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G Cohen

Publications and source records attributed to G Cohen.

At least 379 records · Page 21Linked to original sources
PubMed1980

Partial purification and characterization of the high molecular weight latent collagenase from human leukocytes.

Two latent collagenases whose apparent molecular weights were ca. 150 000 and 60 000 have been detected in human leukocytes and the partial purification of the high molecular weight component was accomplished by the following steps: acetone precipitation, ammonium sulphate fractionation, gel filtration on Sephacryl S-200, chromatography on DEAE-Sepharose, and a final gel filtration on Sephacryl S-200. After activation by an activator extracted from human rheumatoid synovial fluid, the enzyme was able to cleave collagen into the classical 1/4 and 3/4 fragments, and was inhibited by chelating agents and other typical collagenase inhibitors.

Arthritis, Rheumatoid↗
PubMed1979

Chemical evidence for production of hydroxyl radicals during microsomal electron transfer.

Rat liver microsomes generate methane from dimethyl sulfoxide and ethylene from either methional or 2-keto-4-thiomethylbutyric acid during electron transfer initiated by reduced nicotinamide-adenine dinucleotide phosphate (NADPH). Hydrocarbon gas production is suppressed by hydroxyl radical scavenging agents. Azide, an inhibitor of catalase, augments the production of hydrocarbon gases. These observations constitute chemical evidence for the generation of hydroxyl radicals by microsomes.

Alcohols↗
PubMed1979

Effect of thiourea on microsomal oxidation of alcohols and associated microsomal functions.

Thiourea and diethylthiourea, two compounds which react with hydroxyl radicals, inhibited NADPH-dependent microsomal oxidation of ethanol and 1-butanol. Inhibition by both compounds was more effective in the presence of the catalase inhibitor, azide. Inhibition by thiourea was noncompetitive with respect to ethanol in the absence of azide but was competitive in the presence of azide. Urea, a compound which does not react with hydroxyl radicals or H2O2, was without effect. Thiourea had no effect on NADH- and NADH-cytochrome c reductase, NADPH oxidase, and NADH- and NADPH-dependent oxygen uptake. Thiourea inhibited the activities of aniline hydroxylase and aminopyrine demethylase. Thiourea, but no other hydroxyl radical scavengers, e.g., dimethyl sulfoxide, mannitol, and benzoate, reacted directly with H202 and decreased H2O2 accumulation in the presence of azide. Therefore the actions of thiourea are complex because it can react with both hydroxyl radicals and H2O2. Differences between the actions of thiourea and those previously reported for dimethyl sulfoxide, mannitol, and benzoate, e.g., effects on drug metabolism, effectiveness of inhibition in the absence of azide, or kinetics of the inhibition, probably reflect the fact that thiourea reacts directly with H2O2 whereas the other agents do not. The current results remain consistent with the concept that microsomal oxidation of alcohols involves interactions of the alcohols with hydroxyl radicals generated from microsomal electron transfer.

Aminopyrine N-Demethylase↗
PubMed1979

Comment on "Information processing in the cerebral hemispheres: selective activation and capacity limitations" by Hellige, Cox, and Litvac.

The attentional model of hemisphere differences proposed by Kinsbourne is reviewed, and some of the difficulties inherent in this model are pointed out. In particular, the difficulty of distinguishing shifts in the allocation of attention from changes of strategy is underlined, and the fact that the effect of imposing a concurrent memory load is uncertain, sometimes priming and sometimes depressing the performance of the loaded hemisphere, is seen as seriously limiting the predictive power of the model. Hellige, Cox, and Litvac attempted to clarify several aspects of Kinsbourne's theory. In their studies concurrent verbal loads produced complex and variable changes in the performance of both hemispheres. To explain these, they postulate a dual mechanism whereby general activation primes the performance of both hemispheres while selective activation acts to prime or to depress the performance of the left hemisphere. Although they succeeded in identifying some of the factors that govern the effects of selective activation, the effects of general activation are uncertain, so the overall outcome of concurrent memory loading is still difficult to predict.

Attention↗
PubMed1979

The use of contrast -- detail -- dose evaluation of image quality in a computed tomographic scanner.

Limiting-perception measurements of hole patterns in computed tomography reconstructions of a low-contrast phantom are used to generate contrast -- detail -- dose diagrams for various contrasts, hole diameters, dose, and system modulation transfer functions (MTF). These curves are then divided into MTF-dominated, transition, and noise-dominated regions. The low-contrast perceptibility and image noise are parameterized and compared. A limiting-perception factor is difined and is shown to be nearly independent of contrast, hole diameter, dose, and MTF in the noise-dominated region.

Data Display↗
PubMed1979

Contrast--detail--dose analysis of six different computed tomographic scanners.

Low-contrast visibility of various rotate-translate, rotating detector, and stationary detector computed tomogrphy (CT) scanners is measured at contrasts ranging from 0.3 to 3% using a phantom based on the partial volume of water and polystyrene. The results are plotted on log-log curves, as a function of entrance dose, to provide a family of contrast (C)--detail (d)--dose (D) visibility curves. The transition region, approximately 1 to 10% contrast, depends on modulation transfer function (MTF), contrast, and the dose (noise), while the noise region, less than or equal to 1% contrast, is independent of MTF. The slopes of the curves in the noise region are consistent with a value of -1, as opposed to a theoretically expected value of -3/2 for ideal CT noise. Relative dose efficiency of various scanners is examined by plotting CdD(1/2) versus contrast for both peak dose (Dp) and summation dose (D sigma). The rotating detector systems are shown to be, on the average (at 0.5% contrast), 3.4 (Dp) and 4 (D sigma) times more dose efficient than the stationary array system examined, and 2.4 (Dp) and 3.2 (D sigma) times more efficient than the rotate-translate units examined.

