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Biomedical subjects

Li Huang

Publications and source records attributed to Li Huang.

At least 91 records · Page 5Linked to original sources
PubMed2003

The role of Six1 in mammalian auditory system development.

The homeobox Six genes, homologues to Drosophila sine oculis (so) gene, are expressed in multiple organs during mammalian development. However, their roles during auditory system development have not been studied. We report that Six1 is required for mouse auditory system development. During inner ear development, Six1 expression was first detected in the ventral region of the otic pit and later is restricted to the middle and ventral otic vesicle within which, respectively, the vestibular and auditory epithelia form. By contrast, Six1 expression is excluded from the dorsal otic vesicle within which the semicircular canals form. Six1 is also expressed in the vestibuloacoustic ganglion. At E15.5, Six1 is expressed in all sensory epithelia of the inner ear. Using recently generated Six1 mutant mice, we found that all Six1(+/-) mice showed some degree of hearing loss because of a failure of sound transmission in the middle ear. By contrast, Six1(-/-) mice displayed malformations of the auditory system involving the outer, middle and inner ears. The inner ear development in Six1(-/-) embryos arrested at the otic vesicle stage and all components of the inner ear failed to form due to increased cell death and reduced cell proliferation in the otic epithelium. Because we previously reported that Six1 expression in the otic vesicle is Eya1 dependent, we first clarified that Eya1 expression was unaffected in Six1(-/-) otic vesicle, further demonstrating that the Drosophila Eya-Six regulatory cassette is evolutionarily conserved during mammalian inner ear development. We also analyzed several other otic markers and found that the expression of Pax2 and Pax8 was unaffected in Six1(-/-) otic vesicle. By contrast, Six1 is required for the activation of Fgf3 expression and the maintenance of Fgf10 and Bmp4 expression in the otic vesicle. Furthermore, loss of Six1 function alters the expression pattern of Nkx5.1 and Gata3, indicating that Six1 is required for regional specification of the otic vesicle. Finally, our data suggest that the interaction between Eya1 and Six1 is crucial for the morphogenesis of the cochlea and the posterior ampulla during inner ear development. These analyses establish a role for Six1 in early growth and patterning of the otic vesicle.

Animals↗
PubMed2003

Potential drug targets on the HIV-1 envelope glycoproteins, gp120 and gp41.

HIV-1 entry is an attractive target for anti-HIV-1 therapy. However, there are no entry inhibitors approved for the clinical treatment of HIV-1 infection. This is likely to be changed in the near future since promising HIV-1 entry inhibitors, such as T20 and some chemokine receptor antagonists, are in the pipeline to join the repertoire of anti-HIV-1 therapeutics. This review will focus on what might be potential targets on the key components of the viral entry machinery, gp120 and gp41. These two molecules are the viral proteins responsible for HIV-1 entry. Binding to CD4 induces a series of structural changes in gp120 and allows it to interact with chemokine receptors. The receptor binding eventually triggers conformational changes in gp41, which result in the formation of a fusion active molecule to attack the cell membrane. The structural and functional motifs that operate this delicate fusion machinery could become the Achilles' heel of the virus.

HIV Envelope Protein gp120↗
PubMed2003

Malignant peripheral nerve sheath tumor with divergent differentiation.

Right posterior thigh malignant peripheral nerve sheath tumor with malignant glandular and rhabdomyoblastic components was diagnosed in a 24-year-old African American man. Malignant glands and rhabdomyoblastic cells were admixed with the spindle cells. Immunohistochemistry demonstrated spindle cells positive for S100 and vimentin; the glandular component was positive for chromogranin, and rare cells were positive for CK20 but negative for CK7. Rhabdomyoblastic cells were positive for muscle-specific actin and desmin. A single pulmonary metastasis occurred 5 months after surgical resection of the tumor. Death occurred 1 month later and was probably due to a pulmonary embolus.

Adult↗
PubMed2003

[Preparation of liposome containing bacteriorhodopsin with natural preferred orientation of its transient photoresponse].

Bacteriorhodopsin is a membrane protein of halobacteria and functions as a light-driven protein pump. After we isolated bR from cultured halobacteria, bR was mixed with amphiphilic DPPC under different pH. The liposomes were formed after sonication. The remaining biological activity of bR as a proton pump was then verified and pulsed-light-induced proton movement was detected, while liposomes were observed via TEM and light scattering. Although there was no noticeable difference in morphologies of both vesicles formed at pH=2.5 and pH=7.0, the orientations of bR in both liposomes were found to be opposite under these two conditions. This experiment confirmed that the protein bR, when self-assembling into liposomes under acid medium, kept the similar orientation as in the natural plasmid membrane. Such a normal-orientation was, however, different from most of reports in the literature about liposomes prepared under normal neutral conditions.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2003

[The application of Chinese health questionnaire for mental disorder screening in community settings in mainland China].

