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Biomedical subjects

E M Scott

Publications and source records attributed to E M Scott.

At least 91 records · Page 5Linked to original sources
PubMed1985

Methemoglobin reductase activity in fish erythrocytes.

NADH-methemoglobin reductase activity of erythrocytes from the coho salmon, Oncorhynchus kisutch, sockeye salmon, Oncorhynchus nerka, and the rainbow trout, Salmo gairdneri exhibited a major band of activity that resembled the human enzyme in electrophoretic mobility. No polymorphism was found in 35 samples from rainbow trout, 4 samples from Dolly Varden, 29 samples from sockeye salmon, and 24 samples from coho salmon. All samples differed from the human enzyme in that they appeared to be membrane-bound and required the presence of a detergent, Triton X-100, for solubilization. Rainbow trout and coho salmon enzymatic activity is greater than the human enzyme activity at 15 degrees C.

Animals↗
PubMed1985

Ultrastructure of protoplasts from mycelium and microconidia of Trichophyton mentagrophytes.

Protoplast formation from mycelium and microconidia of Trichophyton mentagrophytes was achieved with Novozym 234. Pretreatment procedures with dithiothreitol or urea mercaptoethanol sodium lauryl sulphate before digestion with Novozym 234 greatly reduced protoplast yield from mycelium. Snail gut enzyme did not protoplasts in good yield. Scanning electron microscopy of mycelium protoplasts showed the acquired spherical shape. The plasma membrane appeared finely granular although remnants of cell wall could sometimes be observed. Transmission electron microscopy showed the cell interior of these protoplasts was plasmolysed. Microconidia treated with Novozym 234 displayed a range of cell wall digestion, with intact protoplasts showing distinct cytoplasmic organelles.

Enzymes↗
PubMed1985

Inhibition of hyphal development in Trichophyton mentagrophytes arthroconidia by ketoconazole and miconazole.

In the presence of 0.5 mg/l ketoconazole and miconazole, arthroconidia from three isolates of Trichophyton mentagrophytes produced germ tubes, which continued to grow for 12 h before further elongation ceased. Lower concentrations reduced the rate of elongation, but did not halt the process. Higher concentrations had no greater effect than 0.5 mg/l. The inhibitory effect of ketoconazole was independent of time of addition of drug during the first six hours of germination. Ketoconazole inhibition was reversible after 12 h contact, whereas miconazole inhibition was not. Morphological effects of drug treatment were investigated by scanning electron microscopy. In the absence of imidazoles, hyphae were straight and regular; ketoconazole treated hyphae were short, irregular and branching; miconazole treatment produced extensive debris and spores forming within the hyphae were visible.

Ergosterol↗
PubMed1985

Effects of aqueous and alcoholic povidone-iodine on spores of Bacillus subtilis.

Spores of Bacillus subtilis NCTC 10073 were examined for susceptibility to two proprietary brands of povidone-iodine: an aqueous solution, Betadine and an alcoholic solution, Videne. Spores were converted to ion-exchange (Ca, H) and coat-defective (SLS-, UME-, UMS-, UDT- and UDS-treated) forms. The resistance of these to povidone-iodine was compared and related to uptake. Effects on spore protoplasts and cortex in relation to hexosamine release were also examined. The degree of spore penetration and site of action of povidone-iodine is discussed.

Bacillus subtilis↗
PubMed1985

Growth of microorganisms in total parenteral nutrition mixtures and related clinical observations.

The effect of lipid addition to TPN (Total Parenteral Nutrition) solutions on microbial growth was investigated. Staphylococcus epidermidis, which failed to grow or grew poorly in the absence of lipid, reached greater than 10(4) cfu/ml (colony forming units per ml), from an initial inoculum of approximately 50 cfu/ml after 24 h when lipid was added. Candida albicans grew more slowly in the presence of lipid, but nevertheless reached 10(4) cfu/ml after 40 h incubation. Klebsiella aerogenes grew readily in all solutions, whereas Escherichia coli failed to grow in any solution. Growth of S. epidermidis and K. aerogenes was improved when the inoculum consisted of starved cells; however, growth of starved cells of C. albicans lagged behind that of unstarved cells. The ability of S. epidermidis to grow in lipid-containing TPN mixtures is particularly important, since this organism is frequently associated with sepsis. In an infant surgical unit, where TPN is under the care of a nutrition team, samples of TPN fluids and giving sets were examined for microbiological contamination at the end of the 24 h administration period. Contamination was found in eight of the 98 systems examined from eight patients. The organisms were identified as coagulase-negative staphylococci and diphtheroids.

Bacteria↗
PubMed1984

The effect of imidazoles on germination of arthrospores and microconidia of Trichophyton mentagrophytes.

