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Biomedical subjects

J C Stewart

Publications and source records attributed to J C Stewart.

At least 73 records · Page 4Linked to original sources
PubMed1981

Factors influencing the production of cellulase by Aspergillus fumigatus (Fresenius).

During growth in liquid culture containing a single cellulosic or non-cellulosic carbon source, a newly isolated strain of Aspergillus fumigatus released cellulases into the medium; the amounts produced depended on the nitrogen source, the type and concentration of the carbon source, pH and temperature. Extracellular cellulolytic activity was still increasing after incubation for 60 d with 1% (W/V) CF11 cellulose, (NH4)2SO4 as nitrogen source and a starting pH of 7. The activities of the new isolate were compared with those of A. fumigatus IMI 143864 and Trichoderma reesei QM6a (ATCC 13631) and it was shown to be a good producer of beta-glucosidase.

Aspergillus fumigatus↗
PubMed1981

Sex- and age-related mouse toxicity and disposition of the amino acid antitumor agent, acivicin.

Studies of acivicin [(alpha S,5S)-alpha-amino-3-chloro-2-isoxazoline-5-acetic acid, AT-125] plasma levels in ICR, B6D2F1 and CD2F1 mice after single dose i.p. administration showed that total body clearance of drug by male mice was ca. twice the clearance by females of the same strain. Clearance was also greater in older (22-25 g) than in younger (15-18 g) ICR mice. Testosterone pretreatment increased the clearance of acivicin by ICR female mice to that of males. Sex- and age-related differences in pharmacokinetics were more pronounced than strain differences. Excretion studies showed that 53 to 82% of doses were recovered unchanged in the urine with no significant differences between sexes in urinary recovery. In tissue distribution studies in ICR mice, the tissue/plasma concentration ratios at each sampling time were similar for both sexes in all tissues analyzed except kidney (male range: 7-22; female range: 1.5-2.5) and muscle (male range: 5-9; female range: 0.8-1.4). Testosterone pretreatment of females increased the kidney/plasma concentration ratio of acivicin to that of males. Acivicin was also shown to be more toxic (as indicated by LD50) to female than to male mice of the B6D2F1 and CD2F1 strains, in agreement with previous studies in ICR mice. The disposition data suggest that the sex- and age-dependent toxicity of acivicin in mice is due to differences in pharmacokinetics which, in turn, may be related to renal excretion mechanisms.

Age Factors↗
PubMed1980

Molecular size, subunit structure and microheterogeneity of glycoprotein II from the seeds of kidney bean (Phaseolus vulgaris L.).

The isolation of Glycoprotein II from the seeds of kidney bean (Phaseolus vulgaris) cv. 'Processor' is described. This glycoprotein was shown by SDS-gel electrophoresis to dissociate into four subunits, 53 000, 50 000, 47 000 and 43 000 (alpha : beta : gamma : delta), in an approximate ratio of 2 : 0.2 : 2 : 1. At neutral and slightly alkaline pH values its molecular weight was about 142 000 (protomer) while at pH 5 it was mainly in the form of a tetramer with a molecular weight value of about 560 000. Samples of Glycoprotein II were shown by isoelectric focusing, molecular sieve chromatography and immunochemical methods to be microheterogenous. A number of fractions were prepared by these methods in which the proportion of the major subunits (alpha : gamma : delta) varied between 1 : 1 : 1 to 3 : 3 : 1. These ratios were also shown to change during development of the seed. On the basis of these results it is suggested that, at and above pH 7, samples of Glycoprotein II consist of microheterogenous population of molecules each containing three subunits per protomer. However, in these protomers the subunits are drawn, in different ratios, from the four subunits available. When the net molecular charge is small, at and around the isoelectric zone of Glycoptotein II, the protomer is converted mainly into the more stable tetramer containing 12 subunits.

Electrophoresis, Disc↗
PubMed1979

Isolation and characteristics of Yersinia enterocolitica-like bacteria from meats.

Seventeen Yersinia enterocolitica-like isolates from vacuum-packaged beef and lamb are described. A majority of the isolates were motile at 25 degrees C but not at 36 degrees C, utilized citrate at 25 degrees C (delayed or negative at 36 degrees C) and produced acid from rhamnose, raffinose and melibiose. Increases in count of Y. enterocolitica occurred on raw beef stored at 0--1 degrees C over a 10-day period. No viable Y. enterocolitica were detected in beef roasts which were inoculated with about 3 x 10(6) cells/g and subsequently heated to a final internal temperature of 60--62 degrees C. Y. enterocolitica counts of inoculated beef steaks stored at 1--5 degrees C for 21--35 days were consistently higher in the more oxygen-permeable films than in vacuum packages. Colonies of Y. enterocolitica and related bacteria from meats produced shiny, enamel-black colonies on bismuth sulfite agar with plate incubation at 25 degrees C for 3--5 days.

Agar↗
PubMed1978

Isolectins of Phaseolus vulgaris. Physicochemical studies.

By a combination of solubility fractionation, continuous free-flow high voltage electrophoresis, molecular sieve and affinity chromatography on fetuin-Sepharose 4B, several lectin fractions of different isoelectric point were obtained from the seeds of Phaseolus vulgaris cv. "Processor". The albumin isolectin range comprised of five major lectin components with isoelectric points between pH 4.6 and 5.2, while the partly overlapping globulin isolectins contained several more lectin components with higher isoelectric points. The two groups had similar amino acid and sugar composition but were only partially identical by immunochemical criteria. The isolectins were also shown to be similar by physicochemical measurements with a common protomer weight value of about 119000. Values of so20,w, 6.84 and 6.76 S, and of V av, 0.712 and 715 ml/g, for the albumin and the globulin lectins, respectively, also indicated a close similarity. Both groups contained, in a slow equilibrium with the protomer, just over 10% of dimer and oligomers. In addition, the albumin lectins also contained a small, 2 S, dissociation product in a slow equilibrium with the protomer. The hydrodynamic data obtained for the albumin isolectins: [eta] = 0.063 dl/g; beta = 2.42 . 10(6) and f/fo = 1.56 indicated a highly voluminous particle with an effective volume of 8.6 . 10(-18) ml. This type of molecular arrangement was general for the major P. vulgaris seed glycoproteins and was, thus, suggested to be of potential importance for their physiological functioning during seed maturation and germination.

