Biomedical subjects

K Huang

Publications and source records attributed to K Huang.

At least 55 records · Page 3Linked to original sources

PubMed2000

Nationwide vaccination: a success story in Taiwan.

In the early 1980s, 15-20% of the population of Taiwan were estimated to be hepatitis B virus (HBV) carriers. A programme of mass vaccination against hepatitis B was therefore launched in 1984. In the first 2 years, newborns of all HBVsurface antigen (HBsAg)-positive mothers were vaccinated. Since 1986, all newborns, and then year by year pre-school children, primary school children, adolescents, young adults and others have also been vaccinated. Vaccination coverage is over 90% for newborns, with 79% of pregnant women screened for HBsAg. The proportion of babies born to highly infectious carrier mothers who also became carriers decreased from 86-96% to 12-14%; the decrease was from 10-12% to 3-4% for babies of less infectious mothers. Between 1989 and 1993, the prevalence of HBsAg in children aged 6 years also fell from 10.5 to 1.7%. The average annual incidence of hepatocellular carcinoma in children aged 6-14 years decreased significantly from 0.7 per 100,000 in 1981-1986 to 0.36 per 100,000 in 1990-1994 (P<0.01). Similarly, the annual incidence of hepatocellular carcinoma in children aged 6-9 years declined from 0.52 per 100,000 for those born in 1974-1984 to 0.13 per 100,000 for those born in 1986-1988 (P<0.001). The mass vaccination programme is highly effective in controlling chronic HBV infection and in preventing liver cancer in Taiwan. If a coverage rate of 90% of all newborns vaccinated against hepatitis B can be maintained, by the year 2010 the carrier rate in Taiwan is expected to decline to <0.1%.

Adolescent↗

PubMed2000

Molecular cloning and functional characterization of the mouse mafB gene.

The Maf family of the transcription factors plays a pivotal role in controlling development and cellular differentiation. To clarify the molecular mechanisms controlling mafB expression, a genomic clone of the mouse mafB gene was isolated and analyzed. RNase protection analysis determined the transcription initiation site at 389 bp upstream from the translation initiation site. The 3' end of the gene is located at 946 bp downstream from the termination codon. The gene lacks intron structure. Sequence analysis showed a TATA-like sequence (5'-GATAAAA-3') and an inverted CCAAT-box (5'-ATTGG-3') in the promoter region. Upstream of these sequences, there are several potential regulatory elements, including two GC-boxes (5'-GGGCGG-3'), and a palindromic sequence (5'-GTCAGCTGAC-3') which contains two Maf recognition elements (MARE, 5'-GCTGAC-3') and an E-box (5'-CAGCTG-3'). Transient transfection analysis with the 5'-flanking region of the mafB gene demonstrated that these elements are important for mafB gene expression. In addition, cotransfection analysis indicated that the MyoD activates the mouse mafB promoter and the gene is positively auto-regulated by its own product.

Animals↗

PubMed2000

Novel mutations in 13 probands with galactokinase deficiency.

Galactokinase is an essential enzyme in the metabolism of galactose. Patients with deficiencies in galactokinase exhibit early-onset cataracts. We examined the sequence of the human galactokinase gene (GK1) from 13 patients exhibiting galactokinase deficiency and identified 12 novel mutations. One of the mutations occurred in six of the 13 probands examined, and the remaining 11 were unique mutations. Expression of each of the mutant GK1 genes in Xenopus oocytes resulted in very low galactokinase activity levels. These results provide important information regarding the types of GK1 mutations that occur in the human population.

Base Sequence↗

PubMed2000

Reactivation and refolding of reassociated dimers of rabbit muscle creatine kinase.

