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Biomedical subjects

K J Tsai

Publications and source records attributed to K J Tsai.

At least 19 recordsLinked to original sources
PubMed2004

Stored of Hsp72/Hsp73 in germinal vesicle-stage mouse oocytes.

Heat-shock proteins (hsps) Hsp72 and Hsp73 are the stored maternal proteins found in mouse oocytes. Both hsps appear in mouse oocytes at germinal vesicle (GV) and metaphase II (M-II)-stages as previously demonstrated by immunoblotting analysis. In this report, we further determined the presences of Hsp72/Hsp73 proteins in mouse embryos at stages of 2-pronucleus, arrested 1-cell, 2-cell, arrested 2-cell, 4-cell, arrested 4-cell, 8-cell to morula and blastocyst. Except for the blastocyst stage, the Hsp72/Hsp73 proteins were detectable in most embryo stages. The concentration of Hsp72/Hsp73 in GV-stage oocytes was higher than that in M-II-stage oocytes, and in any stages of embryos before implantation. A dramatical increase in Hsp72/Hsp73 expression was found at the 2-cell stage. Together with these findings, we speculated that hsps accumulated or stored earlier in the GV-stage mouse oocytes to protect the oocytes against environmental influences acting on ovary, and hsps may be required for zygotic gene activation and provided a protective effect against apoptosis.

Animals↗
PubMed2001

LeuO expression in response to starvation for branched-chain amino acids.

The recently identified role of LeuO in the regulation of transcription has prompted us to search for the specific function(s) of LeuO in bacterial physiology. The cryptic nature of expression of leuO has previously limited such analysis. A conditional leuO expression was found when bacteria enter stationary phase and was shown to be guanosine 3',5'-bispyrophosphate-dependent. Multiple physiological events, including the stringent response, are induced upon the increase of the bacterial stress signal, guanosine 3',5'-bispyrophosphate. In this study, we tested whether LeuO was directly involved in the bacterial stringent response. LeuO was shown to be indispensable for growth resumption following a 2-h growth arrest caused by starvation for branched-chain amino acids in an E. coli K-12 relA1 strain. This result supports a functional role for LeuO in the bacterial stringent response.

Amino Acids, Branched-Chain↗
PubMed2000

ppGpp-dependent leuO expression in bacteria under stress.

Despite the known potential transcription regulatory role of leuO gene product, LeuO, the condition when leuO expresses during bacterial growth cycle remains unclear. Mechanistically, leuO expression was shown to be part of promoter relay mechanism, however, the factor(s) responsible for the regulation of leuO expression is not known. Combining Northern and Western results, we demonstrate in the present communication that leuO expression is normally low and enhanced when bacteria are in transition from exponential growth to stationary phase. The stationary phase-associated leuO expression is ppGpp dependent and rpoS (sigma(s) factor) independent.

Bacterial Proteins↗
PubMed2000

Induction of integrin-associated protein (IAP) mRNA expression during memory consolidation in rat hippocampus.

We have previously demonstrated that hippocampal integrin-associated protein (IAP) gene expression is associated with memory formation in a one-way inhibitory avoidance learning in rats. In the present study, we further investigated the role and mechanism of IAP involved in memory consolidation in rats. Because of the minute amount of IAP present in the brain, we have adopted the quantitative reverse transcription-polymerase chain reaction (RT-PCR) method. Our results revealed that hippocampal IAP mRNA expression is approximately fourfold higher in rats showing good memory retention (GM, retention score of 600 s) at 3 h, but not at other time points, after training when compared with the poor memory rats (retention score < 80 s). On the other hand, integrin alphav mRNA level was markedly increased ( approximately twofold), while integrin beta3 mRNA level was decreased ( approximately 50%) at 1 h post-training. Further, separate sets of RT-PCR analysis revealed that IAP5 and IAP6 mRNA expressions, but not that of IAP7, were markedly increased in GM rats 3 h post-training. Moreover, regional distribution studies revealed that different isoforms of the IAP gene are similarly distributed in different brain areas, while IAP7 has been the predominant form present in astrocyte cells. These results together suggest that IAP mRNA expression is indeed induced upon training, rather than that the GM rats have constitutively higher levels of IAP. The unparallel change of IAP and integrin mRNA expressions as far as time-course is concerned suggests that they are possibly involved in different forms and stages of memory processing. Further, IAP5 and IAP6 are more closely associated with memory consolidation, while IAP7 may constitute the major isotype for signal transduction in astrocyte cells.

