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Biomedical subjects

S Huang

Publications and source records attributed to S Huang.

At least 415 records · Page 23Linked to original sources
PubMed1996

A cysteine proteinase, which cleaves human C3, the third component of complement, is involved in tumorigenicity and metastasis of human melanoma.

The DM-4 human melanoma cell line, which is highly metastatic in nude mice, expresses a C3-cleaving activity that proteolyzes labeled as well as unlabeled human C3. This C3-cleaving activity is a cysteine proteinase characterized by a M(r) 41,000. The p41 proteinase shares antigenic determinants with murine p39 procathepsin-L and human procathepsin-L. Preincubation of DM-4 cells with anti-p39 F(ab')2 induced up to 45% decrease in their complement resistance. Pretreatment of DM-4 cells with anti-p39 Ab strongly inhibited their tumorigenicity and significantly decreased their metastatic potential in nude mice. Thus, the p41 C3-cleaving proteinase contributes to tumorigenicity and metastasis of human melanoma DM-4 cells.

Animals↗
PubMed1996

Hydrogen bonding of tyrosine B10 to heme-bound oxygen in Ascaris hemoglobin. Direct evidence from UV resonance Raman spectroscopy.

The hemoglobin from Ascaris suum, a parasitic nematode, has a spontaneous dissociation rate for the dioxygen ligand that is 3 orders of magnitude less than for mammalian myoglobins or hemoglobins. In this hemoglobin, the distal histidine is replaced with a glutamine which is capable of forming a stabilizing hydrogen bond to the bound dioxygen. A single hydrogen bond from a glutamine is, under typical circumstances, not sufficient to account for the low off rate for oxygen. Several studies point to a second hydrogen bond to the heme-bound dioxygen originating from tyrosine B10 as the source of this unusual reactivity. In this study ultraviolet (UV) resonance Raman spectroscopy is used to directly observe the formation of this hydrogen bond upon oxygen binding. The study reveals that both oxygen and carbon monoxide induce similar conformational changes in the globin upon binding to the heme; however, in the case of oxygen, a strong hydrogen bond involving a tyrosine is also observed. Similar studies on the QE7L mutant of this Hb suggest that the glutamine plays a role in stabilizing a rigid tertiary structure associated with the distal heme pocket. This conformation maintains the tyrosine in an orientation conducive to hydrogen bond formation with a heme-bound dioxygen ligand.

Animals↗
PubMed1996

Conformational changes in oxyhemoglobin C (Glu beta 6-->Lys) detected by spectroscopic probing.

Hemoglobin C (Glu beta 6-->Lys) shares with hemoglobin S (Glu beta 6-->Val) the site of mutation, but with different consequences: deoxyHbS forms polymers, whereas oxyHbC readily forms crystals. The molecular mechanism for this property of oxyHbC is unknown. Since no detailed oxyHbC crystal structural information exists, spectroscopic probing is used in this study to investigate possible solution-phase conformational changes in HbC compared with HbA. Intrinsic fluorescence combined with UV resonance Raman data demonstrate a weakening of the Trp beta 15-Ser beta 72 hydrogen bond that most likely leads to a displacement of the A helix away from the E helix.

Glutamic Acid↗
PubMed1996

Dynamic organization of pre-mRNA splicing factors.

Studies from several laboratories during the past few years have increased our understanding towards the dynamic organization of pre-mRNA splicing factors in the mammalian cell nucleus. Many well characterized splicing factors have been localized in a speckled pattern in the cell nucleus. Upon the activation of RNA polymerase II transcription, splicing factors are recruited to the sites of transcription from sites of reassembly and/or storage. Nascent intron-containing RNA transcripts are spliced at the sites of transcription. The speckled distribution of splicing factors in the nucleus is altered when either transcription or pre-mRNA splicing activities are interrupted suggesting that the organization of the splicing machinery in the interphase nucleus is a direct reflection of the transcriptional activity of the cell.

Animals↗
PubMed1996

Improvement of productivity of yeast cell with a novel airlift loop reactor.

