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Biomedical subjects

C Huang

Publications and source records attributed to C Huang.

At least 145 records · Page 8Linked to original sources
PubMed2000

Vanadate induces p53 transactivation through hydrogen peroxide and causes apoptosis.

Vanadium is a metal widely distributed in the environment. Although vanadate-containing compounds exert potent toxic effects on a wide variety of biological systems, the mechanisms controlling vanadate-induced adverse effects remain to be elucidated. The present study investigated the vanadate-induced p53 activation and involvement of reactive oxygen species (ROS) in p53 activation as well as the role of p53 in apoptosis induction by vanadate. Exposure of mouse epidermal JB6 cells to vanadate led to transactivation of p53 activity in a time- and dose-dependent manner. It also caused mitochondrial damage, apoptosis, and generated ROS. Scavenging of vanadate-induced H(2)O(2) by N-acetyl-l-cysteine (a general antioxidant) or catalase (a specific H(2)O(2) inhibitor), or the chelation of vanadate by deferoxamine, resulted in inhibition of p53 activation and cell mitochondrial damage. In contract, an increase in H(2)O(2) generation in response to superoxide dismutase or NADPH enhanced these effects caused by vanadate. Furthermore, vanadate-induced apoptosis occurred in cells expressing wild-type p53 (p53+/+) but was very weak in p53-deficient (p53-/-) cells. These results demonstrate that vanadate induces p53 activation mainly through H(2)O(2) generation, and this activation is required for vanadate-induced apoptosis.

Acetylcysteine↗
PubMed2000

The top of the inserted-like domain of the integrin lymphocyte function-associated antigen-1 beta subunit contacts the alpha subunit beta -propeller domain near beta-sheet 3.

We find that monoclonal antibody YTA-1 recognizes an epitope formed by a combination of the integrin alpha(L) and beta(2) subunits of LFA-1. Using human/mouse chimeras of the alpha(L) and beta(2) subunits, we determined that YTA-1 binds to the predicted inserted (I)-like domain of the beta(2) subunit and the predicted beta-propeller domain of the alpha(L) subunit. Substitution into mouse LFA-1 of human residues Ser(302) and Arg(303) of the beta(2) subunit and Pro(78), Thr(79), Asp(80), Ile(365), and Asn(367) of the alpha(L) subunit is sufficient to completely reconstitute YTA-1 reactivity. Antibodies that bind to epitopes that are nearby in models of the I-like and beta-propeller domains compete with YTA-1 monoclonal antibody for binding. The predicted beta-propeller domain of integrin alpha subunits contains seven beta-sheets arranged like blades of a propeller around a pseudosymmetry axis. The antigenic residues cluster on the bottom of this domain in the 1-2 loop of blade 2, and on the side of the domain in beta-strand 4 of blade 3. The I domain is inserted between these blades on the top of the beta-propeller domain. The antigenic residues in the beta subunit localize to the top of the I-like domain near the putative Mg(2+) ion binding site. Thus, the I-like domain contacts the bottom or side of the beta-propeller domain near beta-sheets 2 and 3. YTA-1 preferentially reacts with activated LFA-1 and is a function-blocking antibody, suggesting that conformational movements occur near the interface it defines between the LFA-1 alpha and beta subunits.

Amino Acid Sequence↗
PubMed2000

Structural and functional studies with antibodies to the integrin beta 2 subunit. A model for the I-like domain.

