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T Wang

Publications and source records attributed to T Wang.

At least 703 records · Page 39Linked to original sources
PubMed1991

Mast cells in the chick digestive tract. II. Fixation, distribution, histochemistry and ultrastructure.

Mast cells in the chick digestive tract were investigated with different fixatives, histochemical methods and transmission electron microscopy. Carnoy's fluid was the best fixative for the chick mast cell. Fixation in formalin reduced the number of mast cells and dissolved the granules. Mast cells stained reddish purple with toluidine blue, and bright blue with Alcian blue-periodic acid schiff (AB-PAS). Staining with Alcian blue-safranin O (AB-S) resulted in some cells only containing blue or red granules, and others containing both blue and red granules in the same cell. The result of AB-S staining was obviously affected by fixation. The ultrastructure of chick mast cells was described. Internal large granules had a variable morphology; some higher or lower electron density with a homogeneous appearance; some were finely granular; some had a mottled appearance, and a few showed a reticular structure. The distribution of mast cells varied. The proventriculus was the most abundant in mast cells among the organs examined. Only one type of mast cell was found in the chick digestive tract. The fixation, staining and the ultrastructure of chick mast cell granules were discussed.

Animals↗
PubMed1991

Repetitive impulse activity potentiates spontaneous acetylcholine secretion at developing neuromuscular synapses.

The effects of presynaptic impulse activity on the transmitter secretion at developing neuromuscular junctions were examined in Xenopus nerve-muscle cultures. Repetitive suprathreshold stimulation of the presynaptic neuron results in marked potentiation of spontaneous synaptic activity, as shown by whole-cell voltage-clamp recording of synaptic currents in the postsynaptic muscle cell. Our results are consistent with the notion that synaptic efficacy of the developing synapse is potentiated by the presence of electrical activity. Such activity-dependent synaptic modulation enables the early neuronal activity to play a regulatory role during the maturation of synaptic connections.

Acetylcholine↗
PubMed1991

[Rational close planting in raising the seedlings of Panax quinguefolium linn].

It has been found that the effect of planting density is hardly noticeable for one-year-old seedlings, but very apparent for 2-year-old ones. With the increase of planting density, the leaf area gets smaller, stem higher, and root thinner and shorter. The larger the planting density. The smaller the dry weights of canopy and root and the root-canopy ratio. It is thus advocated that rational planting densities be selected according to the proper cultivation systems.

Panax↗
PubMed1991

[Molecular genetics of phenylketonuria in Orientals--linkage disequilibrium between a termination mutation and haplotype 4 of the phenylalanine hydroxylase gene].

Phenylketonuria (PKU) is a common metabolic disorder among Chinese, with a prevalence of about 1 in 16,500 births. This frequency is very similar to that among Caucasians. Individual exons of the phenylalanine hydroxylase (PAH) gene with flanking introns were amplified by the polymerase chain reaction and cloned into M13 for sequence analysis. An Arg111-to-Ter111 mutation was identified in exon 3 of the PAH gene in a Chinese PKU patient. The mutation is in linkage disequilibrium with the mutant haplotype 4, most prevalent among Orientals. The mutation accounts for about 10% of Chinese PKU alleles and is not found in Caucasians, demonstrating that independent mutational events occurred in the PAH locus after racial divergence.

Asian People↗
PubMed1991

The role of phosphoinositide turnover in mediating the biphasic effect of angiotensin II on renal tubular transport.

