Biomedical subjects

C H Yang

Publications and source records attributed to C H Yang.

At least 19 recordsLinked to original sources

PubMed1998

Differences in activity between alpha and beta type I interferons explored by mutational analysis.

Type I interferon (IFN) subtypes alpha and beta share a common multicomponent, cell surface receptor and elicit a similar range of biological responses, including antiviral, antiproliferative, and immunomodulatory activities. However, alpha and beta IFNs exhibit key differences in several biological properties. For example, IFN-beta, but not IFN-alpha, induces the association of tyrosine-phosphorylated receptor components ifnar1 and ifnar2, and has activity in cells lacking the IFN receptor-associated, Janus kinase tyk2. To define the structural basis for these functional differences we produced human IFN-beta with point mutations and compared them to wild-type IFN-beta in assays that distinguish alpha and beta IFN subtypes. IFN-beta mutants with charged residues (N86K, N86E, or Y92D) introduced at two positions in the C helix lost the ability to induce the association of tyrosine-phosphorylated receptor chains and had reduced activity on tyk2-deficient cells. The combination of negatively charged residues N86E and Y92D (homologous with IFN-alpha8) increased the cross-species activity of the mutant IFN-betas on bovine cells to a level comparable to that of human IFN-alphas. In contrast, point mutations in the AB loop and D helix had no significant effect on these subtype-specific activities. A subset of these latter mutations did, however, reduce activity in a manner analogous to IFN-alpha mutations. The effects of these mutations on IFN-beta activity are discussed in the context of a family of related ligands acting through a common receptor and signaling pathway.

Amino Acid Sequence↗

PubMed1998

Induction of Jak/STAT signaling by activation of the type 1 TNF receptor.

Cellular responses to TNF are initiated by either of two cell surface receptors, the type 1 TNF receptor (TNFR1) and the type 2 TNF receptor (TNFR2). Although neither receptor contains an intrinsic protein tyrosine kinase, such activity has been implicated in TNF action. In this study, we show that murine TNF induces the tyrosine phosphorylation and activation of the intracellular Janus tyrosine kinases Jak1, Jak2, and Tyk2 in murine 3T3-L1 adipocytes. Activation of Jak kinases by TNF was associated with tyrosine phosphorylation of STAT1, STAT3, STAT5, and STAT6, but not STAT2 or STAT4, showing that TNF acts on a specific subset of these latent cytoplasmic transcription factors in 3T3-L1 adipocytes. Agonist antiserum to TNFR1 induced Jak kinase and STAT protein phosphorylation. Phosphorylation of Jak proteins was also induced by human TNF, which selectively binds to TNFR1 on murine cells. 35S-labeled Jak kinases were precipitated from a cell-free system and from lysates of 3T3-L1 adipocytes by a glutathione S-transferase fusion protein containing the cytoplasmic domain of TNFR1. These results suggest that the cytoplasmic domain of TNFR1 can directly interact with and form signaling complexes with Jak kinases. Jak2 was precipitated from HeLa cells by antiserum to TNFR1, directly demonstrating their association in vivo. Thus, TNF activates a Jak/STAT signal-transduction cascade by acting through TNFR1.

3T3 Cells↗

PubMed1998

The antiviral action of interferon is potentiated by removal of the conserved IRTAM domain of the IFNAR1 chain of the interferon alpha/beta receptor: effects on JAK-STAT activation and receptor down-regulation.

The first cloned chain (IFNAR1) of the human interferon-alpha (IFN alpha) receptor acts as a species-specific transducer for type 1 IFN action when transfected into heterologous mouse cells. Stably transfected mouse L929 cell lines expressing truncation mutants of the intracellular domain of the human IFNAR1 chain were tested for biological responses to human IFN alpha. Deletion of the intracellular domain resulted in a complete loss of sensitivity to the biological activity of human IFN but markedly increased IFNAR1 cell surface expression, demonstrating that the intracellular domain is required for biological function and contains a domain that negatively regulates its cell surface expression. Removal of the conserved membrane distal 16-amino-acid IRTAM (Interferon Receptor Tyrosine Activation Motif) sequence: (1) increased sensitivity to IFN alpha's antiviral activity, (2) increased the rapid IFN alpha-dependent formation of STAT-containing DNA-binding complexes, (3) prolonged tyrosine phosphorylation kinetics of the JAK-STAT pathway, and (4) blocked the IFN-dependent down-regulation of the IFNAR1 chain. These results indicate that the IRTAM negatively regulates signalling events required for the induction of IFN's biological actions via regulating receptor down-regulation.

