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Background: Obesity can influence hepatic mitochondrial function, and cause non-alcoholic steatohepatitis (NASH). Diagnosis and follow-up rely on invasive liver biopsy so blood-based markers are urgently required., Aim: To investigate whether values of circulating metabolites from energy and one-carbon (1-C) metabolism may: (a) reflect hepatic mitochondrial flexibility failure and (b) act as NASH biomarkers., Methods: Patients with severe obesity undergoing bariatric surgery (n = 270) were investigated using quantitative targeted plasma metabolomics. Comparisons were with non-obese controls without liver disease (n = 50). Obese patients with NASH (n = 53) and without NASH (n = 130) representing extreme groups of liver disease were assessed to test the diagnostic ability of the measured circulating metabolites. Paired liver biopsy and plasma samples from NASH patients were available 1 year post-surgery and were evaluated to monitor metabolomic changes with liver damage resolution., Results: We identified correlations between human liver metabolism and obesity. High-plasma α-ketoglutarate (α-KG) and lactate concentrations in NASH patients indicating citric acid cycle replenishment via glutaminolysis might also be a crucial point in NASH onset. Plasma measurements of α-KG, β-hydroxybutyrate, pyruvate and oxaloacetate reduced the uncertainty in clinical diagnosis of NASH [area under receiver operating characteristic curve (AUC) of 0.826] and predicted NASH resolution without ambiguity (AUC of 0.999)., Conclusion: Changes in plasma mitochondrial metabolites appear to be associated with NASH. These metabolic responses may be dynamically remodelled following resolution of liver damage through massive weight loss., (© 2019 John Wiley & Sons Ltd.)

Comorbidities associated with obesity have become a worldwide public health concern. Obesity-associated hepatic steatosis is not benign, and the risk of developing severe liver disease is high. Currently, biopsy is the only clinical tool available for the diagnosis of pathological alterations in the liver. However, the procedure is painful and not without risk. As such, there is a need to identify non-invasive biomarkers of steatosis. There has been considerable progress in this area, but research appears to be limited to measurements of levels of certain parameters in patients with liver impairment relative to those of healthy controls. The clinically relevant aim should be to distinguish, at an early stage, those obese individuals with liver steatosis from those obese individuals without it. Plasma constituents that act as surrogates of altered hepatic energy metabolism in response to food intake are likely candidates. Targeted metabolomics, combined with quantitation of the metabolites involved, has been shown to be an efficient measurement tool. Indeed, the evaluation of exhaled volatile compounds might be sufficient, while other rapid, sensitive, and reproducible methods have been validated in preliminary studies in various clinical settings. Metabolomics methods are promising but require considerable expertise and sophisticated (and expensive) equipment not readily available in all centers. The challenge is to adapt this newly acquired, expanding knowledge to current, reasonably equipped clinical laboratories, while substantially reducing costs. Good outcomes are urgently required if effective prevention programs are to be developed to decrease the prevalence of liver disease.

Abnormalities in mitochondrial metabolism and regulation of energy balance contribute to human diseases. The consequences of high fat and other nutrient intake, and the resulting acquired mitochondrial dysfunction, are essential to fully understand common disorders, including obesity, cancer, and atherosclerosis. To simultaneously and noninvasively measure and quantify indirect markers of mitochondrial function, we have developed a method based on gas chromatography coupled to quadrupole-time of flight mass spectrometry and an electron ionization interface, and validated the system using plasma from patients with peripheral artery disease, human cancer cells, and mouse tissues. This approach was used to increase sensibility in the measurement of a wide dynamic range and chemical diversity of multiple intermediate metabolites used in energy metabolism. We demonstrate that our targeted metabolomics method allows for quick and accurate identification and quantification of molecules, including the measurement of small yet significant biological changes in experimental samples. The apparently low process variability required for its performance in plasma, cell lysates, and tissues allowed a rapid identification of correlations between interconnected pathways. Our results suggest that delineating the process of energy generation by targeted metabolomics can be a valid surrogate for predicting mitochondrial dysfunction in biological samples. Importantly, when used in plasma, targeted metabolomics should be viewed as a robust and noninvasive source of biomarkers in specific pathophysiological scenarios.