OBJECTIVE: To examine the applicability of Chinese Health Questionnaire (Taiwan version) (CHQ) originated from General Health Questionnaire (GHQ) for mental disorder screening in community settings in mainland China. METHODS: A pilot study was conducted in Hangzhou (n = 377). Three thousand seven hundred and seven subjects were recruited from four cities to validate the results of the pilot study. Validation of the Screening Questionnaire was analyzed, using Relative Operating Characteristic (ROC) method. RESULTS: Cronbach's alpha coefficients were calculated to be 0.79 for the 12-items and 0.89 for 30-items to CHQ version in the first sample, and 0.74 in the second sample (12-items). Four factors were extracted from the CHQ-30, including somatic symptoms, anxiety and worry, social dysfunction, poor family relationship, and depression. CHQ-12 could be explained by a single factor in both samples. The areas under ROC were 0.80 (95% CI: 0.70 - 0.89) for 12 items and 0.72 (95% CI: 0.62 - 0.82) for 30 items. The sensitivities of CHQ-12 and CHQ-30 were found to be 76.9% and 71.8%, and the specificities were 73.8% and 67.9% with Kappa value 0.44 (P = 0.00) and 0.38 (P = 0.00), respectively. The estimated rates of mental disorder were 18.13% (95% CI: 14.16 - 22.10) by CHQ-12, and 22.80% (95% CI: 18.19 - 27.11) by CHQ-30 in the first sample and the rates were 21.72% (95% CI: 20.39 - 23.05) by CHQ-12 in the second sample. CONCLUSION: CHQ, especially CHQ-12 through slight language modification, could be used for epidemiological studies and on community health care to screen for mental disorder in the mainland of China.

Adult↗
PubMed2003

[Analysis of sterile male semen of occupational drivers].

OBJECTIVE: To explore the possible correlation between the driver's occupation and male semen quality. METHODS: Semen samples were collected from 1,223 infertile men (78 drivers and 1,145 non-drivers) and 100 normal men, and their liquefaction, sperm density, sperm vitality, sperm motility and sperm shape were analysed. RESULTS: The abnormal rates of semen quality in sterile male drivers were significantly higher than in non-drivers(P < 0.05) and in normal men(P < 0.01). The semen abnormal rates in drivers with more than 8 years' driving experience were higher than in those with less than 8 years' driving experience(P < 0.05). CONCLUSION: Driving occupation can result in abnormal semen quality.

Adult↗
PubMed2002

Biochemical characterization of an ATP-dependent DNA ligase from the hyperthermophilic crenarchaeon Sulfolobus shibatae.

A gene encoding a putative ATP-dependent DNA ligase was identified in the genome of the hyperthermophilic archaeon Sulfolobus shibatae and expressed in Escherichia coli. The 601 amino acid recombinant polypeptide was a monomeric protein capable of strand joining on a singly nicked DNA substrate in the presence of ATP ( K(m)=34 micro mu) and a divalent cation (Mn(2+), Mg(2+), or Ca(2+)). dATP was partially active in supporting ligation catalyzed by the protein, but GTP, CTP, UTP, dGTP, dCTP, dTTP, and NAD(+) were inactive. The cloned Ssh ligase showed an unusual metal cofactor requirement; it was significantly more active in the presence of Mn(2+) than in the presence of Mg(2+) or Ca(2+). Unexpectedly, the native Ssh ligase preferred Mg(2+) and Ca(2+) rather than Mn(2+). Both native and recombinant enzymes displayed optimal nick-joining activity at 60-80 degrees C. Ssh ligase discriminated against substrates containing mismatches on the 3'-side of nick junction and was more tolerant of mismatches at the 5'-end than of those at the penultimate 5'-end. The enzyme showed little activity on a 1-nucleotide gapped substrate. This is the first biochemical study of a DNA ligase from the crenarchaeotal branch of the archaea domain.

Adenosine Triphosphate↗
PubMed2002

Structure of a tethered cationic 3-aminopropyl chain incorporated into an oligodeoxynucleotide: evidence for 3'-orientation in the major groove accompanied by DNA bending.

