1978

Intestinal ascorbic acid transport following diets of high or low ascorbic acid content.

Active transport of ascorbic acid in ileum is mediated by a carrier mechanism at the brush border membrane. This mechanism may show compensatory changes in activity in response to alterations of dietary ascorbic acid content. The unidirectional influx of ascorbic acid across the brush border into epithelial cells of guinea pig ileum was determined in vitro. Influx was significantly reduced in scorbutic animals and following 14 or 28 days of high doses (5 or 25 times normal) of ascorbic acid. The transport rate was reduced by intramuscular administration of ascorbic acid, suggesting that the transport mechanism may respond to circulating levels of the vitamin.

Animals↗
PubMed1977

Choline influx across the brush border of guinea pig jejunum.

Choline uptake across the mucosal border of guinea pig jejunum was measured to determine the characteristics of this step in intestinal absorption. Unidirectional influx of [14C]choline appears to proceed primarily by a saturable, carrier-mediated process at low mucosal choline concentrations; at high concentrations (greater than 4 mM) the influx rate is approximately linearly related to the mucosal choline concentration, suggesting that absorption by passive diffusion predominates. Influx was only minimally reduced by elimination of Na+ from the mucosal test solution or by reduction of the intracellular Na+ concentration. Preincubation of tissue samples with metabolic inhibitors or with ouabain did not markedly reduce influx. These results are consistent with a model of choline transport across the brush border membrane by a carrier-mediated mechanism which is similar to that involved in fructose absorption but different from the Na+-dependent mechanism which participates in active transport of sugars and amino acids. At low lumenal choline concentrations, influx into colonic mucosa is slower than in jejunum and appears to be attributed solely to simple diffusion.

Animals↗
PubMed1977

Electrical potential profile in rabbit ileum: role of rheogenic Na transport.

The electrical potential profile of rabbit ileum was investigated in vitro with the microelectrode technique. The transmural electrical potential difference (PD), designated psims, was immediately reduced by 60% upon cooling the tissue from 37 to 7 degrees C; the PD across the mucosal membrane (transmucosal PD, psimc) was simultaneously reduced by 37%. These electrical changes could not be attributed to alternations in either transmembrane ion concentration gradients or total tissue conductance. The psimc and psims may have substantial values even after the concentration gradients of Na and K across the cell membane are eliminated, provided that active transport mechanisms are still operative. Conversely, in the presence of approximately normal transmembrane ion concentration gradients, but when active transport mechanisms have been inhibited. psimc is reduced by 45% and psims is zero. These observations are consistent with a model of electrolyte transport in which psims and the normal transmembrane cation concentration gradients are established by rheogenic active transport of Na out of the cell. The psimc is generated both by rheogenic active Na transport and by cation concentration gradients which exist across the cell membrane. The Koefoed-Johnsen and Ussing model (Acta Physiol. Scand., 1958, vol. 42, p. 298) of electrolyte transport by epithelial cells does not adequately describe the electrical properties of ileum.

Animals↗
PubMed1977

Ascorbic acid flux across mucosal border of guinea pig and human ileum.

The unidirectional influx of L-[14C]ascorbic acid (vitamin C) across the mucosal border of guinea pig and human ileum was determined. Influx follows saturation kinetics, indicating that a carrier mechanism is operative. The maximal influx in guinea pig ileum bathed in Ringer is 140 nmol/cm2-h and the ascorbic acid concentration greater than 6 mM , or when the tissue is bathed in Na-free media, influx is approximately linearly related to the ascorbic acid concentration, and absorption by simple diffusion may predominate. With mucosal ascorbic acid concentration of 0.28 mM, influx is reduced by at least 70% when Na-free media is used; however, influx is not dependent on the intracellular Na concentration. The brush border mechanism appears to be stereospecific and not closely coupled to cellular metabolism. A model of transport is favored that features a carrier-mediated transport mechanism for simultaneous entry of ascorbic acid and Na across the brush border. This model is similar in nature to, but functionally distinct from, the sodium-gradient mechanism postulated to effect sugar and amino acid transport in mammalian ileal mucosa.

Animals↗
PubMed1977

Characteristics of inhibition of pancreatic secretion by isoproterenol.