Amino Acids↗
PubMed1977

The state of aggregation of red deer (Cervus elaphus L.) beta-lactoglobulin preparations near neutral pH.

1. The state of aggregation of four red-deer (Cervus elaphus L.) beta-lactoglobulin preparations and a control ox beta-lactoglobulin A preparation was studied by sedimentation-equilibrium experiments at pH 6.5 and 20 degrees C. 2. Three of the deer preparations and the ox control each behaved as a monomer-dimer system, with a value of log K (where K is the association constant in litres/mol) in the range 5.4-5.5. 3. When one of these deer preparations was examined in the presence of dithiothreitol, log K appeared to decrease to 4.5.4. One deer preparation, comprising recovered material, appeared to have undergone irreversible changes and to behave like a non-equilibrating system containing monomer, dimer and trimer. 5. The sedimentation-equilibrium properties of the deer monomer was studied in 6M-guanidine hydrochloride at pH 7.0; the mol.wt. was 17600, the second virial coefficient was 3.4 x 10(-3) ml - mol - g-2, and the apparent partial specific volume 0.724 ml/g, a value indicating an appreciable decrease in volume on dissociation and denaturation.

Animals↗
PubMed1976

The whey proteins of the milk of red deer (Cervus elaphus L.). A homologue of bovine beta-lactoglobulin.

1. The whey proteins from the milk of red deer are compared with those of cattle. Gel chromatography and electrophoresis showed a close similarity between the whey proteins of the two species in the size, mobility and relative amounts of the main constituents and in the changes in their relative amounts with time after parturition. 2. The major constituent of the deer whey was isolated. It appeared to be homologous with bovine beta-lactoglobulin and had the following properties: m=-5.2X10(-9)m2-s-1-V-1 at 4 degrees C and pH 8.6; pI=5.17; S020, w =2.89S; v=0.748 ml/g; E1g/dl 1cm= 9.12 at 278 nm; deltan/c=1.794 X 10(-3)dl/g at 579 nm (all at 20 degrees C except m). Its molecular weight was that of a dimer with a subunit weight of 18 000. 3. Amino acid analyses of this protein, adjusted to lysine = 15 residues showed that it contains one more residue of aspartic acid, alanine and methionine and one less glutamic acid residue and two less leucine residues than bovine beta-lactoglobulin A. 4. On starch-gel electrophoresis at pH 8.2, this protein migrated at the same rate as bovine beta-lactoglobulin B, although its isoelectric point is close to that of the bovine A variant. Milk from three out of 27 hinds examined showed a variant. This migrated in starch gel at the same rate as the bovine A variant but had a more acid pI = 5.02. 5. The two species whose milk whey proteins are compared represent two different families of ruminants. The similarities found support the view that the milk whey proteins of the bovids are probably typical of the suborder as a whole.

Amino Acids↗
PubMed1976

Thyrotoxicosis induced by iodine contamination of food--a common unrecognised condition?

The incidence of thyrotoxicosis in northern Tasmania rose significantly in 1964, two years before an epidemic of iodine-induced thyrotoxicosis was precipitated by the addition of iodate to bread to prevent goitre. Each time older patients accounted for most of the increase. The 1964 increase was probably iodine-induced as the use of iodophor disinfectants on dairy farms, which causes iodine residues in milk, began in 1963 and a fall in the prevalence of goitre in young children suggested an increase in dietary iodine at about that time. A further small increase in thyrotoxicosis in 1971 may also have been iodine-induced as it followed an extension of the use of iodophors. Dietary iodine is rising substantially in many places because of high iodine levels in milk and the use of iodine compounds in automated bread making, and this may be causing unsuspected iodine-induced thyrotoxicosis. Dietary iodine should be monitored regularly and clinicans alerted to any rise. Contamination of common foods with iodine should be more strictly controlled.

Adult↗
PubMed1975

Hyperthyroidism in Tasmania following iodide supplementation: measurements of thyroid-stimulating autoantibodies and thyrotropin.

Serum thyroid-stimulating autoantibodies (LATS and LATS protector) and thyrotropin (TSH) concentrations were measured in the serum of 30 patients with hyperthyroidism living in Tasmania who developed their disease following correction of iodine deficiency by addition of iodate to the bread. Patients were grouped according to thyroid scan results. None of 8 patients with autonomous thyroid nodules had thyroid-stimulating autoantibodies. These were present in both of the patients with uniform thyroid scans and 14 of 20 patients (70%) with irregular scans without demonstrated localized autonomy. Serum TSH, measured by immunoassay of concentrated serum extracts, was 0.15 muU/ml or less in all patients, below the range of 0.35 to 2.60 muU/ml found in normal subjects. Only 6 (20%) of the 30 patients failed to show either localized autonomy or thyroid-stimulating autoantibodies. In most regards these patients resembled those with antonomous nodules. The findings support the conclusion that the increased incidence of phyerthyroidism in Tasmania was due to an increased supply of iodine to patients with latent hyperthyroidism whose thyroid glands, due to the presence of toxid nodule(s) or thyroid-stimulating autoantibodies, were unresponsive to control by TSH deprivation. There was no evidence for additional pathogenic mechanisms

Adult↗