Alternative Splicing↗
PubMed2000

Association of CYP1A1 and microsomal epoxide hydrolase polymorphisms with lung squamous cell carcinoma.

Lung cancer is the leading cause of death among cancers in Taiwan. Although the etiology of lung cancer has yet to be defined, genetic variability in activities of metabolic enzymes has been correlated with lung cancer. In the present study, the possibility of association of CYP1A1 and microsomal epoxide hydrolase (HYL1) genetic polymorphisms with lung cancer was examined among 132 lung cancer patients and 259 controls in Taiwan. No significant association was observed for either CYP1A1 or HYL1 polymorphism alone and the overall incidence of lung cancer after adjusting for age, gender and smoking status. When cases were stratified according to histological type, there was significant association between CYP1A1*2A homozygote and squamous cell carcinoma (SCC) (odds ratio (OR) 2.86; 95% confidence interval (CI) 1.33-6.12). Similarly, the proportion of HYL1 genotypes corresponding to high or normal enzyme activities was higher in SCC than in controls (OR 1.96; 95% CI 1.04-3.70). A combination of susceptible CYP1A1 and HYL1 genotypes was found to be highly associated with lung cancer, especially with SCC (OR 6.76; 95% CI 2.29-19.10). Our results suggest that the combination of CYP1A1 and HYL1 polymorphisms is an important risk factor for lung SCC.

Base Sequence↗
PubMed1999

NAD(P)H: quinone oxidoreductase polymorphism and lung cancer in Taiwan.

Lung cancer is one of the leading causes of death in Taiwan since 1996. Genetic variation in metabolic activation or detoxification enzymes has been associated with the occurrence of lung cancer. NAD(P)H:quinone oxidoreductase (NQO1) enzyme is a cytosolic two-electron reductase thought to be involved in bioactivation and detoxification of environmental carcinogens. The possible association between NQO1 genetic polymorphism and lung cancer risk was examined among 95 male smokers without cancer and 100 male smokers with lung cancer in Taiwan. There was no significant difference in the proportion of wild-type NQO1 among all cancer cases and controls. When cases were stratified according to histological subtypes, the wild-type NQO1 was more common in adenocarcinoma than in controls. The odds ratio was 2.93 (95% confidence interval, 1.23-7.02; p = .02). This is the first observation for the positive association of this locus with lung cancer in an Asian population. These results suggest that NQO1 polymorphism is an important genetic risk factor for lung adenocarcinoma among smokers in Taiwan.

Adenocarcinoma↗
PubMed1999

Cytochrome P4502E1 genetic polymorphisms and lung cancer in a Taiwanese population.

Cytochrome P4502E1 (CYP2E1) is involved in metabolic activation of carcinogenic nitrosamines, benzene and low molecular weight halogenated hydrocarbons. In this study, we assessed the association between CYP2E1 RsaI and DraI genetic polymorphisms and lung cancer in a Taiwanese population. The RsaI genotype distribution was significantly different between 119 lung cancer patients and 231 non-cancer controls. The homozygote variants of RsaI genotypes were more common in controls (6.9%) than in lung cancer patients (0.8%). The estimated odds ratio (OR) was 0.11 (95% confidence interval (CI), 0.01-0.87). After adjusting for age, sex, and smoking status, the OR was 0.12 (95%, CI, 0.02-0.95). This is the first observation of a positive association between this locus and lung cancer in an Asian population. No significant differences in CYP2E1 DraI genotype distributions were found between cases and controls. The results of this study indicate that CYP2E1 RsaI polymorphism, but not DraI polymorphism, may contribute to the development of lung cancer in Taiwan.

Cytochrome P-450 CYP2E1↗
PubMed1999

The effects of ellagic acid on arylamine N-acetyltransferase activity in the bacterium Pseudomonas aeruginosa.

