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Biomedical subjects

J Huang

Publications and source records attributed to J Huang.

At least 739 records · Page 41Linked to original sources
PubMed1993

Role of SV40 T antigen binding to pRB and p53 in multistep transformation in vitro of human uroepithelial cells.

In the present study, we examined the sufficiency of SV40 T antigen (Tag) binding to pRB and p53 to substitute for alterations in RB and TP53 at all stages of human uroepithelial cell (HUC) transformation in vitro. Two independent SV40 immortalized HUCs (SV-HUC and SV-HUC/CK2) and 17 independent derivative carcinogen-induced or spontaneous tumors (T-SV-HUCs and T-SV-HUC/CK2) representing different stages of urothelial tumorigenesis were examined. Although five of 17 T-SV-HUCs and SV-HUC/CK2 and its derivative tumor showed 13q chromosome deletion and loss of heterozygosity (LOH), this did not reflect functional loss of pRB because Tag/pRB binding was unaltered and sequencing showed a normal RB gene in all these tumors. No genetic alterations involving 17p or TP53 were detected in any tumors in this study using the same techniques. These results indicate that Tag/pRB and Tag/p53 binding apparently abrogate requirements for/or a selective advantage of RB and TP53 mutations in HUC tumorigenic transformation and progression, as well as in HUC immortalization. These data also provide new evidence that more than one suppressor gene may be located on chromosome 13q.

Antigens, Polyomavirus Transforming↗
PubMed1993

Comparison of catheter ablation using direct current energy versus radiofrequency: observations in 147 patients with supraventricular tachyarrhythmias.

We studied the follow-up of 147 patients who underwent catheter ablation because of drug resistant supraventricular tachyarrhythmias. Direct current (DC) ablation was performed in 116 patients, while 31 patients underwent radiofrequency (RF) ablation. In 101 patients (87%) with DC ablation and in 28 patients (90%) with RF ablation, complete atrioventricular (AV) block was achieved initially. Fifteen patients (13%) with DC ablation and three patients (11%) with RF ablation resumed AV conduction. Serious complications occurred in eight patients (7%) with DC ablation and in none of the patients with RF ablation. During the mean follow-up of 45 +/- 24 months, 13 patients died (11%) who underwent DC ablation; during the mean follow-up of 11 plus or minus 3 months, no patient died who had had RF ablation. Transcatheter ablation using DC or RF is an effective treatment in patients with drug resistant supraventricular arrhythmias, providing a beneficial long-term outcome including an improved quality of life. Although the risk of complications is low, this procedure should be reserved for patients with supraventricular arrhythmias who do not respond to conventional drug therapy.

Adult↗
PubMed1993

vsrB, a regulator of virulence genes of Pseudomonas solanacearum, is homologous to sensors of the two-component regulator family.

Pseudomonas solanacearum, an important wilt pathogen of many plants, produces several extracellular proteins (EXPs) and extracellular polysaccharides (EPSs) that contribute to its virulence. Using TnphoA mutagenesis, we discovered a new gene, vsrB, that when inactivated causes a major reduction in the virulence and production of an EPS. Analysis of eps::lacZ reporters showed that vsrB is required for maximal expression (transcription) of eps, whose products are required for production of EPS I, a major virulence determinant. Analysis of EXPs in culture supernatants revealed that inactivation of vsrB also causes reduced production of two major EXPs, with molecular masses of 28 and 97 kDa, and a simultaneous 15-fold increase in levels of another EXP, PglA endopolygalacturonase. The vsrB gene was cloned from a P. solanacearum genomic library by complementation of the nonmucoid phenotype of the vsrB::TnphoA mutant and then subcloned on a 2.4-kb DNA fragment. TnphoA fusion analysis and subcellular localization of the vsrB gene product in Escherichia coli maxicells suggest that it is a ca. 60-kDa transmembrane protein. The nucleotide sequence of the 2.4-kb DNA fragment was determined, and a 638-amino-acid open reading frame was found for VsrB. A search of the GenBank data base found that the central part of VsrB has homology with the histidine kinase domain of sensors in the two-component regulator family, while the C terminus has homology with the phosphate receiver domain of response regulators in the same family. Genetic analysis suggests that the receiver domain is not required for vsrB function.

