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C Chen

Publications and source records attributed to C Chen.

At least 1,207 records · Page 67Linked to original sources
PubMed1987

Isolation of the Candida tropicalis gene for P450 lanosterol demethylase and its expression in Saccharomyces cerevisiae.

We have isolated the gene for cytochrome P450 lanosterol 14 alpha-demethylase (14DM) from the yeast Candida tropicalis. This was accomplished by screening genomic libraries of strain ATCC750 in E. coli using a DNA fragment containing the yeast Saccharomyces cerevisiae 14DM gene. Identity of this gene was confirmed by a) observing a heme binding region common to all P450s after sequencing the 3' portion of the gene, and b) based upon tests of its expression in strains of Saccharomyces cerevisiae.

Amino Acid Sequence↗
PubMed1987

High extracellular Ca2+ and Mg2+ stimulate accumulation of inositol phosphates in bovine parathyroid cells.

We examined the effects of the divalent cations Ca2+ and Mg2+ on inositol phosphate accumulation in bovine parathyroid cells prelabelled with [3H]inositol to determine whether the high extracellular Ca2+ and Mg2+-evoked transients in cytosolic Ca2+ in these cells might result from increases in cellular IP3 levels. In the presence of Li+, both Ca2+ and Mg2+ produced rapid, 2-6-fold increases in IP3 and IP2 and a linear increase in IP of 6-8-fold at 30 min. Smaller (1.5-2-fold) increases in IP2 and IP3 were evident within 7.5-15 s upon exposure to high (3 mM) Ca2+ in the absence of Li+. The relative potencies of Ca2+ and Mg2+ (Ca2+ 3-fold more potent than Mg2+) in elevating inositol phosphates were similar to those for their effects in inhibiting PTH release. Fluoride (5 and 10 mM) also produced similar increases in inositol phosphate accumulation, presumably through activation of phospholipase C by a guanine nucleotide (G) protein-dependent process. Thus, high extracellular Ca2+ and Mg2+-induced spikes in cytosolic Ca2+ in bovine parathyroid cells may be mediated by increases in IP3, perhaps through a receptor-mediated process linked to phospholipase C by a G-protein.

Animals↗
PubMed1987

Isolation of the alkane inducible cytochrome P450 (P450alk) gene from the yeast Candida tropicalis.

The gene for the alkane-inducible cytochrome P450, P450alk, has been isolated from the yeast Candida tropicalis by immunoscreening a lambda gt11 library. Isolation of the gene has been identified on the basis of its inducibility and partial DNA sequence. Transcripts of this gene were induced by alkane to levels 500 to 1000 fold over those detected in glucose-grown cells. The nucleotide sequence of the 3' portion of this gene revealed a coding sequence for the heme binding segment characteristic of the P450 gene family.

Alkanes↗
PubMed1987

Usefulness of anatomic parameters derived from two-dimensional echocardiography for estimating magnitude of left to right shunt in patients with atrial septal defect.

The ability of two-dimensional echocardiography (2DE) to quantitate the atrial septal defect size and left-to-right shunt magnitude was examined in 75 adult patients with simple ostium secundum atrial septal defect (ASD) with left-to-right shunts of 19-92% of systemic flow as determined by oximetry. The ASD was visualized in 71 of 75 (95%) patients utilizing subcostal 2DE, and the end-systolic atrial septal defect diameters in subcostal 2DE (ASDe) were measured. The maximal diameters of ASD measured during operation (ASDop) were obtained in 45 of these patients, who then underwent surgical ASD repair. The correlation between ASDe and ASDop was high (r = 0.91, p less than 0.001), indicating accuracy of quantitating defect size via subcostal 2DE approach. However, the correlation between the left-to-right shunt magnitude and ASDe was only fair (r = 0.76, p less than 0.01). In large ASDe the shunts varied greatly, while in small ASDe the shunts increased proportionally with increasing sizes of ASD. In addition, the ratio of left-to-right ventricular diameter (RVD/LVD) was determined. The RVD/LVD correlated relatively well with the shunt magnitudes (r = 0.83, p less than 0.001). Using the two new echocardiographic parameters of ASDe and RVD/LVD, a high percentage (85%) of patients with a large left-to-right shunt requiring surgical closure can be identified. All 43 patients with ASDe greater than 2.0 cm and RVD/LVD greater than 1.1 had a left-to-right shunt greater than 40%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Inhibition of protein synthesis prolongs Ca2+-mediated reduction of K+ currents in molluscan neurons.

