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Biomedical subjects

K Huang

Publications and source records attributed to K Huang.

At least 127 records · Page 7Linked to original sources
PubMed1996

Differential radioprotection of three mouse strains by basic or acidic fibroblast growth factor.

Recently we found that human recombinant basic fibroblast growth factor (FGF2) radioprotected C3H/HeNCr mice after whole body irradiation (WBI). The purpose of the present study was to compare the in vivo radioprotective effects of human recombinant acidic fibroblast growth factor (FGF1) or FGF2 in three strains of mice (C3H/HeNCr, BALB/CAn, C57BL/6). In vivo administration of 6 micrograms/mouse of FGF1 or FGF2 pre- or post- WBI significantly protected only C3H and BALB/C mice. Dose modification factor was: C3H(FGF1/2) 1.09 +/- 0.02/1.14 +/- 0.04; BALB/C(FGF1/2) 1.13 +/- 0.02/1.15 +/- 0.01. Response was minimal or absent in C57 mice (FGF2 1.02 +/- 0.02). Increasing the FGF dose above 12 micrograms/mouse did not increase radioprotection in any strain. In single radiation dose studies, FGF2 was more potent than FGF1 in C3H mice; FGF1 and FGF2 were equipotent in BALB/C mice; and both had minimal effect in C57 mice. Significant radioprotection occurred in only two of the three strains of mice studied. We therefore suggest caution in applying mouse radioprotection data to other species.

Animals↗
PubMed1996

Diversity of the Tcra-V3 gene family in BALB/c mice.

Southern analysis of Eco RI-digested BALB/c liver DNA reveals four T-cell receptor Tcra-V3-hybridizing DNA fragments, which are of sizes 18.0, 12.0, 8.0, and 2.1 kilobases, respectively. These four Tcra-V3-hybridizing genomic DNA were isolated from a BALB/c genomic library. Restriction and Southern analysis of the genomic DNA clones showed that each of the Tcra-V3-hybridizing Eco RI DNA fragments harbors only a single Tcra-V3 gene. The DNA sequences of coding regions of the four Tcra-V3 family members were determined. These sequences show very limited divergence from one another. Comparisons of BALB/c Tcra-V3 sequences with published Tcra-V3 sequences expressed in different strains of mice reveal substantial allelic polymorphism. Sequence similarity searches retrieved homologous rat, cattle, and human genes. The scarcity of coding sequence divergence among members of the Tcra-V3 family and the more substantial allelic polymorphism may be general features of the T-cell receptor V-alpha chain-encoding gene families.

Amino Acid Sequence↗
PubMed1996

The collectivistic nature of ethnic identity development among Asian-American college students.

Current theories of ethnic identity oversimplify the development process by failing to recognize the malleability of identity within its social context, a conceptualization of self that is particularly relevant for Asian-Americans. Further, these theories tend to view identity in static, deterministic terms, despite social psychology data suggesting that identity is a dynamic ongoing process. Data were analyzed from a sample of 87 Asian-American undergraduates, using the Ethnic Identity Development Exercise (EIDE). While many theories suggest that ethnic identity development is predominantly an internal, intro-psychic process, our data indicate that Asian-Americans are largely influenced by relationships and external forces. In addition, the avoidance of shame was found to be a strong motivating factor in determining their ethnic identification. Thus, ethnic identification theories must acknowledge the malleable and collectivistic nature of ethnic identity development among Asian-Americans. Three theoretical frameworks of research on ethnic identity are reviewed and summarized: identity formation, social identity, and acculturation.

Acculturation↗
PubMed1996

[Effect of phosphorylation by protein kinase C on the DNA binding activity of high mobility group protein I].

High mobility group protein I (HMG-I) is a nonhistone chromosomal protein. The present study aims to examine phosphorylation of HMG-I by protein kinase C (PKC) and its effect on HMG-I's DNA binding activity. HMG-I, extracted and purified from rat brain was phosphorylated in vitro equally well by PKC alpha, beta, gamma and delta. Phosphoamino acid analysis indicated that both serine and threonine residues were phosphorylated. The nonphosphorylated HMG-I was shown to bind specifically to the fragment of DNA containing bp -708 to -458 of RC3 genomic DNA, which is abundant in A-T sequences. In contrast, phosphorylation of HMG-I by PKC resulted in an attenuation of binding to the DNA fragment. It is suggested that phosphorylation of HMG-I by PKC may regulate DNA binding activity of HMG-I, thereby possibly altering its biological functions.

