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Biomedical subjects

T C Wang

Publications and source records attributed to T C Wang.

At least 127 records · Page 7Linked to original sources
PubMed1994

Delay of the excision of UV light-induced DNA adducts is involved in the coclastogenicity of UV light plus arsenite.

Chromatid exchanges and chromatid breaks were synergistically increased by a 2-h post-treatment with arsenite (VS treatment) but not with arabinofuranosyl cytosine (VA treatment) of UV-irradiated late-G1 Chinese hamster ovary cells. In order to determine the mechanism of this UV-arsenite coclastogenicity, we have compared the effects of arsenite and arabinofuranosyl cytosine on the generation of DNA strand breaks in UV-irradiated cells by alkaline elution and alkaline sucrose sedimentation. Only very small numbers of DNA breaks were detected immediately after VS treatment, however the breaks in parental strands increased as the cells reached mitosis in drug-free medium, whereas a large number of breaks were detected immediately after VA treatment but the breaks decreased thereafter. By labelling the newly synthesized DNA, we have also shown that the VS-treated cells had more breaks in daughter strands than the VA-treated cells at the time of reaching mitosis. The effect of a 2-h post-treatment with arsenite on the excision of UV-induced DNA adducts was further investigated by using the exponentially growing cells. The results confirmed that very low amount of breaks was detectable immediately after VS treatment, however the amount of breaks increased upon the removal of arsenite. Therefore, the breaks in the daughter strands of VS-treated cells may come from DNA replication using templates containing unexcised adducts, or using broken templates. It is conceivable that gaps in the overlapping regions of parental and daughter strands may result in chromatid breaks and that misreplication, because of unexcised adducts or gaps in the parental strands, may result in chromatid exchanges.

Animals↗
PubMed1994

Influences of alkylphenyl alpha-D-mannopyranosides on histamine release from rat peritoneal mast cells induced by concanavalin A.

The influence of mannose, glucose, galactose and their corresponding methyl and phenyl glycopyranosides, as well as a series of alkylphenyl alpha-D-mannopyranosides, on histamine release from rat peritoneal mast cells induced by concanavalin A was examined. Among the compounds tested, the inhibitory effects of compounds bearing a 2,6-dimethyl substituent were stronger than the others. The results suggest that the binding ability of phenyl alpha-D-mannopyranoside may be markedly enhanced by the introduction of a 2,6-dimethyl substituent into the benzene nuclei of aglycones.

Animals↗
PubMed1994

Anti-allergy actions of alkylphenyl alpha-D-mannopyranosides.

The inhibitory effects of alkylphenyl alpha-D-mannopyranosides on histamine release from rat peritoneal mast cells induced by an antigen-antibody reaction were examined. Among the compounds tested, 2,4,6-trimethylphenyl alpha-D-mannopyranoside exhibited the strongest inhibitory effect. Furthermore, the 2,4,6-trimethylphenyl alpha-D-mannopyranoside suppressed the Schultz-Dale reaction and 48 h homologous passive cutaneous anaphylaxis (PCA), suggesting that this compound may be a useful lead compound in the development of novel anti-allergy drugs.

Animals↗
PubMed1994

Inhibitory effects of (4-alkoxy-2, 3, 6-trimethylphenyl) glycopyranosides on histamine release induced by antigen-antibody reaction.

The inhibitory effects of newly synthesized 4-alkoxy-2, 3, 6-trimethylphenyl D-glycopyranosides on histamine release induced by antigen-antibody reaction were examined. Among the compounds tested, 4-hexoxy-2, 3, 6-trimethylphenyl alpha-D-mannopyranoside exhibited the strongest inhibitory effect. Furthermore, 4-hexoxy-2, 3, 6-trimethylphenyl alpha-D-glucopyranoside and alpha-D-galactopyranoside markedly inhibited antigen-induced histamine release, and their activities were more potent than those of the corresponding beta-anomers. These results suggest that these compounds may possess excellent anti-allergic activities.

Animals↗
PubMed1994

Synthesis of 4-alkoxyaryl beta-D-glucopyranosides and their inhibitory effects on histamine release from rat peritoneal mast cells induced by concanavalin A.

