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Biomedical subjects

X Huang

Publications and source records attributed to X Huang.

At least 505 records · Page 28Linked to original sources
PubMed1997

[The role of MMP-2 in the invasion and metastasis of hepatocellular carcinoma (HCC)].

OBJECTIVES: To get insights into the role of MMP-2 in the invasion and metastasis of hepatocellular carcinoma (HCC), and to find a method to judge the invasion and metastasis of HCC through MMP-2. METHODS: Zymograph and immunohistochemistry were used to study the content and types of positive cells of MMP-2 in the HCC, and statistical methods were used to analyse the association between the content of MMP-2 and the pathological indexes of HCC. RESULTS: MMP-2 was expressed by all the normal liver, HCC and surrounding liver parenchyma. The increase of MMP-2 and the presence of the active type of MMP-2 were related to the invasion and metastasis of HCC. The content of MMP-2 in HCC being higher than that in surrounding liver parenchyma was an important index to judge the invasion and metastasis of the HCC. The positive cells of MMP-2 found in immunohistochemistry were normal hepatocytes, cholangioepithelial cells, Ito cells, regenerated hepatocytes, new generated cholangioepithelial cells, and HCC cells. CONCLUSION: MMP-2 was related to the invasion and me astasis of HCC. The content of MMP-2 in HCC being higher than that in surrounding liver parenchyma could be bused as an important index to judge the invasion and metastasis of HCC.

Carcinoma, Hepatocellular↗
PubMed1997

[Experimental in vivo passage of H2 strain of live attenuated vaccine of hepatitis A in common marmosets].

Common marmosets with negative serum antibodies against hepatitis A virus (anti-HAV) and normal liver functions were used for the tests of passage of H2 vaccine strain of HAV to explore its residual virulence after attenuation and possibility of its reversion. Common marmosets were inoculated with attenuated live vaccine, and fecal suspension and/or proliferative liquid in tissue culture of the progeny of vaccine HAV excreted from their feces were passaged in common marmosets. Result of three serial passages in vivo indicated that there was no significant difference in serum anti-HAV titer, and no or low-level changes in activities of liver enzymes, no pathological changes in liver tissues observed, and detectable but minimal HAV was shed in stool of the all animals.

Animals↗
PubMed1997

[Serotyping of hemorrhagic fever with renal syndrome in Hubei province].

Ninety-two serum specimens, positive for antibodies against hemorrhagic fever with renal syndrome (HFRS) virus in initial screening with immunofluorescence assay technic (IFAT), were serotyped with micro cell pathogenic effects neutralization test based on preliminary epidemiological classification of epidemic foci of HFRS throughout the province to find out serological evidence of HFRS typing in Hubei Province. It was found that 48 of the specimens were belonged to Type I (HTN) accounting for 52.18 percent, 29 Type II (SEO) for 31.52 percent, and 15 undefined for 16.30 percent. Hubei Province was classified serologically as a mixed prevalent area with Type I as its major component, but all serotypes in different sub-areas have their own features and those in the old epidemic foci were more complex. It indicated that it was better to use a bivalent HFRS virus vaccine, or a single-valent vaccine consistent with local serotype. Serotyping of local HFRS conformed basically to that of epidemiological classification. Local HFRS should be serotyped periodically due to continuous changes in types of foci. Attention to reactions of vaccine immunization should be paid during observation of the effectiveness of the vaccine.

China↗
PubMed1997

[Effect of sijunzi decoction on motilin and pharmacokinetic characteristics of tetramethylpyrazine in rat model of spleen deficiency syndrome].

OBJECTIVE: To explore relationship between the essence of Spleen Deficiency Syndrome (SDS) and pharmacokinetic characteristics (PK). METHODS: The level of motilin in serum and intestine, and PK of tetramethylpyrazine phosphate (TMPP) in rat model of SDS were observed simultaneously and treated with Sijunzi decoction (SJZD) for confirmation. RESULTS: The atrioventricular model of TMPP in SDS, normal and SJZD treated rats all belonged to the open double ventricular type; there were insignificant differences between normal and SJZD treated rats in motilin level and PK of TMPP, but the differences of these parameters between normal and SDS model rats were significantly (P < 0.01). The SDS state could markedly affect the absorption, distribution, metabolism and elimination of TMPP in rat; SJZD could normalize the abnormal PK of TMPP in SDS model rats. CONCLUSIONS: A supplementary scientific evidence for the hypothesis of "Pharmacokinetics of Syndrome Differentiation" is provided.

Animals↗
PubMed1996

Genetically unstable CXG repeats are structurally dynamic and have a high propensity for folding. An NMR and UV spectroscopic study.

