Factor XI antigen and activity in human platelets

Washed platelets, contaminated with less than 0.20% plasma factor XI, were examined for the presence of factor XI antigen and activity. These platelets contained a factor-XI-like coagulant activity (0.67 +/- 0.11 U/10(11) platelets) that remained constant after successive washes. By means of indirect immunofluorescence, a monospecific antibody to factor XI showed specific staining of both normal platelets and platelets from patients deficient in plasma factor XI. Radiolabeled Triton extracts of washed platelets and labeled purified factor XI solutions were analyzed for factor XI antigen by Staph A immunoprecipitation analysis using antibody to purified plasma factor XI followed by SDS gel electrophoresis. On unreduced gels, the platelet material ran as a single band having an apparent molecular weight of 220,000 daltons, whereas purified plasma factor XI gave a single band at 160,000 daltons. On reduced gels, the platelet material analyzed as a single band at 52,000 daltons, whereas purified factor XI gave a single band of 80,000 daltons. Analysis of a partially purified factor XI preparation from platelets by immunoelectrophoresis revealed that the platelet preparation displayed a slightly lower cathodal electrophoretic mobility at pH 8.6 than did plasma factor XI and yet appeared to possess complete antigenic identity with plasma factor XI. These results indicate that platelets possess a form of factor XI that exists as a disulfide-linked 52,000-dalton tetramer in contrast to the plasma form that circulates as a 80,000-dalton disulfide-linked dimer.     

Preventive and curative effect of methanolic extract of Gardenia gummifera Linn. f. on thioacetamide induced oxidative stress in rats

ObjectiveTo evaluate the antioxidant and antihepatotoxic effect of methanolic extract of Gardenia gummifera Linn. f. root (MEGG) on thioacetamide (TAA) induced oxidative stress in male Wistar rats.MethodsIn the preventive study, rats were administered with 125 and 250 mg/kg of MEGG for 9 days prior to TAA administration (100 mg/kg s.c.). In post-treatment groups, rats were treated with MEGG at doses of 125 and 250 mg/kg, 2, 24 and 48 h after TAA intoxication. Silymarin was used as a standard drug control (100 mg/kg). Hepatotoxicity was assessed by quantifying the serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH). The antioxidant potential of MEGG was evaluated by the estimation of catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione-S-transferase (GST), reduced glutathione (GSH) and lipid peroxidation [thiobarbituric acid reactive substances (TBARS)] in hepatic and renal tissues. Histopathological changes were also evaluated.ResultsMEGG significantly (P≤0.05) prevented the elevation of serum AST, ALT, ALP, LDH and tissue malondialdehyde levels in both experimental groups, when compared to the TAA alone treated groups. The rats receiving TAA plus MEGG exhibited significant (P≤0.05) increases in hepatic and renal antioxidant activities including GSH, GST, GR, GPx and CAT levels. Quantification of histopathological changes also supported the dose dependent protective effects of MEGG.ConclusionsThese observations suggest that MEGG has dose dependent hepatoprotective and antioxidant effect against TAA induced oxidative stress.     

A comparison of least squares and conditional maximum likelihood estimators under volume endpoint censoring in tumor growth experiments

Measurements in tumor growth experiments are stopped once the tumor volume exceeds a preset threshold: a mechanism we term volume endpoint censoring. We argue that this type of censoring is informative. Further, least squares (LS) parameter estimates are shown to suffer a bias in a general parametric model for tumor growth with an independent and identically distributed measurement error, both theoretically and in simulation experiments. In a linear growth model, the magnitude of bias in the LS growth rate estimate increases with the growth rate and the standard deviation of measurement error. We propose a conditional maximum likelihood estimation procedure, which is shown both theoretically and in simulation experiments to yield approximately unbiased parameter estimates in linear and quadratic growth models. Both LS and maximum likelihood estimators have similar variance characteristics. In simulation studies, these properties appear to extend to the case of moderately dependent measurement error. The methodology is illustrated by application to a tumor growth study for an ovarian cancer cell line. Copyright © 2012 John Wiley & Sons, Ltd.     

