Biomedical subjects

L R HEDRICK

Publications and source records attributed to L R HEDRICK.

18 recordsLinked to original sources

PubMed1964

GROWTH OF ACANTHAMOEBA CASTELLANI WITH THE YEAST TORULOPSIS FAMATA.

Nero, L. C. (Illinois Institute of Technology, Chicago), Mae G. Tarver, and L. R. Hedrick. Growth of Acanthamoeba castellani with the yeast Torulopsis famata. J. Bacteriol. 87:220-225. 1964.-Acanthamoeba castellani and Torulopsis famata cells were cultured together for 10 days at three different temperatures: 18, 25, and 32 C. In the 18- and 25-C series, the yeast population reached a peak within 3 to 5 days and then declined for the next 5 days. This decrease in yeast population corresponded with an increase in the development of amoebae, which first appeared as vegetative cells and later transformed themselves into cysts. The changes in population were determined by counts in a hemocytometer. The vegetative amoeba population seldom exceeded 4 x 10(7) cells per bottle culture, but the encysted population approached 16 x 10(7) cysts per bottle culture within 10 days of incubation. The amoebae actively ingested the yeasts and used these cells as their principal source of energy. At 18 C each amoeba consumed 70 yeast cells per day; at 25 C each amoeba ingested 35 yeast cells per day. In the 32-C series, both the yeast and the amoebae had slow growth rates. The development of cysts corresponded with the growth of the yeast population without the rapid increase in yeast population prior to the growth of the amoebic cells.

Acanthamoeba castellanii↗

PubMed1964

PROLINE OXIDASES IN HANSENULA SUBPELLICULOSA.

Ling, Chung-Mei (Illinois Institute of Technology, Chicago), and L. R. Hedrick. Proline oxidases in Hansenula subpelliculosa. J. Bacteriol. 87:1462-1470. 1964-Cells of Hansenula subpelliculosa can use l-proline as a carbon and a nitrogen source after a 6- to 8-hr induction period. However, they cannot use l-glutamate as both nitrogen and carbon sources unless the induction period is of several days' duration. Two l-proline oxidases were demonstrated in the mitochondrial preparation of this yeast. One forms the product Delta'-pyrroline-2-carboxylic acid (P2C), which is in equilibrium with alpha-keto-delta-amino-valeric acid; the other forms the product Delta'-pyrroline-5-carboxylic acid (P5C), which is in equilibrium with glutamic-gamma-semialdehyde. The first-mentioned enzyme is induced when l-proline is the carbon source; the second appears to be constitutive, and is probably associated with the use of l-proline as a nitrogen source. The P2C-forming enzyme is specific for the l isomer of proline, and is inactive against l-hydroxyproline. The enzyme activity is at its peak when the mitochondria are prepared from logarithmically grown cells, and is rapidly reduced after cells reach the stationary phase of growth. Kinetic studies with varying concentrations of substrate indicate a Michaelis-Menten constant of 2.45 x 10(-2)m. Paper chromatographic studies, chemical tests with H(2)O(2), sensitivity to freezing, and spectral measurements indicate that proline oxidase from H. subpelliculosa mitochondria forms a product from l-proline which is like, if not identical to, P2C formed by the action of sheep kidney d-proline oxidase upon dl-proline. The soluble portion of the cell extract contains NAD(+) enzymes which use either P2C (alpha-keto-delta-amino-valeric acid) or P5C (glutamic-gamma-semialdehyde) as substrates. No glutamic dehydrogenase activity could be detected when l-glutamic acid and the nicotinamide adenine dinucleotide (NAD(+)) cofactor were added to the supernatant solution with the yeast enzymes. The presence of a dehydrogenase NAD(+) enzyme for activity with P2C (alpha-keto-delta-amino-valeric acid) has not been previously reported.

Amino Acid Oxidoreductases↗

PubMed1963

Adsorption and fluorescence of fat-soluble fluorescent dyes on class I and class III Saccharomyces cerevisiae.

