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Biomedical subjects

Y Tan

Publications and source records attributed to Y Tan.

At least 73 records · Page 4Linked to original sources
PubMed2000

Efficacy of a 1-week pantoprazole triple therapy in eradicating Helicobacter pylori in Asian patients.

BACKGROUND: The aim of the present paper was to determine the efficacy and tolerability of a 1-week treatment regimen consisting of pantoprazole and two antibiotics: clarithromycin and amoxycillin, in the eradication of Helicobacter pylori. METHODS: The patients selected had unequivocal evidence of H. pylori infection based on urease test, culture and histology on antral and corpus biopsies obtained at endoscopy. Patients received pantoprazole 40 mg twice a day, clarithromycin 500 mg twice a day and amoxycillin 1 g twice a day for 1 week and were assessed for successful eradication at least 4 weeks after completion of therapy by repeat gastroscopy and gastric biopsies. Eradication was defined as absence of bacteria in both antral and corpus biopsies tested by culture, histology and urease test. RESULTS: One hundred and six patients were recruited for the study. The mean age was 48.0 years (range: 23-74 years). Four patients defaulted follow up and five patients were not compliant (taking less than 85%) with medications. Eradication rates on per-protocol analysis were: 88/97 (90.7%; 95% CI: 83.1-95.7); and on intention-to-treat analysis they were: 88/106 (83.0%; 95% CI: 75.9-90.2). Side-effects were in general mild and tolerable: 57 of 106 (53.7%) patients complained of a bitter taste; 15 (14.1%) complained of giddiness; 10 (9.4%) complained of increased abdominal pain; 11 (11.5%) complained of lethargy and 16 (15.1%) complained of loose motions. Pre-treatment metronidazole resistance was encountered in 57/74 strains (77.0%). Clarithromycin resistance was not encountered in any of the strains. CONCLUSIONS: The pantoprazole 1-week triple therapy with amoxycillin and clarithromycin is effective in H. pylori eradication. The treatment was well tolerated by patients. Metronidazole resistance was reported in a high percentage of strains isolated from patients. Clarithromycin resistance was, however, not detected in any of the strains.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed2000

Crystallization and preliminary crystallographic characterization of recombinant L-methionine-alpha-deamino-gamma-mercaptomethane lyase (methioninase).

L-Methionine-alpha-deamino-gamma-mercaptomethane lyase (rMETase) is involved in the alpha,gamma-elimination of methionine to alpha-ketobutyrate, methanethiol and ammonia. The reaction catalyzed by rMETase reduces the methionine concentration of methionine-dependent tumor cells, arresting their growth. Towards the goal of developing rMETase into an effective antitumor therapeutic and also to understand the catalytic mechanism of this enzyme, rMETase from Pseudomonas putida has been expressed, purified and crystallized. The crystals belong to space group P2(1)2(1)2 and diffract X-rays to at least 2.68 A resolution at 100 K using synchrotron radiation. The unit cell has parameters a = 152.8, b = 154.6, c = 80.8 A and contains four molecules in the asymmetric unit.

Carbon-Sulfur Lyases↗
PubMed2000

Elevated levels of hepatocyte nuclear factor 3beta in mouse hepatocytes influence expression of genes involved in bile acid and glucose homeostasis.

The winged helix transcription factor, hepatocyte nuclear factor-3beta (HNF-3beta), mediates the hepatocyte-specific transcription of numerous genes important for liver function. However, the in vivo role of HNF-3beta in regulating these genes remains unknown because homozygous null HNF3beta mouse embryos die in utero prior to liver formation. In order to examine the regulatory function of HNF-3beta, we created transgenic mice in which the -3-kb transthyretin promoter functions to increase hepatocyte expression of the rat HNF-3beta protein. Postnatal transgenic mice exhibit growth retardation, depletion of hepatocyte glycogen storage, and elevated levels of bile acids in serum. The retarded growth phenotype is likely due to a 20-fold increase in hepatic expression of insulin-like growth factor binding protein 1 (IGFBP-1), which results in elevated levels in serum of IGFBP-1 and limits the biological availability of IGFs required for postnatal growth. The defects in glycogen storage and serum bile acids coincide with diminished postnatal expression of hepatocyte genes involved in gluconeogenesis (phosphoenolpyruvate carboxykinase and glycogen synthase) and sinusoidal bile acid uptake (Ntcp), respectively. These changes in gene transcription may result from the disruptive effect of HNF-3beta on the hepatic expression of the endogenous mouse HNF-3alpha,-3beta, -3gamma, and -6 transcription factors. Furthermore, adult transgenic livers lack expression of the canalicular phospholipid transporter, mdr2, which is consistent with ultrastructure evidence of damage to transgenic hepatocytes and bile canaliculi. These transgenic studies represent the first in vivo demonstration that the HNF-3beta transcriptional network regulates expression of hepatocyte-specific genes required for bile acid and glucose homeostasis, as well as postnatal growth.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed2000

Targeted gene delivery to pulmonary endothelium by anti-PECAM antibody.

