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R K Li

Publications and source records attributed to R K Li.

71 records · Page 4Linked to original sources
PubMed1991

The limits of cardiac preservation with University of Wisconsin solution.

Previous studies from this institution have suggested that University of Wisconsin solution is preferred for prolonged cardiac storage and preserves high-energy phosphates better than other storage fluids. University of Wisconsin solution contains adenosine (5 mmol/L), which may maintain the concentration of myocardial adenine nucleotides. Cultures of human adult myocytes were grown from left ventricular biopsy specimens obtained from patients undergoing coronary bypass procedures. Cells (seven to nine dishes per group) were rinsed of culture medium and stored at 0 degrees C in University of Wisconsin solution. Cells were analyzed for adenine nucleotide content after 1, 6, 12, and 24 hours of storage by high-performance liquid chromatography (units = nmol/microgram DNA) and compared with control samples (0 hour). Adenosine concentration increased from 0.03 +/- 0.02 (mean +/- standard deviation) to 1.77 +/- 1.03 by 1 hour (p less than 0.0001, analysis of variance) and remained increased thereafter. Adenosine was largely degraded to inosine (0 hours, 0.03 +/- 0.03; 6 hours, 0.88 +/- 0.56; p less than 0.001) and hypoxanthine (0 hours, 0.01 +/- 0.01; 6 hours, 0.15 +/- 0.09; p = 0.004). Measured levels of xanthine and uric acid were extremely low at all time intervals. Adenosine triphosphate levels were maintained at 1 hour (0 hours, 0.64 +/- 0.38; 1 hour, 0.67 +/- 0.45) but declined thereafter (6 hours, 0.21 +/- 0.21; 12 hours, 0.11 +/- 0.09; 24 hours, 0.04 +/- 0.03; p less than 0.0001). Levels of adenosine diphosphate (p = 0.007) and adenosine monophosphate (p less than 0.05) decreased to approximately 25% of original values by 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine Nucleotides↗
PubMed1991

Prolonged preservation with University of Wisconsin Solution.

Previous studies from this institution using human cell cultures have suggested that University of Wisconsin Solution may be preferred for prolonged cardiac storage. University of Wisconsin Solution (UWS) contains adenosine (5 mmole/liter) which could maintain adenine nucleotides better than other storage fluids. Human cardiomyocytes were isolated from left ventricular biopsies. Cells (seven to nine dishes/group) were rinsed of culture media and placed in one of four solutions: Stanford cardioplegia, phosphate-buffered saline, modified EuroCollins', or UWS. Metabolites were assessed using high-performance liquid chromatography (units = nmole/micrograms DNA) after 24 hr of storage at 0 degrees C and compared to baseline controls (BASE). Adenosine triphosphate (P less than 0.0001, ANOVA), adenosine diphosphate (P less than 0.0001), and adenosine monophosphate (P less than 0.01) decreased with each solution compared to BASE but were maintained best with UWS (P less than 0.05). Adenosine increased in the UWS cells only (BASE, 0.029 +/- 0.118; UWS, 1.836 +/- 1.110; P less than 0.0001, ANOVA). Adenosine in the UWS cells was largely degraded to inosine (UWS, 1.013 +/- 0.779; BASE, 0.034 +/- 0.032; P less than 0.0001) and hypoxanthine (UWS, 0.124 +/- 0.091; BASE, 0.005 +/- 0.005; P less than 0.001). University of Wisconsin Solution does preserve adenine nucleotides better than other storage fluids and may improve the clinical results of cardiac transplantation.

Adenine Nucleotides↗
PubMed1991

A cell surface/plasma membrane antigen of Candida albicans.

