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Biomedical subjects

T Yang

Publications and source records attributed to T Yang.

At least 199 records · Page 11Linked to original sources
PubMed1997

The selective recognition of antibody IgY for digestive system cancers.

Biological methods for cancer therapies are very important. A small and efficient target carrier is the key component for anti-cancer drugs. In our laboratory, the antibody IgY was extracted from egg yolk of a SPF hen. The SPF hen was immunized with an antigene of P110 protein which was purified from human stomach cancer MGC-803 cells. Results indicated that the antibody IgY can specifically recognize gastrointestinal system cancers. It may become an important carrier for antitumorigenic drugs.

Adenocarcinoma↗
PubMed1997

Variations in the use of prostate cancer staging tests: results from one NCCN Institution.

Medical care for prostate cancer accounts for as much as $26 billion in medical expenditures. There is debate about whether urologists who treat a large number of cases of prostate cancer use medical resources more efficiently than do urologists who treat fewer patients. This study focuses on one aspect of this debate by addressing the following issue: Are men with prostate cancer more likely to undergo noninvasive staging tests when they are treated by urologists who have higher caseloads than urologists with lower caseloads? Our study identified variations in patterns of ordering staging tests for prostate cancer. The finding supports the use of guidelines. Adherence to the guidelines is likely to be associated with more efficient use of medical resources by physicians with lower caseloads of prostate cancer.

Data Interpretation, Statistical↗
PubMed1997

[Three-dimensional reconstruction of sinusoids from serial sections].

The three-dimensional image of sinusoids has been reconstructed by computer image processing using a new method of registration. By observing the reconstructed image of sinusoids, we can easily understand the anatomy of sinusoids. Theoretical analysis and experimental results suggest that the method is feasible and practicable.

Animals↗
PubMed1997

[The effect of phenytoin in healing of fracture of rabbits].

It was reported that the systemic use of phenytoin could promote healing of fracture. In order to observe the effect of local application of phenytoin in the healing of fracture, the experiment was performed. Seventy-two rabbits were divided into three groups. Fractures were created on both radius of all rabbits. Group 1, intraperitoneal injection of phenytoin with a dosage of 50 mg/kg per day; Group 2, local use of phenytoin with a dosage of 40 mg/kg was injected in the fracture site every seventy-two hours, and Group 3, injection mormal saline of in the control group. Eight rabbits in each group were sacrificed in the 9th, 16th and 30th days after operation respectively. By X-ray excuiualtion, the healing of fracture was observed. Dry and wet weights of the callus were determined. After HE and Mallory's stain, the samples were examined under microscope. Results showed that both local and systemic use of phenytoin promoted healing of fracture. The effects of phenytoin in the two groups were the same and had no significant difference.

Animals↗
PubMed1996

Mapping cross-linking sites in modified proteins with mass spectrometry: an application to cross-linked hemoglobins.

The combined use of trypsin digestion and peptide mass mapping by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is reported here as an effective and rapid means for identifying the cross-linking sites in human oxy hemoglobin A (HbA) cross-linked with either bis(3,5-dibromosalicyl)-succinate or -glutarate. MALDI-MS analysis of a nondigested sample of oxy HbA modified with bis(3,5-dibromosalicyl)-glutarate showed that cross-linking only occurred between the beta 1- and beta 2-protomers and not between alpha 1- and alpha 2- or alpha- and beta-protomers, along with a modification reaction on an un-cross-linked beta-chain. Results of the MALDI tryptic peptide mass maps of cross-linked hemoglobins showed several cross-linked peptides having masses consistent with: beta Val67-Lys95-XL-beta Val67-Lys95, beta Val67-Lys95-XL-beta Val67-Arg104, beta Val67-Arg104-XL-beta Val67-Arg104, where XL represents the succinyl or glutaryl bridging span moiety. Each of these peptides contains Lys82, the targeted residue for these reagents, substantiating the cross-linking sites at beta 1Lys82-beta 2Lys82. This approach in general will enable rapid identification of the cross-linking sites in engineered proteins or intracellularly recombinant cross-linked proteins when the mass of the cross-linker and the protein primary structure are known.