Our previous studies have shown that angiotensin II (Ang II) has a dose-dependent biphasic effect on bicarbonate and sodium transport and 4-beta-phorbol-12-myristate-13-acetate can simulate the stimulatory effect of Ang II on Na+/H+ exchange in the proximal convoluted tubules (PCT) of the rat kidney. This study was designed to further investigate the possible role of phosphoinositide turnover in mediating the biphasic effect of Ang II. Rat PCT was perfused in vivo with Ringer's solution containing [3H]inulin as a volume marker. Bicarbonate flux (JHCO3) was determined by total CO2 changes between the collected fluid and the original perfusate as analyzed by microcalorimetry. Luminal perfusion with 10(-11) M Ang II or 10(-8) M 4-beta-phorbol-12-myristate-13-acetate stimulated both fluid reabsorption (JV) and JHCO3, these effects can be blocked by 2 x 10(-4) M 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate (TMB-8), a blocker of intracellular calcium mobilization. Interestingly, Ang II at 10(-9) M or 2 x 10(-4) M TMB-8 have no effect on JV or JHCO3 individually. However, JV and JHCO3 significantly decreased when PCT were perfused simultaneously with 10(-9) M Ang II and 10(-4) M 1-(5-isoquinolinesulfonyl)-2-methylpiperazine; whereas JV and JHCO3 significantly increased when PCT were perfused with 10(-9) M Ang II and 2 x 10(-4) M TMB-8 together. These results suggest that PKC and intracellular calcium play a critical role in mediating the biphasic effect of Ang II on bicarbonate and sodium transport in PCT.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1991

Identification of a novel phenylketonuria (PKU) mutation in the Chinese: further evidence for multiple origins of PKU in Asia.

A novel mutation has been identified in the human phenylalanine hydroxylase (PAH) gene of a Chinese patient with classical phenylketonuria (PKU). It is a single base transition of G to A at the last base in intron 4 of the gene, which abolishes the 3'-acceptor site of the intron. Population screening indicates that this mutation constitutes about 8% of all PKU chromosomes in Chinese but is absent in Japanese and Caucasian PKU patients. It is prevalent in southern China but rare in northern China, providing additional evidence that there were multiple founding populations of PKU in east Asia.

Alleles↗
PubMed1990

Kinetics and thermodynamics of oxygen, CO, and azide binding by the subcomponents of soybean leghemoglobin.

Leghemoglobin shows extreme high affinity behavior in the binding of both oxygen and CO. We have determined the temperature dependence of the rate constants for ligation of oxygen and CO and from these data the thermodynamics (delta G0, delta H0, delta S0) of ligation for the purified components of soybean leghemoglobin. X-ray crystallography has shown that the heme cavity can easily accommodate ligands the size of nicotinate, and analysis of extended x-ray absorption fine structure data has shown that the Fe atom is in the mean plane of the heme in the leghemoglobin-CO complex. Ligation of oxygen and CO are in accord with this picture in that the Ea for oxygen binding is that expected for a diffusion controlled reaction and delta S0 for the ligation of both CO and oxygen is consistent with the simple immobilization of the ligand at the Fe, with no evidence for significant conformational changes in the protein or changes in solvation. At 20 degrees C the rate constants for oxygen and CO binding vary by 26-44% among the eight leghemoglobin components. For azide binding the variation is a factor of 2. These variations appear to arise from amino acid substitutions outside either the heme cavity or the two major paths for ligand entry to the heme. The distribution of leghemoglobin components varies with the age of the soybean nodule during the growing season. The changes in composition alone, however, would only allow the concentration of free oxygen to vary by about 3%. This finding calls into question models that ascribe a significant functional role to changes in the distribution of leghemoglobin components in regulating oxygen concentration in the nodule.

Azides↗
PubMed1990

Breast tumor radioimmunodetection with a 111In-labeled monoclonal antibody (MA5) against a mucin-like antigen.

Monoclonal antibody MA5 recognizes a determinant displayed on high molecular weight antigens associated with secretory and malignant breast epithelial cells. MA5 reactivity with greater than 95% of primary and metastatic breast tumors, surface expression of the antigen, as well as its ability to localize within breast tumor xenografts prompted this initial study to determine the efficacy of MA5 to localize breast tumors by radioimmunoscanning. A total of 17 patients was monitored, each receiving 2 mg of purified MA5 labeled with 5 mCi of 111In. Some patients also received 3 or 18 mg of unlabeled carrier antibody (MA5); no serious allergic reactions were noted. Primary tumors, bone lesions, soft tissue recurrences, and lung metastases greater than 3 cm in diameter were detectable, whereas only one lesion (hilar node) less than 3 cm was localized. Significant antibody accumulation was noted in the liver and less significant uptake in the spleen and bone. The extensive fibrosis and poor vascularization of breast tumors may partly explain the limited sensitivity obtained thus far. The imaging results obtained with MA5 are compared with other antibodies which we show recognize the same antigens.