The effects of imidazole antifungal drugs on germination of Trichophyton mentagrophytes microconidia and arthrospores were investigated. A Coulter Counter was used to estimate spore swelling and microscopy to assess germ-tube formation. Both spore forms germinated in SLM, pH 6, at 32 degrees C and these conditions were used as a control. The inhibition of spore germination by imidazoles was concentration dependent and required higher drug levels than MICs. There was good correlation between reduction in swelling and inhibition of germ-tube formation. In order to produce greater than 90% reduction of germ-tube formation higher concentrations of imidazole were necessary for arthrospores than for microconidia. There was no clear difference in potency of imidazoles except for ketoconazole which was markedly less effective. No increase in sensitivity of microconidia to miconazole was observed with time of addition during the initial 3 h of germination. Although the inhibitory effect of miconazole on swelling of micronidia was partially reduced in the presence of Mg++, germ-tube formation was not altered.

Clotrimazole↗
PubMed1984

Hypochlorite effects on spores and spore forms of Bacillus subtilis and on a spore lytic enzyme.

Spores of Bacillus subtilis NCTC 10073 were converted to ion-exchange (Ca, H) forms and coat-defective (urea-mercaptoethanol, urea-dithiothreitol-sodium lauryl sulphate) forms. The resistance of these to sodium hypochlorite (1000 parts/10(6) free chlorine) was compared and related to uptake from which the assumed monolayer capacities were calculated. Hypochlorite effects on spore protoplasts and cortical fragments were also examined in relation to DPA and hexosamine release. A spore lytic enzyme was extracted and examined in respect of hypochlorite activity. The results are discussed in terms of the mechanism and site of action of hypochlorite on the bacterial spore.

Bacillus subtilis↗
PubMed1984

Emergence and development of resistance to antimicrobial chemicals and heat in spores of Bacillus subtilis.

The emergence and development of chemical and thermal resistance in spores of Bacillus subtilis was examined. The chemicals studied were of the disinfectant type: glutaraldehyde, hypochlorite, hypochlorite-methanol and povidone-iodine. Growth and sporulation were followed by electron microscopy and resistance assigned to specific stages in relation to 45Ca and DPA accumulation. A sequential development of resistance was observed with thermal resistance appearing first at early Stage V corresponding to maturation of cortex and deposition of rudimentary spore coat material. Chemical resistance coincided with middle to late Stage V dependent on the chemical concerned. A progressive development of resistance was observed on prolonged incubation in sporulation medium and was affected by inclusion of lysozyme in the spore washing sequence.

Bacillus subtilis↗
PubMed1984

Interaction of the Bacillus subtilis spore protoplast, cortex, ion-exchange and coatless forms with glutaraldehyde.

Bacillus subtilis spores with altered ionic content were tested for their susceptibility to lysis with lysozyme or sodium nitrite following treatment with glutaraldehyde. The Ca-form was more sensitive to glutaraldehyde (pH 4.0 and pH 7.9) than the untreated or H-form. Removal of spore coat dramatically increased sensitivity of the spore to glutaraldehyde. Pretreatment of spores, the coats of which had been extensively removed, with glutaraldehyde (pH 7.9) reduced the rate of lysis by lysozyme and by sodium nitrite, whereas glutaraldehyde at pH 4.0 had little effect. Glutaraldehyde pretreatment (pH 4.0 and pH 7.9) reduced the amount of hexosamine released by lysozyme but not by nitrite from isolated cortical fragments. Spore protoplasts were more susceptible to 0.01% (w/v) glutaraldehyde at pH 4.0 and isolated spore coats adsorbed alkaline glutaraldehyde more rapidly. These results are discussed in terms of a possible mode of action of glutaraldehyde on the bacterial spore.

Aldehydes↗
PubMed1984

Spore differentiation in a clinical strain of Trichophyton mentagrophytes.

Spore differentiation and, in particular, arthrosporogenesis in a clinical strain of T. mentagrophytes was investigated using a variety of methods and by altering environmental conditions. Results are discussed with reference to the in vivo situation. Arthrospores were obtained in the presence of increased CO2 tension but not increased N2 tension. High humidity was necessary for arthrospore formation but maturity (i.e. crops of single spores) was associated with conditions of reduced humidity. Desiccation reduced arthrospore viability. Glucose and peptone based media were suitable for arthrospore formation. Arthrospores were produced at 30 degrees C and 37 degrees C, but 30 degrees C is preferred since chlamydospores were prevalent at 37 degrees C. Conditions for production of arthrospore, microconidial and mycelial suspensions are presented.

Carbon Dioxide↗
PubMed1983

Resetting of the baroreceptors by atenolol in the anaesthetized cat.

In anaesthetized cats, atenolol (3 mg X kg-1 i.v.) produced an immediate reduction in blood pressure, heart rate and aortic nerve discharge. However, 30 min and 60 min after atenolol there was a shift to the left of the curve relating aortic nerve discharge to mean arterial blood pressure indicating a delayed resetting of the baroreceptors. There was no evidence that atenolol altered the sensitivity of the baroreceptors.

Anesthesia, General↗
PubMed1983

The sensitivity of mycelium, arthrospores and microconidia of Trichophyton mentagrophytes to imidazoles determined by in-vitro tests.

