Mechanism of deoxyadenosine-induced catabolism of adenine ribonucleotides in adenosine deaminase-inhibited human T lymphoblastoid cells

Loss of ATP accompanying accumulation of dATP has recently been reported to occur in the erythrocytes and lymphoblasts of patients with T lymphocytic leukemia during treatment with deoxycoformycin, an inhibitor of adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4) that causes the accumulation of deoxyadenosine. We have studied the mechanisms responsible for adenine ribonucleotide depletion in cultured human CEM T lymphoblastoid cells treated with deoxycoformycin and deoxyadenosine. Accumulation of dATP was accompanied by depletion of total soluble adenine ribonucleotides without change in the adenylate energy charge, by the route ATP --> AMP --> IMP --> inosine --> hypoxanthine; conversion of IMP to AMP and de novo purine synthesis were inhibited in these cells. ATP degradation did not occur in a mutant of CEM that was incapable of phosphorylating deoxyadenosine, or in a B cell line with very limited ability to accumulate dATP. We found that dATP and ATP were both able to stimulate markedly the deamination of AMP by lymphoblast AMP deaminase; dAMP was a poor substrate for this enzyme (K(m) = 2.4 mM, vs. 0.4 mM for AMP). Similarly, dATP as well as ATP caused marked activation of IMP dephosphorylation by a lymphoblast cytoplasmic nucleotidase. Inhibition of intracellular AMP deaminase with coformycin prevented degradation of adenine ribonucleotides without affecting dATP accumulation. We propose that ATP-dependent phosphorylation of deoxyadenosine generates ADP and AMP. Simultaneously, dATP accumulation stimulates deamination of AMP, but not dAMP, and the dephosphorylation of IMP to inosine. Coupling of AMP degradation to ATP utilization in deoxyadenosine phosphorylation maintains the adenylate energy charge despite net depletion of cellular ATP.     

Protective effect of methylprednisolone and of intermittent hepatic pedicle clamping during liver vascular inflow occlusion in the rat

BACKGROUND/AIMS: One of the main causes of postoperative morbidity and mortality following major hepatic resection is hepatic ischemia deliberately designed to reduce intraoperative hemorrhage. This study assessed the effects of intermittent or continuous hepatic ischemia and reperfusion with or without methylprednisolone pretreatment in the rat. METHODOLOGY: One hundred and eighty rats were divided into 3 groups undergoing hepatic ischemia of 60, 90, and 120 minutes total duration. Each group of rats were subdivided to receive either a continuous Pringle maneuver, or 30 min or 15 min of intermittent liver pedicle clamping. Ten minutes before ischemia induction, 10 rats from each group were pretreated with intravenous 3 mg/100 g bw methylprednisolone. RESULTS: With continuous hepatic pedicle clamping the rat survival rates inversely correlated with the duration of ischemia (survival: 70%, 40%, and 20% with ischemia of 60, 90, and 120 min). Survival rates at 15-min and 30-min intermittent ischemia groups were significantly higher than in the continuous clamping group (p<0.05). Methylprednisolone pretreatment did not significantly increase survival but resulted as a significant reduction in liver enzyme release (AST, ALT), at 90 min (p<0.05) and at 120 min (p<0.05) in the continuously clamped groups. When ischemia lasted 120 min, methylprednisolone pretreatment was associated with higher preservation of ATP liver content (p<0.05). CONCLUSIONS: This study confirms that intermittent hepatic pedicle clamping significantly improves survival in rats undergoing hepatic vascular inflow occlusion with a decrease in transaminase release and greater maintenance of intrahepatic ATP after prolonged total ischemia when animals were pretreated with methylprednisolone.     

GlObal Secondary Prevention strategiEs to Limit event recurrence after myocardial infarction: the GOSPEL study. A trial from the Italian Cardiac Rehabilitation Network: rationale and design.