The inhibitory effects of newly synthesized 4-alkoxyaryl beta-D-glucopyranosides on histamine release from rat peritoneal mast cells induced by concanavalin A were examined. A plot of hydrophobicity (k') against inhibitory activity of the compounds showed a distinct maximum, and 4-decyloxy-2,3,6-trimethylphenyl beta-D-glucopyranoside was the most potent inhibitor among the tested compounds.

Animals↗
PubMed1994

Synthesis and anti lipid-peroxidation activity of hydroquinone monoalkyl ethers.

A series of hydroquinone monoalkyl ethers was synthesized and evaluated for anti lipid-peroxidation activity in rat liver microsomes. 4-Hexyloxy-2,3,6-trimethylphenol (9), having a low redox potential, as well as ascorbic acid exhibited the strongest anti lipid-peroxidation activity (IC50 = 4.2 x 10(-7) M). Structure-activity relationship studies demonstrated that the inhibitory effect of hydroquinone monoalkyl ethers on lipid peroxidation was increased by the acquisition of an optimum hydrophobicity and decreased by an insufficient or excessive hydrophobicity.

Animals↗
PubMed1994

Findings of anomalous pulmonary venous return using MRI.

This study represents a preliminary retrospective assessment of the value of spin-echo magnetic resonance imaging (MRI) in detecting and describing total or partial anomalous pulmonary venous return (APVR). MRI was performed in 21 cases of APVR; orthogonal planes were used in all. Of the 21 cases, 19 were classified as total APVR (TAPVR) and two were partial APVR (PAPVR). Of the 19 cases of TAPVR, seven supracardiac, nine cardiac, one infracardiac and two mixed type were noted. The detection rate of each pulmonary vein combined in all three planes was 57% in the right superior pulmonary vein (RSPV), 62% in the left superior pulmonary vein (LSPV), 76% in the right inferior pulmonary vein (RIPV), and 86% in the left inferior pulmonary vein (LIPV). The axial plane was most effective (RSPV: 38%; LSPV: 52%; RIPV: 71%; LIPV: 81%). The coronal plane offered a better detection rate than the axial plane in RSPV (43%) and additional information of bronchial and visceral situs. Imaging of the combined axial and coronal planes was sufficient to evaluate each individual pulmonary vein. The sagittal plane gave no additional information in this respect. Accurate identification of pulmonary venous confluence and anomalous pulmonary venous channel was 95% (20/21). Limitation of echocardiography and and angiocardiography makes cardiac MRI important in assessing pulmonary vein and pulmonary venous confluence. It obviates the need for invasive angiocardiography and is an important supplement to an inadequate echo.

Adolescent↗
PubMed1994

Blood pressure, circulating atrial natriuretic peptide and sodium excretion responses during acute saline infusion in patients with essential hypertension.

In order to examine whether changes in circulating atrial natriuretic peptide (ANP) and sodium excretion during saline infusion in patients with essential hypertension (EH) could be modulated by the severity of resting arterial blood pressure (BP), 30 subjects with EH and nine normotensive subjects were given 2 L of isotonic saline infusion at a rate of 500 mL/hour. Plasma ANP concentrations in EH increased significantly from 64.9 +/- 5.1 (mean +/- SEM) to 92.5 +/- 12.8 pg/mL at the first hour and peaked at the second hour. In normotensives, the increase of plasma ANP was not significant until the fourth hour of infusion. Hypertensive subjects sustained a greater percentage increment of mean BP (MBP) than normotensives at the end of infusion. Those with pre-saline MBP exceeding 107 mmHg (group A) exhibited a faster and greater rise in plasma ANP after saline loading than those having less than or equal to 107 mmHg (group B). The post-saline four-hour natriuresis was appreciably higher in group A than group B, while the percentage increment of MBP at the fourth hour was significantly greater in the latter as compared to normal controls. These results indicate that patients with higher basal arterial pressure attain a faster and greater ANP response following saline infusion than those with lower BP. This phenomenon may be responsible for the maintenance of short-term fluid-volume and BP homeostasis during acute sodium loading in established EH.

