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Biomedical subjects

J K Chen

Publications and source records attributed to J K Chen.

At least 91 records · Page 5Linked to original sources
PubMed1993

Affinity electrophoresis in multisectional polyacrylamide slab gels is a useful and convenient technique for measuring binding constants of aryl sulfonamides to bovine carbonic anhydrase B.

This paper describes convenient preparations of heterogeneous multisectional polyacrylamide slab gels and the protocols that use these gels to measure protein-ligand binding constants [using bovine carbonic anhydrase B (CAB) as a model system]. Unlike procedures for affinity electrophoresis using tube gels, all binding information concerning protein-ligand interactions was encoded in a single multisectional gel: the procedure involving for measuring binding constants required no postelectrophoresis manipulation of gels. Use of these types of gels improves the accuracy of affinity gel electrophoresis (AGE) by providing reliable internal protein standards. Binding constants measured by AGE agree with those determined in homogeneous solution by spectrophotometric measurements. This technique has been used to investigate the influence of the length of the spacer separating the ligand and the polyacrylamide backbone on the binding constants. Dissociation constants obtained using the affinity gels approach the values measured in free solution, when the spacer is sufficiently long (> or = 18 A); affinity ligands having short spacers give high apparent dissociation constants.

Animals↗
PubMed1993

Cyclic AMP-induced inhibition of collagen lattice contraction by fibroblasts may be attenuated by both cyclic AMP dependent and independent mechanisms.

The contraction of collagen lattices made with foreskin fibroblasts in medium containing 1% fetal bovine serum was inhibited by intracellular cyclic AMP-raising drugs including cholera toxin (CT), forskolin, and dibutyryl-cAMP. The inhibition by CT was attenuated by insulin, acidic fibroblast growth factor (aFGF), and transforming growth factor-beta (TGF-beta). All three peptide factors have previously been reported to promote collagen lattice contraction by arterial smooth muscle cells and/or fibroblasts. Incubation of cells suspended in collagen gels with CT and forskolin resulted in a transient rise of the intracellular cyclic AMP levels, which peaked at 2 hr and 30 min, respectively, after drug exposure. Cholera toxin-induced intracellular cyclic AMP increase was attenuated by TGF-beta, but not by aFGF and insulin, when added simultaneously. Thus, TGF-beta may attenuate CT's inhibition on collagen lattice contraction by attenuating CT-induced intracellular cyclic AMP increase, whereas the attenuation by insulin and aFGF on the inhibition of lattice contraction may be mediated by a cyclic AMP-independent mechanism.

Cells, Cultured↗
PubMed1993

Effects of different doses of norethisterone on ovarian function, serum sex hormone binding globulin and high density lipoprotein-cholesterol.

The ovarian effects of different doses of norethisterone (NET) were compared in 45 normally menstruating women in order to find the lowest effective dose of the Chinese NET "visiting pill". Subjects were randomly divided into 3 groups. Each subject in each group was taking 0.5, 1.5 or 3.0 mg per day from days 5 to day 18 of the cycle. Blood samples were taken on days 5, 8, 11, 14, 17, 20, 23, 26 and 29 of the cycle. Serum oestradiol (E2), progesterone (P), sex hormone binding globulin (SHBG), high density-lipoprotein cholesterol (HDL-C), and NET concentrations were measured. Ovulation, delayed ovulation, ovulation inhibition and follicular activity were classified by the analysis of the peripheral serum levels of sex hormones. Ovulation occurred in 7 women in the 0.5 mg group, in 2 women in the 1.5 mg group and in none of the 3.0 mg group. Mean serum SHBG levels were reduced progressively by 6.6% (Group 0.5), 15.5% (Group 1.5) and 23.4% (Group 3.0). There were no significant changes in HDL-C levels in any group. There was a significant correlation of mean serum NET concentrations with dose. The lack of complete inhibition of ovulation in most women in the 1.5 mg and 0.5 mg groups might suggest that the dose of NET required when used as a visiting pill could not be reduced below 3.0 mg.

Adult↗
PubMed1993

Stimulation or inhibition of A431 cell growth by EGF is directly correlated with receptor tyrosine kinase concentration but not with PLC gamma activity.

