Biomedical subjects

T Yang

Publications and source records attributed to T Yang.

At least 181 records · Page 10Linked to original sources

PubMed1998

[Expression of secreted ligand domain of vaccinia growth factor encoded by vaccinia virus strain tian tan in E. coli and insect cells].

Vaccinia virus growth factor (VGF) is encoded by an early gene of vaccinia virus strain TianTan located near the border between the terminal inverted repeats and the internal region of the viral genome as one copy. Its relationship to members of epidermal growth factor superfamily was discovered when computer searches of protein sequences revealed that VGF has strong sequence homology with these growth factors. To further get insight into the biological activity of VGF, we cloned and expressed the secreted ligand domain of VGF (VGFsl) encoded by vaccinia virus strain TianTan in E. coli and insect cells. The results of biological activity test indicated that expressed products is capable of binding to the EGF receptor, and stimulating EGF receptor tyrosin autophosphorylation to a level greater than that of EGF.

Animals↗

PubMed1997

Synthesis and characterization of a novel retinylamine analog inhibitor of constitutively active rhodopsin mutants found in patients with autosomal dominant retinitis pigmentosa.

Two different mutations of the active-site Lys-296 in rhodopsin, K296E and K296M, have been found to cause autosomal dominant retinitis pigmentosa (ADRP). In vitro studies have shown that both mutations result in constitutive activation of the protein, suggesting that the activated state of the receptor may be responsible for retinal degeneration in patients with these mutations. Previous work has highlighted the potential of retinylamine analogs as active-site directed inactivators of constitutively active mutants of rhodopsin with the idea that these or related compounds might be used therapeutically for cases of ADRP involving mutations of the active-site Lys. Unfortunately, however, amine derivatives of 11-cis-retinal, although highly effective against a K296G mutant of rhodopsin, were without affect on the two naturally occurring ADRP mutants, presumably because of the greater steric bulk of Glu and Met side chains in comparison to Gly. For this reason we synthesized a retinylamine analog one carbon shorter than the parent 11-cis-retinal and show that this compound is indeed an effective inhibitor of both the K296E and K296M mutants. The 11-cis C19 retinylamine analog 1 inhibits constitutive activation of transducin by these mutants and their constitutive phosphorylation by rhodopsin kinase, and it does so in the presence of continuous illumination from room lights.

Animals↗

PubMed1997

p53 induced by ionizing radiation mediates DNA end-jointing activity, but not apoptosis of thyroid cells.

To understand the effects of ionizing radiation on thyroid cells, we investigated the role of p53 in mediating apoptosis and in DNA repair following in vivo and in vitro irradiation of thyroid cells. In vitro exposure of human thyroid cells to ionizing radiation of up to 5-8 Gy failed to induce apoptosis in primary cells. The same results were obtained when the thyroid gland was irradiated in the intact rat. To explore the mechanism of failure of the wild-type p53 in inducing apoptosis in thyroid cells, we investigated the expression of apoptosis-related genes, bax, bcl-2 and fas/APO-1 following irradiation or induction of temperature-sensitive p53. The expression of Bax, Bcl-2 and Fas/APO-1 in human primary cultured thyroid cells did not change after irradiation. To further confirm the results, we established a clonal cell line (tsFRO) in which a temperature sensitive p53 (Val138) expression vector was stably transfected to a thyroid carcinoma cell line lacking endogenous p53. Incubation of tsFRO cells at the permissive temperature for three days, however, did not induce apoptosis although G1 arrest was noted. Although enhanced expression of the bax mRNA level was observed, the expression of Bax, Bcl-2 and Fas/APO-1 protein did not change by shifting tsFRO cells to permissive temperature as well as irradiated primary cells. Furthermore, DNA end-jointing ability was examined by transfection of linearized luciferase plasmid into tsFRO cells. Increased luciferase activity occurred when the cells were cultured at the permissive temperature, indicating that the wild-type p53 enhances DNA end-jointing activity. Our results indicate that the wild-type p53 does not lead to apoptosis but facilitates DNA end-jointing in thyroid cells. These results may reflect specific responses in thyroid cells following irradiation.

Animals↗

PubMed1997

Post-translational processing and renal expression of mouse Indian hedgehog.

