Characterizing fretting damage in different test media for cardiovascular device durability testing.

In vitro durability tests of cardiovascular devices are often used to evaluate the potential for fretting damage during clinical use. Evaluation of fretting damage is important because severe fretting can concentrate stress and lead to the loss of structural integrity. Most international standards call for the use of phosphate buffered saline (PBS) for such tests although there has been little evidence to date that the use of PBS is appropriate in terms of predicting the amount of fretting damage that would occur in vivo. In order to determine an appropriate test media for in vitro durability tests where fretting damage is being evaluated, we utilized an in vitro test that is relevant to cardiovascular devices both in terms of dimensions and materials (nitinol, cobalt-chromium, and stainless steel) to characterize fretting damage in PBS, deionized water (DIW), and heparinized porcine blood. Overall, tests conducted in blood were found to have increased levels of fretting damage over tests in DIW or PBS, although the magnitude of this difference was smaller than the variability for each test media. Tests conducted in DIW and PBS led to mostly similar amounts of fretting damage with the exception of one material combination where DIW had greatly reduced damage compared to PBS and blood. Differences in fretting damage among materials were also observed with nitinol having less fretting damage than stainless steel or cobalt-chromium. In general, evaluating fretting damage in PBS or DIW may be appropriate although caution should be used when selecting test media and interpreting results given some of the differences observed across different materials.

Sodium Hypochlorite Treatment and Nitinol Performance for Medical Devices.

Processing of nitinol medical devices has evolved over the years as manufacturers have identified methods of reducing surface defects such as inclusions. One recent method proposes to soak nitinol medical devices in a 6% sodium hypochlorite (NaClO) solution as a means of identifying surface inclusions. Devices with surface inclusions could in theory then be removed from production because inclusions would interact with NaClO to form a visible black material on the nitinol surface. To understand the effects of an NaClO soak on performance, we compared as-received and NaClO-soaked nitinol wires with two different surface finishes (black oxide and electropolished). Pitting corrosion susceptibility was equivalent between the as-received and NaClO-soaked groups for both surface finishes. Nickel ion release increased in the NaClO-soaked group for black oxide nitinol, but was equivalent for electropolished nitinol. Fatigue testing revealed a lower fatigue life for NaClO-soaked black oxide nitinol at all alternating strains. With the exception of 0.83% alternating strain, NaClO-soaked and as-received electropolished nitinol had similar average fatigue life, but the NaClO-soaked group showed higher variability. NaClO-soaked electropolished nitinol had specimens with the lowest number of cycles to fracture for all alternating strains tested with the exception of the highest alternating strain 1.2%. The NaClO treatment identified only one specimen with surface inclusions and caused readily identifiable surface damage to the black oxide nitinol. Damage from the NaClO soak to electropolished nitinol surface also appears to have occurred and is likely the cause of the increased variability of the fatigue results. Overall, the NaClO soak appears to not lead to an improvement in nitinol performance and seems to be damaging to the nitinol surface in ways that may not be detectable with a simple visual inspection for black material on the nitinol surface.

ET-1 plasma levels during cold stress test in sclerodermic patients.

Endothelial cell injury in blood vessels of small arteries and capillaries is considered the primary event in the pathogenesis of systemic sclerosis (SSc). Because endothelin-1 (ET-1) is mainly released in the site of endothelial cell damage, thereby inducing a potent vasoconstriction, it was our intention to study ET-1 release in a group of SSc patients during a cold pressor test (CPT). Twelve SSc patients and a control group of 10 healthy subjects underwent CPT. Blood samples for ET-1 assay were collected at 90 and 180 seconds of exposure to cold stress. Heart rate and blood pressure were recorded at the same intervals. A capillaroscopic examination was performed in both groups before and after CPT. We observed significantly higher levels of plasma ET-1 in SSc patients compared with those of the control group at baseline (P=0.007) and at 90 (P=0.006) and 180 seconds (P=0.03) of CPT. During the test, the capillaroscopic examination showed a dramatic worsening of the vascular picture that was parallel to the increase in ET-1 plasma levels. This suggests that higher ET-1 plasma levels can have a part in the acute vascular reactivity of SSc patients undergoing CPT.

