Influence of predation on species coexistence in Volterra models

The possibility of predator-mediated coexistence of all species in model ecosystems of the Volterra type is discussed, that is, asymptotic behaviors of systems of two competing species are analyzed when one or two predators are added. All species in the communities can coexist in two distinct ways mathematically, that is, the species may coexist at equilibrium or may coexist in persistent oscillations. The stability of all species at equilibrium increases when one or two predators are added. The conditions for oscillatory coexistence in limit cycles or in chaotic behaviors of two-predator systems are more complicated than in those of one-predator systems. It is concluded that predator-mediated coexistence can be promoted by an intimate relationship between the competitive ability of the prey and the diet preference of the predators.     

Effect of high carbohydrate diet on serum gamma-glutamyl transpeptidase fraction pattern in Japanese young men

Changes in the activity of serum gamma-glutamyl transpeptidase (gamma-GTP) and the percentage of the gamma-GTP fraction in healthy young men given a high carbohydrate diet (480-636 g/day, 80% of the total energy) for 21 days were examined. Serum total gamma-GTP activity showed no significant change in four healthy young volunteers who received high carbohydrate diet for 21 days. However, the percentage of the gamma-GTP (1) fraction increased significantly (P less than 0.01) from the basal level of 55.6 +/- 4.0% to 67.6 +/- 0.9% on day 10, and then decreased to 58.4 +/- 1.4% on day 21. When the experimental diet was replaced by usual diet, the percentage of the gamma-GTP (1) fraction returned to the same level as before the experiment. It is concluded from the results that the nutrient intake affects the percentage of gamma-GTP (1), but not the total serum gamma-GTP activity.     

Early replicative intermediates of Escherichia coli chromosome isolated from a membrane complex.

The replication origin region of the Escherichia coli chromosome was isolated from an outer membrane fraction. The chromosome was further purified by centrifugation in a cesium chloride gradient. Early replicative intermediates were enriched in the preparation when cytosine-1-beta-arabinofuranoside was added to the culture at the time of initiation of chromosome replication. DNA fragments with an eye structure having two branches of less than 400-500 bp in length were associated with components that were removed by phenol treatment. We conclude that the replication fork usually proceeds counter-clockwise toward the unc operon in the earliest period of replication.     

Investigation of actin in Tetrahymena cells. A comparison with skeletal muscle actin by a devised two-dimensional gel electrophoresis method

Total protein constituents of Tetrahymena thermophila strain B1868 III were studied by two-dimensional agarose-polyacrylamide gel electrophoresis to detect actin among the constituents. In the attempts to prepare a whole-cell extract of Tetrahymena, it was found that protease activity in the extract was so high that high molecular components were quickly digested with the endogenous protease into small peptides unless the homogenization and heat-treatment in a sodium dodecylsulfate solution were performed within 5 s. It was eventually found that employment of 8 M guanidine hydrochloride (HCl) in the homogenization of cells perfectly prevented the degradation of protein components, even through a long preparation procedure. A devised two-dimensional agarose-polyacrylamide gel electrophoresis of the guanidine HCl extract gave a 'protein map' on which most proteins were located in their respective positions, including proteins with more than 200,000 mol. wt. Addition of rabbit skeletal muscle actin on the protein map revealed that no protein with isoelectric point and molecular weight identical with those of the actin was contained in the whole Tetrahymena extract, suggesting that Tetrahymena actin may have characteristics far different from those of skeletal muscle actin.     

Spirulina ferredoxin-NADP+ reductase. Further characterization with an improved preparation