The full-length mouse Indian hedgehog (Ihh) cDNA was cloned from an embryonic 17.5-day kidney library and was used to study the post-translational processing of the peptide and temporal and spatial expression of the transcript. Sequence analysis predicted two putative translation initiation sites. Ihh translation was initiated at both initiation sites when expressed in an in vitro transcription/translation system. Expression of an Ihh mutant demonstrated that the internal translation initiation site was sufficient to produce the mature forms of Ihh. Ihh post-translational processing proceeded in a fashion similar to Sonic and Drosophila hedgehog; the unprocessed form underwent signal peptide cleavage as well as internal proteolytic processing to form a 19-kDa amino-terminal peptide and a 26-kDa carboxyl-terminal peptide. This processing required His313 present in a conserved serine protease motif. Ihh transcript was detected by in situ RNA hybridization as early as 10 days postcoitum (dpc) in developing gut, as early as 14.5 dpc in the cartilage primordium, and in the developing urogenital sinus. In semiquantitative reverse transcription-polymerase chain reaction experiments, Indian hedgehog transcript was first detected in the mouse metanephros at 14.5 dpc; transcript abundance increased with gestational age, becoming maximal in adulthood. In adult kidney, Ihh transcript was detected only in the proximal convoluted tubule and proximal straight tubule.

Amino Acid Sequence↗

PubMed1997

Deficient LAR expression decreases basal forebrain cholinergic neuronal size and hippocampal cholinergic innervation.

A role in neural development for protein tyrosine phosphatase (PTPase) receptors has been suggested by the finding of aberrant neurite outgrowth in Drosophila mutants lacking functional leukocyte common antigen-related (LAR) PTPase receptors; however, PTPase functions in the mammalian nervous system remain to be established. In transgenic mice containing a gene trap in the LAR gene, only trace expression of full-length LAR transcripts was found. In these mice, the size of basal forebrain cholinergic neurons was significantly reduced and cholinergic innervation of the dentate gyrus was markedly decreased. These findings constitute the first demonstration of an aberrant neuronal phenotype in a mammalian PTPase mutant and support the hypothesis that LAR-type PTPase receptors function to establish and/or maintain neuronal networks.

Acetylcholine↗

PubMed1997

Cholinergic stimulation of lacrimal acinar cells promotes redistribution of membrane-associated kinesin and the secretory protein, beta-hexosaminidase, and increases kinesin motor activity.

The role of the microtubule-based motor, kinesin, in membrane trafficking has been investigated in resting and stimulated acinar cells from rabbit lacrimal gland, a cholinergically controlled secretory tissue. Microtubule-dependent motors from extracts of control and carbachol-treated acini were isolated by microtubule-affinity purification and their activity was determined using a video-enhanced differential interference contrast microscopy assay for microtubule gliding. The observation that carbachol treatment resulted in a 2.2-fold stimulation of the frequency of GTP-dependent microtubule gliding in fractions isolated by microtubule-affinity purification and GTP release suggested that kinesin was a target of carbachol-induced stimulation. Resolution of membranes from resting cells by fractionation on a sorbitol density gradient followed by partitioning analysis in a dextran-polyethyleneglycol two-phase system revealed that membrane-associated kinesin codistributed with Golgi-derived membranes, a post-Golgi secretory compartment designated Hex1, membranes from a trans Golgi network-like compartment, endoplasmic reticulum and a group of putative lysosomal membranes containing cathepsin B. Comparable fractionation of carbachol-treated acini showed that stimulation caused redistributions of membrane-associated kinesin, the secretory enzyme beta-hexosaminidase, and galactosyltransferase that appeared to reflect both a reorganization within the Golgi complex and a return of material to the Golgi complex from the secretory pathway. Our findings that carbachol promotes activation of lacrimal acinar kinesin as well as major shifts in kinesin-membrane association within the secretory pathway suggests that kinesin plays a major role in secretory vesicle assembly, apical secretion, and/or secretory vesicle membrane recycling in the lacrimal gland.

Animals↗

PubMed1997

Effects of ionic channel antagonists barium, cesium, and UL-FS-49 on vagal slowing of atrial rate in dogs.