To establish a structure and function map of the beta2 integrin subunit, we mapped the epitopes of a panel of beta2 monoclonal antibodies including function-blocking, nonblocking, and activating antibodies using human/mouse beta2 subunit chimeras. Activating antibodies recognize the C-terminal half of the cysteine-rich region, residues 522-612. Antibodies that do not affect ligand binding map to residues 1-98 and residues 344-521. Monoclonal antibodies to epitopes within a predicted I-like domain (residues 104-341) strongly inhibit LFA-1-dependent adhesion. These function-blocking monoclonal antibodies were mapped to specific residues with human --> mouse knock-out or mouse --> human knock-in mutations. Combinatorial epitopes involving residues distant in the sequence provide support for a specific alignment between the beta-subunit and I domains that was used to construct a three-dimensional model. Antigenic residues 133, 332, and 339 are on the first and last predicted alpha-helices of the I-like domain, which are adjacent on its "front." Other antigenic residues in beta2 and in other integrin beta subunits are present on the front. No antigenic residues are present on the "back" of the domain, which is predicted to be in an interface with other domains, such as the alpha subunit beta-propeller domain. Most mutations in the beta2 subunit in leukocyte adhesion deficiency are predicted to be buried in the beta2 subunit I-like domain. Two long insertions are present relative to alpha-subunit I-domains. One is tied down to the back of the I-like domain by a disulfide bond. The other corresponds to the "specificity-determining loop" defined in beta1 and beta3 integrins and contains the antigenic residue Glu(175) in a disulfide-bonded loop located near the "top" of the domain.

Amino Acid Sequence↗
PubMed2000

Regulated expression of the rat recombinant P2X(3) receptor in stably transfected CHO-K1 tTA cells.

In this report, the regulatable expression by tetracycline of the rat recombinant P2X(3) receptor in stably transfected Chinese hamster ovary (CHO-K1) expressing the tetracycline-controlled transactivator (tTA) is described. cDNA encoding the rat P2X(3)-receptor was subcloned into pTRE (a tetracycline-repressible expression vector) which was used to transfect stably CHO-K1 tTA cells. Using whole cell patch clamp techniques, 100 microM ATP evoked inward currents of 2.9+/-1.6 nA in transfected cells grown in the absence of tetracycline (tet-). The P2X(3) receptor protein was detectable by immunoblot as early as 24 h and protein expression levels continued to increase as much as 192 h following activation of tTA by the removal of the antibiotic. Saturation binding isotherms using [35S]ATP gamma S yielded a pK(d) of 8.2+/-0.1 and a B(max) of 31.9+/-3.5 pmol/mg protein in tet- cell membranes and a pK(d) of 8.1+/-0.1 and a B(max) of 5.8+/-0.8 pmol/mg protein in tet+ cell membranes. The agonist ligands 2MeSATP and alpha beta MeATP displaced the binding of [35S]ATP gamma S in tet- cell membranes with very high affinity, yielding pIC(50) values of 9.4+/-0.2 and 7.5+/-0. 2, respectively. In tet+ cell membrane, displacement of [35S]ATP gamma S by 2MeSATP and alpha beta MeATP was of much lower affinity (pIC(50) values of 7.8 and 6.2, respectively). ATP, ADP and UTP showed similar displacement of [35S]ATP gamma S binding in tet- and tet+ cell membranes. In other experiments, cytosolic Ca(2+) was monitored using the fluorescent indicator, fluo-3. Increases in cytosolic Ca(2+) were elicited by 100 nM alpha beta MeATP in tet- cells while no increases in cytosolic Ca(2+) were detected below 100 microM alpha beta MeATP in either tet+ cells or untransfected cells. These calcium responses to alpha beta MeATP had a pEC(50) of 6.7 and were transient, returning to baseline within 120 s. Suramin produced concentration-dependent, parallel, dextral shifts of E/[A] curves to alpha beta MeATP yielding a pK(B) of 5.6. PPADS produced non-parallel, dextral shifts of E/[A] curves to alpha beta MeATP which were insurmountable. These results show for the first time, expression of a functional, homomeric recombinant rat P2X(3) receptor which is under regulated expression in a stably transfected mammalian cell line.

Animals↗
PubMed2000

Repeated administration of low dose ketamine for the treatment of monoarthritic pain in the rat.

The aim of the present study was to observe the effect of repeated subcutaneous (sc) injections of low doses of ketamine for the treatment of acute inflammatory pain in a complete Freund's adjuvant-induced monoarthritic pain model in rats. The results show: (1) sc injection of ketamine at a dose of 2 mg x kg(-1) or 10 mg x kg(-1) produced significant analgesia (P<0.01) in arthritic rats starting from the 2nd week and 3rd week, respectively. (2) Repeated administration of ketamine produced a significant reduction of the circumference of the arthritic ankle (P<0.05 and P<0.01 with different doses). (3) The body weight of the rats was not affected by continuous administration of ketamine for 4 weeks. No abnormal locomotor behavior was observed (It was concerned but not systemically evaluated in this study). The results suggest that repeated sc injection of ketamine for 4 weeks significantly reduce inflammatory pain in monoarthritis without notable aversive side effects.