Recent molecular genetics studies have revealed a correlation between spontaneous, progressive expansion of several DNA trinucleotide repeats and certain hereditary neurodegenerative diseases. Triplet repeat (TR) sequences may be present in structured forms that can mediate the processes interrupting normal cellular replication, transcription, or repair activities, eventually leading to gene mutation. Using high resolution NMR spectroscopy and other biophysical methods, we probed the solution structures and properties of single-stranded TR sequences. These studies have led to the discovery of a new duplex motif (e-motif), present in CCG repeats, and to the elucidation of the structure of the (CTG)3 duplex. In this paper we provide a global picture of the solution behavior of the human disease-related CXG (X = A, C, G, or T) and the comparison GXC (X = A, or T) TR sequences. All six triplet repeats form antiparallel duplexes. The mismatched bases in CAG and CGG repeat duplexes are rather flexible and they do not appear to form stable, paired conformations. By comparison, GAC repeat duplexes and their mismatched A residues are well-structured. Most interestingly, the structures of the disease-related CXG repeats exhibit a propensity for folding at chain lengths as short as 12 residues. Furthermore, the energy barrier for the formation of homo-duplexes from the corresponding complementary hetero-duplexes are much lower for the CXG TR sequences than for the GAC or GTC TR sequences. These results provide insights into the conformation and physiochemical properties of TR sequences. Thus, a basis is provided for further studies of the behavior of long TR sequences in an effort to elucidate the molecular mechanisms of in vivo expansion and function of TR sequences.

Base Composition↗
PubMed1996

The CBFbeta subunit is essential for CBFalpha2 (AML1) function in vivo.

The CBFbeta subunit is the non-DNA-binding subunit of the heterodimeric core-binding factor (CBF). CBFbeta associates with DNA-binding CBFalpha subunits and increases their affinity for DNA. Genes encoding the CBFbeta subunit (CBFB) and one of the CBFalpha subunits (CBFA2, otherwise known as AML1) are the most frequent targets of chromosomal translocations in acute leukemias in humans. We and others previously demonstrated that homozygous disruption of the mouse Cbfa2 (AML1) gene results in embryonic lethality at midgestation due to hemorrhaging in the central nervous system and blocks fetal liver hematopoiesis. Here we demonstrate that homozygous mutation of the Cbfb gene results in the same phenotype. Our results demonstrate that the CBFbeta subunit is required for CBFalpha2 function in vivo.

Alleles↗
PubMed1996

Structural studies of imidazole-cytochrome c: resonance assignments and structural comparison with cytochrome c.

Two-dimensional nuclear magnetic resonance spectroscopy (2D NMR) was used to obtain extensive proton resonance assignments of Im-cyt c complex which is a possible analog of a late folding intermediate of cytochrome c. Assignments were made nearly completely for the main-chain and the side-chain protons (all except Gly29). As starting points for the assignment of the Im-cyt c, a limited set of protons was initially assigned by use of 2D NMR magnetization transfer methods to correlated resonances in the Im-cyt c with assigned resonances in the native cyt c. The subsequent search focused on recognition of main-chain NOE connectivity patterns, with use of previously assigned residues to place NOE-connected segments within the amino acid sequence. The observed patterns of main-chain NOEs provided some structural information and suggested potentially significant differences between Im-cyt c and the native cyt c. Differences in NOEs involving side-chain protons were reported and analyzed. There was evidence for conformational changes induced by the breakage of Fe-S bond. It was concluded that the Im-cyt c had undergone a rearrangement of several regions forming the heme pocket of the protein. The structural understanding of these effects of the mutation may be essential to elucidate the changes in function and kinetic mechanism of cyt c folding.

Animals↗
PubMed1996

A neurotransmitter transporter encoded by the Drosophila inebriated gene.

Behavioral and electrophysiological studies on mutants defective in the Drosophila inebriated (ine) gene demonstrated increased excitability of the motor neuron. In this paper, we describe the cloning and sequence analysis of ine. Mutations in ine were localized on cloned DNA by restriction mapping and restriction fragment length polymorphism (RFLP) mapping of ine mutants. DNA from the ine region was then used to isolate an ine cDNA. In situ hybridization of ine transcripts to developing embryos revealed expression of this gene in several cell types, including the posterior hindgut, Malpighian tubules, anal plate, garland cells, and a subset of cells in the central nervous system. The ine cDNA contains an open reading frame of 658 amino acids with a high degree of sequence similarity to members of the Na+/Cl(-)-dependent neurotransmitter transporter family. Members of this family catalyze the rapid reuptake of neurotransmitters released into the synapse and thereby play key roles in controlling neuronal function. We conclude that ine mutations cause increased excitability of the Drosophila motor neuron by causing the defective reuptake of the substrate neurotransmitter of the ine transporter and thus overstimulation of the motor neuron by this neurotransmitter. From this observation comes a unique opportunity to perform a genetic dissection of the regulation of excitability of the Drosophila motor neuron.