In response to a brief vagal stimulus, the atrial rate initially slows, then transiently accelerates, and slows a second time. We determined the effects of three antagonists to two ionic channels on this characteristic triphasic pacemaker response. Brief bursts of vagal stimulation were delivered to anesthetized dogs, and atrial cycle lengths were recorded. Either barium, cesium, or UL-FS-49 was administered. Barium, which primarily blocks the acetylcholine-sensitive potassium current (IK,ACh), attenuated the initial vagally induced bradycardia by > 50% without affecting the subsequent acceleration or the secondary slowing. Cesium and UL-FS-49 [both of which primarily block the pacemaker current (If)] did not affect the initial vagal slowing of atrial rate but abolished the acceleratory portion of the response. The secondary slowing was abolished by cesium but not by UL-FS-49. We conclude that the initial rapid atrial response to acetylcholine is mediated mainly by the IK,ACh, with little contribution from the If. The subsequent acceleration is mediated by activation of the If.

Acetylcholine↗

PubMed1997

Expression of PTHrP, PTH/PTHrP receptor, and Ca(2+)-sensing receptor mRNAs along the rat nephron.

To provide a frame of reference for studies of renal divalent cation and phosphate metabolism, we assessed the cellular localization of kidney calcium receptor (RaKCaR), parathyroid hormone-related protein (PTHrP), and parathyroid hormone/ parathyroid hormone-related protein (PTH/PTHrP) receptor mRNA. The studies used using reverse transcription-polymerase chain reaction (RT-PCR) applied to cDNA prepared from dissected rat nephron segments and from primary cultures of mouse juxtaglomerular granular cells. With species-specific primers, PCR products of expected size were obtained for RaKCaR (967 bp), PTHrP (420 bp), and PTH/PTHrP receptor (817 bp), with product identity being confirmed by restriction digestion. RaKCaR mRNA was found in medullary and cortical thick ascending limbs (MTAL and CTAL, respectively), the macula densa-containing segment, distal convoluted tubules (DCT), and, to a lesser extent, in cortical collecting ducts (CCD). It was not found in glomeruli, proximal convoluted and straight tubules (PCT and PST, respectively), outer and inner medullary collecting ducts (OMCD and IMCD, respectively), or in juxtaglomerular granular cell isolates. PTHrP mRNA was predominantly expressed in glomeruli and at lower levels in PCT and the macula densacontaining segment but was not detectable in CTAL, MTAL, DCT, and CD segments. Presence of PTH/PTHrP receptor mRNA was demonstrated in glomeruli, PCT, PST, CTAL, MTAL, and DCT but not in CD segments. These results suggest that the function of TAL and DCT cells, in addition to being affected by PTH, may be directly altered by extracellular divalent cations through RaKCaR and that PTHrP may act in the glomerulus and proximal tubule as an autocrine or paracrine regulator of hemodynamics and phosphate transport.

Animals↗

PubMed1997

Absence of tubuloglomerular feedback responses in AT1A receptor-deficient mice.

Experiments were performed in a recently generated strain of mice with an angiotensin II AT1A-receptor null mutation (M. Ito, M. I. Oliverio, P. J. Mannon, C. F. Best, N. Maeda, O. Smithies, and T. M. coffman. Proc. Natl. Acad. Sci. USA 92: 3521-3525, 1995) to examine the effects of chronic AT1A receptor deficiency on tubuloglomerular feeback (TGF) responses. All animals were genotyped by polymerase chain reaction using primers designed to amplify sequences from the deleted AT1A gene and from the neomycin resistance gene. Normal mice (AT1A +/+) and mice heterozygous (AT1A +/-) and homozygous (AT1A -/-) for the gene disruption were anesthetized, and stop-flow pressures (PSF) were determined during changes in loop perfusion rate with previously established micropuncture methods. In five AT1A +/+ mice (26 tubules) mean PSF at zero loop flow was 37.2 +/- 1.5 mmHg, falling to 28.2 +/- 1.9 mmHg at a flow of 45 nl/min (P < 0.0001). Flow rate causing the half-maximum response (V1/2) was 8.7 +/- 0.4 nl/min. In four AT1A +/- animals (19 tubules) mean PSF at zero flow was 39.9 +/- 2.4 mmHg, falling to 34.8 +/- 2.7 mmHg at 45 nl/min (mean V1/2 8.6 +/- 1.04 nl/min). In five AT1A -/- mice (24 tubules) PSF was not significantly affected by loop flow with PSF averaging 33.9 +/- 1.7 mmHg at zero flow and 33.2 +/- 1.6 mmHg at 45 nl/min (not significant). Mean arterial blood pressures in the anesthetized and laparotomized mice were 91.8 +/- 2.2, 97.1 +/- 3, and 80.7 +/- 3.2 mmHg in the AT1A +/+, AT1A +/-, and AT1A -/- animals, respectively. Blood pressure responses to exogenous angiotensin II were greatly blunted in the AT1A -/- mice. We conclude that AT1A receptor-mediated effects of angiotensin II are in essential component of TGF responsiveness under chronic conditions. Our studies show the feasibility of using complex micropuncture methods in mice, an approach that widens the potential of genetically altered mouse strains as experimental models.

