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Biomedical subjects

T C Wang

Publications and source records attributed to T C Wang.

At least 145 records · Page 8Linked to original sources
PubMed1992

Hepatocyte growth factor inhibits growth of hepatocellular carcinoma cells.

Hepatocyte growth factor (HGF) is a potent mitogen for primary hepatocytes. Therefore, we examined HGF as a possible autocrine growth factor in hepatocellular carcinoma (HCC). We introduced an albumin-HGF expression vector into Fao HCC cells and transgenic mice. Expression of the albumin-HGF vector in Fao HCC cells inhibited their growth in vitro. In vivo, FaoHGF cells produced tumors that averaged 10% of the sizes of G418-resistant controls when transplanted into nude mice. In contrast, hepatocytes from transgenic mice expressing HGF grew more rapidly than did those from normal siblings. Further, growth of eight additional HCC cell lines was inhibited by the addition of recombinant HGF. Finally, of 35 tumor cell lines surveyed, only 6 cell lines expressed HGF mRNA, and no HCC cell line expressed HGF. Although HGF stimulates normal hepatocytes, it is a negative growth regulator for HCC cells.

Animals↗
PubMed1992

Freezing preservation of the mammalian cardiac explant. II. Comparing the protective effect of glycerol and polyethylene glycol.

We compared the cryoprotective ability of glycerol and polyethylene glycol (PEG) during freezing. Isolated rat hearts were flushed with one of three cardioplegic solutions (CP-14, CP-15, and CP-16), frozen at -1.4 degrees C, and reperfused after thawing to assess function. After 3 h freezing, cardiac output (CO) in CP-14-flushed hearts recovered to 58.1% of control. CP-16 (CP-14 with 5% PEG) improved CO to 77.5%. Five hours of freezing abolished recovery in CP-14 hearts, but CP-15 (CP-14 with 50 mM glycerol) and CP-16 hearts produced 40.0 and 49.0% CO, respectively. With 6 h freezing, CP-15 hearts did not recover, whereas CP-16 hearts recovered 37.5% CO. In CP-14 hearts frozen for 3 h, 37.4% of the tissue water was ice that increased to 44.7% with 5 h freezing. CP-15 and CP-16 hearts had 34.4 and 30.9% tissue ice, respectively, after 5 h freezing. Tissue water contents in CP-14 and CP-15 hearts (3.83 to 3.96 g H2O/g dry) were 14 to 24% higher than that in CP-16 hearts. Six hours of freezing elevated AMP and ADP contents and reduced ATP levels in CP-15 and CP-16 hearts. Total adenine nucleotide (TAN) content of CP-15 hearts was 72% of control, while that of CP-16 hearts was normal. In conclusion, both glycerol and PEG offered cryoprotection by reducing tissue ice formation. PEG was superior by reducing tissue ice content further via dehydration and by better preserving TAN content.

Adenine Nucleotides↗
PubMed1992

Reappraisal of electrical cure of atrioventricular nodal reentrant tachycardia--lessons from a modified catheter ablation technique.

A modified catheter ablation technique was studied prospectively in 29 patients with atrioventricular (AV) nodal reentrant tachycardia. A His bundle electrode catheter was used for mapping and ablation. Cathodic electroshocks (100-250 J) were delivered from the distal two electrodes (connected in common) of the His bundle catheter to the site selected for ablation. The optimal ablation site recorded the earliest retrograde atrial depolarization, simultaneous or earlier than the QRS complex, with absence of a His bundle deflection during AV nodal reentrant tachycardia. One additional electrical shock was delivered if complete abolition of retrograde VA conduction persisted for more than 30 min and AV nodal reentrant tachycardia was not inducible during isoproterenol and/or atropine administration. With a cumulative energy of 323 +/- 27 J and a mean of 2.3 +/- 0.5 shocks interruption or impairment of retrograde nodal conduction was achieved. Antegrade conduction, although modified, was preserved in 27 patients, with persistence of complete AV block in 2 patients. Two of the 27 patients still need antiarrhythmic agents to control tachycardia, the other 25 patients were free of tachycardia within a mean follow-up period of 13 +/- 2 months (range 7 to 20 months). Twenty-three patients received late follow-up electrophysiological studies (3-6 months after the ablation procedures), and the AV nodal function curves were classified into 4 types. The majority of the patients (15/23) had loss of retrograde conduction. Among the 8 patients with prolongation of retrograde conduction, 4 patients still had antegrade dual AV nodal property but all without inducible tachycardia. In conclusion, preferential interruption or impairment of retrograde conduction was the major, but not the sole, mechanism of electrical cure of AV nodal reentrant tachycardia.

