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Biomedical subjects

H Huang

Publications and source records attributed to H Huang.

At least 523 records · Page 29Linked to original sources
PubMed1993

Analysis of lectin receptors in normal nasal mucosa, nasal polyp, inverted papilloma and papillary adenocarcinoma.

In order to investigate the changes in glycoprotein structure in the process of cellular differentiation of the nasal mucosa, formalin-fixed, paraffin-embedded biopsy specimens of normal nasal mucosae, nasal polyps, inverted papillomas and papillary adenocarcinomas were analysed by the Avidin Biotin-Peroxidase Complex technique for the demonstration of peanut agglutinin (PNA) receptors, concanavalin ensifomis agglutinin (ConA) receptors, ulex europeaus agglutinin (UEA-I) receptors, wheat germ agglutinin (WGA) receptors, carcino-embryonic antigen (CEA) and keratin. The quantity and distribution of PNA receptors, ConA receptors, UEA-I receptors and CEA were different, in relation to the varying pathological changes. The results suggest that the glycoprotein structure in the cells of the nasal mucosa will change following their differentiation and malignant transformation, which may be helpful in establishing the diagnosis.

Adenocarcinoma, Papillary↗
PubMed1993

DNA excision repair as a component of adaptation to low doses of ionizing radiation in Escherichia coli.

In this study we examined whether or not DNA excision repair is a component of adaptation induced by very low-dose ionizing radiation in Escherichia coli, a well-characterized prokaryote, and investigated the relationship between enhanced excision repair and the SOS response. Competent E. coli cells were irradiated using low doses (0.1-10 Gy) of 137Cs gamma-rays, allowed to recover for 2 h and were then transformed using pUC18 DNA containing approximately 22 oxidized thymine residues (thymine glycols) per molecule. Successful transformants were identified by recovery of plasmid-borne ampicillin resistance and the resulting data (colony counts) were used to calculate ratios of plasmid recovery in irradiated to control cells. Results showed that cells irradiated with very low doses (0.1-0.5 Gy) were up to 30-40% more efficient at utilizing thymine glycol-containing pUC18 DNA. The enhanced excision repair by very low doses (< 0.5 Gy) of gamma-rays was shown to be independent of the recA-controlled SOS response in experiments using recA cells or cells carrying recA-lacZ gene fusions. The stimulating effect in AB1157 prototype cells were subsequently confirmed using a DNA precipitation assay in which DNA incision events were accumulated by inhibiting DNA ligation with ethidium bromide. Our data suggest that there seems to be narrow 'windows' of dose-effect for the induction of SOS-independent DNA excision repair. Being similar to mammalian cell studies, the dose range for this effect was about 200-fold less than D37 for radiation survival.

Adaptation, Physiological↗
PubMed1993

Angiotensin-converting enzyme inhibition does not suppress plasma angiotensin II increase during exercise in humans.

Physical effort stimulates the reninangiotensin system (RAS). We studied the effect of an angiotensin-converting enzyme inhibitor (ACE inhibitor) in a double-blind placebo-controlled study, on eight volunteers undergoing physical stress on an ergometric bicycle. The effects of captopril (C) (50 mg, three times daily for 3 days) on arterial pressure (AP), O2 consumption (VO2), variations in auricular natriuretic factor (ANF), renin, angiotensin II (AII) plasma levels, as well as glomerular filtration rate (GFR) and microalbuminuria (MA) were evaluated. The different parameters were compared by analysis of variance (ANOVA). The pressure profile and VO2 were not modified by ACE inhibitor. Exercise stimulates release of renin; this action was greater with captopril administration (treatment effect: p < 10(-4), indicating blockade of the RAS. This inhibition was incomplete because AII levels increased markedly when captopril was given (no treatment effect: p < 0.37). Finally, ACE inhibitor resulted in decreased GFR (p = 115 +/- 5.8 ml/mn-1, C = 91.1 +/- 4, p < 0.05) with exercise without modification of MA. ACE inhibitor administration does not modify the physical performance of nonathletic subjects; AII is significantly increased with exercise despite captopril treatment; ACE inhibitor decreases GFR significantly but does not influence MA with prolonged physical effort.

Adult↗
PubMed1993

Immunolocalization of the G protein alpha subunit encoded by the GPA1 gene in Arabidopsis.