Two different strains of baker's yeast are cultivated using a fed-batch process with a novel airlift loop reactor. The reactor can be operated not only under steady-state conditions as the traditional airlift loop reactor, but also under forced periodically operational conditions in which the direction of liquid circulating flow is alternatively changed. Compared with the traditional steady-state operation, both the growth rate and yield of cells are much higher in the forced periodic operation.

Biotechnology↗
PubMed1996

Bcl-2 protects cells from cytokine-induced nitric-oxide-dependent apoptosis.

Cytokine-mediated cell death in tumor cells can be achieved through endogenous nitric oxide (NO) from within tumor cells or exogenous NO from either activated macrophages or endothelial cells. The purpose of this study was to determine the role of Bcl-2 in NO-mediated apoptosis. The incubation of murine L929 and NIH3T3 cells with interleukin-1 alpha (IL-1 alpha) and interferon gamma (IFN gamma) induced high endogenous NO production only in the L929 cells that also underwent apoptosis. NIH3T3 cells were not resistant to NO-mediated apoptosis. In fact, the incubation of L929 and NIH3T3 cells with exogenous NO derived from NO donors, sodium nitroprusside, or S-nitroso-N-acetyl-DL-penicillamine (SNAP) induced death, characterized by typical apoptotic morphology and DNA fragmentation, in both cell types, but to a higher degree in NIH3T3 cells than in the L929 cells. We then measured the effect of Bcl-2 expression on exogenous NO-induced apoptosis. At both the mRNA and protein levels, L929 fibroblasts expressed higher levels of endogenous mouse Bcl-2 than did NIH3T3 cells. At the same time, L929 cells were much more resistant to exogenous NO-induced cell death than were NIH3T3 cells. The inverse correlation between mouse Bcl-2 expression and sensitivity to exogenous NO-mediated cell death was also found in the murine K-1735 melanoma C-23 and X-21 clonal populations. Transfection of both NIH3T3 cells and L929 cells with the human bcl-2 gene led to resistance to both exogenous and endogenous NO-mediated apoptosis. These data demonstrate that NO-mediated apoptosis can be suppressed by expression of Bcl-2, suggesting that abnormal expression of Bcl-2 may influence the efficacy of tumor immunotherapy.

3T3 Cells↗
PubMed1996

Niruriside, a new HIV REV/RRE binding inhibitor from Phyllanthus niruri.

During the screening of natural products for their ability to inhibit the binding of HIV-REV protein to [33P]-labeled RRE RNA, one novel compound, niruriside (1), was isolated from the MeOH extract of the dried leaf of Phyllanthus niruri L. by bioassay-guided fractionation. The structure of niruriside was determined by spectroscopic methods. Niruriside showed specific inhibitory activity against the binding of REV protein to RRE RNA with an IC50 value of 3.3 microM; however, niruriside did not protect CEM-SS cells from acute HIV infection at concentrations up to 260 microM using an XTT dye reduction assay.

Antiviral Agents↗
PubMed1996

Risk factors for initiation of drug use among young males in southwest China.

To identify risk factors for drug use among young males in southwest China a cross-sectional survey and a non-concurrent cohort study were conducted. Demographic, behavioral and drug-use information was collected from young males aged 18-29 years. The non-concurrent cohort included the period 1 January 1991 to 1 August 1994. A total of 1548 subjects were interviewed. The cumulative incidence increased between 1991 and 1993. Multivariate analysis identified the following significant risk factors for drug use: being divorced/widowed/separated, having been encouraged by friends/others to try drugs, smoking cigarettes, belonging to the Jingpo ethnic group, and having a family member who used drugs in 1991. More than 6 years of education was a protective factor for drug use. Drug use in the community was associated with having been encouraged by friends or others to try drugs (71%), to smoking cigarettes (50%), and to belonging to the Jingpo group (24%). The results are consistent with community based prevention approaches which should be studied carefully because of the unique cultural and epidemiological situation in China.

Adolescent↗
PubMed1996

Strong, constitutive expression of the Arabidopsis ACT2/ACT8 actin subclass in vegetative tissues.

