Biomedical subjects

C H Yang

Publications and source records attributed to C H Yang.

At least 109 records · Page 6Linked to original sources

PubMed1998

Homozygous deletions of the CDKN2 gene and loss of heterozygosity of 9p in primary hepatocellular carcinoma.

To elucidate the alterations of CDKN2 in hepatocarcinogenesis, we performed a loss of heterozygosity (LOH) study using eight polymorphic markers surrounding the CDKN2 gene and analyzed the homozygous deletions and mutations of the CDKN2 gene in 41 primary hepatocellular carcinomas (HCCs). Frequent LOH (27.8-44%) was found in the eight loci on chromosome 9p, however, no intragenic mutations of CDKN2 were observed by PCR-SSCP analysis. Homozygous deletions were detected in 25 of 41 HCCs (61%) by a comparative multiplex PCR. No expression of the CDKN2 protein was noted in five out of nine available HCCs by Western blot analysis. These results suggest that inactivation of the CDKN2 gene in HCC is a frequent event in which homozygous deletions are the most common mechanism of CDKN2 inactivation.

Carcinoma, Hepatocellular↗

PubMed1998

Serological characterization of the 3'-proximal encoded proteins of beet yellows closterovirus.

The 3'-proximal open reading frames (ORFs) of beet yellows closterovirus, California isolate (BYV-CA), were sequenced and the expression of the corresponding proteins analyzed. The nucleotide sequence of ORF 5 (coding for p24) was most conserved compared with ORF 7 (coding for p20) and ORF 8 (coding for p21) among the isolates analyzed. Polyclonal antisera were produced to GST fusion proteins of p24, p20, and p21. Accumulation of p24, CP, p20 and p21 was studied in infected Tetragonia expansa plants and Chenopodium quinoa protoplasts. All four proteins were expressed in all tissues (old leaves, young leaves and stems), and most abundantly in young leaves. The subcellular localization of each protein in different tissues showed that compared with p24, CP and p21, p20 accumulated less in transfected protoplasts. Immunogold labeling in sugarbeet with p24 and CP antisera demonstrated co-localization of p24 and CP in vascular petiole tissues. In infectivity neutralization tests, antisera against p24 and CP greatly reduced transmission of BYV by viruliferous aphids compared with viruliferous aphids fed on preimmune serum or antiserum to p21.

Amino Acid Sequence↗

PubMed1998

Chromosomal localization of the murine RFC-1 gene encoding a folate transporter and its amplification in an antifolate resistant variant overproducing the transporter.

A variant of the L1210 cell (L1210/R83) selected in the presence of the lipophilic antifolate, metoprine, and a concentration of the natural diastereoisomer of 5-formyltetrahydrofolate, lL5CHO-folateH4, suboptimum for growth exhibited a 35-fold increase compared to parental L1210 cells in one-carbon, reduced folate transport. This was evidenced by the increase in Vmax for [3H]MTX (methotrexate) influx and a commensurate increase in the amount of the 46 kilodalton (kDa) transport protein and reduced folate carrier (RFC-1) mRNA. The variant is resistant to lipophilic antifolates, but shows collateral sensitivity to classical folate analogues. Karyotype analysis of L1210/R83 cells revealed the presence of several new chromosome abnormalities. One of these was a large, submetacentric marker chromosome comprising a normal #10 and a longer, abnormally banded arm of uncertain origin which exhibited an interstitial, palely staining, HSR-like segment. The results of Southern and Northern blotting showed that the RFC-1 gene copy number and RNA transcript level were markedly increased (30-35 fold) in L1210/R83 cells. Fluorescence in situ hybridization (FISH) analysis revealed that the HSR-like segment in these cells was the site of amplified RFC-1 genes. Independent revertant subclones, obtained following growth in the absence of selection pressure, showed four- to 12-fold decreases in [3H]MTX influx Vmax and in amount of NHS (N-hydroxysuccinimide)-[3H]MTX affinity labeled one-carbon, reduced folate transporter compared to L1210/R83 cells. RFC-1 gene copy number also decreased, and the mean length of the HSR in these revertants declined 1.6- to 5-fold. Based upon genomic nucleotide sequencing, the RFC-1 gene in the normal mouse genome was localized to chromosome 10 in close association with the alpha 1 (Col18a1) collagen gene at 10B3(locus 41cM). The close association of these genes was confirmed by other data showing that the alpha 1 collagen gene was co-amplified in L1210/R83 cells. These results document the amplification at the site of a putative HSR in an L1210 cell variant of the RFC-1 gene regulating expression of the one-carbon, reduced folate transporter.

