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Biomedical subjects

M Huang

Publications and source records attributed to M Huang.

At least 217 records · Page 12Linked to original sources
PubMed1996

Cocaine down-regulates IL-2-induced peripheral blood lymphocyte IL-8 and IFN-gamma production.

Cocaine has multiple immunomodulatory effects, including the ability to influence cytokine release in immunoeffector cells. Little is known, however, regarding the effects of cocaine on cytokine production by human peripheral blood lymphocytes (PBL). The effect of cocaine on PBL cytokine profiles and the molecular mechanisms responsible for the modulation of cytokine mRNA expression were investigated. To evaluate the effects of cocaine on cytokine production, conditioned supernatant from IL-2-stimulated PBL was evaluated by cytokine-specific ELISA (IL-4, IL-5, IL-8, IL-10, IFN-gamma, and TGF-beta) following in vitro cocaine exposure. Cocaine abrogated the IL-2-induced production of IFN-gamma and IL-8 in a dose-responsive manner. Cocaine also decreased PBL IFN-gamma and IL-8 mRNA expression as determined by Northern blot and slot blot analysis. Cocaine did not affect the stability of the IFN-gamma and IL-8 mRNA. Nuclear run-on assays revealed that cocaine down-regulated the rate of IFN-gamma and IL-8 transcription. These findings suggest that the immunomodulatory effects of cocaine may be mediated, in part, by modification of lymphocyte cytokine production.

Cocaine↗
PubMed1996

Peptide nucleic acid characterization by MALDI-TOF mass spectrometry.

Peptide nucleic acids (PNAs) are a new class of DNA mimics in which the regular nucleobases of adenine, thymine, cytosine, and guanine are connected via a peptide-like backbone. PNA molecules retain the same Watson-Crick base pairing as regular oligonucleotides, with the added benefits of greater specificity and resistance to enzymatic digestion. While the use of PNAs has grown rapidly because of their potential applications in biotechnology, little work has been done on developing analytical procedures for characterizing them. We have found matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry to be an effective tool for PNA analysis. PNA molecules survive the MALDI process intact and are easily ionized with almost no multiply-charged species. These features allow mixtures to be easily characterized. Traditional protein matrices (e.g., sinapinic acid,2,5-dihydroxybenzoic acid, alpha-cyano-4-hydroxycinnamic acid) were found to be superior to DNA matrices (e.g., trihydroxy-acetophenone, 3-hydroxypicolinic acid, picolinic acid). In addition, the new DNA matrix 6-aza-2-thiothymine worked well. The ability of MALDI-TOF-MS to ascertain PNA purity and sequence information at low picomole levels will be important as greater quality control of PNA synthesis is needed (e.g., when PNAs are used as antisense or antigene drugs).

Base Sequence↗
PubMed1996

Structure and mutational analysis of Rab GDP-dissociation inhibitor.

The crystal structure of the bovine alpha-isoform of Rab GDP-dissociation inhibitor (GDI), which functions in vesicle-membrane transport to recycle and regulate Rab GTPases, has been determined to a resolution of 1.81 A. GDI is constructed of two main structural units, a large complex multisheet domain I and a smaller alpha-helical domain II. The structural organization of domain I is surprisingly closely related to FAD-containing monooxygenases and oxidases. Sequence-conserved regions common to GDI and the choroideraemia gene product, which delivers Rab to catalytic subunits of Rab geranylgeranyltransferase II, are clustered on one face of the molecule. The two most sequence-conserved regions, which form a compact structure at the apex of GDI, are shown by site-directed mutagenesis to play a critical role in the binding of Rab proteins.

Adaptor Proteins, Signal Transducing↗
PubMed1996

Highly efficient protein separations in high-performance capillary electrophoresis, using hydrophilic coatings on polysiloxane-bonded columns.

Three methods for preparing hydrophilic coatings on polysiloxane bonded CElect H-type capillary electrophoresis columns have been shown. The polyalkylsiloxane-bonded phase is the first coating layer on the capillary surface, and nonionic surfactant, hydrophilic polymer, or polymer surfactant, adsorbed onto this first later through hydrophobic interactions, forms the second coating layer. The resultant capillary surfaces are inert, hydrophilic, and suitable for highly efficient protein separations. The effectiveness and applicability of these capillary surface modification methods were tested for the separations of a variety of proteins over a wide range of buffer pH values under different capillary electrophoretic operations modes.

Buffers↗
PubMed1996

Vasoactive intestinal peptide in cirrhotic rats: hemodynamic effects and mesenteric arterial receptor characteristics.