Heterotrimeric GTP binding proteins (G proteins) are important signal transducers in lower eukaryotes and in animal cells. In plants, the occurrence of GTP binding proteins has been reported, but their biological function remains unclear. Two genes coding for G protein alpha subunits have been cloned: GPA1 in Arabidopsis and TGA1 in tomato. To gain some insights into the function of GPA1, we describe an extensive immunolocalization of GPalpha1, the gene product of GPA1, during Arabidopsis development. Our results show that the GPalpha1 is present through all stages of development and in all organs examined, with the exception of mature seeds. It is expressed in roots, floral stem, rosette leaves, cauline leaves, flowers, and seed pods. Interestingly, the level of GPalpha1 protein is higher in immature organs than in mature organs. GPalpha1 is present at a high level in the root meristem and elongation zone, in the shoot and floral meristems, and in the leaf primordium and floral organ (sepal, petal, stamen, and gynoecium) primordia. During flower development, dividing microspores, but not mature pollen, show high levels of GPalpha1. During pollination, GPalpha1 is present in the growing pollen tubes. The protein is also present in nectaries and developing ovules and, after fertilization, in developing embryos. In mature tissue, GPalpha1 is preferentially found in the vascular system but is also present in other cell types. The complexity of the GPalpha1 localization pattern suggests that GPalpha1 might be involved in different signaling pathways depending on the developmental stage.

Amino Acid Sequence↗
PubMed1993

A positive correlation between the precursor frequency of cytotoxic lymphocytes to autologous Epstein-Barr virus-transformed B cells and antibody titer level against Epstein-Barr virus-associated nuclear antigen in healthy seropositive individuals.

A limiting dilution analysis was established to determine the precursor frequency (PF) of cytotoxic lymphocytes against autologous B cells transformed with the Epstein-Barr virus (EBV). This method was found to detect mainly self-restricted T-cell activity and little non-self-restricted cytotoxicity. The mean PF in 21 healthy EBV-seropositive persons was 1.4 x 10(-3) (range: 0.03 x 10(-3) to 8.7 x 10(-3)) for peripheral blood mononuclear cells, whereas 4 samples of mononuclear cells obtained from umbilical cord blood had PFs below 0.007 x 10(-3). A positive correlation was observed between the PF and serum antibody titers against EBV-associated nuclear antigen among the seropositive persons.

Antibodies, Viral↗
PubMed1993

Visualisation of arterial structure in vivo with intravascular ultrasound.

BACKGROUND: Contrast angiography provides a silhouette of the arterial lumen, but does not give information about arterial wall structure. Catheter-tip ultrasound transducers can now provide a cross-sectional image of the arterial wall. This study examined the pathological correlation of intravascular ultrasound images and the accuracy of ultrasound measurements of vascular geometry. METHODS: Intravascular ultrasound images were obtained with a mechanically rotated catheter-tip transducer and recorded on videotape. Initial validation studies were performed in fresh, post-mortem arterial specimens, which were filled with saline at physiological pressures. Ultrasound images at specific sites were compared with the pathological findings at that site and measurements of luminal diameter were compared with corresponding angiographic measurements. Subsequently, intravascular ultrasound was employed to examine the aorta, ilio-femoral and coronary arteries in patients undergoing balloon angioplasty. RESULTS: The pathological correlations showed that intravascular ultrasound can detect early initial thickening and mild atherosclerotic lesions that do not result in luminal deformation. Ultrasound images provided definition of calcified, fibrotic and lipid-filled lesions. Ultrasound measurements of luminal diameter correlated well with pathology measurements (r = 0.93), as did ultrasound measurements of plaque area (r = 0.89). The in vivo studies demonstrated that intravascular ultrasound can define atheroma lesions not evident on contrast angiography and permits detailed evaluation of the results of interventions such as balloon angioplasty. CONCLUSIONS: Intravascular ultrasound provides a unique window upon arterial structure and pathology in humans. Ultrasound images allow accurate measurements of vascular geometry and define early atheromatous lesions that are not evident with angiography.

Arteries↗
PubMed1993

Genetic definition of the substrate selectivity of outer membrane porin protein OprD of Pseudomonas aeruginosa.

