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Biomedical subjects

H Gu

Publications and source records attributed to H Gu.

At least 127 records · Page 7Linked to original sources
PubMed1997

Partitioning a vocabulary's IS-A hierarchy into trees.

Controlled medical vocabularies are useful in application areas such as medical information-systems and decision-support. However, such vocabularies are large and complex, and working with them can be daunting. It is important to provide a means for orienting users to the vocabulary's contents. This paper introduces a methodology for partitioning a vocabulary into small, meaningful pieces. The partitioning is done with respect to the vocabulary's IS-A hierarchy. The methodology, based on a set of rules for refining the IS-A hierarchy, is a process carried out by a user in conjunction with the computer. The methodology is demonstrated on a complex portion of a vocabulary.

Classification↗
PubMed1997

[Observation of chromosome aberration and micronucleus formation in peripheral blood lymphocytes among cigarette smokers].

Using two interrelated observation indices--chromosomal aberration and micronucleus analysis in peripheral blood lymphocytes to reflect damages of genetic material, were used to observe the status of genetic material damage in male smokers at the same time. The results showed that there were significant increases in hyperpolid cell rate, chromatid and chromosome aberration rates, total aberant cell rate and frequency of micronucleated cells as well as micronucleus in smoking group when compared to non-smoking group. This findings showed that cigarette smoking is one of the important mutagenic factors which caused damage to human genetic materials.

Adult↗
PubMed1997

[No point mutation of the 2.8 kb EcORI fragment of the nasopharyngeal carcinoma transforming gene TX in nasopharyngeal carcinoma].

We have previously cloned a nasopharyngeal carcinoma transforming gene from human nasopharyngeal carcinoma cell line CNE-2 using mouse JB6 cell line as the recipient cells. This transforming gene, designated Tx, exhibits moderate transforming activity upon transfection into JB6 cells. Several lines of evidence indicate that the 2.8 kb EcoRI fragment which lies in the middle of the Tx gene is responsible for the transforming activity. The sequence of the 2.8 kb EcoRI fragment was determined, which showed striking homology with the human immunoglobulin light chain C region gene. Using the modified polymerase chain reaction-single strand conformation polymorphism analysis (PCR-SSCP) silver staining technique, we studied the possible point mutations of the nasopharyngeal carcinoma gene Tx in nasopharyngeal carcinoma. No mobility shift was detected in eleven paired cases of nasopharyngeal carcinoma biopsies suggesting that in most cases of nasopharyngeal carcinoma, the Tx gene is not activated via a mode of point mutation. Taken together with the previously obtained results we have found that the Tx gene is not activated by gene rearrangement or gene amplification. Therefore, we consider that the Tx gene may have been activated by its interaction with other regulatory factors.

Carcinoma, Squamous Cell↗
PubMed1996

H-ras transfection of the rat kidney cell line NRK-52E results in increased induction of c-fos, c-jun and hsp70 following sulofenur treatment.

The effect of the antineoplastic drug sulofenur on the induction of the immediate-early genes (IEG) c-fos and c-jun and the stress gene hsp70 was compared in the rat kidney epithelial-like cell line NRK-52E and a derivative H-ras-transfected (H/1.2NRK-52E) cell line. Fold induction for each gene after sulofenur (500 microM) treatment was greater in H/1.2NRK-52E. The maximum increases for NRK-2E and H/1.2NRK-52E were as follows: c-fos, approximately 10-fold and approximately 18-fold; c-jun, approximately 2.5-fold and approximately 3.6-fold; hsp70, approximately 13-fold and approximately 30-fold. In cells loaded with EGTA/AM or treated in low or no Ca2+ HBSS, c-fos induction was reduced similarly in both cell types. However, inhibition of protein kinases with staurosporin and calphostin C reduced c-fos by 80% in NRK-52E but by only 10-20% in H/1.2NRK.52E. These results indicate that sulofenur-induced IEG elevation is Ca(2+)-dependent and that the requirement for protein kinase C activation is bypassed in H-ras-transfected cells.

Animals↗
PubMed1996

Rearrangement-enhancing element upstream of the mouse immunoglobulin kappa chain J cluster.

Transcriptional regulatory elements have been shown to be necessary but not sufficient for the developmental regulation of immunoglobulin gene rearrangement in mouse precursor B cells. In the chicken lambda light chain locus, additional elements in the V-J intervening sequence are involved in negative and positive regulation of rearrangement. Here, mutation of the mouse homolog of a chicken element, located in the V(K)-J(K) intervening sequence upstream of the J(K) cluster, was shown to significantly decrease rearrangement. This cis-acting recombination-enhancing element affects the rearrangement process without being involved in regulating transcription.