Arabidopsis has a complex and ancient actin gene family encoding six divergent subclasses of proteins. One subclass is represented by ACT2 and ACT8, which encode nearly identical proteins. These two genes differ significantly in flanking and intron sequences and in silent nucleotide positions within codons. Gene-specific RNA gel blot hybridization and reverse transcriptase-mediated polymerase chain reaction (RT-PCR) assays showed that ACT2 and/or ACT8mRNAs were coordinately and strongly expressed in leaves, roots, stems, flowers, pollen, and siliques. Together they account for greater than 80% of the actin mRNA in most Arabidopsis organs. The 5' flanking regions, including the promoter, the mRNA leader exon, an intron in the mRNA leader, and the first 19 codons, were coupled to a beta-glucuronidase (GUS) reporter gene and transformed into Arabidopsis. The ACT2/GUS construct was expressed strongly in nearly all the vegetative tissues in seedlings, juvenile plants, and mature plants. These activities persisted in older tissues. Little or no expression was observed in seed coats, hypocotyls, gynoecia, or pollen sacs. In contrast, the expression of the ACT8/GUS construct was weaker. It was observed only in a subset of the organs and tissues expressing ACT2/GUS and was not significantly expressed in the flower. ACT2, ACT8, and ACT8/GUS mRNAs were present at moderate to high levels in pollen, and yet neither ACT2/GUS nor ACT8/GUS enzyme expression could be detected in pollen. This suggested a mechanism of translational control affecting ACT2 and ACT8 expression in some tissues. The conservation of protein sequence and overlapping patterns of expression, in spite of significant DNA sequence divergence, suggests that the function and regulation of these two genes have been conserved during the evolution of the Brassicaceae.

Actins↗
PubMed1996

The Arabidopsis thaliana ACT4/ACT12 actin gene subclass is strongly expressed throughout pollen development.

Plants contain complex actin gene families composed of several diverse and ancient subclasses of genes. One Arabidopsis actin gene subclass represented by the ACT4 and ACT12 genes has been isolated and characterized. Both actin genes have typical plant actin gene structures, including three small introns interrupting the coding region and an intron within the mRNA leader. Their encoded proteins differ from each other in only one amino acid, whereas they differ in 3-10% of their amino acids from the other five Arabidopsis actin subclasses. They also share a few small blocks of DNA sequence homology in the 5' flanking region near their TATA boxs, but not in their introns, 3' flanking regions, or degenerate positions within codons. Southern analysis with gene-specific probes from 5' flanking sequences showed that both were single copy genes in the genome. Both RNA gel blot analysis with 3' gene-specific probes and reverse transcriptase-mediated polymerase chain reactions (RT-PCR) with gene-specific primers detected low levels of ACT4 and ACT12 mRNAs in flowers and very high levels in pollen. The RT-PCR detected very low levels of these mRNAs in the vegetative organs. The 5' region from both genes, including the promoter region, TATA box, the sequence for the mRNA leader and its intron, and the first 19 actin codons, was fused to a beta-glucuronidase (GUS) reporter gene. Expression of the GUS fusions were examined histochemically in 40 independent transgenic Arabidopsis plants. Expression of the ACT4/GUS fusion was restricted to young vascular tissues, tapetum, and developing and mature pollen. Similar expression patterns in these tissues and cell types were observed for ACT12/GUS fusion, yet unlike ACT4, ACT12 was also strongly expressed in the root cap and in a ring of pericycle tissues during lateral root initiation and early development. The unique expression patterns of the ACT4/ACT12 actin gene subclass are discussed in light of recent data on the other expressed members of the Arabidopsis actin gene family.

Actins↗
PubMed1996

Intron-dependent recruitment of pre-mRNA splicing factors to sites of transcription.

We have examined the nuclear localization of transiently and stably expressed nascent RNA transcripts containing or lacking introns in order to determine if the spatial association of RNA transcripts and pre-mRNA splicing factors in nuclei is random or functionally significant. Our findings show that the association between nascent RNA and splicing factors in the nucleus is intron-dependent when the RNAs are either transiently or stably expressed. Furthermore, our data indicate that splicing factors are recruited to the transcription sites. The presence of both pre-and mRNA at these locations suggest that pre-mRNA splicing occurs at these sites of transcription. In addition, electron microscopic examination of the highly active transcription sites has revealed a granular appearance which closely resembles, but is functionally different from, interchromatin granule clusters. Our findings demonstrate that the nucleus is highly organized and dynamic with regard to the functions of the transcription and pre-mRNA splicing.