Cardiac valve involvement in systemic lupus erythematosus and primary antiphospholipid syndrome: lack of correlation with antiphospholipid antibodies.

The aim of this study was to determine the prevalence of cardiac valve disease in systemic lupus erythematosus or in patients with primary antiphospholipid syndrome and to assess the role of the antiphospholipid antibodies as risk factor for endocardial lesions. We studied 39 consecutive patients with systemic lupus erythematosus (mean age 34 +/- 12 years, 38 female and one male), 20 women with primary antiphospholipid syndrome (mean age 32 +/- 4 years) and 20 normal subjects (mean age 35 +/- 8 years, 15 female and five male). All patients with primary antiphospholipid syndrome had increased levels of serum anticardiolipin antibodies and recurrent fetal abortions; some of them also had arterial and/or venous thrombosis and/or thrombocytopenia. M-mode, two-dimensional and Doppler echocardiography were performed in all patients. IgG anticardiolipin antibodies were measured by an enzyme-linked immunosorbent assay. Valvular lesions were observed in 15 patients (38%) with systemic lupus erythematosus. These abnormalities included: mitral valve thickening or vegetation, mitral valve prolapse and aortic valve vegetation; mitral, aortic and tricuspid regurgitation; mitral stenosis. None of the patients with primary antiphospholipid syndrome and of the normal subjects was found to have valvular abnormalities. In systemic lupus erythematosus, high levels of anticardiolipin antibodies were detected in 73% of the patients with valvular lesions and in 67% of the patients without valvular lesions (P > 0.05). We conclude that valvular involvement is frequent in patients with systemic lupus erythematosus but it is apparently unrelated to antiphospholipid autoimmunization.

Anti 70 kDa heat shock protein antibodies in sera of patients affected by autoimmune and non-autoimmune thyroid diseases.

Twenty eight patients (25F, 3M) affected by autoimmune and non-autoimmune thyroid diseases were studied. HSP 70 antibodies were present in 21.4% of patients. Five of them were affected by Graves' disease and one by De Quervain's thyroiditis. The HSP 70 antibodies mean values of patients were significantly higher than the normals (p < 0.05). This datum was confirmed by Western blotting. The presence of HSP 70 antibodies in the sera of those patients may support the link between the protein and the thyroid autoimmune processes.

Anti-cardiolipin antibodies in autoimmune thyroid diseases.

OBJECTIVE: In recent years anti-phospholipid antibodies have gained much attention since they are frequently associated with thrombosis, recurrent abortion, and thrombocytopenia. Besides disease-specific autoantibodies, other autoantibodies reactive with both organ and non-organ specific autoantigens have been found in patients with autoimmune thyroid diseases. Therefore the objective of this study was to evaluate the presence and significance of anti-phospholipid antibodies in untreated patients with different forms of autoimmune thyroid diseases. PATIENTS AND METHODS: Thirty-one patients (26 females, five males; mean age 42.5 years) affected by different autoimmune thyroid diseases were studied. Fourteen patients were affected by Graves' disease, eight by silent thyroiditis, five by Hashimoto's thyroiditis. Four patients with Graves' disease in remission were also evaluated. Anti-cardiolipin antibodies were detected by enzyme linked immunosorbent assay. In five Graves' disease patients anti-cardiolipin antibodies were evaluated before and after 3 months of therapy with methimazole. RESULTS: Seventeen out of 31 patients were positive for IgG and/or IgM anti-cardiolipin antibodies, the highest levels occurring in three Graves' disease patients with severe thyrotoxicosis. In four of five Graves' patients evaluated before and after methimazole therapy, anticardiolipin antibodies decreased following treatment. None of the patients with increased IgG and/or IgM anticardiolipin antibodies showed clinical manifestations of the anti-phospholipid syndrome during our observation which ranged from 1 to 5 years. CONCLUSIONS: Our results showed an increased incidence of anti-cardiolipin antibodies in patients affected by autoimmune thyroid diseases. However, these autoantibodies seem merely to represent a non-specific marker of immune dysregulation.

[Otosclerosis. Immunoendocrine and infective aspects]. / Otosclerosi. Aspetti immunoendocrini ed infettivi.