Animals↗

PubMed1997

Cyclooxygenase-2 is expressed in bladder during fetal development and stimulated by outlet obstruction.

Studies were undertaken to assess expression of inducible cyclooxygenase (COX)-2 in bladder during fetal development and COX-1 and COX-2 expression after outlet obstruction. Bladder tissue or bladder progenitor tissue was harvested from CD-1 murine embryos at embryonic days 11.5 (E11.5), E14.5, E17.5, E20.5 (newborn), and from adult. Bladder obstruction was created in adult female mice by ligating the urethra, and bladders were harvested after 3-24 h of obstruction. Gene expression was assessed by semiquantitative reverse transcription-polymerase chain reaction and Western blotting. COX-2 was highly expressed at the early stages of bladder development and declined progressively throughout gestation. In adult bladder, both COX-1 and COX-2 were detectable at low levels under basal conditions. An approximately 30-fold increase in COX-2 mRNA was seen after 24 h of obstruction. In contrast, COX-1 did not change with obstruction. COX-2 mRNA levels peaked at 6 h of obstruction. In regional bladder-distention models, COX-2 induction was confined to the area of distention. Bladder outlet obstruction stimulates COX-2 expression dramatically, reactivating a gene that is highly expressed during fetal development.

Animals↗

PubMed1997

Rapid inactivation determines the rectification and [K+]o dependence of the rapid component of the delayed rectifier K+ current in cardiac cells.

Two characteristic features of the rapid component of the cardiac delayed rectifier current (IKr) are prominent inward rectification and an unexpected reduction in activating current with decreased [K+]o. Similar features are observed with heterologous expression of HERG, the gene thought to encode the channel carrying IKr, moreover, recent studies indicate that the mechanism underlying rectification of HERG current is the inactivation that channels rapidly undergo during depolarizing pulses. The present studies were designed to determine the mechanism of IKr rectification and [K+]o sensitivity in the mouse atrial myocyte cell line, AT-1 cells. Reducing [Mg2+]i to 0, which reverses inward rectification of some K+ channels, did not alter IKr current-voltage relationships, although it did decrease sensitivity to the IKr blockers dofetilide and quinidine 2- to 5-fold. To determine the presence and extent of fast inactivation of IKr in AT-1 cells, a brief hyperpolarizing pulse (20 ms to -120 mV) was applied during long depolarizations. Immediately after this pulse, a very large outward current that decayed rapidly to the previous activating current baseline was observed. This outward current component was blocked by the IKr-specific inhibitor dofetilide, indicating that it represented recovery from fast inactivation during the hyperpolarizing step, with fast reinactivation during the return to depolarized potential. With removal of inactivation using this approach, current-voltage relationships for IKr ([K+]o, 1 to 20 mmol/L) were linar and reversed close to the predicted Nernst potential for K+. In addition, decreased [K+]o decreased the time constants for open-->inactivated and inactivated-->open transitions. Thus, in these cardiac myocytes, as with heterologously expressed HERG, IKr undergoes fast inactivation that determines its characteristic inward rectification. These studies demonstrate that the mechanism underlying decreased activating current observed at low [K+]o is more extensive fast inactivation.

Animals↗

PubMed1997

[Operative treatment of vesical diverticula].