The preparation procedure for Spirulina ferredoxin-NADP+ reductase (ferredoxin: NADP+ oxidoreductase, EC 1.18.1.2, FNR) was improved by adding protease inhibitors, phenylmethylsulfonylfluoride (PMSF) and EDTA, through the whole process of preparation and by introducing an affinity chromatography step on Blue Sepharose CL-6B. The addition of the inhibitors largely prevented the formation of the minor component (FNR I), and the affinity gel chromatography simplified the preparation process, shortening the exposure period of FNR to proteolysis. However, complete removal of the heterogeneity of FNR found at the amino (N)-terminal region was not achieved even by applying the new method. The affinity chromatography on the Blue Sepharose gel was also effective in purifying spinach FNR. The affinity of this gel for Spirulina FNR was compared with that for the enzyme derived from spinach leaves. The spinach enzyme had a higher affinity than the Spirulina one. Both enzymes showed the highest affinities to Blue Sepharose at 20--30 mM NaCl concentration. The N-terminal sequence analysis revealed that there was 4 forms, which were probably modifications produced by exopeptidase action during the preparation, or even in the living cells. The longest component gave the N-terminal sequence Ala-Lys-Thr-Asp-Ile-Pro-Val-Asn-Ile-Tyr-. The others lacked amino acids successively one by one from the N-terminus. In contrast, the carboxyl(C)-terminal residues of all 4 FNR forms were tyrosine. The probable C-terminal sequence was predicted to be -Trp-His-Val-Gln-Thr-Tyr based on a study of a cyanogen bromide peptide.     

Interferon-alpha in serum and carcinomatous pleural effusion after repeated intrapleural injections of antitumor agents

Pleural effusions and sera of two patients with lung cancer were tested after intrapleural injection of OK-432 as an anticancer drug for IFN-alpha activity by biological assay and for IFN-alpha as an antigen by radioimmunoassay. The titers by radioimmunoassay were fairly consistent with those by biological assay, but were usually higher. In Case 1, IFN-alpha was observed fairly early after administration of OK-432 and only in pleural effusions. In Case 2, induction of IFN-alpha at low level was observed late after the first administration of OK-432 both in the pleural effusion and serum and was detected only by radioimmunoassay.     

A role of the B-oligomer moiety of islet-activating protein, pertussis toxin, in development of the biological effects on intact cells

Islet-activating protein (IAP), pertussis toxin, is an oligomeric protein (Tamura, M., Nogimori, K., Murai, S., Yajima, M., Ito, K., Katada, T., Ui, M., and Ishii, S. (1982) Biochemistry 21, 5516-5522), the biggest subunit (Mr = 28,000, referred to as the A-protomer) of which catalyzes transfer of the ADP-ribose moiety of NAD to the membrane Mr = 41,000 protein. The pentamer, termed the B-oligomer, consisting of the residual subunits was the moiety of IAP that was responsible for binding to the cell surface, as revealed by competitive inhibition of the development of the IAP actions on intact rat C6 glioma cells and rat adipocytes. The binding of the B-oligomer to its receptor proteins was divalent via the constituent two dimers; it stimulated mitosis of lymphocytes and caused an insulin-like action to enhance glucose oxidation in adipocytes, just as did concanavalin A, presumably as a result of cross-linking or aggregation of the membrane proteins. The A-promoter displayed its biological action on adipocytes only when the B-oligomer had been bound to the cells. Thus, IAP is a typical A-B toxin in which the B-oligomer is first bound to the cell surface proteins to enable the A-protomer to reach to the site of its action within the cell. Diverse biological actions of pertussis toxin may be accounted for by the mitogenic action of the B-oligomer as well as ADP-ribosyltransferase activity of the A-promoter.     

Effects of Net and Local Charges on the Interaction between Chemically-Modified Horse Heart Cytochrome c and P700 in Photosystem 1-Enriched Subchloroplast Particles

Effects of salt and pH on the re-reduction of P700 by chemically-modifiedhorse heart cytochrome c after a flash illumination were examinedin Triton-treated P700- enriched subchloroplast particles (TSF-1particles). At low salt concentrations net charges on the membrane surfaceand native, guanidinated or succinylated cytochrome c were majorfactors that determined the reaction rates, as in the reactionbetween plastocyanin and P700 [Tamura et al. (1981) Plant &Cell Physiol. 22: 603]. The reaction rates also depended onreactant-specific factors, particularly the localized distributionof charges on macromolecules and their interaction over shortdistances, as well as on long-range Coulombic interaction. Theeffect of this type became clearer at high salt concentrations. (Received October 7, 1982; Accepted December 20, 1982)