A simple binary solvent method has been developed for the simultaneous determination of creatine (Cr), phosphocreatine (PCr), ATP, ADP, AMP, GTP, GDP, IMP, NAD, inosine, adenosine, hypoxanthine and xanthine. This allows separation of the most important nucleotides present in myocardial biopsies as, for example, in studies using 31P NMR spectroscopy. In NMR spectra ATP and PCr are the only visible high-energy phosphates, therefore the status of other nucleotides and bases cannot be determined. The nucleotides, AMP degradation products, PCr and Cr in pig and rat heart muscle were resolved with 35 mM K2HPO4, 6 mM tetrabutylammonium hydrogensulfate buffer, pH 6.0, and a binary acetonitrile gradient on medium-bore, 250 mm or 125 mm x 3.9-4.6 mm I.D. steel octadecyl-bonded (C18) columns at a flow-rate of 1.5 or 1.0 ml/min. This method, optimized for use with older high-performance liquid chromatography pumps (100 microliters displacement heads), resolves the major porcine and rat myocardial nucleotides and degradation products within 22 min. The amounts found in normoxic porcine muscle are: Cr 9.21 +/- 0.75; hypoxanthine 1.40 +/- 0.14; PCr 7.20 +/- 1.2; IMP 1.34 +/- 0.13; beta NAD 1.82 +/- 0.23; AMP 0.10 +/- 0.04; GDP 0.05 +/- 0.02; ADP 1.23 +/- 0.09; GTP 0.19 +/- 0.01; ATP 4.45 +/- 0.32 mumol/g wet weight. The method, incorporating adenosine tetraphosphate as an internal standard, allows the documentation of changes in both the high-energy phosphates and their degradation products in a single analysis of myocardial samples as small as 200 micrograms (wet weight).

A new hypothesis on carcinogenesis is set forth on the basis of the neighborhood coherence principle (NCP). NCP constitutes a general rule of pattern formation and maintenance. According to this principle, a system of interacting cells can produce and maintain a spatial organization by virtue of cell-cell communication. This hypothesis suggests that this homeostasis primarily results from a NCP-like process implying cell-cell communication. Each cell is constrained by its neighbors to maintain the mature phenotype despite its inherent individual variability. If the cell-cell mature communication happens to be impaired, tissue homeostasis is disrupted and a proliferative state can be initiated. A further potential effect may result from the establishment of NCP-like communication specific for proliferative cells allied to paracrine and outocrine factors which can lock the cells into the proliferative mode. Most mechanisms implied in this hypothesis have already been investigated. There is a large body of experimental results supporting the role of junctional communication in cooperative metabolism, growth, differentiation and tumour-related events. This new hypothesis provides a framework within which these known facts may be put in a theoretical perspective; it might well constitute the unifying theory--as yet missing--in carcinogenesis.

Upon exposure to methylmercury chloride, the whole-cell oxygen uptake by the yeast Saccharomyces cerevisiae ceases. On a fermentable carbon source, carbon dioxide continues to be evolved after respiration has stopped, indicating that fermentation is still active. Dextrose and glycerol uptake also persists until the respective processes, fermentation and respiration, are totally inhibited. Protein and nucleic acid synthesis are blocked with similar concentrations of methylmercury, while cytochrome c, the terminal component of the electron transport chain, is unaltered by the toxicant. Surprisingly, the intracellular ATP is higher in the treated cells than in the controls, although they eventually fall in response to higher concentration or longer exposure. High-pressure liquid chromatography profiles show that the amounts of the other nucleotides are either unaltered or increased. The entire inhibitory process is reversible with time or fresh medium at low methylmercury concentrations. These results do not support the hypothesis expressed by several authors of an inhibition of ATP biosynthesis resulting from membrane perturbation. These data suggest that the decrease in ATP—when induced by the organomercurial—is a secondary process and is not the result of direct mitochondrial toxicity.