Amino Acid Sequence↗

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↗

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↗

PubMed1997

mirror encodes a novel PBX-class homeoprotein that functions in the definition of the dorsal-ventral border in the Drosophila eye.

The Drosophila eye is composed of dorsal and ventral mirror-image fields of opposite chiral forms of ommatidia. The boundary between these fields is known as the equator. We describe a novel gene, mirror (mrr), which is expressed in the dorsal half of the eye and plays a key role in forming the equator. Ectopic equators can be generated by juxtaposing mrr expressing and nonexpressing cells, and the path of the normal equator can be altered by changing the domain of mrr expression. These observations suggest that mrr is a key component in defining the dorsal-ventral boundary of tissue polarity in the eye. In addition, loss of mrr function leads to embryonic lethality and segmental defects, and its expression pattern suggests that it may also act to define segmental borders. Mirror is a member of the class of homeoproteins defined by the human proto-oncogene PBX1. mrr is similar to the Iroquois genes ara and caup and is located adjacent to them in this recently described homeotic cluster.

Amino Acid Sequence↗

PubMed1997

Carbachol induces inward current in rat neostriatal neurons through a G-protein-coupled mechanism.

Our recent study demonstrated that carbachol can act at M1-like muscarinic receptors to reduce the membrane K+ conductance and excite the neostriatal neurons. In the present study, we further studied the molecular mechanism by which carbachol induced inward currents in neostriatal neurons. In acutely isolated neostriatal neurons held at-60 mV, pressure application of carbachol (30 microM) induced a transient inward current underlying whole-cell voltage-clamp mode. In cells loaded with the stable GDP analogue guanosine 5'-0-(2-thiodiphosphate) (GDP-beta-S, 1 mM), the carbachol-induced inward current was significantly diminished. However, the carbachol response was not affected by intracellular dialysis of the neostriatal neurons with either protein kinase C (PKC) inhibitors, PKCI 19-36 (5 microM) or NPC-15437 (20 microM), or a potent cAMP-dependent protein kinase (PKA) inhibitor, Rp-cAMPS (25 microM). These results show that a G-protein-coupled mechanism mediates carbachol-induced inward current in the neostriatal neurons and that neither PKC- nor PKA-dependent intracellular transduction pathways are involved in the carbachol response.

Animals↗

PubMed1997

Behavioural disturbances in psychiatric inpatients with dementia of the Alzheimer's type in Taiwan.

This report studied behavioural disturbances in psychiatric inpatients with dementia of the Alzheimer's type (DAT) in Taiwan. The sample consisted of 75 inpatients with DAT who were consecutively admitted to the geropsychiatric ward. Their behavioural disturbances were obtained from semistructured interviews with families and ward observation. There were eight main behavioural disturbances: getting lost, repetitive phenomena, sleep disturbance, aggression, wandering, hyperphagia, hoarding behaviour, and inappropriate sexual behaviour. Number of behavioural disturbances, wandering, hyperphagia and sleep disturbance were significantly associated with the severity of cognitive impairment.

Aged↗

PubMed1997

Community-acquired Acinetobacter pneumonia: a case report.

A 35-year-old male with glucose-6-phosphate dehydrogenase (G6PD) deficiency was admitted because of right chest (pleuritic) pain, fever, cough with scarce production of blood-tinged sputum, and generalized yellowish discolouration of skin for 2 days. Radiographic examination revealed right lower lobe necrotizing pneumonia. Hypotension, dyspnoea and severe haemolysis was noted the next day. Echo-guided lung aspiration and sputum cultures both grew Acinetobacter baumannii. Antibiotic therapy was started immediately, but fever persisted and abscess formation was noted 1 week later. After aggressive supportive and antibiotic therapy, he made a slow but complete recovery from the pneumonia, and was then discharged in a stable condition. Acinetobacter baumannii is a well-known causative agent of nosocomial infections, particularly in intensive units. Community-acquired pneumonia, however, is quite rare, and usually has a fulminant course and high case fatality rate.

Acinetobacter↗

PubMed1997

Intraocular lens position and anterior chamber angle changes after cataract extraction in eyes with primary angle-closure glaucoma.

