Respiratory syncytial virus pneumonia in a human immunodeficiency virus-infected man.
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Adult↗
Biomedical subjects
R C Rose
Publications and source records attributed to R C Rose.
Response to surgeon-specific infection rates.
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Humans↗
Clinically significant central venous catheter infections in a community hospital: association with type of dressing.
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Bandages↗
Expression in Escherichia coli of seven DNA fragments comprising the complete L1 and L2 open reading frames of human papillomavirus type 6b and localization of the 'common antigen' region.
Molecular cloning was used to express human papillomavirus type 6b (HPV-6b) antigens in Escherichia coli. Seven genomic DNA fragments of HPV-6b which together comprise the complete L1 and L2 open reading frames, known to code for capsid proteins, were cloned and expressed in E. coli as both beta-galactosidase and TrpE fusion proteins. Western blots of HPV-6b beta-galactosidase fusion proteins using 'genus-specific' antisera produced by immunization of rabbits with disrupted bovine papillomavirus type 1 (BPV-1) showed that polypeptides encoded by two DNA fragments from the mid portion of L1 of HPV-6b were cross-reactive. Only one of these two polypeptides reacted with antisera raised against disrupted HPV-1, directly demonstrating that this polypeptide contains the papillomavirus 'common antigen'. The cross-reactive region was confirmed by reversing antigen and antibody. Polyclonal antisera were raised against the seven HPV-6b beta-galactosidase fusion proteins and tested against BPV-1 virion proteins on Western blots. Only antiserum against the mid portion of L1 of HPV-6b reacted with the BPV-1 major capsid protein. HPV-6b fusion proteins were also used to test human sera for antibodies reactive in Western blots. Serum samples from 38 patients with documented HPV-6 infections and from 22 presumably uninfected controls were tested. Antibodies were not detected in any of the sera to any of the seven fusion proteins. HPV-6b beta-galactosidase fusion proteins are antigenic and can be used on Western blots to localize immunologically reactive sub-regions of proteins by reacting protein fragments with antisera from immunized animals. However, alternative methods will be required to detect anti-HPV antibodies in human sera.
Adult↗
Transport and metabolism of ascorbic acid in human placenta.
The role of human placenta in cellular transport and metabolism of the potentially toxic oxidized form and the useful reduced form of ascorbic acid was examined in surviving tissue fragments in vitro. At the end of a 60-min incubation with the 14C label nominally present in the reduced form, a tissue-to-medium ratio in excess of unity was reached. The importance of evaluating uptake of the ascorbic acid metabolites is evident from a careful assay of 14C label present in the bathing media. Significant spontaneous oxidation occurs, which is slowed or reversed to a limited extent by the presence of placental tissue. Uptake of the oxidized substrate, dehydro-L-ascorbic acid, proceeds much more rapidly than uptake of ascorbic acid. At the end of a 15-min incubation, most of the substrate taken up was in the reduced form. From an additional evaluation of 14C label in the bath it is calculated that 25% of ascorbic acid formed by the tissue is released within 15 min. The cellular uptake mechanism for dehydro-L-ascorbic acid is not shared by glucose and is not dependent on the presence of Na+ but is dependent on intact cellular metabolism. The finding of avid cellular uptake and reduction of the oxidized form of ascorbic acid supports the concept that the placenta helps to clear the toxic molecule from the maternal circulation, metabolizes it, and delivers the useful reduced form to the fetus.
2,3-Diketogulonic Acid↗
Renal metabolism of the oxidized form of ascorbic acid (dehydro-L-ascorbic acid).
We evaluated whether specific transport and metabolic properties exist in rat and guinea pig kidney for handling the immediate oxidative product of ascorbic acid, dehydro-L-ascorbic acid. Isolated tubules were used to measure uptake of 10 microM [14C]-dehydro-L-ascorbic acid over an 8-min incubation period. Uptake did not show dependence on the bathing media electrolyte composition but was inhibited to some extent by glucose. In tubules of both animal species the majority of 14C label present in the tissue extract was in the reduced form. No degredative enzymatic effect on dehydro-L-ascorbic acid is evident. Thirty-six percent of the [14C]dehydro-L-ascorbic acid reduced by the tubules was released during an 8-min incubation. Recently formed ascorbic acid is not substantially bound to cellular components. A factor necessary for dehydro-L-ascorbic acid reduction in renal cortex was found primarily in the 55-70% ammonium sulfate fraction. It is retained by mol wt 12,000 dialysis tubing, is heat labile, pH sensitive, inhibited by thiol reagents, and is most active in the presence of NADPH and glutathione. It has a molecular weight between that of blue dextran and cytochrome c as indicated by gel chromatography. We suggest that a cytosolic enzyme functions in reduction of dehydro-L-ascorbic acid and thereby is important in maintaining the redox state of ascorbic acid derived from the glomerular filtrate or from peritubular fluid.
Animals↗
Regeneration of ascorbic acid by rat colon.