Alleles↗
PubMed1996

Requirement of mammalian DNA polymerase-beta in base-excision repair.

Synthesis of DNA by DNA polymerase-beta is distributive on single-stranded DNA templates, but short DNA gaps with a 5' PO4 in the gap are filled processively to completion. In vitro studies have suggested a role of beta-polymerase in different types of DNA repair. However, the significance of these studies to the in vivo role of beta-polymerase has remained unclear. Because genetic studies are essential for determining the physiological role of a gene, we established embryonic fibroblast cell lines homozygous for a deletion mutation in the gene encoding DNA polymerase-beta. Extracts from these cell lines were found to be defective in uracil-initiated base-excision repair. The beta-polymerase-deleted cells are normal in viability and growth characteristics, although they exhibit increased sensitivity to monofunctional DNA-alkylating agents, but not to other DNA-damaging agents. Both the deficiency in base-excision repair and hypersensitivity to DNA-alkylating agents are rescued following stable transfection with a wild-type beta-polymerase minitransgene. These studies demonstrate that beta-polymerase functions specifically in base-excision repair in vivo.

Animals↗
PubMed1996

Effect of acidosis on contraction, intracellular pH and calcium in the rabbit mesenteric small artery.

The purpose of the present study was to determine the effect of various types of acidosis on vessel diameter, intracellular pH (pHi), and calcium concentration ([Ca2+]i) in a cannulated preparation of the mesenteric arteriole of the rabbit. The effect of acidosis on vessel contraction was also studied in the wire-mounted preparation. In the cannulated preparation, pre-contracted by noradrenaline, hypercapnia caused vasoconstriction and increases in [Ca2+]i. In the wire-mounted preparation pre-contracted by either noradrenaline or high KCl, hypercapnia caused a transient vasoconstriction. In contrast, in the cannulated preparation pre-contracted by high KCl, hypercapnia caused a transient vasorelaxation and decreases in [Ca2+]i. Intracellular acidosis, induced by a NH4Cl prepulse, caused vasoconstriction and increases in [Ca2+]i even in the cannulated preparation pre-contracted by high KCl. The decrease in pHi during hypercapnia was similar to that observed after NH4Cl withdrawal. These data suggest that: (1) the effect of acidosis on vascular tone and [Ca2+]i is different depending upon the type of preparation and the mode of pre-activation, and (2) [Ca2+]i may, at least partly, regulate vascular contraction and relaxation during acidosis.

Acidosis↗
PubMed1996

Experimental study on the early efficacy of excimer laser with adjunctive balloon angioplasty in dog's femoral artery.

The effect of domestically-manufactured excimer laser with adjunctive balloon angioplasty in achieving revascularization and reduction of residual stenosis was assessed. 20 femoral arteries with thrombosis and occlusion from 12 dogs were subject to angiography. At first excimer laser angioplasty was done followed by balloon angioplasty. The diameter and residual stenosis of revascularized vessel were measured. The result showed that 17 out of 20 vessels (85%) were revascularized. The diameter of revascularized vessel by excimer laser were 1.22 +/- 0.14 mm, while residual stenoses were 54% +/- 5%. After adjunctive balloon angioplasty the diameter and residual stenoses were 2.04 +/- 0.16 mm and 20% +/- 7% respectively (P < 0.05 and P < 0.01). Complication in form of vasoperforation occurred in 3/20 vessels (15%). It is concluded that China- manufactured excimer laser angioplasty is effective when used for revascularization. While the reduction of narrowing and residual stenoses was enhanced after adjunction of balloon angioplasty. This method can be employed in treating peripheral occlusive disease effectively and safely.

Angioplasty, Balloon, Laser-Assisted↗
PubMed1996

Characterization and localization of adrenal nicotinic acetylcholine receptors: evidence that mAb35-nicotinic receptors are the principal receptors mediating adrenal catecholamine secretion.

