Enstrophy from symmetry

We study symmetry principles associated with the approximately conserved enstrophy current, responsible for the inverse energy cascade in non relativistic 2+1 dimensional turbulence. We do so by identifying the accidental symmetry associated with enstrophy current conservation in a recently realized effective action principle for hydrodynamics. Our analysis deals with both relativistic and non relativistic effective actions and their associated symmetries

Dermoscopic and Clinical Response Predictor Factors in Nonsegmental Vitiligo Treated with Narrowband Ultraviolet B Phototherapy: A Prospective Observational Study

Introduction: Few data on possible local factors that can influence the achievement of response in nonsegmental vitiligo (NSV) treated with narrowband ultraviolet B (Nb-UVB) phototherapy are available. Our objective is to evaluate possible correlations between therapeutic outcomes and dermoscopic and local (lesional) clinical findings of vitiligous lesions undergoing Nb-UVB phototherapy to find positive and/or negative response predictor factors to such treatment. Methods: For each target patch, we calculated the extension area using a computer-aided method and assessed dermoscopic and local (lesional) clinical findings at baseline. After 30 phototherapy sessions (twice weekly), surface area of the lesions was reevaluated to assess clinical improvement, correlating the therapeutic outcome with initial clinical and dermoscopic features. Results: A total of 70 lesions were finally included in the study. At the end of therapy, 18 patches (25.7%) achieved improvement, and the presence of perifollicular pigmentation on baseline dermoscopic examination was found to be associated with a 12-fold higher probability of having a positive therapeutic outcome. Similarly, face localization was also correlated with clinical amelioration, with a sevenfold higher probability for improvement. No association (p > 0.05) between therapeutic outcomes (either good or poor) and other dermoscopic or local clinical variables (including leukotrichia) was observed. Conclusions: Therapeutic response of vitiligo to Nb-UVB phototherapy may be positively affected by local features of the lesions, i.e., face localization and presence of perifollicular pigmentation on baseline dermoscopic examination, which might be considered as positive response predictor factors to optimize treatment of vitiligo

Utility of ElastPQ point-shear wave elastography in the work-up of patients with primary sclerosing cholangitis

Background & Aims: Liver stiffness measurement (LSM) and spleen stiffness measurement (SSM) have been shown to be useful tools for assessing the risk of fibrosis and portal hypertension, respectively. However, data on the accuracy of LSM and SSM measured by point-shear wave elastography (pSWE) in patients affected by primary sclerosing cholangitis (PSC) are still lacking. Thus, we aimed to prospectively assess their performance in a cohort of patients with PSC. Methods: We determined the correlation between LSM assessed by a pSWE technique (ElastPQ) and by FibroScan-transient elastography (F-TE). Furthermore, we used receiver-operating characteristic curves and area under the curves (AUROC) to evaluate the performance of LSM by ElastPQ for the staging of fibrosis, using F-TE as a reference standard, and the performance of LSM and SSM by ElastPQ in predicting the presence of oesophageal varices (OVs). Results: One hundred and fifty-two patients with PSC (93 males [61.2%], mean age 46 ± 16 years) were prospectively recruited. ElastPQ and F-TE LSMs were available for all patients, while ElastPQ SSM was available in 109 (72%) patients of whom 35 underwent upper gastrointestinal endoscopy within 1 year of the ultrasound assessment. ElastPQ LSM showed an excellent correlation with F-TE (p <0.001, Spearman's 0.93; Lin's 0.86) and a good diagnostic accuracy for fibrosis staging along all stages of liver fibrosis (AUROCs 0.96, 0.97, 0.97 and 0.99 for fibrosis stages F≥1, F≥2, F≥3 and F=4, respectively), using F-TE as a surrogate of histological fibrosis. ElastPQ SSM showed a good diagnostic performance in predicting the presence of OVs at endoscopy. Conclusions: LSM and SSM by ElastPQ can be used as accurate tools for liver fibrosis risk assessment and fibrosis staging, as well as for predicting the presence of OVs in the work-up of patients with PSC. Impact and implications: Liver and spleen stiffness measurement (LSM and SSM, respectively) by ElastPQ point-shear wave elastography in patients with primary sclerosing cholangitis represent reliable and reproducible tools for non-invasively staging the severity of liver disease and stratifying patients according to their risk of developing liver-related outcomes. In particular, LSM shows good accuracy for staging liver fibrosis and therefore detecting those patients at high risk of having compensated advanced chronic liver disease who require close monitoring. SSM seems to be promising to detect the risk of portal hypertension and therefore of oesophageal varices, enabling the triaging of patients who really need to undergo a screening endoscopy

