Potassium requirement for cell division in Anacystis nidulans

Allometry (scaling) of blood components in mammals: connection with economy of energy?

Hematocrit (HCT), blood hemoglobin (HGB), and serum concentrations of 14 commonly measured serum constituents in mammals were extracted from 131 publications published within the last 35 years and then subjected to allometric study (Y = aWb, where Y is the characteristic studied, W is body mass, and b is the scaling exponent). HCT and HGB values decreased (b < 0; p < 0.001) with body mass (W), as did serum K+, glucose, triglycerides, and urea values. In contrast, serum total protein and creatinine values increased (b > 0; p < 0.02 and p < 0.001, respectively) with W. The associations of HCT, HGB, glucose, triglycerides, and urea values with W may be assumed to coincide with the well-known reduction of metabolic rate per unit mass with increasing W of mammals. The decrease in serum K+values (p < 0.001) has yet to be adequately explained. Despite the ratio of muscle mass and W being constant for large and small mammals, serum values of creatinine rose (b = 0.14; p < 0.0001) with W. This suggests increased phosphocreatine turnover in muscles with W, which in turn might be connected to the increased efficiency reported for leg muscles in larger animals and, conceivably, might affect the measurement of metabolic rate and hence its scaling in mammals.

Mechanism of lysis of Escherichia coli by ethanol and other chaotropic agents

Ethanol has been shown to inhibit the assembly of cross-linked peptidoglycan and to induce cell lysis in Escherichia coli. These effects of ethanol appear to result from the weakening of hydrophobic interactions by ethanol rather than from the intercalation of ethanol into membranes. Other chaotropic agents also inhibited cross-linking and induced lysis. The potency of chaotropic anions with regard to this effect followed the expected chaotropic series. Antichaotropic agents, which strengthened hydrophobic interactions, antagonized ethanol-induced lysis. The weakening of hydrophobic interactions by ethanol is proposed as a general mechanism by which ethanol and other chaotropic agents could affect membrane-associated enzyme activities.

Regulation of ornithine decarboxylase activity by guanine nucleotides: in vivo test in potassium-depleted Escherichia coli

The observation that guanosine 5'-triphosphate (GTP) is an activator and guanosine 5'-diphosphate-3'-diphosphate (ppGpp) is an inhibitor of ornithine decarboxylase (L-ornithine carboxy-lyase, EC 4.1.1.17) of Escherichia coli [E. Hölttä et al. (1974) Biochem. Biophys. Res. Commun. 59, 1104-1111] has been confirmed. The hypothesis that synthesis of both polyamine and RNA in E. coli is regulated in vivo by these nucleotides was tested in E. coli B-207. On transfer of this K+-requiring, amino-acid-deficient strigent strain from K+-medium to Na+-medium, the organism stops protein synthesis, maintains a high rate of RNA synthesis, and increases putrescine synthesis from ornithine manyfold. Under these conditions, the cells do not markedly change their contents of GTP and ppGpp. The proposed mechanism of regulation of RNA and putrescine synthesis by guanine nucleotides does not appear to explain the metabolic phenomena observed in this organism during K+ deficiency. Nevertheless, amino acid depletion in K+-medium does result in a marked increase in ppGpp.