Biomedical subjects

G HALLIWELL

Publications and source records attributed to G HALLIWELL.

14 recordsLinked to original sources

PubMed1965

CATALYTIC DECOMPOSITION OF CELLULOSE UNDER BIOLOGICAL CONDITIONS.

1. The catalytic decomposition of undegraded cellulose in the form of cotton fibres is described with hydrogen peroxide at 0.4-0.04% (w/v) concentration in the presence of ferrous salts at pH3-5. 2. Complete solubilization of 5mg. of cotton fibres occurred in about 7 days in the presence of 0.4% hydrogen peroxide and 0.2mm-ferrous sulphate at the optimum pH4.2-4.3. 3. With 0.4% hydrogen peroxide the most rapid decomposition of cellulose was confined to ferrous sulphate concentrations of approx. 2-0.02mm. If the concentrations of the reagents were decreased in proportion extensive breakdown occurred but much more slowly. 4. In the primary stages of breakdown cotton fibres were disintegrated to very short fibres. These were subsequently solubilized, but there was little accumulation of soluble material. Organic matter was lost from solution as the reaction progressed. 5. Other naturally occurring cellulose-containing materials, such as grass, straw, hay and sawdust, were also disintegrated and solubilized by hydrogen peroxide and ferrous sulphate.

Catalysis↗

PubMed1965

HYDROLYSIS OF FIBROUS COTTON AND REPRECIPITATED CELLULOSE BY CELLULOLYTIC ENZYMES FROM SOIL MICRO-ORGANISMS.

1. The action of cell-free filtrates from Trichoderma koningii was examined on undegraded cellulose in the form of cotton fibres, on degraded cellulose in the form of cellulose powder reprecipitated from phosphoric acid and on the soluble cellulose derivative CM-cellulose. 2. The cell-free filtrates compare favourably with intact cellulolytic micro-organisms in producing complete solubilization of undegraded as well as of degraded types of cellulose. Enzymic solubilization of cotton fibres gives quantitative conversion into glucose. Cellobiase is present. 3. The early enzymic breakdown of cotton fibres is characterized by the formation of very short fibres that increase to a maximum and disappear gradually by conversion into glucose. Disintegration of cotton fibres to short fibres is assisted by shaking, and within 20hr. the enzyme converts a minor fraction (up to 16%) of substrate into soluble products and a major portion (80%) into insoluble short fibres. 4. Maximum enzymic activity on cotton fibres occurs at about pH5.0, measured by the formation of short fibres, and at about pH3.8 on reprecipitated cellulose, measured by solubilization of the substrate. 5. Gluconolactone, glucose and cellobiose fail to produce marked inhibition of the enzymic hydrolysis of cotton fibres to short fibres or of the solubilization of reprecipitated cellulose unless present in amounts comparable with or greater than the initial weight of these two forms of cellulose. 6. The heavy-metal ions Cu(2+), Hg(2+) and Fe(3+) at 2mm concentration give 80-100% decrease in the enzymic breakdown of cotton fibres, measured by the formation of short fibres. At the same concentration Hg(2+) and Fe(3+) but not Cu(2+) also produce 70-100% inhibition of the solubilization of reprecipitated cellulose. 7. The ability to hydrolyse cotton fibres to short fibres and CM-cellulose to sugars is completely lost after heating enzyme preparations for 10min. at 71 degrees .

Cellulose↗

PubMed1964

A COMPARISON OF IMIPRAMINE, CHLORPROMAZINE AND RELATED DRUGS IN VARIOUS TESTS INVOLVING AUTONOMIC FUNCTIONS AND ANTAGONISM OF RESERPINE.

Seven structurally-related compounds consisting of three antidepressant drugs (imipramine, desmethylimipramine and amitriptyline), three tranquillizing agents (promazine, chlorpromazine and chlorprothixene) and a hybrid, desmethylpromazine, have been examined in a series of tests involving autonomic functions and antagonism of reserpine. Activities of the compounds in antagonizing reserpine-induced ptosis in rabbits and prolongation of alcohol hypnosis in mice give good correlation with their clinical actions, whilst their activities in augmenting excitation of rats by amphetamine and yohimbine toxicity in mice, and in reversing reserpine-induced bradycardia in rats offer further evidence for drug-induced sensitization to adrenergic or tryptaminic mechanisms, which is not however specific for antidepressant agents. No evidence has been obtained to indicate that a central parasympatholytic action is an important component of the antidepressant activity of imipramine and related drugs.

Alcoholic Intoxication↗

PubMed1963