Amino Acid Sequence↗
PubMed1996

Structural comparison of a 15 residue peptide from the V3 loop of HIV-1IIIb and an O-glycosylated analogue.

As part of a program to study the effect of glycosylation on the three-dimensional structures of HIV-1IIIB V3 peptide constructs, we have examined the solution structures of a 15 residue peptide (RIQRGPGRAFVTIGK, P18IIIB)- originally mapped as an epitope recognized by CD8+ Dd class I MHC-restricted murine cytotoxic T-lymphocytes (CTL), and an analogue (P18IIIB-g), O-glycosylated with an alpha-galactosamine on Thr-12, using NMR, circular dichroism and molecular modeling methods. Our studies show that the peptides sample mainly random conformations in aqueous solution near 25 degrees C and become more ordered by the addition of trifluoroethanol. Upon decreasing the temperature to 5 degrees C, a reverse turn is formed around the immunodominant tip (G5-R8). Glycosylation on T12 'tightens' the turn slightly as suggested by NOE and CD analysis. In addition, the sugar has a defined conformation with respect to the peptide backbone and influences the local peptide conformation. These data suggest that simple glycosylation may influence the conformational equilibrium of a V3 peptide which contains a domain critical for antibody recognition and virus neutralization. We also show that the ability of cytotoxic T-lymphocytes (CTL) to lyse tumor cells presenting P18IIIB was completely abrogated by threonine glycosylation.

Amino Acid Sequence↗
PubMed1996

Cloning of the cDNA for rabbit L-selectin and expression of recombinant protein with a kinase target site to facilitate radiolabeling.

The cDNA encoding rabbit L-Selectin has been cloned from a cDNA library, utilizing a PCR-derived probe. It encodes a peptide of 377 amino acids, including a signal peptide of 38 amino acids. Sequence analysis demonstrated extensive homology with L-Selectin's from other species. Recombinant rabbit L-Selectin protein was expressed in eukaryotic cells in a chimeric construct incorporating the entire extracellular portion of the protein coding region, a phosphokinase target site to allow high activity radiolabeling with 32P, and the constant region of the heavy chain of human IgG1 to facilitate purification and detection. Amino-terminal peptide sequencing of recombinant L-Selectin confirmed that the signal peptide had been removed at the expected site.

Amino Acid Sequence↗
PubMed1996

2D-NMR studies of the effects of axial substitution on two helices in horse cytochrome c.

The sequential amino acids from Gly-1 to Cys-14 in the N-terminal segment and from Lys-88 to Glu-104 in the C-terminal segment of cytochrome c-imidazole complex (Im-cyt c) have been studied by two-dimensional nuclear magnetic resonance techniques. Resonance assignments for the main-chain and side-chain protons are reported. Qualitative interpretation of nuclear Overhauser enhancement data allows the secondary structure of the two segments to be described, which indicate the patterns of NOEs found are consistent with an alpha-helix between Val-3 and Cys-14 in the N-terminus, and between Lys-88 and Asn-103 in the C-terminus. Two alpha-helices are found to be maintained. Comparison of the long-range NOEs of Im-cyt c relative to the crystal structure of native cytochrome c reveals apparent conformational changes of some side-chains especially those close to heme pocket within the N- and C-terminal helices resulting from the binding of imidazole to iron by displacing native Met-80 side-chain. The explanation for ligand-induced changes within the N- and C-helices is therefore suggested.

Amino Acid Sequence↗
PubMed1996

Characterization of products from the reactions of N-acetyldopamine quinone with N-acetylhistidine.

When insects harden or sclerotize their exoskeletons, quinones of N-acetylated catecholamines such as N-acetyldopamine (NADA) undergo nucleophilic addition reactions with amino acids such as histidine in cuticular proteins. To determine the products that might form when this type of reaction occurs during cuticle sclerotization, the reactions between electrochemically prepared NADA quinone and N-acetylistidine (NAcH), a protein model nucleophile, have been investigated at pH 7. Two major products, 6-[N-(N-acetylhistidyl)]-N-acetyldopamine and 2-[N-(N-acetylhistidyl)]-N-acetyldopamine, were purified by semipreparative reversed-phase liquid chromatography and identified by mass spectrometry and nuclear magnetic resonance spectroscopy. The relative molar ratio of the C(6) mono-addition adduct to the C(2) mono-addition adduct is 87:13. UV/vis spectroscopic analysis shows that both products have an absorption maximum at 284 nm. Cyclic voltammetry shows that these adducts are oxidized less readily than NADA.

Benzoquinones↗
PubMed1996

An improved sequence assembly program.

