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A Huang

Publications and source records attributed to A Huang.

16 recordsLinked to original sources
PubMed1992

NMR analysis of helix I from the 5S RNA of Escherichia coli.

The structure of helix I of the 5S rRNA from Escherichia coli has been determined using a nucleolytic digest fragment of the intact molecule. The fragment analyzed, which corresponds to bases (-1)-11 and 108-120 of intact 5S rRNA, contains a G-U pair and has unpaired bases at its termini. Its proton resonances were assigned by two-dimensional NMR methods, and both NOE distance and coupling constant information have been used to calculate structural models for it using the full relaxation matrix algorithm of the molecular dynamics program XPLOR. Helix I has A-type helical geometry, as expected. Its most striking departure from regular helical geometry occurs at its G-U, which stacks on the base pair to the 5' side of its G but not on the base pair to its 3' side. This stacking pattern maximizes interstrand guanine-guanine interactions and explains why the G-U in question fails to give imino proton NOE's to the base pair to 5' side of its G. These results are consistent with the crystal structures that have been obtained for wobble base pairs in tRNAPhe [Mizuno, H., & Sundaralingam, M. (1978) Nucleic Acids Res. 5, 4451-4461] and A-form DNA [Rabbinovich, D., Haran, T., Eisenstein, M., & Shakked, Z. (1988) J. Mol. Biol. 200, 151-161]. The conformations of the terminal residues of helix I, which corresponds to bases (-1)-11 and 108-120 of native 5S RNA, are less well-determined, and their sugar puckers are intermediate between C2' and C3'-endo, on average.

Base Composition↗
PubMed1992

Loss of heterozygosity mapping in Wilms tumor indicates the involvement of three distinct regions and a limited role for nondisjunction or mitotic recombination.

Loss of heterozygosity (LOH) for polymorphic markers is a frequently occurring event in some tumors, reflecting the role of allele loss in the development of these tumors. We have determined LOH in 38 cases of Wilms tumor for the 2 known loci on chromosome arm 11p and for a newly detected locus on chromosome arm 16q. Only 7 of the 38 tumors studied showed reduction to homozygosity of 11p13 markers. In 4 of these tumors, reduced expression of WT1 and WIT1, genes located at 11p13 and implicated in Wilms tumorigenesis, was noted. However, this was also found in 2 of 7 tumors showing LOH exclusively of 11p15 markers and in 15 of the remaining 24 tumors in which there was no LOH for 11p markers. This suggests that events not involving mitotic recombination or chromosome nondisjunction are the most common mechanisms for mutations at the 11p Wilms tumor locus. We also noted that mitotic recombination involving 11p15 loci occurred in addition to reduced expression of the 11p13 locus genes in 2 tumors, suggesting a possible interaction between these 2 loci. In addition, LOH for 16q markers was observed in 6 tumors. In one case this was coincident with reduction of WT1 and WIT1 gene expression, and in 3 other cases it occurred in addition to 11p LOH. This indicates that an additional locus on 16q is likely to be involved in Wilms tumorigenesis.

Adolescent↗
PubMed1992

Cognitive style as a factor in accounting students' perceptions of career-choice factors.

Since prior studies of individuals' perceptions of career-choice factors have not considered the effect of cognitive styles of subjects, this study, using 68 accounting students, investigated the mediating effects of the field dependent-independent cognitive dimension on perceptions of the importance of career-choice factors. The results, in general, show that cognitive style affected individuals' perceptions of career-choice factors, suggesting that future studies of individuals' perceptions should take into account individual cognitive differences.

Accounting↗
PubMed1992

Coordinate expression of Wilms' tumor genes correlates with Wilms' tumor phenotypes.

The cloning and molecular characterization of two putative tumor genes, WT1 and WIT1, from the chromosome 11p13 region has provided a means of evaluating their role in the generation of Wilms' tumor heterogeneity. A series of 29 tumors were analyzed for WT1 and WIT1 expression by Northern blot or RNase protection analyses, and results were compared with tumor histopathology. Tumors were scored for the percentage of mesenchymal and epithelial derived tissue components. Homotypic tumors comprised blastema, tubular epithelium, and a fibroblast-like mesenchyme. In addition to these tissue components, the group of tumors designated as heterotypic also contained ectopic cell phenotypes such as muscle and squamous epithelium. The analyses suggest that heterotypic differentiation patterns occur when WT1 and WIT1 expression is low relative to normal fetal kidney. In situ hybridization using antisense RNA probes showed that WT1 and WIT1 were concordantly expressed in normal fetal kidney and in the blastema of tumors. The ratio of WT1:WIT1 expression remained relatively constant in homotypic tumors but deviated significantly in heterotypic tumors. These results suggest that expression patterns of the WT1 and WIT1 genes can be closely correlated to Wilms' tumor histopathology.

Blotting, Northern↗
PubMed1991

A randomized comparison of two doses of human lymphoblastoid interferon-alpha in hairy cell leukemia. Wellcome HCL Study Group.