We reviewed the results of operative management of 31 patients with vesical deverticula, and introduce a simple technique for treating large bladder diverticula. In the 31 patients with vesical diverticula analysed, 23 were followed up for at least six months. Of the 31 patients, 25 were male and 6 female. The average age was 54.2 years. Diverticula was secondary to bladderoutlet obstruction. Seven cases had intradiverticular tumors, and 9 stones in the sac. The diagnosis of vesical diverticula was usually made by cystogram or ultrasonography. The operative indications for vesical diverticula included stone formation, intradiverticular tumor, ureteral obstruction, incomplete empting diverticulum and urine retention due to large diverticula. The combined extravesical and intravesical method was often used. 26 patients underwent both operations for outlet obstruction and vesical diverticula at the same time. Of the 23 followed-up cases, 21 had no symptoms of the urinary tract. Five of the 7 patients with intradiverticular tumor died within 2.5 years; one of the rest survived for 2 years, and the others for 6 years. Two patients with large vesical diverticula received intravesical separation of diverticula. No complications encountered in this simple, time-saving and safe procedure. Cystograms revealed normal condition. The choice of operative techniques to treat vesical diverticula varies with each individual patient. The technique of intravesical separation of vesical diverticula is suitable for large, adhesive and posterior diverticula.

Adult↗

PubMed1997

[Effect of antihypertensive agents on plasma endothelin, nitric oxide and so on in essential hypertension].

Ninty patients with mild to moderate essential hypertension (EH) were randomly divided into three groups and treated with Enalapril (E), Metoprolol (M) and Nifedipine (N) respectively. After a six-week-treatment, SBP and DBP of each of the three groups decreased significantly (vs. pre-treatment, P < 0.001). Plasma concentration of ET, NO, cGAMP and MDA in group M remained unchanged, and that of MDA in group N, especially of the stage II EH, decreased remarkably (vs. pretreatment, P < 0.05; vs. that of stage I EH, P < 0.05). While that of ET, NO, cGMP, and MDA in group E changed significantly (vs. Pretreatment, P < 0.01) and that of ET and MDA of stage II EH in group E exhibited more remarkable changes (vs. that of stage I, P < 0.05). It is suggested that E, and at some degree N, may protect the vascular endothelium from being damaged in EH, and also may contribute to prevent EH from development.

Adrenergic beta-Antagonists↗

PubMed1997

[The inhibitory effects of antioxidant vitamins on serum oxLDL and experimental atherosclerosis of rabbits].

OBJECTIVE AND METHODS: In order to study the inhibitory effects of antioxidant vitamins on serum (low oxidative density lipoproteins, oxLDL) and experimental atherosclerosis in rabbits, 20 rabbits were fed on cholesterol rich diet and antioxidant vitamins (vitamin E, vitamin C and beta carotene) for 12 weeks. oxLDL were tested by ELISA at the beginning of experiment and after 4 weeks 8 weeks. RESULTS: The results showed that supplement of antioxidant vitamins can decrease the oxLDL level significantly and inhibited development of atherosclerosis lesion around aorta in rabbits.

Animals↗

PubMed1997

[Expression of foreign genes in adult rats' central nervous system by use of defective herpes simplex virus type 1 vectors].

We developed a defective herpes simplex virus (HSV) vector system that permitted the introduction of virtually any gene into mammalian central nervous system neurons. The HSV-1 amplicon plasmid, pHSL, contained a beta-galactosidase transcription cassette directed by HSV-1 IE68 promoter and two elements from HSV-1 genome: the origin of HSV-1 replication and its packaging site sequence. Being transfected into immortalized cells such as Vero cells in the present of HSV-1 to provide the helper virus function, (in our tests, a temperature-sensitive mutank tsK strain with permissive temperature at 31 degrees C was used), the prototype vector pHSL could be packaged into HSV-1 particles as a head-to-tail concatemer with the size of about the genome of HSV-1. A mixed HSV-1 stocks obtained were called dvHSL. Infection of cultured embryonic spinal cord motor neurons and forebrain cortex neurons of rats with dvHSL showed that beta-galactosidase was expressed up to twelve days. Via corneal inoculation, the trigeminal ganglia of rats were infected by dvHSL and the expression of beta-galactosidase could be detected there at different times after inoculation for at least two months. Infection of the forebrain cortex of rats with dvHSL through stereotactic injection showed that the expression of beta-galactosidase was restricted to the injection site for up to two months.

Animals↗

PubMed1997

[Characteristics of virus growth factor (VGF) encoded by vaccinia virus Tian Tan strain].

