90 research outputs found

    Cathodic disbonding tests operating at large cathodic potentials for long periods need current monitoring, pH control and anode isolation

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    Metallic structures in service in seawater are protected coupling cathodic protection and paints, where the former may induce disbondment of the latter. A preliminary evaluation of the cathodic disbondment risk can be made by cathodic disbondment tests, CDTs. Many CDTs use cathodic potentials as large as E < -1400 mV vs SCE applied up to 90 days. Only two CDT protocols require contemporary anode isolation, current and pH monitoring, without its correction. These three aspects were considered to develop a hybrid CDT; it consisted in polarizing steel panels at -1500 mV vs SCE for 12 weeks. The chemical effects related to the anodic processes were investigated. The observed pH acidic shift was justified by the increasing current demand due to paint damage and brucite precipitation on the panels. The necessity of anode isolating glass to prevent chlorine related chemical attack over the paints, potentially affecting the disbondment result, was verified. In conclusion, current monitoring, pH control and anode isolation are highly suggested to correctly interpret the cathodic disbondment results when CDTs requiring large electronegative potentials are applied for long periods

    Calpain digestion and HSP90-based chaperone protection modulate the level of plasma membrane F508del-CFTR

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    AbstractWe are here showing that peripheral mononuclear blood cells (PBMC) from cystic fibrosis (CF) patients contain almost undetectable amounts of mature 170 kDa CF-transmembrane conductance regulator (CFTR) and a highly represented 100 kDa form. This CFTR protein, resembling the form produced by calpain digestion and present, although in lower amounts, also in normal PBMC, is localized in cytoplasmic internal vesicles. These observations are thus revealing that the calpain-mediated proteolysis is largely increased in cells from CF patients. To characterize the process leading to the accumulation of such split CFTR, FRT cells expressing the F508del-CFTR mutated channel protein and human leukaemic T cell line (JA3), expressing wild type CFTR were used. In in vitro experiments, the sensitivity of the mutated channel to the protease is identical to that of the wild type, whereas in Ca2+-loaded cells F508del-CFTR is more susceptible to digestion. Inhibition of intracellular calpain activity prevents CFTR degradation and leads to a 10-fold increase in the level of F508del-CFTR at the plasma membrane, further indicating the involvement of calpain activity in the maintenance of very low levels of mature channel form. The higher sensitivity to calpain of the mutated 170 kDa CFTR results from a reduced affinity for HSP90 causing a lower degree of protection from calpain digestion. The recovery of HSP90 binding capacity in F508del-CFTR, following digestion, explains the large accumulation of the 100 kDa CFTR form in circulating PBMC from CF patients

    Calpains are Involved in Entamoeba histolytica-Induced Death of HT-29 Colonic Epithelial Cells

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    Entamoeba histolytica is an enteric tissue-invading protozoan parasite that can cause amebic colitis and liver abscess in humans. E. histolytica has the capability to kill colon epithelial cells in vitro; however, information regarding the role of calpain in colon cell death induced by ameba is limited. In this study, we investigated whether calpains are involved in the E. histolytica-induced cell death of HT-29 colonic epithelial cells. When HT-29 cells were co-incubated with E. histolytica, the propidium iodide stained dead cells markedly increased compared to that in HT-29 cells incubated with medium alone. This pro-death effect induced by ameba was effectively blocked by pretreatment of HT-29 cells with the calpain inhibitor, calpeptin. Moreover, knockdown of m- and µ-calpain by siRNA significantly reduced E. histolytica-induced HT-29 cell death. These results suggest that m- and µ-calpain may be involved in colon epithelial cell death induced by E. histolytica

    Calpain system protein expression in carcinomas of the pancreas, bile duct and ampulla

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    Background: Pancreatic cancer, including cancer of the ampulla of Vater and bile duct, is very aggressive and has a poor five year survival rate; improved methods of patient stratification are required. Methods: We assessed the expression of calpain-1, calpain-2 and calpastatin in two patient cohorts using immunohistochemistry on tissue microarrays. The first cohort was composed of 68 pancreatic adenocarcinomas and the second cohort was composed of 120 cancers of the bile duct and ampulla. Results: In bile duct and ampullary carcinomas an association was observed between cytoplasmic calpastatin expression and patient age (P = 0.036), and between nuclear calpastatin expression and increased tumour stage (P = 0.026) and the presence of vascular invasion (P = 0.043). In pancreatic cancer, high calpain-2 expression was significantly associated with improved overall survival (P = 0.036), which remained significant in multivariate Cox-regression analysis (hazard ratio = 0.342; 95% confidence interva l = 0.157-0.741; P = 0.007). In cancers of the bile duct and ampulla, low cytoplasmic expression of calpastatin was significantly associated with poor overall survival (P = 0.012), which remained significant in multivariate Cox-regression analysis (hazard ratio = 0.595; 95% confidence interval = 0.365-0.968; P = 0.037). Conclusion: The results suggest that calpain-2 and calpastatin expression is important in pancreatic cancers, influencing disease progression. The findings of this study warrant a larger follow-up study. Keywords: Calpain, Calpastatin, Pancreas, Ampulla, Bile duct, Cance