Amino Acid Sequence↗
PubMed1996

Characterization of the calmodulin gene family in wheat: structure, chromosomal location, and evolutionary aspects.

Calmodulin is a ubiquitous transducer of calcium signals in eukaryotes. In diploid plant species, several isoforms of calmodulin have been described. Here, we report on the isolation and characterization of calmodulin cDNAs corresponding to 10 genes from hexaploid (bread) wheat (Triticum aestivum). These genes encode three distinct calmodulin isoforms; one isoform is novel in that it lacks a conserved calcium binding site. Based on their nucleotide sequences, the 10 cDNAs were classified into four subfamilies. Using subfamily-specific DNA probes, calmodulin genes were identified and the chromosomal location of each subfamily was determined by Southern analysis of selected aneuploid lines. The data suggest that hexaploid wheat possesses at least 13 calmodulin-related genes. Subfamilies 1 and 2 were both localized to the short arms of homoeologous-group 3 chromosomes; subfamily 2 is located on all three homoeologous short arms (3AS, 3BS and 3DS), whereas subfamily 1 is located only on 3AS and 3BS but not on 3DS. Further analysis revealed that Aegilops tauschii, the presumed diploid donor of the D-genome of hexaploid wheat, lacks a subfamily-1 calmodulin gene homologue, whereas diploid species related to the progenitors of the A and B genomes do contain such genes. Subfamily 3 was localized to the short arm of homoeologous chromosomes 2A, 2B and 2D, and subfamily 4 was mapped to the proximal regions of 4AS, 4BL and 4DL. These findings suggest that the calmodulin genes within each subfamily in hexaploid wheat represent homoeoallelic loci. Furthermore, they also suggest that calmodulin genes diversified into subfamilies before speciation of Triticum and Aegilops diploid species.

Amino Acid Sequence↗
PubMed1996

Blood lead levels in Taiwanese adults: distribution and influencing factors.

Five-thousand nine-hundred thirteen Taiwanese adults were selected by multistage sampling methods to investigate environmental lead exposure in Taiwan. The blood specimens were distributed to six laboratories for blood lead levels (BLL) measurement. The mean BLL of the 5913 Taiwanese adults was 8.28 +/- 5.39 microg/dl, with a maximum level of 57.6 microg/dl. The median was 7.0 microg/dl and 90th percentile was 15.0 microg/dl. BLLs were associated with gender, ethnic group, education level, smoking, alcohol consumption, herbal drug consumption, milk consumption, sources of drinking water, level of urbanization, and occupational lead exposure. These results showed that BLLs in Taiwanese adults were stable during the 2-year study. Most of the influencing factors were consistent with other studies, while local risk factors, such as Chinese herbal drug consumption are important ways of preventing the general population from overexposure to lead.

Adolescent↗
PubMed1996

Extracellular potassium modulation of drug block of IKr. Implications for torsade de pointes and reverse use-dependence.

BACKGROUND: Torsade de pointes often occurs with underlying hypokalemia and bradycardia. A common effect of many drugs producing torsade de pointes is block of the rapidly activating component of the cardiac delayed rectifier (IKr). In this study, we evaluated the effect of changing extracellular potassium ([K+]o) on IKr block by the nonspecific agent quinidine and by the specific IKr blocker dofetilide. METHODS AND RESULTS: IKr was measured in AT-1 cells, where contaminating outward currents are absent. The drug concentration producing 50% inhibition of IKr tails (IC50) was strikingly [K+]o-dependent. Elevating [K+]o from 1 to 8 mmol/L increased the IC50 for dofetilide block from 2.7 +/- 0.9 to 79 +/- 32 nmol/L and for quinidine block from 0.4 +/- 0.1 to 3.8 +/- 1.2 mumol/L. CONCLUSIONS: (1) The increase in drug block with low [K+]o provides a mechanism to explain the link between hypokalemia and torsade de pointes. (2) Elevations in [K+]o occur with myocardial ischemia and with rapid pacing. Possible consequences of blunted drug block with high [K+]o include loss of drug efficacy with ischemia and with rapid pacing; the latter may contribute to "reverse use-dependent" action potential prolongation. Extracellular potassium is a critical determinant of drug block of IKr, with substantial clinical implications.