Adult↗
PubMed1992

The transition from late G1 to early S phase is most vulnerable to the coclastogenic effect of ultraviolet radiation plus arsenite.

It has previously been reported that chromosome aberrations induced by ultraviolet (UV) radiation can be enhanced by treatment with sodium arsenite for 24 h post-irradiation. Using synchronized CHO-K1 cells, it has now been established that cells in the transitional stage from late G1 to early S phase are most vulnerable to the coclastogenic effect of treatment with UV radiation and arsenite. This result cannot be explained by the special vulnerability of cells in the late G1 to early S transition to UV clastogenicity, as the coclastogenic effects of UV and caffeine or UV and arabinofuranosylcytosine were detected when treating the mid-S but not late-G1 or G2 phase cells.

Animals↗
PubMed1992

A comparative study of a modified catheter-mediated direct current and radiofrequency ablation on atrioventricular junction.

Conventional His-bundle ablation, performed at the site with the largest His-bundle potential, displays a high incidence of a new right bundle branch block with loss of pacemaker escape. Damage to the perinodal atrial area may decrease the injury to the His-bundle, such that the escape pacemaker activity with a narrow QRS complex is produced. This study reports data from 25 patients with drug-refractory atrial tachyarrhythmias. Nine patients (group I) received radiofrequency (RF) ablation of the atrioventricular junction (AVJ). General anesthesia was not necessary in group I patients. During a mean follow-up period of 10 months, a complete AV block persisted in 5 patients, and a first degree AV block persisted in 2 patients; these patients were asymptomatic and did not require treatment with antiarrhythmic agents. A successful direct-current (DC) ablation was performed in one of the patients with an unsuccessful RF lesion, producing a new right bundle branch block (RBBB). Sixteen patients (group II) received DC ablation of the AVJ. During a mean follow-up period of 20 months, a complete AV block persisted in 9 patients, a first degree AV block was produced in 7 patients, and a new RBBB occurred in 2 patients. Fifteen patients (94%) were asymptomatic without administration of antiarrhythmic agents. Complications, including nonsustained ventricular tachycardia (1 patient) and pericarditis (1 patient), occurred immediately after ablation in group II. Myocardial injury, reflected by creatine kinase-MB isoenzyme, was higher in group II than in group I (25 +/- 2 vs 10 +/- 1 IU/l). We conclude that (1) catheter-mediated RF ablation of the AV junction is safer than DC ablation, (2) a majority of patients with drug-refractory atrial tachyarrhythmias can be successfully treated with RF ablation and (3) failure to achieve AV junction ablation with RF does not mitigate against successful application of DC ablation.

Adult↗
PubMed1992

Thyroglossal duct cyst: an analysis of 92 cases.

From 1983 to 1989, ninety-two in hospital cases of surgically treated thyroglossal duct cysts were reviewed. 4 patients (4%) were found to have metaplastic changes of the lining epithelium. Recurrence and the potential for malignancy are two main problems in the treatment of thyroglossal duct cyst. We advocate the Sistrunk procedure to be the choice of surgical treatment for thyroglossal duct cyst.

Adolescent↗
PubMed1991

Effect of rec mutations on viability and processing of DNA damaged by methylmethane sulfonate in xth nth nfo cells of Escherichia coli.

The role of recombination genes in the processing of DNA damaged by methlymethane sulfonate (MMS) was examined in an xth nth nfo strain of Escherichia coli K-12. Introduction of a recQ mutation did not increase the cell's sensitivity to MMS treatment. The presence of recF, recJ or recN mutation slightly increased the cell's sensitivity to MMS treatment. The introduction of recA or recB mutation into the cells led to inviability. Taken together, we suggest that replication of DNA containing apurinic/apyrimidinic (AP) sites in vivo will lead to the formation of secondary lesions. The repair of these secondary lesions requires the function of recA and recB genes, but does not appear to require recF, recJ, recQ or recN genes.

DNA Damage↗
PubMed1991

Freezing preservation of adult mammalian heart at high subzero temperatures.