BACKGROUND: Cardiac rehabilitation programmes are a proven treatment for individuals with recent myocardial infarction, resulting in reduced morbidity and mortality compared to usual care. Unfortunately, following completion of a cardiac rehabilitation programme, risk factors and lifestyle behaviours may deteriorate. The GlObal Secondary Prevention strategiEs to Limit event recurrence after myocardial infarction (GOSPEL) study investigates the benefits of a programme of continued educational and behavioural interventions to achieve optimal long-term secondary prevention goals. DESIGN: This will be a multicentre, randomized, controlled study carried out in 78 Italian cardiac rehabilitation centres. METHODS: After completion of an initial cardiac rehabilitation programme, patients with recent (<3 months) myocardial infarction were randomized to either a long-lasting (over 3 years) multifactorial continued educational and behavioural programme (intensive approach) or usual care (control) group. Intensive approach patients participated in extensive cardiac rehabilitation sessions, monthly from months 1 to 6, then every 6 months for 3 years. Each session consisted of aerobic exercise, comprehensive lifestyle and risk factor counselling, and clinical assessment. Usual care patients returned to their family physicians' care, and attended the reference centre only for the 6-month and then annual scheduled assessment. The efficacy of the two different strategies will be evaluated in terms of morbidity and mortality as primary endpoint. RESULTS: From January 2001 through December 2002, 3241 patients were enrolled. Results will be available in mid 2006. CONCLUSIONS: The GOSPEL trial, the rationale and design of which we present here, was designed to test a new strategy of secondary prevention delivery and to raise standards of long-term secondary prevention in Italy. With a cohort of over 3200 patients, GOSPEL is the largest randomized, multifactorial lifestyle and risk factor intervention trial after myocardial infarction conducted so far.     

Clinical relevance of soluble HLA class I molecules in Waldenstrom Macroglobulinemia

Objectives: Waldenstrom Macroglobulinemia (WM) is a B‐cell neoplasm characterised by secretion of IgM by lymphoplasmacytic bone marrow cells and by cytopenias and hypogammaglobulinemia in a subset of patients. Beta‐2 microglobulin (b2m) is a major prognostic factor in WM and the heavy chain of HLA class I molecules, which are known to have immunosuppressive properties and have been implicated in the pathogeny of several malignancies. Methods: We assessed the serum levels of the total soluble HLA‐I molecules and the HLA‐Gs molecules in 105 patients with IgM‐related disorders [WM (n = 42) and IgM MGUS (n = 63)], and compared the results to 41 healthy subjects. Results: We found higher levels of HLA‐Is in WM, compared to IgM MGUS and healthy donors. HLA‐Gs levels were similar in WM and in IgM MGUS, but higher than in healthy donors. The association between HLA‐Is at the cut‐off of 1.8 μg/mL and known markers of poor prognosis was then evaluated among WM patients using univariate and multivariate methods. Based on this, high HLA‐Is level was strongly associated with high serum β2M level >3 mg/L [OR = 2, (CI 95% 1.1–5.7); P = 0.04], age > 65 yrs [OR = 1.5, (CI 95% 0.5–4.1), P = 0.06] and haemoglobin ≤11.5 g/dL [OR = 3.3, (CI 95% 1.2–9.7); P = 0.03]. High levels of serum HLA‐Is were also found in patients with cryoglobulinemia, however irrespectively of WM or IgM‐MGUS status. Conclusion: Together our results suggest a possible role for soluble MHC class I molecules in WM disease. Further investigations are necessary to further demonstrate the prognostic impact of soluble MHC class I molecules in Waldenstrom Macroglobulinemia.     

Radionuclide angiocardiography in evaluation of patients after repair of transposition of the great arteries

The ability of first pass radionuclide angiocardiography to detect and quantitate residual intracardiac shunts and systemic venous obstruction after repair of transposition of the great arteries was evaluated in 29 children. Information from radionuclide scans was compared with data obtained during cardiac catheterization. Three children had a residual right to left shunt detected with both methods. There was good agreement between radionuclide and catheterization quantitation of left to right shunt in the nine patients with a residual defect, five of whom had significant shunting. Nineteen patients with signs suggesting superior vena caval obstruction were evaluated with both radionuclide and catheterization methods. In eight, complete obstruction was detected with both techniques; in one additional patient, partial obstruction was found on catheterization only. One of six patients evaluated for possible inferior vena caval obstruction was identified with both techniques. In the group as a whole, information obtained with radionuclide angiography correlated well with cardiac catheterization data in evaluation of residual shunts and obstruction to systemic venous return.     

