THE EFFECT OF dl-METHIONINE, l-CYSTINE, AND dl-ISOLEUCINE ON THE UTILIZATION OF PARENTERALLY ADMINISTERED DOG HEMOGLOBIN : A SUGGESTION FOR DESIGNING THE COMPOSITION OF THE "IDEAL" PROTEIN DIGEST

1. Further observations on the utilization of parenterally administered dog hemoglobin show that oral supplements of dl-methionine and l-cystine improve the efficiency of utilization of hemoglobin N, while a fed supplement of dl-isoleucine alone is without effect. 2. When N-isoleucine is added to a fed supplement of methionine or methionine and cystine, the utilization of parenterally given hemoglobin N is even better than with the sulfur-containing amino acids alone. 3. A suggested approach to the problem of designing the quantitatively "ideal" amino acid mixture lies in the definition of what may be called total organism-amino acid patterns of rat, dog, man, etc. These may vary considerably not only at different developmental stages in a given species, but also certainly from one species to another. 4. Further attempts to detect globin in the peripheral circulation have pointed to the need for a highly specific procedure such as that an immunologic method may offer. 5. Reduced hemin in dog plasma migrates with α₁-globulin and albumin in veronal buffer at pH 8.5 and the colored zones give strong hemochromogen absorption bands.

Effect of methionine, norleucine, and lysine derivatives on cephalosporin C formation in chemically defined media

Demain, A. L. (Merck Sharp & Dohme Research Laboratories, Rahway, N.J.), Joanne F. Newkirk, and D. Hendlin. Effect of methionine, norleucine, and lysine derivatives on cephalosporin C formation in chemically defined media. J. Bacteriol. 85: 339-344. 1963.-Chemically defined media were developed for production of cephalosporin C by Cephalosporium sp. In such media, the requirement for methionine can be satisfied by norleucine. Further stimulation of antibiotic production was obtained with the lysine derivatives epsilon-N-acetyl-l-lysine and epsilon-aminocaproic acid but not with lysine itself. Also inactive were alpha-aminoadipic and ketoadipic acids. Other lysine derivatives were found to inhibit cephalosporin C production at 0.01 m. The final medium supported the production of approximately 0.5 g of cephalosporin C per liter of medium.

Synthesis and migration of proteins in the cells of the exocrine pancreas as revealed by specific activity determination from radioautographs

Radioautographs of pancreatic acinar cells were prepared in rats and mice sacrificed at various times after injection of leucine-, glycine-, or methionine-H³. Measurements of radioactivity concentration (number of silver grains per unit area) and relative protein concentration (by microspectrophotometry of Millon-treated sections) yielded the mean specific activity of proteins in various regions of the acinar cells. The 2 to 5 minute radioautographs as well as the specific activity time curves demonstrate protein synthesis in ergastoplasm. From there, most newly synthesized proteins migrate to and accumulate in the Golgi zone. Then they spread to the whole zymogen region and, finally, enter the excretory ducts. An attempt at estimating turnover times indicated that two classes of proteins are synthesized in the ergastoplasm: "sedentary" with a slow turnover (62.5 hours) and "exportable" with rapid turnover (4.7 minutes). It is estimated that the exportable proteins spend approximately 11.7 minutes in the Golgi zone where they are built up into zymogen granules, and thereafter 36.0 minutes as fully formed zymogen granules, before they are released outside the acinar cell as pancreatic secretion. The mean life span of a zymogen granule in the cell is estimated to be 47.7 minutes.

Labeling with 14C amino acids of albumin-like protein by rat liver ribonucleoprotein particles

Ribonucleoprotein particles were prepared by treatment of rat liver microsomes with detergents and high concentrations of KCl. They were active in incorporating ¹⁴C amino acids into protein when incubated with cell sap together with ATP, GTP, and a system to regenerate the triphosphates. The albumin of the incubation mixture, soluble at 105,000 g, and that of the fraction released by ultrasonication of the particles were studied by immunoelectrophoresis in agar gel. When the ribonucleoprotein particles were incubated with cell sap the immunological precipitation lines formed with antiserum to rat serum albumin were highly radioactive as tested by autoradiography. After zone electrophoresis on cellulose acetate, two immunologically reactive albumins were obtained which differed in their electrophoretic mobility from rat serum albumin. Labeled albumin, when purified on DEAE-cellulose columns, retained its radioactivity as tested by autoradiography following immunoelectrophoresis. On cellulose acetate this purified albumin showed an electrophoretic mobility higher than that of rat serum albumin.

KINETICS OF MATING OF FP+ AND FP- STRAINS OF PSEUDOMONAS AERUGINOSA

Loutit, J. S. (University of Otago, Dunedin, N.Z.), and L. E. Pearce. Kinetics of mating of FP(+) and FP(-) strains of Pseudomonas aeruginosa. J. Bacteriol. 90:425-430. 1965.-Recently, we reported the variability of the FP(+) x FP(-) mating in Pseudomonas aeruginosa, and the increase in efficiency when the cells were mated after dilution. The present work shows that when standardized cells were mated after a dilution of 10(-2) for FP(-) and 2 x 10(-3) for FP(+), there was less variability in the system. Investigation of pairing between FP(+) and FP(-) cells, as measured by genetic transfer, revealed that none took place during 24 hr in liquid media in which growth of both parents was possible. Transfer in liquid minimal medium was not investigated, because the single marker in the male was insufficient to control back mutation in 24 hr. No transfer occurred on solid media which allowed full growth of both FP(+) and FP(-) cells. Transfer took place very slowly on minimal agar, requiring 19 to 20 hr. It is thought that this represents growth of microcolonies with eventual transfer when internal nutrients were exhausted.

CO-2 FORMED FROM ENDOGENOUS AND EXOGENOUS SUBSTRATES IN PERFUSED RAT HEART

Measurements of total CO2 and C14O2 production by the isolated, perfused rat heart showed the extent of respiration dependent on endogenous and exogenous substrates. Glucose, acetate, and palmitate, but not glutamic acid or leucine, contributed appreciably to respiration. With optimal glucose and palmitate oxidation endogenous substrates accounted for over half of CO2. Endogenous substrates were adequate to maintain respiration for 30 but not for 60 min. Dependence of respiration on lipids was suggested by the similarity of metabolic CO2 in glycogen-depleted hearts perfused with no added substrate, with palmitate-1-C14, and with glucose-U-C14 plus palmitate. A reduction in C14O2 and in total CO2 formation with glucose-U-C14 in the presence of palmitate provided further support for the preferential oxidation of fatty acids. The Vo2, estimated from the total and C14O2, and an assumed respiratory quotient, indicated adequate oxygenation of the heart in the closed recirculated system. The necessity of maintaining an adequate coronary artery flow rate was indicated by an altered pattern of cell metabolism in hearts with reduced coronary perfusion.