Animals↗

PubMed1998

Striatal dopamine dynamics are altered following an intranigral infusion of iron in adult rats.

In vivo electrochemical detection was employed to examine iron-induced oxidative injury on dopamine dynamics in the nigrostriatal system of urethane-anesthetized rats. Seven days after an intranigral infusion of iron, oxidative stress was confirmed by an elevated lipid peroxidation in lesioned substantia nigra (SN). Local application of potassium (K+) evoked dopamine releases from the dopamine-containing nerve terminals in the striatum. Both amplitude and rate of clearance (Tc) of evoked dopamine releases were lower in striatum with lesioned SN; however, the time course parameters of dopamine release in the lesioned group were not different from those of the intact group, indicating a reduction in dopamine clearance. Indeed, iron-induced oxidative stress attenuated the effect of nomifensine, a high-affinity dopamine uptake blocker, on dopamine clearance. In striatum with intact SN, the amplitude and time course parameters of signals by exogenous dopamine were increased and Tc was decreased by nomifensine. In contrast, nomifensine did not significantly alter the dopamine signals of the lesioned group. Taken together, in addition to the increased lipid peroxidation in SN, our in vivo electrochemical data demonstrates that iron-induced oxidative injury attenuates K+-evoked dopamine release and dopamine uptake in the ipsilateral striatum. The diminished nomifensine effect implies a lack of high-affinity dopamine uptake sites.

Animals↗

PubMed1998

A possible hydrolysis mechanism of beta-naphthyl acetate catalyzed by antibodies.

The mechanism of ester hydrolysis has been extensively studied; however, the precise function of active-site residues in promoting catalysis is unclear. We describe here the structural models for the complex of a catalytic antibody Fv fragment with a phosphonate transition-state analogue, constructed by using gene cloning, sequencing and molecular modeling, mainly based on a known X-ray structure of a catalytic antibody. Hydrophobic and electrostatic analyses of the Fv/analog and Fv/substrate interaction suggest the hydrolysis mechanism: Tyr L91 and Tyr H97 play important roles to stabilize the beta-naphthyl group of hapten through pi-stack; His H35 donates a pair of free electrons at the atom NE2 to an active water and let it to be a partial hydroxide, which attacks the carbon atom of the carbonyl group of the substrate. Both His H35 and Arg L96 can form hydrogen bonds and stabilize the anionic tetrahedral intermediate formed during turnover. This mechanism emphasizes that an active water bridge may be formed during hydrolysis process.

Amino Acid Sequence↗

PubMed1998

The kinetics of IL-4 and IFN-gamma gene expression in mice after Trichosansin immunization.

Trichosanthin (TCS) is a potent allergen to mice. According to our previous experiments, it could bring out the IgE response to ovabumin (OVA) if TCS was given one day before OVA immunization, while OVA alone could not induce IgE to it. In this work, the kinetics of interleukin 4(IL-4) and interferon gamma(IFN-gamma) gene expression in the mesenteric lymph node (MLN) of TCS-immunized mice was investigated using a semi-quantitative RT-PCR method. It indicated that TCS induced significant IL-4 gene expression and the peaks of IL4 gene expression were on day one after TCS immunization in both primary and secondary response. In contrast, the IFN-gamma gene expression was suppressed. Furthermore, the IL-4 gene expression in the secondary response was lower than that in the primary response. Thus the presence of IgE memory B cells were studied. Results showed that the amount of mature IgE mRNA arose significantly and rapidly one day after TCS restimulation, while in the MLN of the mice primed 30 days before and without boost, it was almost as the same amount of the unimmunized control. These findings suggest the existence of the IgE memory B cells in the mice after the primary TCS immunization.

