John A.D. Cooper

Lipogenesis by adipose tissue, dietary effects.

Summary 1. The incorporation of C14-acetate into lipid and carbon dioxide by rat adipose tissue (in vitro) was investigated. This investigation concerned the effect of the nutritional status upon the lipogenic activity of adipose tissue. 2. Fasting was found to produce an increase in nitrogen concentration and a decrease in lipid concentration and lipogenic activity. 3. In normal rats lipogenic activity of the tissue was found to increase during recovery feeding following fasting. The increased activity was paralleled by increased nitrogen and glucose content of the tissue and by decreased lipid content. 4. Lipogenic activity of adipose tissue of rats could be made relatively constant by depletion of fat stores followed by recovery feeding.

Acid Hydrolysis of Erythropoietin.

Summary Purified erythropoietin has been subjected to mild acid hydrolysis. This mucoprotein thus has been further characterized and shown to lose erythropoietic activity upon hydrolytic removal of neuraminic acid.

Purification of Erythropoietin by Ion-Exchange Chromatography

Summary A method for purification of erythropoietin from the filtrate of acidified, boiled plasma prepared from phenylhydrazine anemic rabbits utilizing DEAE-cellulose ionexchange columns has been described. The active erythropoietic factor thus prepared has been partially characterized and shown to be a low molecular weight, acidic glycoprotein.

Incorporation of radioacetate into lipid by adipose tissue in vitro: lipid characterization.

Abstract Normal minced rat epididymal adipose tissue incubated in vitro with 14 C- I -acetate incorporates the label almost entirely into the fatty acids of triglycerides with negligible incorporation into other lipid components (including cholesterol esters, cholesterol, non-esterived fatty acid, and phospholipid).

Erythropoietic effect of red blood cell components and heme-related compounds.

Summary 1. Regardless of age, sex, or species of the donor animals, lysed mammalian red blood cells show erythropoietic stimulating activity. 2. Comparison of the stimulating effects of red blood cell components on erythropoiesis shows that hemoglobin and hemin are active; stroma and globin are not. 3. The following compounds related to heme appear to increase erythropoiesis: compounds containing 4 pyrrole rings connected by methene bridges; an open 4-pyrrole ring configuration, as in biliverdin and bilirubin. The nature of the side-chain groups is not critical for activity; a metal moiety is not essential to activity. 4. Several precursors involved in synthesis of the porphyrin ring, a single pyrrole ring, and cyanocobalamin which has a corrinoid ring structure, did not increase erythropoietic activity.

Protective Effect of Hypoxia against Irradiation Injury of the Rat Bone Marrow and Spleen.

Summary 1. Rats irradiated in a hypoxic atmosphere show a slightly higher cellularity and much greater rate of DNA synthesis in the bone marrow and spleen after 96 hours than rats irradiated at ground level. 2. Thirty hours of intermittent hypoxia preceding irradiation at low oxygen tensions does not give additional protection. 3. A striking parallelism exists in the cellular reactions in the bone marrow and spleen following irradiation, both at normal atmospheric pressures and at low oxygen pressure. 4. Irradiation of animals at low oxygen pressures appears to reduce the biological effectiveness of 800 r on the bone marrow to 600 r.

Erythropoietic Activity of Tissue Homogenates.

Summary Homogenates of rat liver, kidney, brain, spleen and muscle prepared in modified Tyrodes solution and injected into the rat are capable of stimulating erythropoiesis as measured by Fe59 incorporation into red cells and reticulocyte counts. The activity of the homogenates does not appear to be a nonspecific effect. Certain points of similarity are noted between the homogenates and plasma erythropoietin.

Lipogenesis by adipose tissue: Serum stimulating effects

Abstract The in vitro incorporation of [14C]acetate into lipid by rat adipose tissue was investigated. Rabbit, dog, rat and human sera were found to greatly enhance the incorporation of [14C]acetate into lipid by adipose tissue. Evidence is presented that the factors in serum responsible for its stimulatory effect upon lipogenesis are bicarbonate, glucose and free amino acids. The results indicate that those amino acids which enter the citric acid cycle during catabolism stimulate lipogenesis while other amino acids do not. Oxalacetate and succinate have a stimulatory effect upon lipogenesis while fumarate, malate, pyruvate, citrate and a-ketoglutarate have no such effect. Cyanide essentially abolished the lipogenic activity of adipose tissue while arsenate and fluoride reduced the activity approximately 50%. Malonate by itself had no appreciable effect upon lipogenic activity and caused an actual increased incorporation of the labeled acetate into carbon dioxide. In addition, malonate seemed to augment the lipogenesis-stimulating effect of succinate.

Nucleic acid metabolism of bone marrow and spleen. I. Normal values and effect of sodium pentobarbital.

Summary (1) Normal values are presented for the desoxyribose nucleic acid phosphorus and ribose nucleic acid phosphorus as well as the rate of uptake of P32 by the DNA and RNA in the bone marrow and spleen of adult rats. (2) Anesthetic doses of sodium pentobarbital were found to produce a significant decrease in the relative rate of formation of DNA in the bone marrow and spleen during a period of 5 1/2 hours. (3) The significance of these observations is discussed.

Identification of the Serum Fraction Carrying Syphilitic Reagin by Electrophoresis.

Summary 1. Electrophoretic analyses are reported for syphilitic sera, before inactivation by heating to 56°C for 30 minutes, after inactivation, and after inactivation and flocculation with the Kahn antigen. No significant change occurred on inactivation but flocculation with the antigen apparently removes some γ globulin from solution. 2. Electrophoretic analyses and serological reactions of protein fractions obtained by salting out with ammonium sulfate are reported. From the data obtained, the β or γ globulin fractions or both have been identified as carriers of the Kahn and Wassermann reagins.