To achieve efficient systemic gene delivery to the lung with minimal toxicity, a vector was developed by chemically conjugating a cationic polymer, polyethylenimine (PEI), with anti-platelet endothelial cell adhesion molecule (PECAM) antibody (Ab). Transfection of mouse lung endothelial cells with a plasmid expression vector with cDNA to luciferase (pCMVL) complexed with anti-PECAM Ab-PEI conjugate was more efficient than that with PEI-pCMVL complexes. Furthermore, the anti-PECAM Ab-PEI conjugate mediated efficient transfection at lower charge plus-to-minus ratios. Conjugation of PEI with a control IgG (hamster IgG) did not enhance transfection of mouse lung endothelial cells, suggesting that the cellular uptake of anti-PECAM Ab-PEI-DNA complexes and subsequent gene expression were governed by a receptor-mediated process rather than by a nonspecific charge interaction. Conjugation of PEI with anti-PECAM Ab also led to significant improvement in lung gene transfer to intact mice after intravenous administration. The increase in lung transfection was associated with a decrease compared with PEI-pCMVL with respect to circulating proinflammatory cytokine (tumor necrosis factor-alpha) levels. These results indicate that targeted gene delivery to the lung endothelium is an effective strategy to enhance gene delivery to the pulmonary circulation while simultaneously reducing toxicity.

Animals↗
PubMed2000

Biodiversity of Asian rice gall midge (Orseolia oryzae Wood Mason) from five countries examined by AFLP analysis.

Amplified fragment length polymorphism (AFLP) analysis was used to assess the biodiversity of one of the most important dipteran pests of cereals, the Asian rice gall midge (Orseolia oryzae Wood Mason). Larvae and pupae were collected at 15 locations in five Asian countries and preserved in 95% ethanol for storage, shipment, and DNA extraction using cetyltrimethylammonium bromide (CTAB). Although only approximately 1 microg of DNA was extracted from a single pupa or larva, the use of several AFLP primers in various combinations meant that this amount of DNA was sufficient to allow many DNA fingerprints to be made per individual. Fingerprints were sufficiently reproducible, especially during selective amplification, to allow the genetic diversity within a field population to be characterized. Extraction of DNA from a pool of 20 insects yielded AFLP fingerprints in which variation among individuals was sacrificed in favor of detecting differences among populations. For each location, pooled DNA was amplified with three primer pairs. A total of 261 distinct AFLP bands were identified for the 45 fingerprints. Cluster analysis, performed by the unweighted pair-group method (UPGMA), separated the populations into two distinct groups. Group I included two populations from Guangdong province of southern China and one each from Laos and Imphal in northeastern India, while group II was comprised of eleven populations from elsewhere in India (Assam, Orissa, Madhya Pradesh, Andhra Pradesh, and Kerala) and from Nepal and Sri Lanka. AFLP analysis provided insight into the origins of gall midge biotypes. In 1992, the prevailing biotype in Imphal changed from Indian biotype 3 to a new biotype 3M. Our data show that biotype 3M belongs to group I and did not arise by a recent mutation from biotype 3, which belongs to group II. By contrast, Indian biotypes 2 and 4 are likely to have diverged through recent mutation and selection, as are Chinese biotypes 1 and 4. The almost simultaneous emergence of new biotypes in Kerala and Sri Lanka during 1985-1988 was most probably coincidental, because these biotypes are not closely related. AFLP fingerprints were also able to detect sexual dimorphism in the DNA of adult gall midges and to distinguish gall midge from its major parasite Platygaster oryzae.

Animals↗
PubMed2000

[Treatment of intrauterine growth retardation with magnesium sulfate].