Adult↗
PubMed1994

Hepatocyte growth factor in transgenic mice: effects on hepatocyte growth, liver regeneration and gene expression.

Attention has recently been focused on hepatocyte growth factor as a major candidate factor in liver regeneration because it is the most potent known mitogen for hepatocytes in vitro. However, hepatocyte growth factor also displays diverse activities in vitro as scatter factor, as an epithelial morphogen, as a pluripotent mitogen and as a growth inhibitor. Consequently, we developed transgenic mice that expressed hepatocyte growth factor under the control of albumin regulatory sequences to examine its in vivo role in hepatocyte growth. Hepatocytes of these mice expressed increased levels of hepatocyte growth factor as an autocrine growth factor. Hepatocyte growth factor was a potent stimulus for liver repair; the livers of hepatocyte growth factor-transgenic mice recovered completely in half the time needed for their normal siblings after partial hepatectomy. This transgenic model also enabled us to study the chronic effects of hepatocyte growth factor expression. During several months of observation, the labeling index of hepatocytes in albumin-hepatocyte growth factor mice was doubled, and liver DNA content was increased compared with that in wild-type mice. To identify intermediate signaling pathways for hepatocyte growth factor that might regulate this increased growth response, we examined transgenic mice for changes in expression of genes that are known to be regulated during liver regeneration. We found that levels of c-myc and c-jun mRNA were increased in the hepatocyte growth factor-transgenic mice. In additional experiments the increased c-myc expression was the consequence of increased transcription rates as seen in nuclear run-on and myc-CAT reporter gene experiments. We conclude that hepatocyte growth factor increases growth and repair processes when expressed for long periods in the liver and that c-myc and c-jun may be important intermediaries in the hepatocyte growth response caused by hepatocyte growth factor.

Animals↗
PubMed1993

Cosuppression of recF, recR and recO mutations by mutant recA alleles in Escherichia coli cells.

The ability of recA718, recA720, recA730, recA750 and two known recA(Srf) alleles (recA2020 and recA441) to act as suppressors of recF, recR and recO mutations was examined by studying their UV radiation sensitivity in uvrA cells of Escherichia coli. With the exception of recA718, all the mutant recA alleles examined were able to suppress the UV radiation sensitivity caused by recF, recR or recO mutations, but not by the recB mutation. The suppression by recA750 was minimal. The suppression of recF, recR and recO mutations by other recA alleles was more pronounced, but none of them could exert full suppression. Heterozygotes containing a mutant recA allele (recA720, recA730 or recA441) and recA2020 (or recA803, another known recA(Srf) allele) failed to produce any additive or synergistic suppression of recF, indicating that these suppressors did not use different mechanisms for their suppression. Similar to a requirement of recJ+ in the suppression of recF, the suppression of recR and recO mutations by mutant recA alleles also required recJ+. The similar phenotypes conferred by recF, recR, and recO mutations and the observations that a number of mutant recA alleles can cosuppress these three mutations suggest that the recF, recR and recO gene products may function together as a complex.

Alleles↗
PubMed1993

Factors affecting zero background frequency of sister-chromatid exchange in mosquito cells.

A background level of sister-chromatid exchange (SCE) is found in mammalian cells. However, in the somatic cells of Drosophila melanogaster, there was no spontaneous SCE if a minimum concentration of bromodeoxyuridine (BrdU) was used. In this communication we report that in a mosquito (Aedes albopictus) cell line (C6/36), some cells also have no background SCE (0-SCE). Subclones of high (44%) or low (12%) frequency of 0-SCE cells were obtained, but none of them contained 100% 0-SCE cells. Increasing frequency of SCE/cell concomitant with decreasing frequency of 0-SCE cells was observed by raising the BrdU concentration in the culture medium during the first cell cycle, culturing cells at lower density and depleting reduced glutathione (GSH) with buthionine sulfoximine. Since these mosquito cells contain much higher level of GSH than Chinese hamster ovary (CHO) cells, and feeding cells with BrdU increased GSH in mosquito cells but decreased GSH in CHO cells, we speculate that GSH may play a role in the low or non-existent background SCE and in the high resistance to many DNA damaging agents of mosquito cells.