Lung cancer is the leading cause of cancer-related deaths globally, with non-small cell lung cancer (NSCLC) accounting for over 85% of cases and poor prognosis in advanced stages. This study explored shifts in circulating metabolite levels in NSCLC patients versus healthy controls and examined the effects of conventionally fractionated radiation therapy (CFRT) and stereotactic body radiation therapy (SBRT). We enrolled 91 NSCLC patients (38 CFRT and 53 SBRT) and 40 healthy controls. Plasma metabolite levels were assessed using semi-targeted metabolomics, revealing 32 elevated and 18 reduced metabolites in patients. Key discriminatory metabolites included ethylmalonic acid, maltose, 3-phosphoglyceric acid, taurine, glutamic acid, glycocolic acid, and d-arabinose, with a combined Receiver Operating Characteristics curve indicating perfect discrimination between patients and controls. CFRT and SBRT affected different metabolites, but both changes suggested a partial normalization of energy and amino acid metabolism pathways. In conclusion, metabolomics identified distinct metabolic signatures in NSCLC patients with potential as diagnostic biomarkers. The differing metabolic responses to CFRT and SBRT reflect their unique therapeutic impacts, underscoring the utility of this technique in enhancing NSCLC diagnosis and treatment monitoring. [ABSTRACT FROM AUTHOR]

Viral infections cause metabolic dysregulation in the infected organism. The present study used metabolomics techniques and machine learning algorithms to retrospectively analyze the alterations of a broad panel of metabolites in the serum and urine of a cohort of 126 patients hospitalized with COVID-19. Results were compared with those of 50 healthy subjects and 45 COVID-19-negative patients but with bacterial infectious diseases. Metabolites were analyzed by gas chromatography coupled to quadrupole time-of-flight mass spectrometry. The main metabolites altered in the sera of COVID-19 patients were those of pentose glucuronate interconversion, ascorbate and fructose metabolism, nucleotide sugars, and nucleotide and amino acid metabolism. Alterations in serum maltose, mannonic acid, xylitol, or glyceric acid metabolites segregated positive patients from the control group with high diagnostic accuracy, while succinic acid segregated positive patients from those with other disparate infectious diseases. Increased lauric acid concentrations were associated with the severity of infection and death. Urine analyses could not discriminate between groups. Targeted metabolomics and machine learning algorithms facilitated the exploration of the metabolic alterations underlying COVID-19 infection, and to identify the potential biomarkers for the diagnosis and prognosis of the disease. [ABSTRACT FROM AUTHOR]

Radiotherapy (RT) is part of the standard treatment of breast cancer (BC) because of its effects on relapse reduction and survival. However, response to treatment is highly variable, and some patients may develop disease progression (DP), a second primary cancer, or may succumb to the disease. Antioxidant systems and inflammatory processes are associated with the onset and development of BC and play a role in resistance to treatment. Here, we report our investigation into the clinical evolution of BC patients, and the impact of RT on the circulating levels of the antioxidant enzyme paraoxonase-1 (PON1), cytokines, and other standard biochemical and hematological variables. Gradient Boosting Machine (GBM) algorithm was used to identify predictive variables. This was a retrospective study in 237 patients with BC. Blood samples were obtained pre- and post-RT, with samples of healthy women used as control subjects. Results showed that 24 patients had DP eight years post-RT, and eight patients developed a second primary tumor. The algorithm identified interleukin-4 and total lymphocyte counts as the most relevant indices discriminating between BC patients and control subjects, while neutrophils, total leukocytes, eosinophils, very low-density lipoprotein cholesterol, and PON1 activity were potential predictors of fatal outcome. [ABSTRACT FROM AUTHOR]