Lycette, R. M. (Illinois Institute of Technology, Chicago) and L. R. Hedrick. Adsorption and fluorescence of fat-soluble fluorescent dyes on class I and class III Saccharomyces cerevisiae. J. Bacteriol. 85:1-6. 1963.-Class III cells of the brewery yeast Saccharomyces cerevisiae flocculate, but class I cells do not, when cultured in an organic YM medium. Class III cells adsorb the fat-soluble stilbyl-triazole fluorescent dye (STC) more readily and produce more fluorescence than do class I cells. This suggests that cells of the class III yeasts have more lipids or more phospholipids on their surface than do cells of class I yeasts. Fluorescence of STC in the absence of cells is pH-independent, but adsorption of the compound on the surface of cells, with the associated fluorescence, is pH-dependent. As the pH level was decreased within the range of pH 9 to 0, and as the temperature was elevated within the range of 0 to 40 C, there was an increase in adsorption and a corresponding increase in fluorescence. Maximal adsorption was attained in less than 15 min when the cells and dye were shaken at 26 C. Cells of class III adsorbed 2.5 mug of STC per 3.25 mg (dry wt) of cells. The kinetics of adsorption follow the Langmuir monomolecular model.

Adsorption↗

PubMed1963

EFFECT OF CATIONS UPON HYDROPHOBICITY OF YEASTS GROWN IN AMINO ACID MEDIA.

Hedrick, L. R. (Illinois Institute of Technology, Chicago), and C. J. Feren. Effect of cations upon hydrophobicity of yeasts grown in amino acid media. J. Bacteriol. 86:1288-1294. 1963.-Cells of four species of Hansenula, namely, H. holstii Y2154, H. subpelliculosa Y1683 and Y1542, and H. anomala Y365, were cultured for 3 days in a glucose-salts medium with one amino acid or (NH(4))(2)SO(4) as a nitrogen source. The l-amino acids used were glutamic acid, valine, proline, lysine, histidine, phenylalanine, tyrosine, and tryptophan. After growth, the cells were washed three times and added to small tubes which contained varying concentrations of chlorides of the cations Cs(+), K(+), Na(+), and Al(+++). The concentration of salt in ionic strength required for sedimenting yeast cells to form a fixed pellet represents an index of hydrophobicity of the cells, i.e., the smaller the ionic strength, the greater the hydrophobicity. All species grown in (NH(4))(2)SO(4) had a high degree of hydrophobicity. Cells of H. holstii and H. subpelliculosa Y1683 were very hydrophilic when cultured in the three aromatic amino acids as a nitrogen source and in proline as a carbon and a nitrogen source; cells of the latter species were much more hydrophobic if grown with proline as a nitrogen source. Cells of H. holstii cultured in l-glutamic acid as a nitrogen source were much more hydrophobic than those grown in proline as either a nitrogen or a carbon source. Cells of all species grown in l-lysine were more hydrophobic than cells cultured in the other amino acids tested. H. subpelliculosa Y1542 cells were somewhat more hydrophilic than those of H. anomala Y365, but both were much more hydrophobic than the other two yeasts studied. The concentration of cations required to detect an identical degree of hydrophobicity of cells decreased in the order Cs, Li, K, Na, and Al. This order corresponds to the compressibility method for estimating the water of hydration of the cations.

Amino Acids↗

PubMed1962

Action of deflocculating agents on Saccharomyces cerevisiae Class III brewer's yeast.

Earlier work with a fluorescent aid indicated that flocculent brewer's yeast may have more surface lipids than nonflocculent types. Organic solvents were checked against flocculent Gilliland yeasts. It was found that those reagents which affect "free" lipids had no dispersive action, and those which remove "bound" fats had a powerful dispersive action against such yeasts. There was no indication that such an action could be correlated with other physical properties of the solvents. The uranyl ion is known for its ability to complex with phospholipids, and it was found to have a powerful dispersive action on Gilliland yeasts. Its effect was compared with that of glucose in its dispersion of yeast flocs, and possible cell "sites" were suggested. This, along with other work, suggests the possibility that lipids are directly or indirectly involved in yeast flocculation.

Alcohols↗

PubMed1961