Plants and animals alike use ascorbic acid in a variety of reactions that result in net generation of dehydro-L-ascorbic acid. The ability to reduce dehydro-L-ascorbic acid back to ascorbic acid would conserve "total ascorbate" and would help to maintain the toxic oxidized form of the molecule at a low level. This study evaluated the rate of dehydro-L-ascorbic acid reduction either by following the rate of NADPH consumption or by analysis of the amount of 14C-labeled dehydro-L-ascorbic acid converted to ascorbic acid. A large percentage of the NADPH consumed by a semipurified preparation of rat colonic mucosa in vitro was dependent on the presence of dehydro-L-ascorbic acid. The tissue factor active in regenerating ascorbic acid is intermediate in size between cytochrome c and blue dextran. The present results indicate that the mucosa reduced dehydro-L-ascorbic acid by a cytosolic enzyme that uses NADPH as a hydrogen donor. Subsequent to precipitation by ammonium sulfate, the 55-70% fraction contains most of the reductase activity while consisting of only 17% of the cellular soluble protein.
Animals↗
Transport of ascorbic acid and other water-soluble vitamins.
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Animals↗
Intestinal transport and metabolism of oxidized ascorbic acid (dehydroascorbic acid).
The transport and metabolic properties of dehydroascorbic acid have been evaluated in the small intestine of one ascorbic acid-dependent animal species (guinea pig) and one ascorbic acid-synthesizing animal species (rat). Loops of guinea pig jejunum in vitro brought about net transepithelial absorption of L-[14C]dehydroascorbic acid with most of the absorbed substrate appearing in the reduced form (ascorbic acid). Saturation of brush-border transport occurs at a lower concentration than saturation of the enzymatic reduction. Rat intestine did not bring about net transepithelial transport. The intestines of both guinea pigs and rats took up substantial dehydroascorbic acid from the serosal bathing solution, with the majority appearing in the mucosa as ascorbic acid. It is proposed that in guinea pig intestinal mucosa, dehydroascorbic acid reductase has a nutritional role in extracting the vitamin from chyme and reducing it for subsequent use in the body. The intestines of both guinea pig and rat appear to take up dehydroascorbic acid across the basolateral surface and reduce it, thus maintaining a substantial endogenous level of ascorbic acid in the mucosa. The transport and metabolic properties described might play an important role as a protective antioxidant mechanism in intestinal mucosa.
Animals↗
Solubility properties of reduced and oxidized ascorbate as determinants of membrane permeation.
The oil/water distribution coefficients of ascorbic acid and dehydro-L-ascorbic acid have been determined and compared with values for mannitol and lauric acid. In general, the relative degrees of hydrophobicity of the compounds evaluated are lauric acid much greater than mannitol approximately equal to dehydro-L-ascorbic acid greater than ascorbic acid. These findings and recent reports from transport studies do not support the concept that dehydro-L-ascorbic acid is very hydrophobic and crosses cell membranes rapidly by simple diffusion.
Ascorbic Acid↗
Fever in hospitalized patients. With special reference to the medical service.
Fever (oral temperature of 38 degrees C or more on two or more consecutive days) during the hospital stay of 4,065 patients admitted to Grady Memorial Hospital during an 11-week period was studied. At least one episode of fever occurred in 1,194 patients (29 percent). Rates of fever were highest on medical and surgical services. Review of 341 episodes of fever in 302 patients on the medical service identified a single potential cause in 56 percent. Multiple factors were present in 26 percent, and no potential causes were found in 18 percent. Of 390 factors identified, 44 percent were community-acquired infections, 9 percent were nosocomial infections, 20 percent possibly involved infection, and 26 percent were noninfectious processes. Fever is a frequent finding in hospitalized patients. Both infectious and noninfectious processes play important roles. Determining the cause of fever is complicated by the multiplicity of possible causes.
Cross Infection↗
Metabolism and transport of dehydroascorbic acid in erythrocytes of "spontaneous diabetic BB/W" Wistar rats.
Rates of uptake and reduction of dehydroascorbic acid in erythrocytes of "Spontaneous diabetic BB/W" and control Wistar rats were determined. Lysed cells reduced 14C-dehydroascorbic acid more rapidly than intact cells did, suggesting that membrane transport is a rate-limiting step. Diabetic rats had lower plasma levels of ascorbic acid but more rapid reduction of dehydroascorbic acid than control animals. The results indicate more rapid transport of dehydroascorbic acid into erythrocytes of prediabetic "BB/W" rats than Wistar rats.
Animals↗
Dehydroascorbic acid and cell membranes: possible disruptive effects.
Exposure of cellular membranes to dehydroascorbic acid can result in a loss of membrane integrity. Renal brush border or basolateral membrane vesicles pre-incubated with dehydroascorbic acid demonstrate a decrease in initial transport rates of D-glucose and a loss of intravesicular volume. The activity of brush border membrane specific leucine aminopeptidase is increased in vesiculated membrane preparations following exposure of the vesicles to either dehydroascorbic acid or Triton X-100. Erythrocytes in isotonic buffer with dehydroascorbic acid lose membrane integrity as demonstrated by a release of hemoglobin.
Animals↗
The effect of diets high in fat and/or fiber on colonic absorption of DMH in the rat.