Antibody from BALB/cByJ mice immunized against a membranous fraction of Candida albicans agglutinated whole cells as well as the membranous fraction. Hybridoma techniques were used to isolate an IgM monoclonal antibody (mAb) designated 10G which agglutinated whole cells and reacted with the subcellular fraction. Yeast cells of 15 additional C. albicans strains and isolates of C. stellatoidea, C. tropicalis, C. intermedia and C. lusitaniae were also agglutinated by mAb 10G. The antigen was not detected on other fungi, including Candida krusei, C. utilis, Cryptococcus neoformans, Cr. albidus, Torulopsis glabrata, Rhodotorula spp. and Saccharomyces cerevisiae. To determine the cellular location of the epitope to which mAb 10G is specific, freeze-substitution was compared with traditional chemical fixation methods in preparation of samples for immunocolloidal gold electron microscopy (IEM). With both fixation procedures, the antigen recognized by mAb 10G was found randomly and densely concentrated on the plasma membrane on exponential-phase yeast-form cells and had a patchy distribution on the cell wall surface. Association of the antigen with the plasma membrane was confirmed by IEM of isolated membranes. On developing hyphal cells, antigen appeared first on the plasma membrane and later on the cell wall surface. Treatment of yeast cells with beta-mercaptoethanol and Zymolyase before fixation removed the antigen from the surface but left the cytoplasmic antigen undisturbed. Treatment of yeast cells or solubilized antigen with heat or proteolytic enzyme (trypsin, Pronase B, proteinase K) did not remove or destroy the antigen, suggesting a non-protein nature of the epitope.

Agglutination↗
PubMed1991

Evidence for expression of the C3d receptor of Candida albicans in vitro and in vivo obtained by immunofluorescence and immunoelectron microscopy.

The complement conversion product C3d binds to a receptor on the cell surface of Candida albicans. While the function of this receptor is still uncertain, we investigated whether it is expressed during a murine infection. Rabbit antiserum raised against purified receptor was used in conjunction with immunofluorescence microscopy and immunocolloidal gold electron microscopy to examine kidney tissue and peritoneal lavages from infected mice for receptor expression by C. albicans in vivo. Specificity of the antiserum was indicated by reactivity with purified receptor (55 to 60 kDa) and with a protein of similar molecular mass from whole hyphal extracts in Western blots (immunoblots). In vitro analysis by immunofluorescence microscopy showed that the antiserum reacted with both yeast and pseudohyphal forms of the organism, but reactivity was strongest with pseudohyphae. Immunocolloidal gold electron microscopy of fungal cells from peritoneal lavages revealed intense staining of mother cells of germinative forms, germ tubes, and pseudohyphae. Staining of the mother cells was heaviest at the innermost layers of the cell wall but only scant on the cell surface. In contrast, staining was observed throughout the cell walls of germ tubes and pseudohyphae. In kidney, expression of the C3d receptor was found primarily on the cell walls of hyphae and pseudohyphae, although some staining was observed in the cytoplasm. These data support that the C3d receptor of C. albicans is expressed in vivo.

Animals↗
PubMed1991

Prolonged hypothermic cardiac storage with University of Wisconsin solution. An assessment with human cell cultures.

Hypothermic storage of cardiac allografts is routinely used for transplantation but is associated with an increased mortality when ischemic times are greater than 4 hours. The ideal storage conditions (solution and temperature) could extend the current limits of cold ischemia. Human endothelial cells and ventricular myocytes were studied to screen various solutions and temperatures for organ preservation. Four solutions (modified Euro-Collins, phosphate-buffered saline, Stanford cardioplegia, and University of Wisconsin) were evaluated. Endothelial cells were evaluated after prolonged hypothermic storage consisting of 0 degree, 4 degrees, and 8 degrees C for 36 hours, and ventricular myocytes were stored at 0 degree and 8 degrees C for 24 hours. Cell viability was determined by morphology (10 dishes per group), and trypan blue exclusion (5 dishes per group) in addition to a cell adhesion assay (endothelial cells 5 dishes per group) and adenine nucleotide analysis with high-performance liquid chromatography techniques (ventricular myocytes 5 dishes per group). Endothelial cell morphology was best preserved by University of Wisconsin solution (p less than 0.001, chi 2) and at 0 degree C (p less than 0.01, chi 2). Endothelial cells stored with University of Wisconsin solution excluded trypan blue better (1.0% +/- 0.5% cells stained, p less than 0.001. Analysis of variance [ANOVA]). Cell adhesion was poorly protected with Stanford cardioplegia (p less than 0.001, ANOVA). Myocyte morphology was preserved best with University of Wisconsin solution at 0 degree C (p less than 0.001, chi 2). According to trypan blue staining, Euro-Collins and University of Wisconsin solutions were superior to Stanford cardioplegia or phosphate-buffered solutions (p less than 0.001, ANOVA). Temperature did not influence the trypan blue results. Adenosine triphosphate was maintained best with University of Wisconsin solution at 0 degree C (p less than 0.01, ANOVA). Myocytes were more sensitive to the effects of prolonged storage compared with endothelial cells by morphologic criteria and trypan blue staining characteristics, irrespective of the shorter preservation times. University of Wisconsin solution was the most effective solution tested. Colder temperatures (0 degree to 4 degrees C) provided better protection than 8 degrees C. Myocytes were more sensitive to prolonged preservation than endothelial cells. Furthermore, the technique used appears helpful as a model of prolonged hypothermic storage and could be expanded to assess other interventions.