Analgesics↗
PubMed2000

Competitive Adsorption of Ferricyanide and Ferrocyanide on gamma-Al(2)O(3) Surface.

In the past 3 decades, research has proven the significance of competitive adsorption in the equilibrium of pollutants between solid and liquid phases. However, studies on the competitive adsorption of complex ions are very limited in spite of its important role in transporting pollutants in the natural environment. The objective of this study is to derive the thermodynamic parameters of the competitive adsorption between ferricyanide and ferrocyanide from the modified Langmuir isotherm and the triple-layer model (TLM) to determine the location of adsorption. The effects of pH, temperature, and ion concentration on competitive adsorption onto gamma-Al(2)O(3) were investigated. The results demonstrate that ferrocyanide is more competitive than ferricyanide. By comparing the derived K(app) with K(int), we inferred that the adsorption of ferricyanide and ferrocyanide onto gamma-Al(2)O(3) was achieved through outer-sphere complexation. The negative DeltaH degrees indicated that the adsorption was exothermic. The positive entropy (Delta S degrees ) was caused by the replacement and release of a greater number of smaller surface ions by adsorbed ferricyanide and ferrocyanide ions of larger size. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Involvement of nuclear factor of activated T cells activation in UV response. Evidence from cell culture and transgenic mice.

Mammalian cells respond to UV radiation by signaling cascades leading to activation of transcription factors, such as activated protein 1, NFkappaB, and p53, a process known as the "UV response." Nuclear factor of activated T cells (NFAT) was first identified as an inducible nuclear factor in immune response and subsequently found to be expressed in other tissues and cells. To date, however, the regulation and function of NFAT in tissues and cells, other than the immune system, are not well understood. In this study, we demonstrate that UV radiation activates NFAT-dependent transcription through a calcium-dependent mechanism in mouse epidermal JB6 cell lines, as well as in the skin of NFAT-luciferase reporter transgenic mice. Exposure of JB6 cells to UV radiation leads to the transactivation of NFAT in a dose-dependent manner. A23187 had a synergistic effect with UV for NFAT induction, whereas pretreatment of cells with nifedipine, a calcium channel blocker, dramatically impaired the NFAT activity induced by either UV or UV plus A23187. Calcium-dependent activation of NFAT by UV was further confirmed by an in vivo study using NFAT-luciferase reporter transgenic mice. These results demonstrated that UV radiation is a strong activator for skin NFAT transactivation through calcium-dependent pathways, suggesting that NFAT activation may be a part of the UV response.

Animals↗
PubMed2000

Mechanistic studies of rat protein farnesyltransferase indicate an associative transition state.

Protein farnesyltransferase is a zinc metalloenzyme that catalyzes the transfer of a 15-carbon farnesyl group to a conserved cysteine residue of a protein substrate. Both electrophilic and nucleophilic mechanisms have been proposed for this enzyme. In this work, we investigate the detailed catalytic mechanism of mammalian protein farnesyltransferase by measuring the effect of metal substitution and/or substrate alterations on the rate constant of the chemical step. Substitution of cadmium for the active site zinc enhances peptide affinity approximately 5-fold and decreases the rate constant for the formation of the thioether product approximately 6-fold, indicating changes in the metal-thiolate coordination in the catalytic transition state. In addition, the observed rate constant for product formation decreases for C3 fluoromethyl farnesyl pyrophosphate substrates, paralleling the number of fluorines at the C3 methyl position and indicating that a rate-contributing transition state has carbocation character. Magnesium ions do not affect the affinity of either the peptide or the isoprenoid substrate but specifically enhance the observed rate constant for product formation 700-fold, suggesting that magnesium coordinates and activates the diphosphate leaving group. These data suggest that FTase catalyzes protein farnesylation by an associative mechanism with an "exploded" transition state where the metal-bound peptide/protein sulfur has a partial negative charge, the C1 of FPP has a partial positive charge, and the bridge oxygen between C1 and the alpha phosphate of FPP has a partial negative charge. This proposed transition state suggests that stabilization of the developing charge on the carbocation and pyrophosphate oxygens is an important catalytic feature.