Arylamine N-acetyltransferase (NAT) activity in Pseudomonas aeruginosa was inhibited by ellagic acid (EA), a naturally occurring dietary plant phenol. By measuring the acetylation of 2-aminofluorene (2-AF), the NAT activity was determined. In P. aeruginosa ATCC 27853, a NAT activity of 1.37 +/- 0.25 nmol/min/10(10) CFU for intact cell and a NAT activity of 5.92 +/- 0.20 nmol/min/mg protein for cytosolic preparation were measured. EA (ranging from 1 to 0.125 mM) showed a dose-dependent inhibition of NAT activities in the analysis of both intact cell and cytosolic preparations. Enzymatic kinetics were determined and found that EA was a potent non-competitive inhibitor of NAT activity in P. aeruginosa ATCC 27853. EA inhibition of NAT activities in P. aeruginosa ATCC 27853 was time-dependent for at least 4 hrs. These data strongly indicated that EA could suppress NAT activity in P. aeruginosa.

Anticarcinogenic Agents↗
PubMed1998

Impaired production of nitric oxide, superoxide, and hydrogen peroxide in glucose 6-phosphate-dehydrogenase-deficient granulocytes.

Since the generation of superoxide and hydrogen peroxide by NADPH oxidase and nitric oxide (NO) by NO synthase (NOS) in granulocytes is NADPH-dependent, we investigated the production of NO, superoxide and H2O2 in glucose 6-phosphate dehydrogenase (G6PD)-deficient human granulocytes. Our results showed that upon stimulation with either 5 microg/ml of lipopolysaccharide (LPS) or 10 microM of phorbol 12-myristate 13-acetate (PMA), the production of nitrite in normal granulocytes was elevated, 252 +/- 135% and 239 +/- 72%, respectively, compared to the resting stage. In contrast, G6PD-deficient granulocytes did not produce more nitrite upon stimulation with either LPS or PMA compared to the resting stage. Western blot analysis indicated a normal expression pattern of inducible NOS in G6PD-deficient granulocytes. In addition, the production of H2O2 and superoxide was also significantly impaired in G6PD-deficient granulocytes compared to control cells. These data demonstrate that G6PD deficiency causes an impairment in the production of NO, superoxide and H2O2.

Erythrocytes↗
PubMed1998

Arecoline desensitizes carbachol-stimulated phosphatidylinositol breakdown in rat brain cortices.

To understand the effects of arecoline administration on the muscarinic cholinergic signaling pathway, rats were injected with arecoline, 10 mg/kg i.p., and the carbachol-stimulated phosphoinositide breakdown in rat brain cortical slices was examined. In vivo administration of arecoline resulted in inhibition of carbachol-stimulated phosphoinositide turnover in rat brain cortical slices. Arecoline was a partial agonist with peak effects of 30% of the maximum as obtained with carbachol. Coaddition of arecoline inhibited the carbachol-stimulated phosphoinositide breakdown. Pretreatment of rat brain cortical slices with arecoline in vitro resulted in a dose-dependent inhibition of carbachol-stimulated [3H]inositol monophosphate accumulation. The inhibition occurred rapidly, with half-maximal inhibition occurring at 15 min and maximal inhibition achieved within 60 min. The inhibition of phosphoinositide breakdown was recovered 1 h after arecoline was removed. When synaptoneurosomes were used for the ligand binding studies, arecoline pretreatment was found to have decreased the maximal ligand binding (Bmax) without inducing any marked change in binding affinity (K(D)). The influence could be recovered by incubating the synaptoneurosomes in the absence of arecoline for 2 h. Taken together, these data suggest that the underlying mechanism by which phosphoinositide turnover is inhibited is arecoline-induced receptor sequestration.

Animals↗
PubMed1997

Palladium or platinum exacerbates hydroxyl radical mediated DNA damage.

Strand breakage of supercoiled pBR322 DNA by a Fenton system is increased in the presence of palladium or platinum (Pt) ions. Neither Pd nor Pt ions can substitute for iron in the Fenton system. We have obtained several lines of evidence that Pd and Pt ions in the presence of a Fenton system can augment the production of OH., as monitored by a spectrophotometric method quantifying hydroxylated salicylate or by a fluorometric method quantifying catechol production. Furthermore, the promoting effect of both metal ions on OH. production was substantiated by the identification of multiple hydroxylated products of salicylate [2,3-dihydroxybenzoate (A), 2,5-dihydroxybenzoate (B), and catechol (C)] using HPLC. The concentrations of A, B, and C produced in the control were 4.5, 8.0, and 2.0 microM, respectively; whereas, their respective concentrations increased to 23.6, 42.0 and 10.0 microM with the addition of Pd ions. The observed phenomenon was further confirmed by the identification of HO-DMPO spin adducts using ESR spectroscopy. Taken together, our data suggest that the mechanism of Pd or Pt ion-mediated exacerbation of DNA damage by a Fenton system is due to the promotion of OH. production by these metal ions.