Earlier studies proved that Pseudomonas aeruginosa OprD is a specific porin for basic amino acids and imipenem. It was also considered to function as a nonspecific porin that allowed the size-dependent uptake of monosaccharides and facilitation of the uptake of quinolone and other antibiotics. In the present study, we utilized P. aeruginosa strains with genetically defined levels of OprD to characterize the in vivo substrate selectivity of this porin. An oprD::omega interposon mutant was constructed by gene replacement utilizing an in vitro mutagenized cloned oprD gene. In addition, OprD was overexpressed from the lac promoter by cloning the oprD gene into the broad-host-range plasmid pUCP19. To test the substrate selectivity, strains were grown in minimal medium with limiting concentrations of the carbon sources glucose, gluconate, or pyruvate. In minimal medium with 0.5 mM gluconate, the growth rates of the parent strain H103 and its oprD::omega mutant H729 were only 60 and 20%, respectively, of that of the OprD-overexpressing strain H103(pXH2). In contrast, no significant differences were observed in the growth rates of these three strains on glucose or pyruvate, indicating that OprD selectively facilitated the transport of gluconate. To determine the role of OprD in antibiotic uptake, nine strains representing different levels of OprD and OprF were used to determine the MICs of different antibiotics. The results clearly demonstrated that OprD could be utilized by imipenem and meropenem but that, even when substantially overexpressed, it could not be significantly utilized by other beta-lactams, quinolones, or aminoglycosides. In addition, competition experiments confirmed that imipenem had common binding sites with basic amino acids in the OprD channel, but not with gluconate or glucose.

Amino Acids, Diamino↗
PubMed1993

Mortality from lung cancer among copper miners.

A cohort mortality study of lung cancer in 7088 copper miners was made from 1 January 1969 to 31 December 1988. There was an excess of deaths from lung cancer in the copper miners. The standardised mortality ratio (SMR) was 147 (p < 0.01). The SMR increased with calendar period. There was a higher risk of deaths from lung cancer in the miners employed in the 1950s. Age at the start of exposure had no effect on the risk of lung cancer. The risk of death from lung cancer increased with the duration of exposure and the time since first exposure. The SMR for lung cancer was 173 in underground miners and 193 for drilling miners (both p < 0.01). These data show that exposure to dust is associated with an excess of deaths from lung cancer in copper miners whereas exposure to radiation does not seem to carry such risk.

Adolescent↗
PubMed1993

Regulation of angiotensin II receptors on ventricular myocytes after myocardial infarction in rats.

To determine the effects of acute myocardial infarction on the regulation of angiotensin II (Ang II) receptors and contractile performance of left and right ventricular myocytes, coronary artery ligation was surgically induced in rats, and Ang II receptor density and affinity and the mechanical properties of surviving muscle cells were examined 1 week later. Physiological determinations of cardiac pump function revealed the presence of ventricular failure, which was associated at the cellular level with a depression in the velocity of myocyte shortening and relengthening, a prolongation of time to peak shortening, and a reduction in the extent of cell shortening. These abnormalities in single-cell function were more prominent in left than in right ventricular myocytes. Cellular hypertrophy was documented by increases in cell length and width, which were also greater in the spared myocytes of the infarcted left ventricle. Reactive hypertrophy was accompanied by a 1.84- and 1.85-fold increase in the density of Ang II receptors on left and right myocytes, respectively. On the other hand, the affinity of Ang II receptors for the radiolabeled antagonist was not altered. However, Ang II-stimulated phosphoinositol turnover was enhanced by 3.7- and 2.5-fold in left and right myocytes, respectively, after infarction. Ventricular myocytes were found to possess the AT1 receptor subtype exclusively. In conclusion, myocardial infarction leads to impairment in the contractile behavior of the remaining cells and to the activation of Ang II receptors and effector pathway associated with these receptors, which may be involved in the reactive growth adaptation of the viable myocytes.

Angiotensin Receptor Antagonists↗
PubMed1993

Mechanism of the preserving effect of aprotinin on platelet function and its use in cardiac surgery.