Elevated intracellular Ca2+ concentration within the Hermissenda type B cell has previously been shown to cause transient reduction of both the early K+ current IA and the delayed, Ca2+-dependent K+ current ICa2+-K+, a reduction that is more permanent with classical conditioning. Other earlier experiments suggested that Ca2+-mediated reduction of K+ currents initially involves the dual activation of Ca2+/calmodulin-dependent and Ca2+/lipid-dependent protein kinases. In the present study, voltage-clamp conditions that cause substantial increases in intracellular Ca2+ concentration (i.e., a Ca2+ "load") were used to produce IA and ICa2+-K+ reduction with and without the protein synthesis inhibitor anisomycin or cycloheximide or the control substance deacetylanisomycin in the bathing medium. Anisomycin (100 microM) and cycloheximide (100 microM) caused no significant change of resting membrane potential, holding current, or the non-voltage-dependent "leak" current. However, inhibition of protein synthesis prevented recovery from Ca2+-mediated K+-current reduction. This effect resembled the effect of injecting purified Ca2+-dependent kinases and was blocked by the presence of trifluoperazine in the bathing medium. Activation of protein kinase C with a water-soluble phorbol ester caused marked reduction of protein synthesis in Hermissenda neurons as monitored by two-dimensional gel electrophoresis. Synthesis of new proteins therefore may be important for reversal of initial steps during memory storage, and Ca2+-activated phosphorylation pathways may initiate long-term changes by turning off (as well as by turning on) the synthesis of particular proteins.

Animals↗
PubMed1987

High-efficiency transformation of mammalian cells by plasmid DNA.

We describe a simple calcium phosphate transfection protocol and neo marker vectors that achieve highly efficient transformation of mammalian cells. In this protocol, the calcium phosphate-DNA complex is formed gradually in the medium during incubation with cells and precipitates on the cells. The crucial factors for obtaining efficient transformation are the pH (6.95) of the buffer used for the calcium phosphate precipitation, the CO2 level (3%) during the incubation of the DNA with the cells, and the amount (20 to 30 micrograms) and the form (circular) of DNA. In sharp contrast to the results with circular DNA, linear DNA is almost inactive. Under these conditions, 50% of mouse L(A9) cells can be stably transformed with pcDneo, a simian virus 40-based neo (neomycin resistance) marker vector. The NIH3T3, C127, CV1, BHK, CHO, and HeLa cell lines were transformed at efficiencies of 10 to 50% with this vector and the neo marker-incorporated pcD vectors that were used for the construction and transduction of cDNA expression libraries as well as for the expression of cloned cDNA in mammalian cells.

Animals↗
PubMed1987

Zinc status and delayed cutaneous hypersensitivity in handicapped children treated with anticonvulsants.

Delayed cutaneous hypersensitivity and hair zinc contents were investigated in 68 children treated with anticonvulsants and 14 untreated children, and serum zinc contents were also measured in 21 of the treated and 13 of the untreated children. Serum zinc levels in the treated and untreated children were 82.7 +/- 7.1 and 85.1 +/- 18.2 micrograms/dl, respectively. Hair zinc levels in the treated and untreated children were 145.4 +/- 27.0 and 144.3 +/- 20.1 micrograms/g, respectively. These two parameters were not significantly different between the two groups. However, a significantly depressed skin reaction and a higher incidence of hypozincnemia (below 70 micrograms/dl) were found in the treated children (p less than 0.05). The results indicated that phenytoin-induced zinc deficiency might be one of the possible factors or exacerbatory factors in suppressed cellular immunity found with anticonvulsant therapy.

Adolescent↗
PubMed1987

Permeabilization reveals classical stimulus-secretion coupling in bovine parathyroid cells.

Unlike most secretory cells, high extracellular Ca2+ inhibits, rather than stimulates, PTH release from parathyroid cells. To gain more direct access to the potentially unique secretory apparatus of this cell type, we developed techniques for permeabilizing parathyroid cells using electroshock. Exposure of dispersed bovine parathyroid cells to five 2-kV discharges results in more than 90% uptake of trypan blue and rapid loss of intracellular 86Rb, documenting permeabilization of the plasma membrane. Unlike intact parathyroid cells, a high Ca2+ concentration increases PTH release 2.8-fold from permeabilized cells, with half-maximal and maximal stimulation at 10(-5) and 4 X 10(-4) M Ca2+, respectively, a pattern similar to classical stimulus-secretion coupling. Moreover, PTH release was low at Ca2+ concentrations equivalent to those in intact cells at low extracellular Ca2+ levels (approximately 2 X 10(-7) M). Cellular mechanisms other than changes in the cytosolic Ca2+ concentration per se, therefore, presumably mediate low Ca2+-stimulated PTH release in the intact cell. Diacylglycerol and protein kinase C may play a role in this process, since dioctanoylglycerol (10(-4) M) and 12-O-tetradecanoyl phorbol 13-acetate (10(-6) M) each enhance PTH release from permeabilized cells 2- to 4-fold at a Ca2+ concentration (approximately 2 X 10(-7) M) equivalent to that present in the intact cell at low extracellular Ca2+ concentrations.

Animals↗
PubMed1987

Early clinical evaluation of the intravenous treatment of acute myocardial infarction with anisoylated plasminogen streptokinase activator complex.