OBJECTIVE: To study the relationship between magnesium level in umbilical vein and mother's peripheral blood with intrauterine growth retardation (IUGR) and fetal weight. METHODS: 39 pregnant women with IUGR were randomly divided into 3 groups: Group 1 (n = 14): The patients were treated with 10% glucose 500 ml + danshen compound 14 ml + low molecular weight dextran 500 ml i.v.; Group 2 (n = 14): in addition to the same treatment as in group 1, 25% magnesium sulfate 20 ml in 5% glucose 500 ml i.v. was given; Group 3 (n = 11): no treatment was given; and another 12 normal term delivery women were served as control. Magnesium concentration levels were determined in both maternal peripheral blood and their fetal umbilical vein. RESULTS: Maternal serum magnesium level was higher in Group 2 (1.06 +/- 0.09) mmol/L than that in Group 1 (0.69 +/- 0.05) mmol/L (P < 0.05), while there was no significant difference between Group 1 and Group 3. The serum magnesium levels in both mother and fetal umbilical vein of normal pregnancy and of Group 2 were significantly higher than those of Group 1 and 3 (P < 0.01), so did the birth weight of their newborns (P < 0.05). CONCLUSION: Magnesium deficiency might be one of the causes of IUGR, and magnesium sulfate treatment was effective.

Adult↗
PubMed2000

[Effects of permissive hypercapnia on pulmonary mechanics and hemodynamics in sheep with acute lung injury].

OBJECTIVE: To study the effects of permissive hypercapnia (PHC) on pulmonary mechanics and hemodynamics in sheep with acute lung injury (ALI). METHODS: In 18 sheep with LPS induced ALI, gas exchange, pulmonary mechanics and hemodynamics were observed at different tidal volumes (VT). RESULTS: When VT was decreased from 16 ml/kg to 4-7 ml/kg, PHC was induced. Arterial pressure of carbon dioxide increased markedly, arterial oxygen pressure, oxygen saturation and mixed venous oxygen saturation decreased (P < 0.05). Airway pressure decreased significantly (P < 0.05), but the airway resistance increased. Systemic and pulmonary vascular resistance index, right and left ventricular stroke work index increased in PHC, but heart rate decreased (P < 0.05). Compared with VT 16 ml/kg, cardiac index decreased markedly in PHC. In static pressure-volume curve, the pressure of upper inflection point was (21.8 +/- 3.2) cm H2O, volume was (10.7 +/- 1.3) ml/kg. CONCLUSIONS: Alveolar overdistention may be prevented only when airway plateau pressure is less than 20-25 cm H2O, but cardiac index is decreased.

Animals↗
PubMed2000

[Application of microsatellite alteration of urine sediment in the early diagnosis of bladder cancer].

OBJECTIVE: To assess the usefulness of microsatellite DNA sequence (MS) alterations in urine sediment for early diagnosis of human bladder cancer. METHODS: Loss of heterozygosity(LOH) and microsatellite instability(MIN) in urine sediment from 28 cases of bladder cancer were detected by polymerase chain reaction (PCR) with selected primers of 10 microsatellite loci. The peripheral blood mononuclear cells and bladder carcinoma cells were used as controls. RESULTS: In 24 of 28 bladder cancer patients (85.7%) LOH and MIN were found in urine sediment on at least one MS locus. Only in 3 of 28 patients(10.7%) was the urine cytology positive while MS and MIN were detected in these 3 patients. The conformance of MS alterations between cancer cells and urine sediment in the same patients was 94.1%. No MS alteration was found in 15 normal controls. CONCLUSION: Application of microsatellite sequence of urine sediment can be considered as a new tool for screening and early diagnoses of bladder cancer.

Humans↗
PubMed2000

Neuroendocrine differentiation in ovarian mucinous tumors.

OBJECTIVE: To investigate the relationship between neuroendocrine differentiation in ovarian mucinous tumors and its genesis. METHODS: A morphologic study of seventy-three cases of ovarian mucinous tumors (32 benign, 20 borderline, 21 malignant) using immunohistochemical and immunohistochemical/histochemical double staining techniques. RESULTS: The study showed that in tumors of benign, borderline and malignant types, the incidence of chromogranin A (CgA) positive cells was 62.5%, 75%, 76% and that of 5-hydroxytryptamine (5-HT) positive cells was 31.3%, 40% and 39%, respectively. Neuroendocrine cells (NEC) were not evenly distributed in any tumor. In four cases of the benign tumors, the number of CgA positive cells was more than 30 percent, localizing between the glandular basement membrane and the mucinous epithelial cells, with many intermediate cells containing both CgA and periodic acid-schiff (PAS) positive granules. CONCLUSION: The occurrence of both neuroendocrine and exocrine granules within the same cell has been previously described as "intermediate" in pancreatic hyperplasia, pancreatic tumors and lung signet-ring cell carcinoids. This has not previously been observed in benign ovarian mucinous tumors. Finding both endocrine and exocrine granules within a single cell seems to indicate a histogenetic relationship between the ovarian endocrine and exocrine cells. The four cases of the benign tumors might be originated from a common stem cell, such as the so-called amphocrine cell. The relationship between these four tumors and neuroendocrine differentiation in ovarian mucinous tumors needs to be further clarified.