Animals↗

PubMed1998

Crystal structure of a novel human peroxidase enzyme at 2.0 A resolution.

Hydrogen peroxide (H2O2) has been implicated recently as an intracellular messenger that affects cellular processes including protein phosphorylation, transcription and apoptosis. A set of novel peroxidases, named peroxiredoxins (Prx), regulate the intracellular concentration of H2O2 by reducing it in the presence of an appropriate electron donor. The crystal structure of a human Prx enzyme, hORF6, reveals that the protein contains two discrete domains and forms a dimer. The N-terminal domain has a thioredoxin fold and the C-terminal domain is used for dimerization. The active site cysteine (Cys 47), which exists as cysteine-sulfenic acid in the crystal, is located at the bottom of a relatively narrow pocket. The positively charged environment surrounding Cys 47 accounts for the peroxidase activity of the enzyme, which contains no redox cofactors.

Binding Sites↗

PubMed1998

FLD interacts with genes that affect different developmental phase transitions to regulate Arabidopsis shoot development.

A new fld mutant allele, fld-2, which significantly delayed flowering, was isolated and characterized in Arabidopsis thaliana. Even under long-day conditions after more than 100 days in the greenhouse, the majority of fld-2 mutant plants had not bolted. In addition, mutant inflorescences produced more than 10 co-florescences that were subtended by a high number of rosette-like leaves before giving rise to flowers. The late-flowering phenotype of the fld-2 mutation could be partially overcome by both vernalization and GA treatment but it was not influenced by 5-azaC treatment. Phenotypic analyses of double mutants indicated that fld-2 is epistatic to early flowering mutants elf1, elf2 and elf3. In addition, fld-2 could enhance vegetative characteristics in embryonic flower 1 (emf1) mutants by causing many small sessile leaves in fld-2 emf1 double mutants. The relief of the terminal flower 1 (tfl1) mutant phenotype in fld-2 tfl1 double mutants, and the enhancement of leafy (lfy) and apetala1 (ap1) mutant phenotypes in fld-2 lfy and fld-2 ap1 double mutants, suggest that FLD is also likely to be involved in the floral transition. Our results strongly suggest that the FLD gene plays a key role in regulating the reproductive competence of the shoot and results in different developmental phase transitions in Arabidopsis.

Arabidopsis↗

PubMed1998

EMF genes interact with late-flowering genes to regulate Arabidopsis shoot development.

To investigate the genetic mechanisms regulating the transition from vegetative to reproductive phase in Arabidopsis, double mutants between two embryonic flower (emf) and 12 different late-flowering mutants were constructed and analyzed. Double mutants in all combinations displayed the emf phenotypes without forming rosettes during early development; however, clear variations between different double mutants were observed during late development. fwa significantly enhanced the vegetative property of both emf mutants by producing a high number of sessile leaves without any further reproductive growth in emf1 fwa double mutants. It also produced numerous leaf-like flower structures similar to those in leafy ap1 double mutant in emf2 fwa double mutants. Nine late-flowering mutants, ft, fca, ld, fd, fpa, fe, fy, fha, and fve, caused different degrees of increase in the number of sessile leaves, the size of inflorescence, and the number of flowers only in weak emf1 and emf2 mutant alleles background. Two late-flowering mutants, co and gi, however, had no effect on either emf1 and emf2 mutant alleles in double mutants. Our results suggest that FWA function in distinct pathways from both EMF genes to regulate flower competence by activating genes which specify floral meristem identity. CO and GI negatively regulate both EMF genes, whereas the other nine late-flowering genes may interact with EMF genes directly or indirectly to regulate shoot maturation in Arabidopsis.

Alleles↗

PubMed1998

Effects of outlet obstruction and its reversal on mitochondrial enzyme activity in rabbit urinary bladders.

