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Biomedical subjects

J Huang

Publications and source records attributed to J Huang.

At least 721 records · Page 40Linked to original sources
PubMed1994

Experimental study on the occlusion of arterial blood flow by the implantation of nitinol alloy stents.

To evaluate the occlusion of arteries, 6 conic intravascular endoprosthetic stents of titanium-nickel alloy were implanted transluminally to the right external iliac arteries in 2 normal dogs and 4 normal pigs. The stent was characterized by ductility below 313 K (40 degrees C) and restoration memory-shape between 313-319 K. The diameter of the large end of conic stent was 4.0 mm (dog) and 4.5 mm(pig). The topographic anatomy showed that the external iliac artery was near complete occlusion, with a very small residual lumen (about 1 mm in diameter) in dogs at 6 months, with complete occlusion in pigs at 8 months. The histopathological examination indicated that the arterial intima of the upper branch from the stented site was smooth, and that neither inflammatory cell infiltration nor foreign giant cell reaction was found. The newly formed granulation tissue inside the stent came from emboli organization. These results suggest that the shape-memory alloy stent has good biocompatibility and the conic intravascular endoprosthetic stent might completely occlude arterial blood flow.

Alloys↗
PubMed1993

Involvement of noradrenergic and 5-hydroxytryptaminergic systems in allylnitrile-induced head twitching.

Allylnitrile induces in rats persistent behavioral abnormalities, including head twitching, following a single administration. We studied the role of 5-hydroxytryptamine (5-HT) and noradrenaline (NA) systems in the brain of rats in inducing and maintaining the head twitching. Allynitrile (1.49 mmol/kg) induced 5-HT system activation in all areas of the brain studied 1-4 days after oral administration, and a reduction in the content of NA in the hippocampus, cortex and hypothalamus 1 day after dosing, in the hippocampus, cortex, hypothalamus and midbrain 2 days after dosing, and in the hypothalamus 4 days after dosing. Allylnitrile induced no change in the content of 5-HT, 5-hydroxyindoleacetic acid (5-HIAA) or NA 7-28 days after dosing. Pretreatment with 5,7-dihydroxytryptamine (5,7-DHT) suppressed the allylnitrile-induced head twitching, and decreased the contents of 5-HT and 5-HIAA in almost all areas of the brain throughout the observation period, as well as the ratio of 5-HIAA/5-HT in the medulla oblongata plus pons from 1 to 30 days after dosing with allylnitrile. No change in NA was observed in any areas of the brain. Pretreatment with N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) increased the head twitching induced by allylnitrile, and decreased the content of NA in all areas of the brain throughout the observation period, without any change in the contents of 5-HT or 5-HIAA or in the ratio of 5-HIAA/5-HT. The present results suggest the involvement of 5-HT and NA systems in allylnitrile-induced head twitching.

5,7-Dihydroxytryptamine↗
PubMed1993

Protein phosphatases 1, 2A, and 2C are protein histidine phosphatases.

Eukaryotic cellular proteins contain phosphohistidine. To search for protein histidine phosphatases, protein histidine kinase from Saccharomyces cerevisiae was used to phosphorylate histone H4 on histidine at position 75 in the H4 amino acid sequence. Incubation of the phosphorylated histone H4 with either protein phosphatase 1, 2A, or 2C resulted in extensive removal of phosphate from the phosphorylated histone. Thus, protein phosphatases 1, 2A, and 2C are histidine phosphatases as well as serine/threonine phosphatases. Calcium/calmodulin-regulated protein phosphatase (protein phosphatase 2B) did not remove phosphate from phosphohistidine. The histidine phosphatase reaction was tested for a magnesium requirement and effects of inhibitor-1 and okadaic acid. In all cases, the protein phosphatases behaved as they do in their serine/threonine phosphatase activity. Extracts of the yeast, S. cerevisiae, contain protein histidine phosphatase activity. Quantitative measurement of phosphatase activity shows that the activity against phosphohistidine is a major activity of protein phosphatases 1, 2A, and 2C.

Carrier Proteins↗
PubMed1993

Monoclonal antibody directed against colon cancer mucin has high specificity for malignancy.

