Edwin T. Mertz

Plasminogen: Purification from Human Plasma by Affinity Chromatography

Plasminogen was prepared from human plasma by affinity chromatography on L-lysine-substituted Sepharose. Thirty milligrams of plasminogen, with a specific activity of 100 caseinolytic units (Committee on Thrombolytic Agents) per milligram of nitrogen, were obtained from 340 milliliters of plasma. This corresponds to over 200-fold purification from plasma. Disc-gel electrophoresis at pH 8.3 indicated seven distinct bands, all of which contained activity.

Mutant Gene That Changes Protein Composition and Increases Lysine Content of Maize Endosperm

Preliminary tests have shown that the endosperms of maize seeds homozygous for the opaque-2 mutant gene have a higher lysine content than normal kernels. As a critical test, a backcross progeny was divided into opaque-2 and normal kernels, the endosperms separated, and the amino acids determined. The opaque-2 endosperms had a different amino acid pattern and 69 percent more lysine than the normal seeds. The major reason for these changes is the synthesis of proteins with a greater content of basic amino acids in the acid-soluble fraction of the mutant endosperm. This is accompanied by a reduction in the ratio of zein to glutelin.

Second Mutant Gene Affecting the Amino Acid Pattern of Maize Endosperm Proteins

The mutant floury-2 results in the production of maize endosperm proteins with an altered amino acid pattern. The lysine concentration is high, eapproximately equal to that in mutant opaque-2, and the methionine concentration is higher than in any other stock tested. Other mutants of similar phenotype!, opaque-1, floury-1, and soft-starch do not cause major changes in amino acid Pattern.

Endosperm Protein Synthesis in Maize Mutants with Increased Lysine Content

The endosperm proteins of the maize mutants, opaque-2, opaque-7, floury-2, brittle-2, and the double mutant of opaque-2 and brittle-2, were separated into five soluble fractions by the Landry-Moureaux method. As compared to their isogenic normal counterparts, the mutant endosperms had higher concentrations of albumins, globulins, and glutelin-3, and lower concentrations of prolamines. The combination of the opaque-2 and brittle-2 genes enhanced this difference. Although the four mutant genes are located on three different chromosomes, they exert a similar effect on endosperm protein composition. Five other starchmodifying mutants with high lysine content resemble the brittle-2 mutant in endosperm protein composition, when the gene is present either singly or combined with opaque-2. Therefore, the pattern of protein synthesis in all maize mutants with high lysine concentrations may be either identical or very similar. Because no synergistic effect on lysine concentration is obtained when floury-2 is combined with opaque-2, different pathways leading to reduced zein synthesis may exist in the floury and starch-modifying mutants with high lysine concentrations.

Growth of Rats Fed on Opaque-2 Maize.

Six weanling male rats were fed a diet containing 90 percent opaque-2 maize for 28 days. The average gain in weight was 97 grams. In control rats fed on a standard hybrid maize the average gain was 27 grams. This confirms results of a previous feeding test on rats and demonstrates the superior quality of the proteins in opaque-2 mutant endosperm.

Classification of essential amino acids for the weanling pig.

Abstract Feeding experiments with mixtures of purified amino acids show that arginine, leucine, phenylalanine, and valine are required for good growth of weanling pigs. The pig resembles the rat in its ability to synthesize part, but not all of the arginine required. It is now possible to tentatively classify the known amino acids with respect to major growth effects in weanling pigs. The amino acids which must be present in the diet for good growth are arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan , and valine . The remaining amino acids may be tentatively classed as dispensable.

Effect of restricted food intake on growth and composition of preweanling rat brain.

Summary Food intake of Wistar rats was restricted from 5 until 20 days of age such that body weight gain was approximately 20% of the ad libitum fed control rats. The incorporation of nonlipid solids, cholesterol, phospholipids and cerebrosides into the brain was reduced by restricting food intake.

Serum Uric Acid in Mongolism

A highly significant increase (P < .01) in average uric acid level was found in the blood serum of mongoloids when levels were compared with those in normal control subjects or nonmongoloid, mentally retarded subjects. The possible relationship of these findings to other abnormalities known to exist in mongolism is discussed.

Imidazole Buffer Its Use in Blood Clotting Studies.

Summary Mixtures of imidazole and hydrochloric acid covering the pH range 6.2 to 7.8 are described. These mixtures are recommended as buffers for reactions which require the presence of calcium ion.

Effect of a Tryptophan Deficient Diet on Brain Serotonin and Plasma Tryptophan Level.

Summary One hundred and eight female Wistar rats were placed on tryptophan sufficient or tryptophan deficient diets. Six animals from each group were sacrificed after 2 days, 4 days and multiples of 4 days. Plasma tryptophan level was found to reflect changes in brain serotonin level. Furthermore, plasma tryptophan and brain serotonin were significantly decreased after as little as 4 days on the tryptophan deficient diet. The levels of plasma tryptophan and brain serotonin were relatively constant from 4 to 28 days, at which time both showed further decreases.