Alkyl and Aryl Transferases↗
PubMed2000

Charged tmRNA but not tmRNA-mediated proteolysis is essential for Neisseria gonorrhoeae viability.

tmRNA, through its tRNA and mRNA properties, adds short peptide tags to abnormal proteins, targeting these proteins for proteolytic degradation. Although the conservation of tmRNA throughout the bacterial kingdom suggests that it must provide a strong selective advantage, it has not been shown to be essential for any bacterium. We report that tmRNA is essential in Neisseria gonorrhoeae. Although tagging per se appears to be required for gonococcal viability, tagging for proteolysis does not. This suggests that the essential roles of tmRNA in N.gonorrhoeae may include resolving stalled translation complexes and/or preventing depletion of free ribosomes. Although derivatives of N.gonorrhoeae expressing Escherichia coli tmRNA as their sole tmRNA were isolated, they appear to form colonies only after acquiring an extragenic suppressor(s).

Base Sequence↗
PubMed2000

Formation of enzymatically active, homotypic, and heterotypic tetramers of mouse mast cell tryptases. Dependence on a conserved Trp-rich domain on the surface.

Mouse mast cell protease (mMCP) 6 and mMCP-7 are homologous tryptases stored in granules as macromolecular complexes with heparin and/or chondroitin sulfate E containing serglycin proteoglycans. When pro-mMCP-7 and pseudozymogen forms of this tryptase and mMCP-6 were separately expressed in insect cells, all three recombinant proteins were secreted into the conditioned medium as properly folded, enzymatically inactive 33-kDa monomers. However, when their propeptides were removed, mMCP-6 and mMCP-7 became enzymatically active and spontaneously assumed an approximately 150-kDa tetramer structure. Heparin was not required for this structural change. When incubated at 37 degrees C, recombinant mMCP-7 progressively lost its enzymatic activity in a time-dependent manner. Its N-linked glycans helped regulate the thermal stability of mMCP-7. However, the ability of this tryptase to form the enzymatically active tetramer was more dependent on a highly conserved Trp-rich domain on its surface. Although recombinant mMCP-6 and mMCP-7 preferred to form homotypic tetramers, these tryptases readily formed heterotypic tetramers in vitro. This latter finding indicates that the tetramer structural unit is a novel way the mast cell uses to assemble varied combinations of tryptases.

Animals↗
PubMed2000

Hip fracture incidence among Caucasians in Hawaii is similar to Japanese. A population-based study.

Age-specific hip fracture incidence has been increasing in some parts of the world. The incidence of hip fractures among Japanese on the island of Oahu, Hawaii in 1979-1981 was approximately half that of Caucasians in North America, but similar to the incidence in Japan. We surveyed the incidence on Oahu again in 1991-1995 for all races to compare the incidence among Japanese to the earlier rates, and to other populations, including Caucasians on Oahu. The incidence of hip fracture among Japanese in Hawaii between 1991-1995 had not changed appreciably (compared to 1979-1981), and was similar to that among Caucasians on Oahu. The incidence among Hawaii Japanese and Caucasians was similar to, or lower than Japan overall, and much lower (one-third to one-half) than that reported for Caucasians in North America and Northern Europe, suggesting that the prevalence of certain risk factors may be lower in Hawaii. These findings confirm other studies suggesting that nongenetic factors may be responsible for much of the observed differences in hip fracture incidence between countries, and between races.

Age Distribution↗
PubMed2000

Biotreatment of H2S- and NH3-containing waste gases by co-immobilized cells biofilter.