50 consecutive patients with acute myocardial infarction and symptoms of less than 4 hours duration were treated with anisoylated plasminogen streptokinase activator complex (APSAC) 30U intravenously as a bolus injection over 5 minutes. An open infarct-related artery was found in 32 patients (64%) when the first coronary angiography was taken 66 +/- 21 minutes after APSAC. Complete reperfusion was subsequently seen in 10 of 18 patients with an occluded infarct-related artery 74 +/- 16 minutes after injection of APSAC. Thus, a patient infarct-related artery was seen in 42 patients (84%) within 68 +/- 20 minutes. A control coronary angiography was performed in 37 patients (74%) after 25 +/- 19 days. Reocclusion was found in 5 patients. The minimal cross-sectional area of the residual coronary stenosis increased from 1.3 +/- 0.9 mm2 to 1.8 +/- 1.9 mm2. Patients with residual thrombi after coronary thrombolysis (n = 13) demonstrated an increase of the minimal cross-sectional area of the residual stenosis from 1.2 +/- 0.8 to 2.6 +/- 2.3 mm2, whereas those without residual thrombi showed only minor changes of the minimal cross-sectional area (1.3 +/- 0.9 to 1.2 +/- 1.2 mm2). Thus, APSAC demonstrated a high patency rate and a low reocclusion rate after intravenous administration. The prolonged fibrinolytic activity of APSAC leads to a further regression of the residual coronary stenosis among patients with coronary thrombi after reperfusion.

Adult↗
PubMed1987

[Clinical study of subclinical hepatic cancer--analysis of 187 patients].

187 patients with subclinical hepatic cancer (SHC), collected by mass screening or follow-up of the hepatic diseases in our hospital from Dec. 1972 to Dec. 1984, are reported. The age ranged from 18 to 76 years with a median of 47. The sex ratio of male and female was 1.97:1. 143 (76.5%) patients had a positive pathology. The exploration rate was 60.4% and resection rate was 77.9%. Of them, there were 72 (81.8%) small liver cancers with lesions equal to or less than 5 cm in diameter. For patients with resection, the 1, 3 and 5 year survival rates were 77.3%, 39.3% and 34.6%, markedly higher than those treated by other means. B-ultrasonography gave a significantly higher positive rate (96.4%) in the localization of SHC, compared with nuclide imaging (17.6%). Basing on analysis of 187 patients with SHC, close follow-up of the subjects with low level persistent positive alpha-fetoprotein without active liver disease plays an important role in the early detection of SHC.

Adolescent↗
PubMed1987

[Acute effects of nitroglycerin on the energetics of the human left ventricular myocardium].

We analyzed performance and efficiency of the left ventricular myocardium on the basis of two new energetic parameters. The myocardial energy consumed during one cardiac cycle is related to performed work on the one hand (E1) and to the stress-time-integral on the other (E2). E1 was obtained by analysis of the pressure-volume integral divided by left ventricular muscle mass. E2 was obtained as follows: the stress-time integral was analyzed from pressure-volume data and wall thickness using an ellipsoidal calculation model. In order to transfer the stress-time integral into energy units, the value was multiplied by a constant factor which was obtained in experimental myothermal studies. In ten patients with coronary heart disease undergoing diagnostic heart catheterization, angiocardiography was performed before and after oral administration of nitroglycerin (1.6 mg). Total energy consumption (2E1 + E2) per gram myocardium per beat decreased from 6.1 +/- 1.3 mcal/g to 4.7 +/- 1.4 mcal/g (P less than 0.01), and myocardial efficiency (E1/[2E1 + E2]) increased from 27.0 +/- 3.1% to 28.4 +/- 4.3% (N.S.) on the average. This analysis explains quantitatively the beneficial effect of nitro-preparations on myocardial function and energetics.

Adult↗
PubMed1986

Regulation of the synthesis of the major surfactant apoprotein in fetal rabbit lung tissue.

Antibodies directed against the major apoprotein of rabbit lung surfactant, a 29-36-kDa glycoprotein, were used to study changes in the levels of translatable surfactant apoprotein mRNA in rabbit lung tissue during development, as well as the effects of cortisol and cyclic AMP analogues on the levels of surfactant apoprotein and its mRNA in fetal rabbit lung tissue in organ culture. The major surfactant apoprotein and its mRNA were undetectable in lung tissues of 21-day gestational age fetal rabbits. Translatable mRNA specific for the major surfactant apoprotein was first detectable in lung tissues of 26-day fetuses, increased 25-fold on day 28, reached peak levels at day 31, and declined after birth. Incubation of 21-day fetal rabbit lung explants with cortisol in serum-free medium resulted in an increase in the specific content of the 29-36-kDa apoprotein. Cyclic AMP analogues and forskolin, an activator of adenylate cyclase, also caused a marked increase in the accumulation of surfactant apoprotein. When fetal lung explants were incubated with cortisol and dibutyryl cyclic AMP in combination, the specific content of the surfactant apoprotein was increased to levels greater than that of explants treated with either cortisol or dibutyryl cyclic AMP alone. These effects of dibutyryl cyclic AMP and cortisol on surfactant apoprotein accumulation were associated with comparable changes in the levels of translatable surfactant apoprotein mRNA. Thus, we have shown for the first time that the induction of pulmonary surfactant apoprotein synthesis during differentiation in vitro and in vivo is associated with an increase in the level of translatable mRNA and that cortisol and cyclic AMP increase both the accumulation of the major surfactant apoprotein and the corresponding mRNA in fetal rabbit lung tissue in vitro.

Animals↗