Recombinant immunoblot assay reaction patterns and hepatitis C virus RNA in blood donors and non-A, non-B hepatitis patients

To establish the value of the second-generation recombinant immunoblot assay (RIBA-2) and cDNA polymerase chain reaction (cDNA PCR) for confirmation of hepatitis C virus (HCV) infection, anti-HCV reaction patterns and the presence of HCV RNA were examined in 610 blood donors and 255 non-A, non-B hepatitis patients who were positive or indeterminate in RIBA-2. Of RIBA-2-positive donors (n = 191) and patients (n = 224), 75.4 and 89.7 percent, respectively, were HCV RNA positive. The most frequently observed anti-HCV recognition patterns in HCV RNA-positive donors and patients were c22, c33c, and c100 and/or 5- 1-1 (67.3%, 57.7%) and c22, c33c (24.8%, 29.3%). Among subjects with a RIBA-2-indeterminate result, HCV RNA was detected more often in patients (n = 31) than in donors (n = 419): 67.7 and 2.1 percent, respectively. In viremic persons with single-band reactivity in RIBA-2, this reactivity was always directed against either c22 or c33c. HCV RNA was detected by cDNA PCR in none of 162 persons with only anti-c100 and/or anti-5-1-1 reactivity. Therefore, RIBA-2 reactivity against c100 in combination with 5-1-1 should not be considered positive but indeterminate. In RIBA-2-indeterminate persons, HCV RNA detection is necessary for reliable confirmation of HCV infection.     

Reliability of the third-generation recombinant immunoblot assay for hepatitis C virus

BACKGROUND: In a confirmatory laboratory, the second-generation recombinant immunoblot assay (RIBA-2) was replaced by the third- generation RIBA (RIBA-3) in March 1993. The aim of this validation study was to compare the sensitivity and specificity of RIBA-2 and RIBA- 3 in a routine setting, by using a validated hepatitis C virus (HCV) RNA polymerase chain reaction to establish plasma viremia. STUDY DESIGN AND METHODS: RIBA-2 testing was performed (March 1991-March 1993) in 593 HCV RNA-positive and 1498 HCV RNA-negative subjects. RIBA-3 testing was performed (March 1993-May 1994) in 220 HCV RNA-positive and 530 HCV RNA-negative subjects. All samples reacted for anti-HCV in enzyme- linked immunosorbent assay. RESULTS: In HCV RNA-positive individuals, the sensitivity of RIBA-3 was significantly higher than that of RIBA-2 (99.5% vs. 93.3%, p = 0.0005). This was not caused by inclusion of the NS5 antigen, but by a higher sensitivity of the antigens c33 and c100 (RIBA-2: 94.3% and 62.6%; RIBA-3: 99.5% and 88.6%). Replacement of the c22 and c100 recombinant proteins by synthetic peptides significantly reduced nonspecific reactivity against these antigens (p < 0.0001). Unfortunately, increased nonspecific reactivity against the modified c33 antigen and the new NS5 antigen canceled out this effect. Two-band reactivity occurred more often in nonviremic persons than in viremic persons (32.7% vs. 8.2%, p < 0.0001). Risk factors for HCV infection were less frequently observed in 11 blood donors with two-band reactivity than in 6 blood donors with other positive RIBA-3 patterns (18% vs. 83%, p = 0.03). CONCLUSION: The higher sensitivity of RIBA-3 significantly reduced the number of indeterminate test results in HCV RNA-positive persons. Confirmatory laboratories must be aware of the frequent occurrence of nonspecific, isolated reactivity and even nonspecific, two-band reactivity in anti-HCV enzyme-linked immunosorbent assay-reactive blood donors.     

The eye in acute leukaemia. 1. Dosimetric analysis in cranial radiation prophylaxis

The dose to the ocular lens during standard cranial irradiation prophylaxis in childhood acute lymphoblastic leukaemia (ALL) has been studied both in patients and in an anthropomorphic phantom. Doses to the lens depend on patient set-up and in order that this is minimised, a simple immobilisation technique is recommended. Surface thermoluminescent dosimeter (TLD) measurements seriously underestimate the dose received by the ocular lens. Previous measurements made in a phantom have used a large volume ionisation chamber and therefore the minimum cataractogenic dose of 400 cGy for a fractionated treatment is an underestimate. The exact position of the anterior orbital field margin and thus its distance behind the surface of the eye is also important as regards lens dose. Data from the phantom demonstrate accurately the dose gradient through the eye during standard cranial prophylaxis and may explain the lower incidence of leukaemic relapse in the posterior segment of the eye, and yet explain the persistence of isolated anterior chamber relapses.