    Elevated calpain activity in acute myelogenous leukemia correlates with decreased calpastatin expression

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    Calpains are intracellular cysteine proteases that have crucial roles in many physiological and pathological processes. Elevated calpain activity has been associated with many pathological states. Calpain inhibition can be protective or lethal depending on the context. Previous work has shown that c-myc transformation regulates calpain activity by suppressing calpastatin, the endogenous negative regulator of calpain. Here, we have investigated calpain activity in primary acute myelogenous leukemia (AML) blast cells. Calpain activity was heterogeneous and greatly elevated over a wide range in AML blast cells, with no correlation to FAB classification. Activity was particularly elevated in the CD34+CD38− enriched fraction compared with the CD34+CD38+ fraction. Treatment of the cells with the specific calpain inhibitor, PD150606, induced significant apoptosis in AML blast cells but not in normal equivalent cells. Sensitivity to calpain inhibition correlated with calpain activity and preferentially targeted CD34+CD38− cells. There was no correlation between calpain activity and p-ERK levels, suggesting the ras pathway may not be a major contributor to calpain activity in AML. A significant negative correlation existed between calpain activity and calpastatin, suggesting calpastatin is the major regulator of activity in these cells. Analysis of previously published microarray data from a variety of AML patients demonstrated a significant negative correlation between calpastatin and c-myc expression. Patients who achieved a complete remission had significantly lower calpain activity than those who had no response to treatment. Taken together, these results demonstrate elevated calpain activity in AML, anti-leukemic activity of calpain inhibition and prognostic potential of calpain activity measurement

    Le basi della biochimica

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    L\u2019autore Denise R. Ferrier insegna presso il dipartimento di Biochimica e Biologia molecolare del Drexel University College of Medicine, Philadelphia. L\u2019opera Le basi della biochimica presenta un profilo compatto della materia in grado di agevolare lo studente nell\u2019apprendimento e nel superamento dell\u2019esame. Tutti gli argomenti essenziali della biochimica sono trattati con linguaggio semplice, puntando ad approfondire il metabolismo e le sue principali ricadute cliniche. Questo manuale si caratterizza per un\u2019intelligente integrazione tra le illustrazioni e il testo, oltre che per la presenza di circa 500 schemi molto curati e di numerose mappe concettuali, che consentono di acquisire in modo non dispersivo una piena padronanza dei nessi tra gli argomenti presentati. Contiene casi di studio illustrati, un indice delle patologie, dettagliati sommari di fine capitolo e oltre 200 domande con risposta. Un\u2019appendice con i casi clinici \ue8 disponibile in formato pdf nel sito collegato al libro. Le risorse multimediali All\u2019indirizzo online.universita.zanichelli.it/ferrier sono disponibili: i test interattivi, i casi clinici, le tecniche biochimiche, le animazioni 3D, la tavola periodica interattiva. Per accedere alle risorse protette \ue8 necessario registrarsi su my.zanichelli.it. inserendo la chiave di attivazione personale contenuta nel libro

    Fondamenti di Biochimica

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    I principi di biochimica di Lehninger

