Entomopathogenous fungi degrade epicuticular hydrocarbons of Triatoma infestans

Studies were undertaken to analyze the ability of entomopathogenous fungi to degrade insect hydrocarbons. Strains of Beauveria bassiana and Metarhizium anisopliae pathogenic to the blood-sucking bug Triatoma infestans were grown on hydrocarbon and non-hydrocarbon insect lipid extracts and on synthetic hydrocarbon-enriched media as the sole carbon source. Entomopathogenous fungi were shown to utilize hydrocarbons as the only carbon source for their growth. Insect-derived hydrocarbons served more efficiently as metabolic fuel rather than synthetic compounds of similar structure. [3H]n-Pentacosane, [11,12-3H]3,11-dimethylnonacosane, and [14C]n-hexadecane were catabolized into different amounts of polar lipids, free fatty acids, and acylglycerols. In experiments using the branched alkane, labeled hydrocarbons of different chain length than the precursor were also synthesized. Evidence of complete catabolism was obtained by a significant release of 14CO2 from [1-14C]n-hexadecane. 14CO2 production might be used as a simple method to compare hydrocarbon utilization by fungal strains. These data demonstrate that entomopathogenous fungi are able to transform a variety of hydrocarbon structures into different lipid products, part of which may be subsequently utilized for energy production and for the biosynthesis of cellular components. These data are the first evidence of hydrocarbon catabolism and synthesis in entomopathogenous fungi.

Characteristics of ryanodine-induced tetani in the perfused rat heart. Tetanic tension is not the highest force that cardiac muscle can generate

The aim of the present study was to elucidate the conditions required to obtain tetanic contractions in rat intact heart and to investigate whether tetanic tension was actually the maximal tension that isolated rat heart is able to generate. Experiments were performed on isolated rat hearts (Langendorff technique) perfused at constant coronary flow (8-9 ml/min). Rapid repetitive stimulation (400 to 3000 pulses/min) failed to elicit a fused tetanus. The first twitch that occurred at the end of the rapid stimulation period was a potentiated beat (PSP) of significantly greater magnitude than that of the regular twitch. This potentiation declined in successive beats. When rapid electrical stimulation (600 to 3000 pulses/min) was applied to hearts treated with 5 x 10(-6) M ryanodine, the result was a fused and steady tetanic tension. Ryanodine suppressed PSP. Tetanic tension could be graded by stepwise increase of [Ca2+]o from 0.25 to 5 mM. Maximal tetanic tension occurred at a [Ca2+]o between 3.85 and 5 mM. At any of the [Ca2+]o, tetanic tension was significantly greater than the tension of the twitch obtained at approximately the natural frequency of rat heart in the intact animal (250 beats/min) but it did not differ significantly from the twitch obtained at 100 beats/min. Moreover, the tension of PSP at 0.25 and 1.35 mM [Ca2+]o was significantly greater than the maximal tetanic tension that could be obtained. Similar results to that obtained with ryanodine, were obtained in additional experiments in which caffeine was used to evoke tetanic contraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphorylation of phospholamban in the intact heart. A study on the physiological role of the Ca(2+)-calmodulin-dependent protein kinase system

The aim of the present study was to further elucidate the physiological role of the calcium-calmodulin (Ca(2+)-Cm)-dependent protein kinase system on phospholamban phosphorylation in the intact functioning heart. The effect of increasing extracellular calcium concentration [Ca]o on phospholamban phosphorylation (PHPL) was studied under different experimental conditions: (a) regular twitches and ryanodine induced-tetani both in the presence and in the absence of 3 x 10(-8) M isoproterenol and (b) Post-stimulation potentiation (PSP), i.e. the potentiation of contractility that follows a period of rapid repetitive stimulation. In the regular twitch, the increase in [Ca]o enhanced contractility both, in the absence and in the presence of beta-stimulation without changing basal or isoproterenol stimulated cAMP levels respectively. This increase in contractility was accompanied by a significant enhancement of PHPL-from 90.6 +/- 16.4 to 216 +/- 35.2 pmols 32Pi/mg protein at 0.25 and 3.85 mM [Ca]o respectively-only when isoproterenol was present. The calmodulin antagonist W-7 significantly decreased the isoproterenol-induced phosphorylation of phospholamban at [Ca]o 1.35 mM. Similar results were obtained under tetanic conditions. When myocardial contractility was enhanced by PSP up to ten-times with respect to the regular twitch, no detectable effect in PHPL was observed. Indirect evidence obtained from skinned rat cardiac trabeculae suggested that the failure of the cAMP-independent mechanisms to phosphorylate phospholamban is not related to a deficient increase in intracellular calcium. The results support the notion that the increase in intracellular calcium induces an increase in PHPL only at high intracellular cAMP levels.

Decrease in tetanic tension elicited by beta-adrenergic stimulation

The effect of beta-adrenergic stimulation on tetanic tension (TT), maximal rate of rise of tension (+TT) and phospholamban (PHL) phosphorylation were studied in the perfused rat heart. 3 x 10(-8) M isoproterenol perfused at different [Ca2+]o 0.25, 1.35 and 3.85 mM, significantly decreased TT while increased +TT and PHL phosphorylation at the three [Ca2+]o studied. Regression lines of the relationship between +TT and TT from individual data obtained at each [Ca2+]o in the presence and in the absence of isoproterenol, show that for the same level of +TT, TT is lower in the presence of isoproterenol, i.e. at high levels of PHL phosphorylation. The slopes of the lines were 0.137 s and 0.427 s (P less than 0.05) in the presence and absence of isoproterenol respectively. The decrease in TT produced by the beta-agonist can be attributed to its relaxant action prevailing over its inotropic effect and may represent the mechanical expression of the enhanced phosphorylation of phospholamban.