Adrenal chromaffin cells contain at least two subtypes of nicotinic acetylcholine receptors (nAChRs). These studies were designed to identify and characterize the subtype of nAChR mediating adrenal catecholamine release using the monoclonal antibody mAb35, which recognizes the alpha-subunit of muscle nAChRs and cross-reacts with some neuronal nAChRs. Immunocytochemical studies demonstrated that mAb35 interacts with specific sites on cultured chromaffin cells. Pretreatment with mAb35 reduced nAChR-stimulated catecholamine release (IC50 of approximately 10nM). mAb35 had no effects on release stimulated through non-nAChR mechanisms. Unlike agonist-induced nAChR desensitization, the mAb35-induced reduction in nAChR-mediated secretion developed slowly. Although not immediately reversible, nAChR-stimulated release recovered after mAB35 removal. However, unlike recovery from agonist pretreatment, recovery from mAb35 pretreatment was relatively slow and was par tially blocked by vinblastine. Hybridization of adrenal chromaffin RNA with a rat alpha3 cDNA revealed two strong bands and two fainter bands: two higher-molecular-weight bands, 6.9 and 8.5 kb; a strong band of 3.2 kb; and a lower amount of 2.3kb RNA. With recovery of nAChR function after agonist or mAb35 treatment, no significant effects on alpha 3 subunit mRNA levels were seen. In summary, these studies demonstrate the presence of mAb35-nAChRs on adrenal chromaffin cells and provide evidence that these receptors represent the major population that regulates secretory events in adrenal chromaffin cells.

Adrenal Glands↗
PubMed1996

Phospholipase D is activated by G protein and not by calcium ions in vascular smooth muscle.

We assessed the sensitivity of phospholipase D (PLD) activity in vascular smooth muscle to cytosolic Ca2+ by increasing cytosolic Ca2+ levels independently of agonist stimulation. When rat tail artery was preloaded with the Ca2+ indicator fluo 3 pentaacetoxymethyl ester, the addition of high extracellular K+, caffeine, or norepinephrine rapidly enhanced cytosolic Ca2+ levels. Neither increased extracellular K+ nor caffeine addition increased phosphatidylethanol production, indicating that cytosolic Ca2+ elevation alone did not stimulate PLD. In contrast, norepinephrine stimulated phosphatidylethanol production in this tissue. In strips of tail artery permeabilized with alpha-toxin and incubated in solutions containing free Ca2+ concentrations observed during physiological stimulation (pCa 6.4), PLD was not stimulated, whereas incubation with guanosine 5'-O-(3-thiotriphosphate) at pCa 7.0 activated this enzyme. Aluminum fluoride (AlF4-) stimulated PLD, and this activity was insensitive to pertussis toxin after stimulation by either norepinephrine or AlF4-. These results indicate that PLD in vascular smooth muscle is activated by norepinephrine via stimulation of a pertussis toxin-insensitive G protein and not via an increase in intracellular Ca2+ levels.

Animals↗
PubMed1996

Utilizing OODB schema modeling for vocabulary management.

Comprehension of complex controlled vocabularies is often difficult. We present a method, facilitated by an object-oriented database, for depicting such a vocabulary (the Medical Entities Dictionary (MED) from the Columbia-Presbyterian Medical Center) in a schematic way which uses a sparse inheritance network of area classes. The resulting Object Oriented Health Vocabulary repository (OOHVR) allows visualization of the 43,000 MED concepts as 90 area classes. This view has provided valuable information to those responsible with maintaining the MED. As a result, the MED organization has been improved and some previously-unrecognized errors and inconsistencies have been removed. We believe that this schematic approach allows improved comprehension of the gestalt of large controlled medical vocabulary.

Classification↗
PubMed1996

[Structure analysis of a DNA fragment containing strong promoter activity from Streptomyces mycarofaciens 1748].

A HindIII-HindIII 2.0kb DNA fragment containing promoter activity has been cloned from medicamycin producing strain (S. mycarofaciens 1748), using promoter -probe plasmid vector pIJ486. Transformants of recombinant plasmid p4H2 containing this fragment were resistant to Km in the level above 500 micrograms/ml in MM medium. The result of subcloning deletion analysis indicated that different part of deletion of this fragment would show various extent of effect on the promoter activity. A rather complicated transcriptional regulatory mechanism was suggested. DNA sequence analysis revealed that this fragment consisted of 1984 nucleotides with 47.7% of G+C content. No typical ORF of Streptomyces gene was found. Certain regions showed some homologies with promoters of Streptomyces genes. In 520-570bp region, a sequence similar to the upstream activator sequence (UAS) of E.coli tRNA was discovered. This implied that a possible "enhancer" element was involved in Streptomyces gene transcription.