PURPOSE: This study investigated the effects of outlet obstruction and its reversal on mitochondrial enzyme activity in the rabbit urinary bladder. MATERIALS AND METHODS: We induced mild bladder outlet obstruction in male New Zealand White rabbits. Following two weeks of obstruction, one group of animals (n = 6) was sacrificed, while outlet obstruction was relieved in three additional groups of animals, which were sacrificed one (n = 5), two (n = 5) and four (n = 5) weeks after relieving the obstruction. Seven sham operated rabbits served as controls. We extracted mitochondria from fresh detrusor and assayed activities of key mitochondrial enzymes in the citric acid cycle, citrate synthase and malate dehydrogenase, as well as those in the electron transport chain, succinate cytochrome c reductase, NADH-cytochrome c reductase and cytochrome c oxidase. With high performance liquid chromatography (HPLC) we determined the tissue content of phosphocreatine and the adenine nucleotides (ATP, ADP and AMP), which was used for calculating energy charge. Responses of detrusor strips to 500 microM bethanechol and 120 mM KCl provided the assessment of detrusor contractility. RESULTS: Contractile response of the detrusor strips to bethanechol stimulation was significantly reduced by outlet obstruction, nevertheless, it recovered gradually toward the control level after the relief of outlet obstruction. Outlet obstruction reduced the detrusor content of phosphocreatine, ATP and energy charge. After relieving the obstruction, however, these recovered gradually, reaching control levels 4 weeks later. The activities of all assayed enzymes were reduced by two weeks of outlet obstruction. Relieving the obstruction restored enzyme activity gradually but at different rates for different enzymes. Activities of the citric acid cycle enzymes citrate synthase and malate dehydrogenase recovered and were similar to control levels four weeks after relief of the obstruction. Of the enzymes in the electron transport chain, NADH cytochrome reductase activity recovered most quickly by one week after relief of the obstruction. The activity of cytochrome c oxidase improved more slowly, but 4 weeks after relieving the obstruction it, also, was restored and was similar to the control level. Succinate cytochrome reductase activity remained lower than the control over the entire four weeks of recovery. CONCLUSIONS: The close association between mitochondrial enzyme activity, energy metabolism and contractility of the detrusor indicates the important role of mitochondrial enzyme damage in decreasing energy production and impairing contractile function of the urinary bladders following outlet obstruction. Our findings also show that various mitochondrial enzymes exhibit different susceptibilities and reversibilities to pathological stress.

Adenine Nucleotides↗

PubMed1998

Recovery of microvascular blood perfusion and energy metabolism of the obstructed rabbit urinary bladder after relieving outlet obstruction.

We investigated the changes in urinary bladder microvascular blood perfusion and energy metabolism following outlet obstruction and after relieving the obstruction. We induced mild bladder outlet obstruction in male New Zealand White rabbits. Following 2 weeks of obstruction, one group of animals (n = 6) was sacrificed, while outlet obstruction was relieved in three additional groups, which were sacrificed 1 (n = 5), 2 (n = 5) and 4 (n = 5) weeks after relieving the obstruction. Seven sham-operated rabbits served as controls. Before obstruction, immediately before relieving the obstruction and preceding the sacrifice, the microvascular blood perfusion of the urinary bladder was measured using a laser Doppler blood flowmeter. The detrusor content of phosphocreatine and adenine nucleotides was determined by high-performance liquid chromatography. The results showed: (1) 2 weeks of outlet obstruction significantly decreased the bladder microvascular blood perfusion, which recovered gradually after relief of the obstruction and returned to the control level by 4 weeks of obstruction reversal; (2) outlet obstruction reduced detrusor energy charge and phosphocreatine content, which were restored in parallel after relieving the obstruction; by 4 weeks the bladder had regained their normal energy producing capability; (3) bladder microvascular perfusion has a very close correlation with detrusor energy charge (r = 0.791, p < 0.001). In conclusion, our findings of the close correlation between microvascular perfusion and energy production in bladder outlet obstruction suggest an important role for the decreased microvascular blood perfusion in reducing bladder energy production.