The effect of isoproterenol on pancreatic secretion stimulated by the octapeptide of cholecystokinin (OP-CCK) was studied in dogs with gastric and pancreatic fistulas. Special precautions were taken to prevent entry of gastric acid into the duodenum and reflux of duodenal content into the stomach. OP-CCK increased volume and the outputs of bicarbonate and protein from the pancreas. Isoproterenol inhibited these pancreatic responses to OP-CCK, and the degree of inhibition was dose related. Propranolol blocked the inhibitory action of isoproterenol completely. Analysis of data by Michaelis-Menten kinetics revealed that there was competitive inhibition of protein output with noncompetitive inhibition of bicarbonate output. The experiments show that isoproterenol inhibits OP-CCK--stimulated pancreatic secretion by a beta-adrenergic mechanism. The kinetic analysis suggests that the intimate mechanisms involved in inhibition of protein and bicarbonate output by isoproterenol are different.

Animals↗
PubMed1976

Electrolyte transport by gallbladders of rabbit and guinea pig: effect of amphotericin B and evidence of rheogenic Na transport.

Ion transport and electrical properties of rabbit and guinea pig gallbladders were investigated to gain further information about the active transport mechanism that mediates fluid absorption. The intracellular and transepithelial electrical potentials were measured simultaneously using the microelectrode technique. Exposure of the mucosal surface to Amphotericin B resulted in the prompt development of a serosa-positive electrical potential difference (PD) which could not be attributed to an alteration in ion diffusion potentials across either the cell membrane or across the tight junction. Because the Amphotericin B-induced PD was immediately dependent on warm temperatures and O2, and was independent of NA and K concentration gradients across the cell membrane, it is suggested that active ion transport is directly responsible for the PD. Since the PD was abolished in the absence of Na in the bathing solutions, a rheogenic Na pump is postulated; this pump also appears to be operative in tissues not exposed to Amphotericin B. The specific tissue properties altered by Amphotericin B to produce a serosa-positive PD remain incompletely defined. The results of the present study indicate that ion transport by rabbit gallbladder in vitro is a consequence of a rheogenic active Na transport mechanism at the basolateral membranes which, in conjunction with a coupled NaC1 influx process at the mucosal border, ultimately results in absorption of NaC1 and water.

Amphotericin B↗
PubMed1976

Abnormalities in gallbladder morphology and function in patients with cholelithiasis.

Thirty-seven symptomatic cholelithiasis patients who had cholecystectomy were studied to determine the relationships between clinical manifestations, histologic findings and gallbladder absorptive capability. A clinical score was calculated from clinical data which we thought might be predictive of abnormal gallbladder histology. Histologic parameters indicative of gallbladder disease were used to calculate a histologic score. Shortcircuit current measurements, which reflect gallbladder sodium absorption,were used to assess absorptive function. Patients with very high clinical scores, indicative of pronounced clinical score was not predictive of histologic findings or absorptive function of the gallbladder is directly related to the degree of histologic abnormality, and that absorptive capability is not an all-or-none phenomenon. The data also show that visualization on oral cholecystography is an unreliable measure of gallbladder absorptive capability.

Cholecystography↗
PubMed1976

Changes in hepatic bile secretion following cholecystectomy.

The volume and compositon of hepatic bile was studied in anesthetized dogs before and approximately 18 weeks after cholecystectomy. Dogs had common duct cannulation, cystic duct ligation, and temporary occlusion of the pylorus. An intravenous infusion of sodium taurocholate, 9 muEq per minute, was given throughout the experiment. Bile volume, electrolyte composition, bile salt output, and 14C-mannitol clearance were determined during infusion of sodium taurocholate alone and after addition of secretin, 4 U. per kilogram per hour, to the infusion. Cholecystectomy then was done and the same experiment was repeated 18 weeks later. Cholecystectomy significantly increased bile volume, sodium and chloride output, and 14C-mannitol clearance both in response to taurocholate alone and to taurocholate plus secretin. Bile salt output and bicarbonate output were unchanged. The study shows that cholecystectomy significantly alters the volume and composition of hepatic bile. The data indicate that cholecystectomy does not affect ductular function or hepatic secretion of bile salts but that canalicular function is altered significantly.

Animals↗