The structure of the dodecamer d(CGCGAATXCGCG)(2), in which X = Z3dU, 5-(3-aminopropyl)-2'-deoxyuridine, was determined. At neutral pH, Z3dU introduced a positive charge into the major groove. NMR spectroscopy revealed that the Z3dU omega-aminopropyl moiety oriented in the 3'-direction from the site of modification. Watson-Crick base pairing remained intact throughout the dodecamer. The presence of the charged amino group in the major groove resulted in a 0.24 ppm upfield shift of one (31)P NMR resonance in the 3'-direction at the phosphodiester linkage between nucleotides C(9) and G(10). Molecular dynamics calculations restrained by distances obtained from (1)H NOE data and torsion angles obtained from (1)H NMR (3)J coupling data, and in which the omega-amino group was constrained to be proximate to G(10)O(6), predicted from the (31)P NMR data and molecular modeling (Dande, P.; Liang, G.; Chen, F.-X.; Roberts, C.; Nelson, M. G.; Hashimoto, H.; Switzer, C.; Gold, B. Biochemistry 1997, 36, 6024-6032), were consistent with experimental NOEs. These refined structures exhibited bending. The distance from the amino group to the 5'-phosphate oxygen of Z3dU was >5 A, which indicated that in this dodecamer the Z3dU amino group did not participate in a salt bridge to its 5'-phosphate.

DNA↗
PubMed2002

Expression, purification, crystallization and preliminary X-ray analysis of a DNA-binding protein from Methanococcus jannaschii.

A small DNA-binding protein of 87 amino-acid residues from the hyperthermophilic archaeon Methanococcus jannaschii (Mja10b) was cloned and overexpressed in Escherichia coli. The protein was crystallized and the crystals belong to the space group P6(1)22/P6(5)22, with unit-cell parameters a = b = 50.85, c = 124.02 A, alpha = beta = 90, gamma = 120 degrees. The crystals diffracted to a maximum resolution of 2.2 A at 100 K using Cu Kalpha radiation. The presence of one molecule per asymmetric unit gives a crystal volume per protein mass (V(M)) of 2.4 A(3) Da(-1) and a solvent content of 49% by volume. A full set of X-ray diffraction data was collected to 2.2 A from the native crystal.

Crystallography, X-Ray↗
PubMed2002

Lithocholic acid decreases expression of bile salt export pump through farnesoid X receptor antagonist activity.

Bile salt export pump (BSEP) is a major bile acid transporter in the liver. Mutations in BSEP result in progressive intrahepatic cholestasis, a severe liver disease that impairs bile flow and causes irreversible liver damage. BSEP is a target for inhibition and down-regulation by drugs and abnormal bile salt metabolites, and such inhibition and down-regulation may result in bile acid retention and intrahepatic cholestasis. In this study, we quantitatively analyzed the regulation of BSEP expression by FXR ligands in primary human hepatocytes and HepG2 cells. We demonstrate that BSEP expression is dramatically regulated by ligands of the nuclear receptor farnesoid X receptor (FXR). Both the endogenous FXR agonist chenodeoxycholate (CDCA) and synthetic FXR ligand GW4064 effectively increased BSEP mRNA in both cell types. This up-regulation was readily detectable at as early as 3 h, and the ligand potency for BSEP regulation correlates with the intrinsic activity on FXR. These results suggest BSEP as a direct target of FXR and support the recent report that the BSEP promoter is transactivated by FXR. In contrast to CDCA and GW4064, lithocholate (LCA), a hydrophobic bile acid and a potent inducer of cholestasis, strongly decreased BSEP expression. Previous studies did not identify LCA as an FXR antagonist ligand in cells, but we show here that LCA is an FXR antagonist with partial agonist activity in cells. In an in vitro co-activator association assay, LCA decreased CDCA- and GW4064-induced FXR activation with an IC(50) of 1 microm. In HepG2 cells, LCA also effectively antagonized GW4064-enhanced FXR transactivation. These data suggest that the toxic and cholestatic effect of LCA in animals may result from its down-regulation of BSEP through FXR. Taken together, these observations indicate that FXR plays an important role in BSEP gene expression and that FXR ligands may be potential therapeutic drugs for intrahepatic cholestasis.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2002

The amino acid residues asparagine 354 and isoleucine 372 of human farnesoid X receptor confer the receptor with high sensitivity to chenodeoxycholate.