Creatine kinase (ATP:creatine N-phosphotransferase, EC 2.7.3.2) is a good model for studying dissociation and reassociation during unfolding and refolding. This study compares self-reassociated CK dimers and CK dimers that contain hybrid dimers under proper conditions. Creatine kinase forms a monomer when denatured in 6 M urea for 1 h which will very quickly form a dimer when the denaturant is diluted under suitable conditions. After modification by DTNB, CK was denatured in 6 M urea to form a modified CK monomer. Dimerization of this modified subunit of CK occurred upon dilution into a suitable buffer containing DTT. Therefore, three different types of reassociated CK dimers including a hybrid dimer can be made from two different CK monomers in the proper conditions. The CK monomers are from a urea-denatured monomer of DTNB-modified CK and from an unmodified urea dissociated monomer. Equal enzyme concentration ratios of these two monomers were mixed in the presence of urea, then diluted into the proper buffer to form the three types of reassociated CK dimers including the hybrid dimer. Reassociated CK dimers including all three different types recover about 75% activity following a two-phase course (k1 = 4.88 x 10(-3) s(-1), k2 = 0.68 x 10(-3) s(-1)). Intrinsic fluorescence spectra of the three different CK monomers which were dissociated in 6 M urea, dissociated in 6 M urea after DTNB modification, and a mixture of the first two dissociated enzymes were studied in the presence of the denaturant urea. The three monomers had different fluorescence intensities and emission maxima. The intrinsic fluorescence maximum intensity changes of the reassociated CK dimers were also studied. The refolding processes also follow biphasic kinetics (k1 = 3.28 x 10(-)3 s(-1), k2 = 0.11 x 10(-3) S(-1)) after dilution in the proper solutions. Tsou's method [Tsou (1988), Adv. Enzymol. Rel. Areas Mol. Biol. 61, 381-436] was also used to measure the kinetic reactivation rate constants for the different three types of reassociated CK dimers, with different kinetic reactivation rate constants observed for each type. CK dissociation and reassociation schemes are suggested based on the results.

Animals↗

PubMed2000

Nucleus-vacuole junctions in Saccharomyces cerevisiae are formed through the direct interaction of Vac8p with Nvj1p.

Vac8p is a vacuolar membrane protein that is required for efficient vacuole inheritance and fusion, cytosol-to-vacuole targeting, and sporulation. By analogy to other armadillo domain proteins, including beta-catenin and importin alpha, we hypothesize that Vac8p docks various factors at the vacuole membrane. Two-hybrid and copurfication assays demonstrated that Vac8p does form complexes with multiple binding partners, including Apg13p, Vab2p, and Nvj1p. Here we describe the surprising role of Vac8p-Nvj1p complexes in the formation of nucleus-vacuole (NV) junctions. Nvj1p is an integral membrane protein of the nuclear envelope and interacts with Vac8p in the cytosol through its C-terminal 40-60 amino acids (aa). Nvj1p green fluorescent protein (GFP) concentrated in small patches or rafts at sites of close contact between the nucleus and one or more vacuoles. Previously, we showed that Vac8p-GFP concentrated in intervacuole rafts, where is it likely to facilitate vacuole-vacuole fusion, and in "orphan" rafts at the edges of vacuole clusters. Orphan rafts of Vac8p red-sifted GFP (YFP) colocalize at sites of NV junctions with Nvj1p blue-sifted GFP (CFP). GFP-tagged nuclear pore complexes (NPCs) were excluded from NV junctions. In vac8-Delta cells, Nvj1p-GFP generally failed to concentrate into rafts and, instead, encircled the nucleus. NV junctions were absent in both nvj1-Delta and vac8-Delta cells. Overexpression of Nvj1p caused the profound proliferation of NV junctions. We conclude that Vac8p and Nvj1p are necessary components of a novel interorganelle junction apparatus.

Cell Fractionation↗

PubMed2000

Cleft palate repair at 3 to 7 months of age.

We report the speech outcome in 90 children with complete unilateral cleft lip and palate who underwent soft palate repair either between 3 and 7 months of age (n = 40) or later than 7 months of age (n = 50). In all patients, palatoplasty was performed by one of two experienced surgeons using a modification of the Furlow technique, and speech evaluations were conducted using the Pittsburgh Weighted Values for Speech Symptoms Associated with Velopharyngeal Incompetence by two speech pathologists with high inter-rater reliability. There were no differences between the groups with respect to resonance, nasal air emission, and articulation. Velopharyngeal function, as measured by the total speech score, was similar between the two groups of patients, as were the rates of secondary pharyngoplasty. These results suggest that very early closure of the soft palate may not offer significant benefit over repair later in infancy with respect to speech outcome.