The deficiency of platelet function is the main defect of the hemostatic mechanism during cardiopulmonary bypass, which greatly exacerbates the postoperative bleeding complications. In this study, we assessed, from basic and clinical perspectives, the mechanism of relieving platelet damage by means of aprotinin. In vitro research confirmed that the addition of urokinase (40 U/ml) to platelet-rich plasma and the addition of plasmin (0.3 U/ml) to washed platelets made ristocetin-induced agglutination decline to 31.6% and 38.5% of control values, respectively. The extent of decline was positively correlated with the concentration of urokinase and plasmin. In addition, the platelet membrane glycoprotein Ib decreased to 76.4% of control value. With the addition of urokinase or plasmin to aprotinin-pretreated platelet-rich plasma or washed platelets, the changes in agglutination are not statistically significant and the decrement in glycoprotein Ib is much less marked. Further in vivo research revealed that cardiopulmonary bypass caused a decrease in plasma alpha 2-antiplasmin, indicating the fibrinolytic system activation. Meanwhile, ristocetin-induced agglutination decreased to 39.6% and platelet glycoprotein Ib decreased to 50% of preoperative values. However, with the administration of aprotinin, plasma alpha 2-antiplasmin during cardiopulmonary bypass did not change; platelet agglutination was improved, platelet glycoprotein Ib was preserved, and this consequently resulted in 46% lower blood loss after the operation. The results showed that fibrinolysis impaired platelet function, and this effect may be associated with the hydrolysis of glycoprotein Ib. Fibrinolytic activation occurred during cardiopulmonary bypass and contributed to postoperative platelet dysfunction to a great extent. Aprotinin may inhibit fibrinolysis during cardiopulmonary bypass and thus relieve the platelet damage and improve the postoperative hemostatic mechanism.

Aprotinin↗
PubMed1993

Kinetic study and modelling on L-arginine fermentation.

The batch fermentation of L-arginine using Corynebacterium crenatum L-arginine-producing mutant 971.1 was kinetically studied in a 2.6 L fermentor for the following purposes: kinetic classification of L-arginine fermentation by the comparison of the two-phases of specific growth rates; modelling of the L-arginine fermentation, and discussion about the effects of oxygen supply on the conversion rate of glucose to L-arginine, by comparing the fraction of glucose-consumption for L-arginine-formation alpha p and the fraction of glucose-consumption for cell-growth alpha x under different oxygen transfer coefficients kLa. The kinetic fermentative behavior of the strain 971.1 in L-arginine formation, which was related to the velocity and effectiveness of the metabolism of the cell, was mathematically analyzed.

Arginine↗
PubMed1993

[Studies of the homology of chromosomes between human being and rhesus monkey with chromosomal in situ suppression hybridization].

Chromosomal in situ suppression (CISS) hybridization of biotin-labeled DNA libraries for human chromosomes 1, 2 and 4 was used to investigate chromosome homology between human being and rhesus monkey. The results demonstrate that chromosome 1 in human being and rhesus monkey is homologous, of which the 1pter-->1q33 of rhesus monkey is highly homologous with a cognate region of chromosome 1 in human, while the 1q33-->1qter is relatively low; Chromosome 2 in human shows homology with the long arm of chromosome 13 as well as the long arm and the partial short arm of chromosome 9 in the rhesus, and chromosome 4 in human is identical to chromosome 2 in rhesus monkey. Combined with a comparative analysis of banding patterns of chromosomes, derivation relationships of chromosomes between man and the rhesus are discussed. Our present data provide a definitive proof that chromosomal rearrangements may be a major mechanism of chromosomal evolution in primates.

Animals↗
PubMed1992

Analysis of two gene regions involved in the expression of the imipenem-specific, outer membrane porin protein OprD of Pseudomonas aeruginosa.

A Tn501 mutant of Pseudomonas aeruginosa resistant to imipenem and lacking the imipenem-specific outer membrane porin protein OprD was isolated. The mutation could be complemented to imipenem susceptibility and OprD-sufficiency by a cloned 6-kb EcoRI-PstI fragment of DNA from the region of chromosome of the wild-type strain surrounding the site of Tn501 insertion. However, this fragment did not contain the oprD structural gene as judged by its inability to hybridize with an oligonucleotide corresponding to the N-terminal amino acid sequence of OprD. DNA sequencing of 3.9 kb of the region surrounding the Tn501 insertion site revealed three large open reading frames, one of which would be interrupted by the Tn501 insertion in the mutant. This latter open reading frame, named opdE (for putative regulator of oprD expression), predicted a hydrophobic protein of M(r) 41,592. Using the above-mentioned oligonucleotide, the oprD structural gene was cloned and expressed in Escherichia coli on a 2.1-kb Bam HI-KpnI fragment. DNA sequencing predicted a 420 amino acid mature OprD protein with a 23 amino acid signal sequence.

Bacterial Outer Membrane Proteins↗