The critical steps in bile acid metabolism have remarkable differences between humans and mice. It is known that human cholesterol 7 alpha-hydroxylase, the enzyme catalyzing the rate-limiting step of bile acid synthesis, is more sensitive to bile acid suppression. In addition, hepatic bile acid export in humans is more dependent on the bile salt export pump (BSEP). To explore the molecular basis for these species differences, we analyzed the function of the ligand-binding domain (LBD) of human and murine farnesoid X receptor (FXR), a nuclear receptor for bile acids. We observed a strong interspecies difference in bile acid-mediated FXR function; in the coactivator association assay, chenodeoxycholate (CDCA) activated human FXR-LBD with 10-fold higher affinity and 3-fold higher maximum response than murine FXR-LBD. Consistently, in HepG2 cells human FXR-LBD increased reporter expression more robustly in the presence of CDCA. The basis for these differences was investigated by preparing chimeric receptors and by site-directed mutagenesis. Remarkably, the double replacements of Lys(366) and Val(384) in murine FXR (corresponding to Asn(354) and Ile(372) in human FXR) with Asn(366) and Ile(384) explained the difference in both potency and maximum activation; compared with the wild-type murine FXR-LBD, the double mutant gained 8-fold affinity and more than 250% maximum response to CDCA in vitro. This mutant also increased reporter expression to an extent comparable with that of human FXR-LBD in HepG2 cells. These results demonstrate that Asn(354) and Ile(372) are critically important for FXR function and that murine FXR can be "humanized" by substituting with the two corresponding residues of human FXR. Consistent with the difference in FXR-LBD transactivation, CDCA induced endogenous expression of human BSEP by 10-12-fold and murine BSEP by 2-3-fold in primary hepatocytes. This study not only provides the identification of critical residues for FXR function but may also explain the species difference in bile acids/cholesterol metabolism.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2002

[A novel stop codon mutation in S gene: the molecular basis of a patient with cryptogenic cirrhosis].

OBJECTIVE: To explore the pathogen and molecular basis of cryptogenic cirrhosis in a patient. METHODS: Serum was collected from a patient, male, aged 56, with cryptogenic cirrhosis. HBV serologic markers were qualitatively tested, and HBsAg, HBeAg, and anti-HBc were quantitatively determined again. HBV DNA in serum was qualitatively tested using PCR, and quantified using fluorescence quantitative PCR. S gene was amplified, cloned, and sequenced. RESULTS: HbsAg and anti-Hbe were negative, and anti-HBs, HBeAg, anti-HBc, and HBV DNA were all positive. HBsAg (S/N) was 0.77 (cutoff of S/N: >/= 2.00), HbeAg (S/N) was 56.43 (cutoff of S/N: >/= 2.10), anti-HBc (S/C(O)) was 0.03 (cutoff of S/C(O): </= 1.00); HBV DNA was 1.54 x 10(9) copies/ml. An uncommon point mutation at nucleotide 336 (C to A) in S gene was found, resulting in the change of the 61st codon into a novel stop codon and failure of synthesis of HbsAg. CONCLUSION: HBV proves the pathogen of this case. This special mutation well explains the patient's unusual serologic pattern. Moreover, this finding possesses important clinical and theoretical significance.

Base Sequence↗
PubMed2002

Screen and identification of proteins interacting with ADAM19 cytoplasmic tail.

ADAM family plays important roles in neurogenesis. The cytoplasmic tail of ADAM19 (ADAM19-CT) contains 193 residues. The presence of two putative SH3 ligand-binding sites suggests potential interactions with cytosolic proteins, which could be possibly linked to the functions of ADAM19. To address these issues, a yeast two-hybrid screen was performed in human fetal brain cDNA library to isolate proteins that interact with the cytoplasmic tail of ADAM19. Four proteins were obtained, ArgBP1, beta-cop, ubiquitin and a novel protein. GST-Pulldown assay has confirmed the interaction between AdAM19 and ArgBP1. By constructing series of deletion mutants of ADAM19-CT and ArgBP1 respectively, the interaction regions have been identified. They are the SH3 binding sites in ADAM19-CT and the P4 region in ArgBP1. And the interaction is specific. ArgBP1 does not bind to ADAM22, ADAM29 or ADAM9 (mouse). ArgBP1 may be the key protein, which accounts for the physiological function of ADAM19.

ADAM Proteins↗
PubMed2002

Long-term pharmacokinetics of an extract of isoflavones from red clover (Trifolium pratense).