Antibodies, Monoclonal↗
PubMed1990

Concentration/response relations for the multiple antiarrhythmic actions of sotalol.

Sotalol, one of the first beta-receptor antagonists synthesized, is a promising investigational agent with remarkable efficacy for treatment of patients with ventricular and supraventricular arrhythmias. Unlike other beta blockers, sotalol also possesses class III antiarrhythmic action, evidenced by prolongation of the myocardial action potential duration. This additional action probably accounts for the greater antiarrhythmic efficacy of sotalol compared with other beta blockers. Sotalol's class III antiarrhythmic action becomes apparent at concentrations higher than those necessary for significant beta-receptor antagonism, both in vitro and in human subjects. In a study correlating dosage and antiarrhythmic response with prolongation of rate-corrected QT (QTc) (a measure of class III action) and the degree of beta-receptor blockade (assessed by the reduction of the maximal exercise-induced heart rate), 11 of 17 patients had an antiarrhythmic response. Eight of these 11 responders had been unresponsive to conventional beta-receptor antagonists. The plasma concentration associated with significant QTc prolongation (2.55 micrograms/ml) was found to be much greater than that associated with 50% reduction in maximal slowing of heart rate (0.8 micrograms/ml). As with other beta-receptor antagonists, the activities of sotalol's 2 stereoisomers differ, with the I-isomer having far more beta-blocking activity. However, both isomers have equal class III antiarrhythmic activity. When increasing doses of the d-isomer of sotalol (50 to 400 mg every 12 hours) were evaluated in patients with chronic ventricular arrhythmias, arrhythmia frequency was suppressed greater than 80% in 3 patients and 50% in 1 patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmias, Cardiac↗
PubMed1990

Molecular genetics of PKU in eastern Europe: a nonsense mutation associated with haplotype 4 of the phenylalanine hydroxylase gene.

Phenylketonuria (PKU) is a genetic disorder secondary to a deficiency of hepatic phenylalanine hydroxylase (PAH). Several mutations in the PAH gene have recently been reported, and linkage disequilibrium was observed between RFLP haplotypes and specific mutations. A new molecular lesion has been identified in exon 7 of the PAH gene in a Hungarian PKU patient by direct sequencing of PCR-amplified DNA. The C-to-T transition causes the substitution of Arg243 to a termination codon, and the mutant allele is associated with haplotype 4 of the PAH gene. The mutation is present in two of nine mutant haplotype 4 alleles among Eastern Europeans and is not present among Western Europeans and Asians. The rarity of this mutant allele and its restricted geographic distribution suggest that the mutational event occurred recently on a normal haplotype 4 background in Eastern Europe.

Alleles↗
PubMed1990

Time- and dose-dependent effects of protein kinase C on proximal bicarbonate transport.

Activation of protein kinase C has been shown to cause both stimulation and inhibition of transport processes in the brush-border membrane and renal tubule. This study was designed to examine the dose-response nature and time-dependent effect of 4 beta-phorbol-12-myristate-13-acetate (PMA) on the rates of bicarbonate absorption (JHCO3) and fluid absorption (Jv) in the proximal convoluted tubule (PCT) of rat kidney. Bicarbonate flux was determined by total CO2 changes between the collected fluid and the original perfusate as analyzed by microcalorimetry. Luminal perfusion of PMA (10(-10) approximately 10(-5) M) within 10 min caused a significant increase of JHCO3 and Jv. A peaked curve of the dose response was observed with maximal effect at 10(-8) M PMA on both bicarbonate and fluid reabsorption, which could be blocked completely by amiloride (10(3) M) and EIPA (10(-5) M). On the other hand, with an increase of perfusion time beyond 15 min. PMA (10(-8) and 10(-6) M) could inhibit JHCO3 and Jv. Amiloride (10(-3) M) or EIPA (10(-5) M) significantly inhibits JHCO3 and Jv, while there is no additive effect of PMA and amiloride or EIPA on PCT transport. An inactive phorbol-ester, 4 alpha-phorbol, that does not activate protein kinase C, had no effects on JHCO3 and Jv. Capillary perfusion of PMA (10(-8) M) significantly stimulate both JHCO3 and Jv; however, PMA did not affect glucose transport from either the luminal side or basolateral side of the PCT. These results indicate that activation of endogenous protein kinase C by PMA could either stimulate or inhibit both bicarbonate and fluid reabsorption in the PCT dependent on time and dose, and these effects are through the modulation of Na+/H+ exchange mechanism.