Amino Acid Sequence↗
PubMed1993

A novel hepatitis B virus (HBV) genetic element with Rev response element-like properties that is essential for expression of HBV gene products.

Many viruses possess complex mechanisms involving multiple gene products and cis-regulatory elements in order to achieve a fine control of their gene expression at both transcriptional and posttranscriptional levels. Hepatitis B virus (HBV) and retroviruses share many structural and functional similarities. In this study, by genetic and biochemical analyses, we have demonstrated the existence of a novel genetic element within the HBV genome which is essential for high-level expression of viral gene products. This element is located 3' to the envelope coding region. We have shown that this genetic element is cis acting at the posttranscriptional level and that its function is exerted at the level of RNA processing as part of transcribed sequences. This RNA element is also functional in the context of a heterologous gene. Similar to the function of Rev-Rev response element interaction of human immunodeficiency virus type 1, this element appears to inhibit the splicing process and facilitate the transport and utilization of HBV transcripts.

Base Sequence↗
PubMed1993

Disruption of largest subunit RNA polymerase II genes in Trypanosoma brucei.

Two types of largest subunit RNA polymerase II (pol II) genes (pol IIA and pol IIB), differing in 3 amino acid substitutions, are encoded in the Trypanosoma brucei (stock 427-60) genome. As a result, the alpha-amanitin-resistant transcription of the procyclic acidic repetitive protein (PARP) and variant surface glycoprotein (VSG) genes was proposed to involve a modified, alpha-amanitin-resistant form of the largest subunit of pol II. Alternatively, pol I could transcribe the PARP and VSG genes. To discriminate between these two models, we deleted the N-terminal domain (about one-third of the polypeptide), which encodes the amino acid substitutions which discriminated the pol IIA and pol IIB genes, at both pol IIB alleles. The pol IIB- trypanosomes still transcribe the PARP genes and the VSG gene promoter region in insect-form trypanosomes by alpha-amanitin-resistant RNA polymerases, while control housekeeping genes are transcribed in an alpha-amanitin-sensitive manner, presumably by pol IIA. We conclude that the alpha-amanitin-resistant transcription of protein coding genes in T. brucei is not mediated by a diverged form of the largest subunit of pol II and that the presence of both the pol IIA and pol IIB genes is not essential for trypanosome viability. This conclusion was further supported by the finding that individual trypanosome variants exhibited allelic heterogeneity for the previously identified amino acid substitutions and that various permutations of the polymorphic amino acids generate at least four different types of largest subunit pol II genes. The expression of the PARP genes and the VSG gene promoter region by alpha-amanitin-resistant RNA polymerases in the pol IIB- trypanosomes provides evidence for transcription of these genes by pol I.

Amanitins↗
PubMed1993

Binding of myc proteins to canonical and noncanonical DNA sequences.

Using an in vitro binding-site selection assay, we have demonstrated that c-Myc-Max complexes bind not only to canonical CACGTG or CATGTG motifs that are flanked by variable sequences but also to noncanonical sites that consist of an internal CG or TG dinucleotide in the context of particular variations in the CA--TG consensus. None of the selected sites contain an internal TA dinucleotide, suggesting that Myc proteins necessarily bind asymmetrically in the context of a CAT half-site. The noncanonical sites can all be bound by proteins of the Myc-Max family but not necessarily by the related CACGTG- and CATGTG-binding proteins USF and TFE3. Substitution of an arginine that is conserved in these proteins into MyoD (MyoD-R) changes its binding specificity so that it recognizes CACGTG instead of the MyoD cognate sequence (CAGCTG). However, like USF and TFE3, MyoD-R does not bind to all of the noncanonical c-Myc-Max sites. Although this R substitution changes the internal dinucleotide specificity of MyoD, it does not significantly alter its wild-type binding sequence preferences at positions outside of the CA--TG motif, suggesting that it does not dramatically change other important amino acid-DNA contacts; this observation has important implications for models of basic-helix-loop-helix protein-DNA binding.

Amino Acid Sequence↗
PubMed1993

Comprehensive health evaluation of workers in the ceramics industry.

