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Biomedical subjects

G Halliwell

Publications and source records attributed to G Halliwell.

11 recordsLinked to original sources
PubMed1997

Care maps across the continuum.

As hospital length of stay decreases and care shifts to the community, there is a need to develop approaches to ensure uniformity and continuity of care in patient groups. Care maps, multidisciplinary standards that outline the processes of care and expected outcomes within predetermined timeframes, can support a continuum of care from preadmission through hospital stay to discharge from community-based home care by clearly delineating standards across the entire episode of care. However, the development of successful care maps requires extensive collaboration, planning and evaluation.

Continuity of Patient Care↗
PubMed1983

Tioconazole, a new imidazole-antifungal agent for the treatment of dermatomycoses. Antifungal and pharmacologic properties.

Tioconazole is a new imidazole antifungal agent with broad-spectrum activity. Its in vitro activity against common dermal pathogens is generally better than miconazole by a factor of 2-8. This activity is paralleled by good topical efficacy in a guinea pig dermatomycosis model. Pharmacokinetic studies in animals have demonstrated minimal systemic exposure following dermal application. Acute general pharmacology studies have shown that the compound is well tolerated in animals and unlikely to produce side-effects in man.

Animals↗
PubMed1982

Saccharification of Complex Cellulosic Substrates by the Cellulase System from Clostridium thermocellum.

True cellulase activity has been demonstrated in cell-free preparations from the thermophilic anaerobe Clostridium thermocellum. Such activity depends upon the presence of Ca and a thiol-reducing agent of which dithiothreitol is the most promising. Under these conditions, native (cotton) and derived forms of cellulose (Avicel and filter paper) were all extensively solubilized at rates comparable with cellulase from Trichoderma reesei. Maximum activity of the Clostridium cellulase was displayed at 70 degrees C and at pH 5.7 and 6.1 on Avicel and carboxymethylcellulose, respectively. In the absence of substrate at temperatures up to 70 degrees C, carboxymethylcellulase was much more unstable than the Avicel-hydrolyzing activity.

Journal Article↗
PubMed1981

The action on cellulose and its derivatives of a purified 1,4-beta-glucanase from Trichoderma koningii.

The specific properties have been examined of the 1,4-beta-glucanase component of Trichoderma koningii that participates in an early and effective stage of random breakdown of native cellulose to short fibres. The enzyme was purified and freed from associated components of the cellulase complex (particularly beta-glucosidase) that interfere with, and complicate interpretation of, the action of such enzymes. Purification increased the specific activity 25-fold over culture filtrates; the enzyme hydrolysed CM-cellulose faster than the purified beta-glucosidase from the same organism hydrolysed any of its substrates (cellobiose or cellodextrins). The specificity of the glucanase was directed towards soluble derivatives of cellulose, CM-cellulose and cellodextrins, and not to insoluble cellulose or alpha-linked polymers. The approximate Km was 2.5 mg of CM-cellulose . ml-1 at 37 degrees C at the optimum pH, 5.5, where enzymic activity was maximal with 6--7 mg of CM-cellulose . ml-1 and inhibited by higher concentrations. The temperature optimum was 60 degrees C. The glucanase attacked larger cellodextrins (cellohexaose to cellotetraose, in that order) much more readily than smaller dextrins (cellobiose and cellotriose) and released a mixture of products, glucose up to cellopentaose, which was quantitatively determined after chromatography on charcoal. Similar examination of hydrolysates of the reduced cellodextrins showed clearly the high specificity of the enzyme for the central bond of its natural substrates (the cellodextrins), whatever their chain length, and indicated the nature of the enzyme as an endoglucanase. Outer bonds shared a weaker, but similar, susceptibility to enzymic cleavage. Transferase activity was absent and no larger dextrins than the initial substrate were formed.

Carboxymethylcellulose Sodium↗
PubMed1978

Affinity chromatography of the cellulase system of Trichoderma koningii.

A procedure involving affinity chromatography on cellulose was developed for separating enzymic components of the cellulase complex. Cellobiase, carboxymethylcellulase, component C2 and cellobiohydrolase are adsorbed with increasing tenacity, and released, as highly purified components, as the ionic strength of the eluent is decreased.