Adenocarcinoma, Mucinous↗
PubMed2000

Hepatocellular adenoma and focal nodular hyperplasia: a series of 24 patients with clinicopathological and radiological correlation.

OBJECTIVE: To investigate two rare benign lesions, hepatocellular adenoma (HCA) and focal nodular hyperplasia (FNH), and evaluate differential diagnosis. METHODS: Twenty-four consecutive patients with presumed HCA and FNH were studied at the Liver Cancer Institute from January 1996 to May 1999. Preoperative assessment included clinical evaluation, symptoms and laboratory tests. New imaging techniques were prospectively appraised in addition to usual techniques. All had hepatic resections and follow-up. Histologic examination of surgical specimens was obtained in all cases. RESULTS: In every instance, FNH was an incidental finding. FNH consists of nodular aggregates of cytologically normal hepatocytes with foci of intranocular bile duct proliferation. In this series, patients with HCA had larger tumors and more often were symptomatic but the occurrence was unrelated to oral contraceptive steroids (OCS) usage. Intralesional hemorrhage or necrosis is common, and was seen in 75% of cases. The best imaging procedure in the diagnosis of FNH was MRI. Color Doppler US was a useful adjunct, but CT lacked specificity, making histological diagnosis mandatory. All patients underwent tumor resected were tumor--free during the follow-up. CONCLUSIONS: FNH is a distinct histopathologic entity, and is distinguishable from HCA. FNH is a hyperplastic response by the liver parenchyma to a pre-existing arterial malformation. HCA is a liver neoplasia and has the potential of malignant transformation to HCC. Based on these findings, we believe that if the clinical suspicion of HCA or FNH is strong, resection is usually the best approach if technically feasible and histologic diagnosis is mandatory.

Adenoma, Liver Cell↗
PubMed2000

[Expression and significance of MMP2 and type IV collagen in gastric cancer].

OBJECTIVE: To evaluate the relationship between the expression of MMP(2), type IV collagen, and invasion and metastasis of gastric cancer. METHODS: The expression of MMP(2) and Type IV collagen was observed by using immunohistochemistry technique. RESULTS: The MMP(2) expression clearly appeared in the poor-differentiated adenocarcinoma and tubular adenocarcinoma (85.7%, 77.7%). Type IV collagen destruction was observed simultaneously. MMP(2) was highly expressed in patients with cancer embolus in blood vessel and lymphatic vessel or with lymph node metastasis (83.3%, 86.7%). CONCLUSIONS: The high expression of MMP(2) was significantly associated with infiltration and metastasis of gastric cancer. The extracellular matrix, especially type IV collagen was destroyed in the cases of high expression of MMP(2). These results suggest that monitoring the level of MMP(2) expression may be an index for evaluation of prognosis.

Adenocarcinoma↗
PubMed2000

[Effect of sodium fluoride on bone turnover and bone loss of vertebrae and tibia in ovariectomized rats].

OBJECTIVE: To investigate the effect of sodium fluoride on bone turnover and bone loss of vertebra and tibia of ovariectomized rats. METHODS: 34 female Wistar rats, 16 weeks old, were divided into 3 groups: sham-ovariectomy (CON), bilateral ovariectomy (OVX) and both OVX and NaF-treatment groups (OVX + NaF, 1.0 mg/kg BW). All of the rats were sacrificed 12 weeks after the treatment. Serum was collected for the analysis of estradiol, calcium, phosphorum and alkaline phosphotase. Temur was used for the analysis of calcium content. Tibiae and the first lumbar vertebral bodies were decalcified for histomorphometry. RESULTS: After treatment with NaF, bone resorption was not inhibited, but bone formation was significantly increased. The trabecular bone volume of vertebrae (18.73% +/- 3.04%) and tibiae (14.30% +/- 5.87%) was significantly increased in comparing with of OVX rats (15.07% +/- 2.45% and 8.81% +/- 2.60%, P < 0.05), but it was markedly lower than that of CON rats (22.44% +/- 1.82% and 24.87% +/- 4.02%, P < 0.05 and P < 0.01). CONCLUSIONS: NaF could not decrease bone turnover and it, has only a partial protective effect against bone loss of either vertebra or tibia.

Animals↗
PubMed2000

[A clinicopathological study of hepatic focal nodular hyperplasia].