PURPOSE: To prospectively study the anterior chamber angle in eyes with chronic primary angle-closure glaucoma (PACG) having posterior chamber intraocular lens (IOL) implantation and evaluate IOL position and intraocular pressure (IOP). SETTING: National Taiwan University Hospital, Taipei, Taiwan. METHODS: Using Scheimpflug image processing, the anterior chamber angles were studied in 20 consecutive eyes with chronic PACG and 10 control eyes before and after posterior chamber IOL implantation. Anterior chamber depth, chamber angle width, IOL position, and IOP change were evaluated. RESULTS: Mean anterior chamber depth in the PACG group was 2.04 +/- 0.29 mm preoperatively and 3.44 +/- 0.16 mm postoperatively. The anterior chamber angle widened significantly in relation to the superior, inferior, temporal, and nasal quadrants after surgery. The degree of IOL tilting and decentration was the same in both the PACG and control groups. All eyes in the PACG group maintained an IOP under 21 mm Hg during the 6 month follow-up. Eighty-four percent maintained or decreased their antiglaucoma medication; 16% required increased medication. CONCLUSION: Cataract extraction with posterior chamber IOL implantation in eyes with PACG controlled IOP well in most cases.

Aged↗

PubMed1997

Effect of exercise and exogenous glucocorticoid on serum level of intact parathyroid hormone.

Most previous studies suggest that physical exercise, or physiological response to exercise such as cortisol and adrenaline secretion regulate parathyroid hormone (PTH) secretion in humans. To investigate the effects and possible interaction of exercise and excessive glucocorticoid on PTH secretion, we examined the serum of levels of intact-PTH, cortisol, adrenocorticotrophic hormone (ACTH), calcium, magnesium and phosphorus before and during one-hour of bicycle-ergometric exercise at 60% of maximal oxygen uptake. These exercise tests were performed on eight Chinese male volunteers aged between 20 and 25 years, once with and once without pretreatment with 0.5 mg of dexamethasone taken orally 9.5 hours in advance. The results showed that dexamethasone pretreatment significantly lowered basal levels of cortisol and ACTH, but intact PTH did not change. After 60 minutes of bicycling, intact PTH level increases by 50% of baseline both with and without dexamethasone pretreatment. Serum levels of calcium, corrected for changes in serum albumin concentration, phosphorus and magnesium also increased in both cases. This study demonstrated an increase of intact-PTH with exercise which was not associated with hypocalcemia or hypomagnesemia, and was not altered in the presence of mild exogenous glucocorticoid excess and suppressed endogenous cortisol secretion.

Adrenocorticotropic Hormone↗

PubMed1997

Inhibition of RPE cell-mediated matrix adhesion and collagen gel contraction by crovidisin, a collagen-binding snake venom protein.

PURPOSE: Cell-mediated collagen gel contraction plays an important role in the pathogenesis of proliferative vitreoretinopathy (PVR). Anti-adhesion therapy has been suggested as a promising strategy in the treatment of PVR. Crovidisin, a snake venom protein isolated from Crotalus viridis, has been shown to bind selectively to collagen and to inhibit collagen-induced platelet aggregation. In the present study, the effectiveness of crovidisin in inhibiting the attachment of retinal pigment epithelial (RPE) cells to collagen, and RPE cell-mediated collagen gel contraction, was evaluated. METHODS: Fluorescein isothiocyanate (FITC)-conjugated crovidisin was prepared and used to evaluate its binding affinity for collagen type I, fibronectin, vitronectin, and laminin. The inhibitory effect of crovidisin on RPE cell-mediated extracellular matrix attachment and collagen gel contraction was evaluated by cell adhesion and type I collagen gel contraction assays. The cytotoxic effect of crovidisin was examined with a cell proliferation assay, using the Alamar blue method. Flavoridin, an Arg-Gly-Asp-containing peptide from viper venom, was used for comparison. RESULTS: FITC-conjugated crovidisin bound selectively to collagen type I with high affinity. It did not bind to other matrix proteins, including fibronectin, vitronectin and laminin, nor to RPE cells. Crovidisin inhibited RPE cell attachment to type I collagen in a dose-dependent manner. This inhibitory effect was enhanced by the presence of flavoridin. Crovidisin also dose-dependently inhibited RPE cell-mediated type I collagen gel contraction. Crovidisin was non-toxic to RPE cells. CONCLUSIONS: Crovidisin, a snake venom-derived collagen-binding protein, possessing an inhibitory activity on RPE cell-collagen interaction and RPE cell-mediated collagen gel contraction, may be a useful tool for studying cell-collagen interaction, and a potential anti-adhesion therapeutic agent for ocular disorders in which cell-collagen interaction in involved, such as PVR.

Animals↗

PubMed1997

Evidence for the essential histidine residues in geranylgeranyl transferase type I from bovine testis.