The possibility that long-term feeding of diets high in fat or fiber could alter the colonic mucosa and subsequent colonic absorption of 1,2-dimethylhydrazine (DMH) in situ was examined in the rat model. Male Sprague-Dawley rats were fed one of four experimental diets for six weeks prior to studies of DMH absorption and bile acid excretion; dietary treatments consisted of two levels of fat (12 and 47% of calories from corn oil) fed at each of two levels of fiber (plus or minus 15% wheat bran). Two sets of DMH absorption studies (Studies 1 and 2) were performed; the first used a 10- and the second a 20-minute test period. In Study 1, DMH absorption was greater in those animals that had been fed the high level of corn oil when additional fiber was not present in the diet. When a longer absorption period was used (Study 2), this effect of diet on DMH absorption was not apparent. The level of fiber, not the fat intake, altered bile acid excretion. Bile acid concentration (mg/g dry wt) decreased with added fiber, whereas total bile acid excretion (mg/day) increased. These results indicate that high levels of dietary fat may result in small increases in DMH absorption which are unrelated to changes in bile acid concentration.
Animals↗
Renal transport and metabolism of nicotinic acid.
Renal metabolism and brush-border transport of nicotinic acid were studied in renal cortical slices and brush-border membrane vesicles exposed to a physiological concentration of vitamin (2.2-3.5 microM). Vesicle transport of [3H]nicotinic acid was found to be Na+ dependent and concentrative. The presence of a Na+ gradient resulted in a fivefold increase in the rate of nicotinic acid uptake over that observed with mannitol and caused a transient nicotinic acid accumulation two- to fourfold above the equilibrium value. The effects of membrane potential, pH, and elimination of Na+-H+ exchange were also studied. Cortical slices and isolated tubules exposed to 2.2 microM [14C]nicotinic acid took up vitamin and rapidly metabolized most of it to intermediates in the Preiss-Handler (J. Biol. Chem. 233: 488-493, 1958) pathway for NAD biosynthesis; little free nicotinic acid was detectable intracellularly. The replacement of Na+ with Li+ in the bathing medium reduced total accumulation of 14C label primarily as a result of reduced nicotinic acid uptake. Cortical tissue concentrated free nicotinic acid only when the involved metabolic pathways were saturated by levels of nicotinic acid far in excess of what occurs in vivo.
Animals↗
Absorption of pantothenic acid in rat and chick intestine.
Pantothenic acid absorption was evaluated in the intestine of rat and chicken to reevaluate the concept that this nutrient crosses the mucosa by simple diffusion. Unidirectional influx of [3H]pantothenic acid (0.9 microM) across the brush-border membrane of rat jejunum in vitro demonstrates sodium dependence and saturation kinetics. Net transepithelial transport (absorption) of pantothenic acid takes place in everted sacs of jejunum against an electrochemical potential gradient. This accumulation does not occur in tissue exposed to metabolic inhibitors. Also, pantothenic acid accumulates in the transport cells of both rat and chicken intestine against a 9- to 10-fold concentration gradient. Recently absorbed pantothenic acid is freely diffusible from isolated chicken enterocytes. No metabolic conversion of pantothenic acid was detected during absorption in the intestine of either species under conditions in vitro or in vivo. The present results indicate that pantothenic acid present at low concentrations is absorbed in the intestine by a specific transport mechanism; the process is best described as sodium-dependent, secondary active transport.
Absorption↗
Dehydroascorbic acid and ascorbic acid transport systems in the guinea pig ileum.
The transport properties of dehydroascorbic acid and ascorbic acid in membrane vesicle preparations of guinea pig ileum were evaluated. Na-dependent transport of ascorbic acid in the brush-border membrane was confirmed, and an Na-independent mechanism was found in the basolateral membrane. The electrically neutral oxidized form of vitamin C is transported by an Na-independent mechanism at both cell surfaces. Transport of each substrate is saturable and exhibits cis-inhibition and trans-stimulation in the presence of structural analogues. Additional studies on ascorbate metabolism will be necessary to support a comprehensive model of intestinal handling of vitamin C.
Animals↗
Ascorbic acid transport in mammalian kidney.
Ascorbic acid is known to circulate free in the plasma of several species and is therefore filtered in the kidney; reabsorption subsequently takes place and prevents urinary loss. However, no specific mechanism of renal ascorbic acid transport has previously been presented. In the present study, rat and guinea pig kidney were incubated as slices or as isolated tubules in vitro in the presence of low concentrations of [14C]ascorbic acid. The kidneys of both species handle ascorbic acid similarly. Ascorbic acid accumulates in the renal tissue to a concentration three to four times that present in the bathing media. Recently absorbed ascorbic acid diffuses freely from the kidney and is predominantly nonmetabolized during absorption. Uptake is reduced following replacement of bathing solution sodium by lithium or cesium, or when incubation is performed in the presence of metabolic inhibitors or at low temperatures. The results indicate that ascorbic acid is reabsorbed in the kidney by a sodium-dependent active transport mechanism that operates by concentrating ascorbic acid in the cellular fluid. Renal slices and tubules both appear to transport ascorbic acid and galactose across the brush-border membrane; this indicates that the tubular lumens in these preparations are not collapsed or sealed off.
Animals↗