EGF-induced hydrolysis of phosphatidylinositol 4, 5, biphosphate was compared in A431 cells with respect to their growth response to EGF. A431 cells which express 4- to 5-fold more EGF receptors than A431-4 cells were growth inhibited, while A431-4 cells were growth stimulated by EGF within the same dose range. Treatment of A431 cells with EGF resulted in a 2-fold increase in cellular IP3 levels and the effect in A431-4 cells was not as obvious. In the presence of tyrosine kinase inhibitor coumaric acid (0.2 approximately 2 microM), A431 cell growth was stimulated, rather than inhibited, by EGF in a dose-dependent manner. In contrast, the stimulation of A431-4 cell growth by EGF was reduced under the same conditions. Furthermore, in the presence of coumaric acid (up to 0.5 microM), EGF-induced production of inositol phosphates in A431 cells was not obviously affected. Taken together, the results suggest that EGF-induced growth inhibition of A431 cells may be due to a quantitative changes of EGF-receptor tyrosine kinase activity in areas other than the recruitment and activation of phosphatidylinositol-specific phospholipase C gamma.

Carcinoma, Squamous Cell↗
PubMed1993

Nonresponsiveness of an SV40-transformed Balb/c-3T3 cell line to PDGF mitogenicity is correlated with an irreversible reduction in PDGF receptor number.

The effect of SV40 transformation on the mitogenic responsiveness of Balb/c-3T3 cells to platelet-derived growth factor was examined. The SV40 transformed cell line (SV40-3T3) did not require exogenous PDGF for growth in a serum-free medium containing insulin, transferrin and high density lipoprotein as macromolecular supplements. The SV40-3T3 cells were found to have undetectable PDGF-stimulated PDGF receptor autophosphorylation and markedly reduced PDGF binding. PDGF-induced PDGF receptor autophosphorylation and PDGF binding of the normal 3T3 cells were not reduced by incubation with conditioned medium from SV40 transformed cells; nor could PDGF binding to SV40-3T3 be increased by an 8-hour incubation with 0.5 mM suramin, a compound known to prevent the binding of PDGF to its receptor. These data suggest that SV40-3T3 cells do not produce PDGF in quantities that are sufficient to down regulate their PDGF receptor and suggest that the reduced PDGF responsiveness and PDGF receptor number in SV40-3T3 cells may be a reflection of a more permanent, perhaps genetic, alteration.

3T3 Cells↗
PubMed1993

[Imaging diagnosis of Budd-Chiari syndrome: report of 24 cases].

In 24 patients with Budd-Chiari syndrome age 15-66, 19 were men, and 5 women. The patients experienced abdominal pain, hepatomegaly, splenomegaly and ascites. Imaging examinations were carried out in all the patients (16 ultrasonography, 5 Doppler, 10 CT, 18 venography, and 4 MRI). Direct features of Budd-Chiari syndrome were striking reduction in caliber, complete absence or obstruction of hepatic veins, intrahepatic inferior vena cava, "comma-shaped" or curled-tubular intrahepatic collateral veins; indirect signs included hepatomegaly, splenomegaly and ascites, extrahepatic collateral veins. Ultrasonography,CT, MRI and venography were all useful in the diagnosis of patients with Budd-Chiari syndrome. It is suggested that ultrasonography is a non-invasive procedure and MRI is the best imaging procedure of choice in the evaluation of Budd-Chiari syndrome.

Adolescent↗
PubMed1993

Removal of renal cell carcinoma extending into the right atrium using cardiopulmonary bypass, profound hypothermia and circulatory arrest.

A 65-year-old man presented with renal cell carcinoma of the right kidney with a tumor thrombus extending up the vena cava to the right atrium. Cardiopulmonary bypass, profound hypothermia and total circulatory arrest were used to create a bloodless field for excision of the renal cell carcinoma and its tumor thrombus. Acute respiratory failure and deep jaundice developed after the operation and the patient was transferred to the intensive care unit for critical care. After respiratory therapy and nutritional support, the liver function was restored. The endotracheal tube was weaned one month later. The patient has had total resolution of all symptoms and there is no evidence of tumor recurrence of distant metastases after 6 months follow-up.