The present study adapted the overwintering strategy employed by freeze-tolerant amphibians and reptiles to freeze-preserve the isolated rat heart. The heart was flushed with a cardioplegic solution and supercooled to -1.2 and -3 degrees C. Then freezing was induced by inoculation of ice crystal. The viability of the heart explant was assessed after reanimation by the isolated working heart perfusion. There was no recovery of function in hearts flushed with solution containing 0.28 mM CaCl2. Lowering the concentration of CaCl2 to 0.15 mM, however, rendered good functional return. Furthermore, inclusion of 50 mM glycerol in the flush solution dramatically improved functional preservation. Under the best conditions defined here, the recoveries of aortic flow, coronary flow, cardiac output, systolic pressure, and work in hearts stored at -1.2 degrees C for 3 h were 72.8 +/- 6.8, 87.2 +/- 4.2, 77.6 +/- 5.4, 83.4 +/- 2.8, and 66.6 +/- 5.9% (mean +/- SEM, n = 8) of the unstored control levels, respectively. The myocardial ice content was 18.6 +/- 5.4% (n = 5) of tissue water. Prolonging the storage time to 5 h increased the ice content to 45.3 +/- 8.1% and reduced the recovery of cardiac output to 23 +/- 11% of the control value (mean +/- SEM, n = 5). Hearts frozen at -3 degrees C for 1.5 h showed 29.4 +/- 8.7% (n = 3) of control cardiac output during reperfusion. This novel approach may provide an opportunity to advance our knowledge about freezing preservation of not only the heart but other solid organs as well.

Animals↗
PubMed1991

Practice patterns and costs of hospitalization for upper gastrointestinal hemorrhage.

We conducted an observational study at three hospitals in Boston to examine the patterns of practice and the costs involved in the medical management of noncirrhotic, upper gastrointestinal bleeding. A total of 111 patients were identified and studied: 42 from hospital 1, 38 from hospital 2, and 31 from hospital 3. There were no significant differences in the management of the patients, except for the more frequent use of upper gastrointestinal radiography at hospital 3 and the more frequent use of cimetidine at hospital 2. Only a small percentage (3-7%) of patients required surgery, and overall mortality (0-8%) was low. The average cost of hospitalization, determined by using the New England Medical Center cost model, was calculated for direct costs ($3,180). The majority of costs incurred were for hospital bed or intensive care unit stay (63%) and transfusion of blood products (14%), with costs for physicians' services (9%), endoscopy (2%), and upper gastrointestinal radiography (1%) accounting for only a small percentage. This study demonstrates remarkable similarity in practice patterns and resource utilization at three different hospitals and provides data on the actual costs involved in hospitalization for noncirrhotic, upper gastrointestinal hemorrhage.

Acute Disease↗
PubMed1991

Computed tomography of the brain in patients with serum prolactin levels over 200 ng/ml.

We reviewed the computed tomographic (CT) findings of the sella turcica in 26 patients with a serum prolactin level of over 200 ng/ml. The interval between the dates of CT examination and checking of the serum prolactin level were within 2 months. There were 24 nonpregnant women with a mean age of 30 years and 2 men with a mean age of 28.5 years. None of them were taking medication known to cause an elevation in serum prolactin levels. Surgery was performed on 8 patients with chromophobe adenomas of the pituitary gland: 6 of them were proven to have prolactin-secreting tumors (prolactinomas) after performing a special stain, and the remaining 2 patients, clinically diagnosed as prolactinomas, showed extremely high serum prolactin levels (3,200 and 2,251 ng/ml, respectively). CT studies showed that the height of the pituitary gland in the coronal sections were more than 7 mm in 15 cases (58%) and more than 10 mm in 13 cases (50%); focal bulging of the diaphragma sellae in 16 cases (62%); erosion of the sellar floor in 20 cases (77%); deviation of the pituitary stalk in 19 cases (73%); and abnormal attenuation or enhancement of the pituitary gland in 18 cases (69%). Three patients (12%) showed no evidence of any abnormal CT finding despite a hyperprolactinemic state of over 200 ng/ml. Six histologically proven cases (23%) of prolactinomas and chromophobe adenomas showed radiologic evidence of cavernous sinus invasion. We conclude that patients with a serum prolactin level higher than 200 ng/ml generally show significant changes in the sella turcica in CT.

