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Biomedical subjects

G Cohen

Publications and source records attributed to G Cohen.

At least 343 records · Page 19Linked to original sources
PubMed1982

Evaluation of a digital subtraction angiography unit.

The operating characteristics of a digital subtraction angiography unit were evaluated. Measurements included image intensifier and system linearity, uniformity, quantum and system noise, and iodine contrast. Various approaches to noise measurement were analyzed and tested, leading to the following conclusions: the video level should be maximized; changes in signal-to-noise ratio (SNR) due to changes in x-ray exposure do not necessarily reflect changes in quantum SNR alone, due to dependence of video levels on x-ray exposure; an understanding of the separate contributions of quantum and video SNRs to the total SNR guides proper selection of variables to minimize patient dose and x-ray tube heat loading.

Angiography↗
PubMed1982

High pressure liquid chromatographic determination of mono- and disaccharides in presweetened cereals: Collaborative study.

A collaborative study was conducted using a modified AOAC method (sugars in chocolate) for the determination of fructose, glucose, sucrose, and maltose in presweetened cereals by high pressure liquid chromatography (HPLC). Eight samples consisting of 6 products were analyzed in duplicate by the HPLC method and the AOAC Lane-Eynon method. The AOAC method was modified to use water-alcohol (1 + 1) and Sep-Pak C18 cartridges for sample cleanup. The HPLC results indicate precision comparable to the lane-Eynon method and the chocolate method. The modified HPLC method has been adopted official first action.

Chromatography, High Pressure Liquid↗
PubMed1982

Scintigraphic detection of segmental bile-duct obstruction.

In a patient with acute obstructive jaundice, cholescintigraphy with technetium-99m-labeled iminodiacetic acid (HIDA) showed uniformly reduced uptake in the left lobe of the liver. Endoscopic retrograde cholangiopancreatography (ERCP) demonstrated cholelithiasis and obstruction of the distal hepatic duct. Surgery, and later a T-tube cholangiogram, confirmed the presence of numerous stones in the left intrahepatic and common hepatic ducts. The liver was free of tumor. Intrahepatic segmental ductal obstruction may produce a spectrum of patterns on hepatobiliary imaging ranging from reduced uptake to intrahepatic pooling.

Aged↗
PubMed1981

Construction and physical mapping of plasmids containing the MetA gene of Escherichia coli K-12.

Plasmids containing the metA gene of E. coli K-12 were constructed in vitro using pBR322 as the cloning vehicle and lambda metA transducing phage as the source of metA DNA. EcoRI digests of pBR322 and lambda metA20 were joined by ligase and plasmids carrying the metA gene were selected after transformation in a metA deletion strain. Recombinant DNA molecules contained one pBR322 fragment and one lambda metA20 fragment of 12.2 kb which was present in either of two possible orientations. Plasmids constructed by BamHI digestion of lambda metA2 contained a single bacterial DNA fragment of 5.8 kb inserted in the tet gene. Insertion of the metA fragment led to loss of resistance to tetracycline in one orientation and partial resistance in the opposite orientation.

Bacteriophage lambda↗
PubMed1981

Coupling of dopamine oxidation (monoamine oxidase activity) to glutathione oxidation via the generation of hydrogen peroxide in rat brain homogenates.

Homogenates of perfused rat brain generated oxidized glutathione from reduced glutathione during incubation with dopamine or serotonin. This activity was blocked by pargyline, a monoamine oxidase inhibitor, or by catalase, a scavenger of hydrogen peroxide. These results demonstrate formation of hydrogen peroxide by monoamine oxidase and the coupling of the peroxide to glutathione peroxidase activity. Oxidized glutathione was measured fluorometrically via the oxidation of NADPH by glutathione reductase. In the absence of added dopamine or serotonin, a much smaller amount of reduced glutathione was oxidized; this activity was blocked by catalase, but not by pargyline. Therefore, endogenous production of hydrogen peroxide, not linked to monoamine oxidase activity, was present. These results indicate that glutathione peroxidase (linked to hexose monophosphate shunt activity) can function to eliminate hydrogen peroxide generated by monoamine oxidase and other endogenous sources in aminergic neurons.

Animals↗