Geranylgeranyl transferase was purified 30,000-fold by sequential use of 30-50% ammonium sulfate fractionation, Q-Sepharose anion exchange chromatography, Phenyl Superose hydrophobic interaction chromatography, Sephacryl S-300 gel filtration chromatography, and peptide (YREKKFFCAIL) affinity chromatography. Geranylgeranyl transferase, when incubated with diethyl pyrocarbonate (DEPC), a histidine-specific reagent, shows time-dependent inactivation, and the activity is restored by the addition of neutral hydroxylamine. The inactivation follows pseudo-first order kinetics with a second order rate constant of 0.319 M-1min-1. The overall results thus provide evidence that a histidine residue in the active site is involved in the catalytic mechanism of the geranylgeranyl transferase reaction.

Alkyl and Aryl Transferases↗

PubMed1997

Anterior chamber angles shallowing and intraocular pressure after topical pilocarpine.

Pilocarpine has been well recognized as the drug of choice for acute angle-closure glaucoma. The purpose of this study is to clarify quantitatively the change of anterior chamber angle and depth with the passage of time after pilocarpine drop administration. Chamber angles of the four quadrants and chamber depths were measured in 18 normal subjects by Scheimpflug Video Image prior to and 30, 60, and 180 minutes after administration of one drop of 4% pilocarpine in one eye, while the opposite eye served as control. The anterior chamber angle and depth showed a significant shallowing at 30, 60 and 180 minutes after 4% pilocarpine administration with a maximal effect of -3.61 degrees and -0.15 mm at 30 minutes, respectively, while the reduction of intraocular pressure reached its maximal effect at 180 minutes. These facts should be well understood in the treatment of angle-closure glaucoma.

Adult↗

PubMed1997

A transgenic mutant of Lactuca sativa (lettuce) with a T-DNA tightly linked to loss of downy mildew resistance.

One hundred and ninety-two independent primary transformants of lettuce cv. Diana were obtained by co-cultivation with Agrobacterium tumefaciens carrying constructs containing maize Ac transposase and Ds. R2 families were screened for mutations at four genes (Dm) for resistance to downy mildew. One family, designated dm3t524, had lost resistance to an isolate of Bremia lactucae expressing the avirulence gene Avr3. Loss of resistance segregated as a single recessive allele of Dm3. The mutation was not due to a large deletion as all molecular markers flanking Dm3 were present. Loss of Dm3 activity co-segregated with a T-DNA from which Ds had excised. Genomic DNA flanking the right border of this T-DNA was isolated by inverse polymerase chain reaction. This genomic sequence was present in four to five copies in wild-type cv. Diana. One copy was missing in all eight deletion mutants of Dm3 and altered in dm3t524, indicating tight physical linkage to Dm3. Three open reading frames (ORFs) occurred in a 6.6-kb region flanking the insertion site; however, expression of these ORFs was not detected. No similarities were detected between these ORFs and resistance genes cloned from other species. Transgenic complementation with 11-to 27-kb genomic fragments of Diana spanning the insertion site failed to restore Dm3 function to two ethyl methanesulfonate (EMS)-induced mutants of Dm3 or to cv. Cobham Green, which naturally lacks Dm3 activity. Therefore, either the T-DNA inserted extremely close to, but not within, Dm3 and the mutation may have been caused by secondary movement of Ds, or Dm3 activity is encoded by a gene extending beyond the fragments used for complementation.

DNA, Bacterial↗

PubMed1997

Epidural dexamethasone reduces the incidence of backache after lumbar epidural anesthesia.

We performed a prospective, randomized, double-blind study to compare the effect of epidural dexamethasone on the incidence of postepidural backache after nonobstetric surgery. One thousand unpremedicated ASA physical status I or II patients scheduled for hemorrhoidectomy were randomly assigned to two groups: Group I patients received 25 mL 2% lidocaine with epinephrine 1:200,000 and 1 mL dexamethasone (5 mg) epidurally. Patients were interviewed at 24,48, and 72 h postoperatively using a standard visual analog scale (VAS) for evaluation of postepidural backache. A patient was considered to have postepidural backache when the postoperative VAS score was higher than the preoperative score. The incidence of postepidural backache in Group I patients for the 3 days were 22.8%, 17.4%, and 9.2%, all of which were significantly more frequent than observed in Group II patients (7.4%,5.6%, and 2.8%, P < 0.01). The severity and duration of postepidural backache were also significantly decreased in Group II patients. In our study, there was a significant association between postepidural backache and multiple attempts at epidural needle insertion. In summary, epidural dexamethasone reduced the incidence and severity of postepidural backache.

Adult↗