A cross sectional study on ceramics workers in the Seto area of Japan was conducted to determine whether there are differences in the morbidity pattern and overall health among the working populations employed by different sized companies engaged in the ceramics industry. The study population consisted of 3324 male ceramics workers (age range 40-69) who participated in the Seto occupational health screening programme in 1990. The prevalences of pulmonary diseases (silicosis and tuberculosis) and findings of some nonpulmonary diseases were compared in terms of company size by categories of 1-19, 20-49, 50-99, and 100 or more employees. The values of various screening tests were subjected to principle component analysis to extract factors representing key indices of health state. The average factor scores stratified by company size were used to quantitatively evaluate the comprehensive health level. Both prevalence and multivariate analysis showed that the employees working for smaller companies had overall worse health. The smaller the company, the higher the prevalence and the lower the health scores for silicosis and pulmonary tuberculosis tended to be; significantly increased rates and lower health scores for hypertension, anaemia, and glucosuria among small companies were also found when compared with larger companies. The high morbidity of silicosis and pulmonary tuberculosis in smaller companies contributed most to the decline in the overall health level.

Adult↗
PubMed1993

A redox-based O2 sensor in rat pulmonary vasculature.

The effector mechanism of hypoxic pulmonary vasoconstriction (HPV) involves K+ channel inhibition with subsequent membrane depolarization. It remains uncertain how hypoxia modulates K+ channel activity. The similar effects of hypoxia and mitochondrial electron transport chain (ETC) inhibitors on metabolism and vascular tone suggest a common mechanism of action. ETC inhibitors and hypoxia may alter cell redox status by causing an accumulation of electron donors from the Krebs cycle and by decreasing the production of activated O2 species (AOS) by the ETC. We hypothesized that this shift toward a more reduced redox state elicits vasoconstriction by inhibition of K+ channels. Pulmonary artery pressure and AOS, measured simultaneously using enhanced chemiluminescence, were studied in isolated perfused rat lungs during exposure to hypoxia, proximal ETC inhibitors (rotenone and antimycin A), and a distal ETC inhibitor (cyanide). Patch-clamp measurements of whole-cell K+ currents were made on freshly isolated rat pulmonary vascular smooth muscle cells during exposure to hypoxia and ETC inhibitors. Hypoxia, rotenone, and antimycin A decreased lung chemiluminescence (-62 +/- 12, -46 +/- 7, and -148 +/- 36 counts/0.1 s, respectively) and subsequently increased pulmonary artery pressure (+14 +/- 2, +13 +/- 3, and +21 +/- 3 mm Hg, respectively). These agents reversibly inhibited an outward, ATP-independent, K+ current in pulmonary vascular smooth muscle cells. Antimycin A and rotenone abolished subsequent HPV. In contrast, cyanide increased AOS and did not alter K+ currents or inhibit HPV. The initial effect of rotenone, antimycin A, and hypoxia was a change in redox status (evident as a decrease in production of AOS). This was associated with the reversible inhibition of an ATP-independent K+ channel and vasoconstriction. These findings are consistent with the existence of a redox-based O2 sensor in the pulmonary vasculature.

Animals↗
PubMed1993

Lysine residues 2 and 104 of the human chorionic gonadotrophin beta subunit influence receptor binding.

Human chorionic gonadotrophin (hCG), like other members of the glycoprotein hormone family, contains a common alpha subunit and a hormone-specific beta subunit. The latter is a 145 amino acid residue polypeptide with six sites of glycosylation. Positions 2 and 104 are occupied by basic amino acid residues in the 12 known amino acid sequences of mammalian beta subunits from CG and LH, a related gonadotrophin that acts through the same receptor. Lysine residues are found in both these positions in hCG-beta. Using site-directed mutagenesis, each of these two lysines in hCG-beta was replaced with glutamic acid. The mutant and wild-type cDNAs were subcloned into a eukaryotic expression vector, which was then transiently transfected into Chinese hamster ovary cells containing a stably integrated gene for the bovine alpha subunit. Holoprotein formation occurred with each of the two heterologous gonadotrophin mutants, i.e. the bovine alpha subunit bound to hCG-beta (Glu2) and to hCG-beta (Glu104), as well as with the control, i.e. the bovine alpha subunit bound to the hCG-beta wild-type subunit. In two in-vitro assays, one a competitive binding assay with 125I-labelled hCG as bound ligand and the other based on stimulation of progesterone production in a transformed murine Leydig cell line, MA-10, both the heterodimers containing a mutant beta subunit exhibited bioactivity, but their potencies were lower than that of the bovine alpha subunit bound to the hCG-beta wild-type subunit. These results suggest that the basic amino acid residues at positions 2 and 104 in hCG-beta participate, either directly or indirectly, in receptor binding.

