Adenylate cyclase activity in cyanobacteria: activation by Ca(2+)-calmodulin and a calmodulin-like activity

An adenylate cyclase activity was partially characterized in the cyanobacterium Anabaena sp. The enzyme activity is found in soluble cell fractions and shows an apparent molecular weight of about 183,400. This adenylate cyclase is activated by Ca2+ and bovine brain or spinach calmodulin and it is inhibited by EGTA and some phenothiazine derivatives. Furthermore, Anabaena sp. extracts contain a calmodulin-like activity which stimulates bovine brain cyclic AMP phosphodiesterase and the Anabaena adenylate cyclase. EGTA and phenothiazine derivatives block the cyanobacterial modulator effect.     

Dose-dependent inhibitory and non-inhibitory action of somatostatin on insulin release in rats

The dose-dependent effect of intravenously infused synthetic somatostatin-14 on basal and postprandial insulin and gastrin release was assessed in anesthetized rats.Infusion of 1 ng · kg^?1 · min^?1 elicited a significant reduction of basal and postprandial insulin levels compared to the saline control group. At 15 ng · kg^?1 · min^?1 basal insulin was not affected but postprandial insulin levels were still significantly reduced. At 30 ng · kg^?1 · min^?1 neither basal nor stimulated insulin levels were affected. At the highest concentration of 120 ng · kg^?1 · min^?1 basal and postprandial insulin levels were suppressed similar to the lowest infusion rate of 1 ng · kg^?1 · min^?1. Basal gastrin levels were significantly reduced only at the highest rate of 120 ng · kg^?1 · min^?1. A significant reduction of postprandial gastrin levels was observed at 15 ng · kg^?1 · min^?1 and all higher infusion rates employed. Measurements of plasma somatostatin-like immunoreactivity (SLI) demonstrated that plasma SLI levels during the lowest infusion rate of 1 ng · kg^?1 · min^?1 were not different from the controls. No significant rise of plasma SLI levels was observed in response to the test meal. The higher infusion rates elicited a dose-dependent increase in plasma SLI levels. These data demonstrate that in rats somatostatin exerts a biological effect on insulin release at very low doses while certain greater infusion rates have no suppressive effect. Gastrin secretion is inhibited in a more linear pattern.     

Protein-mediated hydroxyl radical generation--the primary event in NADH oxidation and oxygen reduction by the granule rich fraction of human resting leukocytes.

The granule rich-fraction isolated from human resting polymorphonuclear leukocytes is capable of CN-insensitive NADH oxidation and O₂-uptake, accompanied by production of superoxide anion, hydroxyl radicals and H₂O₂. We showed that H₂O₂ initiates and maintains NADH oxidation and O₂-uptake but is also necessary for the formation of superoxide anion and hydroxyl radicals. It acts as a primary substrate for CN-insensitive protein-mediated formation of hydroxyl radicals, which in turn produce superoxide anions, probably through univalent oxidation of NADH as an intermediary.     

The helminth fauna of CHIle: IV. Nematodes of the genera Anisakis Dujardin, 1845 AND Phocanema Myers, 1954 in relation with gastric ulcers in a South American Sea Lion, Otaria byronia

A gastric ulcer was diagnosed in a South American Sea Lion, Otario byronia, captured along the northern coast of Chile. Species of Anisakis and Phocanema were found to be associated with the lesions. A discussion of the histopathologic damage observed is presented, along with probable etiology of the ulcer.     

Regulation of uracil uptake in Escherichia coli by adenosine 3',5'-monophosphate.

Culture of a wild-type strain of Escherichia coli in the presence of cyclic AMP leads to an impairment of uracil uptake. Half maximum inhibition of uracil uptake was observed at 1.5 mM cyclic AMP. The effect seems to be specific since no inhibition was found in cultures supplemented with ATP, ADP or 5'-AMP. Similarly the inhibition was not observed in cultures of a mutant deficient in the cyclic AMP receptor protein. The inhibition in uracil uptake, found in bacteria cultured in the presence of cyclic AMP, is not a consequence of a reduction in the growth rate. On the other hand, this inhibition was observed only in cultures containing glucose or pyruvate as carbon source.     