Background: Isolated rapid eye movement sleep behavior disorder (IRBD) is a well‐established clinical risk factor for Lewy body diseases (LBDs), such as Parkinson's disease (PD) and dementia with Lewy bodies (DLB). Objective: To elucidate whether serum microRNA (miRNA) deregulation in IRBD can antedate the diagnosis of LBD by performing a longitudinal study in different progression stages of IRBD before and after LBD diagnosis and assessing the predictive performance of differentially expressed miRNAs by machine learning–based modeling. Methods: Using genome‐wide miRNA analysis and real‐time quantitative polymerase chain reaction validation, we assessed serum miRNA profiles from patients with IRBD stratified by dopamine transporter (DaT) single‐photon emission computed tomography into DaT‐negative IRBD (n = 17) and DaT‐positive IRBD (n = 21), IRBD phenoconverted into LBD (n = 13), and controls (n = 20). Longitudinally, we followed up the IRBD cohort by studying three time point serum samples over 26 months. Results: We found sustained cross‐sectional and longitudinal deregulation of 12 miRNAs across the RBD continuum, including DaT‐negative IRBD, DaT‐positive IRBD, and LBD phenoconverted IRBD (let‐7c‐5p, miR‐19b‐3p, miR‐140, miR‐22‐3p, miR‐221‐3p, miR‐24‐3p, miR‐25‐3p, miR‐29c‐3p, miR‐361‐5p, miR‐425‐5p, miR‐4505, and miR‐451a) (false discovery rate P < 0.05). Age‐ and sex‐adjusted predictive modeling based on the 12 differentially expressed miRNA biosignatures discriminated IRBD and PD or DLB from controls with an area under the curve of 98% (95% confidence interval: 89–99%). Conclusions: Besides clinical diagnosis of IRBD or imaging markers such as DaT single‐photon emission computed tomography, specific miRNA biosignatures alone hold promise as progression biomarkers for patients with IRBD for predicting PD and DLB clinical outcomes. Further miRNA studies in other PD at‐risk populations, such as LRRK2 mutation asymptomatic carriers or hyposmic subjects, are warranted. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society [ABSTRACT FROM AUTHOR]

The development of inexpensive, fast, and reliable screening tests for COVID-19 is, as yet, an unmet need. The present study was aimed at evaluating the usefulness of serum arylesterase activity of paraoxonase-1 (PON1) measurement as a screening test in patients with different severity levels of COVID-19 infection. We included 615 COVID-19-positive patients who were classified as asymptomatic, mildly symptomatic, severely symptomatic, or fatally symptomatic. Results were compared with 50 healthy volunteers, 330 patients with cancer, and 343 with morbid obesity. Results showed PON1 activity greatly decreased in COVID-19 compared to healthy volunteers; a receiver operating characteristics plot showed a high diagnostic accuracy. The degree of COVID-19 severity did not influence PON1 levels. Our results indicated that PON1 determination was efficient for disease diagnosis, but not for prognosis. Furthermore, patients with obesity or cancer presented alterations similar to those of COVID-19 patients. As such, elevated levels of PON1 indicate the absence of COVID-19, but low levels may be present in various other chronic diseases. The assay is fast and inexpensive. We suggest that PON1 measurement could be used as an initial, high cut-off point screening method, while lower values should be confirmed with the more expensive nucleic acid amplification test. [ABSTRACT FROM AUTHOR]

We report a pilot study on the feasibility of determinations of circulating levels of paraoxonase-1 (PON1) and compounds related to energy metabolism as biomarkers for the evaluation of patients with rectal cancer (RC), and the effects produced by neoadjuvant radiochemotherapy (NRCT). We studied 32 patients treated with radiotherapy plus capecitabine concomitant chemotherapy and 48 control subjects. We identified pre-NRCT PON1 and α-ketoglutarate as the parameters that best discriminated between RC patients and the control group. Receiver operating characteristics analysis of the combination of the two parameters showed an area under the curve (AUC) of 0.918. Moreover, patients who presented a pathological complete response (pCR) to treatment had lower plasma pre-NRCT valine concentrations (AUC of 0.826). Patients who had a relapse had lower concentrations of succinate (AUC of 0.833). The results of the present study illustrate the usefulness of investigating alterations in oxidative stress and metabolism in RC. Due to the small number of patients studied, our results must be considered preliminary, but they suggest that the determination of circulating levels of PON1 and α-ketoglutarate might be a valuable tool for the early diagnosis of RC, while the determination of valine and succinate might effectively predict pCR and the appearance of relapse. [ABSTRACT FROM AUTHOR]