Aedes↗
PubMed1993

Pancreatic gastrin stimulates islet differentiation of transforming growth factor alpha-induced ductular precursor cells.

Gastrin is transiently expressed in fetal islets during a critical period of their development from protodifferentiated islet precursors in fetal pancreatic ducts. To examine the possible role of gastrin as an islet cell growth factor, postnatal islet growth was studied in transgenic mice which overexpress gastrin and TGF alpha in their pancreas. Overexpression of a TGF alpha transgene causes metaplastic ductules containing numerous insulin expressing cells that resemble protodifferentiated precursors of the fetal pancreas. However, islet mass of the TGF alpha transgenic mice was not increased. Pancreatic overexpression of gastrin from a chimeric insulin/gastrin transgene transcribed from the insulin promoter markedly decreased the TGF alpha-stimulated increase in pancreatic duct mass. Furthermore, pancreatic coexpression of both gastrin and TGF alpha significantly increased islet mass in mice expressing both transgenes. These findings indicate that TGF alpha and gastrin can act synergistically to stimulate islet growth, although neither peptide alone is sufficient. Islet growth may possibly be stimulated through gastrin promoting the differentiation of insulin-positive cells in the TGF alpha-induced metaplastic ducts. This transgenic study suggests that islet neogenesis can be reactivated in the ductular epithelium of the adult pancreas by local expression of two growth factors, gastrin and TGF alpha.

Animals↗
PubMed1993

[Giant cystic hygroma: a case report].

Cystic hygromas are congenital malformations of the lymphatic system appearing as single or multiloculated, fluid-filled cavities found mainly in the neck and axilla region. Antenatal ultrasound examination done in this case showed a suspicious giant cystic mass over the neck and chest area. At birth, the mass turned out to be a rare giant cystic hygroma measuring about 25cm x 26cm covering neck, anterior chest, axilla, proximal right upper limb, upper abdomen and upper back area. Because of some compromise to the infant's breathing, an emergency resection was done, and the infant tolerated the procedure well. Pathology report confirmed the diagnosis.

Adult↗
PubMed1993

Acute acalculous cholecystitis.

To demonstrate the importance of early detection and diagnosis of acute acalculous cholecystitis, 34 patients with this disease, were studied retrospectively. Twenty patients had a delay between the onset of symptoms and operative intervention, exceeding 48 hours; five of them were found to have a perforated gallbladder during operation; however, no such complication was encountered in the 14 patients who underwent surgical treatment within 48 hours of onset. Sixteen patients had post-operative complications, and four patients who died produced in a mortality rate 11% (4/34). Three mortality cases had coexisting cardiovascular disease and the operation was also delayed for more than 48 hours.

Acute Disease↗
PubMed1993

Primary malignant lymphoma of the breast: report of two cases with literature review.

We report two cases of malignant lymphoma of the breast. Extensive investigation on both, demonstrated only a neoplastic lesion confined within the breast. One was managed by local excision, systemic chemotherapy and adjuvant radiotherapy; the other was managed by a modified radical mastectomy, adjuvant radiotherapy and therapeutic chemotherapy. Both of them achieved complete remission 3 years and 1.5 years respectively after management.

Adult↗
PubMed1992

Similar-sized daughter-strand gaps are produced in the leading and lagging strands of DNA in UV-irradiated E. coli uvrA cells.

The nascent DNA synthesized after UV irradiation contained discontinuity, i.e., daughter-strand gaps. The sizes of these gaps produced in the leading and lagging strands of UV-irradiated Escherichia coli cells were determined by using strand-specific DNA probes. The DNA isolated from irradiated uvrA delta(lac-pro) cells was hybridized with the 32P-labeled single-stranded DNA probes. After digestion with S1 nuclease, the sizes of the bound radioactive DNA fragments were determined by electrophoresis in an alkaline agarose gel. It was found that the average size of gaps produced in the leading strand was about 0.12 kb, whereas those produced in the lagging strand was slightly smaller than 0.12 kb. No gaps larger than 0.5 kb were detected.

Coliphages↗