Vasoactive intestinal peptide (VIP) blood levels in cirrhosis are elevated, but its hemodynamic and receptor characteristics remain unclarified. We aimed to quantify VIP receptor characteristics in mesenteric arteries, plasma VIP concentration by radioimmunoassay (RIA), and the hemodynamic effects of VIP infusion in bile duct-ligated (BDL) cirrhotic and sham-operated control rats. Mesenteric arterial membranes were prepared by ultracentrifugation, and receptor characteristics were studied using 125I-labeled VIP as a radioligand. For the hemodynamic study, there were four groups: cirrhotic and sham-operated rats were infused with either VIP (50 ng/kg/min for 15 minutes) or equivolumic isotonic saline. Regional blood flows were measured in conscious rats with radioactive microspheres. Receptor studies showed high- and low-affinity binding sites for VIP, which had similar equilibrium dissociation constants (binding affinities) and receptor densities for both the cirrhotic and control rats. Plasma VIP concentrations were significantly elevated in the cirrhotic rats. In both cirrhotic and sham-operated rats, VIP infusion produced plasma levels approximately twofold to threefold increased over the basal levels observed in cirrhotic rats. In cirrhotic rats, VIP infusion did not affect any hemodynamic parameter, whereas in the sham-operated rats VIP infusion significantly increased the mesenteric visceral blood flow. These results show that the hyporesponsiveness to VIP in cirrhotic rats is not attributable to receptor downregulation, implying postreceptor alterations. This suggests that VIP may not play a major role in the maintenance of splanchnic hyperemia in cirrhosis.

Analysis of Variance↗
PubMed1996

Optimized heterologous expression of the polymorphic human glutathione transferase M1-1 based on silent mutations in the corresponding cDNA.

An expression clone for large-scale production of the polymorphic human glutathione transferase (GST) M1-1 has been developed. Heterologous expression in Escherichia coli afforded a yield of 100 mg of GST M1-1 per 3 liters of culture medium, corresponding to an approximately 10-fold increased yield compared to the parental expression construct. Overproduction of the enzyme was dependent on the codon usage in the 5' region of the DNA sequence encoding glutathione transferase M1-1. High-level expression clones were generated by a combination of random silent mutations in selected wobble positions in the coding sequence and immunoselection of clones from the library of random mutants. The strategy used is generally applicable for the production of recombinant proteins provided that a suitable selection procedure is available for identifying the desired mutants.

Amino Acid Sequence↗
PubMed1996

Morphology of diaphragm neuromuscular junctions on different fibre types.

We hypothesize that the morphology of the neuromuscular junction on different muscle fibre types varies, reflecting differences in activation history. In the rat diaphragm muscle, we used a three-colour fluorescent immunocytochemical technique to simultaneously visualize (1) innervating axons and presynaptic nerve terminals, (2) motor endplates, and (3) myosin heavy chain isoform expression (muscle fibre type). Laser-scanning confocal microscopy was then used to optically section the triple-labelled muscle fibres, and create three-dimensional views of the neuromuscular junction. Type I fibres were innervated by the smallest axons, and type IIa, IIx and IIb fibres by progressively larger axons. Absolute planar areas of nerve terminals and endplates progressively increased from type I, IIa, IIx to IIb fibres. When normalized for fibre diameter, planar areas of nerve terminals were largest on type I fibres, with no difference among type II fibres. The normalized planar area of endplates were larger for type I and IIb fibres, compared to type IIa and IIx fibres. The three-dimensional surface area of endplates was largest on type I fibres, with no differences across type II fibres. When normalized for fibre diameter, endplate surface areas increased progressively from type I, IIa, IIx to IIb fibres. The branching patterns of both nerve terminals and endplates varied across fibre types. The number of nerve terminal and endplate branches increased progressively from type I, IIa, IIx to IIb fibres. Conversely, individual branch length was longest on type I fibres, and shortest on type IIb fibres. The extent of overlap of pre- and postsynaptic elements of the neuromuscular junction decreased progressively on type I, IIa, IIx and IIb fibres. We conclude that these morphological differences at the neuromuscular function of different fibre types reflect differences in activation history and may underlie phenotypic differences in neuromuscular transmission.

Animals↗
PubMed1996

The effect of xenobiotic acetylation on interorgan metabolism of glucose in fasted rats.

The effect of cytosolic acetylation on interorgan glucose metabolism was studied by arteriovenous (AV) difference and tracer kinetic techniques in fasted, ketamine-anesthetized rats. The administration of sulfamethazine (SMZ, 2 mmol/kg, i.p.) resulted in 39% and 313% increases in hepatic contents of glucose and lactate, respectively. Plasma concentrations of glucose and lactate in the aorta, portal vein and hepatic vein also increased (33-43% for glucose, and 86-200% for lactate). Net hepatic release of glucose was not significantly different from the control. Net hepatic uptake of lactate increased 72-151% in the SMZ-treated rats. The concentration and hepatic gradient of alanine were little changed in the SMZ-treated rats. The rates of turnover for plasma glucose, estimated from [3-3H]-glucose, were not significantly different between the control and SMZ-treated rats. The rate of glucose recycling, estimated from the difference in the rates of turnover between [3-3H]-and[U-14C]-glucose, decreased by 42% in the SMZ-treated rats. Muscle glycogen in the SMZ-treated rats also decreased (33%). In conclusion, our data indicate that cytosolic acetylation can affect not only ketogenesis, as we have previously reported, but also interorgan metabolism of glucose. Although direct evidence is not available, increases in the levels of plasma and liver glucose suggest that gluconeogenesis is increased in the SMZ-treated rats. A net loss of lactate from muscle glycogen store to the liver is indicated by the increase in hepatic uptake of lactate and the decrease in the rate of glucose recycling in the rats treated with SMZ.

