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Biomedical subjects

G Chu

Publications and source records attributed to G Chu.

88 records · Page 5Linked to original sources
PubMed1983

The RBE of the leakage radiation from the Hiletron neutron therapy unit.

The RBE of the leakage radiation from the Hiletron 14.7 MeV neutron therapy unit has been measured using three sensitive biological systems in mice, which differ markedly in their radiobiological characteristics. These systems comprise type A spermatogonia and bone marrow stem cells, which are affected insignificantly by dose rate, and pigment abnormalities in hair follicles which are affected markedly by dose rate. For mice irradiated at 10 cm depth in a water phantom, the leakage radiation up to 40 cm from the beam axis was virtually as effective as the primary beam for the latter two biological systems, and for spermatogonia in mice when irradiated in air. At this distance, the total dose rate was about 0.2 cGy (rad) per minute (3% of that in the primary beam), and the gamma-ray component was about 70%. This equal effectiveness of the total dose for all three systems was considered fortuitous, and it implied high RBE values for equal effect with the small neutron component at far distances. Considering published data on RBE versus neutron energy, the evidence suggested either a positive interaction of neutron and gamma-ray components in killing bone marrow stem cells when the neutron component was less than 40% of the total dose, or an increased efficiency of neutrons when delivered at very low dose rates. However the components were additive in killing spermatogonia.

Air↗
PubMed1981

A gene chimaera of SV40 and mouse beta-globin is transcribed and properly spliced.

A gene chimaera of the first exon from simian virus 40 (SV40) sequences coding for T antigen placed upstream from the third exon from mouse beta-globin, and separated by the resultant new chimaeric intron, was cloned into a bacterial plasmid. When transfected into monkey cells, the gene chimaera was transcribed, polyadenylated and spliced using the donor splice site from SV40 and the acceptor splice site from mouse beta-globin. This result suggests that a donor site from one gene can be spliced to an acceptor site from another gene.

Antigens, Neoplasm↗
PubMed1981

SV40 DNA transfection of cells in suspension: analysis of efficiency of transcription and translation of T-antigen.

A modification of the Graham and Van der Eb (1974) DNA-calcium phosphate coprecipitation technique is shown to routinely transfect 15% of CV-1 cells with SV40 DNA. The transfection is done in suspension after detachment of cells by trypsin digestion. Transfection efficiency was measured by staining cells for the presence of SV40 T-antigen by indirect immunofluorescence and by assaying for the presence of SV40 early message by the Berk and Sharp (1978) technique.

Animals↗
PubMed1979

Reappraisal of prick test to tree and weed antigens.

Although 3+ or 4+ prick test reactions to olive tree or Russian thistle are valid, the RAST values to these antigens are significantly lower than those in patients with similar reactions to grass antigens, suggesting that nonimmunologic factors are partially responsible for the skin test reactions to the tree and weed antigens.

Antigens↗
PubMed1977

Three-dimensional imaging in the position camera using Fourier techniques.

A mathematical algorithm for three-dimensional reconstructions in the positron camera is described. Fouier techniques have been adapted for use in analysing the data from cameras with limited detector configuration. Noise instabilities from random fluctuations in the data are discussed and treated. The technique is tested on a computer-generated phantom and the results are presented. Ways of incorporating the effects of Compton scattering and detector response into the algorithm are discussed. It is concluded that the method is feasible and practical for obtaining accurate reconstructions.

Brain Neoplasms↗
PubMed1976

Correlation between protein kinase-mediated stimulation of calcium transport by cardiac sarcoplasmic reticulum and phosphorylation of a 22000 dalton protein.

Increases in protein kinase-catalyzed phosphorylation of a 22000 dalton protein correlated closely with increases in phosphate-facilitated calcium transport measured concurrently in canine cardiac sarcoplasmic reticulum under similar conditions in the presence of varying concentrations of bovine cardiac protein kinase. A correlation coefficient of 0.93 and a P value of less than 0.001 were obtained. Protein kinase-catalyzed phosphorylation of the 22000 dalton microsomal protein may mediate the abbreviation of systole seen in the mammalian heart in response to inotropic agents like catecholamines.

