1,875 Matching Results

Search Results

Advanced search parameters have been applied.

Metabolism of Hydrocortisone by X-Irradiated Rat Liver Tissue as Determined by the Porter-Silber Chromagen Method

Description: The present study may be considered endocrinological and radiobiological in nature. The endocrinology phase was concerned with studying the changes in endocrine function following the application of a stress agent. X-irradiation was chosen as the stressor in order to determine any difference in effect of this stressor from others which have been studied, e. g. heat, cold, metabolic poisons. Liver slices taken from rats at various time intervals following whole body X-irradiation were tested for their ability to metabolize hydrocortisone from a Krebs-Ringer solution.
Date: August 1959
Creator: Pryor, Nan Webb
Partner: UNT Libraries

Pyrimidine Metabolism in Rhizobium: Physiological Aspects of Pyrimidine Salvage

Description: The objective of this research was to study the pyrimidine salvage pathways of Rhizobium. Three approaches were used to define the pyrimidine salvage pathways operative in two species of Rhizobium, R. meliloti and R. leguminosarum . The first approach was to ascertain the pyrimidine bases and nucleosides that could satisfy the pyrimidine requirement of pyrimidine auxotrophs. Uracil, cytosine, uridine or cytidine all satisfied the absolute pyrimidine requirement. The second approach was to select for mutants resistant to 5-fluoropyrimidine analogues which block known steps in the interconversion of the pyrimidine bases and nucleosides. Mutants resistant to 5-fluorouracil lacked the enzyme uracil phosphoribosyltransferase (upp ) and could no longer use uracil to satisfy their pyrimidine requirement. Mutants resistant to 5-fluorocytosine, while remaining sensitive to 5- fluorouracil, lacked cytosine deaminase (cod) and thus could no longer use cytosine to satisfy their pyrimidine auxotrophy. The third approach used a reversed phase HPLC column to identify the products that accumulated when cytidine, uridine or cytosine was incubated with cell extracts of wild type and analogue resistant mutants of Rhizobium. When cytidine was incubated with cell extracts of Rhizobium wild type, uridine, uracil and cytosine were produced. This Indicated that Rhizobium had an active cytidine deaminase (cdd) and either uridine phosphorylase or uridine hydrolase. By dialyzing the extract and reincubating it with cytidine, uridine and uracil still appeared. This proved that it was a hydrolase ( nuh ) rather than a phosphorylase that degraded the nucleoside. Thus, Rhizobium was found to contain an active cytidine deaminase and cytosine deaminase with no uridine phosphorylase present. The nucleoside hydrolase was active with cytidine, uridine and to a far lesser extent with purines, adenosine and inosine. When high concentrations of cytidine were added to mutants devoid of hydrolase, cytosine was produced from cytidine - 5-monophosphate by the sequential action ...
Date: December 1989
Creator: Ibrahim, Mohamed M.
Partner: UNT Libraries

Novel Hydrogen Production Systems Operative at Thermodynamic Extremes

Description: We have employed a suite of molecular, bioinformatics, and biochemical tools to interrogate the thermodynamically limiting steps of H{sub 2} production from fatty acids in syntrophic communities. We also developed a new microbial model system that generates high H{sub 2} concentrations (over 17% of the gas phase) with high H{sub 2} yields of over 3 moles H{sub 2} per mole glucose. Lastly, a systems-based study of biohydrogen production in model anaerobic consortia was performed to begin identifying key regulated steps as a precursor to modeling co-metabolism. The results of these studies significantly expand our ability to predict and model systems for H{sub 2} production in novel anaerobes that are currently very poorly documented or understood.
Date: November 30, 2012
Creator: Gunsalus, Robert
Partner: UNT Libraries Government Documents Department

Studies of Porphyrin Metabolism, 3. The Relation of Erythropoiesis to the Excretion of Coproporphyrin by Dogs and Rabbits, and to the Concentration of Coproporphyrin and Protoporphyrin in Rabbit Erythrocytes

Description: Report discussing studies regarding porphyrin excretion and hemoglobin metabolism in animals with phenylhydrazine anemia, and studies regarding the coproporphyrin and protoporphyrin in the red blood cells of rabbits.
Date: November 25, 1945
Creator: Schwartz, Samuel; Glickman, Marcia; Hunter, Rosie & Wallace, Jean
Partner: UNT Libraries Government Documents Department

