Effect of theophylline and theobromine on cell respiration and calcium transport in isolated rat liver mitochondria

The influence of theophylline and theobromine on cellular respiration and on membrane transport of calcium has been studied in isolated rat liver mitochondria, using oxygen and Ca2+ selective electrodes. A linear decrease in respiratory coefficients, in the total amount and rate of "extra" oxygen consumption induced by ADP is observed with drug concentration. Theobromine does not show any appreciable effect on these respiratory parameters, but this result is similar to that observed with theophylline for the same concentration range. Calcium uptake coupled to respiration is inhibited by both drugs depending on their concentrations. Theobromine is more effective than theophylline. Calcium saturation of the mitochondria takes place in all cases after 36 +/- 2 s but only a 20% of the maximum calcium uptake observed in the absence of the drugs is determined in the presence of 15 mM theophylline or only 1.8 mM theobromine. Comparative studies show direct correlation between the pharmacological activities as stimulants of caffeine, theophylline and theobromine and their behaviour as inhibitors of calcium uptake coupled to respiration by mitochondria.     

Antilipolytic activity in vitro of various analogs of nicotinic acid. Structure-activity relationship

The antilipolytic activity of a series of N aryl-nicotinamides and of alpha picolinic acid, has been tested in vitro. Lipolysis was stimulated by epinephrine (20 micrograms/ml of incubation medium) using rat's epididymal adipose tissue slices. Only N(2-carboxy methyl phenyl) nicotinamide showed antilipolytic effect comparable to that of nicotinic acid at similar concentrations (2 X 10(-5) M). Picolinic acid (10(-4) M) showed no antilipolytic effect. These results, together with those of the literature, are discussed in regard to the relations between structure and antilipolytic activity.     

Effects of salicylate on insulin and glucagon secretion by the isolated and perfused rat pancreas

The effects of sodium salicylate, a prostaglandin synthesis inhibitor, on glucose-induced secretion of insulin and glucagon by the isolated perfused rat pancreas have been studied. Sodium salicylate inhibited both basal (2.8 mM glucose) and stimulated (16.7 mM glucose) insulin release in a dose dependent manner (1, 5 and 10 mM). This inhibition is not interpretable in terms of a simple inhibition of cyclooxygenase by sodium salicylate. Basal glucagon release was not changed by 1 mM sodium salicylate but the latter partially blocked its inhibition by 16.7 mM glucose. Higher doses of sodium salicylate (5 and 10 mM) inhibited basal glucagon secretion without affecting its response to 16.7 mM glucose. These findings suggest a predominant stimulatory action of endogenous prostaglandins on glucagon release.     

Incorporation of (U-14C)-glucose into glycogen in normal rat pancreatic islets

The incorporation of glucose into glycogen was determined in pancreatic islets isolated from normal rats and incubated with glucose (5 or 20 mM) and compounds known to affect glycogen metabolism in other tissues. Incubation of pancreatic islets with glucose (20 mM) induced a marked increase in radioactive glycogen. Exposure to epinephrine in the presence of glucose (20 mM) slightly increased incorporation of glucose into glycogen. In contrast the incorporation of glucose into glycogen was not affected when isolated islets were exposed to glucagon or insulin, whereas anti-insulin serum in the incubation medium decreased radioactive glycogen formation.     

Possible effect of bromocriptine on the insulin receptor

The administration of 0.00011 mg/g weight/day of bromocriptine (CB154) for 7 days to Wistar rats, improved the peripheral glucose uptake without significant changes in plasma insulin level, during the intravenous glucose tolerance test (0.33 g/kg). The mode of the bromocriptine action on binding of 125I insulin to erythrocyte insulin receptors has been evaluated. The total number of sites was greater with bromocriptine (513.1 +/- 124.1 pM/1,CB154 815.6 +/- 107.9 pM/l) (p less than 0.01). The high affinity/low capacity compound of insulin receptor, in CB154 rats (51.8 +/- 16.8 pM/l) was higher than in normal rats (18.3 +/- 8.9 pM/l) (p less than 0.005). Additional studies indicated that CB154 had no effect on the rate of association and dissociation of 125I insulin from rats erythrocyte insulin receptors. The degradation of insulin or the erythrocyte receptor sites do not change, after the treatment with CB154.     