Animals↗
PubMedDate not supplied

Pulsed field electrophoresis in contour-clamped homogeneous electric fields for the resolution of DNA by size or topology.

The electrophoretic separation of DNA molecules can be controlled by the use of contour-clamped homogeneous electric fields (CHEF). This paper describes an improved CHEF apparatus with negligible distortion in the electric fields. When the electric field was periodically reoriented, DNA molecules up to 2 megabases were resolved in a highly uniform manner. Furthermore, when the field strength was changed with orientation, topological variations of conventional-sized DNA molecules were resolved.

DNA↗
PubMedDate not supplied

Cellular immunity delimits adenoviral gene therapy strategies for the treatment of neoplastic diseases.

BACKGROUND: Adenoviral gene therapy is a promising new approach for the treatment of neoplastic diseases. To design rational clinical trials and distinguish the effects of therapeutic transgene expression from those caused by viral infection alone, the immune response to the vector must be understood. In these experiments, we further define cellular immunity to recombinant adenovirus. METHODS: The immune response to hepatic adenoviral gene transfer was studied in infected mice by depleting T cells with an anti-CD3 antibody, measuring splenocyte cytokine production, determining the impact of transgene expression on inflammation, and assessing liver MHC protein expression. RESULTS: The cellular immune response to recombinant adenovirus is (1) averted by T lymphocyte depletion, (2) marked by a TH1 response with increased IL-2 production, (3) directed against both the transgene product and viral proteins, and (4) associated with increased hepatocyte MHC Class I expression. CONCLUSIONS: It is necessary to take into consideration the constraints imposed by the immunogenicity of recombinant adenovirus and its transient transgene expression in the clinical application of adenoviral gene transfer for the treatment of cancer.

Adenoviruses, Human↗
PubMedDate not supplied

Portal vein thrombosis associated with prolonged ingestion of oral contraceptive steroids.

The case is described of a 38 year old woman who developed severe right upper quadrant abdominal pain that was associated with partial portal vein occlusion, as confirmed by flow Doppler ultrasonography and dynamic contrast computed tomography. The patient was a cigarette smoker and had taken combined oestrogen/progestagen oral contraceptive steroids (OCS) continuously for 24 years. There were no other risk factors for portal vein thrombosis or for thromboembolic disease. Following anticoagulant therapy and discontinuation of OCS complete recovery occurred. The case is reported to draw attention to portal vein thrombosis as an extremely rare complication of OCS.

Adult↗
PubMedDate not supplied

Malabsorption and villous atrophy in patients receiving enteral feeding.

BACKGROUND: The purpose of this study was to assess the structure and function of the small intestine before and after enteral feeding given via a percutaneous feeding gastrostomy (PEG). It is not known whether this method of feeding provides a good luminal drive to the small intestine. METHODS: Studies were performed of patients at the time of PEG placement, in a cross-sectional group after a period of feeding and in a smaller longitudinal subgroup. Enteral feeds were adjusted in volume and caloric content for each patient. Duodenal biopsies were taken during endoscopy for quantitative morphometry, and lactulose-rhamnose permeability tests were performed during the next day. Duodenal fluid was cultured quantitatively in the first study, and disaccharidases determined in the second study. RESULTS: The first study of 15 patients, who had enteral feeding for a median (range) period of 13 (8 to 104) weeks, showed partial villous atrophy with normal crypt length, no increase in duodenal bacteriology, and abnormal lactulose-rhamnose sugar permeability due to rhamnose malabsorption. These changes were also present in 38 similar patients before enteral feeding. A second study before enteral feeding showed lowered maltase activity (24 patients), and similar intestinal permeability findings (22 patients). Twelve of these patients were followed longitudinally for 3 months of enteral feeding that maintained but did not improve nutrition, as assessed by body mass index and mid-arm muscle circumference, and there was no change in duodenal morphometry (11 patients), rhamnose malabsorption (4 patients), or disaccharidases (11 patients). CONCLUSIONS: These studies suggest villous atrophy was not due to an inflammatory enteropathy but resulted from a poor luminal "drive" associated with the enteral feeding. Enteral feeding maintained but did not improve nutrition status.

Atrophy↗