Adenosine Diphosphate↗
PubMed1990

Water-soluble antioxidant specificity against free radical injury using cultured human ventricular myocytes and fibroblasts and saphenous vein endothelial cells.

To better understand the protective effect of water-soluble antioxidants against free radical injury to the reperfused ischemic myocardium, we studied the antioxidant effectiveness of superoxide dismutase (SOD), catalase, ascorbic acid, and Trolox, a water-soluble analogue of alpha-tocopherol, in protecting cultured adult human ventricular myocytes and fibroblasts and saphenous vein endothelial cells from hypoxanthine-xanthine oxidase generated free radicals. The cells were cultured at oxygen tension to 150 and 40 mmHg. Passage P2 to P4 cells were injured by a hypoxanthine-xanthine oxidase free radical generation system. The time when all the cells became shriveled divided by the cell count expressed in terms of 100,000 cells was used to compare cellular susceptibilities to free radical injury and the relative effectiveness of the antioxidants. Fibroblasts were more resistant to free radical injury than myocytes which were more resistant than endothelial cells, when all three cell types were cultured at the same oxygen tension. Trolox and ascorbic acid were effective antioxidants for myocytes while SOD and catalase were ineffective. SOD and catalase were more effective than ascorbic acid as antioxidants for endothelial cells and fibroblasts, while Trolox was ineffective. In summary, we have shown that each cultured cell type has a different susceptibility to free radical damage and that antioxidants are not effective for all cell types.

Antioxidants↗
PubMed1990

The cytoprotective effect of Trolox demonstrated with three types of human cells.

Trolox, a hydrophilic analogue of alpha-tocopherol, was reported to scavenge peroxyl radicals better than vitamin E in sodium dodecyl sulfate micelles and in liposomes. However, it was not known if Trolox protects human cells against oxyradical damage or if it acts as an antioxidant there. Here we demonstrate that Trolox prolonged substantially the survival of human ventricular myocytes and hepatocyte against oxyradicals generated with xanthine oxidase plus hypoxanthine, and prevented lysis of red cells exposed to an azo-initiator (2,2'-azo-bis(2-amidinopropane) HCl). Note that Trolox did not inhibit xanthine oxidase. In each cell type, the protection by Trolox was dose dependent and surpassed those given by such water-soluble antioxidants as ascorbic acid, superoxide dismutase, and (or) catalase, each examined at or near its optimal level in the same system. Using hepatocytes as a model, we further observed that Trolox reduced markedly the quantity of phospholipid conjugated dienes (a chemical imprint of oxyradical damage) in cells despite their exposure to oxyradicals. These data suggested that Trolox behaves as an antioxidant in cells as illustrated in hepatocytes.

Antioxidants↗
PubMed1989

Myocardial salvage with trolox and ascorbic acid for an acute evolving infarction.

