Gallbladder Cancer: Surgical Management

Gallbladder cancer represents one of the rare and highly fatal neoplastic diseases, early diagnosis and treatment being the key for an acceptable outcome. The best survival results are obtained for patients with T1-T2 stage, a radical cholecystectomy being sufficient in most of these cases. For advanced tumors, major liver resections could be necessary to obtain optimal oncological results. Although a high percentage of the patients are diagnosed with unresectable disease, the continuous progresses made in the field of surgical therapy and oncological treatment could finally improve the outcome of this neoplastic pathology

Surgical Treatment of Distal Common Bile Duct Malignancy

Distal cholangiocarcinoma is a rare malignant condition arising from the epithelial cells of the biliary tract. Surgical resection is the only curable alternative for patients with this disease. True resectability is often determined by surgical exploration. Duodenopancreatectomy is an extremely high-demanding technique and is the only one that can be potentially curable for patients diagnosed with resectable distal cholangiocarcinoma. Long-term survival may be achieved only in selected patients, undergoing duodenopancreatectomy, especially in patients where R0 margins are achieved. Perineural extension, pancreatic invasion, and lymph nodes involvement are the main risk factors for recurrence. Palliative biliodigestive diversion or endoscopic internal drainage of the biliary tree is alternative for patients with unresectable tumors. Although the prognosis after surgical treatment of distal common bile duct malignancy is better than for other periampullary tumors, the continuous progresses made in the field of surgical therapy and oncological treatment may lead to an improvement in the outcome of this neoplastic pathology

The Arabidopsis thylakoid chloride channel ClCe regulates ATP availability for light-harvesting complex II protein phosphorylation

Coping with changes in light intensity is challenging for plants, but well-designed mechanisms allow them to acclimate to most unpredicted situations. The thylakoid K+/H+ antiporter KEA3 and the voltage-dependent Cl- channel VCCN1 play important roles in light acclimation by fine-tuning electron transport and photoprotection. Good evidence exists that the thylakoid Cl- channel ClCe is involved in the regulation of photosynthesis and state transitions in conditions of low light. However, a detailed mechanistic understanding of this effect is lacking. Here we report that the ClCe loss-of-function in Arabidopsis thaliana results in lower levels of phosphorylated light-harvesting complex II (LHCII) proteins as well as lower levels of the photosystem I-LHCII complexes relative to wild type (WT) in low light conditions. The phosphorylation of the photosystem II core D1/D2 proteins was less affected either in low or high light conditions. In low light conditions, the steady-state levels of ATP synthase conductivity and of the total proton flux available for ATP synthesis were lower in ClCe loss-of-function mutants, but comparable to WT at standard and high light intensity. As a long-term acclimation strategy, expression of the ClCe gene was upregulated in WT plants grown in light-limiting conditions, but not in WT plants grown in standard light even when exposed for up to 8 h to low light. Taken together, these results suggest a role of ClCe in the regulation of the ATP synthase activity which under low light conditions impacts LHCII protein phosphorylation and state transitions.</p

Ion Transport in Chloroplasts with Role in Regulation of Photosynthesis

Photosynthesis is the primary energy source of almost all ecosystems on Earth. Oxygenic photosynthesis has appeared approximately 2.4 billion years ago and has since then gradually evolved into the complex process that land plants, algae and cyanobacteria perform today. During the course of evolution, these organisms have also developed mechanisms to improve photosynthetic efficiency, to cope with changes in the environment, and effectively use the available resources. The environment in which photosynthetic organisms grow contains numerous ionic compounds. These compounds are taken up and used in numerous important processes, including photosynthesis in chloroplasts. As in the rest of the cell, specialized proteins named channels and transporters mediate ion transport across membranes and control ion homeostasis in chloroplasts. The work presented in this thesis addresses the role in regulation of photosynthesis of ion channels and transporters from the chloroplast inner envelope (Paper I), and the thylakoid membrane (Paper I to V) of Arabidopsis thaliana. Potassium ion fluxes mediated by the chloroplast K+/H+ antiporters KEA1, KEA2 and KEA3 regulate the composition of the proton motive force (PMF) across the thylakoid membrane that activates photoprotective mechanisms (NPQ) (Paper I). In Paper II, an Arabidopsis mutant named pam71 is found disturbed in photosystem II efficiency and the adjustment of PMF, due to altered Ca2+ homeostasis in the chloroplast. In Paper III, it is shown that the thylakoid phosphate transporter PHT4;1 affects the availability of phosphate for ATP synthesis, and also alters NPQ activation kinetics and PMF composition. A novel thylakoid voltage-dependent chloride channel (VCCN1) is identified in Paper IV, and shown to affect PMF and NPQ activation upon illumination and after rapid shifts from low light to high light. In Paper V it is shown that the thylakoid chloride channel CLCe contributes to the modulation of PMF as well as to the regulation of electron transfer and state transition. Taken together, the findings of this thesis bring novel mechanisms of anion and cation transport across the thylakoid membrane and the chloroplast inner envelope with role in regulation of photosynthesis

An update on the regulation of photosynthesis by thylakoid ion channels and transporters in Arabidopsis.

International audienceIn natural variable environments, plants rapidly adjust photosynthesis for optimal balance between light absorption and utilization. There is increasing evidence suggesting that ion fluxes across the chloroplast thylakoid membrane play an important role in this regulation, by affecting the proton motive force, and consequently photosynthesis and thylakoid membrane ultrastructure. This minireview presents an update on the thylakoid ion channels and transporters characterized in Arabidopsis thaliana as being involved in these processes, as well as an outlook at the evolutionary conservation of their functions in other photosynthetic organisms. This is a contribution to shed light on the thylakoid network of ion fluxes and how they help plants to adjust photosynthesis in variable light environments

The Arabidopsis thylakoid chloride channel AtCLCe functions in chloride homeostasis and photosynthetic regulation

Chloride ions can be translocated across cell membranes through Cl− channels or Cl−/H+ exchangers. The thylakoid-located member of the Cl− channel CLC family in Arabidopsis thaliana (AtCLCe) was hypothesized to play a role in photosynthetic regulation based on the initial photosynthetic characterization of clce mutant lines. The reduced nitrate content of Arabidopsis clce mutants suggested a role in regulation of plant nitrate homeostasis. In this study, we aimed to further investigate the role of AtCLCe in the regulation of ion homeostasis and photosynthetic processes in the thylakoid membrane. We report that the size and composition of proton motive force were mildly altered in two independent Arabidopsis clce mutant lines. Most pronounced effects in the clce mutants were observed on the photosynthetic electron transport of dark-adapted plants, based on the altered shape and associated parameters of the polyphasic OJIP kinetics of chlorophyll a fluorescence induction. Other alterations were found in the kinetics of state transition and in the macro-organisation of photosystem II supercomplexes, as indicated by circular dichroism measurements. Pre-treatment with KCl but not with KNO3 restored the wild-type photosynthetic phenotype. Analyses by transmission electron microscopy revealed a bow-like arrangement of the thylakoid network and a large thylakoid-free stromal region in chloroplast sections from the dark-adapted clce plants. Based on these data, we propose that AtCLCe functions in Cl− homeostasis after transition from light to dark, which affects chloroplast ultrastructure and regulation of photosynthetic electron transport