Adenine Nucleotides↗

PubMed1998

Mortality in geriatric psychiatric inpatients.

OBJECTIVE: This study investigated the deaths of patients sixty-five and older on a psychiatric ward to determine the mortality rate, the characteristics of illness, and the cause of death. METHODS: We analyzed the case record of patients sixty-five and older who had died during hospitalization on a psychiatric ward during a seventeen-year period. Case data was collected by review of chart records. RESULTS: The mortality rate in the patients sixty-five and older was 18/1208 (1.5%). Eight of these eighteen patients died of pneumonia. Mortality in the acutely ill geropsychiatric inpatients was difficult to predict. Age, sex, and diagnosis did not predict mortality. CONCLUSIONS: To reduce mortality, especially in male veterans, management of geropsychiatric patients should include early recognition of pneumonia symptoms, especially for patients with history of pulmonary disease.

Aged↗

PubMed1998

Adaptive Morse code recognition using variable degree variable step size LMS for persons with disabilities.

In this paper, we applied variable degree, variable step size LMS algorithm to adaptive Morse code recognition for persons with impaired hand coordination and dexterity. The automatic recognition of Morse code by the disabled is difficult because they cannot maintain a stable typing rate. Therefore, a suitable adaptive automatic recognition method is needed. In this adaptive Morse code recognition method, three processes are involved: character separation, character recognition, and adaptive processing. Statistical analyses demonstrated that the proposed method resulted in a better recognition rate compared to alternative methods from the literature.

Adolescent↗

PubMed1998

Softened endothracheal tube reduces the incidence and severity of epistaxis following nasotracheal intubation.

BACKGROUND: Many complications were reported to be related with nasotracheal intubation. Various chemical or mechanical techniques have been proposed to decrease hemorrhage and trauma associated with nasotracheal intubation but the results remain controversial. We conducted a prospective, randomized, single-blind study to elucidate the effect of an endotracheal tube softened with warm water before use on the incidence and severity of epistaxis following nasotracheal intubation. METHODS: Sixty-two healthy, (ASA class I or II) patients scheduled for elective surgery were randomly assigned into two groups. Patients in the treatment group were intubated with a softened endotracheal tube made possible by heating it in warm water while those in the control group were intubated with unsoftened (intact) tube. Epistaxis was evaluated immediately after intubation and its severity was graded as none, mild, moderate and severe. The use of Magill forceps and postoperative nasal morbidity were also recorded. RESULTS: The total incidence of epistaxis in the "unsoftened" group was significantly higher than that of "softened" group (76.7% vs. 43.8%, P = 0.0002). The severity of nasal hemorrhage was also significantly lightened in the "softened" group. No technical difficulty was encountered in intubation with a softened endotracheal tube by prewarming. The morbidity referable to nasal intubation, however, did not differ in both groups. CONCLUSIONS: In conclusion, our study shows that using an endotracheal tube softened by warm water could reduce the incidence and severity of epistaxis during the act of nasotracheal intubation. It is an effective way and worth a try.

Adolescent↗

PubMed1998

Hoarding behavior in dementia. A preliminary report.

Hoarding behavior has been reported in several mental disorders and is occasionally reported by the caregivers of dementia patients. Such behavior may have adverse effects on the patients and increase the burden of the caregivers. This study was conducted to investigate the prevalence of hoarding behavior in patients with dementia and identify the characteristics and psychiatric symptoms associated with it. The sample was 133 dementia patients admitted to a geropsychiatric ward. Of the 133 dementia patients, 30 (22.6%) showed hoarding. Hoarding was found in various types of dementia. Patients with hoarding had a higher prevalence of repetitive behaviors, hyperphagia, and pilfering. Results suggested that hoarding behavior is a common symptom in dementia patients and a complex phenomenon. Better understanding of the underlying pathogenesis may highlight specific pharmacological or behavioral methods for treatment of the behavior.