Data Display↗
PubMed1979

Complications of laparoscopic sterilization. Comparison of 2 methods.

A retrospective study of 5346 cases of laparoscopic sterilization with special reference to early and late complications was undertaken. In the 6-year period from 1972 to 1978, 846 patients were sterilized by the elasticized silicone-ring technique and 4500 patients were sterilized by the electrocautery method. The electrocautery method was complicated by electrical burns in 13 cases (0.29%); 3 of these patients required bowel resections. Mechanical complications occurred in 1.6% of the Silastic-ring cases, but none of the patients required additional surgery. The Silastic-ring patients had greater postoperative abdominal pain than the electrocautery patients, but it usually abated within 48 hours. There were 15 cases of postoperative pelvic infection in the electrocautery group, and none in the Silastic-ring group. Bleeding from the mesosalpinx occurred in both groups and occurred more often with coincident suction D&C. Technical failure to perform the sterilization procedure was principally related to previous abdominal surgery. A substantial number of patients complained of menstrual irregularity and/or dysmenorrhea following these sterilization procedures. The majority of women reported unchanged or improved sexual relations. Improvement in sexual relations was reported by significantly more patients in the Silastic-ring group than in the electrocautery group.

Burns, Electric↗
PubMed1979

Absorbed doses to patients and personnel from endoscopic retrograde cholangiopancreatographic (ERCP) examinations.

Radiation doses to the skin, bone marrow, and gonads were determined during endoscopic retrograde cholangiopancreatographic examinations. Average patient entrance doses were 7.5, 4.9, 17.5 and 2.7 rads to the abdomen, back, and left lateral and right lateral positions, respectively. Mean active bone marrow dose was 0.4 rads and average gonadal dose was 0.2 rads. Spot radiographs and fluoroscopy provided equal contributions to patient dose. Patient entrance dose was less than that from abdominal angiography, and comparable to that from a typical upper-gastrointestinal series. The pancreatic dose was comparable to that from a radionuclide scan. Dose to personnel was negligible.

Bone Marrow↗
PubMed1979

Digital radiography using a computed tomographic instrument.

A prototype computed radiography (CR) system was evaluated for its efficacy as an independent diagnostic modality. Preliminary measurements of high contrast resolution, low contrast perceptibility, and dose were obtained. Clinical examinations including skull, abdomen, liver, gallbladder, biliary system, spine, and extremities were performed as an adjunct to either computed tomography or CR. The data suggest that CR can be an effective diagnostic imaging modality by itself. Advantages over conventional radiography include high scatter rejection, low patient dose, wide dynamic range, and good low contrast sensitivity for large objects; disadvantages, its long exposure time and relatively poor high contrast spatial resolution.

Biliary Tract↗
PubMed1979

[Chronic polyarthritis: role of polymorphonuclear leukocytes in the destruction of pannus-free articular cartilage].

The synovial fluid (SF) of RA patients contains large amounts of PMN which are well equipped with neutral enzymes to degrade articular cartilage: elastase and cathepsin G, which both destroy proteoglycans and native collagen, as well as 2 types of collagenoases. Indirect evidence suggests that PMN might be important in the destruction of RA articular cartilage. In 19 SF of RA patients no free elastase or collagenase was found. Using immune histochemical methods, we observed that PMN and macrophages of SF contain both elastase and alpha 1-anti-trypsin and alpha 2-macroglobulin. Peripheral PMN - but not monocytes - contain elastase, however both types of cells lack alpha 1-antitrypsin and alpha 2-macroglobulin. Elastase is demonstratable in the superficial layer of pannus free RA articular cartilage. These findings suggest that neutral proteinases from PMN in RA SF are generally neutralized by physiologic inhibitors and removed by phagocytes. The enzyme-inhibitor interaction might be bypassed during "frustrated phagocytosis" so that enzymes like PMN elastase can damage RA articular cartilage.

Arthritis, Rheumatoid↗
PubMed1978

Isolation and characterization of a ColE1 plasmid containing the entire bio gene cluster of Escherichia coli K12.

ColE1amp plasmids carrying the entire bio gene cluster were constructed in vitro using ColE1amp as the cloning vehicle and a lambda transducing phage, lambdaatt2, as the source of bio DNA. Restriction endonuclease EcoRI digests of ColE1amp and lambdaatt2 DNA were joined by polynucleotide ligase and plasmids bearing the entire bio gene cluster were selected, after transformation, in bio deletion strains of E. coli. Recombinant DNA molecules contained one ColE1amp fragment (7.4 X 10(6) daltons) and one lambdaatt2 DNA fragment (5.4 X 10(6) daltons). Clones carrying ColE1 amp-bio plasmids produce elevated levels of biotin and biotin synthetase activity.

Biotin↗