With mycelium, arthrospores and microconidia of trichophyton mentagrophytes as inocula, a variety of in-vitro tests were used to assess the antifungal activity of the imidazoles; miconazole, clotrimazole, ketoconazole, econazole and tioconazole. For mycelial sensitivity, an agar plus method, a microtitre method using fragmented mycelial suspension and a turbidometric method were employed to determine fungistatic effects while a mycelial plug method indicated fungicidal activity. Spore susceptibility was determined by broth dilution and agar dilution methods for fungistatic action, while fungicidal activity was determined by measurement of rate of kill. The results obtained were affected to varying degrees by the test procedure, temperature and time of incubation, medium, pH and solvent. The spore forms were not more resistant than mycelium to the fungistatic effects of the imidazoles. There was little to choose between the various imidazoles in respect to their performance in these tests, with the exception of ketoconazole, which consistently gave higher MICs.

Antifungal Agents↗
PubMed1983

Death, injury and revival of chemically treated Bacillus subtilis spores.

The resistance of spores of Bacillus subtilis NCTC 10073 to glutaraldehyde, sodium hypochlorite and povidone-iodine was compared. Revival of treated spores was examined by use of defined germination media and conditions, protein denaturing agents, ultrasonics and heat. Revival, obtained after treatment with each of the three chemical agents, originated under different sets of conditions and was of two recognizably distinct types. The results, including the evidence of electron microscopy, are discussed in terms of chemical-spore reactivity and the implications on their use and suitability as chemical sterilizers.

Aldehydes↗
PubMed1983

The effect of atenolol on the spontaneous and reflex activity of the sympathetic nerves in the cat: influence of cardiopulmonary receptors.

1 Atenolol reduces sympathetic efferent discharge and attenuates the responses of the sympathetic nerves to changes in blood pressure. The present experiments were carried out to determine whether these changes were mediated by cardiopulmonary receptors whose afferents lie in the vagal nerves.2 Cats were anaesthetized with alpha-chloralose and artificially ventilated. In one group of cats recordings were made of sympathetic efferent discharge from few-fibre preparations from the lumbar trunk, splanchnic or renal nerves over a range of blood pressures. In a second group of cats changes in heart rate and blood pressure in response to bilateral occlusion of the common carotid arteries were investigated. In all cats the influence of vagal afferent fibres was removed by cooling both vagal nerves in the neck, both before and after administration of atenolol (3 mg kg(-1) i.v.).3 Cooling both vagal nerves produced significant increases in blood pressure, heart rate and spontaneous sympathetic efferent discharge but did not affect the relationship between sympathetic efferent discharge and mean blood pressure or the responses to carotid occlusion. Atenolol significantly reduced blood pressure, heart rate and sympathetic efferent discharge but the change in sympathetic efferent discharge on vagal cooling was less than before giving the drug. Atenolol also attenuated the reflex responses of the sympathetic nerves to changes in blood pressure and reduced responses to carotid occlusion. This attenuation was not removed by vagal cooling.4 Thus, neither the reduction in spontaneous sympathetic efferent discharge nor the attenuation of the baroreceptor reflex seen after atenolol, are due to an increased input to the brain from vagal afferent fibres. Other possible mechanisms whereby atenolol might exert its effects on the sympathetic nerves are discussed.

Action Potentials↗
PubMed1982

The effect of chemical sympathectomy on mitochondrial function in the ischaemic and reperfused myocardium.

1 Isolated rabbit hearts were perfused aerobically for 120 min, made ischaemic for 90 min, or made ischaemic for 90 min and then reperfused for 30 min. 2 Some rabbits were pretreated with 6-hydroxydopamine (6-OHDA), given as three separate intravenous doses of 30, 20 and 20 mg/kg, 20 to 48 h before they were killed; others (controls) received saline according to the same regime. 3 Mitochondria were harvested from left ventricular homogenates and their function assessed by measuring state 3O2 consumption (state 3 QO2), respiratory control index (RCI), phosphate: oxygen ratio (ADP:O), Ca2+ content, and ATP-producing activity. In other experiments peak left ventricular developed tension was recorded. 4 In hearts from saline-treated animals, mitochondrial state 3 QO2, RCI and ATP producing activities were reduced after global ischaemia, with or without reperfusion. There was a small gain in mitochondrial Ca2+ after ischaemia, and a large gain upon reperfusion. 5 6-OHDA pretreatment provided some protection against the effects of ischaemia and reperfusion on mitochondrial function and on peak developed tension. 6 It was concluded that chemical sympathectomy with 6-OHDA does not duplicate the effect of prolonged beta-adrenoceptor blockade in protecting mitochondrial function against the deleterious effects of ischaemia and reperfusion.

Adenosine Triphosphate↗
PubMed1982

The effects of stimulation of the left atrial receptors in the cat.

In the cat, distension of the left atrial appendages by means of small balloons resulted in variable changes in the heart rate. Distension of the junctions between the upper two left pulmonary veins and the left atrium resulted in a small but statistically significant increase in the heart rate. Distension did not result in any significant changes in the blood pressure. The increases in heart rate are far less than observed in the dog and it is suggested that the atrial receptors might play a less important role in cardiovascular control in the cat than they do in the dog.

Animals↗