Cell Nucleus↗
PubMed1996

Sevoflurane degradation to compound A in anaesthesia breathing systems.

Determination of an effective rate constant and activation energy allowed the application of steady-state theory to predict concentrations of compound A from sevoflurane concentrations, fresh gas flow rate, absorbent temperature and amount of absorbent. Studies by eight research groups were compared. Lower concentrations of compound A than predicted were observed at low flow rates, suggesting that its degradation by the absorbent is important in limiting the maximum observed concentrations in closed and low-flow breathing systems. Trial-to-trial and batch-to-batch variations in compound A concentrations were observed in model system tests of commercial and pilot-plant absorbents. Chemical modification of the absorbent with glycerol lowered concentrations of compound A, possibly by formation of a nucleophilic addition product. An ideal chemical scavenger would remain stable and non-volatile in the absorbent before irreversibly reacting with compound A to form a stable non-volatile product.

Absorption↗
PubMed1996

Structure and evolution of the actin gene family in Arabidopsis thaliana.

Higher plants contain families of actin-encoding genes that are divergent and differentially expressed. Progress in understanding the functions and evolution of plant actins has been hindered by the large size of the actin gene families. In this study, we characterized the structure and evolution of the actin gene family in Arabidopsis thaliana. DNA blot analyses with gene-specific probes suggested that all 10 of the Arabidopsis actin gene family members have been isolated and established that Arabidopsis has a much simpler actin gene family than other plants that have been examined. Phylogenetic analyses suggested that the Arabidopsis gene family contains at least two ancient classes of genes that diverged early in land plant evolution and may have separated vegetative from reproductive actins. Subsequent divergence produced a total of six distinct subclasses of actin, and five showed a distinct pattern of tissue specific expression. The concordance of expression patterns with the phylogenetic structure is discussed. These subclasses appear to be evolving independently, as no evidence of gene conversion was found. The Arabidopsis actin proteins have an unusually large number of nonconservative amino acid substitutions, which mapped to the surface of the actin molecule, and should effect protein-protein interactions.

Actins↗
PubMed1996

Risk factors for intravenous drug use and sharing equipment among young male drug users in Longchuan County, south-west China.

OBJECTIVES: To identify the risk factors for intravenous drug use and sharing of equipment in Longchuan County in south-west China. METHODS: Demographic information and sexual and drug-use-related behavior between 1 January 1991 and 1 August 1994 were collected retrospectively from a cohort of young male drug users aged 18-29 years in 82 villages. RESULTS: A total of 433 drug users were identified. The cumulative incidence of intravenous drug use was 40.0% during the 3.7-year study period. The annual incidence increased from 10% in 1991 to over 30% in 1994. Risk factors for intravenous drug use among drug users, according to the multivariate model, included having had premarital/extramarital sex [odds ratio (OR), 1.5; 95% confidence interval (CI), 1.01-2.3], having a family member who used drugs in 1991 (OR, 1.8; 95% CI, 1.1-2.9), and currently not married (OR, 1.6; 95% CI, 0.98-2.7). Being Buddhist protected against intravenous drug use (OR, 0.4; 95% CI, 0.2-0.9). The population attributable fraction was 30% for not being currently married, 17% for having had premarital/extramarital sex and 14% for having a family member who used drugs. The risk factor for sharing of equipment was being of Jingpo ethnicity (OR, 5.8; 95% CI, 2.5-13.8). The average incidence of sharing equipment was 19.6% per year. The population attributable fraction for sharing equipment was 58.5% for being Jingpo. CONCLUSIONS: The incidence of intravenous drug use and sharing equipment is increasing. Therefore, it is urgent that vigorous, effective intervention programs be initiated in southern Yunnan. Unmarried, sexually promiscuous Jingpo drug users with a family history of drug use should be especially targeted. Given the problems of transport and communication in this remote area of China, intervention programs which use existing social, governmental and community networks should be implemented.

Adolescent↗