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Biomedical subjects

J N Brown

Publications and source records attributed to J N Brown.

16 recordsLinked to original sources
PubMed1979

Potential radiosensitizing agents. Dinitroimidazoles.

New compounds of the nitroimidazole series have been synthesized as radiosensitizers which selectively sensitize hypoxic cells to the lethal effect of radiation. The reaction of 2,4(5)-dinitroimidazole (2) with chloroethanol or hydrochloric acid yielded 4(5)-nitro-5(4)-chloroimidazole (3), which upon reaction with ethylene oxide yielded the 4-nitro-5-chloroimidazole-1-ethanol (6). Reaction of 2 with ethylene oxide resulted in a mixture of two compounds, the 2,4-dinitroimidazole-1-ethanol (4) and 2,3-dihydro-5-nitroimidazo[2,1-b]oxazole (5). The structure of the new heterocyclic compound 5 was confirmed by 1H NMR, mass spectrum, and X-ray crystallography. These agents were tested for their ability to sensitize hypoxic Escherichia coli cells to killing by ionizing radiation. Compound 4 was found to be the most active agent of this series of compounds.

Chemical Phenomena↗
PubMed1979

Peptide--water association in peptide crystals.

The structures of 37 peptide crystals, containing 78 water-peptide hydrogen bonds and 77 other hydrogen bonds involving water, were surveyed to identify the geometry of peptide backbone hydration. In the sample, hydration of peptide carbonyl occurred more frequently than hydration of peptide N--H. The most probable value of the C'=O ... O water angle was near 138 degrees, considerably greater than the 120 degrees to the axis of a lone electron pair on the carbonyl oxygen. Associated water oxygens tended to be in the plane of the peptide bond, bui--H and Ci+1=O atoms, was common in glycine-containing cyclic hexapeptides. The distribution of angles between two hydrogen bonds at a single water molecule, as defined by the three nonhydrogen atoms involved, was centered near the tetrahedral angle.

Amino Acid Sequence↗
PubMed1977

Tricarboxylic acid cycle enzyme activities in adult Schistosoma mansoni and Schistosoma japonicum.

Reduced tricarboxylic acid cycle enzyme activities were found in paired adult Schistosoma mansoni and S. japonicum in comparison to those reported for S. mansoni cercariae (Coles, 1973). Succinate dehydrogenase activity, which has not been previously reported for either adult blood fluke, is more than twice as great in paired adult S. japonicum as in paired adult S. mansoni, but the activity is low in both species of adult worms. The similar low levels of tricarboxylic acid cycle enzyme activities which occur in adult S. mansoni and S. japonicum further substantiate the fact that anaerobic glycolysis is the major energy source in adults of both species.

Animals↗
PubMed1977

Schistosoma mansoni and Schistosoma japonicum: comparison of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activities in adults.

Glucose-6-phosphate dehydrogenase activity in paired adult Schistosoma mansoni is about twice as great as in paired adult Schistosoma japonicum. 2. 6-phosphogluconate dehydrogenase activity accounts for 25.8% of the measured production of reduced nicotinamide adenine dinucleotide phosphate (NADPH) in S. japonicum but only 8.6% of the measured production of NADPH in S. mansoni. 3. These data suggest a species difference in 6-phosphogluconate metabolism.

Animals↗
PubMed1977

A simple low-cost critical point dryer with continuous flow dehydration attachment.

A simple low-cost critical point dryer with continuous flow dehydration attachment is described. By using the critical point pressure chamber for all fluid exchanges, loss of material and air-drying artefacts due to specimen handling are reduced. An operating schedule that allows the optimum path around the critical point process to be followed is proposed.

Cells, Cultured↗
PubMed1977

Inhibition of key glycolytic enzymes from rabbit kidney medulla by free fatty acids in vitro.

In vitro incubation of key glycolytic enzymes in supernatant fluids from rabbit kidney medulla with increasing concentrations of sodium laurate resulted in progressive inhibition of hexokinase, phosphofructokinase and pyruvate kinase. A corresponding reduction in the production of lactate from glucose was also observed. The possible effects of these enzyme inhibitions on the naturesis observed during fasting are discussed.

Animals↗
PubMed1975

The avian erythrocyte: a study of fixation for electron microscopy.

The quality of ultrastructural preservation of the avian erythrocyte achieved using various fixation techniques is evaluated. Different combinations of initial fixatives, buffers and post-fixation procedures were tested as well as variations in fixative osmolarity, pH and temperature. Of the commonly used initial fixatives (glutaraldehyde, acrolein and formaldehyde), 2% glutaraldehyde, alone in a slightly hypertonic buffer containing divalent ions, produced optimum erythrocyte preservation. The osmolarity was balanced using a non-electrolyte such as a sucrose. The addition of 12% hexylene glycol to the buffer solutions also improves erythrocyte preservation, as evidenced by the increased stability of the marginal microtubules, microfilaments and proteinaceous material. The use of Spurr low-viscosity epoxy resin enables the cells to be collected using low gravitational centrifugation.

Acrolein↗