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Biomedical subjects

H C Yang

Publications and source records attributed to H C Yang.

At least 91 records · Page 5Linked to original sources
PubMed1990

Differential effects of sodium on hydrogen- and glucose-dependent growth of the acetogenic bacterium Acetogenium kivui.

Acetogenium kivui could not be revived or maintained in a sodium-deficient medium (0.2 mM sodium) under H2-dependent conditions, and neither lithium nor potassium replaced the sodium requirement of H2-cultivated cells. Conversely, the revival and maintenance of glucose-cultivated cells did not display a dependency on supplemental sodium. In the absence of growth, formate became a major end product in both sodium-deficient and metabolically impaired H2-grown cultures of A. kivui. Harmaline, a putative inhibitor of Na+/H+ antiporters, uncoupled acetogenesis from H2-dependent growth but was less effective when growth was at the expense of glucose. Significantly, carbon monoxide (CO) stimulated H2-dependent growth of A. kivui but inhibited glucose-dependent growth. Collectively, these findings demonstrate that sodium plays a critical role in the H2-dependent bioenergetics of A. kivui and indicate that autotrophic and heterotrophic cells may utilize dissimilar mechanisms of energy conservation. In contrast to the growth of A. kivui, supplemental sodium was not required for the glucose-, H2-, and CO-dependent growth of Clostridium thermoaceticum.

Acetates↗
PubMed1990

c-fos regulation in untransformed as compared to transformed Balb/c 3T3 fibroblasts.

The regulation of c-fos expression was studied in the untransformed A31 Balb/c 3T3 mouse fibroblast cell line and in the derivative benzo(a)pyrene (BPA31), dimethylbenz(a)anthracene (DA31) and the Kirsten sarcoma virus (KA31) transformed cell lines. The peak induced c-fos RNA levels varied by about 20-fold among the cell lines. Differences in the peak level of c-fos RNA were due primarily to differences in the de novo transcriptional rate rather than in the stability of the message. Superinduction of 6-12x occurred after combined cycloheximide and phorbol ester treatment in the 4 cell lines. Superinduction of 20x in the untransformed A31 cells but only 1-3x in the transformed cells occurred when cycloheximidine and 10% serum were used. Superinduction of 5x in the A31 cells and of 1-2x in the transformed cells was found using cycloheximide and A23187. The data suggest the possibility that a labile protein which degrades the c-fos RNA is stabilized or increased in the transformed cells.

Animals↗
PubMed1990

Experience with the double lumen Silastic catheter for hemoaccess.

Transvenous access for acute hemodialysis has advanced recently with the introduction of a double lumen Silastic (silicone rubber), Dacron-cuffed (polyester) catheter (Quinton PermCath), which has a better patient acceptance than the stiff Teflon (polytetrafluoroethylene) catheters. We present our experience with 53 PermCath catheters placed in 49 patients (eight to 80 years old). Twenty-two catheters were used for initiation of dialysis, 17 as a bridge to permanent hemoaccess, two as a bridge to peritoneal dialysis and 12 for chronic hemoaccess. We have achieved better success with insertion of catheters through the jugular system (external in 22 instances and internal in 30) by cutdown with fluoroscopic positioning of the catheter tip at the second to third intercostal space. Arterial port alignment was toward the center of the vena cava to reduce sucking against the caval wall during dialysis. No catheter failed to function with this positioning technique. Average catheter use was 84 days with a range of one to 573 days. Catheter thrombosis occurred 40 times in ten patients and was treated successfully in all with the infusion of streptokinase or urokinase. Four patients received chronic warfarin for repeated clotting. Four patients had catheter sepsis that resolved with removal of the catheter and administration of antibiotics. We conclude that the PermCath is an improved means for hemoaccess with a low complication rate. Our key to successful functioning of the PermCath is careful fluoroscopic positioning of the catheter tip.

Catheterization, Central Venous↗
PubMed1990

Evaluation of pancreatic allograft circulation using color Doppler ultrasonography.

In conclusion, color flow Doppler ultrasonography is a safe, noninvasive method to study perfusion in the pancreatic allograft. In trained hands, reproducibly quantitative measurements can be made of the circulation in the transplanted pancreatic allograft. With further experience, it is our hope that spectral analysis will elucidate rejection as it has for us with kidney transplants. Because the technique is noninvasive, it has a high degree of patient acceptance.

Humans↗
PubMed1989

Altered kinase C function in transformed BALB/c3T3 cells.

