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Biomedical subjects

W Li

Publications and source records attributed to W Li.

At least 1,387 records · Page 77Linked to original sources
PubMed1985

Perioperative ischemic injury after coronary bypass graft surgery.

Two hundred twelve patients who underwent isolated coronary bypass graft surgery were prospectively evaluated for perioperative ischemic injury. All patients underwent preoperative and postoperative testing with technetium 99m pyrophosphate first-pass ventriculography combined with myocardial uptake scans, 12-lead electrocardiography, and serial creatinine phosphokinase MB determination. Fifteen percent of the patients had ischemic injury with at least two test results positive, but only 4 percent had positive results of all three tests. No single test proved adequate. Enzyme levels were highly sensitive and had value as a screening test. The electrocardiogram was specific but only moderately sensitive. The single best test was the radionuclide scan with good sensitivity and no false-positive results. All three tests are required to rigorously diagnose ischemic injury.

Coronary Artery Bypass↗
PubMed1985

Characterization of glucose transport by bovine retinal capillary pericytes in culture.

The transport of D-glucose and its non-metabolizable analog, 3-o-methyl-D-glucose (3-o-MG), by cultured bovine retinal capillary pericytes was characterized. A preference for D-glucose over L-glucose uptake by pericytes indicated a stereospecific process. The 3-o-MG transport appeared to follow complex kinetics. At low substrate concentrations, 3-o-MG transport had an apparent Km of 1.53 mM and a Vmax of 0.50 nmol (microgram DNA)-1 min-1 at 37 degrees C. A reduced extracellular sodium concentration, energy poisons, and exogenous insulin did not significantly influence 3-o-MG uptake. Inhibition of the uptake or efflux of 3-o-MG by cytochalasin B or phloretin, respectively, and the demonstration of a 'counter transport' phenomenon showed that 3-o-MG transport by retinal capillary pericytes in culture was a carrier-mediated process.

3-O-Methylglucose↗
PubMed1985

The effects of glucose and an aldose reductase inhibitor on the sorbitol content and collagen synthesis of bovine retinal capillary pericytes in culture.

The absolute rate of collagen synthesis by cultured bovine retinal capillary pericytes, determined using the specific radioactivity of proline in the cellular amino acid pool, was compared in media containing different concentrations of glucose (5, 10 or 40 mM) and Sorbinil (0.0 or 0.1 mM), an inhibitor of aldose reductase. The absolute rate of collagen synthesis, in proline molar terms, by pericytes in medium with 5 mM glucose was 3.3 +/- 1.9 (S.D.) pmol 10(-7) cells 24 hr-1, and increased significantly to 8.8 +/- 3.7 pmol 10(-7) cells 24 hr-1 when the glucose concentration was increased to 40 mM. Sorbinil (0.1 mM) reduced the elevated sorbitol contents of pericytes induced by high concentrations of glucose, but did not significantly change the absolute rate of collagen synthesis per cell.

Aldehyde Reductase↗
PubMed1984

T and B cells induce macrophages which suppress proliferation but not lymphokine secretion.

In vitro culture of mouse spleen cells for 2 days or more leads to the production of adherent, phagocytic, Thy-1-, Ia+, Lyt-2- cells ("suppressor macrophages") which strongly inhibit the proliferative response of T and B lymphocytes to a variety of stimuli: mitogens, specific antigens, and antigen-nonspecific growth factors. Suppressive activity fails to develop, however, in cultured spleen cells from which nonadherent cells have been removed before the initial 48-hr incubation, and only partial suppression is obtained from cell suspensions from which T cells have been depleted before culture. We find that the requirement for nonadherent cells can be replaced by graded doses of lymphocytes. Lyt-2- and Lyt-2+ T cells are about equally potent in inducing suppressive activity in nonadherent cells. Surprisingly, B cells (containing fewer than 0.1% contaminating T cells) are also able to induce suppression in this system. The suppression induced includes both indomethacin-sensitive and indomethacin-resistant components. Interestingly, not all stages of mitogen-induced T-cell activation are blocked by these adherent cells: proliferation is inhibited, but production of interleukin 2 (IL-2) and interleukin 3 (IL-3) is unaffected.