A reappraisal of the Rb1 gene abnormalities in the diagnosis of parathyroid cancer

OBJECTIVES: Some histological features may suggest the malignant nature of a parathyroid tumour. However, the diagnosis of parathyroid cancer can only be definitively established in the presence of local invasion or metastases. DESIGN: We further investigated the role of the retinoblastoma gene (Rb1) and the breast cancer susceptibility gene (BRCA2) in the differential diagnosis between benign and malignant parathyroid tumours by evaluating loss of heterozygosity (LOH) at these loci and Rb protein (pRb) immunohistochemistry. PATIENTS AND MEASUREMENTS: Fifty-three parathyroid adenomas from patients with sporadic primary hyperparathyroidism (PHPT) and 10 parathyroid cancer specimens were studied. Microsatellite polymorphisms at the Rb1 and BRCA2 loci were polymerase chain reaction (PCR) amplified from each patient's paired tumour and leucocyte DNA samples, using oligonucleotide primers flanking the repeat sequence. Immunohistochemical staining of pRb was carried out using a monoclonal antibody. RESULTS: All but one of the 53 tumour-leucocyte pairs was informative for at least one of the three polymorphic markers of the Rb1 gene. Fifteen adenomas (28.8%) showed LOH. Regarding the BRCA2 gene, 46 tumour-leucocyte pairs were informative and LOH was present in eight (17.4%). All six carcinomas had LOH for at least one marker at the Rb1 locus. LOH for the BRCA2 microsatellite was found in three of the five informative primary tumour samples. Immunohistochemical analysis revealed that all adenomas were positive and the number of pRb-positive cells varied significantly among different samples. The mean percentage of stained cells was 15.7%. Eleven of the 30 (36.7%) adenomas showed sparse positive staining, 13 (43.3%) intermediate staining and six (20%) extensive staining. All parathyroid cancers were entirely negative for pRb immunostaining. CONCLUSIONS: Inactivation of the Rb1 gene is a common event in parathyroid tumorigenesis. Retention of heterozygosity seems to exclude parathyroid malignancy, which is suggested by the combined finding of LOH and lack of protein expression.     

Simian virus 40-like sequences from early and late regions in human thyroid tumors of different histotypes

Simian virus 40 (SV40) sequences were investigated in human thyroid tumors of different histotypes, Graves' disease thyroid specimens, normal thyroid tissues, and peripheral blood mononuclear cells (PBMC) of healthy donors. Specific SV40 large T antigen (Tag) sequences were detected, by PCR and filter hybridization, in human thyroid tumors with a frequency ranging from 66% in papillary thyroid carcinomas (PTC) to 100% in anaplastic thyroid carcinomas (ATC). SV40 was revealed in 60% and 100% of normal thyroid tissues adjacent to PTC and ATC, respectively, but in only 10% of control normal thyroid tissues (NTT) from patients affected by multinodular goiter. Thyroid tissues from patients affected by the Graves' disease were found to be SV40 positive with a frequency of 20%. In agreement with previous investigations, the presence of SV40 sequences was detected in 25% of PBMC of healthy individuals. SV40 Tag mRNA was detected by RT-PCR, whereas the viral oncoprotein was revealed by immunohistochemistry with a specific monoclonal antibody. The high prevalence of SV40 footprints in human thyroid tumors indicates that the oncogenic virus may participate as a cofactor in the onset/progression of specific human thyroid cancers. Detection of SV40 sequences in NTT adjacent to thyroid cancers suggests that the viral infection may spread from transformed cells to normal cells surrounding the tumor. The presence of the SV40 footprint in PBMC implies that blood cells are vectors of the virus in other tissues of the host.