Amino Acid Sequence↗
PubMed1993

[Inhaled nonasbestos fibers; pulmonary concentrations and fiber size in autopsied urban residents].

Nonasbestos fiber concentrations and fiber size distribution in autopsied lung tissues of 53 urban residents (34 males and 19 females) were analyzed by low temperature ashing-analytical transmission electron microscopy. The following findings were obtained. 1. Pulmonary nonasbestos fibers were found in all samples. Fiber consisting mainly of aluminum and silicon represented 80.0% of the total nonasbestos fibers observed. 2. The geometric mean concentration of nonasbestos fiber was significantly higher in males (47.6 x 10(6) fibers/g dry lung) than in females (18.2 x 10(6) fibers/g dry lung) (p < 0.05). This may be caused by differences in occupational exposure to nonasbestos fibers between males and females. 3. In females, the geometric mean concentration of nonasbestos fibers of smokers (34.6 x 10(6) fibers/g dry lung) was higher than that of nonsmokers (11.4 x 10(6) fibers/g dry lung), while, in males, the geometric mean concentration of nonasbestos fibers was lower in smokers (53.9 x 10(6) fibers/g dry lung) than in nonsmokers (89.1 x 10(6) fibers/g dry lung). These differences were not statistically significant. 4. The mean value for the ratio of nonasbestos fiber to asbestos concentration which ranged from 2.3 to 268 in males, and from 1.3 to 52.0 in females, was 30.1 and 20.2 respectively. 5. The mean length, diameter and aspect ratio for nonasbestos fibers were 1.01 microns, 0.103 microns and 11.3, respectively. Although nonasbestos fibers were almost equal in length to asbestos, the mean diameter of nonasbestos fibers was almost one-half of that of asbestos. Most of nonasbestos fibers (99.0%) were too small to be visible by light microscopy.

Adult↗
PubMed1993

[Morphology, immunohistochemistry and differential diagnosis of 70 cases of adenocarcinoma of uterine cervix].

Seventy cases of cervical adenocarcinoma were classified into five types, namely: mucinous adenocarcinoma, endometrioid adenocarcinoma, mixed adenosquamous carcinoma, papillary adenocarcinoma and clear cell carcinoma. According to the morphological features, the results of mucin and immunohistochemical stainings, the histogenesis of cervical endometrioid adenocarcinoma and the differential diagnosis between cervical adenocarcinoma and endometrioid adenocarcinoma are discussed. The significance of vimentin staining for the differential diagnosis is also evaluated.

Adenocarcinoma↗
PubMed1993

Effects of chronic ethanol on growth hormone secretion and hepatic cytochrome P450 isozymes of the rat.

Growth hormone (GH) secretion is sexually dimorphic in the laboratory rat and the plasma GH profile is a determining factor in the regulation of the male-specific cytochrome P450 (CYP) 2C11. Acute ethanol has been reported previously to alter the secretion of GH, and in the present investigation, we have studied the effects of chronic (38 days) ethanol on plasma GH profiles, CYP 2C11 and the major ethanol-inducible cytochrome, CYP 2E1, using a total enteral nutrition system, where 35% of the total calories were ethanol. Ethanol-treated rats had elevated (P < or = .05) CYP 2E1 activities and apoprotein levels and increased steady-state mRNA levels encoding for CYP 2E1. Ethanol-treated rats also had reduced (P < or = .05) hydroxylation of testosterone at positions 2 alpha and 16 alpha, lower 2C11 apoprotein levels and lower steady-state mRNA levels encoding for 2C11. In addition, the plasma GH pulse profiles were altered in chronically treated rats by reducing (P < or = .05) the GH pulse amplitude and mean plasma GH concentrations. Our results suggest that: 1) the reduced CYP 2C11 activities, apoprotein levels and steady-state mRNA levels during chronic alcohol exposure are causally related to the alterations in GH secretion; and 2) chronic alcohol exposure elevated CYP 2E1 activities, apoprotein levels and steady-state mRNA levels, and these changes occurred primarily as the result of ethanol rather than undernutrition or as the combination of ethanol and undernutrition.