Time-dependent regulation of muscle caveolin activation and insulin signalling in response to high-fat diet

We studied the effect of high-fat diet on the expression and activation of the three caveolins in rat skeletal muscle and their association with the insulin signalling cascade. Initial response was characterized by increased signalling through Cav-1 and Cav-3 phosphorylation, suggesting that both participate in an initial acute response to the calorie surplus. Afterwards, Cav-1 signalling was slightly reduced, whereas Cav-3 remained active. Late chronic phase signalling through both proteins was impaired inducing a prediabetic state. Summarizing, caveolins seem to mediate a time-dependent regulation of insulin cascade in response to high-fat diet in muscle.     

PARP-1 Regulates Metastatic Melanoma through Modulation of Vimentin-induced Malignant Transformation

PARP inhibition can induce anti-neoplastic effects when used as monotherapy or in combination with chemo- or radiotherapy in various tumor settings; however, the basis for the anti-metastasic activities resulting from PARP inhibition remains unknown. PARP inhibitors may also act as modulators of tumor angiogenesis. Proteomic analysis of endothelial cells revealed that vimentin, an intermediary filament involved in angiogenesis and a specific hallmark of EndoMT (endothelial to mesenchymal transition) transformation, was down-regulated following loss of PARP-1 function in endothelial cells. VE-cadherin, an endothelial marker of vascular normalization, was up-regulated in HUVEC treated with PARP inhibitors or following PARP-1 silencing; vimentin over-expression was sufficient to drive to an EndoMT phenotype. In melanoma cells, PARP inhibition reduced pro-metastatic markers, including vasculogenic mimicry. We also demonstrated that vimentin expression was sufficient to induce increased mesenchymal/pro-metastasic phenotypic changes in melanoma cells, including ILK/GSK3-β-dependent E-cadherin down-regulation, Snail1 activation and increased cell motility and migration. In a murine model of metastatic melanoma, PARP inhibition counteracted the ability of melanoma cells to metastasize to the lung. These results suggest that inhibition of PARP interferes with key metastasis-promoting processes, leading to suppression of invasion and colonization of distal organs by aggressive metastatic cells.     

Melatonin in the seasonal response of the aphid Acyrthosiphon pisum

Aphids display life cycles largely determined by the photoperiod.During the warm long-day seasons.most aphid species reproduce by viviparous parthenogenesis.The shortening of the photoperiod in autumn induces a switch to sexual reproduction.Males and sexual females mate to produce overwintering resistant eggs.In addition to this full life cycle(holocycle),there are anholocyelic lineages that do not respond to changes in photoperiod and reproduce continuously by parthenogenesis.The molecular or hormonal events that trigger the scasonal response(i.c,induction of the sexual phenotypes)are still unknown.Although circadian synthesis of melatonin is known to play a key role in vertebrate photoperiodism,the involvement of the circadian clock and/or of the hor-mone melatonin in insect seasonal responses is not so well established.Here we show that melatonin levels in the aphid Acyrthosiphon pisum are significantly higher in holocyclice aphids reared under short days than under long days,while no differences were found between anholoeyelic aphids under the same conditions.We also found that melatonin is localized in the aphid suboesophageal ganglion(SOG)and in the thoracic ganglionic mass(TGM).In analogy to vertcbrates,insect-type arylalkxylamine N-acetyltransferases(i-AANATs)are thought to play a key role in melatonin synthesis.We measured the expression of four I-AANAT genes identified in A.pisum and localized two of them in situ in the insect central nervous systems(CNS).Levels of expression of these genes were compatible with the quantities of melatonin observed.Moreover,like melatonin,expression of these genes was found in the SOG and the TGM.