Animals↗
PubMed1996

MCL-1, a member of the BLC-2 family, is induced rapidly in response to signals for cell differentiation or death, but not to signals for cell proliferation.

mcl-1 was identified as an "early-induction" gene that increases in expression during the differentiation of ML-1 human myeloblastic leukemia cells. The mcl-1 gene product proved to be a member of the bcl-2 gene family and, like bcl-2, to have the capacity to promote cell viability. The pattern of expression of mcl-1 has now been characterized, the aim being to determine whether increased expression is consistently associated with differentiation-induction and whether expression is also associated with other changes in proliferative state or cell viability. Expression of the mcl-1 mRNA was found to increase rapidly in ML-1 cells exposed to inducers of monocyte/macrophage differentiation (phorbol esters or lymphocyte conditioned medium), but not cells exposed to an inducer of granulocyte differentiation (retinoic acid). Expression also increased rapidly in response to certain cytotoxic agents (colchicine and vinblastine), but did not increase during serum stimulation or growth-arrest in reduced serum. Increased expression of mcl-1 occurred during the initiation of cell differentiation or death and was not inhibited by cycloheximide, in agreement with the designation of mcl-1 as an early-induction gene. Increased transcription contributed to the increase in expression, and turnover of the mcl-1 mRNA was rapid. These findings suggest that mcl-1 may serve as a modulator of cell viability that can undergo rapid upregulation as well as downregulation, with upregulation harbingering the initiation of cell differentiation or death.

Base Sequence↗
PubMed1996

Specific replacement of consecutive AGG codons results in high-level expression of human cardiac troponin T in Escherichia coli.

The adult isoform of human cardiac troponin T (TnT) contains 288 amino acids, 14 of which (4.9%) are encoded by the rarely used arginine codons (12 AGG, 2 AGA) in Escherichia coli genes. To generate sufficient quantity of TnT protein for antibody production, we cloned the corresponding cDNA and expressed it in E. coli. A low-level expression of TnT that comprised only about 1% of total cell protein was initially observed with the use of the native cDNA. The existence of two pairs of consecutive AGG codons AGG(165) AGG(166) and AGG(215) AGG(216) in the cDNA was suspected to be the main cause for this low-level expression. These two pairs of consecutive AGG codons were successively replaced with the major synonymous codon CGT by site-directed mutagenesis. As suspected, a 10-fold increase in TnT expression was obtained when one pair of the rare arginine codons was replaced and a 40-fold increase was achieved when both pairs of the rare codons were replaced. Our finding demonstrates the importance of consecutive rare codons in the suppression of high-level expression of heterologous proteins in E. coli and suggests that in order to maximize protein expression, a similar approach may be taken with other genes which contain consecutive rare codons.

Adult↗
PubMed1996

Three-year survey of blood lead levels in 8828 Taiwanese adults.

The purpose of this study was to investigate environmental lead exposure in the general Taiwanese population. A total of 8828 Taiwanese adults selected by a multistage sampling method were investigated. Characteristics of the participants were ascertained by questionnaire and 10 ml venous blood was drawn by public health nurses. The blood specimens were distributed to six laboratories for blood lead level (BLL) measurement. A quality control program was applied during the analysis of the BLLs in order to improve precision and accuracy. The arithmetic mean BLL of the 8828 Taiwanese adults was 7.70 +/- 5.23 micrograms/dl, with a maximal level of 69.1 micrograms/dl. The median was 6.5 micrograms/dl and the 90th percentile was 14.0 micrograms/dl. After logarithmic transformation, the geometric mean was 1.84 +/- 0.67 microgram/dl. This study also found that elevated BLLs were associated with certain personal characteristics, i.e., gender, ethnic group, and education level; life-style factors, such as smoking, alcohol consumption, Chinese herbal drug consumption, milk consumption, and sources of drinking water; residential location, i.e., level of urbanization; and occupational history of lead exposure. However, age, floor level of residence, distance from house to road, and betel nut consumption were not associated with elevated BLLs. These results showed that BLLs in the Taiwanese population were not higher than those in developed and developing countries. Most of the influencing factors were also found in other studies; however, local factors such as ethnic group, Chinese herbal drug consumption, and sources of drinking water are important considerations in Taiwan when examining ways to prevent overexposure to lead in the general population.