Amiloride↗
PubMed1990

Cholinergic effect on rat proximal convoluted tubule.

The effect of cholinergic agents on proximal tubular absorption of bicarbonate and fluid were examined to investigate the possible role of the cholinergic receptor in the regulation of renal function. Proximal convoluted tubule (PCT) and peritubular capillaries were perfused with bicarbonate-Ringer's solution containing radioactive inulin. Bicarbonate (total CO2) was determined by microcalorimetry. The rates of bicarbonate absorption (JHCO3) and fluid absorption (Jv) were 143.3 +/- 7.2 pEq/min.mm and 2.52 +/- 0.23 nl/min.mm, respectively. Addition of carbachol (10(-8) M) to the capillary perfusate reduced JHCO3 by 17% and Jv by 32%. A higher dose of carbachol (10(-6) M) did not further inhibit JHCO3 or Jv. Simultaneous perfusion of atropine (10(-5) M) together with carbachol (10(-8) M) abolished the inhibitory effect of carbachol on PCT transport. Atropine itself, however, had no effect on PCT transport. The inhibitory effect of carbachol was also diminished by lanthanum chloride (10(-4) M). Carbachol (10(-6) M) had no effects from the luminal side. W-7, a calmodulin antagonist, inhibited carbachol-induced effects. Ionophore A-23187 also inhibited Jv and JHCO3. However, there was no additive effect when A-23187 and carbachol were combined in the capillary perfusate. These results suggest that there are functional cholinergic receptors on the basolateral side of the PCT that can regulate JHCO3 and Jv. Calcium influx may play a role in mediating the cholinergic effects on PCT transport.

Absorption↗
PubMed1990

Interstitial purine metabolites during regional myocardial ischemia.

The purpose of this study was to determine the changes in cardiac interstitial fluid (ISF) purine metabolites during 90 min of regional myocardial ischemia. To collect ISF metabolites and measure local coronary blood flow (CBF), cardiac microdialysis probes were implanted into the left anterior descending artery (LAD) and left circumflex artery (LC) perfused myocardium of chloralose-urethane anesthetized dogs (n = 7). Regional ventricular wall thickness was measured in the LAD and LC perfused regions with sonomicrometric crystals, using systolic wall thickening (SWT) as an index of regional ventricular function. Regional myocardial ischemia, produced by occlusion of the LAD, resulted in a decrease in CBF (hydrogen clearance) from 77.3 +/- 12.4 to 10.9 +/- 4.4 ml/min/100 g (P less than 0.05), and systolic wall thinning (control SWT = 15.5 +/- 2.2%; ischemic SWT = -6.8 +/- 1.7%). ISF adenosine was transiently elevated in the ischemic region, obtaining a maximum sixfold increase after 15 min of ischemia. Inosine, hypoxanthine, and to a lesser extent xanthine, composed the majority of metabolites which accumulated in the ISF of the ischemic region, accounting for greater than 95% of the total purine metabolites in the ISF after 20 min of ischemia. Despite the marked increase in ISF inosine, hypoxanthine, and xanthine levels, ISF uric acid levels did not increase in the ischemic region. Although CBF and SWT did not change in the nonischemic LC perfused area, there were small transient increases (two- to fourfold) in ISF adenosine, inosine, and hypoxanthine levels. In summary, these data demonstrate that purine metabolites accumulate rapidly in the ISF during myocardial ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1990

All-trans retinoic acid stimulates growth and extracellular matrix production in growth-inhibited cultured human skin fibroblasts.