Gas mixture of H2S and NH3 in this study has been the focus in the research area concerning gases generated from the animal husbandry and the anaerobic wastewater lagoons used for their treatment. A specific microflora (mixture of Thiobacillus thioparus CH11 for H2S and Nitrosomonas europaea for NH3) was immobilized with Ca-alginate and packed inside a glass column to decompose H2S and NH3. The biofilter packed with co-immobilized cells was continuously supplied with H2S and NH3 gas mixtures of various ratios, and the removal efficiency, removal kinetics, and pressure drop in the biofilter was monitored. The results showed that the efficiency remained above 95% regardless of the ratios of H2S and NH3 used. The NH3 concentration has little effect on H2S removal efficiency, however, both high NH3 and H2S concentrations significantly suppress the NH3 removal. Through product analysis, we found that controlling the inlet ratio of the H2S/NH3 could prevent the biofilter from acidification, and, therefore, enhance the operational stability. Conclusions from bioaerosol analysis and pressure drop in the biofilter suggest that the immobilized cell technique creates less environmental impact and improves pure culture operational stability. The criteria for the biofilter operation to meet the current H2S and NH3 emission standards were also established. To reach Taiwan's current ambient air standards of H2S and NH3 (0.1 and 1 ppm, respectively), the maximum inlet concentrations should not exceed 58 ppm for H2S and 164 ppm for NH3, and the residence time be kept at 72 s.

Air Pollutants↗
PubMed2000

Discrimination of Alzheimer's disease and mild cognitive impairment by equivalent EEG sources: a cross-sectional and longitudinal study.

OBJECTIVES: The spatial aspects of brain electrical activity can be assessed by equivalent EEG frequency band generators. We aimed to describe alterations of these EEG generators in Alzheimer's disease (AD) and healthy aging and whether they could serve as predictive markers of AD in subjects at risk. METHODS: The amplitude and 3-dimensional localization of equivalent EEG sources were evaluated using FFT dipole approximation in 38 mild AD patients, 31 subjects with mild cognitive impairment (MCI) and 24 healthy control subjects. RESULTS: AD patients showed an increase of delta and theta global field power (GFP), which corresponds to the generalized EEG amplitude, as well as a reduction of alpha GFP when compared to the controls. A decrease of alpha and beta GFP was found in AD patients, as compared to the MCI subjects. With respect to topography in the antero-posterior direction, sources of alpha and beta activity shifted more anteriorly in AD patients compared to both the controls and MCI subjects. No significant difference was found between MCI and controls. Combined alpha and theta GFP were the best discriminating variables between AD patients and controls (84% correct classification) and AD and MCI subjects (78% correctly classified). MCI subjects were followed longitudinally (25 months on average) in order to compare differences in baseline EEG variables between MCI subjects who progressed to AD (PMCI) and those who remained stable (SMCI). Compared to SMCI, PMCI had decreased alpha GFP and a more anterior localization of sources of theta, alpha and beta frequency. In a linear discriminant analysis applied on baseline values of the two MCI subgroups, the best predictor of future development of AD was found to be antero-posterior localization of alpha frequency. CONCLUSIONS: FFT dipole approximation and frequency analysis performed by conventional FFT showed comparable classification accuracy between the studied groups. We conclude that localization and amplitude of equivalent EEG sources could be promising markers of early AD.

Aged↗
PubMed2000

Hydrogen peroxide-induced apoptosis in human hepatoma cells is mediated by CD95(APO-1/Fas) receptor/ligand system and may involve activation of wild-type p53.

Reactive oxygen species (ROS) play an important role in cell death induced by many different stimuli. Direct exposure of human hepatoma cell line SMMC-7221 to hydrogen peroxide (H2O2) can induce apoptosis characterized by morphological evidence and fragmentation of DNA assayed by terminal deoxynucleotidyl transferase assay (TUNEL assay). Analysis of flow cytometry indicated that H2O2 can decrease the level of CD95(APO-1/Fas), and it is confirmed that H2O2 can also activate the differential expression of some specific gene such as p53 by means of RT-PCR technique. The results indicated that CD95 signal transduction system may be involved in the H2O2-induced apoptosis, and can regulate some specific genes associated with apoptosis in transcription and translation levels such as p53.

Apoptosis↗
PubMed2000

Body mass index during childhood, adolescence and young adulthood in relation to adult overweight and adiposity: the Fels Longitudinal Study.

