The laparoscopic approach to secondary lumbar hernia repair is more efficient and more profitable than the traditional open technique.

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Ligaria cuneifolia (R. et P.) Tiegh (Loranthaceae) is an hemiparasite species widely distributed in several provinces of Argentina. It has been commonly used in folk medicine as a substitute of the European mistetloe (Viscum album L.) based on its putative depressive effect on high blood pressure. In this paper the anatomical features as well as micromolecular and macromolecular analysis of this species are reported. Anatomical study has shown that the main characteristic is the presence of crystalliferous branched stone cells in leaves and stems. The analysis of flavonoids showed that only glycosylated quercetin and proanthocyanidins (whose monomer is cyanidin) are present, indicating a distinctive metabolic pathway. SDS-PAGE analysis evidenced a protein pattern with components ranging from 14 to 90 kD molecular weights. Antiserum against Ligaria cuneifolia was prepared in mice and its immunogenic ability was evidenced by Ouchterlony and Western-blot assays. The results presented are part of a comprehensive ongoing project on Argentine hemiparasite species, which may also be applied to quality control of commercial samples in order to detect the substitution of Viscum album by Ligaria cuneifolia.

Incorporation of 32P into Saccharomyces cerevisiae isocitrate lyase was observed after addition of glucose to a culture incubated with [32P]orthophosphoric acid. A band of 32P-labelled protein was coincident with the enzyme band when immunoprecipitates were subjected to SDS-PAGE and autoradiography. No label was found in the band corresponding to the isocitrate lyase when immunoprecipitation was done with a control pre-immune serum or in the presence of excess pure unlabelled enzyme. The incorporation of phosphate was associated with a decrease in enzyme activity. Phosphorylated isocitrate lyase was not proteolytically degraded when cells were cultured in mineral medium. The loss of protein antigenicity only took place when the yeast was grown in a complex medium containing glucose.

Hexokinase PI1 is not inhibited by high Mg-ATP concentrations if the MgZ+-free ATP is kept at low levels (0.01 mM) in the assay mixture. Hexokinase PI activity is not affected either by Mg2+-free ATP nor by free Mg2+ in the assay mixture. Thus, hexokinase PI and PI1 activities appear not to be regulated by substrate inhibition as proposed previously [Kopetzki, E. & Entian, K. D. (1985) Eur. J. Biochem. 146,657-6621. However, the level of Mg2+-free ATP in the hexokinase PI1 assay mixture strongly affects the enzyme activity by decreasing the V,,, and increasing the K , value for Mg-ATP from 0.15 mM to 5.0 mM.The physiological role of this inhibition, which has not been described previously, was investigated by determining the cytosolic ATP and Mg2 This free ATP concentration would lead to a maximal inhibition of hexokinase PII.Three glucose-phosphorylating enzymes, glucokinase and two hexokinase isoenzymes PI and PII, have been described in yeasts [l ,2]. The physiological role of these enzymes remains unclear. One of them is sufficient for growth on glucose, and either one of the two hexokinases for growth on fructose. In the last few years, special attention has been given to hexokinase PII; it has been described as an enzyme with both catalytic and regulatory properties [3 -51.Hexokinase PI1 can be inactivated by addition Of D-XylOSe to the culture medium, in which case the growth rate as well as rate of glucose consumption are similar to yeasts grown without D-xylose [5, 61. These results indicate that hexokinase PI1 is not essential for glucose phosphorylation. However, catabolic repression of invertase and maltase was relieved in yeast with xylose-inactivated hexokinase PI1 [5] and by a mutation in the hexokinase PI1 structural gene (hex 1) [A. This suggested a direct role of hexokinase PI1 in carbon catabolite repression of invertase and maltase. This hypothesis is supported by the isolation of nonrepressible mutants (hex lr) which were only defective in the regulatory domain with the hexokinase PI1 enzyme still active catalytically [8]. In such mutants the defect in catabolite repression was due to the defective hexokinase PI1 but independent of the capacity for glucose phosphorylation.The interaction between hexokinase PI1 and an unknown signal mediating catabolite repression could produce a conformational change of the enzyme triggering derepression. The detailed molecular mechanism is unknown at the moment. Catabolite repression in cells being transferred from a non-repressing ethanol medium to a repressing glucose medium, does not depend on the accumulation of glycolytic or Krebs cycle intermediates [5, 91.Recently, both hexokinase isoenzymes were described to be strongly inhibited by high physiological concentrations of ATP (2mM) [lo]. Our results suggest that the substrate inhibition of hexokinase PI1 is produced by the Mg2+-free ATP accumulation in the assay mixture. This paper describes the strong decrease in the concentration of magnesium ions in the cytosol of cells being transferred from a repr...