Animals↗
PubMed1984

Extracellular matrix production by cat retinal pigment epithelium in vitro: characterization of type IV collagen synthesis.

Feline retinal pigment epithelial cells (RPE) produced an extracellular matrix (ECM) in vitro which was located between the basal surface of the RPE and the culture plate. This ECM had three morphological components: bundle, granular and fibrillar. After 14 days in culture the basal extracellular space contained small amounts of bundle material; granular and fibrillar material were infrequently observed at this time. The amount of ECM material increased with increasing time in culture. The accumulation of the granular component extracellularly was greatest between 60 and 108 days. Fibrillar material, although occasionally observed in the ECM, appeared to be an infrequent component. By 145 days, the ECM filled the extracellular space between the RPE and the culture plate. The time-dependent increase of the ECM indicated continued synthesis and secretion of ECM into the basal extracellular space by the RPE. Confluent RPE cultures, or choroidal/scleral fibroblasts, were incubated for 24 hr with [14C]-proline. Newly synthesized collagen, either in the culture medium or the cell layer, was co-precipitated with added carrier collagen by (NH4)2 SO4. The samples, with or without reduction and alkylation, were digested with pepsin and fractioned by selective salt precipitation and carboxymethyl(CM)-cellulose chromatography. The resulting fractions were further analyzed, or purified for thin layer chromatography (TLC) amino acid analysis, by SDS-polyacrylamide gel electrophoresis (SDS-PAGE). Cultured RPE cells, but not choroidal/scleral fibroblasts, produced labelled peptides which were characterized as alpha 1 (IV), and alpha 2 (IV) collagen chains by CM-cellulose chromatography, SDS-PAGE, proline: hydroxyproline ratios and sensitivity to bacterial collagenase. In contrast, choroidal/scleral fibroblasts produced labelled alpha 1 (I), beta 12 (I) and alpha 2 (I) collagen chains. The synthesis of type IV collagen by RPE cells may reflect the production of ECM observed by electron microscopy in cultured feline RPE cells.

Animals↗
PubMed1984

Stimulation of retinal capillary pericyte protein and collagen synthesis in culture by high-glucose concentration.

The influence of glucose concentration on cell multiplication and protein synthesis was studied in synchronized, long-term cultures of bovine retinal microvessel pericytes. The cell multiplication rate and the mitotic rate were reduced in media containing 20 mM glucose to 57% and 54%, respectively, of that obtained in media containing 5 mM glucose. Elevated glucose, however, did not change the DNA content of individual cells. Protein and collagen synthesis were measured by the incorporation of radioactive proline and lysine, or the posttranslational production of hydroxyproline and hydroxylysine, respectively. High glucose stimulated protein and collagen synthesis per cell 2.2 +/- 0.10 (SD) and 2.1 +/- 0.06 times, respectively. Aspirin (0.5 mM), an inhibitor of nonenzymatic glycosylation, did not alter the effect of elevated glucose concentration on protein and collagen synthesis.

Animals↗
PubMed1984

Nonenzymatic glycosylation of bovine retinal microvessel basement membranes in vitro. Kinetic analysis and inhibition by aspirin.

Incubation of intact bovine retinal microvessels or isolated retinal microvessel basement membranes (RVBM) with radioactive D-glucose or L-glucose, followed by basement membrane collagenous protein purification, resulted in the isolation of nonenzymatically glycosylated RVBM collagens. Type IV collagen was identified in the RVBM by selective salt fractionation, SDS-polyacrylamide gel electrophoresis, amino acid analysis, and immunoprecipitation with specific antibody. Kinetic analysis of the condensation of glucose with RVBM was carried out by labeling retinal microvessel basement membranes with D-[2-3 H]-glucose and D-[6-14 C]-glucose. The rate constant for aldimine product formation, k1, was 1.95 +/- 0.24 (SD) X 10(-4) mM-1 h-1, and the rate constant for the reversed reaction, k-1, was 5.9 +/- 1.0 X 10(-2) h-1. Based on a rate constant for the Amadori rearrangement, k2, of 8.8 +/- 1.0 X 10(-3) h-1, which was the rate-determining step, the half life of this reaction was 80 +/- 9 h. These data may be useful in estimating the glycosylation of retinal microvessel basement membranes in vivo. The nonenzymatic glycosylation of retinal microvessel basement membrane proteins was progressively inhibited by increasing concentrations (0.1 to 2.0 mM) of aspirin.