Exact Solution of the Discrete (1+1)-dimensional RSOS Model with Field and Surface Interactions

We present the solution of a linear Restricted Solid--on--Solid (RSOS) model in a field. Aside from the origins of this model in the context of describing the phase boundary in a magnet, interest also comes from more recent work on the steady state of non-equilibrium models of molecular motors. While similar to a previously solved (non-restricted) SOS model in its physical behaviour, mathematically the solution is more complex. Involving basic hypergeometric functions ${}_3\phi_2$, it introduces a new form of solution to the lexicon of directed lattice path generating functions.Comment: 10 pages, 2 figure

Evaluation of intracellular signalling pathways in response to insulin-like growth factor I in apoptotic-resistant activated human hepatic stellate cells

BACKGROUND: Human hepatic stellate cells have been shown to be resistant to apoptotic stimuli. This is likely dependent on the activation of anti-apoptotic pathways upon transition of these cells to myofibroblast-like cells. In particular, previous studies have demonstrated an increased expression of the anti-apoptotic protein Bcl-2 and a decreased expression of the pro-apoptotic protein Bax during the transition of the hepatic stellate cell phenotype from quiescent to myofibroblast-like cells. However, the role and expression of other key anti-apoptotic and survival pathways elicited by polypeptide growth factors involved in the chronic wound healing process remain to be elucidated. In particular, insulin growth factor-I promotes chemotactic and mitogenic effects in activated human hepatic stellate cells and these effects are mediated by the activation of PI 3-K. The role of insulin growth factor-I as a survival factor in human hepatic stellate cells needs to be substantiated. The aim of this study was to evaluate the involvement of other key anti-apoptotic pathways such as PI-3K/Akt/p-Bad in response to insulin growth factor-I. RESULTS: Insulin growth factor-I induced activation of Akt followed by Bad phosphorylation after 15 minutes of incubation. These effects were PI-3k dependent since selective inhibitors of this molecule, wortmannin and LY294002, inhibited both Akt and Bad phosphorylation. The effect of insulin growth factor-I on the activation of two downstream targets of Akt activation, that is, GSK3 and FHKR, both implicated in the promotion of cell survival was also investigated. Both targets became phosphorylated after 15 minutes of incubation, and these effects were also PI-3K-dependent. Despite the activation of this survival pathway insulin growth factor-I did not have a remarkable biological effect, probably because other insulin growth factor-I-independent survival pathways were already maximally activated in the process of hepatic stellate cell activation. However, after incubation of the cells with a strong apoptotic stimuli such as Fas ligand+cycloheximide, a small percentage of hepatic stellate cells underwent programmed cell death that was partially rescued by insulin growth factor-I. CONCLUSION: In addition to Bcl-2, several other anti-apoptotic pathways are responsible for human hepatic stellate cell resistance to apoptosis. These features are relevant for the progression and limited reversibility of liver fibrosis in humans

Elastic fibres in alcoholic liver disease

The literature on the contribution of elastic fibre deposition to alcohol-related liver disease (ARLD) is limited. We studied: (1) 180 liver biopsies from ARLD patients; (2) 20 ARLD explant livers; (3) 213 liver biopsies with non-ARLD injury. Elastic fibres were assessed in terms of their distribution around hepatocytes [pericellular elastosis (PCE)] and within bridging fibrous septa (septal elastosis) and scored using a semiquantitative system. We also investigated the composition of the elastic fibres (oxytalan, elaunin and mature elastic fibres) in 20 cases. PCE was associated with steatohepatitis in ARLD patients and with ARLD when compared to non-ARLD cases (p < 0.001). Oxytalan fibres were identified in PCE in ARLD biopsies and broken dense perisinusoidal mature elastic fibres in explanted livers. Septal elastosis increased from intermediate to advanced fibrosis stage. Early septal elastosis contained oxytalan fibres, whereas septal elastosis at more advanced stages contained mainly mature elastic fibres. PCE is a typical feature of steatohepatitis in ARLD and includes oxytalan fibres. Septal elastosis is a gradual process with a transition from oxytalan to mature elastic fibres usually present in explanted livers. There may be different dynamics in the assembly and reabsorption of pericellular and septal elastic fibres, and a potential role for stratification of patients with advanced stage ARLD