Currently, a liver biopsy remains the only reliable way to precisely diagnose non-alcoholic fatty liver disease (NAFLD) and establish the severity of liver injury, presence of fibrosis, and architecture remodeling. However, the cost and the intrinsic invasive procedure of a liver biopsy rules it out as a gold standard diagnostic test, and the imaging test are not the best choice due to the price, and currently is being refined. The lack of a biomarker of NAFLD pushes to develop this new line of research. The aim of the present systematic review is to clarify and update all the NAFLD biomarkers described in the literature until recently. We highlight α-ketoglutarate and CK18-F as currently the best potential biomarker of NAFLD. However, due to methodological differences, we propose the implementation of international, multicenter, multiethnic studies with larger population size, and biopsy proven NAFLD diagnosis to analyze and compare α-ketoglutarate and CK18-F as potential biomarkers of the silent evolution of NAFLD. [ABSTRACT FROM AUTHOR]

Galectin-3 is a modulator of oxidative stress, inflammation, and fibrogenesis involved in the pathogenesis of vascular diseases. The present study sought to characterize, in patients with peripheral artery disease (PAD), the localization of galectin-3 in arterial tissue, and to analyze the relationships between the circulating levels of galectin-3 and oxidative stress and inflammation. It also sought to compare the diagnostic accuracy of galectin-3 with that of other biochemical markers of this disease. We analyzed femoral or popliteal arteries from 50 PAD patients, and four control arteries. Plasma from 86 patients was compared with that from 72 control subjects. We observed differences in the expression of galectin-3 in normal arteries, and arteries from patients with PAD, with a displacement of the expression from the adventitia to the media, and the intima. In addition, plasma galectin-3 concentration was increased in PAD patients, and correlated with serologic markers of oxidative stress (F2-isoprostanes), and inflammation [chemokine (C−C motif) ligand 2, C-reactive protein, β-2-microglobulin]. We conclude that the determination of galectin-3 has good diagnostic accuracy in the assessment of PAD and compares well with other analytical parameters currently in use. [ABSTRACT FROM AUTHOR]

We investigated the potential differential effects of antiretroviral therapies on unbalanced chemokine homeostasis and on the progression of atherosclerosis in HIV-infected patients. A two-year prospective study was performed in 67 consecutive HIV-infected patients initiating antiretroviral therapy with abacavir/lamivudine or tenofovir/emtricitabine. Circulating levels of inflammatory biomarkers, progression of subclinical atherosclerosis and expression levels of selected chemokines genes in circulating leukocytes were assessed. Control subjects showed significantly lower plasma concentrations of CRP, tPA, IL-6, and MCP-1 than HIV-infected patients at a baseline. After two years of follow up, the observed decreases in plasma inflammatory biomarker levels were only significant for MCP-1, tPA, and IL-6. The decrease in plasmaMCP-1 concentration was associated with the progression of atherosclerosis, and this effect was negligible only in patients receiving TDF-based therapy. Multivariate analysis confirmed that treatment with TDF was positively and significantly associated with a higher likelihood of subclinical atherosclerosis progression. However, the expression levels of selected genes in blood cells only showed associations with the viral load and total and HDL-cholesterol levels. Current antiretroviral treatments may partially attenuate the influence of HIV infection on certain inflammatory pathways, though patients receiving TDF therapy must be carefully monitored with respect to the presence and/or progression of atherosclerosis. [ABSTRACT FROM AUTHOR]

SARS-CoV-2 infection produces a response of the innate immune system causing oxidative stress and a strong inflammatory reaction termed 'cytokine storm' that is one of the leading causes of death. Paraoxonase-1 (PON1) protects against oxidative stress by hydrolyzing lipoperoxides. Alterations in PON1 activity have been associated with pro-inflammatory mediators such as the chemokine (C-C motif) ligand 2 (CCL2), and the glycoprotein galectin-3. We aimed to investigate the alterations in the circulating levels of PON1, CCL2, and galectin-3 in 126 patients with COVID-19 and their interactions with clinical variables and analytical parameters. A machine learning approach was used to identify predictive markers of the disease. For comparisons, we recruited 45 COVID-19 negative patients and 50 healthy individuals. Our approach identified a synergy between oxidative stress, inflammation, and fibrogenesis in positive patients that is not observed in negative patients. PON1 activity was the parameter with the greatest power to discriminate between patients who were either positive or negative for COVID-19, while their levels of CCL2 and galectin-3 were similar. We suggest that the measurement of serum PON1 activity may be a useful marker for the diagnosis of COVID-19. [ABSTRACT FROM AUTHOR]