Animals↗
PubMed1983

Anterior transpericardial closure of a main bronchus fistula after pneumonectomy.

A young woman sustained a penetrating wound to the right anterior chest during a vehicular accident. Septic complications led to emergency pneumonectomy followed by infection of the pleural space and disruption of the right bronchus closure. Her condition improved after creation of a pleural window for dependent drainage and gauze packing of the pleural space. Subsequently, the open bronchial stump was closed utilizing a transpericardial approach through a median sternotomy incision which permitted eventual closure of the pneumonectomy space without thoracoplasty. When the length of the bronchial stump permits its application, the transpericardial approach to postpneumonectomy bronchial fistula closure offers important advantages over conventional transpleural techniques.

Accidents, Traffic↗
PubMed1983

Binding of fluorescein and carboxyfluorescein by human serum proteins: significance of kinetic and equilibrium parameters of association in ocular fluorometric studies.

The binding of fluorescein and 5- and 6-carboxyfluorescein by human serum proteins was measured at 37 and 4 degrees C by equilibrium dialysis. The equilibrium association constants (KA) for fluorescein were 3.7 X 10(3) and 7.1 X 10(3)M-1, and for carboxyfluorescein were 3.5 X 10(3) and 7.5 X 10(3)M-1 at 37 and 4 degrees C equilibrium dialysis data, was 3.9 X 10(3) binding sites in human serum, determined from the 37 degrees C equilibrium dialysis data, was 3.9 X 10(-3)M for fluorescein and 3.3 X 10(-3)M for carboxyfluorescein. Utilizing these binding parameters it was calculated that a maximum of 93.5% of the total fluorescein and 92.0% of the carboxyfluorescein would be bound by undiluted human serum proteins at 37 degrees C. Experimental binding data obtained after prolonged equilibrium dialysis (four days) at low total fluorochrome concentrations (1.5 X 10(-4)M or less) indicated that 93.1 +/- 1.0 (S.D.)% of the fluorescein and 90.1 +/- 0.7% of the carboxyfluorescein were bound at 37 degrees C by undiluted human serum proteins. Stopped-flow kinetic spectrophotometric studies of the changes in absorptivity at 487-488 and 510 nm that occurred when the fluorochromes were bound by human serum proteins, indicated that the fluorescein and carboxyfluorescein binding reactions were 99% complete within 0.65 and 1.72 sec. These had second-order association rate constants at 25 degrees C of 3.0 X 10(3) and 1.5 X 10(3)M-1 sec-1, respectively. These findings offer a basis for calculation of bound and free fluorescein and carboxyfluorescein in vivo in human subjects.

Binding Sites↗
PubMed1983

Coronary artery disease following mediastinal radiation therapy.

Coronary artery disease occurred in four young men (mean age 41 years) who had received curative irradiation therapy for mediastinal malignancies 12 to 18 (mean 15) years previously. None was at high risk for developing coronary artery disease by Framingham criteria. Angiography demonstrated proximal coronary artery disease with normal distal vessels. Distribution of the lesions correlated with radiation dosimetry in that vessels exposed to higher radiation intensity were more frequently diseased. Three patients had coronary bypass grafting for intractable angina and are asymptomatic at 10 to 43 months. A total of 163 patients underwent mediastinal irradiation for lymphoma or thymoma between 1959 and 1980. Among the 29 who survived 10 or more years, five (18%) developed severe coronary artery disease, implicating thoracic radiotherapy as an important risk factor. Because of the importance of mantle irradiation in the treatment of lymphomas, the prevalence of these neoplasms, and the survival patterns following treatment, many long-term survivors may be at increased risk for the development of coronary artery disease. Recognition of the relationship between radiotherapy and coronary artery disease may lead to earlier diagnosis and more timely intervention. Standard surgical treatment may be particularly beneficial because of the relative youth of most of these patients and because the proximal distribution of typical lesions increases the likelihood of complete revascularization.