Age Factors↗

PubMed2000

The flow-cytometric analysis of nasopharyngeal carcinoma treated with stereotactic radiosurgery.

Stereotactic radiosurgery has been used in the treatment of nasopharyngeal carcinoma. To analyze the effect of radiosurgery on the flow cytometry DNA index and progression of cells through the cycles, 4 recurrent nasopharyngeal carcinoma cases were treated with stereotactic radiosurgery. The distribution of cells through the cycles was measured by flow cytometry at various times thereafter. The 50% isodose curve was placed at the tumor margin and the margin dose was 20 Gy. Biopsy of the nasopharynx was performed before and 1, 3, and 6 months after treatment. The specimens were then subjected to flow-cytometric analysis. The percentage of cells in the S phase was 27.6 +/- 1.0, 14.6 +/- 0.8, 12.1 +/- 1.6 and 11.3 +/- 1.3%; the proliferating index was 39.1 +/- 1.4, 17.0 +/- 0.9, and 14.3 +/- 1.2 and 14.1 +/- 1.5%, and the DNA index was 1.5 +/- 0.1, 1.6 +/- 0.2, 1.7 +/- 0.1 and 1.9 +/- 0.1 before and 1, 3, and 6 months after treatment, respectively. It is suggested that the percentage of cells in the S phase and the proliferating index decreased to normal after treatment with stereotactic radiosurgery. This study explores the preliminary radiobiological effect of stereotactic radiosurgery on the DNA content and the distribution of cells through the cycles in nasopharyngeal carcinoma.

Aged↗

PubMed2000

Selenium deficiency-induced alterations in the vascular system of the rat.

To enunciate the mechanisms whereby Se protects against cardiovascular diseases, weanling male Wistar rats were fed deficient (0.022 mg/kg diet) and adequate (0.159 mg/kg diet) Se diets for 14 and/or 39 wk. As the Se content and glutathione peroxidase activity were decreased and the lipid peroxide level was increased, the plasma 6-keto-PGF1alpha concentration of the Se-deficient group was markedly decreased in blood and tissues of the Se-deficient rats, as compared with the Se-adequate animals. Furthermore, the Se-deficient group had significantly lower plasma nitric oxide content and vascular nitric oxide synthase activity, higher erythrocyte sedimentation equation K value and aggregation index, and lower erythrocyte deformability than the Se-adequate group. Experimental Se deficiency also resulted in significant increases in serum total cholesterol and low-density lipoprotein cholesterol levels and a significant decrease in serum high-density lipoprotein cholesterol level. These results give some experimental supports to the hypothesis that low Se status and lipid peroxidation are involved in the etiology of cardiovascular diseases.

6-Ketoprostaglandin F1 alpha↗

PubMed2000

HIV risk behaviors among Asian drug users in San Francisco.

This study identified patterns of drug use and HIV risk behaviors in relation to cultural factors among Asian drug users in San Francisco. A sample of 92 Asian drug users (35 Chinese, 31 Filipino, 26 Vietnamese) who were not currently enrolled in drug treatment programs were recruited through targeted sampling methods and interviewed using a questionnaire with open-ended questions. The study evaluated responses of the participants based on content analyses. Compared with Chinese and Vietnamese, Filipino drug users had engaged in riskier behaviors in terms of injection drug use, having sex while on drugs, and having sex with injection drug users (IDUs). Cultural factors such as stigma of injection drug use and fear of needles were cited as reasons for not injecting drugs. Among IDUs, half cited trust as a reason for having shared needles. AIDS prevention programs targeting Asian drug users should consider specific cultural factors among high-risk groups (i.e., Filipinos, immigrants, women, and IDUs).

Adult↗

PubMed2000

[Sequential non-invasive following short-term invasive mechanical ventilation in COPD induced hypercapnic respiratory failure].