OBJECTIVES: To study the pharmacokinetics of isoflavones from red clover (Trifolium pratense) after long-term administration as a once-daily dietary supplementary. DESIGN: Fourteen (14) subjects who had been consuming a low-isoflavone diet for 2 weeks were given an oral dose of two isoflavone tablets (approximately 80 mg of total isoflavones) daily for 2 weeks and appeared for a study day at 9:00 AM after an overnight fast on the day that they were to receive the last dose. Plasma samples were collected for a 48-hour period after the last dose. Plasma isoflavones were assayed by high-performance liquid chromatography (HPLC). RESULTS: Trough plasma levels were significantly higher for daidzein and genistein after long-term dosing than levels taken prior to the commencement of the study and plasma levels of isoflavones after long-term dosing were in the range previously reported in populations that consume an isoflavone-rich diet. The plasma half-lives observed after long-term administration were, in most cases, consistent with once-daily administration. CONCLUSIONS: Isoflavones have pharmacokinetic characteristics that suggest that once-daily administration is adequate when they are administered long-term as dietary supplements.

Adult↗
PubMed2002

A complete sequence of the T. tengcongensis genome.

Thermoanaerobacter tengcongensis is a rod-shaped, gram-negative, anaerobic eubacterium that was isolated from a freshwater hot spring in Tengchong, China. Using a whole-genome-shotgun method, we sequenced its 2,689,445-bp genome from an isolate, MB4(T) (Genbank accession no. AE008691). The genome encodes 2588 predicted coding sequences (CDS). Among them, 1764 (68.2%) are classified according to homology to other documented proteins, and the rest, 824 CDS (31.8%), are functionally unknown. One of the interesting features of the T. tengcongensis genome is that 86.7% of its genes are encoded on the leading strand of DNA replication. Based on protein sequence similarity, the T. tengcongensis genome is most similar to that of Bacillus halodurans, a mesophilic eubacterium, among all fully sequenced prokaryotic genomes up to date. Computational analysis on genes involved in basic metabolic pathways supports the experimental discovery that T. tengcongensis metabolizes sugars as principal energy and carbon source and utilizes thiosulfate and element sulfur, but not sulfate, as electron acceptors. T. tengcongensis, as a gram-negative rod by empirical definitions (such as staining), shares many genes that are characteristics of gram-positive bacteria whereas it is missing molecular components unique to gram-negative bacteria. A strong correlation between the G + C content of tDNA and rDNA genes and the optimal growth temperature is found among the sequenced thermophiles. It is concluded that thermophiles are a biologically and phylogenetically divergent group of prokaryotes that have converged to sustain extreme environmental conditions over evolutionary timescale.

Bacillaceae↗
PubMed2002

Analysis of 106 kb of contiguous DNA sequence from the D genome of wheat reveals high gene density and a complex arrangement of genes related to disease resistance.

Vast differences exist in genome sizes of higher plants; however, gene count remains relatively constant among species. Differences observed in DNA content can be attributed to retroelement amplification leading to genome expansion. Cytological and genetic studies have demonstrated that genes are clustered in islands rather than distributed at random in the genome. Analysis of gene islands within highly repetitive genomes of plants like wheat remains largely unstudied. The objective of our work was to sequence and characterize a contiguous DNA sequence from chromosome IDS of Aegilops tauschii. An RFLP probe that maps to the Lr21 region of IDS was used to isolate a single BAC. The BAC was sequenced and is 106 kb in length. The contiguous DNA sequence contains a 46-kb retroelement-free gene island containing seven coding sequences. Within the gene island is a complex arrangement of resistance and defense response genes. Overall gene density in this BAC is 1 gene per 8.9 kb. This report demonstrates that wheat and its relatives do contain regions with gene densities similar to that of Arabidopsis.

Amino Acid Sequence↗
PubMed2002

Effect of the aqueous extract of xiao-ban-xia-tang on gastric emptying in mice.

Gastric emptying effect of the aqueous extract of xiao-ban-xia-tang (XBXT) was investigated in mice. Mice with food deprived for 18 hours were orally administered a certain amount of test meal (ca. 0.8 g) equaling 0.8 ml in volume. The percentage of 0.8 g test meal remaining in the stomach after 20 minutes was estimated. It was shown that XBXT significantly antagonized dopamine- (0.56 mg/kg, i.p.), not atropine- (0.3 mg/kg, i.p.), induced gastric emptying inhibition. It also significantly restored metoclopramide-induced (8 mg/kg, p.o.) propulsion and potentiated methylneostigmine-induced (2 mg/kg, p.o.) gastric emptying enhancement. The aqueous extract of Pinellia ternata, but not that of Zingiber officinale showed an inhibitory activity on gastric emptying. The present results suggest that XBXT possesses a regulative effect on gastric motility.

Administration, Oral↗