Comparative studies of kinase C function were performed in an untransformed (A31) and the benzo[a]pyrene (BPA31), dimethylbenz[a]anthracene (DA31), and Kirsten sarcoma virus (KA31) transformed BALB/c 3T3 mouse fibroblast cell lines. The 80-kDa kinase C dependent phosphoprotein (pp80), an in vivo marker of kinase C activity, was markedly decreased in the transformed cells although the amount of the 80-kDa substrate protein in the BPA31 cells was similar to that in the untransformed A31 cells. Total cell lysate kinase C levels were lower in the transformed cells but this difference could not account for the reduced pp80 phosphorylation. Increased affinity of kinase C for the membrane fraction in the BPA31 cells may account for decreased phosphorylation of pp80.

Animals↗
PubMed1989

The effect of glutathione content on renal function following warm ischemia.

Reperfusion after ischemia produces tissue injury due to free radicals generated during the reflow period. Glutathione (GSH) mediates against this oxidant damage by scavenging free radicals and protecting cells against injury. In an attempt to reduce the injury caused by free radicals, rat kidneys were pretreated with GSH monoethyl ester to elevate renal GSH fivefold. Previous studies in a renal artery occlusion model showed that pretreated kidneys in comparison to untreated controls were functionally impaired as measured by glomerular filtration rate, urine flow rate, and histology. To eliminate systemic effects of the pretreatment, kidneys were subjected to a fixed period of warm ischemia but flushed of blood and transplanted into nonpretreated syngeneic recipients. As before, pretreated kidneys exhibited marked functional impairment. We conclude that (i) elevation of renal GSH with GSH monoethyl ester enhances rather than prevents renal dysfunction and (ii) the enhancement of renal ischemic injury following pretreatment is not due to nonspecific systemic effects of GSH monoethyl ester pretreatment.

Animals↗
PubMed1989

The simultaneous occurrence of renal artery stenosis and an aldosteronoma in a patient with hypertension.

The simultaneous occurrence of renovascular hypertension and an adrenocortical adenoma is a rare entity. The case of a 64-year-old woman who underwent an aortorenal bypass graft for renovascular hypertension requiring a multidrug antihypertensive regimen is presented. Persistently elevated blood pressures in the postoperative period prompted further workup for other causes of hypertension. Laboratory evaluation showed hyperaldosteronism and hyporeninemia despite enalapril administration. Abdominal computerized tomography (CT) revealed a left adrenal mass which, on surgical removal, was found to be a cortical adenoma. Subsequently, her antihypertensive therapy has been reduced to a single agent. Previous authors have described only four patients with malignant hypertension who had the rare clinical combination of renal artery stenosis and an aldosteronoma. This case reemphasizes the critical need for a thorough search for other surgically correctable lesions in those patients who remain severely hypertensive after the "definitive" operation.

Adenoma↗
PubMed1989

Nickel transport by the thermophilic acetogen Acetogenium kivui.

Exogenous 63Ni was incorporated into carbon monoxide dehydrogenase when Acetogenium kivui ATCC 33488 was cultivated in the presence of 63NiCl2. The capacity for nickel (63NiCl2) transport was greatest with cells harvested from the mid- to late exponential phases of growth. Nickel transport was linear during the transport assay period and displayed saturation kinetics. The apparent Km and Vmax for nickel transport by H2-cultivated cells approximated 2.3 microM Ni and 670 pmol of Ni transported per min per mg (dry weight) of cells, respectively. The nickel transport system was not appreciably affected by the other divalent cations that were tested, and transported nickel was not readily exchangeable with exogenous nickel. Nickel transport was stimulated by glucose or H2 and was decreased by various metabolic inhibitors; however, nickel uptake by glucose- and H2-cultivated cells displayed differential sensitivities to ATPase inhibitors.

Aldehyde Oxidoreductases↗
PubMed1988

Combined kidney and pancreas transplantation in diabetics.

Kidney and pancreaticoduodenal transplantation were simultaneously performed in 12 insulin-dependent diabetic patients. These patients had advanced secondary complications, including blindness, vascular disease, and disabling neuropathy. Average posttransplant hospitalization and charges were 17.7 days and $42,780 compared with 11.2 days and $29,000 for patients who received renal allografts alone. Following transplantation, blood glucose and glycosylated hemoglobin A levels promptly returned to normal in all patients. Two patients subsequently died, one after five months of a cytomegalovirus infection and one after seven months of a ruptured bladder. After a mean of 11.6 months of follow-up, ten patients (83%) remained independent of insulin and dialysis. The success of pancreas transplantation in diabetics with advanced complications now approaches that of other organ allografts. It therefore appears reasonable to recommend transplantation for diabetics with less severe secondary complications, since these candidates are most likely to realize the potential benefits of long-term normoglycemia.

Adult↗
PubMed1988

Energy-dependent, high-affinity transport of nickel by the acetogen Clostridium thermoaceticum.