The Metabolism of Chyle Cholesterol in the Rat

Description: Abstract: "Observations on the metabolism of chyle cholesterol in the rat show that exogenous cholesterol entering the systemic circulation in chyle exists in lipoproteins of low density (including chylomicrons) migrating with a high Sf rate (i.e.>400) in the ultracentrifuge. Following entry into the systemic circulation these molecules are rapidly removed from the plasma. This "clearing" of serum chyle cholesterol is a tissue phenomenon, the liver being the predominant site. Within the liver the chyle cholesterol esters are at least partially hydrolyzed; hydrolysis apparently does not occur in the plasma to any appreciable extent. After its entry into the liver exogenous cholesterol, if normally metabolized, presumably mixes with and becomes indistinguishable from cholesterol produced by endogenous synthesis."
Date: May 12, 1954
Creator: Biggs, Max William & Nichols, Alexander V.
Partner: UNT Libraries Government Documents Department

Accumulation of Flavonols over Hydroxycinnamic Acids Favors Oxidative Damage Protetion under Abiotic Stress

Description: This article reports on the characterization of the different antioxidant mechanisms of tomato plants subjected to heat stress, salinity stress, or a combination of both stresses.
Date: June 15, 2016
Creator: Martinez, Vicente; Mestre, Teresa C.; Rubio, Francisco; Girones-Vilaplana, Amadeo; Moreno, Diego; Mittler, Ron et al.
Partner: UNT College of Arts and Sciences

Purification and Studies of Methylglyoxal Reductase from Sheep Liver

Description: The objectives of these investigations were (1) the purification of MG reductase from sheep liver and (2) studies of some of its characteristics. MG reductase was purified 40 fold and showed a single band on SDS-PAGE. Molecular weight estimations with SDS-PAGE showed a molecular weight of 44,000; although gel filtration with Sephadex G-150 gave a molecular weight of 87,000 indicating that the enzyme might be a dimer. The Km for MG is 1.42 mM and for NADH it is 0.04 mM. The pH optimum for the purified enzyme is pH 7.0. Isoelectric focusing experiments showed a pI of 9.3. In vivo experiments involving rats treated with 3,3',5-triiodothyronine (T_3) and 6-n-propyl-2-thiouracil (PTU) indicated that MG reductase was depressed by T_3 and elevated by PTU.
Date: May 1983
Creator: Lambert, Patricia A.
Partner: UNT Libraries

Effect of Operant Behavior on the Metabolism of 5-Hydroxytryptamine

Description: The role of operant behavior in the metabolism of brain 5-hydroxytryptamine (5-HT) turnover was investigated. Two and one-half hours following the administration of 150 mg/kg of para-chlorophenylalanine (PCPA), a specific inhibitor of tryptophan hydroxylase, levels of 5-HT were compared in sedentary and performing rats. Whole brain levels of serotonin were reduced in both responding and sedentary animals; however, differences between these groups were not statistically significant. The drug induced decrease in 5-HT levels was accompanied by a significant decrease in session responding. The degree of suppressed responding could be correlated with the level of 5-HT following PCPA, suggesting that the metabolism of serotonin is in part modulated by the rate of responding as maintained by the operant schedule.
Date: August 1979
Creator: Shepard, Paul
Partner: UNT Libraries

A Study of Lean Body Mass in Estimating Basal Metabolic Rate

Description: The primary purpose of the study was to determine if measured LBM could be used as a more powerful predictor of BMR than could surface area (SA) as calculated by the formula of DuBois and DuBois (1916). It was also of interest to develop a prediction equation for BMR using multiple regression analysis. Data from 82 women and 76 men were included in the study. Pearson product-moment correlations indicated that LBM was a better predictor for BMR than SA on either of the principal SA prediction equations, those of Aub and DuBois (1917) and Harris and Benedict (1919). Age, sex, and fat weight were not found to contribute significantly to prediction when included by multiple regression analyses. Linear equations for BMR as a function of LBM were developed for each sex. Tables based on these equations were also generated as a quick reference for clinicians.
Date: May 1985
Creator: Lachenbruch, Charles
Partner: UNT Libraries

Pyrimidine Metabolism in Streptomyces griseus

Description: Salvage of pyrimidine nucleosides and bases by S. griseus and the regulation of aspartate transcarbamoylase (ATCase) were studied. The velocity-substrate curve for S. griseus ATCase was hyperbolic for both aspartate and carbamoylphosphate. The enzyme activity was diminished in the presence of ATP, CTP, or UTP. The synthesis of ATCase was repressed in cells grown in the presence of exogenous uracil. The specific activity of cells grown with uracil was 43 percent of that for cells grown in minimal medium only. Maximal ATCase and dihydroorotase activities were found in the same column fraction after size-exclusion chromatography, suggesting that both activities could reside in the same polypeptide. The pyrimidine salvage enzymes cytosine deaminase and uridine phosphorylase were identified in S. griseus using HPLC reversed-phase chromatography.
Date: August 1994
Creator: Hughes, Lee E. (Lee Everette)
Partner: UNT Libraries

Identification and quantification of lipid metabolites in cotton fibers: Reconciliation with metabolic pathway predictions from DNA databases.