Acetylation↗
PubMed1996

The variable expressivity of a family with central areolar pigment epithelial dystrophy.

PURPOSE: To clarify the nosology of autosomal dominant central areolar pigment epithelial dystrophy (CAPED) as previously described. METHODS: The authors studied a family of 69 members spanning six generations with a macular dystrophy. Thirty-four patients were examined, and those found to be affected underwent further testing, including visual fields, electrophysiologic studies, and fluorescein angiography. Family history and medical records were used in three additional deceased patients. RESULTS: Eleven patients were identified as having CAPED. The phenotype was inherited in an autosomal dominant fashion. Six of these patients were examined by us and had mid-life onset (at 32-53 years) of progressive visual loss (20/50--counting fingers), occurring over a 3- to 10-year period. These subjects had circumscribed hypopigmented maculae, retinal pigment epithelial window defects on fluorescein angiography, central scotomas, and electrophysiologic studies, ranging from normal to severely abnormal. Three deceased patients were presumed to have CAPED by review of records or family history. Two additional patients examined had mild macular changes but good visual acuity and no significant abnormalities on electrophysiologic studies. The latter two patients are presumed to have had early manifestations of CAPED. CONCLUSION: This family demonstrates that CAPED is an autosomal-dominant hereditary macular dystrophy which has late-onset and variable expressivity.

Adult↗
PubMed1996

Thrombin receptor-related hemostatic defect after cardiopulmonary bypass.

Platelet abnormalities have been blamed for the hemostatic defect that develops after cardiopulmonary bypass (CPB), but investigators have not been able to agree upon an intrinsic platelet abnormality responsible for the observed defect. To better define the blood components responsible for this post-operative hemostatic defect, we compared platelet function in whole blood (WB) to that in platelet-rich plasma (PRP) in 33 patients undergoing coronary artery bypass grafting. We measured platelet aggregation in response to various platelet agonists, including thrombin and TRAP-6 (a 6-amino acid peptide that activates the thrombin "tethered ligand" receptor site). In WB there was a lasting, diminished response to TRAP-6, but not to gamma-thrombin, after CPB. Control experiments showed that this diminished response to TRAP-6: (1) was not related to heparin or heparin-protamine complexes, (2) was not the result of hemodilution during CPB, (3) was not related to increased amounts of naturally occurring enzymes (aminopeptidases) that degrade TRAP, and (4) was not able to be reversed by the addition of as much as a 10-fold excess of the usual TRAP-6 aggregating dose to WB preparations. In contrast, no corresponding defect in platelet aggregation could be identified in PRP obtained from patients after CPB. These results show that, in post-operative blood samples, blood components present in WB and not in PRP (eg, red blood cells, activated white cells or platelets bound to white cells) diminish the ability of TRAP peptides to activate the thrombin receptor but do not decrease the ability of gamma-thrombin to induce platelet aggregation. This suggests that for circulating platelets after CPB: (1) interactions of platelets with other blood cell elements are the cause of altered postoperative platelet reactivity rather than any intrinsic CPB-induced platelet defect, (2) drugs, such as aprotinin, that limit activation of white cells and the fibrinolytic system may also have beneficial effects on platelet function after CPB, and (3) alternate mechanisms exist that allow thrombin, but not TRAP-6, to activate platelets normally after CPB (perhaps a second, as yet undefined, thrombin receptor).

Cardiopulmonary Bypass↗
PubMed1996

Interleukin-8 inhibits non-small cell lung cancer proliferation: a possible role for regulation of tumor growth by autocrine and paracrine pathways.

