Biomedical subjects
Publications and source records attributed to G Du.
Bubbles oscillating at resonance frequency dramatically enhance nonlinearity of a bubbly liquid. A second-order nonlinear wave equation taking account of bubble pulsation is solved. Numerical calculations based on the equation are compared favorably with experimental results. Possible biological significance of the highly nonlinear medium is also discussed.
Pheromone specificity in the Lepidoptera is encoded in protein components of the antennal sensillum lymph and dendritic membrane. In this paper, we highlight recent work on the molecular determinants of pheromone binding affinity of pheromone binding proteins (PBPs) of three genera. First, we describe new cDNA sequences for Lymantria dispar (Lymantriidae) and Agrotis segetum (Noctuidae). These data enrich the conclusions derived from our functional studies. Secondly, we indicate how preparation of multimilligram quantities of the recombinant PBP 'Apol-3' (originally from Antheraea polyphemus) has provided a platform (i) to determine the ligand binding sites using photoaffinity labeling, (ii) to conduct structural analysis by CD and NMR, and (iii) to measure binding affinities using a new binding assay. Thirdly, we describe the use of expression-cassette PCR technology to prepare two related PBPs from Antheraea perneyi to test binding affinities of naturally-occurring homologous PBPs. Our results support a model in which ligand specificity for chain length, double bond position, and terminal functionality is partially encoded in the PBPs. We propose that the final decoding is accomplished when the PBP-pheromone complex activates a G-protein coupled seven-transmembrane domain receptor that contains recognition sites for both the presented pheromone and the presenting PBP.
OBJECTIVE: To compare the upper gastrointestinal disease profiles of Helicobacter pylori-infected patients drawn from two distinct regions of China, one with a low incidence of gastric cancer (Guangzhou) and the other with a high incidence of gastric cancer (Lanzhou). The age-standardized prevalence of H. pylori within the populations of these two cities was similar (approximately 56%). In these patient groups, the prevalence of different gastrointestinal disease states and the occurrence and severity of gastritis, gastric atrophy, and intestinal metaplasia were compared. METHODS: This study was based on consecutive patients: 265 from Guangzhou and 275 from Lanzhou. The grading of gastritis and the detection of H. pylori was determined by histology using the "Sydney System". RESULTS: The ratio of cases of duodenal to gastric ulceration for the two cities was: Guangzhou 14:1 and Lanzhou 3:1. Gastric cancer was more prevalent in the patients from Lanzhou (9.8%) than from Guangzhou (3%). In nonulcer dyspepsia patients from Guangzhou, gastritis was predominantly antral, whereas, in Lanzhou, gastritis was predominantly uniform. The amount and severity of atrophy was significantly greater in Lanzhou compared with Guangzhou. CONCLUSIONS: The prevalence of atrophy, rather than age of acquisition and prevalence of H. pylori infection, appears to be a marker of the major upper gastrointestinal disease profiles of a region. Development of atrophy, although apparently related to H. pylori infection, may be a multifactorial condition. Differences in diet, as seen between Guangzhou and Lanzhou, may be important in this regard. Understanding the factors leading to the development of atrophy may enhance our understanding of processes leading to gastric malignancy.
The bacterially expressed recombinant pheromone binding protein (PBP) of Antheraea polyphemus was photoaffinity labeled with (6E,11Z)-[3H]hexadecadienyl diazoacetate, a photoactivatable analog of the naturally occurring acetate pheromone. Radiolabeled peptides were separated from an endoproteinase Lys-C digestion by HPLC and characterized by Edman degradation. The label was exclusively found in the Asp39-Lys58 fragment. Cleavage of this peptide (DDYVMTDRLAGCAINCLATK) with Arg-C gave a single radiolabeled peptide (DDYVMTDR), which was predicted to be alpha-helical. The adjoining LAGCAINCLATK fragment, which is highly conserved in PBP sequences, was predicted to be a hydrophobic beta-strand and has been proposed to be important in recognition of the alkadienyl chain. Edman degradation confirmed the location of the covalently attached ligand at Thr44 of the smaller hydrophilic peptide. In addition, the synthesis of the newly identified pheromone component (4E,9Z)-tetradecadienyl acetate and its photoaffinity analog, (4E,9Z)-[3H]tetradecadienyl diazoacetate, is also described. Mapping of PBP photoaffinity labeled by (4E,9Z)-[3H]14:Dza revealed that the hydrophobic region Asp21-Lys38 adjacent to the primary binding domain Asp39-Lys58 contained a second modification site. The 14-carbon odorant molecule thus had two binding positions within the recognition site, while only a single binding position was available to the 16-carbon pheromone.
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ELISA was used to detect anti-HCV antibody in 179 serum samples of patients with various types of liver diseases and 41 serum samples of blood recipients in Baise district of Guang Xi. The results showed that 17.9% of patients with various types of liver diseases and 31.7% of blood recipients were anti-HCV positive. Among patients with liver diseases, the anti-HCV positive rate was 4.3% (1/23) in acute hepatitis (AH), 12.8% (10/78) in chronic hepatitis (CH), 28.6% (12/42) in liver cirrhosis (LC) and 25.0% (9/36) in hepatocellular carcinoma (HCC). As liver diseases became chronic, the anti-HCV positive rate tended to rise. The anti-HCV positive rate in LC was significantly higher than that in AH or CH (P < 0.05). The anti-HCV positive rate in HCC was not significantly different from that in AH or CH (P > 0.05 or 0.1). It was found that the anti-HCV positive rate in HBsAg-negative patients was significantly higher than that in HBsAg-positive patients (P < 0.05). The anti-HCV positive rate in liver diseases was not related to ALT (P > 0.05). In blood recipients, the anti-HCV positive rate was closely related to the number of transfusion and the activity of ALT.
Theoretical models for calculating the on-axis acoustic streaming velocity generated by a continuous-wave (CW) and pulsed finite amplitude ultrasonic beams have been developed. Using these models, the on-axis streaming velocity is calculated for unfocused linear plane wave ultrasonic beams, focused linear Gaussian beams, and unfocused ultrasonic tonebursts of finite amplitude. The numerical results show that the on-axis streaming velocity is significantly enhanced by the nonlinear harmonic generation of finite-amplitude ultrasonic tonebursts.
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