Animals↗
PubMed1996

[The effect of electro-acupuncture on the adrenal gland of endotoxic shocked rats].

The quantitative histochemical changes of glycogen SDH in the adrenal gland of endotoxic-shocked rat induced by electro-acupuncture were observed in this paper. The result indicates that electro-acupuncture at "Ren Zhong" or "Zusali" of endotoxic shocked animal might improve the function of adrenal cortex and achieve recovery in certain extent.

Adrenal Glands↗
PubMed1996

Cataract extraction by phacoemulsification in situ and elliptical intraocular lens implantation.

OBJECTIVE: To investigate the technique of phacoemulsification in situ for cataract extraction and elliptical intraocular lens (IOL) implantation. METHODS: 60 eyes of 57 cases with cataract were included and the hardness of nucleus was grade-1-2 in 25 eyes, grade-3 in 27 eyes and grade-4 in 8 eyes. Tunnel incision was made and in situ phacoemulsification with elliptical (5 mm x 6 mm) IOL implantation was performed on all the cases. RESULTS: Phaco-spent-time was 45 seconds to 3 minutes 45 seconds (average 1 minute 52 seconds). Phacoemulsification in 53 eyes (88.3%) was successful in situ Visual acuities of 0.5 or better and 1.0 or better at postoperative one week were obtained in 75.0% and 56.7%, and at 1-12 month follow-up in 85.0% and 71.7% respectively. CONCLUSION: The technique of phacoemulsification in situ and elliptical IOL implantation is worthy to be spread due to minimum postoperative astigmatism and fast restoration of visual acuity.

Adult↗
PubMed1995

Murine txk: a protein tyrosine kinase gene regulated by T cell activation.

To identify genes involved in signal transduction pathways that regulate T cell activation and development, murine fetal thymocytes were screened for expression of protein tyrosine kinase family members by the polymerase chain reaction. Using this approach, a non-receptor protein tyrosine kinase, txk, was identified and cloned. Tsk is expressed in thymocytes as early as fetal day 13.5 and its expression at the mRNA level continues throughout development. Txk transcripts are present in thymocytes, peripheral T cells and mast cell lines, but are not detectable in B cell macrophage/monocyte cell lines or in non-hematopoietic fetal or adult tissues. In both thymocytes and T cells, txk transcripts are down-regulated after activation with PMA and ionomycin, concanavalin A or T cell receptor cross-linking. Sequence analysis indicates that txk contains SH2, SH3 and kinase catalytic domains and belongs to the tec family of cytoplasmic protein tyrosine kinases which includes tec, itk and btk. Its unique N-terminus contains a proline-rich region, but unlike the other tec family members, does not contain a pleckstrin homology domain. The restricted expression pattern of txk and its regulation by T cell activation make it an excellent candidate for involvement in signal transduction during thymocyte development.

Amino Acid Sequence↗
PubMed1995

Water molecules participate in proteinase-inhibitor interactions: crystal structures of Leu18, Ala18, and Gly18 variants of turkey ovomucoid inhibitor third domain complexed with Streptomyces griseus proteinase B.

Crystal structures of the complexes of Streptomyces griseus proteinase B (SGPB) with three P1 variants of turkey ovomucoid inhibitor third domain (OMTKY3), Leu18, Ala18, and Gly18, have been determined and refined to high resolution. Comparisons among these structures and of each with native, uncomplexed SGPB reveal that each complex features a unique solvent structure in the S1 binding pocket. The number and relative positions of water molecules bound in the S1 binding pocket vary according to the size of the side chain of the P1 residue. Water molecules in the S1 binding pocket of SGPB are redistributed in response to the complex formation, probably to optimize hydrogen bonds between the enzyme and the inhibitor. There are extensive water-mediated hydrogen bonds in the interfaces of the complexes. In all complexes, Asn 36 of OMTKY3 participates in forming hydrogen bonds, via water molecules, with residues lining the S1 binding pocket of SGPB. For a homologous series of aliphatic straight side chains, Gly18, Ala18, Abu18, Ape18, and Ahp18 variants, the binding free energy is a linear function of the hydrophobic surface area buried in the interface of the corresponding complexes. The resulting constant of proportionality is 34.1 cal mol-1 A-2. These structures confirm that the binding of OMTKY3 to the preformed S1 pocket in SGPB involves no substantial structural disturbances that commonly occur in the site-directed mutagenesis studies of interior residues in other proteins, thus providing one of the most reliable assessments of the contribution of the hydrophobic effect to protein-complex stability.