Background: Fatty acid synthase (FASN) is an enzyme synthesized by the liver and plays an important role in lipogenesis. The present study aimed to assess whether serum FASN concentrations are altered in patients with chronic liver disease, and to investigate whether its measurement may be a useful tool in the clinical evaluation of this derangement. Methods: We investigated 93 patients with chronic liver disease (14 minimal change disease, 79 steatohepatitis) and 100 control subjects. Serum FASN concentrations were measured using ELISA. Results: Patients had a significant increase in serum FASN concentration (p<0.001), which was specifically associated with the hepatic Knodell sub-index III of portal inflammation (p=0.019). In addition, serum FASN concentrations were significantly correlated with the circulating levels of the monocyte chemoattractant protein-1 (MCP-1) (Spearman ρ=0.375; p<0.001) and type III procollagen-N-peptide (P-III-P) (Spearman ρ=0.297; p<0.001). Conclusions: Serum FASN concentrations are increased in patients with chronic liver impairment, and are associated with specific histological alterations and biochemical markers of portal inflammation. These data suggest that FASN measurement may contribute significantly to the evaluation of these patients. Clin Chem Lab Med 2009;47:1097–9. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Assessment of low-density lipoprotein targets" by T.F. Whayne in the 2013 issue.

Clinically implemented prognostic biomarkers are lacking for the 80% of colorectal cancers (CRCs) that exhibit chromosomal instability (CIN). CIN is characterised by chromosome segregation errors and double-strand break repair defects that lead to somatic copy number aberrations (SCNAs) and chromosomal rearrangement-associated structural variants (SVs), respectively. We hypothesise that the number of SVs is a distinct feature of genomic instability and defined a new measure to quantify SVs: the tumour break load (TBL). The present study aimed to characterise the biological impact and clinical relevance of TBL in CRC. Disease-free survival and SCNA data were obtained from The Cancer Genome Atlas and two independent CRC studies. TBL was defined as the sum of SCNA-associated SVs. RNA gene expression data of microsatellite stable (MSS) CRC samples were used to train an RNA-based TBL classifier. Dichotomised DNA-based TBL data were used for survival analysis. TBL shows large variation in CRC with poor correlation to tumour mutational burden and fraction of genome altered. TBL impact on tumour biology was illustrated by the high accuracy of classifying cancers in TBL-high and TBL-low (area under the receiver operating characteristic curve [AUC]: 0.88; p < 0.01). High TBL was associated with disease recurrence in 85 stages II–III MSS CRCs from The Cancer Genome Atlas (hazard ratio [HR]: 6.1; p = 0.007) and in two independent validation series of 57 untreated stages II–III (HR: 4.1; p = 0.012) and 74 untreated stage II MSS CRCs (HR: 2.4; p = 0.01). TBL is a prognostic biomarker in patients with non-metastatic MSS CRC with great potential to be implemented in routine molecular diagnostics. • Tumour break load (TBL) is a distinct feature of genomic instability. • TBL status (high or low) has a large impact on tumour biology. • TBL is a prognostic biomarker for patients with resected stage II and III microsatellite stable colorectal cancer. • TBL has the potential to be implemented in routine molecular diagnostics. [ABSTRACT FROM AUTHOR]

Aneuploidy, the unbalanced state of the chromosome content, represents a hallmark of most solid tumors, including colorectal cancer. Such aneuploidies result in tumor specific genomic imbalances, which emerge in premalignant precursor lesions. Moreover, increasing levels of chromosomal instability have been observed in adenocarcinomas and are maintained in distant metastases. A number of studies have systematically integrated copy number alterations with gene expression changes in primary carcinomas, cell lines, and experimental models of aneuploidy. In fact, chromosomal aneuploidies target a number of genes conferring a selective advantage for the metabolism of the cancer cell. Copy number alterations not only have a positive correlation with expression changes of the majority of genes on the altered genomic segment, but also have effects on the transcriptional levels of genes genome-wide. Finally, copy number alterations have been associated with disease outcome; nevertheless, the translational applicability in clinical practice requires further studies. Here, we (i) review the spectrum of genetic alterations that lead to colorectal cancer, (ii) describe the most frequent copy number alterations at different stages of colorectal carcinogenesis, (iii) exemplify their positive correlation with gene expression levels, and (iv) discuss copy number alterations that are potentially involved in disease outcome of individual patients. [ABSTRACT FROM AUTHOR]

