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Biomedical subjects

M Tsao

Publications and source records attributed to M Tsao.

13 recordsLinked to original sources
PubMed2001

Small-scale bioreactor system for process development and optimization.

An agitated 12-well microtiter plate system with a working volume of 2ml was investigated for cell culture process development. Agitation assures homogeneity in wells and enhances mass transfer between the gas and the liquid phase, thus improving maximum cell density and pH stability. The pH of the NaHCO(3)-buffered system can be adjusted by altering the carbon dioxide content of the gas phase. The non-toxic, visual pH indicator phenol red was used in combination with a spectrophotometric plate reader for rapid and precise pH measurements. For high throughputs, cell growth was assessed non-invasively using stable green fluorescent protein (GFP) expressing cells and a fluorescence plate reader. The setup is simple and inexpensive. The system can be automated and allows several hundred small-scale bioreactor experiments to be run in parallel.

Journal Article↗
PubMed2000

Colorectal carcinomas in mice lacking the catalytic subunit of PI(3)Kgamma.

Phosphoinositide-3-OH kinases (PI(3)Ks) constitute a family of evolutionarily conserved lipid kinases that regulate a vast array of fundamental cellular responses, including proliferation, transformation, differentiation and protection from apoptosis. PI(3)K-mediated activation of the cell survival kinase PKB/Akt, and negative regulation of PI(3)K signalling by the tumour suppressor PTEN (refs 3, 4) are key regulatory events in tumorigenesis. Thus, a model has arisen that PI(3)Ks promote development of cancers. Here we report that genetic inactivation of the p110gamma catalytic subunit of PI(3)Kgamma (ref. 8) leads to development of invasive colorectal adenocarcinomas in mice. In humans, p110gamma protein expression is lost in primary colorectal adenocarcinomas from patients and in colon cancer cell lines. Overexpression of wild-type or kinase-dead p110gamma in human colon cancer cells with mutations of the tumour suppressors APC and p53, or the oncogenes beta-catenin and Ki-ras, suppressed tumorigenesis. Thus, loss of p110gamma in mice leads to spontaneous, malignant epithelial tumours in the colorectum and p110gamma can block the growth of human colon cancer cells.

Adenocarcinoma↗
PubMed1999

Quantification of glutamine in proteins and peptides using enzymatic hydrolysis and reverse-phase high-performance liquid chromatography.

An enzymatic method for hydrolyzing bovine milk proteins was developed. Purified milk proteins (alpha-lactalbumin, beta-lactoglobulin, and beta-casein) were hydrolyzed in 0.1 M Hepes buffer (pH 7.5) containing pronase E, aminopeptidase M, and prolidase at 37 degrees C for 20 h. Free glutamine and other amino acids were derivatized with phenylisothiocyanate and separated using a C18 Pico-Tag column. Amino acids were eluted from the column with an aqueous sodium acetate-acetonitrile gradient with detection at 254 nm. Glutamine recoveries from hydrolyzed alpha-lactalbumin, beta-lactoglobulin, and beta-casein were 78 +/- 4, 98 +/- 3, and 101 +/- 3% of the theoretical values, respectively. The recoveries of most amino acids were comparable with those obtained using acid hydrolysis, except for the recoveries of proline and acidic amino acids. These peptide bonds appeared to be resistant to enzymatic hydrolysis and also to inhibit the hydrolysis of adjacent amino acids. Free glutamine was found to be very stable (97% recovery) under the enzymatic hydrolysis conditions.

Amino Acids↗
PubMed1999

Expression and prognostic significance of metalloproteinases and their tissue inhibitors in patients with small-cell lung cancer.

PURPOSE: Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are important in tumor development and progression. MMP expression has been correlated with advanced clinical stage and poor survival in some tumors, but data for small-cell lung cancer (SCLC) are lacking. The aim of this study was to assess the expression of MMPs and TIMPs in SCLC and to evaluate their importance relative to standard prognostic factors. PATIENTS AND METHODS: Expression of MMP-1, -2, -3, -9, -11, -13, and -14 and TIMP-1, -2, -3, and -4 was evaluated by immunohistochemistry (IHC). In situ hybridization was used to confirm expression of specific mRNAs. Clinical data collected included sex, tumor stage, performance status, weight loss, hematology (hemoglobin, WBC, platelets) and biochemistry (sodium, albumin, alkaline phosphatase, lactate dehydrogenase), treatment, and survival. RESULTS: Samples from 46 patients were evaluated: 30 males, 16 females; 29 limited, 17 extensive stage; 35 Eastern Cooperative Oncology Group performance status 0-1. Positive IHC staining was evident for MMP-1 and -9 in 60% to 70% of tumor cells, and for MMP-11, -13, and -14 and TIMP-2 and -3 in 70% to 100% of tumor cells. Stromal staining of TIMP-1 to -3 was present in less than 30% of specimens. On multivariate analysis, only stage and decreased tumoral expression of TIMP-1 were significant for response (P =.043). Significant factors for survival were tumor stage (P =.0021); weight loss (P =. 013); and high tumor cell expression of MMP-3 (P =.077), MMP-11 (P =. 031), and MMP-14 (P =.019). MMP and TIMP expression did not differ significantly between stages. CONCLUSION: MMPs and TIMPs are widely expressed in SCLC. Increased tumoral expression of MMP-3, -11, and -14 were independent negative prognostic factors for survival. The results support the evaluation of synthetic MMP inhibitors in patients with SCLC.