Both Trolox (a water-soluble analogue of alpha-tocopherol) and ascorbic acid were more effective than superoxide dismutase or catalase in protecting myocyte cell cultures from free radical attack (induced by hypoxanthine and xanthine oxidase). In a canine model of two hours of left anterior descending coronary artery occlusion followed by four hours of reperfusion, Trolox and ascorbic acid reduced the area of infarction within the area at risk. The Trolox group received 500 mL of deoxygenated saline solution containing 2.0 g of Trolox, 3.0 g of ascorbic acid, and 18 mg of EDTA (ethylenediaminetetraacetic acid) infused into the ascending aorta 30 seconds before and four minutes after reperfusion. Saline controls received 500 mL of deoxygenated saline solution containing 18 mg of EDTA. The angioplasty group had unmodified reperfusion by simple release of the occlusion. The area at risk and the area infarcted were estimated with Evans blue and triphenyl tetrazolium hydrochloride stains, respectively. The ratio of the area infarcted to the area at risk was significantly lower with Trolox (angioplasty, 30.4% +/- 5.1%; saline, 20.8% +/- 2.9%; and Trolox, 8.7% +/- 4.0%; p less than 0.01). In summary, the antioxidants Trolox and ascorbic acid effectively reduced myocardial necrosis after ischemia.

Animals↗
PubMed1989

Effect of oxygen tension on the anti-oxidant enzyme activities of tetralogy of Fallot ventricular myocytes.

Since the chronically cyanotic tetralogy of Fallot (TOF) myocardium is more sensitive to reperfusion injury after cardiac surgery than the adult myocardium, we decided to study the regulation of myocardial superoxide dismutase (SOD), catalase and glutathione peroxidase by oxygen tension. TOF myocytes were cultured at a Po2 of 150 mmHg for 30 days to establish the culture. The cells were then cultured at Po2 of 150 and 40 mmHg and the myocyte antioxidant enzymes measured at days 3, 7, 14 and 21. On day 21 the myocytes cultured at Po2 of 40 mmHg were then cultured at 150 mmHg and SOD and catalase activities measured on days 28 and 35. Although there were no differences in the rates of incorporation of 35S-methionine into the myocytes at either Po2 on these days, the myocytes scavenger enzyme levels were significantly higher by day 14 when cultured at a Po2 of 150 mmHg than at a Po2 of 40 mmHg. With the increase in oxygen tension from 40 to 150 mmHg, SOD and catalase activities increased significantly by day 35. The myocytes cultured at Po2 40 mmHg were more sensitive by day 7 to an hypoxanthine-xanthine oxidase generated free radical injury than the Po2 150 mmHg cultured cells. The regulation of these enzyme activities by oxygen tension and the increased sensitivity to free radical injury of the myocytes cultured at an oxygen tension of 40 mmHg provide putative evidence that the chronically cyanotic myocardium may be less well protected than the normally perfused myocardium against oxygen-mediated free radical injury and be at higher risk for cardiovascular surgery.

Catalase↗
PubMed1988

Effect of root agglutinin on microbial activities in the rhizosphere.

A total of 220 bacterial isolates were obtained from pea rhizosphere and nonrhizosphere samples. Of these samples, 100 isolates were chosen randomly to test for their agglutinative reaction against pea root exudate. The percentage of positive agglutination of bacteria isolated from the nonrhizosphere sample was significantly lower than that of bacteria isolated from the rhizosphere sample. Moreover, this agglutinative reaction could not be blocked either by treating the bacterial cells or root exudate with different carbohydrates before they were mixed or by boiling the root exudate first. Bacteria that could be agglutinated by pea root exudate followed the downward growth of the pea root through the soil profile. The greater abilities of such bacteria to colonize the pea rhizosphere were indicated by their higher rhizosphere-colonizing (rhizosphere/nonrhizosphere) ratios, whether the bacteria were added alone or together with nonagglutinating bacteria. However, bacteria did show different agglutinative reactions toward root exudates obtained from different plants.

Journal Article↗
PubMed1980

Central venous pressure in preterm infants.