The etiopathogenesis of otosclerosis is yet scarcely known. In this paper we focus on the immunoendocrine and infective aspects of the disorder. According to recent investigations the role played by cytokines and calcitonin's receptors appears to be crucial in the pathogenesis of otosclerosis. In addition, the ultrastructural and immunohistochemical evidence of virus specific antigens around the active otosclerotic focus suggest that virus can trigger and maintain an inflammatory disease.

CD5+ B lymphocytes and CD4+ CD45RA+ T cells in Graves' disease.

Fifteen patients affected by new-onset Graves' disease with ophthalmopathy have been examined for lymphocyte subset phenotypes by two-colour cytometric analysis. CD5+ B cells were significantly increased in comparison to the normal population (43.2 +/- 20.6% versus 19.5 +/- 6.9%; p < 0.0009); total T cells showed a normal amount (70.4 +/- 9.6%), but the levels of THLADR+ cells were significantly increased in comparison to the control group (13.7 +/- 10.5% versus 4.7 +/- 3.2%; p < 0.007). The characterization of the subset suppressor-inducer CD4+ CD45RA+, evaluated as percentage of the total CD4+ T cells, showed a significant decrease in comparison with the control group (43.8 +/- 13.5% versus 52.3 +/- 6.5%; p < 0.03). Serum immunoglobulin evaluation showed a statistically significant increase of IgM (p < 0.05) and a significant decrease of IgA (p < 0.02). A statistical correlation between IgM levels and percentage of CD5+ B cells has been found (p < 0.04). The defect of suppressor-inducer T cell subset, along with the increase of CD5+ B cells may contribute to the pathogenetic mechanism of the disease in patients with a genetically-induced aberrant immune response.

HLA-DR and DQ antigens and anticardiolipin antibodies in women with recurrent spontaneous abortions.

IgG anticardiolipin antibodies (ACL) have been shown to occur in a high proportion of women with repeated unexplained miscarriages. Forty-nine women with unexplained recurrent spontaneous abortions (RSA), previously assayed for the presence of ACL by an enzyme-linked immunoabsorbent assay, were typed for HLA-DR and DQ antigens by the classical microlymphocytotoxicity test. Twenty-five women were positive for ACL and 24 were negative. HLA-DR7 was found in 24.5% of 49 habitually aborting women vs. 28% of healthy controls; but the DR7 frequency was 40% in ACL positive patients vs. 8.3% in ACL negative patients (P = 0.011). These results show that in the Italian population an association between HLA-DR7 antigen and ACL is present in women with unexplained RSA, suggesting that HLA-DR genes might control the susceptibility to specific autoantibody production.

Gastric parietal cell antibodies: demonstration by immunofluorescence of their reactivity with surface of the gastric parietal cells.

Viable, intact gastric cells were obtained by pronase digestion of inverted rat stomach. The cell suspensions contained two main distinct cell population, i.e. 'large' cells (mean diameter 16 microns) and 'small' cells (mean diameter 8.5 microns). By indirect immunofluorescence on smears of dispersed rat gastric cells, the large cells were identified as parietal cells, since all the sera containing parietal cell antibodies (PCA) were seen to react with the cytoplasm of these cells, leaving the cytoplasm of the small cells completely unstained. Thirty-one PCA-positive sera and forty-one PCA-negative sera were tested for gastric cell surface-reactive antibodies by an indirect immunofluorescence technique on suspensions of viable gastric cells. All the PCA-containing sera yielded a membrane immunofluorescence confined to the large cells, while none of the PCA-negative sera induced this fluorescent pattern. The surface reaction persisted unmodified when F(ab')2 fragments processed from IgG PCA-positive sera and FITC-conjugated pepsin fragments of rabbit IgG directed against the F(ab')2 fragments of human IgG were employed for the membrane fluorescence studies. The absorption of PCA-positive sera with viable, intact gastric cells led to the disappearance of both the surface immunofluorescence of the viable large cells and the cytoplasmic fluorescence of the rat parietal cells. These results demonstrate that PCA invariably react with an antigen represented on the surface of parietal cells, and that this antigen is immunologically identical to the intracytoplasmic 'microsomal' antigen.