Exposure of core carbohydrate structures such as NeuAc alpha2-6GalNAc-Ser/Thr (sialosyl-Tn) in mucus glycoproteins is often associated with malignant transformation in a number of different tissues. Reagents that specifically identify such structures would be useful in the diagnosis of cancer. Monoclonal antibody JT10e has been produced against mucins from xenografts of LS174T colon cancer cells but also reacts with mucins of pancreatic cancer xenografts. The following data suggest that JT10e reacts with sialosyl-Tn: (I) reactivity with bovine and ovine submaxillary mucins; (2) reactivity sensitive to neuraminidase or mild acid; (3) inhibition of reactivity by NeuAc and NeuAc alpha2-6 lactose; and (4) lack of reactivity with other glycoproteins with related carbohydrate structures but no sialosyl-Tn. JT10e is distinguishable from 2 other antibodies which react with sialosyl-Tn, B72.3 and TKH2 because JT10e: (a) did not react with normal gastric tissue while B72.3 and TKH2 did; (b) was only partially inhibited by TKH2 and not at all by B72.3; (c) did not react with Tn antigen while B72.3 did; and (d) bound more strongly to pancreatic cancer mucins than did either B72.3 or TKH2. JT10e reacted with a high percentage of malignant colonic, pancreatic, gastric and mammary tissues but not with the corresponding normal tissues. A high percentage of patients with colonic, pancreatic, gastric, mammary and lung cancers had elevated blood levels of JT10e antigen. A number of colonic cancer patients had elevated JT10e antigen levels without corresponding elevations in CA19-9 levels. These results suggest that JT10e antibody could be used in conjunction with other mucin markers to improve the identification of malignancy in colon, and to study the structure of oligosaccharides in cancer mucins.

Animals↗
PubMed1993

Amino/carboxyl-terminal deletion mutants of human choriogonadotropin beta.

Human choriogonadotropin (hCG) contains an alpha subunit common to other members of the glycoprotein hormone family, lutropin (LH), follitropin, and thyrotropin, and a hormone-specific beta subunit. hCG beta contains a carboxyl-terminal extension of 25-30 amino acid residues not present in the other beta subunits; also, CG beta and lutropin beta have an additional 6 or 7 amino-terminal residues that are not present in follitropin beta and thyrotropin beta. To delineate the contribution of these extensions in hCG beta, site-directed mutagenesis was used to prepare several deletion fragments. Plasmids containing cDNAs for wild-type and mutant hCG beta were transiently transfected into Chinese hamster ovary cells containing a stably integrated gene for bovine alpha. Medium from the transfected cells was used in two in vitro assays with a transformed murine Leydig cell line, MA-10. The deletion fragments, des(1-7), des(111-145), and des(1-7, 111-145), associated with alpha as well as hCG beta wild-type; moreover, the potencies of the three mutant hormones were comparable to that of control. In contrast, des(1-7, 101-145)hCG beta yielded very little heterodimer, although that which formed was partially active. These results define the shortest known core fragment of hCG beta, amino acid residues 8-110, that retains significant functionality in vitro.

Animals↗
PubMed1993

Immunohistochemical study of mucin carbohydrates and core proteins in human pancreatic tumors.

BACKGROUND: Pancreatic cancer has a poor prognosis, and early diagnosis of carcinoma and discrimination between malignant and benign conditions are difficult. Many pancreatic cancer-associated antigens, such as CA 19-9, DU-PAN-2, YPan-1, and SPan-1, have been studied. However, expression of Tn, sialosyl-Tn, and T antigens in tissues of different types of pancreatic neoplasms has not been investigated systematically. Moreover, little is known about the distribution of different types of apomucins in the pancreas. METHODS: The expression of Tn, sialosyl-Tn, and T antigens and DF3 (mammary type apomucin) and intestinal MRP (intestinal type apomucin) was examined immunohistochemically in 47 pancreatic tumors: 36 invasive ductal carcinomas, 5 intraductal papillary tumors, and 6 adenomas. RESULTS: In normal pancreatic tissues, neither Tn nor sialosyl-Tn antigen was expressed. In contrast, expression of both Tn and sialosyl-Tn antigens was observed in all the invasive ductal carcinomas and intraductal papillary tumors. None of the adenomas expressed both Tn and sialosyl-Tn. DF3 antigen was expressed in all invasive ductal carcinomas but not in intraductal papillary tumors, whereas intestinal MRP was expressed in all the intraductal papillary tumors but not in the invasive ductal carcinomas. CONCLUSIONS: The results from this study suggest that the expression of the mucin core protein and mucin carbohydrate antigens is correlated with the biologic behavior of pancreatic tumors. In particular, the expression of mammary type mucin core protein and intestinal type mucin core protein showed a striking contrast between invasive ductal carcinomas with a poor prognosis and intraductal papillary tumors with a favorable prognosis.