OBJECTIVE: To study the clinicopathological features of focal nodular hyperplasia (FNH). METHODS: The clinicopathological characteristics of 25 cases of FNH were studied retrospectively. 20 cases followed for 6 to 47 months. All were evaluated by use of paraffin-embedded sections, special and immunohistochemical staining (EnVision method) and electron microscope. RESULTS: 17 female and 8 male FNH patients aged 14 to 58 (median 38) years of age, all alpha-fetoprotein negative, asymptomatic and normal biochemical liver tests in most cases. The macroscopic hallmark is a central stellate fibrotic scar, composed of fibrous connective tissue and tortuous blood vessels, the fibrous tissue radiated peripherally, dividing the mass into multiple, variably sized nodules, simulating the pattern of cirrhosis. Microscopically, multinodular proliferation of benign-appearing hepatocytes separated by bile-duct-containing fibrous septae that radiate from the central scar. Internodular bile duct proliferation is abundant and merge imperceptibly with the hepatocyte elements near the fibrous septa. Immunohistochemically, the keratin expessed by hepatocytes and by the proliferated bile ducts were similar. Electron microscopic examination found that the ultrastructure of tumor cells were similar to normal hepatocytes. 20 cases were followed for 6-47 months, all survived with no recurrence. CONCLUSION: FNH is a benign hepatocytic lesion, i.e. a reactive proliferation of hepatic cells to local blood vessel anomalies.

Adolescent↗
PubMed2000

[Hyperconjugation, characteristic infrared absorption of methylsulfones and crystal structures of selected aromaticsulfones].

A branched absorption peak with medium intensity at (970 +/- 20) cm-1 appears only in the infrared spectra of methylsulfones. The below mentioned aromaticsulfones are chosen to reveal the specificity. Crystal and molecular parameters of CH3CONH-C6H4-SO2R(R = -CH3, -CH2CH2OH)-CH2CONH2, are determined by application of single crystal diffraction of X-ray through Nicolet R3M/E diffracometer. The existence of hyperconjugation and its natures in group -SO2CH3, confirmed by further analyses on the parameters, result in the specificity of IR absorption of the group, which is proved characteristic and can be used to identify methylsulfones. The first part describes the detection results, ascertains their crystal and molecular structures, and shows that the aromaticsulfone exists as cross linking multi-molecules when R = -CH2CONH2 or as double molecules when R = -CH2CH2OH because of H bonds. The second part covers analyses on their molecular structures. The analyses demonstrate the hyperconjugation between sigma S-C and pi S-C in group -SO2CH3. The sigma C-H hyperconjugate with pi S-O. The strength of hyperconjugated bond C-H decreases and its length tends longer. Due to the effect, the bond S-C is not a pure single bond sigma, but one which possesses a certain degree of a double bond. Its IR wave number, between those of sigma S-C and pi S-C, attributes to the medium branched peak at (970 +/- 20) cm-1. The peak branch reflects two groups of the most stable hyperconjugating conformational isomers. The hyperconjugation is weakened by the substitution of one non H group for one H atom in -SO2CH3 and if the non H group does not conjugate with pi S-O, the absorption at (970 +/- 20) cm-1 disappears as a characteristic peak. The intensity of absorption at (970 +/- 20) cm-1 conforms to the intensity of hyperconjugation between pi S-O and its adjacent sigma C-H. The third part introduces syntheses of the products, crystal preparations and their detections through X-ray diffraction.

English Abstract↗
PubMed1999

p90(RSK) blocks bad-mediated cell death via a protein kinase C-dependent pathway.

Although activation of protein kinase C (PKC) is known to promote cell survival and protect against cell death, the PKC targets and pathways that serve this function have remained elusive. Here we demonstrate that two potent activators of PKC, 12-O-tetradecanoylphorbol-13-acetate and bryostatin, both stimulate phosphorylation of Bad at Ser(112), a site known to regulate apoptotic cell death by interleukin-3. PKC inhibitors but not PI 3-kinase/Akt inhibitors block 12-O-tetradecanoylphorbol-13-acetate-stimulated Bad phosphorylation. PKC isoforms tested in vitro were unable to phosphorylate Bad at Ser(112), suggesting that PKC acts indirectly to activate a downstream Bad kinase. p90(RSK) and family members RSK-2 and RSK-3 are activated by phorbol ester and phosphorylate Bad at Ser(112) both in vitro and in vivo. p90(RSK) stimulates binding of Bad to 14-3-3 and blocks Bad-mediated cell death in a Ser(112)-dependent manner. These findings suggest that p90(RSK) can function in a PKC-dependent pathway to promote cell survival via phosphorylation and inactivation of Bad-mediated cell death.

Animals↗