Adult↗
PubMed1982

Fluorescein binding to normal human serum proteins demonstrated by equilibrium dialysis.

The binding of fluorescein to normal human serum proteins in a physiologic solvent at 37 degree C was measured by equilibrium dialysis. Human serum contained 3.28 X 10(-3)M concentration fluorescein-binding sites, with an average association constant at 37 degree C of 0.54 X 10(4)M(-1). The percentage of total fluorescein bound by human serum proteins ranged from 83% to 53% when the total fluorescein concentration ranged from 6.9 X 10(-5) to 6.2 X 10(-3)M.

Binding Sites↗
PubMed1982

Carboxyfluorescein. A probe of the blood-ocular barriers with lower membrane permeability than fluorescein.

We have examined the permeability of the blood-ocular barriers to carboxyfluorescein, a dye similar in spectral properties but more polar than fluorescein. Octanol-buffer partition ratios of carboxyfluorescein, measured as an indication of lipid solubility, were approximately 1,000 times lower than those of fluorescein at pH values between 6.40 and 8.03. The partition ratios of both dyes show pronounced pH dependence. We also evaluated intraocular dye distribution by fluorescence microscopy after intravenous (IV) injection in rats. Carboxyfluorescein does not penetrate ciliary or iris epithelial cells, whereas fluorescein prominently stains these cells. Quantitative measurement of fluorescence intensity demonstrates that carboxyfluorescein does not enter the retina even when high doses are administered. Fluorescein, in contrast, can be detected throughout the retina with fluorescence intensity levels proportional to the IV dose administered. The relative inability of carboxyfluorescein to penetrate the blood-ocular barriers is not caused by greater binding to plasma proteins, since the plasma concentration of free carboxyfluorescein is greater than that of fluorescein. We conclude that carboxyfluorescein has potential experimental and clinical use as a probe of the blood-ocular barriers. Because of its low membrane permeability, it may yield a better definition of the nature of barrier abnormalities than is now possible with fluorescein.

Animals↗
PubMed1982

Binding of fluorescein and carboxyfluorescein by normal and glycosylated human serum proteins.

The binding of fluorescein and 6-carboxyfluorescein by normal, diabetic and in vitro glycosylated human serum proteins was analyzed by absorption and fluorescence spectroscopy, gel filtration and equilibrium dialysis. The absorption spectra of bound fluorochromes showed red shifts and hypochromic changes, and fluorochrome fluorescence was reduced by serum proteins. Bio-gel P-6 and Sephadex G-200 gel filtration in solvents containing free fluorochrome demonstrated that fluorescein and carboxyfluorescein were bound by serum proteins of varying molecular weights and/or diffusion rates. Equilibrium dialysis at 37 degrees C showed that human sera contained 3.5 +/- (SD) 0.4 X 10(-3)M of fluorescein and carboxyfluorescein binding sites with an average association constant of 3.9 +/- 0.2 X 10(-3)M-1. Undiluted serum proteins bound 93% of the fluorochrome at a total concentration of 2 X 10(-4)M or less. Glycosylation of serum proteins in vivo or in vitro did not change the concentration-dependent or pH-dependent binding of fluorescein or carboxyfluorescein.

Blood Proteins↗
PubMed1981

Unpredictable course of small cell undifferentiated lung carcinoma.

Twenty-nine patients with small cell lung carcinoma were examined as to ultrastructural morphology, stage of disease, and survival. Although all tumors met the light microscopic criteria for oat cell carcinoma, only 19 (66%) contained neurosecretory granules characteristic of this tumor. Of 12 patients undergoing pulmonary resection, five of six patients with non-neurosecretory tumors and two of six patients with neurosecretory (true oat cell) tumors survived more than 2 years. Survival of all patients with Stage I or II disease was significantly different from that of patients with Stage III disease. Stage together with ultrastructural morphology may carry important therapeutic and prognostic implications. Pulmonary resection appears to be effective treatment for certain subsets of patients with small cell undifferentiated carcinoma.

Aged↗