One hundred thirty-eight patients with hairy cell leukemia were randomized to receive either a dose of 2.0 megaunits (MU)/m2 or a 10-fold lower dose of 0.2 MU/m2 of a highly purified natural alpha-interferon, administered daily for 28 days followed by a three times a week schedule. Ninety-seven of these patients had previously undergone splenectomy, but otherwise none of the patients had received prior therapy for their leukemia. The two doses were comparable in their effect on improving the neutrophil and platelet count, whereas the higher dose had a greater beneficial effect on the hemoglobin level and a greater antileukemic effect on the marrow. Acute toxicity in the form of a flu-like syndrome, neurologic side effects, neutropenia, and the need for platelet transfusions was observed less frequently in the low-dose group, as was the chronic fatigue syndrome. No neutralizing antibody activity was seen in the sera from 61 patients examined. Because of its beneficial effect on the neutrophil and platelet count and a lower degree of toxicity (ie, a superior therapeutic/toxicity ratio), the low dose is recommended as initial therapy in patients with hairy cell leukemia. This therapy may be followed by dose escalation once clinical improvement is observed.

Adult↗
PubMed1991

EDRF-mediated shear-induced dilation opposes myogenic vasoconstriction in small rabbit arteries.

In small saline-perfused rabbit mesenteric arteries (diam 221 +/- 4 microns, means +/- SE; n = 48) in situ, the interactions of endothelium-derived relaxing factor (EDRF)-mediated flow-dependent dilation and myogenic constriction were studied. When pump flow was increased two- to fivefold (2.8 +/- 0.1-fold), input perfusion pressure rose by 133 +/- 17%. Vessel diameter first increased passively by 9 +/- 1% and then decreased to or below control values reflecting the vascular myogenic activity. This was followed by a 16 +/- 3% increase in diameter, which was flow dependent, because nonperfused vessels exposed to the same intravascular pressures did not dilate. When the perfusate viscosity was increased with dextran solutions, both the basal diameters and the flow-induced dilator responses were significantly augmented, indicating that the increase in shear stress was the stimulus. The flow-dependent dilation was abolished by inhibition of EDRF with either hemoglobin (10 microM) or NG-nitro-L-arginine (0.3 mM) and also after preincubation with neuraminidase (0.2 U/ml, 30 min), which removes part of the membrane glycocalyx. Thus, myogenic responses in small mesenteric arteries can be effectively opposed by shear-induced release of EDRF. This might be a major mechanism for maintaining adequate tissue perfusion when pressure and shear stress increase simultaneously (e.g., exercise hyperemia, autoregulation) and otherwise myogenic activity would reduce vascular conductivity.

Acetylcholine↗
PubMed1991

Frequent identification of HIV-1 DNA in bronchoalveolar lavage cells obtained from individuals with the acquired immunodeficiency syndrome.

Tissue macrophages are recognized as a cellular target for infection with the human immunodeficiency virus type 1 (HIV-1). To characterize the nature of this cell-retrovirus interaction within the lower respiratory tract we analyzed fluid and cells obtained by bronchoalveolar lavage (BAL) of eight individuals with acquired immunodeficiency syndrome (AIDS) who were undergoing diagnostic fiberoptic bronchoscopy. Of these eight individuals, seven had active infection with Pneumocystis carinii; one had suspected cytomegalovirus pneumonitis. At the time of study two were receiving the antiretroviral drug zidovudine (azidothymidine [AZT]). HIV-1 could not be isolated from any of the eight samples of BAL fluid concentrated by ultracentrifugation through 20% sucrose. HIV-1 antigen (p24) was detected in one of eight samples of concentrated BAL fluid but could not be found in eight samples of media conditioned by overnight incubation with adherent BAL cells. Despite the infrequent detection of HIV-1 antigen it was possible to identify HIV-1 genomic sequences by the use of a DNA amplification technique, the polymerase chain reaction, in all eight BAL cell preparations. In BAL cells adherent for up to 5 days in culture this method detected retroviral DNA that hybridized to a complementary pair of primers located in the env and gag gene regions of HIV-1. These studies demonstrate the uniform presence of HIV-1 harboring cells within the airways of the lung in individuals with AIDS and active respiratory infection and may have implications for local organ defense.(ABSTRACT TRUNCATED AT 250 WORDS)

Acquired Immunodeficiency Syndrome↗
PubMed1991

[Determination and comparison of beta-glucuronidase activity among strains of B. fragilis and E. coli].

We determined and compared the beta-glucuronidase (beta-G) activity among strains of B. fragilis and E. coli under the optimum condition. Results showed that the mean beta-G activity of strain B. fragilis ATCC25285 was 94.7u. B. fragilis ATCC25285 strain was selected as the model strain to establish the animal model of bilirubin gallstones because its beta-G activity was obviously higher than that of B. fragilis CDC14462 and E. coli 3362 (O157K88) strain.

Bacteroides fragilis↗
PubMed1991

[Study on ursodeoxycholic acid biotransformation by three strains of clostridia].