Description: The lipid composition of cotton (Gossypium hirsutum, L) fibers was determined. Fatty acid profiles revealed that linolenate and palmitate were the most abundant fatty acids present in fiber cells. Phosphatidylcholine was the predominant lipid class in fiber cells, while phosphatidylethanolamine, phosphatidylinositol and digalactosyldiacylglycerol were also prevalent. An unusually high amount of phosphatidic acid was observed in frozen cotton fibers. Phospholipase D activity assays revealed that this enzyme readily hydrolyzed radioactive phosphatidylcholine into phosphatidic acid. A profile of expressed sequence tags (ESTs) for genes involved in lipid metabolism in cotton fibers was also obtained. This EST profile along with our lipid metabolite data was used to predict lipid metabolic pathways in cotton fiber cells.
Date: May 2004
Creator: Wanjie, Sylvia W.
Partner: UNT Libraries

Developmental Patterns of Metabolism and Hematology in the Late Stage Chicken Embryo (Gallus Domesticus) at Two Incubation Temperatures.

Description: How temperature affects physiological development in the chicken embryo is unknown. Embryos incubated at 38°C or 35°C showed no difference in growth or survival. The time to hatching was longer in 35°C than 38°C embryos (23.7 vs. 20.6 days), but unaffected was the relative timing of appearance of developmental landmarks (internal, external pipping). At stage 43-44, 38°C embryos maintained oxygen consumption around 1 mL/g/h despite acute temperature reduction (suggesting thermoregulatory maturation), unlike 35°C embryos. In 35°C embryos the lower oxygen-carrying capacity and temperature insensitive blood O2 affinity (P50 about 30 mmHg) may restrict O2 delivery to tissues, limiting metabolism during decreased ambient temperature. Reduced incubation temperature retards normal hematological and thermoregulatory development.
Date: May 2003
Creator: Black, Juli
Partner: UNT Libraries

The effects of EDTA chelation therapy on plaque calcium and mineral metabolism in atherosclerotic rabbits

Description: New Zealand albino rabbits exhibited calcified aortic plaques and maximum average serum cholesterol levels of 1200 mg percent after twenty-three weeks on an atherogenic diet (250 to 500 mg percent cholesterol in ten percent corn oil; 200,00 I.U. vitamin D3 per month). One month following termination of the atherogenic diet, rabbits were treated with disodium edetate (Na2EDTA, 50 mg/kg body weight) via the marginal ear vein, on alternating days for a total of twenty infusions each. Aortae were examined for tissue calcium both quantitatively (direct microcomplexometric analysis) and histologically six weeks after completion of EDTA chelation therapy.
Date: May 1980
Creator: Walker, Foster M.
Partner: UNT Libraries

Human phosphoglucose isomerase: isolation and characterization of wild type and the Singh allozyme

Description: A procedure was developed for the rapid isolation of human phosphoglucose isomerase by substrate-induced elution from cellulose phosphate. The high degree of selectivity of the elution provided homogenous enzyme from erythrocytes after a purification of approximately 30,000-fold with a recovery of approximately 70%. The enzyme was also isolated from other human tissues by a similar procedure.
Date: August 1974
Creator: Tilley, Bill E.
Partner: UNT Libraries

Evaluation of immobilized boronates for studies of adenine nucleotide metabolism

Description: Immobilized boronates were evaluated for studies of adenine nucleotide metabolism. These studies were performed using Affi-gel 601, a commercial boronate gel, and dihydroxyboryl Sepharose and dihydroxyboryl-Bio Rex which were synthesized in the laboratory. The studies performed included the determination of the relative binding affinity of a variety of adenine containing compounds for the three immobilized boronates under differing chromatographic conditions.
Date: August 1982
Creator: Alvarez-Gonzalez, Rafael
Partner: UNT Libraries

Isolation of the xylE-xylL region of Pseudomonas putida plasmid pDKR1 and determination of the complete nucleotide sequence of the xylE gene encoding catechol 2,3-dioxygenase

Description: A 5.1 kbEcoR I fragment from Pseudomonas putida TOL plsmid pDKR1, carrying the xylE and xylL genes, was inserted into pBR 325 and transformed into E. coli. The xylE region, coding for catechol 2,3-dioxygenase, was subjected to Maxam-Gilbert sequencing reactions.
Date: May 1989
Creator: Voss, John A. (John Andrew)
Partner: UNT Libraries