Aged↗
PubMed1993

[Comparison between electro-acupuncture with chlorpromazine and chlorpromazine alone in 60 schizophrenic patients].

60 schizophrenia patients were treated with electro-acupuncture and chlorpromazine therapy in comparison with chlorpromazine therapy alone, 30 patients for each group, and their curative effects evaluated according to the brief psychiatric rating scale (BPRS). The result showed the total curative effects of the two groups were similar. However, the marked effects appeared earlier in combined therapy than that of using chlorpromazine alone, less chlorpromazine was needed, hence displayed fewer side-effects.

Case-Control Studies↗
PubMed1992

Transplacental genotoxicity of triethylenemelamine, benzene, and vinblastine in mice.

Transplacental cytogenetic effects of triethylenemelamine (TEM), benzene, and vinblastine on maternal mice and their fetuses have been investigated using micronucleus and sister chromatid exchange (SCE) as genetic endpoints. CD-1 mice were treated on day 14 and 15 of gestation with TEM (0.125, 0.25, and 0.5 mg/kg), benzene (439,878, and 1,318 mg/kg), and vinblastine (0.5, 1, and 2 mg/kg) by intraperitoneal injection at 24 hr intervals, and sacrificed 40 hr after the first injection. Erythrocytic precursor cells in maternal bone marrow and fetal livers (2-4) from each pregnant mouse were used for the micronucleus and/or the SCE analyses. Significant dose-related increases in both micronuclei and SCE were found in maternal bone marrow and fetal liver following TEM treatment. Benzene at the highest dose (1,318 mg/kg) also caused a significant increase in micronuclei and SCE in both maternal bone marrow and fetal liver cells. The embryonic genotoxic effect of TEM was much higher than that of benzene for both genetic endpoints, and the frequency of micronuclei induced by benzene was higher in fetal liver than in maternal bone marrow cells. Vinblastine, a spindle poison, induced micronuclei but not SCE. Micronuclei induction by vinblastine was 7 fold greater in maternal bone marrow than in fetal liver cells. All three chemicals were cytotoxic in maternal bone marrow cells, but not in fetal liver cells except for TEM, which showed a weak cytotoxicity in fetal liver cells in the micronucleus assay. These results indicate that TEM, benzene, and vinblastine are transplacental genotoxicants in mice.

Animals↗
PubMed1992

Coordinated regulation of vascular endothelial cell growth and prostacyclin production by epidermal growth factor: evidence of clonal variations among rat aortic endothelial cells.

Rat aortic endothelial cells were found to exhibit clonal variations in response to EGF stimulation in cell growth and prostacyclin synthesis. EGF-induced growth and prostacyclin synthesis appeared to be regulated in a coordinated manner in that a clone with a higher response to EGF growth stimulation also exhibited a higher response to EGF-stimulated prostacyclin synthesis. This observation implies a possible involvement of prostacyclin synthesis in some of the biological effects of EGF on vascular endothelial cells.

Animals↗
PubMed1992

A cross-over study of three oral contraceptives containing ethinyloestradiol and either desogestrel or levonorgestrel.

A randomised cross-over trial was performed to compare the pharmacodynamic actions of three low-dose oral contraceptives (OCs): Marvelon (150 micrograms desogestrel (DSG)+ 30 micrograms ethinyloestradiol (EE)), Mercilon (150 micrograms DSG + 20 micrograms EE) and Microgynon (150 micrograms levonorgestrel (LNG) + 30 micrograms EE). None of the OCs produced any significant changes in serum cholesterol, LDL-C and apoprotein B. Triglycerides were increased by the desogestrel OCs but not by Microgynon. The latter however increased the glucose and insulin responses to a glucose tolerance test whereas Marvelon and Mercilon had no effect. HDL-C increased with Marvelon, was unchanged with Mercilon and was decreased with Microgynon. Apoprotein AII was increased by all three OCs but only the DSG OCs increased apoprotein AI. All OCs produced similar increases in caeruloplasmin but the increase in SHBG was much greater with Marvelon and Mercilon than with Microgynon. Testosterone was reduced more with Microgynon than with the DSG OCs. Many of the changes reflect the strong anti-oestrogenic action of LNG on metabolic parameters compared to DSG. Except for the effect on HDL-C, there was little difference between Marvelon and Mercilon on metabolic parameters and this complements the findings from large-scale clinical trials of the two OCs. Mercilon, therefore provides a very satisfactory alternative to Marvelon.

