Purification of glutamate dehydrogenase from ox brain and liver. Evidence that commercially available preparations of the enzyme from ox liver have suffered proteolytic cleavage.

1. A rapid procedure, involving ion-exchange chromatography on DEAE-cellulose and affinity chromatography on GTP-Sepharose, was used to purify glutamate dehydrogenase from ox brain and liver. 2. Preparations purified in this way differed from those of the ox liver enzyme that were obtained from commercial suppliers in their mobilities on polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate. This difference appears to result from the occurrence of limited proteolysis during the preparation of the latter enzyme samples. 3. N-Terminal sequence analysis showed the presence of four amino acid residues in the enzyme prepared in this study that were not present in those obtained from the commercial sources and which have not been reported in previous studies on the sequence of the ox liver enzyme. 4. A preliminary examination of the enzyme prepared in this way indicated that the Michaelis constants for the substrates are similar to those obtained from the commercial preparation, but that the response to allosteric effectors was modified.     

The nature of the electrophoretically separable multiple forms of rat liver monoamine oxidase

1. Treatment of a partly purified preparation of rat liver monoamine oxidase with the chaotropic agent sodium perchlorate caused the enzyme to migrate as a single band of activity of polyacrylamide-gel electrophoresis, whereas the untreated enzyme separated into a number of bands. 2. Treatment with the chaotropic agent caused no loss of enzyme activity towards benzylamine, dopamine or tyramine. 3. The activities of the untreated preparation towards different substrates were inhibited to different extents by heat treatment and by some inhibitors. No such differences could be detected after the enzyme preparation had been treated with sodium perchlorate. 4. Lipid material, which could be separated by gel filtration, was liberated from the enzyme preparation by sodium perchlorate treatment. 5. The molecular weight of the treated enzyme was found to be 380000+/-38000. 6. Perchlorate treatment altered the solubility of the enzyme. 7. A continuous assay method for monoamine oxidase is described.     

Isolation and characterization of calmodulin-inactivating cholesterol hydroperoxides.

A series of cholesterol hydroperoxides has been prepared and tested as inactivators of calmodulin. Two previously undescribed compounds, tentatively identified as 20-(R)-25-dihydroperoxy-5-cholesten-3 beta-ol and its 20-(S) isomer inactivate calmodulin with 50% loss of activity at 5-10 microM. Cholesterol derivatives with a single hydroperoxy group at C-20 or C-25 are less effective, while 7 alpha-hydroperoxy-cholesterol and 25-hydroxy-cholesterol are inactive. The side-chain hydroperoxide compounds were isolated from a mixture shown earlier to suppress formation of fatty streaks in aortas of rabbits fed a diet supplemented with cholesterol.     

Alkaline cooking and tortilla quality in maize grains from the humid,tropical lands of Mexico

Maize (Zea mays L.) tortilla is the major staple food for the Mexican population. Nine tropical maize genotypes were evaluated. All samples had white grains, a common characteristic in tropical maize, and therefore they were appropriate for nixtamalized flour industry. Grain, flour, masa and tortilla characteristics of each maize genotype were evaluated. Length, width, thickness, weight of 1000 grains and hardness of grain were determined. Moisture content, proteins, fat, ash, mean particle size, water absorption index, enthalpy, and flour temperature were also evaluated. Adhesiveness and cohesiveness were evaluated in masa. Moisture content, protein, capacity to puff up, roll making, tension and cutting strength were determined in tortillas. There were significant differences (p≤0.05) in most of the evaluated characteristics. Grain length values varied between 9.26 and 11.02 mm for populations 23 and 22, respectively. Grain hardness oscillated between 11.17 (population 32) and 14.75 (landrace Mejen). According to the weight of 1000 grains most genotypes had small grains. The minimum and maximum moisture values of flour and tortillas were 8.33-9.99% and 46.20-50.36%, respectively. The texture of tortillas elaborated from population 32 and landrace Mejen had the lowest tension and cutting strength, resulting the best genotypes for making tortilla.     

Thesaurus-based disambiguation of gene symbols

Background  

Massive text mining of the biological literature holds great promise of relating disparate information and discovering new knowledge. However, disambiguation of gene symbols is a major bottleneck.     

DNA divergence in and around the alcohol dehydrogenase locus in five closely related species of Hawaiian Drosophila

The alcohol dehydrogenase (Adh) region from five planitibia subgroup species of Hawaiian picture-wing Drosophila has been cloned. A total of 15 kb of DNA in and around the Adh gene has been compared among the five species. Genetic distances were calculated to determine evolutionary relationships. These distances agree with previous distances determined by protein polymorphism and DNA hybridization techniques and can be interpreted in terms of specific island colonization and speciation (founder) events over the past 5 Myr. Examination of the restriction maps of the cloned Adh region from the five species shows many instances of small deletions, insertion of a transposable element in D. heteroneura, and the existence of a highly variable region on the 3' side of the Adh gene. Clustering relationships and rates of DNA change are calculated and compared with the relationship found for other species of Drosophila.      

Influence of fasting and hormone deficiency on myocardial glycogen levels in rats.

This study was undertaken because of uncertainties regarding the influence of hormones on myocardial glycogen metabolism of fed and fasted rats. The results indicate that adrenal hormones exert a stabilizing effect on myocardial glycogen levels in fed animals but are not necessary for synthesis to occur. Hypophysectomy eliminates the glycogen increase that occurs from fasting in normal animals while insulin deficiency leads to elevated glycogen stores in both fed and fasted conditions. These findings suggest that changes in myocardial glycogen metabolism are the results of a synergetic relationship between a variety of hormonal and nutritional factors.     

Phylogenetic screening of the human genome: identification of differentially hybridizing repetitive sequence families

The phi-screen, a method of phylogenetic screening, can be employed to detect repetitive sequence families that differentially hybridize between closely related species. Such differences may involve sequence divergence or variations in copy number, including total presence versus absence of a family of repeated DNA. We present the results of a phi-screen comparing the human genome to that of the prosimian, Galago crassicaudatus. Three human repetitive families that are divergent or not present in galago have been detected. One of these families is described in detail; it is similar among the anthropoids but is present in a lower copy number and/or divergent form in prosimians. The family is clearly related to the transposon-like human element (THE) described by Paulson et al. (1985). THEs have long terminal repeats reminiscent of retroviruses but are unique in that they have no sequence similarity to known mammalian retroviruses. The sequence of a solo long terminal repeat, found unassociated with THE internal sequence, is presented. This family member, THE p2, is bordered by a 5-bp target-site repeat and is interrupted by the insertion of an Alu element. A solo THE element sequenced by Wiginton et al. (1986) contains an insertion of Alu at precisely the same position as does THE p2.