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Biomedical subjects

L Dubois

Publications and source records attributed to L Dubois.

At least 37 records · Page 2Linked to original sources
PubMed1995

Synthetic routes to 4-amino-3-carboxy-beta-carboline derivatives: incidental formation of novel furo[3,4-c]-beta-carbolin-2-ones displaying high affinities for the benzodiazepine receptor.

The synthesis of the first 4-amino-3-carboxy-beta-carboline derivative (35) is described. This synthesis is based on ozonolysis of the 4-vinyl-beta-carboline-3-carboxamide 17 to give the 4-aldehyde 20 and potassium permanganate oxidation of the latter to the 4-carboxylic acid 34 followed by a DPPA-promoted Curtius rearrangement. During the course of these transformations, a number of furo[3,4-c]-beta-carbolin-2-ones, differing in substituents at the C-10 position, were formed. While these beta-carboline lactones (15,25,26,33) generally displayed good affinities for the central type benzodiazepine receptor in vitro (IC50's in the 10-50 nM range), one compound, 29, demonstrated an exceptionally high binding affinity (IC50 = 0.2 nM). Compound 29 was shown in electrophysiological and behavioral studies to act as a benzodiazepine receptor antagonist. The unusually high binding affinity of compound 29 corroborates the hypothesis that the benzodiazepine receptor preferentially recognizes the C-3 carbonyl function of 3-carboxy-beta-carbolines in an s-cis conformation (i.e., the carbonyl oxygen on the same side as the pyridinyl nitrogen).

Animals↗
PubMed1987

Effects of two novel inhibitors of 5-lipoxygenase, L-651,392 and L-651,896, in a guinea-pig model of epidermal hyperproliferation.

The effects of two novel and structurally different 5-lipoxygenase inhibitors, L-651,392 (4-bromo-2,7-dimethoxy-3H-phenothiazin-3-one) and L-651,896 (2,3-dihydro-6-(3-(2-hydroxymethyl)phenyl-2-propenyl)-5-benzo furanol), on epidermal proliferation were examined in the guinea-pig ear stimulated with the calcium ionophore A23187. Topical application of A23187 on the guinea-pig ear induced epidermal hyperproliferation which could be quantitated by tritiated-thymidine incorporation into DNA in the heat-separated epidermis. The ionophore-induced response was inhibited dose dependently by either L-651,392 or L-651,896 when the guinea-pigs were pretreated topically with these compounds. In separate experiments, it was demonstrated that A23187 induced a significant increase in the levels of immunoreactive-LTB4 in the guinea-pig ear which could be blocked by either inhibitors. It was suggested that L-651,392 and L-651,896 inhibited the ionophore-induced epidermal proliferation via their inhibitory action on the 5-lipoxygenase pathway of arachidonic acid metabolism.

Animals↗
PubMed1977

Agglutinins and lysins in the molluscan family Planorbidae: a survey of hemolymph, egg-masses, and albumen-gland extracts.

1. Thirty-one strains representing eight species and four genera of the molluscan family Planorbidae were surveyed for the presence of hemagglutinins and hemolysins. Extracts prepared from albumen-glands and egg-masses, as well as hemolymph, were assayed by a micro-hemagglutination technique in which human erythrocytes were used as receptors. 2. Hemagglutinins and hemolysins for human erythrocytes were not uniformly present in all members of the family and detection of these substances depended, in part, on the material tested. 3. Neither heating to 56 degrees C, dialysis, storage at -20 degrees C for up to a year, nor repeated freezing and thawing appeared to effect the agglutinating activity of egg or albumen-gland extracts. 4. Inhibition of the agglutinating activity of Helisoma hemolymph could be accomplished with N-Acetyl-D-Galactosamine, but this sugar had no effect on the activity of Biomphalaria agglutinins. 5. There is evidence to suggest that the source and nature of agglutinins from Helisoma and Biomphalaria species are different. 6. Lectins may be of some value in characterizing snail populations and as an aid in the taxonomic discrimination of species.

Agglutinins↗
PubMed1976

Characterization of an episode with elevated ozone concentrations.

A detailed analysis has been made of a seven day period in 1973, during which elevated ozone levels were observed at Ottawa. In addition to the ozone data, results are also presented for oxides of nitrogen, carbon monoxide, methane, total hydrocarbons and particulate matter. The particulates were analyzed for seven constituents, including the cations ammonium, calcium, sodium, potassium and lead and the anions sulfate and nitrate. Also measured were several other properties of the particulates, including the size distribution. It was found that none of the other gaseous pollutants showed any increase in concentration when high ozone levels were present. In contrast, the particulate matter did increase and several constituents, notably ammonium and sulfate, showed a dramatic rise. A comparison with ozone data from Toronto and upper New York state showed that the high ozone concentrations were widespread. A meteorological analysis showed that elevated ozone levels were associated with a Tropical air mass with a moderate southwesterly flow of air. Trajectory calculations were carried out to show the origin of the air over Ottawa before, during and after the period of increased ozone.

Air Movements↗
PubMed1975

Calibration of mercury vapor monitors by permeation.

The permeation system described provides constant concentrations of mercury in air. They can be selected at will and introduced into one or more of the instruments to be calibrated. The concentration of mercury in the permeation stream is simultaneously reocrded by a reference ultraviolet photometer.

Air Pollutants↗