Cellulase↗
PubMed1977

Regulation of cellvibriocin activity.

Attempts were made to enhance the production of cellvibriocin, the bacteriocin produced by Cellvibrio sp. NCIB 9916, by a study of cultural conditions in agar (solid) media. In such media cellvibriocin was unstable: within 24 h all activity disappeared at 45 degrees C, 70% at 37 degrees C and more than 50% within 5 days at 5 degrees C. The temperature at which the producer strain was grown was critical, 25 degrees C being optimal. Cellvibriocin activity was markedly affected by the composition of the medium. Small amounts of metallic salts (Cu2+, Mn2+, Sr2+, Zn2+) and carboxylic acids of the citric acid cycle, especially citrate and tartrate, promoted its activity. Protease inhibitors, p-chloromercuribenzoic acid, N-ethyl maleimide and iodoacetate, enhanced cellvibriocin activity whereas a promoter of protease activity, casein hydrolysate, decreased activity.

Acids↗
PubMed1973

The nature and mode of action of the cellulolytic component C1 of Trichoderma koningii on native cellulose.

1. A purified cellulolytic component C(1) was isolated free from associated activities of the cellulase complex and shown to act as a beta-1,4-glucan cellobiohydrolase on both simple and complex forms of native cellulose. 2. The enzyme releases terminal cellobiose units from cellulose, its extent of action being determined principally by the product and by the nature of the substrate. 3. Component C(x) of the cellulase system is not required for the action of component C(1) (cellobiohydrolase). The enzyme synergizes extensively with cellobiase in extending the hydrolysis of native and of less-complex forms of cellulose to at least 70% with the liberation of glucose. 4. The cellobiohydrolase is relatively unstable, with an optimum at pH5 and a K(m) of 0.05mg/ml. The enzyme is inhibited by its product, from which it is released by cellobiase. 5. Of other compounds tested against the cellobiohydrolase the metal ions Cu(2+), Zn(2+), phenylmercuric and Fe(3+) are increasingly effective inhibitors. Glucose has no action at concentrations found inhibitory with cellobiose. 6. The relationship of the enzyme to the entire cellulase complex is discussed.

Acetobacter↗
PubMed1970

The formation of short fibres from native cellulose by components of Trichoderma koningii cellulase.

Cellulolytic enzyme components of culture filtrates of Trichoderma koningii were fractionated on ionic and non-ionic forms of Sephadex and on cellulose powder (Whatman) and examined for their ability to hydrolyse soluble carboxymethyl-cellulose, and to saccharify, solubilize and form short fibres from native undegraded cellulose of the type found in cotton. DEAE-Sephadex provided two CM-cellulase components and a C(1) component; the C(1) component acted weakly and solely on cotton, forming soluble products but not short fibres. The ability to form short fibres was confined almost wholly to one of the CM-cellulase components which completely degraded cotton, minimally to soluble products and extensively to short fibres. The latter action was unaffected by the presence of the other two components. The two CM-cellulase components solubilized cellulose synergistically whereas the short-fibre-forming component and C(1) component were inhibitory.

Cellulose↗
PubMed1966

Solubilization of native and derived forms of cellulose by cell-free microbial enzymes.

1. Cell-free enzymes from Myrothecium verrucaria and Trichoderma koningii hydrolyse native undegraded cellulose, as found in cotton fibres, in a random manner to short insoluble fibres and to minor amounts of soluble products. 2. Enzyme preparations from M. verrucaria fail to attack the short fibres whereas preparations from T. koningii solubilize them completely to sugars at an optimum pH4.2-4.6. 3. The mode of hydrolysis of cotton cellulose by preparations from T. koningii involves from the earliest stages the formation of reducing sugars, followed closely by the appearance of short fibres, until the insoluble and soluble products each constitute about 40-50% of the weight of the initial substrate. After this stage the quantity of sugars increases at the expense of the insoluble short fibres. 4. Depending upon the method of preparation, derived forms of cellulose may be hydrolysed more slowly, much more rapidly, or at the same rate as cotton fibres by enzyme preparations from T. koningii.

Bacteria↗