Aged↗

PubMed1997

STAT3 as an adapter to couple phosphatidylinositol 3-kinase to the IFNAR1 chain of the type I interferon receptor.

STAT (signal transducers and activators of transcription) proteins undergo cytokine-dependent phosphorylation on serine and tyrosine. STAT3, a transcription factor for acute phase response genes, was found to act as an adapter molecule in signal transduction from the type I interferon receptor. STAT3 bound to a conserved sequence in the cytoplasmic tail of the IFNAR1 chain of the receptor and underwent interferon-dependent tyrosine phosphorylation. The p85 regulatory subunit of phosphatidylinositol 3-kinase, which activates a series of serine kinases, bound to phosphorylated STAT3 and subsequently underwent tyrosine phosphorylation. Thus, STAT3 acts as an adapter to couple another signaling pathway to the interferon receptor.

Acute-Phase Proteins↗

PubMed1997

The short form of the interferon alpha/beta receptor chain 2 acts as a dominant negative for type I interferon action.

We have characterized the functional properties of the short form of the human interferon alpha/beta receptor chain 2 (IFNAR2), denoted IFNAR2.1. IFNAR2.1 contains a shortened cytoplasmic domain when compared with the recently cloned full-length IFNAR2 chain (IFNAR2. 2). We show that IFNalpha8 and IFNbeta1b induce antiviral and antiproliferative activity in mouse cell transfectants expressing the human IFNAR1 chain of the receptor and induce the formation of STAT1/STAT2 dimers in IFN-stimulated response element (ISRE)-dependent gel shift assays. In contrast, coexpression of IFNAR2.1 with IFNAR1 reduces the IFN-induced antiviral, antiproliferative and ISRE-dependent gel shift binding activity conferred by IFNAR1 alone. No antiviral or antiproliferative response to IFN, nor IFN-induced ISRE-dependent gel shift binding activity, was observed when IFNAR2.1 was expressed alone in murine cells. Therefore, IFNAR2.1 acts as a dominant negative for these IFN-induced activities. Our results suggest that IFNAR2.1 represents a nonfunctional version of the full-length chain (IFNAR2.2).

Animals↗

PubMed1997

RFC-1 gene expression regulates folate absorption in mouse small intestine.

Mediated folate compound transport inward in isolated luminal epithelial cells from mouse small intestine was delineated as pH-dependent and non-pH-dependent components on the basis of their differential sensitivity to the stilbene inhibitor, 4, 4'-diisothiocyanatostilbene-2,2'-disulfonic acid. pH dependence was manifested as higher maximum capacity (Vmax) for influx of l, L-5-CH3-H4folate at acidic pH compared with neutral or alkaline pH with no effect on saturability (Km). The pH-dependent component was relatively insensitive to inhibition by 4, 4'-diisothiocyanatostilbene-2,2'-disulfonic acid and highly saturable (Km or Ki = 2 to 4 microM) in the case of folic acid, folate coenzymes, and 4-aminofolate analogues as permeants or inhibitors. The non-pH-dependent component was highly sensitive to 4, 4'-diisothiocyanatostilbene-2,2'-disulfonic acid and poorly and variably saturable (Km or Ki = 20 to >2000 microM) with respect to these folate compounds. Only the pH-dependent transport component was developmentally regulated, showing much higher maximum capacity for l,L-5-CH3-H4folate influx in mature absorptive rather than proliferative crypt cells. The increase in pH-dependent influx during maturation was associated with an increase in RFC-1 gene expression in the form of a 2.5-kilobase RNA transcript and 58-kDa brush-border membrane protein detected by folate-based affinity labeling and with anti-mouse RFC-1 peptide antibodies. The size of this protein was the same as that encoded by RFC-1 mRNA. The treatment of mature absorptive cells with either the affinity label or the anti-RFC-1 peptide antibodies inhibited influx of l, L-[3H]-5-CH3-H4folate in a concentration-dependent manner. These results strongly suggest that pH-dependent folate absorption in this tissue is regulated by RFC-1 gene expression.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