Interleukin-8 (IL-8) is an 8 kD chemokine and angiogenic factor produced by alveolar macrophages, endothelial cells, monocytes, fibroblasts, T lymphocytes, and epithelial cells in response to a variety of stimuli, including LPS, TNF-alpha, IL-1, IL-7, and hypoxia. Pulmonary tumors produce a variety of growth factors and cytokines that may act in both autocrine and paracrine fashion. A549, a well-characterized human lung adenocarcinoma line, was cloned for different levels of IL-8 production by limiting dilution. Clone 3B4 produced 361 +/- 73 pg/ml, and clone 2B2 produced 7818 +/- 614 pg/ml of IL-8 (p = 0.003). Clone 3B4 proliferated at 1.7 times the rate of 2B2. Anti-IL-8 reversed the decrement in proliferation of clone 2B2 by 50%, but recombinant IL-8 decreased the proliferation of 3B4 by 40-55% compared with control. In addition to A549, three other non-small cell lung cancer (NSCLC) lines showed significantly decreased proliferation in response to exogenous recombinant IL-8 (5-30 ng/ml; p < 0.05). These findings suggest that in addition to its chemotactic and angiogenic activities, IL-8 may inhibit lung tumor proliferation by both autocrine and paracrine pathways.

Antigens, CD↗
PubMed1996

Changes in average blood pressure and incidence of high blood pressure 1983-1984 to 1987-1988 in four population cohorts in the People's Republic of China. The PRC-USA Cardiovascular and Cardiopulmonary Epidemiology Research Group.

OBJECTIVE: To assess comparative changes in systolic and diastolic blood pressure and incidence of high blood pressure over 4 years, and factors related to these changes, in northern and southern, urban and rural adults in the People's Republic of China. SETTING: This is a prospective study of populations surveyed by standardized methods in 1983-1984 and 1987-1988 in north China, Beijing area steel mill workers and farmers, and south China, Guangzhou area shipyard workers and farmers. SUBJECTS: The subjects were 8805 men and women aged 35-54 years at baseline (1983-1984), of whom 7338 were non-hypertensive (systolic blood pressure < 140, diastolic blood pressure < 90 mmHg, not being administered antihypertensive drugs). MAIN OUTCOME MEASURES: The main outcome measures were 4-year changes in systolic and diastolic blood pressures and the 4-year incidence of high blood pressure in persons not hypertensive at baseline. RESULTS: At baseline, the average systolic and diastolic blood pressures were higher for Beijing than for Guangzhou cohorts. At resurvey the average systolic blood pressure had increased for seven of eight sex-city-setting cohorts (all but Guangzhou urban men). The Beijing urban cohorts had the greatest increases (men 6.2 mmHg, women 4.9 mmHg, slopes of 1.6 and 1.2 mmHg/year). The incidence of high blood pressure was higher for Beijing than for Guangzhou cohorts in all four comparisons (men and women, urban and rural). Beijing men, urban and rural, had the highest incidence rates (about 21%). In multiple logistic analyses by sex, variables significantly related to 4-year high blood pressure incidence were city, baseline systolic blood pressure and body mass index, change in weight, and, for men, baseline alcohol use and heart rate. CONCLUSION: Modifiable lifestyle traits, previously shown to be related to blood pressure and high blood pressure in cross-sectional studies, also relate to the incidence of hypertension.

Adult↗
PubMed1996

Bactericidal activity of a synthetic peptide (CG 117-136) of human lysosomal cathepsin G is dependent on arginine content.

The importance of individual amino acids in mediating the broad-spectrum bactericidal action of a 20-mer amphipathic, cationic peptide (CG 117-136) of human lysosomal cathepsin G was determined by using a single amino acid replacement strategy. This strategy revealed an important role for arginine because loss of any of the four arginine residues in CG 117-136 due to substitution with alanine, citrulline, or lysine residues resulted in a reduction of its bactericidal activity against both Pseudomonas aeruginosa ATCC 27853 and Staphylococcus aureus ATCC 33593. However, the replacement of a single alanine residue in CG 117-136 with arginine, but not glutamic acid, enhanced the activity of CG 117-136 against both P. aeruginosa and S. aureus. The importance of certain bulky, nonpolar amino acids for the bactericidal activity of CG 117-136 was also evident, since their substitutions by alanine diminished bactericidal activity. Accordingly, contributions of hydrophobic amino acids and structural considerations of the guanidinium side chain of arginine are major determinants in the broad-spectrum antimicrobial action of CG 117-136.

Amino Acid Sequence↗
PubMed1996

The improved PAS-ELISA method for the diagnosis of the pathogen for banana mosaic heart rot disease.

As a fast and practical immunological test, ELISA has been widely applied both in research and diagnosis of plant viruses [1]. In its research utility, PAS-ELISA has been proven as an effective measure to obtain CMV-free micropropagated plantlets. In large-scale micropropagation of banana plantlets, we have been using it in our Quality Control Department to prepare CMV-free and/or TMV-free germplasm. From large-scale testing, we have found that component(s) in banana tissue can cause a nonspecific reaction which severely interferes with the diagnostic results, making the average optical density (OD490nm) value a much higher false positive, leading to an abnormally high percentage loss of the germplasm prepared. The procedure for preparation of the antigen extract from banana tissue has been modified to eliminate the false positive.

Enzyme-Linked Immunosorbent Assay↗