Vaccinia virus growth factor (VGF) is encoded by an early gene located near the border between the terminal inverted repeats and the internal unique region of the viral genome. It has been suggested that secreted VGF may serve to stimulate the metabolism of neighboring uninfected cells, thereby increasing the capacity of these cells to support viral replication. In this study, we cloned and sequenced the VGF gene of vaccinia virus strain Tian Tap. The analytical results indicated that VGF of strain Tian Tan possessed the core sequences of Epidermal growth factor superfamily, and more closely related to that of strain WR than to those of other orthopoxvirus strains. Overall deduced amino acid divergence of 4.3% was observed between Tian Tan and WR VGF protein, while divergences ranged from 10% to 20% compared to other orthopoxviruses strains. Most of the amino acid substitutions were found within signal peptide and transmembrane regions, but were not present in secreted ligand domain. It was striking that the amino acid sequence deduced from the ORF TB22L which located within the right terminal region of genome was identical to VGF protein amino acids 67-140, suggesting that ORF TB22L may be derived from the seconed copy of VGF gene of strain Tian Tan.

Intercellular Signaling Peptides and Proteins↗

PubMed1997

[Study on the immunophenotype of myeloid cells in myelodysplastic syndromes and its clinical implications].

OBJECTIVE: To explore the immunophenotype of myeloid cells in myelodysplastic syndromes and its clinical implications. METHODS: A panel of monoclonal antibodies was used to detect CD13, CD33, CD15 and CD14 on the membrane surfaces of myeloid cells in the bone marrow from 51 patients with myelodysplastic syndromes (MDS), 21 with aplastic anemia (AA), 21 with paroxysmal nocturnal hemoglobinuria (PNH), and 15 normal subjects, by immunoenzymatic assay. The morphology and chromosome karyotype of bone marrow cells of MDS patients were also examined. RESULTS: CD14+ cells, CD13+ cells and CD33+ cells in the bone marrow were more in MDS patients than in normal controls, AA patients and PNH patients. CD15+ cells in the bone marrow were less in MDS patients than in normal controls. The percentages of CD14, CD13 and CD33 positive cells in the bone marrow of MDS patients were related to the percentage of myeloblast, the chromosomal aberrations and the response to treatment. CONCLUSION: There was an immunophenotypic misexpression of myeloid cells in MDS patients. Immunophenotype analysis of myeloid cells might be useful for the diagnosis and directing treatment in MDS patients.

Adolescent↗

PubMed1997

Inhibition of cardiac potassium currents by the vesnarinone analog OPC-18790: comparison with quinidine and dofetilide.

OPC-18790 is a vesnarinone analog currently in clinical trials for treatment of heart failure. In vitro studies have shown that, in addition to its positive inotropic actions, OPC-18790 prolongs cardiac action potentials. Therefore, in this study, the effects of OPC-18790 on cardiac potassium currents were compared with those we previously observed for the blockers quinidine and dofetilide in two test systems, i.e., L-cells stably transfected with mammalian cardiac potassium channel clones (Kv1.4, Kv1.5 and Kv2.1) and mouse AT-1 cells, in which the rapidly inactivating component of the cardiac delayed rectifier (I(Kr)) is the major repolarizing current. In L-cells, 10 to 100 microM OPC-18790 reduced Kv1.4, Kv1.5 and Kv2.1 currents by <30%, whereas quinidine was a more potent blocker (EC50 < 10 microM) and the I(Kr)-specific blocker dofetilide was without effect. In contrast, in AT-1 cells, OPC-18790 blocked I(Kr) with an EC50 (0.96 +/- 0.12 microM, n = 10) similar to that of quinidine (0.9 +/- 0.2 microM). For both drugs, block was voltage dependent, increasing at positive potentials. OPC-18790 and quinidine showed no frequency dependence, implying block of resting channels and/or very rapid block of open channels; this is in contrast to dofetilide, which displayed slow onset kinetics of block. Thus, we conclude that, 1) unlike quinidine, OPC-18790 does not significantly inhibit currents obtained by expression of the cardiac potassium channel clones Kv1.4, Kv1.5 and Kv2.1; 2) like quinidine and dofetilide, OPC-18790 blocks I(Kr) in AT-1 cells, but the kinetics of block onset more closely resemble those of quinidine than dofetilide; and 3) block of I(Kr) appears to be an important mechanism underlying the action potential-prolonging properties of OPC-18790.

Animals↗