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    Gli autori David L. Nelson e Michael M. Cox sono professori di Biochimica alla University of Wisconsin-Madison. Il libro Il Lehninger \ue8 da oltre trent\u2019anni il manuale di biochimica per antonomasia e su di esso si sono formate generazioni di studenti in tutto il mondo. Nella sesta edizione \ue8 stata profondamente aggiornata la trattazione delle tecniche genomiche e delle loro applicazioni, che hanno trasformato la nostra comprensione della biochimica. Il Capitolo 9, Tecnologie basate sull\u2019informazione contenuta nel DNA, \ue8 stato completamente riscritto e ora incorpora i pi\uf9 recenti metodi genomici, tra i quali: il sequenziamento del DNA di nuova generazione, compresi i metodi Illumina e 454; le applicazioni della genomica, compresi l\u2019utilizzo degli aplotipi per tracciare le migrazioni degli esseri umani e la filogenetica per localizzare i geni umani associati alle patologie a carattere ereditario; la tipizzazione genica forense e l\u2019utilizzo della genomica personalizzata in medicina. Tra i molti nuovi argomenti della sesta edizione vi sono inoltre: l\u2019evoluzione prebiotica, i camini vulcanici e il mondo a RNA; le proteine intrinsecamente disordinate; gli analoghi dello stato di transizione e l\u2019inibizione irreversibile; le vie della coagulazione sanguigna nel contesto della regolazione enzimatica; la distribuzione asimmetrica dei lipidi all\u2019interno del doppio strato lipidico; il ruolo della superfamiglia delle proteine BAR nella curvatura della membrana; le proteine di supporto (scaffold) e i loro ruoli regolatori; le specie reattive dell\u2019ossigeno come prodotti biologici e come molecole di segnalazione; la struttura e la funzione dell\u2019aggregato metallico di produzione dell\u2019ossigeno del PSII; la formazione e il trasporto delle lipoproteine nei mammiferi la creatina fosfato e il ruolo della creatina chinasi nel trasferimento dell\u2019ATP al citosol; i simbionti microbici presenti nell\u2019intestino e la loro influenza sul metabolismo energetico e sull\u2019adipogenesi; i nucleosomi, le loro modificazioni e il loro posizionamento e la struttura altamente ordinata della cromatina; la DNA polimerasi e la ricombinazione omologa; il caricamento della RNA polimerasi II; la natura resistente alla mutazione del codice genetico; la regolazione dell\u2019espressione genica eucariotica da parte dei miRNA; la formazione delle anse del DNA, il controllo combinatorio, il rimodellamento della cromatina e la regolazione positiva negli eucarioti; la regolazione dell\u2019inizio della trascrizione negli eucarioti; i recettori nucleari degli steroidi. Sono state inserite nuove schede su metodiche sperimentali e applicazioni mediche e aggiunti nuovi esercizi di calcolo guidati. Sono presenti inoltre esercizi di interpretazione dei dati tratti dalla letteratura scientifica e oltre 600 problemi di fine capitolo. Le risorse multimediali All\u2019indirizzo online.universita.zanichelli.it/nelson-6e sono disponibili: i test interattivi, le tecniche animate, i videoesercizi, le animazioni 3D, i grafici attivi, i tutorial molecolari, la tavola periodica interattiva, la sitografia, il glossario e le soluzioni dei problemi. Alcune di queste risorse sono espressamente richiamate nel testo. Chi acquista il libro pu\uf2 scaricare l\u2019ebook multimediale, seguendo le istruzioni presenti nel sito. Per accedere alle risorse protette \ue8 necessario registrarsi su myzanichelli.it inserendo la chiave di attivazione personale contenuta nel libro

    Principi di biochimica

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    Durante lo studio del metabolismo biomolecolare si pu\uf2 facilmente perdere di vista il significato generale di quanto si legge, ovvero come le diverse vie metaboliche si intreccino e si integrino per contribuire a creare un organismo funzionale. In tutto il libro, e in particolare nelle sezioni Il metabolismo nel contesto, si insiste sulle relazioni tra i prodotti metabolici, utilizzando un esempio ricorrente relativo all\u2019uso delle risorse bioenergetiche, mentre gli approfondimenti clinici e biologici rendono espliciti i diversi modi in cui la biochimica influenza, a volte in modo sorprendente, molti aspetti del mondo in cui viviamo. L\u2019apprendimento \ue8 inoltre reso pi\uf9 efficace e solido dai Quesiti (le cui risposte sono riportate a fine capitolo), dalle Strutture a margine che forniscono un breve promemoria sulla struttura di una molecola o di un gruppo funzionale incontrato in precedenza, dalle brevi digressioni costituite dalle Note a margine e dai numerosi Problemi proposti per ogni capitolo

    Thermodynamic stability of RNi2 Laves phases

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    A calorimetric study of the RNi2 Laves phases (R = Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) has been carried out to determine the heat of formation (DfH) at 300 K using a high temperature direct drop calorimeter. The reliability of the calorimetric results has been determined and supported by using different analytical techniques: light optical microscopy, scanning electron microscopy equipped with electron probe microanalysis (EPMA) with energy dispersive X-ray spectroscopy (EDS) detector and X-ray powder diffraction analysis. We observed a gradual regular decreasing trend of the heat of formation with the increasing of the rare-earth atomic number from 34 \ub1 1.5 kJ/mol for PrNi2 to 50 \ub1 1 kJ/mol for ErNi2. Results have been discussed and compared with the data previously reported in the literature
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