Adult↗
PubMed1996

Genetic correlates of in vivo viral resistance to indinavir, a human immunodeficiency virus type 1 protease inhibitor.

Indinavir (IDV) (also called CRIXIVAN, MK-639, or L-735,524) is a potent and selective inhibitor of the human immunodeficiency virus type 1 (HIV-1) protease. During early clinical trials, in which patients initiated therapy with suboptimal dosages of IDV, we monitored the emergence of viral resistance to the inhibitor by genotypic and phenotypic characterization of primary HIV-1 isolates. Development of resistance coincided with variable patterns of multiple substitutions among at least 11 protease amino acid residues. No single substitution was present in all resistant isolates, indicating that resistance evolves through multiple genetic pathways. Despite this complexity, all of 29 resistant isolates tested exhibited alteration of residues M-46 (to I or L) and/or V-82 (to A, F, or T), suggesting that screening of these residues may be useful in predicting the emergence of resistance. We also extended our previous finding that IDV-resistant viral variants exhibit various patterns of cross-resistance to a diverse panel of HIV-1 protease inhibitors. Finally, we noted an association between the number of protease amino acid substitutions and the observed level of IDV resistance. No single substitution or pair of substitutions tested gave rise to measurable viral resistance to IDV. The evolution of this resistance was found to be cumulative, indicating the need for ongoing viral replication in this process. These observations strongly suggest that therapy should be initiated with the most efficacious regimen available, both to suppress viral spread and to inhibit the replication that is required for the evolution of resistance.

Base Sequence↗
PubMed1996

Na-K-ATPase in lacrimal gland acinar cell endosomal system: correcting a case of mistaken identity.

Na-K-ATPase is associated with a variety of membrane populations in lacrimal acinar cells. Acinus-like structures formed by rabbit acinar cells in primary culture were incubated with horseradish peroxidase (HRP) to label basolateral and endosomal membranes and then analyzed by electron microscopy cytochemistry with the 3-3'-diaminobenzidine reaction or by fractionation and measurement of marker catalytic activities or immunoreactivities. HRP adsorbed to basolateral membranes at 4 degrees C. Fractionation showed it associated with low-density membranes enriched in acid phosphatase and TGN38 but containing only minor amounts of Na-K-ATPase. Cells internalized HRP to cytoplasmic vesicles, Golgi structures, and lysosomes at 37 degrees C. The major endosomal compartment revealed by fractionation coincided with major peaks of Na-K-ATPase and Rab6 and secondary peaks of galactosyltransferase and gamma-adaptin. Carbachol (10 microM) increased lysosomal and Golgi labeling. Thus most of the Na-K-ATPase is located in the basolateral membrane-oriented endosomal system, concentrated in a compartment possibly related to the trans-Golgi network. Constitutive and stimulation-accelerated traffic to and from this compartment may serve several exocrine cell functions.

Animals↗
PubMed1996

Regulation of sodium current development in cultured atrial tumor myocytes (AT-1 cells).

AT-1 cells, derived from atrial tumors in transgenic mice, have many features similar to cardiac myocytes. However, their sodium current (INa) has not been evaluated on detail. In this study, two INa phenotypes were identified in AT-1 cells: one at 3 days in culture and the other at 14 days. INa was smaller at 3 days than at 14 days (12 +/- 2 vs. 37 +/- 5 pA/pF) and activated more slowly (time to peak INa at -30 mV: 9.8 +/- 0.4 vs. 1.4 +/- 0.1 ms). Inactivation at 14 days was faster and shifted 16 mV negative compared with that at 3 days. Acute protein kinase A or C stimulation in 3-day cells did not alter INa gating. However, the 14-day phenotype was observed in 3-day cells when the adenosine 3',5'-cyclic monophosphate analogue 8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate, the phorbol ester phorbol 12-myristate 13-acetate, or okadaic acid was added to the culture medium from days 0 to 3. Conversely, adenosine 3',5'-cyclic monophosphothioate triethylamine, the protein kinase A inhibitor, prevented the normal development of the 14-day phenotype if the exposure was early and reverted the phenotype to that at 3 days if the exposure was later. Thus, in AT-1 cells, as in other mammalian cardiac myocytes, INa undergoes a maturation process that is dependent on intracellular phosphorylation processes. The data raise the possibility that an important consequence of altered intracellular signaling in disease is lability in INa amplitude or gating.

