Helicobacter species in cancers of the gallbladder and extrahepatic biliary tract

Helicobacter species have been found in human bile and biliary tract (BT) tissue and are suspected to cause BT diseases, including gallbladder and extrahepatic cancers, collectively referred to in this work as BT cancers. We conducted a literature review of the epidemiological evidence linking the presence of Helicobacter species in bile or BT biopsies to BT cancers and benign diseases. Reports showed great variability with respect to study methods. Nine studies of BT cancers were identified, all with 30 or fewer BT cancers; eight included cancer-free control subjects and used polymerase chain reaction (PCR) as a means of Helicobacter species detection. In four of these studies, Helicobacter species were detected in patients with BT cancer significantly more frequently than in controls, at least when controls without BT diseases were used. In two studies, no Helicobacter species were detected in either cases or controls. Helicobacter species were also often detected in benign BT diseases such as gallstone disease or chronic cholecystitis. As our current knowledge relies on a few small studies that showed substantial differences, larger studies and more standardised protocols for detecting DNA and antibodies against Helicobacter species are needed to investigate a potential association with BT cancer

Calcium efflux in rat tail artery during potassium induced relaxation

The current study investigates the mechanism by which the concentration of activator Ca 2+ is decreased during potassium induced relaxation of vascular smooth muscle. Helically cut strips of rat tail artery were mounted between a fixed base and force transducers; isometric contractions were recorded. The arterial strips relaxed in response to potassium after contraction induced by norepinephrine in potassium-free solution. The efflux of 45Ca 2+ from the strips was stimulated by norepinephrine during the potassium-free cycle. This increase in efflux was prevented during potassium induced relaxation. D-600, an inhibitor of transmembrane Ca 2+ flux, reduced the magnitude of potassium induced relaxation by 35%. These observations suggest that relaxation in response to potassium is the result of a decrease in membrane permeability to Ca 2+ coupled with an increase in Ca 2+ sequestration at intracellular sites.link_to_subscribed_fulltex

Inactivation of released norepinephrine in rat tail artery by neuronal uptake

The relationship between adrenergic nerve activity and neuronal uptake was investigated. Helically cut strips of rat tail artery were mounted in organ chambers and isometric contractions were recorded. Spontaneous contractions were occasionally observed and these contractions were blocked by phentolamine. Cumulative addition of cocaine produced contractions of the strips. These contractions were blocked by phentolamine and reduced after denervation with 6-hydroxydopamine. Cocaine potentiated the contractile responses to exogenous norepinephrine and caused a shift to the left in the concentration-response curve. Contractions in response to low-frequency field stimulation were potentiated by cocaine; contractions produced by high frequencies were not altered by the drug. Cocaine had no effect on contractions produced by depolarization of the prejunctional membrane with high potassium. The relative rates of relaxation following high- and low-frequency stimulation were increased similarly by cocaine. The results indicate (1) the spontaneous activity of rat tail artery is related to the leakage of norepinephrine from nerve endings; (2) contraction in response to cocaine alone probably results from inhibition of neuronal uptake and the release of endogenous norepinephrine; and (3) the amine uptake mechanism is not operative during depolarization of prejunctional membrane.link_to_subscribed_fulltex

Effect of potassium on the mechanical activity of rat tail artery

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