Adenoma↗
PubMed1993

Activation of a phosphotyrosine phosphatase by tyrosine phosphorylation.

Regulation of cell proliferation, differentiation, and metabolic homeostasis is associated with the phosphorylation and dephosphorylation of specific tyrosine residues of key regulatory proteins. The phosphotyrosine phosphatase 1D (PTP 1D) contains two amino terminally located Src homology 2 (SH2) domains and is similar to the Drosophila corkscrew gene product, which positively regulates the torso tyrosine kinase signal transduction pathway. PTP activity was found to be regulated by physical interaction with a protein tyrosine kinase. PTP 1D did not dephosphorylate receptor tyrosine kinases, despite the fact that it associated with the epidermal growth factor receptor and chimeric receptors containing the extracellular domain of the epidermal growth factor receptor and the cytoplasmic domain of either the HER2-neu, kit-SCF, or platelet-derived growth factor beta (beta PDGF) receptors. PTP 1D was phosphorylated on tyrosine in cells overexpressing the beta PDGF receptor kinase and this tyrosine phosphorylation correlated with an enhancement of its catalytic activity. Thus, protein tyrosine kinases and phosphatases do not simply oppose each other's action; rather, they may work in concert to maintain a fine balance of effector activation needed for the regulation of cell growth and differentiation.

Amino Acid Sequence↗
PubMed1993

Induction of cytochrome P450 2E1 during chronic ethanol exposure occurs via transcription of the CYP 2E1 gene when blood alcohol concentrations are high.

Induction of cytochrome P450 CYP 2E1 during chronic ethanol exposure in rats has been reported by our laboratory to occur by a complex two step process. The first step occurs at relatively low blood alcohol concentrations and involves increases in CYP 2E1-dependent activities and apoprotein levels with no increases in steady-state mRNA encoding CYP 2E1. The second step of this process occurs at higher blood alcohol concentrations and involves elevated mRNA levels. In this report, we demonstrate for the first time that CYP 2E1 induction by chronic ethanol is associated with increased CYP 2E1 gene transcription and is independent of gonadal factors.

Animals↗
PubMed1993

Nerve-specific marker proteins as indicators of organic solvent neurotoxicity.

Effects of chronic exposure to n-hexane and toluene on some nerve-specific marker proteins in rat central nervous system (CNS) and peripheral nervous system (PNS) were assessed and compared. The rats were exposed to 2000 ppm n-hexane, 12 hr/day, 6 days/week, for 24 weeks, and to 1000 ppm toluene, 8 hr/day, 6 days/week, for 16 weeks. The level of neuron-specific enolase (NSE), creatine kinase-B (CK-B), and beta-S100 protein in cortex, cerebellum, spinal cord, and proximal and distal sciatic nerve was determined by enzyme immunoassay method. In n-hexane-exposed rats, the level of NSE, CK-B, and beta-S100 decreased significantly in the distal segment of the sciatic nerve, while the marker proteins in CNS and proximal sciatic nerve remained unchanged. In contrast, chronic exposure to toluene mostly affected these marker proteins in CNS tissues, displaying the increase of NSE, CK-B, beta-S100 in cerebellum, as well as the increase of beta-S100 in spinal cord. No quantitative changes of the three proteins in distal sciatic nerve were observed after exposure to toluene. n-Hexane-induced peripheral distal neuropathy and toluene-induced brain gliosis appeared to be responsible for this different pattern of biochemical changes. The present study suggests the usefulness of using these nerve-specific marker proteins to assess the solvent-related CNS and PNS neurotoxicity.

Animals↗
PubMed1993

The plant mitochondrial open reading frame orf221 encodes a membrane-bound protein.