OBJECTIVE: To estimate the feasibility and the efficacy of early extubation and sequential non-invasive mechanical ventilation(MV) in COPD with exacerbated hypercapnic respiratory failure. METHODS: 22 intubated COPD cases with severe hypercapnic respiratory failure due to pulmonary infection (pneumonia or purulent bronchitis) were involved in the study. At the time pulmonary infection had been significantly controlled (resolution of fever and decrease in purulent sputum, radiographic infiltrations, and leukocytosis. We call the time as "Pulmonary Infection Control Window", PIC window) after the antibiotic and the comprehensive therapy, the early extubation was conducted and followed by non-invasive MV via facial mask immediately in 11 cases (study group). Other 11 COPD cases with similar clinical characteristics who continuously received invasive MV after PIC window were used as control group. RESULTS: The groups had similar clinical characteristics and gas exchange, initially and at the time of PIC window. For study group and control group, the duration of invasive MV was (7.1 +/- 2.9) vs (23.0 +/- 14.0) days, P < 0.01; the total duration of ventilatory support was (13 +/- 7) vs (23 +/- 14) days, P < 0.05; the incidence of VAP were 0/11 vs 6/11, P < 0.01; the duration of ICU stay was (13 +/- 7) vs (26 +/- 14) days, P < 0.05, respectively. CONCLUSIONS: In COPD patients requiring intubation and MV for pulmonary infection and hypercapnic respiratory failure, early extubation followed by non-invasive MV initiated at the point of PIC window may significantly decrease the invasive and total durations of ventilatory support, the risk of VAP, and the duration of ICU stay.

Aged↗

PubMed2000

[Pressure influence on mRNA expression and protein synthesis of inducible nitric oxide synthetase in bovine trabecular meshwork cell].

OBJECTIVE: To investigate the inducible nitric oxide synthetase (iNOS) mRNA expression and protein synthesis in bovine trabecular meshwork cell and discuss the possible effects of nitric oxide (NO) in the development of glaucoma. METHODS: 20 mm Hg, 40 mm Hg, 60 mm Hg and 80 mm Hg pressure were respectively added on cultured trabecular cells of new born bovine. No pressure group was set as the control. The changes of iNOS mRNA and protein in trabecular meshwork cells under different pressures were demonstrated qualitatively and quantitatively by in situ hybridization and nicotinamide-adenine dinucleotide phosphate diaphorase (NADPH-d) histochemical assay. RESULTS: The expression of iNOS mRNA and its protein synthesis became higher and higher as the pressure was increased. There was weak iNOS mRNA expression in the control and 20 mm Hg groups, and no significant difference between them. 40 mm Hg and 60 mm Hg groups had a statistical difference from the control group. And 80 mm Hg group had a very significant difference from the control group. There was no difference between 40 mm Hg and 60 mm Hg groups, but they had significant difference from 80 mm Hg group. NADPH-d histochemical assay showed almost the same results except that there was significant difference between 40 mm Hg and 60 mm Hg groups. CONCLUSIONS: Pressure can evoke the expression of iNOS mRNA, and the nitric oxide thus produced can be one of the causes of trabecular meshwork destruction, that may induce or aggravate glaucoma.

Animals↗

PubMed2000

[Protection of hematopoietic stem cells by MIP-1alpha and PF4 against the cytotoxicity of chemotherapeutic agents].

OBJECTIVE: To study the protective effects of macrophage inflammatory protein-1alpha (MIP-1alpha) and platelet factor 4 (PF4), alone and in combination, on hematopoietic stem/progenitor cells against the cytotoxicity of chemotherapeutic drugs. METHODS: Bone marrow and cord blood mononuclear cells (BMMNC and CBMNC) and HL-60 cells were pretreated with MIP-1alpha, PF4, MIP-1alpha + PF4, and PBS respectively for 48 hours, and then incubated with DNR for an additional 24 hours. Cell viability, cell cycle, CD(34)(+) CD(38)(-) cells, colony forming units (CFU) and protein expression of p16, p27 gene were measured. RESULTS: (1) Cell viability, the number of CD(34)(+) CD(38)(-) cells and CFU yields of BMMNC and CBMNC in MIP-1alpha and PF4 groups were significantly higher than that in control groups (P < 0.05). (2) Cells in S + G(2) phase in MIP-1alpha and PF4 groups were significantly fewer than that in control groups (P < 0.05). (3) MIP-1alpha upregulated the expression of p16 gene of stem/progenitor cells. PF4 showed no effects on expression of both p16 and p27 genes. (4) Hematopoietic protection of MIP-1alpha was stronger than that of PF4. No cooperative effect could be seen in combination of the two agents. (5) Cell viability, cell cycle and expression of p16 and p27 gene of HL-60 cells were not affected by either MIP-1alpha or PF4. CONCLUSION: MIP-1alpha and PF4 can reversibly and selectively protect hematopoietic stem/progenitor cells against cytotoxicity of chemotherapeutic agents. MIP-1alpha can suppress cell proliferation by upregulating the expression of p16 gene and block the cell cycle at G(0) phase, resulting in the elevation of cell resistance to chemotherapeutic drugs.