This study provides preliminary information on the usefulness of measuring serum paraoxonase-1 (PON1) concentration and activity (and other inflammatory markers) to predict tumor recurrence in patients with urinary bladder cancer. We studied a total of 39 hospitalized patients in whom the diagnosis of urinary bladder cancer was confirmed by transurethral resection. After five years of follow-up, 29 patients presented with tumor recurrence. As control subjects, we also studied 61 healthy subjects and a further 132 hospitalized patients who had a urinary catheter-related infection due to causes other than cancer. Results showed that urinary bladder patients had lower serum PON1 concentration and activity, and higher chemokine (C-C motif) ligand 2, C-reactive protein, and procalcitonin concentrations than the control individuals. Patients with tumor recurrence had significantly lower serum PON1 concentration than patients without tumor recurrence. The mean area under the curve of the receiver operating characteristics plot for serum PON1 concentration in discriminating patients with and those without tumor recurrence was 0.755 and the best combination of sensitivity and specificity was obtained at PON1 = 100 mg/L (0.72 and 0.80, respectively). Establishing this value as a cut-off, positive predictive value was = 0.91, and negative predictive value was = 0.50. These results suggest that the measurement of serum PON1 concentration may be a high-sensitivity marker of tumor recurrence in urinary bladder cancer patients. [ABSTRACT FROM AUTHOR]

Objectives Identification of biochemical markers to diagnose bloodstream infections in patients with a central venous catheter (CVC) inserted is an active research pursuit. Paraoxonase-1 (PON1) is an enzyme participating in the innate immune system protecting against toxic substances and infectious agents. We investigated the relationships between serum PON1 alterations and the characteristics of infection in a group of patients with a CVC implant. Methods Patients (n = 114) who had had an inserted CVC removed because of infection or because the usefulness was at an end, and 407 healthy volunteers were recruited. In all participants we measured serum PON1 lactonase and paraoxonase activities, PON1 concentration and genetic polymorphisms, together with levels of the chemokine (C–C motif) ligand 2 (CCL2), procalcitonin and C-reactive protein (CRP). Results Patients with an acute concomitant infection (ACI) had higher CCL2, CRP and procalcitonin concentrations than the control group, together with lower paraoxonase and lactonase activities and specific activities. The areas under the curve of the receiver operating characteristic plots for paraoxonase and lactonase specific activities in the discrimination between patients with or without and ACI were 0.81 (0.73–0.89) and 0.81 (0.71–0.89), respectively, indicating the high diagnostic accuracy of these parameters. Conclusion This preliminary study suggests that the measurement of PON1 may be useful as a tool for the diagnosis of ACI in patients with an indwelling CVC. [ABSTRACT FROM AUTHOR]

Abstract: Background: Liver steatosis is frequent in patients with chronic hepatitis viral infections. Intracellular fatty acid synthase (FASN) seems to play a substantial role in its pathogenesis. FASN can also be found in circulation and is significantly increased in HIV-infected individuals, especially if they are co-infected with hepatitis C virus (HCV). Objectives: To assess whether serum FASN concentration is also increased in patients with chronic hepatitis viral infections and its relationship with liver steatosis. Study design: Samples and associated data were obtained from stored collections in our institutions from patients with chronic infections with either hepatitis B virus (HBV, cHB, n =60), HCV (cHC, n =81) or co-infection (n =29). Results: The incidence of liver steatosis was significantly (p <0.001) different among groups (23.7% in cHB, 34.2% in cHC and 69.2% in co-infected). A similar trend was observed for changes in serum ALT [in μKat/L, 1.41 (0.08), 1.62 (0.08) and 1.95 (0.16) respectively; p =0.02] and serum FASN [in ng/mL, 9.44 (1.28), 16.38 (1.93) and 31.47 (4.26) respectively; p <0.001]. Serum FASN concentration was related to the degree of liver steatosis, and was correlated with serum ALT values when the whole group was considered (ρ =0.207; p =0.007). Conclusions: Serum FASN concentration is significantly increased in patients with chronic hepatitis viral infections and correlated with the degree of liver steatosis. These findings may represent a basis for further studies searching non-invasive biomarkers with either diagnostic or prognostic value. [Copyright &y& Elsevier]