Adenoma, Chromophobe↗
PubMed1991

CT myelography for differential diagnosis between intramedullary and intradural-extramedullary spinal tumors in the region of the conus medullaris.

We reviewed the myelograms and computed tomographic myelograms of 12 cases of intraspinal tumor with a "cupping sign" on the myelogram in the region of the conus medullaris from 1986 to 1988. There were 5 intramedullary tumors, 4 of them having an exophytic component, and 7 intradural-extramedullary tumors. The myelograms revealed that 4 of the 5 intramedullary tumors showed expansion and the outline of the conus medullaris was irregular, whereas 1 of the tumors showed smooth compression (crescent-shaped) and displacement of the conus medullaris. Six of the 7 intradural-extramedullary tumors showed smooth compression and displacement of the conus medullaris, while 1 of the tumors had caused expansion of the conus medullaris. Complete blockage of the passage of the contrast medium was noted in 3 of the 5 intramedullary tumors, while a partial block was noted in 3 of the 7 intradural-extramedullary tumors. Two of the 7 intradural-extramedulllary tumors showed an extradural tumor component, such as a dumb-bell tumor and a enlarged intervertebral neural foramen. Tumor calcification was noted in 1 of the 7 intradural-extramedullary tumors. Dural ectasia was noted in 2 of the 7 intradural-extramedullary tumors which were later proven to be neurofibromatosis. We conclude that smooth compression (crescent-shaped) and displacement of the conus medullaris, existence of an extradural tumor component, and eroded intervertebral neural foramina favor intradural-extramedullary tumors, while expansion and a conus medullaris with an irregular outline favors intramedullary tumors.

Adolescent↗
PubMed1990

Islet cell-specific regulatory domain in the gastrin promoter contains adjacent positive and negative DNA elements.

The gastrin gene is expressed in fetal pancreatic islet cells, but after birth expression is selectively repressed as the islets terminally differentiate. DNA transfection studies identified a cis regulatory domain between -108 and -76 in the gastrin promoter which controls gastrin transcription in islet cells. This cis regulatory domain comprises adjacent positive and negative elements. The negative element (-108 to -82) contains the sequence ATTCCTCT, which is also found in the negative element of the beta-interferon promoter. Gel retardation assays and DNase footprinting studies demonstrated that specific islet nuclear protein(s) bind to the gastrin negative element. In vivo competition studies demonstrated that the trans-acting factors which bind to this element specifically repress gastrin promoter activity in islet cells. Immediately downstream of the negative element lies a positive element (-82 CATATGG -76), which activates gastrin transcription in islet cells. The sequence of the positive element resembles the islet-specific enhancer elements of the insulin gene (CATCTGG/C). Gel mobility shift assays and in vivo competition studies indicate that this positive element activates the gastrin promoter by binding to the same islet cell transcription factor which binds enhancer elements in the rat insulin gene. The tandem organization of the negative and positive elements suggests that this regulatory domain may act as a switch controlling the transient transcription of the gastrin gene during fetal islet development.

Animals↗
PubMed1990

Effect of mucosal thickening near gastric carcinoma on the endoscopic diagnosis of malignancy.

Gastric mucosal thickening of variable degree occurs in the vicinity of gastric carcinomas and is possibly related to simultaneous tumor expression of epidermal growth factor and its receptor. Seventeen cases in which both endoscopic biopsy and subsequent resection for gastric carcinoma had been performed were studied to see if putative tumor-related mucosal thickening had an effect on endoscopic biopsy sensitivity. Biopsy fragment positivity rate was greater in cases with exophytic, protruding tumor masses (46.8 +/- 8.5%) than in all other cases (17.0 +/- 4.7%; P = 0.02). Thickness of nontumorous mucosa adjacent to carcinomas did not significantly affect the biopsy fragment positivity rate in cases with exophytic masses ("thin" subgroup, 51.0 +/- 16.2%; "thick" subgroup, 44.0 +/- 10.8%; P = 0.7) but did reduce the positivity rate significantly (P = 0.05) in ulcerative or infiltrative tumors without exophytic components ("thin" subgroup, 23.3 +/- 4.1%; "thick" subgroup, 8.4 +/- 2.1%). This reduction in biopsy sensitivity related to mucosal thickening occurring adjacent to nonprotuberant lesions may explain, at least in part, the variable rates of positive biopsies observed with gastric cancers.

Aged↗