ADP-ribosyl Cyclase↗

PubMed2000

[In situ FTIRS studies of reduction of [OsVI(N)(NH3)4](CF3SO3)3 in acetonitrile].

In this paper, the electrochemical cyclic voltammetry, UV/Vis and in situ FTIR spectroscopy were used to study the electrochemical reduction of [OsVI(N)(NH3)4](CF3SO3)3 on GC and Pt electrode in acetonitrile. The results demonstrated that the N-N coupling can occur between [OsVI(N)(NH3)4]3+ and the osmium(V) species generated at the electrode. It has revealed for the first time, by in situ FTIR spectroscopy, that the IR absorption of the nu (N identical to N) mode of the mu-dinitrogen osmium[III, II] and [II, II] complex yields positive-going band at around 2,019 cm-1 and negative-going band near 1,970 cm-1, respectively. The results provided new insights in understanding the mechanism of the coupling reaction [OsV identical to N][OsVI identical to N]<=>[OsII-N identical to N-OsIII].

English Abstract↗

PubMed2000

[Spectrometric determination of nutritional elements in the medicine-food flowers].

A study was carried out on the contents of nutritional elements in some medicine-food flowers by atomic absorption spectrometry. The results showed that flowers contain much more contents Fe, Ca, Mg and Co. The range of the average recovery in this method is 94%-108%, which indicate that the method we used is practicable. And flower is a kind of typical food source of containing high content of K and low content of Na. It is worth much more comprehensive utilization.

Asteraceae↗

PubMed1999

Free radical scavenging and antioxidant activities of flavonoids extracted from the radix of Scutellaria baicalensis Georgi.

Free radical scavenging and antioxidant activities of baicalein, baicalin, wogonin and wogonoside, the four major flavonoids in the radix of Scutellaria baicalensis Georgi, were examined in different systems. ESR results showed that baicalein and baicalin scavenged hydroxyl radical, DPPH radical and alkyl radical in a dose-dependent manner, while wogonin and wogonoside showed subtle or no effect on these radicals. Ten micromol/l of baicalein and baicalin effectively inhibited lipid peroxidation of rat brain cortex mitochondria induced by Fe(2+)-ascorbic acid, AAPH or NADPH, while wogonin and wogonoside showed significant effects only on NADPH-induced lipid peroxidation. In a study on cultured human neuroblastoma SH-SY5Y cells system, it was found that 10 micromol/l of baicalein and baicalin significantly protected cells against H(2)O(2)-induced injury. Baicalein was the most effective antioxidant among the four tested compounds in every system due to its o-tri-hydroxyl structure in the A ring. Compared with a well-known flavonoid, quercetin, the antioxidant activity of baicalein was lower in DPPH or AAPH system, but a little higher in those systems which might associate with iron ion. These results suggest that flavonoids in the radix of Scutellaria baicalensis with o-di-hydroxyl group in A the ring, such as baicalein and baicalin, could be good free radical scavengers and might be used to cure head injury associated with free radical assault.

Animals↗

PubMed1999

Insight into the mechanism of phosphoenolpyruvate mutase catalysis derived from site-directed mutagenesis studies of active site residues.