We have shown that the open reading frame orf221 is an active mitochondrial gene which encodes a novel mitochondrial polypeptide. The orf221 sequence is common to higher plants but absent in animal and fungal mitochondria. A mitochondrial polypeptide with an apparent molecular weight of 21,000 was detected with a polyclonal antibody raised against an ORF221 fusion protein. In organello translation followed by immunoprecipitation with the anti-ORF221 antibody demonstrated that this polypeptide is encoded by the orf221 gene in plant mitochondria. The ORF221 was found to be a mitochondrial membrane protein in normal (N), cms-T, and cms-C cytoplasms of several inbred lines of maize (Zea mays L.) and in other plant species.

Cell Fractionation↗
PubMed1993

Neuron and glial cell marker proteins as indicators of heavy metal-induced neurotoxicity in neuroblastoma and glioma cell lines.

The sensitive and specific biochemical indicators for assessing chemical-induced neurotoxic insults in cell culture models have not been sufficiently explored. This study was designed to assess the usefulness of glia-specific beta-S100 protein and neuron-specific enolase (NSE) as indices of in vitro neurotoxicity of heavy metals. Glioma C6 and neuroblastoma N18TG-2 cells were grown in Dulbecco's modified Eagle's medium containing various concentrations of mercuric chloride (HgCl2) or cadmium chloride (CdCl2) for 5 days. Toxic response patterns of the neurospecific endpoints (beta-S100 and NSE), which were monitored with enzyme immunoassays, were compared with those of the non-neurospecific endpoints such as cell viability, total cellular protein, lactate dehydrogenase (LDH) activity, and cumulative glucose consumption in the two cell lines. Both HgCl2 and CdCl2 produced dose-dependent inhibition of neurospecific endpoints and non-specific endpoints. However, by ranking the EC50 values (effective concentration producing half-maximal inhibition) for various endpoints, the lowest values were found for beta-S100 in C6 cells, and for NSE in N18TG-2 cells. In lower and intermediate concentrations, the inhibitory effects of the heavy metals on the content of beta-S100 and NSE occurred in the absence of any detectable effect on intracellular LDH activity, and independently of total cellular protein inhibition. The sensitive and excess responses of the neurospecific endpoints relative to that of the non-specific endpoints may reflect the specific neurotoxic insults of the heavy metals on the cultured cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Experimental study on respiratory sensitivity to inhaled toluene diisocyanate.

Groups of guinea pigs were exposed via inhalation to toluene diisocyanate (TDI) ranging from 0.02 to 1.0 ppm for 3 h/day on 5 consecutive days. Three weeks later, guinea pigs were challenged with TDI-GSA conjugates. Evaluations were based on TDI specific antibodies, pulmonary response and antigen stimulated histamine release from lung mast cells (LMC). The results indicated that both the antibody titer and the severity of pulmonary response followed a concentration-dependent pattern, with corresponding threshold levels. Antibodies and pulmonary responses were undetectable in animals exposed to 0.02 ppm TDI; however, exposure to 0.2 ppm TDI resulted in significant antibody production and pulmonary responses. Animals showed higher antibody titers and more severe pulmonary responses as TDI concentration increased from 0.6 ppm to 1.0 ppm. A discrepancy which was noted between antibody production and pulmonary responses was thought to be relevant to the discrimination of the potentials of antigen stimulated histamine release from LMC mediating between these two responses.

Administration, Inhalation↗
PubMed1993

Mutagenesis of the 'determinant loop' region of human choriogonadotropin beta.