Alanine↗
PubMed1995

Lipopolysaccharide-induced E-selectin expression requires continuous presence of LPS and is inhibited by bactericidal/permeability-increasing protein.

Endothelial cells stimulated by LPS express E-selectin, which plays an important role in mediating neutrophil adhesion during inflammation. E-selectin is induced within 1-2 h, peaks at 4-6 h, and gradually returns to basal level by 24 h. rBPI21, a recombinant N-terminal fragment of human bactericidal/permeability-increasing protein (BPI), inhibited LPS-induced E-selectin expression when added at the same time as, and up to 6 h after, LPS. Delayed administration of rBPI21 also affected LPS-mediated activation of the nuclear factor, NF-kappa B. Two to 4 h following LPS addition to endothelial cells, when NF-kappa B was already activated, addition of rBPI21 resulted in marked reduction of NF-kappa B detectable at 4 or 6 h. These results indicate that endothelial activation requires continuous presence of LPS, and rBPI21 acts to reverse LPS-mediated endothelial activation by interrupting the on-going LPS signal.

Antimicrobial Cationic Peptides↗
PubMed1995

Interference of electromagnetic waves in dynamic metabolism.

Life is a continuous process of the dynamic metabolism. The influence of electromagnetic waves on the process of metabolism cannot be neglected. Here a new theory of electromagnetic interference in the dynamic metabolism of life is proposed. The statistical dynamic equations of ion and free radical in the biochemical reaction radiated by electromagnetic waves are given. The intensity of electromagnetic interference could be described with an interference factor. Good agreement can be seen between the calculated and measured results for a famous experiment of radio-frequency radiation-induced calcium ion efflux enhancement.

Animals↗
PubMed1995

[Histochemical observation of the effect of electroacupuncture on the livers of rats with endotoxic shock].

The experimental rats were randomly divided into three groups: i.e. control group; endotoxic shock group (the model of endotoxic shock was induced by intravenous administration of E. Coli endotoxin, 16 mg/kg); and electroacupuncture (EA) group ("Renzhong" or "Zusanli" acupoint was stimulated for 15 minutes at 1 hr after injection of endotoxin). The experimental rats were decapitated at 75 minutes after injecting endotoxin. Their livers were taken out for cryostat section, and histochemical observation. The results were as follows: 1) The glycogen in the hepatic cells of endotoxic shocked rats were almost completely depleted. The activities of SDH Mg(++)-ATPase and G-6-Pase and 5'-Nase were decreased; especially the activities of 5'-Nase in the biliary canaliculi and sinusoids were apparently reduced. 2) The content of hepatic glycogen in EA group was increased, but some of them was still depleted. The activities of SDH, Mg(++)-ATPase and G-6-Pase were slightly increased as compared with that of the endotoxic shock group. The activity of 5'-Nase was obviously increased after EA. The preliminary results indicated that EA at "Renzhong" or "Zusanli" acupoint of rats with endotoxic shock might play certain role on improving the hepatic metabolism and promoting the membrane transport action.

Animals↗
PubMed1994

Active-site mutations of diphtheria toxin: role of tyrosine-65 in NAD binding and ADP-ribosylation.

Previous studies have suggested that tyrosine-65 (Tyr-65) of diphtheria toxin (DT) is located at the active site. To investigate the role of Tyr-65 in NAD binding and the ADP-ribosylation of elongation factor-2 (EF-2), we changed this residue to alanine and phenylalanine by site-directed mutagenesis of a synthetic gene encoding the catalytic fragment of DT (DTA). The alanine mutant was greatly diminished in ADP-ribosylation activity (350-fold) and NAD-glycohydrolase activity (88-fold), whereas the phenylalanine mutant was reduced in these activities only slightly. Dissociation constants (Kd) for NAD binding were 15 microM for wild-type DTA, 26 microM for the phenylalanine mutant, and greater than 800 microM NAD for the alanine mutant. However, both mutant enzymes were found to bind adenosine with nearly equal affinity as wild-type DTA. These results support a model of ADP-ribosylation in which the phenolic ring of Tyr-65 interacts with the nicotinamide ring of NAD, orienting the N-glycosidic bond of NAD for attack by the incoming nucleophile in a direct displacement mechanism.