PEP mutase catalyzes the conversion of phosphoenolpyruvate (PEP) to phosphonopyruvate in biosynthetic pathways leading to phosphonate secondary metabolites. A recent X-ray structure [Huang, K., Li, Z., Jia, Y., Dunaway-Mariano, D., and Herzberg, O. (1999) Structure (in press)] of the Mytilus edulis enzyme complexed with the Mg(II) cofactor and oxalate inhibitor reveals an alpha/beta-barrel backbone-fold housing an active site in which Mg(II) is bound by the two carboxylate groups of the oxalate ligand and the side chain of D85 and, via bridging water molecules, by the side chains of D58, D85, D87, and E114. The oxalate ligand, in turn, interacts with the side chains of R159, W44, and S46 and the backbone amide NHs of G47 and L48. Modeling studies identified two feasible PEP binding modes: model A in which PEP replaces oxalate with its carboxylate group interacting with R159 and its phosphoryl group positioned close to D58 and Mg(II) shifting slightly from its original position in the crystal structure, and model B in which PEP replaces oxalate with its phosphoryl group interacting with R159 and Mg(II) retaining its original position. Site-directed mutagenesis studies of the key mutase active site residues (R159, D58, D85, D87, and E114) were carried out in order to evaluate the catalytic roles predicted by the two models. The observed retention of low catalytic activity in the mutants R159A, D85A, D87A, and E114A, coupled with the absence of detectable catalytic activity in D58A, was interpreted as evidence for model A in which D58 functions in nucleophilic catalysis (phosphoryl transfer), R159 functions in PEP carboxylate group binding, and the carboxylates of D85, D87 and E114 function in Mg(II) binding. These results also provide evidence against model B in which R159 serves to mediate the phosphoryl transfer. A catalytic motif, which could serve both the phosphoryl transfer and the C-C cleavage enzymes of the PEP mutase superfamily, is proposed.

Amino Acid Motifs↗

PubMed1999

The Wilms tumor suppressor WT1 encodes a transcriptional activator of amphiregulin.

WT1 encodes a zinc finger transcription factor implicated in kidney differentiation and tumorigenesis. In reporter assays, WT1 represses transcription from GC- and TC-rich promoters, but its physiological targets remain uncertain. We used hybridization to high-density oligonucleotide arrays to search for native genes whose expression is altered following inducible expression of WT1. The major target of WT1 was amphiregulin, a member of the epidermal growth factor family. The WT1(-KTS) isoform binds directly to the amphiregulin promoter, resulting in potent transcriptional activation. The in vivo expression profile of amphiregulin during fetal kidney development mirrors the highly specific pattern of WT1 itself, and recombinant Amphiregulin stimulates epithelial branching in organ cultures of embryonic mouse kidney. These observations suggest a model for WT1 as a transcriptional regulator during kidney differentiation.

Amphiregulin↗

PubMed1999

Backbone dynamics of the N-terminal domain in E. coli DnaJ determined by 15N- and 13CO-relaxation measurements.

The backbone dynamics of the N-terminal domain of the chaperone protein Escherichia coli DnaJ have been investigated using steady-state 1H-15N NOEs, 15N T1, T2, and T1 rho relaxation times, steady-state 13C alpha-13CO NOEs, and 13CO T1 relaxation times. Two recombinant constructs of the N-terminal domain of DnaJ have been studied. One, DnaJ(1-78), contains the most conserved "J-domain" of DnaJ, and the other, DnaJ(1-104), includes a glycine/phenylalanine rich region ("G/F" region) in addition to the "J-domain". DnaJ(1-78) is not capable of stimulating ATP hydrolysis by DnaK, despite the fact that all currently identified sites responsible for DnaJ-DnaK interaction are located in this region. DnaJ(1-104), on the other hand, retains nearly the full ATPase stimulatory activity of full length DnaJ. Recently, a structural analysis of these two molecules was presented in an effort to elucidate the origin of their functional differences [Huang, K., Flanagan, J. M., and Prestegard, J. H. (1999) Protein Science 8, 203-214]. Herein, an analysis of dynamic properties is presented in a similar effort. A generalized model-free approach with a full treatment of the anisotropic overall rotation of the proteins is used in the analysis of measured relaxation parameters. Our results show that internal motions on pico- to nanosecond time scales in the backbone of DnaJ(1-78) are reduced on the inclusion of the "G/F" region, while conformational exchange on micro- to millisecond time scales increases. We speculate that the enhanced flexibility of residues on the slow time scale upon the inclusion of the "G/F" region could be relevant to the ATPase stimulatory activity of DnaJ if an "induced-fit" mechanism applies to DnaJ-DnaK interactions.

Anisotropy↗