We describe a number of improvements to the CAP sequence assembly program. These improvements include the development of methods for solving the problem caused by simple repetitive sequences, for automatically editing fragment alignments and consensus sequences, and for identifying chimeric fragments. The improved program (CAP2) assembled each of seven data sets, six of which contain repetitive sequences of very strong similarity, into a single sequence. As an example, CAP2 assembled a set of 1467 fragments into a single sequence of 73,328 bp that has only eight differences from the original sequence. The effects of fragment length, coverage, and error rate on the performance of CAP2 were evaluated using artificial data sets.

Algorithms↗
PubMed1996

Patterns of bone strain in the zygomatic arch.

BACKGROUND: The transmission of force through the skull is complicated by the irregular form of the bones, the interposed sutures, and the multiplicity of loads from the teeth, muscles, and environment. The in vivo relationship between bone strain and muscle function in the mammalian skull is best investigated empirically. METHODS: We studied the zygomatic arch of pigs (Sus scrofa) by simultaneous strain gauge recording and electromyography. Seventeen juvenile animals were used, employing multiple strain gauges arranged either in rosettes or strips. Strain was recorded during mastication and muscle stimulations. Bony architecture was examined on sectioned specimens. RESULTS: Strain patterns were complex even in this beamlike structure. During masseteric contraction, the more anterior zygomatic bone showed in-plane bending such that its lower border became more convex, and the major principal strain axis (tension) was parallel to the masseter muscle. The posterior squamosal bone was slightly bent in the opposite direction, and the major principal strain was rotated 45-60 degrees from the masseteric line of action. Strain magnitudes in the squamosal were larger than those in the zygomatic. Woven bone composing the surface of the arch appeared denser in the zygomatic bone, where its predominant orientation corresponded with compressive strain. In the squamosal bone trabeculae were more regularly arranged, but their orientation did not correspond with strain axes. CONCLUSIONS: The magnitude differences are probably related to the different architecture of the zygomatic and squamosal bones, whereas the different strain patterns primarily reflect the influence of the sutures in selectively damping or transmitting loads. In particular, the zygomatic bone may be loaded by three-point, distributed-load bending, whereas the squamosal, loaded at only two points, may be sheared. We conclude that each cranial bone functions in a unique strain environment, with the sutures serving to redirect loading.

Animals↗
PubMed1996

Peroxidase deficiency of nickel-transformed hamster cells correlates with their increased resistance to cytotoxicity of peroxides.

Using a procedure aimed at isolation of genes that are inactivated during nickel-induced carcinogenesis in Chinese hamster cells, a homolog of genes encoding human and mouse heme containing peroxidases has been cloned. Northern blot analysis of normal cultured fibroblasts and two nickel-transformed cell lines confirmed that this gene was expressed in normal but not in transformed cells. Nickel-transformed cells also tested negative for peroxidase activity using a sensitive fluorescence assay. Cultured embryo cells or fibroblasts that express peroxidase activity and their nickel-transformed peroxidase-deficient counterparts were employed to investigate the role of peroxidase-catalyzed processes in cytotoxicity induced by tert-butyl hydroperoxide or cumene hydroperoxide. It has been found that peroxidase-deficient cells were significantly more resistant to cytotoxic effect of these compounds suggesting that cytotoxic effect of hydroperoxides may be mediated in part by free radicals generated in the course of peroxidase-catalyzed reactions.

Animals↗
PubMed1996

Effect of domestically-made levonorgestrel-releasing intrauterine device on the endocrine system and menstruation in monkeys.

Effect of domestically-made levonorgestrel-releasing intrauterine device (LNG, release rate, 6 micrograms/day) on the endocrine system and menstruation in monkeys was investigated. The results showed that the Estradiol (E2) and progesterone (P) levels were significantly decreased 2 ovulatory cycles after insertion of the devices as compared with those before insertion in 3 monkeys (P > 0.001), suggesting an evident ovulation-suppressing effect. In 1 monkey, the E2 and P levels were the same before and after insertion, and expulsion of device was found in the monkey later. The plasma LNG concentration in 3 animals was 493.69-454.60 pg/ml and plasma LNG was not detected in 1 monkey. The hormone level returned to normal level after removal of the devices.

Animals↗
PubMed1996

Stereoselective pharmacological effects of lysergic acid amides possessing chirality in the amide substituent.

Studies of the affinities for serotonin 5-HT2A and 5-HT1A receptor subtypes of lysergic acid amides prepared from chiral 2-aminoalkanes showed a stereoselective preference at both receptor types for the amides with alkyl groups containing the R configuration. The 5-HT2A receptor was less tolerant of long alkyl groups than was the 5-HT1A subtype. In vivo assays in rats trained to discriminate LSD from saline also showed that amides with alkyl groups having the R configuration were most potent.

Animals↗