Carcinoma, Small Cell↗
PubMed1994

Cross-reactive antibodies in the serum of balb/c mice immunized with thyroid or eye muscle membranes.

During the course of immunizing balb/c mice with eye muscle (EM) or thyroid (THY) membranes for monoclonal antibody (MCAB) production their sera frequently contain antibodies which react against both EM and THY membranes in enzyme-linked immunosorbent assay (ELISA) and SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting. In order to further study this phenomenon we have analyzed sera from 27 balb/c mice, including 10 that were studied serially, and their tissues examined histologically at sacrifice. Following immunization serum and, in some cases, the corresponding MCAB produced by fusion of the mouse spleen cells with a mouse myeloma cell line, were tested for EM and THY cross-reactivity in an ELISA and by immunoblotting. The number of antibodies demonstrated in Western blotting identified as bands of reactivity, and ELISA levels, expressed as optical density--increased with time, each peaking at around 10-12 weeks. THY and EM antibody cross-reactivity was demonstrated in the majority of mice, serum from mice immunized with THY membranes reacting with these membranes as well as with pig EM membranes in both ELISA and immunoblotting and, conversely, sera from mice immunized with pig EM membranes also reacting with THY membranes in the two tests. In Western blotting a variety of THY and EM-reactive antibodies were demonstrated including those directed against a 64 kDa protein, shown to be an important autoantigen in thyroid-associated ophthalmopathy. There was also some cross-reactivity with brain membranes, used as control antigen in both tests and in immunization, although to a lesser degree, but very little to liver and orbital connective tissue membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Changes in the fluorescence of bound nucleotide during the reaction catalysed by glucose-fructose oxidoreductase from Zymomonas mobilis.

The reduction of gluconolactone by glucose-fructose oxidoreductase containing tightly bound NADPH (enzyme-NADPH) is biphasic in nucleotide fluorescence. The initial rapid decrease, which represents quenching of the fluorescence by bound lactone, is followed by a slower decrease which corresponds to the change in absorbance. At low glucose concentrations, the oxidation of glucose by enzyme-NADP+ involves a single first-order process with similar rate constants in fluorescence and absorbance. At higher glucose concentrations, the apparent first-order rate constants for the fluorescence change are less than those for the absorbance change. This is consistent with a mechanism in which the fluorescence change occurs during the lactone dissociation step, which is slower than the hydrogen transfer step during which the absorbance change occurs. The rate constant for gluconolactone dissociation is 360 +/- 10 s-1 and this step is therefore rate-determining for the overall reaction. Reduction of fructose by enzyme-NADPH is first order with a limiting rate constant of at least 2000 s-1.

Carbohydrate Dehydrogenases↗
PubMed1991

Quantity of protein deposited on hydrogel contact lenses and its relation to visible protein deposits.

The purposes of this study were to determine if the quantity of protein deposited (QPD) upon hydrogel lenses was affected by enzymatic cleaning and to test the potential relation between QPD and visible protein deposition (VPD) and change. Seventy-four contact lens patients classified as "heavy depositors" wore new lenses for an average of 80 (SD = 32) days. Cleaning and disinfection solutions varied. One lens was cleaned weekly by a papain enzymatic treatment. The distribution of QPD measurements was bimodal and was related to the FDA material for nonionic, low water content lenses (FDA Materials Group no. 1). The mean deposition was 45 micrograms/cm2 (N = 112) compared with that of ionic, high water content lenses (FDA Materials Group no. 4), which was 1010 micrograms/cm2 (N = 30). VPD distributions were the same for the FDA Group no. 1 and no. 4 lenses. Enzymatic treatment did not significantly reduce QPD; however, enzymatic treatment did reduce VPD. Thus QPD and VPD are independent phenomena and possible reasons for this are given.

Adult↗
PubMed1989

Purification of a glycosaminoglycan-stimulatory lymphokine from supernatants of in vitro-activated human mononuclear cells.