Synthesis, purification and conformational studies on enkephalin derivatives containing gamma-amino-n-butyric acid

The solid-phase synthesis of several analogs of enkephalin containing gamma-amino-butyric acid is reported. Synthetic strategies, purification methods, chemical and physicochemical characterization are discussed. The n.m.r. data suggest for some of the analogs structural features similar to the opioids.

Evidence on the existence of a purine ligand induced conformational change in the active site of bovine pancreatic ribonuclease A studied by proton nuclear magnetic resonance spectroscopy

The titration curves of the C-2 histidine protons of RNase A and of derivative II--a covalent derivative obtained by reaction of the enzyme with the halogenated nucleotide 9-beta-D-ribofuranosyl-6-chloropurine 5'-phosphate--in the presence of a number of purine nucleosides, nucleoside monophosphates, and nucleoside diphosphates were studied by means of proton nuclear magnetic resonance at 270 MHz. The examination of the perturbations found on the chemical shifts and pKs of the C-2 protons of His-12, -48, and -119 are consistent with the following conclusions: (1) The interaction of adenosine in the primary purine binding site of the enzyme (B2R2) induces a conformational change in the active center of the enzyme [for the nomenclature of the RNase A binding subsites, see Parés et al. [Parés, X., Llorens, R., Arús, C., & Cuchillo, C. M. (1980) Eur. J. Biochem. 105, 571-579]]. (2) The phosphate moiety of the ligands, independently of its position, probably acts as a general carrier of the nucleotide to the active center, while the substituents of the base are the generators of the specificity of the binding and control the binding equilibrium between subsites B2R2 and B1R1. (3) There is no overlapping between the binding sites occupied by the labeling nucleotide in derivative II (B3R3p2) and the primary binding site for purine mononucleotides (B2R2p1).

Nuclear magnetic resonance of protamines. A 13C relaxation study of the three main fractions of clupeine

The three main fractions of clupeine, the protamine extracted from herring sperm, have been investigated by 13C nuclear magnetic resonance techniques. The dynamic behaviour, examined through the evaluation of the spin lattice relaxation times (T1) of individual carbon resonances assigned to both backbone and side chains, reveals interesting features. The relaxation times of backbone alpha-carbons, interpreted on the basis of an axially symmetric ellipsoid, point to the clupeine fractions as being essentially extended in aqueous solution. These times remain constant along the polypeptide chain and are of the order of 0.16 +/- 0.02 s. Conversely, the side chains show different flexibilities in the presence of monophosphate counterions, thus demonstrating a diverging behaviour which may be biologically relevant. In particular, the side-chain flexibilities of fraction YI decrease, while those of fractions Z and YII are either constant or increase. Comparison of these data with the viscosity measurements helps in explaining the viscosity changes observed in the presence of phosphate.

1H-NMR studies on the binding subsites of bovine pancreatic ribonuclease A

The titration curves of the C-2 histidine protons of an RNAase derivative (a covalent derivative obtained by reaction of bovine pancreatic RNAase A (EC 3.1.27.5) with 6-chloropurine 9-beta-D-ribofuranosyl 5'-monophosphate) were studied by means of 1H-NMR spectroscopy at 270 MHz. The interaction of natural (5'AMP, 5'GMP, 5'IMP) and halogenated purine mononucleotides (cl6RMP, br8AMP) with RNAase A was also monitored by using the same technique. The slight change observed in the pK values of the active centre histidine residues of the RNAase derivative, with respect to those in the native enzyme, can be considered as evidence that the phosphate of the label does not interact directly either with His-12 or 119 in the p1 site, but the p2 site as proposed previously (Parés, X., Llorens, R., Arús, C. and Cuchillo, C.M. (1980) Eur. J. Biochem. 105, 571--579). Lys-7 and/or Arg-10 are proposed as part of the p2 phosphate-binding subsite. The pK values of His-12 and 119 and the shift of an aromatic resonance of the native enzyme found on interaction with some purine nucleotides, can be interpreted by postulating that the interaction of 5'AMP, 5'GMP and 5'IMP takes place not only in the so-called purine-binding site B2R2p1 but also in the primary pyrimidine-binding site B1R1 and p0 of RNAase A.

[Use of contraceptives by a Brazilian population]

Um grupo de 245 mulheres moradoras em Mogi das Cruzes (Estado de S. Paulo, Brasil) foi questionado com relação ao uso de anticoncepcionais, história obstétrica, mortalidade infantil e atitudes correlacionadas com a limitação da natalidade. As respostas foram classificadas segundo idade e nível de renda da informante. Apenas 49% das mulheres empregavam medidas anticoncepcionais, das quais 42% recorriam aos anovulatórios. Esta prática era mais freqüente entre as mulheres jovens, e aquelas pertencentes às famílias melhores situadas economicamente. Não só era mais baixa a natalidade nas mulheres que se valiam de anticoncepcionais, mas esta prática acompanhava-se de sensível redução no número de abortos e da mortalidade infantil. O efeito foi mais pronunciado entre aquelas que empregavam os anovulatórios.