All-trans retinoic acid was examined for effects on human dermal fibroblast proliferation and for effects on fibroblast production and expression of non-collagenous and collagenous components of the extracellular matrix in vitro. Fibroblast proliferation was blocked when the cells were cultured in the presence of a serum-free culture medium containing epidermal growth factor, hydrocortisone, insulin, ethanolamine, phosphoethanolamine, and bovine pituitary extract as growth supplements and 0.15 mM Ca++. This level of extracellular Ca++ is lower than that needed to support fibroblast growth. Under these conditions, growth was stimulated by all-trans retinoic acid. Proliferation was also stimulated in the same basal medium without the growth supplements. Growth-promoting concentrations of all-trans retinoic acid ranged from 0.5-2.0 micrograms/ml (1.7-6.6 X 10(-6) M). Stimulation of proliferation was not seen at higher or lower concentrations. Concentrations of all-trans retinoic acid that stimulated proliferation also induced increased production of fibronectin as indicated by biosynthetic labeling/immunoprecipitation and by enzyme-linked immunosorbent assay. Increased production was associated with increased staining for fibronectin in the extracellular matrix. Increased production of two other non-collagenous extracellular matrix component, i.e., thrombospondin and laminin, also occurred in all-trans retinoic acid-treated cells. At 0.5 micrograms/ml, all-trans retinoic acid also stimulated production of type I collagen by the dermal fibroblasts, but at higher concentrations (2.5 micrograms/ml) production of type I collagen was inhibited. These data indicate that all-trans retinoic acid can induce changes in dermal fibroblasts in vitro (i.e., increased proliferation and extracellular matrix production) that mimic the major changes seen in the dermis after topical treatment with this agent.

Cell Division↗
PubMed1990

Missense mutations associated with RFLP haplotypes 1 and 4 of the human phenylalanine hydroxylase gene.

We report missense mutations associated with haplotype 1 and haplotype 4 alleles of the human phenylalanine hydroxylase (PAH) gene. Individual exon-containing regions were amplified by polymerase chain reaction from genomic DNA of a PKU patient who was a haplotype 1/4 compound heterozygote. The amplified DNA fragments were subcloned into M13 for sequence analysis. Missense mutations were observed in exons 5 and 7, resulting in the substitution of Arg by Gln at residues 158 and 261 of the enzyme, respectively. Expression analysis in heterozygous mammalian cells after site-directed mutagenesis demonstrated that the Arg158-to-Gln158 mutation is a PKU mutation, whereas the Arg261-to-Gln261 mutation is apparently silent in the assay system. Hybridization analysis using allele-specific oligonucleotide probes demonstrated that the Arg158-to-Gln158 mutation is present in two of six mutant haplotype 4 alleles among the Swiss and constitutes about 40% of all mutant haplotype 4 alleles in the European population. The mutation is not present in normal alleles or in any mutant alleles of other haplotypes. The results provide conclusive evidence that there is linkage disequilibrium between mutation and haplotype in the PAH gene and that multiple mutations have occurred in the PAH gene of a prevalent haplotype among Caucasians.

Base Sequence↗
PubMed1990

Recurrent mutation in the human phenylalanine hydroxylase gene.

We report the identification of a missense mutation of Glu280 to Lys280 in the phenylalanine hydroxylase (PAH) gene of a phenylketonuria (PKU) patient in Denmark. The mutation is associated with haplotype 1 of the PAH gene in this population. This mutation has previously been found in North Africa, where it is in linkage disequilibrium with haplotype 38. While it is conceivable that this mutation could have been transferred from one haplotype background to another by a double crossover or gene conversion event, the fact that the mutation is exclusively associated with the two different haplotypes in the two distinct populations supports the hypothesis that these two PKU alleles are the result of recurrent mutations in the human PAH gene. Furthermore, since the site of mutation involves a CpG dinucleotide, they may represent hot spots for mutation in the human PAH locus.

Alleles↗