Animals↗
PubMed1996

Coordinate regulation of renal expression of nitric oxide synthase, renin, and angiotensinogen mRNA by dietary salt.

Experiments were performed to examine the effect of changes in dietary salt intake on the neuronal form of the constitutive nitric oxide synthase (ncNOS, type I NOS), renin, and angiotensinogen mRNA expression in the kidney. Three groups of Sprague-Dawley rats were studied as follows: rats maintained on a 3% Na diet plus 0.45% NaCl in the drinking fluid for 7 days (high salt), rats given a single injection of furosemide (2 mg/kg i.p.) and a 0.03% Na diet for 7 days (low salt), and rats on a diet containing 0.2% Na (control). mRNA expression was assessed with reverse transcription-polymerase chain reaction (RT-PCR) methods using cDNA prepared from samples of renal cortex and microdissected tubular segments. ncNOS PCR products were quantified by comparison with a dilution series of a mutant deletion template. Compared with their respective control, ncNOS mRNA levels in renal cortical tissue were elevated in rats on a low-salt diet and reduced in rats on a high-salt diet. Similar changes were seen in the expression of renin and angiotensinogen mRNA. Dietary salt intake did not alter the mRNA levels for ncNOS from the inner medulla or for endothelial constitutive NOS (ecNOS, type III NOS) and inducible NOS (iNOS, type II NOS) in the renal cortex. ncNOS mRNA was found in glomeruli dissected with the macula densa-containing segment (MDCS), but only at marginal levels in glomeruli without MDCS. Furthermore, a low-salt diet stimulated ncNOS mRNA in glomeruli with MDCS by 6.2-fold compared with a high-salt diet. There was no effect of salt diet on ncNOS mRNA in glomeruli without MDCS or in inner medullary collecting ducts. These results suggest that ncNOS expression in macula densa cells is inversely regulated by salt intake, thus following the known response of the renin-angiotensin system to changes in salt balance.

Angiotensinogen↗
PubMed1996

Localization of bumetanide- and thiazide-sensitive Na-K-Cl cotransporters along the rat nephron.

The present study was undertaken to investigate the mRNA localization of the two major kidney-specific Na-K-Cl transport proteins, the bumetanide-sensitive cotransporter (NKCC2 in rabbit and BSC1 in rat) and the thiazide-sensitive cotransporter (TSC). NKCC2 from rabbit and mouse has been shown to exist in three isoforms (designated A, B, and F) that differ only in a 96-bp region. The divergent region of each of the three NKCC2 isoforms was cloned from rat kidney by a polymerase chain reaction (PCR)-based strategy, and isoform-specific primers were chosen. RNA and cDNA were prepared from renal cortex and medulla and from microdissected nephron segments. Using reverse transcription (RT)-PCR, the B isoform was detected only in cortex and the F isoform only in medulla, whereas the A from was found in both. In dissected nephron segments, the B form was found exclusively in cortical thick ascending limb (CTAL) and macula densa-containing segment (MDCS), the F form only in medullary thick ascending limb (MTAL) and outer medullary collecting duct, and the A form in CTAL, MDCS, and MTAL. An additional isoform including both A and F exons was identified by direct sequencing of a 592-bp product from medulla. The AF product was found only in the medulla and was localized exclusively in MTAL. TSC mRNA was detected exclusively in the distal convoluted tubule. Differential nephron localization of NKCC2 isoforms suggests that Na-K-Cl cotransporters may differ in their transport characteristics to explain regulation of salt transport along the nephron.

Animals↗