The nickel transport system of Clostridium thermoaceticum was investigated with 63NiCl2 and an anaerobic microfiltration transport assay. Transport was optimal at pH 7 to pH 7.5 and 65 degrees C and decreased in the presence of metabolic uncouplers and inhibitors. Exogenous nickel was concentrated 3,000-fold over the apparent nickel concentration gradient during typical transport assays. Stored cellular energy appeared to provide a short-term energy source to power nickel transport, and starvation experiments demonstrated external energy source stimulation of nickel translocation. The apparent Km and Vmax for nickel transport by carbon monoxide-dependent chemolithotrophic cells approximated 3.2 microM Ni and 400 pmol of Ni transported per min per mg of cells (dry weight), respectively. Magnesium, calcium, cobalt, iron, manganese, and zinc did not inhibit the transport of nickel.

Anaerobiosis↗
PubMed1987

Cell cycle and growth factor-dependent phosphoprotein of 78kD differently regulated in normal and transformed mouse fibroblasts.

A novel 78kD phosphoprotein (pp78) of BALB/c 3T3 mouse fibroblasts is reported. Its properties of appearance in late G1 phase, dependence on specific growth factors, and altered constitutive kinetics in benzo(a)pyrene-transformed (BPA31) cells suggest its role in growth and transformation. Pp78 phosphorylation is in a dynamic state and is stabilized by inhibitors of protein and mRNA synthesis, possibly because of inhibition of a labile phosphatase or protease. Its disappearance in S phase and its low level in exponential cells also indicate a dynamic control that is dependent on growth conditions. Enhancement by phorbol myristate acetate indicates that phosphorylation of pp78 is a consequence of protein kinase C activation, but it appears much later than does an 80kD phosphoprotein (pp80), which is a recognized substrate of kinase C. No simple relation between the appearance of pp78 and mitogenesis was found. Two other phosphoproteins varied with growth conditions. One is the pp80 kinase C substrate which was found in the untransformed (A31) 3T3 cells early after stimulation but was absent in BPA31 cells. The other is an 18kD phosphoprotein that appeared shortly after quiescent 3T3 cells were stimulated.

Animals↗
PubMed1986

Insulin-like growth factor I regulation of transcription and replicating enzyme induction necessary for DNA synthesis.

Insulin-like growth factor I (IGF-I) regulation of the sequence of transcriptional, translational, and postranslational events during G1 that are necessary for DNA synthesis, and the induction of thymidine kinase and in vivo thymidylate synthase activities was studied in synchronized confluent BALB/c 3T3 mouse fibroblasts. IGF-I was the only growth factor necessary from 6 to 2 1/2 hours before S phase for onset of DNA synthesis. 5,6 dichlororibofuranosylbenzimidazole (DRB), an inhibitor of transcription, was ineffective in blocking DNA synthesis and increase of both enzyme activities during an interval of about 2 1/2 hours before S phase. Cycloheximide, an inhibitor of translation, was ineffective in blocking DNA synthesis and the increase of in vivo thymidylate synthase activity during an interval of about 1 1/2 hours before S phase but was effective in blocking the increase of thymidine kinase activity up to the G1/S boundary. The results demonstrate that IGF-I is dispensable beyond the R-point (2-3 hours before S phase), the time when serum factors are no longer necessary for the initiation of DNA synthesis, and that IGF-I regulates transcriptional events necessary for both DNA synthesis and the induction of thymidine kinase and in vivo thymidylate synthase. The results also demonstrate a posttranslational interval for in vivo thymidylate synthase, suggesting posttranslational modification of this enzyme.

Animals↗
PubMed1985

Quaternary structure of pyruvate dehydrogenase complex from Escherichia coli.

The pyruvate dehydrogenase complex of Escherichia coli and subcomplexes derived from it by selective removal of component enzymes have been subjected to quaternary structural analysis by scanning transmission electron microscopy. Scanning transmission electron microscopic images of the intact complex (E1E2E3), the dihydrolipoyl transacetylase-dihydrolipoyl dehydrogenase (E2E3) subcomplex, and the E2 core enzyme appear as cubic particles in various orientations. Mass distributions within this complex and its subcomplexes have been determined by radial mass analysis of similarly oriented scanning transmission electron microscopic images of each type. The data show that mass attributable to dihydrolipoyl dehydrogenase (E3) is well integrated into the structural framework of the E2 core, dihydrolipoyl transacetylase, whereas mass attributable to pyruvate dehydrogenase (E1) is located about the periphery of the core enzyme. The mass distributions are fully consistent with a structural model in which 6 E3 dimers are integrated into the six faces of the cubic E2 core, and 12 E1 dimers are associated along the 12 edges of the core enzyme.

Escherichia coli↗