Anti-Bacterial Agents↗
PubMed1996

Increase of the expression of midecamycin 4"-hydroxyl propionyltransferase gene (mpt) by a promoter-like fragment from the midecamycin producing strain.

The promoter region of the midecamycin 4"-hydroxyl propionyltransferase gene (mpt) gene was reconstructed by PCR, and ligated with a fragment from the midecamycin producing strain (Streptomyces mycarofaciens var. 68) which contained fairly strong promoter activity (PLF). Recombinant plasmids pCHFPE2 (promoter region of mpt was reconstructed by combining the PLF in the upstream of its own promoter) and pCHFPE3 (the promoter of mpt was replaced by PLF) were obtained. The extent of expression of mpt was measured according to the amount of propionylspiramycin bioconverted from exogenous spiramycin by transformants of S. lividans TK24 containing pCHFPE2 and pCHFPE3. The results showed that the PLF could increase the expression of mpt in S. lividans TK24 up to 89.02% and 58.53%, respectively, and also enhance the expression in the industrial spiramycin producing strain S. spiramyceticus to a great extent.

Acyltransferases↗
PubMed1996

A clinical study on severe hydroa vacciniforme.

OBJECTIVE: To describe a severe type of hydroa vacciniforme (HV) in order to provide basis for treatment and prevention of this disease. METHODS: Nine cases of HV were collected in our outpatient department, and clinical and laboratory examinations were performed. RESULTS: All the cases had erythemas, papules, bullae, erosions or ulcers on exposed sites, with recurrences, gradually resulting in deformation. Five patients suffered from hand deformation manifesting rigidity, flexor tetanus, or malposition of the first, second and third interphalangeal joints of hands. Two of the above mentioned patients manifested partial bone absorption of fingers. Five patients showed partial defect of auricle. Two patients showed saddle nose, and partial absorption of nasal cartilage. One patient displayed cicatricial contracture of lower lip, with incisor extrusion. Four patients showed opacity of cornea. Through laboratory examinations, porphyrinopathies were excluded. Phototests showed increased sensitivity to ultraviolet-A radiation (UVA). CONCLUSIONS: Based on the clinical features and laboratory examinations, these patients were diagnosed as having severe HV. It is believed that this condition belongs to a disease spectrum induced by ultraviolet light. Our analysis suggests that for children with severe type of HV, preventive measures and therapeutic agents should be taken as soon as possible in order to avoid deterioration of the disease and malformations.

Adolescent↗
PubMed1996

[Inferior mesocaval shunt].

The results of inferior mesenteric vein-inferior vena cava shunt coupled with splenectomy and gastroesophageal devascularization in 16 patients with cirrhotic portal hypertention were reviewed. The mean diameter of the shunt stoma was 6.46 +/- 0.78 mm, and the portal pressure decreased from 4.25 +/- 0.54 kPa to 3.39 +/- 0.41 kPa. Variceal bleeding stopped in all 16 patients with no severe postoperative complications. This procedure should preserve satisfactory portal perfusion to the liver, and technically is easier than other shunt procedures.

Adult↗
PubMed1995

Dielectric study of the cooperative order-disorder transition in aqueous solutions of schizophyllan, a triple-helical polysaccharide.

Schizophyllan exists in aqueous solution as a triple helix, which is intact at room temperature. Its aqueous solution forms some ordered structure at low temperatures but undergoes a sharp transition to a disordered structure as the temperature is raised. The transition temperature Tc is about 7 and 18 degrees C for H2O and D2O solutions, respectively. This transition was followed by time-domain reflectometry to investigate dynamic aspects of the transition. In addition to a major peak around 10 GHz, the dielectric dispersion curve of a 20 wt % schizophyllan in D2O exhibited a small peak around 100 MHz below Tc and around 10 MHz above Tc. The major peak is due to bulk water, whereas the 100 MHz peak is assigned to "bound" or "structured" water, and that around 10 MHz to side-chain glucose residues. However, unlike usual bound water reported for biopolymer solutions, this "structured" water disappears abruptly when the temperature becomes close to Tc without accompanying a conformational transition of the main chain. The above assignment is consistent with the structure of the ordered phase derived from previous static data that it consists of side-chain glucose residues along with nearby water molecules surrounding the helix core that are interacting with each other loosely through hydrogen bonds, and spreads radially only a layer of one or two water molecules but a long distance along the helix axis.

Carbohydrate Conformation↗