Glycosaminoglycans (GAGs), like collagens, are the major component of the connective tissue matrix. Fibroblasts are responsible for the production and maintenance of this matrix. Glycosaminoglycan-stimulatory factor (GAG-SF) from T lymphocytes is a lymphokine that selectively increases GAG synthesis in normal human dermal fibroblasts. Supernatants of mononuclear cells activated with a mitogen, concanavalin A, were used to purify GAG-SF to an apparent homogeneity. The GAG-SF proved to be a glycoprotein with a molecular weight of 67,000 and pI of 5.6. It was not mitogenic to fibroblasts and did not regulate collagen synthesis in confluent fibroblast cultures. The purified factor was distinct from interleukin-1 (IL-1), but it could synergize with IL-1, which was present in unpurified supernatants, in modulating the activation of fibroblasts. The purification and characterization of this lymphokine are important because it is a product of activated lymphocytes and thus may be involved in the immunopathogenesis of several human diseases characterized by the presence of lymphoid infiltrates in the target organ such as autoimmune diseases of the connective tissue, the stromal reactions in human tumors, and the fibrosis associated with chronic rejection of transplanted organs.

Cell-Free System↗
PubMed1986

Production of a glycosaminoglycan stimulatory factor by cloned human T lymphocytes activated in vitro.

Supernatants of mitogen-activated mononuclear cells contain a factor which stimulates, up to fifteen-fold, the synthesis of glycosaminoglycan (GAG) by cultured normal dermal fibroblasts. To demonstrate that the GAG stimulatory factor is a product of T lymphocytes, we cloned normal peripheral blood T lymphocytes that were activated in mixed lymphocyte culture. Selected alloreactive T cell clones were expanded in the presence of original stimulator cells and T cell growth factor. Only supernatants of the clones that were reactivated with irradiated stimulators (allogeneic peripheral blood lymphocytes of B cell lines) were capable of increasing, 3-7-fold, the GAG synthesis by dermal fibroblasts. The production of GAG stimulatory activity by alloreactive T cells was restricted by HLA-DR allorecognition. Alloactivated T cell clones produced more GAG stimulatory activity on a per cell basis than did concanavalin A-activated mononuclear cells. These results show that cloned, activated T lymphocytes are capable of releasing soluble factors that modulate GAG synthesis by normal dermal fibroblasts.

Clone Cells↗
PubMed1975

Hepatic and metabolic effects of ethanol on rhesus monkeys.

Rhesus monkeys were tube-fed 100 calories per kg of a liquid diet based on casein in which 41% of the calories were derived from grain alcohol. The alcohol intake was 5.8 g per kg per day. Control diets contained isocaloric amounts of glucose. The protein content of the diet was 15% and fat supplied 21% of the calories. After 28 days the animals which had been fed ethanol developed hepatic fatty change and serum L.D.H. levels were elevated. The most striking electron microscopic changes in the alcohol animals were mitochondrial swelling, focal cytoplasmic degradation, and dilatation of the rough endoplasmic reticulum. In the monkeys which had received ethanol the metabolism of alcohol increased from 17.4 mg per 100 ml per hour to 26.6 mg and antipyrene half-life decreased from 61.0 minutes to 49.9 minutes. The carbohydrate animals showed no significant change in alcohol metabolism or antipyrene half life. The ethanol animals lost weight significantly while the carbohydrate animals gained significantly. The metabolic effects of alcohol thus were not reproduced by glucose. Administration of phenobarbital at 30 mg per kg for 5 days increased alcohol metabolism from 16.5 mg per hour to 22.5 mg per hour and shortened antipyrene half life from 76.5 minutes to 33.6 minutes. Alcohol and phenobarbital both induced enhanced drug metabolism but alcohol was a more powerful inducer of its own metabolism than phenobarbital. Phenobarbital on the other hand was a better inducer of antipyrene metabolism than alcohol.

Animals↗
PubMedDate not supplied

Dispersion models and longitudinal data analysis.

Dispersion models provide a flexible class of non-normal distributions with many potential applications in biostatistics, accommodating a wide range of continuous, discrete and mixed data. Starting with Liang and Zeger's generalized estimating equation method, we review some recent applications of dispersion models in longitudinal data analysis, including state space models based on the Tweedie class of exponential dispersion models. In medical applications the latent process of a state space model may often be interpreted as an unobserved potential morbidity process, which is modelled as a function of time varying covariates. By allowing a multivariate response vector of 'symptoms', the model integrates several response variables of mixed types into a single model. For growth curve models, the latent process reflects the 'true' growth.

Air Pollutants↗