Transaminase abnormalities and adaptations of the liver lobule manifest at specific cut-offs of steatosis

There is little documented evidence suggesting that liver fat is responsible for liver injury in the absence of other disease processes. We investigated the relationships between liver fat, aminotransferases and hepatic architecture in liver biopsies with simple steatosis. We identified 136 biopsies with simple steatosis from the Royal Free Hospital Archives with both clinical data and sufficient material. Digital image analysis was employed to measure fat proportionate area (mFPA). Hepatocyte area (HA) and lobule radius (LR) were also measured. There were significant increases in ALT (p &lt; 0.001) and AST (p = 0.013) with increased fat content and evidence to suggest both 5% and 20% mFPA as a cut-off for raised ALT. In liver with increased fat content there were significant increases in HA (p &lt; 0.001). LR also increased as mFPA increased to 10% (p &lt; 0.001), at which point the lobule ceased to expand further and was counterbalanced with a decrease in the number of hepatocytes per lobule (p = 0.029). Consequently there are mechanisms of adaption in the liver architecture to accommodate the accumulation of fat and these are accompanied by significant increases in transaminases. These results support the generally accepted cut-off of 5% fat for steatosis and indicate 20% as a threshold of more severe liver injury

A combined model based on spleen stiffness measurement and Baveno VI criteria to rule out high-risk varices in advanced chronic liver disease

BACKGROUND & AIMS: Recently, Baveno VI guidelines suggested that esophagogastroduodenoscopy (EGD) can be avoided in patients with compensated advanced chronic liver disease (cACLD) who have a liver stiffness measurement (LSM) 150,000/mm3. We aimed to: assess the performance of spleen stiffness measurement (SSM) in ruling out patients with high-risk varices (HRV); validate Baveno VI criteria in a large population and assess how the sequential use of Baveno VI criteria and SSM could safely avoid the need for endoscopy. METHODS: We retrospectively analyzed 498 patients with cACLD who had undergone LSM/SSM by transient elastography (TE) (FibroScan®), platelet count and EGDs from 2012 to 2016 referred to our tertiary centre. The new combined model was validated internally by a split-validation method, and externally in a prospective multicentre cohort of 115 patients. RESULTS: SSM, LSM, platelet count and Child-Pugh-B were independent predictors of HRV. Applying the newly identified SSM cut-off (≤46 kPa) or Baveno VI criteria, 35.8% and 21.7% of patients in the internal validation cohort could have avoided EGD, with only 2% of HRVs being missed with either model. The combination of SSM with Baveno VI criteria would have avoided an additional 22.5% of EGDs, reaching a final value of 43.8% spared EGDs, with <5% missed HRVs. Results were confirmed in the prospective external validation cohort, as the combined Baveno VI/SSM ≤46 model would have safely spared (0 HRV missed) 37.4% of EGDs, compared to 16.5% when using the Baveno VI criteria alone. CONCLUSIONS: A non-invasive prediction model combining SSM with Baveno VI criteria may be useful to rule out HRV and could make it possible to avoid a significantly larger number of unnecessary EGDs compared to Baveno VI criteria only. LAY SUMMARY: Spleen stiffness measurement assessed by transient elastography, the most widely used elastography technique, is a non-invasive technique that can help the physician to better stratify the degree of portal hypertension and the risk of esophageal varices in patients with compensated advanced chronic liver disease. Performing spleen stiffness measurement together with liver stiffness measurement during the same examination is simple and fast and this sequential model can identify a greater number of patients that can safely avoid endoscopy, which is an invasive and expensive examination