BACKGROUND: Childhood overweight develops during 'critical periods', but the relationship of body mass index (BMI) patterns during 'critical periods' from childhood into adulthood with subsequent overweight and adiposity has not been previously investigated. BMI patterns during early childhood, pubescence and post-pubescence and their independent effects on overweight and body fatness at 35-45 y of age were examined along with birth weight and the effects of adult lifestyle factors. METHODS: BMI parameters describing the timing, velocity minimum (min) and maximum (max) values from 2 to 25 y of age were related to adulthood BMI values and total and percentage body fat (TBF, %BF) at 35-45 y. These data were from 180 males and 158 females in the Fels Longitudinal Study. RESULTS: There was no sex difference in the timing of BMI rebound, but the age of BMI maximum velocity and maximum BMI were both earlier in girls. Children with an earlier BMI rebound had larger BMI values at rebound and at maximum velocity. Children who reached maximum BMI at later age had larger maximum BMI values. Maximum BMI was a strong predictor for adult BMI and in females, a strong predictor of adulthood TBF and %BF. Maximum BMI was closely related to maximum BMI velocity in females and in males, BMI at maximum velocity is a strong predictor of TBF and %BF. CONCLUSIONS: Changes in childhood BMI were related to adult overweight and adiposity more so in females than males. BMI rebound is a significant important period related to overweight at 35-45 y in females but not in males. However BMI patterns during and post-adolescence were more important than the BMI rebound for adulthood TBF and %BF status. There is marked tracking in BMI from approximately 20 y into 35-45 y. The pattern of BMI changes from 2 to 25 y had stronger effects on subsequent adult overweight than birth weight and adult lifestyle variables.

Adipose Tissue↗
PubMed2000

Preserving transfer independence among individuals with spinal cord injury.

STUDY DESIGN: Literature review. OBJECTIVES: Upper extremity (UE) joint degeneration, particularly at the shoulder, detrimentally influences functional independence, quality of life, cardiovascular disease risk, and life expectancy of individuals following spinal cord injury (SCI). This review (1) describes UE use for transfers among individuals with SCI; (2) describes contributing factors associated with UE joint degeneration and loss of transfer independence; (3) summarizes and identifies gaps in existing research; and (4) provides suggestions for future research. RESULTS: Investigations of wheelchair transfer related UE joint and function preservation among individuals with SCI should consider factors including age and length of time from SCI onset, interface between subject-wheelchair, pain, shoulder joint range of motion (ROM) and muscle strength deficiencies or imbalances, exercise capacity and tolerance for the physical strain of activities of daily living (ADL), body mass and composition, previous UE injury or disease history, and transfer techniques. Existing studies of transfers among individuals with SCI have relied on small groups of either asymptomatic or non-impaired subjects, with minimal integration of kinematic, kinetic and electromyographic data. Descriptions of UE joint ROM, forces, and moments produced during transfers are lacking. CONCLUSIONS: Biomechanical measurement and computer modeling have provided increasingly accurate tools for acquiring the data needed to guide intervention planning to prevent UE joint degeneration and preserve function among individuals with SCI. The identification of stressful sub-components during transfers will enable intervening clinicians and engineers who design and modify assistive and adaptive devices to better serve individuals with SCI.

Activities of Daily Living↗
PubMed2000

Phakomatosis pigmentovascularis IIb with renal anomaly.

Phakomatosis pigmentovascularis (PPV) is a rare congenital naevoid syndrome; most case reports originate in Japan. The major clinical manifestations consist of coexisting extensive naevus flammeus and pigmentary naevus with or without systemic involvement. We report an 8-year-old Taiwanese boy, who was born with extensive naevus flammeus and other anomalies comprising persistent aberrant Mongolian spot-like pigmentary patches, leg-length discrepancy, pelvic obliquity, scoliosis and bilateral melanosis oculi bulbi. Further investigation also revealed agenesis of the right kidney. The cutaneous lesions remained unchanged over a 3-year follow-up period. Within the classification of PPV, this boy's disorder represents an example of PPV IIb. Right kidney agenesis, which has never been observed in PPV, may be an incidental finding.

Child↗