Adult↗
PubMed1992

Serum protease inhibitors promote anchorage-independent growth of transformed cells in serum-free medium.

The effect of three serum serine protease inhibitors on the serum-free agar growth of an SV40-transformed 3T3 cell line was investigated. Antithrombin III, alpha-2-macroglobulin and alpha-1-antitrypsin were found to potently stimulate colony growth in a semisolid medium because of their anti-proteolytic properties. These results indicate that protease inhibitors can facilitate tumor cell growth in serum-free agar cultures and suggest that the stimulatory effect of serum on the growth of certain transformed cells in agar may at least partially be due to the high levels of protease inhibitors found in serum.

3T3 Cells↗
PubMed1992

Comparison of effects following the intracorporeal injection of papaverine and prostaglandin E1.

A study group of 240 impotent men receiving intracorporeal injections were divided into 2 groups: the first group received papaverine (60 mg) and the second prostaglandin E1 (PGE1 20 micrograms). The effect of the drugs was evaluated according to the onset of erection, rigidity and the duration of erection; 136 patients were treated with papaverine and 104 with PGE1. The onset of action in these groups was 6.42 +/- 5.39 vs 10.14 +/- 5.41 min; the rigidity score was 3.37 +/- 0.89 vs 3.60 +/- 1.10 and the duration of erection was 49.56 +/- 62.56 vs 63.60 +/- 44.57 min respectively. There was a significant difference in the onset of action (PGE1 was slower than papaverine) and maintenance of erection (longer with PGE1 than with papaverine). Another group of 17 patients received both papaverine and PGE1. The effects of papaverine were better in 4 cases, worse in 5 and equal to PGE1 in 8. This study indicates that compared with papaverine, treatment with PGE1 produces a slower onset of action, a longer duration of erection and fewer side effects.

Adult↗
PubMed1992

[Changes and significance of chemiluminescence of polymorphonuclear leukocytes in endotoxin-induced lung injury in conscious sheep].

The chemiluminescence (CL) of polymorphonuclear leukocytes and its relation with pulmonary microvascular permeability after endotoxin-induced lung injury in conscious sheep with lung lymph fistula were observed. Four hours after the injury the CL of PMNs increased from 0.27 cpm/PMN of baseline to 0.69 cpm/PMN (P < 0.05). The increment of the CL had positive correlation with the increment of lung lymph flow or permeability index (r = 0.632 0.638 P < 0.05), suggesting that the increase of pulmonary microvascular permeability after the endotoxin injury had relation with the increase of the respiratory tract of PMNs.

Animals↗
PubMed1991

Role of growth factors in the contraction and maintenance of collagen lattices made with arterial smooth muscle cells.

The contraction of collagen lattices made with arterial smooth muscle cells was studied in medium MCDB 107 without serum or supplemented with 1% fetal bovine serum, plus insulin, transferrin, and low-density lipoprotein. Under these conditions, smooth muscle cell mitogens including HBGF-1 (aFGF), PDGF, and EGF stimulated contraction. Stimulation by HBGF-1 was more profound than with other factors tested. HBGF-1 stimulation of lattice contraction was blocked by protein synthesis inhibitors, but not inhibitors of DNA synthesis. Histological observations indicated that HBGF-1 also enhanced the maintenance of healthy cells in the lattice. Taken together, these observations suggest that HBGF-1 stimulates lattice contraction, not by a mitogenic effect, but by stimulating synthesis of specific cellular proteins. Since the greatest effects of HBGF-1 on lattice contraction were seen during the first 72 h following casting, the effects on maintenance of cell viability are probably less important in promoting lattice contraction.

Animals↗