Effects of divalent cations and functionally related substances on the yeast to mycelium transition in Sporothrix schenckii

In a minimal basal medium with glucose at pH 4.0 and 25 degrees C, a lowering of the magnesium and zinc concentrations or increase in the calcium concentration of the medium favoured the yeast-mycelium transition in Sporothrix schenckii. Addition of zinc (1 and 10 mM) inhibited mycelial development and induced reversion to a yeast-like morphology. EDTA and EGTA also delayed germ tube formation, possibly by their calcium-chelating effects or by altering intracellular concentrations of this or other ions. Ionophore X537A also caused a delay in germ tube formation, possibly by interfering with magnesium metabolism in these cells.     

Phospholipid methylation in pancreatic islets

Glucose provokes a transient stimulation of phospholipid methylation in rat pancreatic islets, possibly by increasing phospholipid methyltransferase activity. The association of DL-homocysteine and 3-deazaadenosine inhibits phospholipid methylation. The methylation of phospholipids may play a role in the stimulus-secretion coupling for glucose-induced insulin release.     

Structural characterization of a higher plant calmodulin : spinacia oleracea

Calmodulin is a eukaryotic calcium binding protein which has several calcium-dependent in vitro activities. Presented in this report is a structural characterization of calmodulin from spinach leaves (Spinacia oleracea). Spinach calmodulin may be representative of higher plant calmodulins in general since calmodulin from the monocotyledon barley (Hordeum vulgare) is indistinguishable by a variety of physical, chemical, and functional criteria (Schleicher, Lukas, Watterson 1983 Plant Physiol 73: 666-670). Spinach calmodulin is homologous to bovine brain calmodulin with only 13 identified amino acid sequence differences, excluding a blocked NH₂-terminal tripeptide whose sequence has not been elucidated. Two extended regions of sequence identity are in the NH₂-terminal half of the molecule, while nine of the 13 identified differences are in the COOH-terminal half of the molecule. Two of the changes, a cysteine at residue 26 and a glutamine at residue 96, require a minimum of two base changes in the nucleotide codons. Both of these changes occur in the proposed calcium binding loops of the molecule. Five additional amino acid differences found in spinach calmodulin had not been observed previously in a calmodulin. As described in an accompanying report (Roberts, Burgess, Watterson 1984 Plant Physiol 75: 796-798), these limited number of amino acid sequence variations appear to result in differential effects on the activation of calmodulin-dependent enzymes by plant and vertebrate calmodulins.     

Fractionation of the gene-size macronuclear chromatin fragments of the binucleated eukaryote Oxytricha

Summary The macronuclear chromatin of Oxytrichia nova consists of chromatin fragments which are fully soluble in 0.2 mM EDTA and whose DNA length varies from 500–25 000 bp. The DNA migrates electrophoretically as a series of discrete bands, with specific genes present in only one or a few bands. The chromatin fragments are composed of nucleosomes and migrate electrophoretically in proportion to their DNA length. These results suggest schemes for the fractionation of undigested chromatin in order to enrich for specific genes, facilitating analysis of changes in chromatin structure associated with changes in gene expression.     

Five new filamentous,glucose-fermenting Candida isolated from decayed wood in the evergreen rainy Valdivian forest of southern Chile

Five novel representatives of the yeast genus Candida isolated from advanced stages of wood degradation from fallen trunks of Eucryphia cordifolia Cav., Laurelia sempervirens Weim., Laurelia philippiana Weim., Nothofagus dombeyii (Mirb.) Blume, and Nothofagus obliqua (Mirb.) Blume, in the evergreen rainy Valdivian forest of southern Chile, are described and illustrated. They clearly differ from all accepted Candida species to warrant their establishment as five new species of yeasts: Candida coipomensis sp. nov., Candida ralunensis sp. nov., Candida laureliae sp. nov., Candida osornensis sp. nov., and Candida llanquihuensis sp. nov.