Androgens↗
PubMed1993

Cytochrome P450 CYP 2E1 induction during chronic alcohol exposure occurs by a two-step mechanism associated with blood alcohol concentrations in rats.

Intragastric infusion of ethanol to male rats as part of a system of total enteral nutrition allows chronic ethanol treatment without the nutritional and feeding problems associated with traditional liquid diets. Even though ethanol was infused at a constant rate 24 h a day, blood alcohol concentrations were observed to cycle over a 5- to 7-day period from values less than 10 mg/dl to greater than 400 mg/dl. Examination of the hepatic microsomal mono-oxygenase system in animals chronically treated with ethanol using this model revealed variable induction of cytochrome P450 CYP 2E1, the principal component of the microsomal ethanol oxidizing system. Correlations were observed between urine alcohol concentrations (UACs) and 1) the level of expression of CYP 2E1 mRNA in Northern blot analysis, 2) the level of CYP 2E1 apoprotein in Western blot analysis and, 3) microsomal p-nitrophenol (PNP) hydroxylation. The data from ethanol-treated animals were expressed as low UAC group (UACs < 200 mg/dl) and a high UAC group (UACs > 300 mg/dl) and compared to total enteral nutrition controls. In the low UAC group, a 6- to 7-fold induction in microsomal PNP hydroxylase (a CYP 2E1-dependent activity) was accompanied by a 4- to 5-fold increase in CYP 2E1 apoprotein, but no increase in CYP 2E1 mRNA levels. In contrast, in the high UAC group, induction of PNP hydroxylase was 15- to 16-fold, induction of CYP 2E1 apoprotein was 12- to 13-fold and CYP 2E1 mRNA was elevated 5- to 6-fold.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol Dehydrogenase↗
PubMed1992

A novel role for calcite in calcium homeostasis.

Calcium carbonate (CaCO3) minerals are known to be deposited in a wide array of different organisms, ranging from microbes to vertebrates [(1989) On Biomineralization, Oxford University Press, New York]. Calcite, aragonite and vaterite are the major crystalline structural polymorphs of CaCO3 associated with living systems, and participate in a variety of biological functions [(1989) Biomineralization: Chemical and Biochemical Perspectives, VCH Publishers, Weinham, Germany; (1991) Advances in Inorganic Chemistry 36, 137-200]. Here we report on the ability of a soil bacterium to synthesize calcite in a calcium-stressed environment. The elaboration of this exocellular crystalline residue enables the organism to regulate its calcium content. The attainment of calcium homeostasis via the exocellular deposition of bacterial calcite with unique crystal habits is a novel biological phenomenon.

Calcium↗
PubMed1992

Genistein inhibits protein histidine kinase.

Protein histidine kinase was prepared from whole cell extracts of the yeast, Saccharomyces cerevisiae. The enzyme was assayed using either histone H4 or a synthetic peptide corresponding to residues 70 to 102 of histone H4 as an in vitro substrate. With either substrate, both genistein and its solvent, dimethyl sulfoxide (Me2SO), inhibited protein histidine kinase. Me2SO alone gave a cooperative dose-response curve, with inhibition changing from almost zero below 10% Me2SO to 80% at 20% Me2SO with either substrate. Genistein gave a simple dose-response curve with 50% inhibition of protein histidine kinase at 110 microM genistein. In experiments with protein histidine kinase, genistein was a noncompetitive inhibitor with respect to ATP, histone H4 or the synthetic peptide, although, in the case of the synthetic peptide, the data were also consistent with competitive inhibition. These data gave Km values for both ATP and histone H4 of 15 microM, in satisfactory agreement with previously reported values (Huang, J., Wei, Y., Kim, Y., Osterberg, L., and Matthews, H. R. (1991) J. Biol. Chem. 266, 9023-9031). The Km for the synthetic peptide was 80 microM. The KI values were 270 or 310 microM measured with histone H4 or the synthetic peptide as substrate, respectively. While these KI values are relatively high, relative to published KI values for genistein inhibition of protein tyrosine kinases, many reported experiments use genistein at concentrations where inhibition of protein histidine kinase occurs. It is possible that some of the observed effects of genistein in vivo may be due to inhibition of protein histidine kinase.

Adenosine Triphosphate↗