The hormone-specific beta subunits of the four human glycoprotein hormones are homologous, and mapping studies are underway in many laboratories to delineate the amino acid residues responsible for receptor binding and activation. Results on the human choriogonadotropin beta (hCG beta) subunit, obtained using synthetic peptides, chemically modified derivatives, and mutant forms prepared via site-directed mutagenesis, have suggested that amino acid residues enclosed by the purported disulfide loop between Cys-93 and Cys-100 may contribute to receptor binding and perhaps specificity. Indeed, the 93-100 amino acid sequence is referred to as a determinant loop. We have used site-directed mutagenesis to prepare single amino acid residue replacements at positions not previously investigated in full length beta subunits; these include Arg-95, Ser-96, Thr-97, and Thr-98. In addition, Leu-92 was studied in an effort to determine whether changes immediately adjacent to the determinant loop alter receptor binding. The wild-type and mutant cDNAs for hCG beta were subcloned into a Prsv expression vector and transiently transfected into Chinese hamster ovary cells containing a stably integrated gene for bovine alpha. The concentrations of total expressed hCG beta in heterodimer form with the bovine alpha subunit were determined by radioimmunoassays. The mutant gonadotropins were assayed in vitro using a competitive binding assay with [125I]hCG and progesterone production, both in the transformed murine Leydig cell line, MA-10. Mutant beta subunits containing the replacements Lys-92, Ser-95, Asp-96, and Tyr-97 exhibited normal alpha subunit binding.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Symbolic decision support in medical care.

Symbolic decision procedures offer a flexible alternative to classical quantitative procedures for decision making, particularly when precise parameters (such as probabilities) are hard to estimate. One such procedure, based on a logic of argumentation, is described. Specifications of inference methods for such functions as proposing and refining decision options, deducing and inheriting arguments for and against options, and selecting among alternatives are presented. These exploit declarative models for patient data, domain and task knowledge. A simple method for translating the specifications into executable Prolog is described. A practical and efficient toolset for using the procedure in a wide range of clinical environments is being developed within the DILEMMA project of the European Commission's Advanced Informatics in Medicine research programme.

Databases, Factual↗
PubMed1993

Monte Carlo simulation of lipid mixtures: finding phase separation.

The nonideal mixing of phosphatidylserine (PS) and phosphatidylcholine (PC) binary lipid mixtures was studied by computer simulation based on a model wherein the excess energy of mixing is divided between an electrostatic term and one adjustable term delta Em that includes all other nonideal interactions. The lateral distribution of the lipids and the energy of the mixtures were obtained by using Kawasaki relaxation in a canonical ensemble. The Gibbs free energies were calculated by Kirkwood's coupling parameter method. The simulation results are strongly dependent on simulation size for sizes smaller than about 1000 lipids. Nonideal interaction between lipids can result in large scale separation of lipid phases of different composition at reasonable delta Em values as well as clustering of like lipids. In plots of total Gibbs free energy of mixing versus PS mole fraction in PS/PC, the boundaries of the two phase region could be accurately determined. The electrostatic interaction influences cluster size and shape, and also the composition of phases in the two-phase region.

Biophysical Phenomena↗
PubMed1993

Nonideal mixing of phosphatidylserine and phosphatidylcholine in the fluid lamellar phase.

The mixing of phosphatidylserine (PS) and phosphatidylcholine (PC) in fluid bilayer model membranes was studied by measuring binding of aqueous Ca2+ ions. The measured [Ca2+]aq was used to derive the activity coefficient for PS, gamma PS, in the lipid mixture. For (16:0, 18:1) PS in binary mixtures with either (16:0, 18:1)PC, (14:1, 14:1)PC, or (18:1, 18:1)PC, gamma PS > 1; i.e., mixing is nonideal, with PS and PC clustered rather than randomly distributed, despite the electrostatic repulsion between PS headgroups. To understand better this mixing behavior, Monte Carlo simulations of the PS/PC distributions were performed, using Kawasaki relaxation. The excess energy was divided into an electrostatic term Uel and one adjustable term including all other nonideal energy contributions, delta Em. Uel was calculated using a discrete charge theory. Kirkwood's coupling parameter method was used to calculate the excess free energy of mixing, delta GEmix, hence In gamma PS,calc. The values of In gamma PS,calc were equalized by adjusting delta Em in order to find the simulated PS/PC distribution that corresponded to the experimental results. We were thus able to compare the smeared charge calculation of [Ca2+]surf with a calculation ("masked evaluation method") that recognized clustering of the negatively charged PS: clustering was found to have a modest effect on [Ca2+]surf, relative to the smeared charge model. Even though both PS and PC tend to cluster, the long-range nature of the electrostatic repulsion reduces the extent of PS clustering at low PS mole fraction compared to PC clustering at an equivalent low PC mole fraction.

Biophysical Phenomena↗