Occult hepatitis C virus (HCV) infection of patients with abnormal liver function tests of unknown originwho are anti-HCV and serum HCV RNA negative but who have HCV RNA in the liver has been described. As HCV replicates in the liver cells of these patients, it could be that the amount of circulating viral particles is under the detection limit of the most sensitive techniques. To prove this hypothesis, serum samples from 106 patients with occult HCV infection were analyzed. Two milliliters of serum was ultracentrifuged over a 10% sucrose cushion for 17 h at 100,000 ؋ g av , where av means average, and HCV RNA detection was performed by strand-specific real-time PCR. Out of the 106 patients, 62 (58.5%) had detectable serum HCV RNA levels after ultracentrifugation, with a median load of 70.5 copies/ml (range, 18 to 192). Iodixanol density gradient studies revealed that HCV RNA was positive at densities of 1.03 to 1.04 and from 1.08 to 1.19 g/ml, which were very similar to those found in the sera of patients with classical chronic HCV infection. The viral genome of hepatitis C virus (HCV) is a 9.6-kb linear single-stranded RNA molecule of positive polarity that replicates via an HCV RNA strand of negative polarity (18).Chronic HCV infection is a progressive disease that may lead to liver cirrhosis and hepatocellular carcinoma (6, 21). The hallmark of chronic hepatitis C is the presence of anti-HCV and HCV RNA in serum for more than 6 months after acute infection. Recently, a new form of chronic HCV infection called "occult HCV infection," characterized by the presence of genomic HCV RNA in liver in the absence of anti-HCV and serum HCV RNA, in patients with abnormal liver function tests of unknown etiology was described (3). In 84% of patients with occult HCV infection, the negative-polarity (antigenomic) HCV RNA strand was also detected in liver, indicating that the virus was replicating. Furthermore, 70% of these patients had HCV RNA in peripheral blood mononuclear cells (PBMCs) (3), and viral replication in these cells was also reported (4).Since HCV replicates in the livers of patients with occult HCV infection, the reason why HCV RNA is not detected in serum is unknown. One possible explanation is that the number of circulating viral particles is too low to be detected even using the most sensitive reverse transcription (RT)-PCR techniques.In the present study, by using ultracentrifugation and a sensitive real-time PCR technique, we have demonstrated that sera from patients with occult HCV infection contain low amounts of viral particles and that the physical characteristics of these virions are similar to those found in patients with classical chronic HCV infection. MATERIALS AND METHODS Patients.One hundred six patients (74 males) with occult HCV infection were analyzed in this study. Patients had abnormal liver function tests, were anti-HCV negative (INNOTEST HCV Ab IV; Innogenetics, Ghent, Belgium), and did not have serum HCV RNA levels tested by real-time RT-PCR (see below). Other causes of liver disease...

An asynchronous phase-shifting method based on principal component analysis (PCA) is presented. No restrictions about the background, modulation, and phase shifts are necessary. The presented method is very fast and needs very low computational requirements, so it can be used with very large images and/or very large image sets. The method is based on obtaining two quadrature signals by the PCA algorithm. We have applied the proposed method to simulated and experimental interferograms, obtaining satisfactory results.

Abstract:We have been reporting several new techniques of analysis and synthesis applied to Phase Shifting Interferometry (PSI). These works are based upon the Frequency Transfer Function (FTF) and how this new tool of analysis and synthesis in PSI may be applied to obtain very general results, among them; rotational invariant spectrum; complex PSI algorithms synthesis based on simpler first and second order quadrature filters; more accurate formulae for estimating the detuning error; output-power phase noise estimation. We have made our cases exposing these aspects of PSI separately. Now in the light of a better understanding provided by our past works we present and expand in a more coherent and holistic way the general theory of PSI algorithms. We are also providing herein new material not reported before. These new results are on; a well defined way to combine PSI algorithms and recursive linear PSI algorithms to obtain resonant quadrature filters.

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Our data disclose a previously undescribed pattern of cytokine alteration that is relevant to determine increased needs of EPO in hemodialysis patients. The present results have potential applicability in designing strategies to improve EPO resistance.