Using the improved TLC procedure, we measured the conversion rates of ursodeoxycholic acid(UDCA) from chenodeoxycholic acid (CDCA) by 3 strains of clostridia--C. perfringens HS-10, C. butyricum DL-20 and LQ-29 isolated. The orthogonal test was used to determine the optical conditions of biotransformation for HS-10. It was found that the conversion rate of UDCA by HS-10 was over 80% during 6-48 h in RCM medium containing 0.2 mmol/L CDCA. The UDCA conversion rates were still over 70% when the CDCA concentrations were as high as 0.8-1.0 mmol/L. In addition, the WW-BCP (Waste water from bean curd production) without any supplemental nutrients was preliminarily proved to be a potential inexpensive conversion medium.

Biotransformation↗
PubMed1978

Cellular and molecular studies on globin gene expression.

Globin gene expression has been studied with the use of a combination of cell and molecular biology techniques. With a somatic cell hybrid between mouse erythroleukemia (MEL) and human erythroid cells, human and mouse globin genes can be coexpressed in the same hybrid cell. Somatic cell hybridization between MEL cells and nonerythroid cells (e.g., human fibroblasts) results in hybrid cells that cannot be induced to produce hemoglobin of any type. Molecular hybridization of cellular DNA and RNA with globin cDNA indicates that the globin genes are present but that no globin mRNA is in the nonexpressing hybrid cell. This finding demonstrates that the loss of globin gene expression in the hybrid cell occurs at the level of transcription or mRNA processing. The nucleus of the nonerythroid cell is not necessary for the extinction of globin gene expression, since cybrids formed from MEL cells with enucleated nonerythroid cells also result in cells which cannot be induced to synthesize hemoglobin even after 40 or more generations. These data suggest that the cytoplasm of cells contains diffusible regulatory molecules which influence globin gene expression. In our attempt to develop an intracellular assay to test for regulatory molecules, we studied the procedure microinjection with red blood cell (RBC) ghosts. Rabbit globin mRNA (with hemin) was loaded into RBC's and then, by Sendai virus-mediated fusion, into Chinese hamster ovary (CHO) cells growing in culture; these microinjected CHO cells synthesized hemoglobin. Since this microinjection procedure appears to be effective in inserting both proteins and nucleic acids into intact cells, it should be possible to develop modifications for inserting aliquots of fractionated cytoplasm into growing cells. The procedure might then be useful as an assay for putative genetic regulatory molecules.

Animals↗
PubMed1976

Effects of nitrogen mustard and splenectomy on mouse bone marrow colony formation in vitro.

Improved tolerance of splenectomized patients with Hodgkin's disease (HD) to radiotherapy and chemotherapy has been reported. The present study was undertaken to determine the effects of splenectomy and nitrogen mustard (NM) on colony-forming cells (CFC's) of bone marrow cells obtained from CF1 male mice by in bitro agar-gel technique. Splenectomized mice were given NM intraperitoneally on day 11. On day 15, they were sacrificed and the bone marrow was cultured with a source of colony-stimulating factor (CSF). Spleen extract was prepared by grinding spleens from CF1 mice. On the eighth day of incubation, significantly higher numbers of CFC's were found in splenectomized animals at 1% confidence level (F Test) compared with the nonsplenectomized animals. Both splenectomized and non-splenectomized mice had a greater colony response after NM (at 5% confidence level) than saline-treated controls. Maximum numbers of colonies were obtained in the nustard-treated asplenic animals. Splenic extract, as well as extracts from other organs, when added to the culture plates resulted in inhibition of colony formation. The significance of in vitro inhibition after addition of organ extract is uncertain.

Animals↗
PubMed1975

Fatal paralytic ileus complicating phenothiazine therapy.

The occurrence of fatal paralytic ileus with peritonitis in a patient receiving phenothiazines and an antiparkinsonian agent is described. Although sporadic reports of this complication have appeared, it has not been emphasized in the literature. Only by being alert to this problem can one hope to achieve earlier diagnosis and begin prompt and appropriate treatment.

Adult↗
PubMedDate not supplied

Invasive aspergillus rhinosinusitis in patients with acute leukemia.

Invasive aspergillus rhinosinusitis is a potentially lethal complication of chemotherapy-induced neutropenia in patients with acute leukemia. The majority of cases are caused by Aspergillus flavus. The infection is difficult to diagnose early but should be suspected when a neutropenic patient develops persistent fever without a known source, symptoms of rhinitis or sinusitis, cutaneous findings over the nose or sinuses, symptoms and signs of orbital or cavernous sinus disease, or an ulcerating lesion of the hard palate or gingiva. Careful anterior rhinoscopy followed by computed tomography of the sinus helps establish the diagnosis, which should be confirmed by histologic study and culture of biopsied material. Early treatment with aggressive surgery, high-dose amphotericin B and 5-fluorocytosine, and possibly white blood cell transfusions may produce a cure if the patient's bone marrow recovers. Newer antifungal agents offer promise for prophylaxis and treatment of this infection.

Acute Disease↗