Right atrial A-wave, mean and inspiratory pressures were measured serially every 6 h in 36 preterm infants--24 healthy and 12 with respiratory distress syndrome (RDS)--from the 2nd until 24th h of age. In healthy preterm infants, the right atrial A-wave averaged + 4.91 mm Hg with a range of + 2 and + 8 mm Hg and the right atrial mean pressure averaged + 1.62 with a range of -3 to + 4 mm Hg. Preterm infants developed RDS had significantly lower right atrial pressure (RAP) during the first 6 h of life than healthy preterm infants. RAP in preterm infants with RDS subsequently increased to normal range. RAP did not have any correlation with either birth weight or gestational age.

Birth Weight↗
PubMedDate not supplied

Albumin-bound bilirubins protect human ventricular myocytes against oxyradical damage.

Synthetic delta-bilirubin (i.e., bilirubin that is covalently bonded to albumin) and, to a lesser extent, bilirubin that is physically adsorbed to albumin substantially prolonged the survival of human ventricular myocytes against in situ generated oxyradicals. This cytoprotection, manifested at micromolar concentrations of either form of bilirubin, surpasses those given by unconjugated bilirubin alone, by equimolar levels of albumin (which has some cytoprotective activity), by known antioxidants ascorbate, mannitol, or Trolox, and by oxyradical scavenging enzymes superoxide dismutase (24,200 IU/L) plus catalase (92,000 IU/L) on the same cells. Our human cell-based data provide the first direct evidence that albumin-bound bilirubins, especially delta bilirubin, are potent circulating cytoprotectors. The latter may be important in defending, among others, the myocardium, which is much less equipped in antioxidant defences than for example the liver or intestines.

Antioxidants↗
PubMedDate not supplied

Candida dubliniensis fungemia: the first four cases in North America.

We report the first four North American cases of Candida dubliniensis fungemia, including the first isolation of this organism from the bloodstream of an HIV-infected person. All isolates were susceptible in vitro to commonly used antifungal drugs. This report demonstrates that C. dubliniensis can cause bloodstream infection; however, the incidence of disease is not known.

Adult↗
PubMedDate not supplied

Induction of interleukin-6 mRNA in rat alveolar macrophages by in vitro exposure to both Cryptococcus neoformans and anti-C. neoformans antiserum.

Lewis rat alveolar macrophages (AM) were harvested and exposed in vitro to Cryptococcus neoformans to investigate the induction of inflammatory cytokines. AM in tissue culture wells were incubated with viable yeast cells of C. neoformans or the capsular polysaccharide, glucuronoxylomannan (GXM), with or without rabbit anti-C. neoformans antiserum. At 3, 6, 12 and 24 h, AM were washed, lyzed and total RNA was isolated. Using reverse transcription-PCR, the transcripts of cytokine genes were semi-quantified by comparison with constitutive transcripts. Incubation of AM with lipopolysaccharide, as positive control, induced elevated levels of the three transcripts measured: interleukin (IL)-1 alpha, IL-6 and tumour necrosis factor (TNF)-alpha. Under the same conditions, no obvious changes were observed in the levels of transcription of these cytokines by AM after exposure to several strains of C. neoformans. However, AM that were incubated with both the yeast cells and rabbit polyclonal antisera to C. neoformans manifested significantly increased levels of mRNA for IL-6, but not IL-1 alpha or TNF-alpha. This increased level of IL-6 mRNA was detectable after incubation for 6 or 12 h. Levels of transcription in AM were unaffected by exposure to normal rabbit serum, specific antiserum alone. GXM at concentrations of 10, 100 or 500 micrograms ml-1, or GXM and antiserum. Adsorption of the antiserum with heat-killed yeast cells of C. neoformans diminished its ability to induce IL-6 mRNA in combination with fresh, viable yeast cells. The induction of IL-6 mRNA by yeast cells and antiserum does not require intact complement. In the absence of complement, the rabbit antiserum served as a potent opsonin and markedly increased phagocytosis of C. neoformans by AM. These results indicate that antibody-opsonized C. neoformans are readily phagocytosed by rat AM, and that antibody-mediated phagocytosis may differ from complement-mediated phagocytosis in the subsequent stimulation of IL-6.

Animals↗