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.

ELECTROPHORETIC EVIDENCE FOR ISOZYMES OF ARYLAMIDASE ("AMINOPEPTIDASE") IN THE RAT. I. RENAL, SERUM AND URINARY ENZYMES SPLITTING DL-ALANYL-2-NAPHTHYLAMIDE AND L-LEUCYL-2-NAPHTHYLAMIDE

Bilateral nephrectomy elicited no changes of serum blood levels of arylamidase assayed with two chromogenic substrates (l-leucyl-2-naphthylamide and dl-alanyl-2-naphthylamide) two days after the operation. Since rat urine contains similar enzymes it was postulated that the urinary enzyme is of renal origin and distinct from serum arylamidase. For this purpose, electrophoretic studies were undertaken. Starch block (for quantitative determinations) and starch gel for zymograms of arylamidase were used. It was shown that both procedures demonstrated the identity of urinary and renal arylamidase, which was distinct from the serum enzyme. The renal and urinary enzyme showed two distinct isozymes: one remaining at the origin and the other migrating somewhat less than the isozyme in serum. It is postulated that the isozyme remaining at the origin corresponds to a membrane-bound form, whereas the electrophoretically-mobile isozyme is found in the cellular supernatant fraction. The arylamidase from serum was represented by a single enzyme which migrated farthest towards the anode.

Histochemical procedures for the demonstration of arylamidase activity in tissues at the light microscopic level permit the localization of enzyme(s) that can hydrolyze synthetic chromogenic naphthylamides containing l-leucyl and dl-alanyl groups (1).

Rat kidneys have a high concentration of histochemically demonstrable arylamidase in the proximal convoluted tubules (2). Blood levels of arylamidase in the normal adult rat vary within a narrow range (3). The observation of arylamidase activity in rat urine raised several questions that led to the studies which are the basis of the present report.

The relationship of serum and urinary arylamidase was the starting point of this investigation. It was speculated that if the urinary enzyme had its origin in the serum, bilateral nephrectomy should alter blood levels of the enzyme. If no such changes occurred, this would suggest that the urinary enzyme was released from the proximal convoluted tubule. In fact, total renal ablation led to no significant variation of serum arylamidase activity.

It was therefore postulated that urinary arylamidase originated in the kidneys and that both are distinct from serum arylamidase. To test this hypothesis, zone electrophoretic studies were undertaken using two different supporting media. It will be shown that distinct molecular forms or isozymes of arylamidase can be separated from rat tissues and fluids by differential electrophoretic mobility. The electrophoretic identity of urinary and renal arylamidase, both of which are distinct from the serum arylamidase, is demonstrated in this study.

TRANSFER OF EPISOMIC ELEMENTS TO PROTEUS. II. NATURE OF LAC+ PROTEUS STRAINS ISOLATED FROM CLINICAL SPECIMENS

Falkow, Stanley (Walter Reed Army Institute of Research, Washington, D.C.), J. A. Wohlhieter, R. V. Citarella, and L. S. Baron. Transfer of episomic elements to Proteus. II. Nature of lac(+)Proteus strains isolated from clinical specimens. J. Bacteriol. 88:1598-1601. 1964.-Strains of Proteus mirabilis exhibiting the unusual property of utilizing lactose (lac(+)) have been reported in clinical material. A genetic examination discloses that the lac(+) determinants in these Proteus strains are associated with an infectious element, P, which is distinct from the sex factor of Escherichia coli K-12. The composite genetic element, P-lac, is readily transmissible to other enteric species and possesses properties which conform to those of an episomic element of the transfer variety. CsCl density-gradient studies of deoxyribonucleic acid (DNA) extracted from lac(+)P. mirabilis indicate that the P-lac(+) element did not arise in this species, but was acquired from an organism possessing a markedly different DNA base composition.

PEPTIDE SYNTHESIS FROM AMINO ACIDS IN AQUEOUS SOLUTION

Four dipeptides and a tripeptide were formed when an aqueous solution of glycine and leucine was exposed to ultraviolet light in the presence of cyanamide.

THE RELATION BETWEEN THE INTRACELLULAR RIBONUCLEIC ACID DISTRIBUTION AND AMINO ACID INCORPORATION IN THE LIVER OF THE DEVELOPING CHICK EMBRYO

The RNA-P and DNA-P content of the nucleus and the RNA-P content of the whole cell of the livers of 8- to 20-day chick embryos and of adult fowls have been determined. The DNA-P content of the liver nuclei was slightly higher in the 8- and 10-day embryo than in all the other stages examined. A significant decrease in the RNA content of the cell occurred during embryonic development. The RNA content of the adult cell was the same as that of the 14- to 16-day embryo. The proportion of the cellular RNA contributed by the nucleus also decreased during development. In respect to both nuclear RNA content and distribution of RNA between nucleus and cytoplasm, the adult resembled the 8- to 12-day embryo. Examination of the fine structure of the cell showed that, as development progressed, free ribosomes decreased in number and the rough membranes increased. Slices of 8-, 14-, and 20-day embryonic livers and of adult livers were incubated with ¹⁴C-leucine, and the amount of labeled amino acid incorporated into whole tissue protein and into the proteins of the subcellular fractions was measured. Embryonic liver incorporated ¹⁴C-leucine 15 to 30 times more rapidly than adult liver. The microsomal protein was always more highly labelled than the protein in any other subcellular fraction; however, in the 8-day embryonic and the adult liver the proportion of total counts found in the nuclear fraction was considerably higher than in the 14- or 20-day embryonic liver. The significance of an apparent correlation between the proportion of the cell's RNA contributed by the nucleus and the proportion of total counts in the nuclear fraction is discussed.