DNA Damage↗
PubMed1996

Enhanced vesiculation exacerbates complement-dependent hemolysis in glucose-6-phosphate dehydrogenase deficient red blood cells.

Glucose-6-phosphate dehydrogenase (G6PD) deficient red blood cells (RBCs) are known to be more susceptible to oxidant-induced hemolysis. Erythrocytes from G6PD-deficient individuals are significantly more susceptible to Ca(2+)-induced vesiculation than normal control cells. The enhanced susceptibility of G6PD-deficient RBCs to Ca(2+)-induced vesiculation is not due to ATP depletion. The remnant G6PD-deficient RBCs following vesiculation are more sensitive to complement-mediated hemolysis than control normal RBCs. A strong positive correlation exists between the level of Ca(2+)-induced vesiculation and the extent of complement mediated hemolysis.

Calcium↗
PubMed1996

Purification and characterization of endogenous digoxin-like immunoreactive factors in chicken blood.

Studies have been performed to determine whether an endogenous material capable of binding to digoxin antibodies is present in the chicken plasma. In the blood of 12 chickens without feed control, endogenous digoxin-like immunoreactive factors (DLIF) binding of digoxin antibodies in enzyme immunoassays amounted to 866 / 302 pg digoxin equivalents/mL of plasma (mean +/- SEM). Immunoreactivity of DLIF increased to 1848***331 pg/mL with a double value of control after boiling and acid pretreating the plasma. The major purification steps employed in this report were gel filtration column chromatography, high performance liquid chromatography (HPLC) and isoelectric focusing (IEF). Using HPLC for the separation, at least 10 chicken DLIFs with different molecular weight (MW) have been found. The MW of the smallest is 300 daltons (Da) while the largest is 100 kDa. The value of the isoelectric point of the most abundant type of DLIF from untreated chicken plasma is 6.3 as determined by IEF. The partially purified DLIF inhibits Na+, K(+)-ATPase from a porcine cerebral cortex as well as three human red blood cell membrane preparations in a dose-response fashion.

Animals↗
PubMed1996

Improved fluorometric quantification of urinary xanthurenic acid.

Measurement of urinary xanthurenic acid (XA) has been used clinically to study a variety of disorders caused by vitamin B6 deficiency. To obviate some cumbersome steps of current methods for measuring XA in human urine, we have developed a simple fluorometric method. We apply the urine sample to a solid-phase extraction column containing trimethylaminopropyl group bound to silica, which enables us to purify and concentrate the XA from the urine without contamination from various tryptophan metabolites. The XA in the acidic eluate can then be quantified fluorometrically. The linearity of the proposed method extends from 0.2 to 10.0 mg/L. The method is precise, yielding day-to-day CVs for two pooled control specimens (1.08 and 1.90 mg/L) of 1.2% and 2.6%, respectively. Correlation studies with an established HPLC method and with a spectrophotometric procedure showed correlation coefficients of 0.99 and 0.98, respectively. Interference from vitamin C, uric acid, salicylate, acetaminophen, vanillylmandelic acid, and homovanillic acid was insignificant. The proposed method for urinary XA is rapid, simple, and suitable for routine use in the clinical laboratory.

Chromatography, High Pressure Liquid↗
PubMed1993

Formation of a phosphorylated enzyme intermediate by the cadA Cd(2+)-ATPase.

Plasmid-mediated resistance to cadmium occurs by means of energy-dependent efflux mediated by a P-ATPase. Formation by the cadA protein of a phosphorylated enzyme intermediate characteristic of members of this class of enzymes was identified by acid pH-sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The formation of the phosphorylated product is dependent upon the presence of the cadA gene product and cadmium. Zinc does not induce labeling, although the determinant has been reported to confer resistance to that cation. The phosphoenzyme product is acid-stable and labile in the presence of alkali or hydroxylamine. Pulse-chase experiments with unlabeled ATP indicate rapid enzyme turnover. The label is also chased in the presence of ADP, suggesting a reversible reaction.

Adenosine Triphosphatases↗