Adenosine↗
PubMed1994

Role of TCR zeta chain in T cell development and selection.

Signals mediated by the T cell receptor (TCR) are required for thymocyte maturation and selection. To examine the role of TCR zeta chain signals in development, TCR expression was restored in zeta-deficient mice with transgenic zeta chains that partially or completely lacked sequences required for signal transduction. The zeta chain played a role in thymic development by promoting TCR surface expression, but zeta-mediated signals were not essential because TCRs that contained signaling-deficient zeta chains promoted T cell maturation and transduced signals associated with thymic selection.

Amino Acid Sequence↗
PubMed1994

The molecular structure of the complex of Ascaris chymotrypsin/elastase inhibitor with porcine elastase.

BACKGROUND: The intestinal parasitic worm, Ascaris suum, produces a variety of protein inhibitors that defend the organism against the host's proteinases. Eight different proteins from Ascaris suum have been identified as inhibitors of serine proteinases, targeting chymotrypsin, elastase and trypsin. These inhibitors share 30-40% sequence identity with one another, but have virtually no sequence identity with members of any of the other families of serine proteinase inhibitors. RESULTS: The crystal structure of the complex of porcine pancreatic elastase with a chymotrypsin/elastase inhibitor from Ascaris suum (the C/E-1 inhibitor) has been solved to 2.4 A resolution by the molecular replacement method. The C/E-1 inhibitor exhibits a novel folding motif. There are only two small beta-sheets and two single-turn 3(10)-helices in this inhibitor. Unlike the majority of proteins, the C/E-1 inhibitor does not have a hydrophobic core. The presence and unique topography of the five disulfide bridges suggests that they play important roles in maintaining the tertiary structure of the inhibitor. In addition, the side chains of several charged residues from electrostatic and hydrogen-bonding cascades, which also probably compensate for the lack of extensive secondary structures and a hydrophobic core. The reactive-site loop of this inhibitor displays a conformation that is characteristic of most serine proteinase inhibitors. CONCLUSIONS: The structure of the C/E-1 inhibitor confirms that inhibitors from Ascaris suum belong to a novel family of proteinase inhibitors. It also provides conclusive evidence for the correct disulfide bridge connections. The C/E-1 inhibitor probably acts by a common inhibitory mechanism proposed for other substrate-like protein inhibitors of serine proteinases. The unusual molecular scaffolding presents a challenge to current folding algorithms. Proteins like the C/E-1 inhibitor may provide a valuable model system to study how the primary sequence of a protein dictates its three-dimensional structure.

Amino Acid Sequence↗
PubMed1994

Active-site mutations of the diphtheria toxin catalytic domain: role of histidine-21 in nicotinamide adenine dinucleotide binding and ADP-ribosylation of elongation factor 2.

Diphtheria toxin (DT) has been studied as a model for understanding active-site structure and function in the ADP-ribosyltransferases. Earlier evidence suggested that histidine-21 of DT is important for the ADP-ribosylation of eukaryotic elongation factor 2 (EF-2). We have generated substitutions of this residue by cassette mutagenesis of a synthetic gene encoding the catalytic A fragment (DTA) of DT, and have characterized purified mutant forms of this domain. Changing histidine-21 to alanine, aspartic acid, leucine, glutamine, or arginine diminished ADP-ribosylation activity by 70-fold or greater. In contrast, asparagine proved to be a functionally conservative substitution, which reduced ADP-ribosylation activity by < 3-fold. The asparagine mutant was approximately 50-fold-attenuated in NAD glycohydrolase activity, however. Dissociation constants (Kd) for NAD binding, determined by quenching of the intrinsic protein fluorescence, were 15 microM for wild-type DTA, 160 microM for the asparagine mutant, and greater than 500 microM NAD for the alanine, leucine, glutamine, and arginine mutants. These and previous results support a model of the ADP-ribosylation of EF-2 in which histidine-21 serves primarily a hydrogen-bonding function. We propose that the pi-imidazole nitrogen of His-21 hydrogen-bonds to the nicotinamide carboxamide, orienting the N-glycosidic bond of NAD for attack by the incoming nucleophile in a direct displacement mechanism, and then stabilizing the transition-state intermediate of this reaction.

Adenosine Diphosphate Ribose↗