Jean Ruf

Syncope due to idiopathic paroxysmal atrioventricular block : long-term follow-up of a distinct form of atrioventricular block.

OBJECTIVES We present data on patients with syncope due to paroxysmal atrioventricular (AV) block unexplainable in terms of currently known mechanisms. BACKGROUND Paroxysmal AV block is known to be due to intrinsic AV conduction disease or to heightened vagal tone. METHODS We evaluated 18 patients presenting with unexplained syncope who had: 1) normal baseline standard electrocardiogram (ECG); 2) absence of structural heart disease; and 3) documentation, by means of prolonged ECG monitoring at the time of syncopal relapse, of paroxysmal third-degree AV block with abrupt onset and absence of other rhythm disturbances before or during the block. RESULTS The study group consisted of 9 men and 9 women, mean age 55 ± 19 years, who had recurrent unexplained syncope for 8 ± 7 years and were subsequently followed up for as long as 14 years (4 ± 4 years on average). The patients had no structural heart disease, standard ECG was normal, and electrophysiological study was negative. In all patients, prolonged ECG monitoring documented paroxysmal complete AV block with 1 or multiple consecutive pauses (mean longest pause: 9 ± 7 s at the time of syncope); AV block occurred without P-P cycle lengthening or PR interval prolongation. During the observation time, no patient had permanent AV block; on permanent cardiac pacing, no patient had further syncopal recurrences. CONCLUSIONS Common clinical and electrophysiological features define a distinct form of syncope due to idiopathic paroxysmal AV block characterized by a long history of recurrent syncope, absence of progression to persistent forms of AV block, and efficacy of cardiac pacing therapy.

Association of duoxes with thyroid peroxidase and its regulation in thyrocytes.

CONTEXT Thyroid hormone synthesis requires H(2)O(2) produced by dual oxidases (Duoxes) and thyroperoxidase (TPO). Defects in this system lead to congenital hypothyroidism. H(2)O(2) damage to the thyrocytes may be a cause of cancer. OBJECTIVE The objective of the study was to investigate whether Duox and TPO, the H(2)O(2) producer and consumer, might constitute a complex in the plasma membrane of human thyroid cells, thus maximizing efficiency and minimizing leakage and damage. DESIGN The interaction between Duox and TPO was studied by coimmunoprecipitation and Western blotting of plasma membranes from incubated follicles prepared from freshly resected human thyroid tissue from patients undergoing thyroidectomy, and COS-7 cells transiently transfected with the entire Duoxes or truncated [amino (NH2) or carboxyl (COOH) terminal]. RESULTS The following results were reached: 1) Duox and TPO from membranes are coprecipitated, 2) this association is up-regulated through the Gq-phospholipase C-Ca(2+)-protein kinase C pathway and down-regulated through the Gs-cAMP-protein kinase A pathway, 3) H(2)O(2) increases the association of Duox1 and Duox2 to TPO in cells and in membranes, and 4) truncated NH(2)- or COOH-terminal Duox1 and Duox2 proteins show different binding abilities with TPO. CONCLUSION Coimmunoprecipitations show that Duox and TPO locate closely in the plasma membranes of human thyrocytes, and this association can be modulated by H(2)O(2), optimizing working efficiency and minimizing H(2)O(2) spillage. This association could represent one part of a postulated pluriprotein complex involved in iodination. This suggests that defects in this association could impair thyroid hormone synthesis and lead to thyroid insufficiency and cell damage.

Effects of PP-56 and Vitamin E on Platelet Hyperaggregability, Fatty Acid Abnormalities, and Clinical Manifestations in Streptozocin-Induced Diabetic Rats

The effects of vitamin E and D-myo-inositol 1,2,6-trisphosphate (PP-56) were investigated in long-term studies in streptozocin-induced diabetic rats fed a purified diet with 33% lipids and a polyunsaturated- to -saturated fatty acid ratio of 1. A supplement of vitamin E decreased plasma triglycerides, platelet lipid biosynthesis, some of the ∆6- and ∆5-desaturase abnormalities, and urine ketone bodies but did not affect the response of platelets to aggregation. PP-56 completely normalized the platelet reactivity to ADP and thrombin. This was accompanied by normalization of platelet lipid biosynthesis and diabetes-induced abnormalities in ∆6- and ∆5-desaturases. PP-56 treatment also reduced the mortality rate and to a certain extent urinary ketone bodies. The protective effect of PP-56 on platelet aggregation and mortality rate were dose related. PP-56, a molecule derived from phytic acid, seems to exert potent protective effects on some of the manifestations associated with diabetes in rats.

Immunohistochemical study of thyroglobulin in thyroid carcinomas with monoclonal antibodies

The effectiveness of an immunoperoxidase technique using four monoclonal antibodies (mAb) is compared to a technique using one polyclonal antibody (pAb) to detect human thyroglobulin (Tg) in paraffin sections of 55 thyroid carcinomas. With the pAb, a positive reaction was found in 82% of the cases. With the four mAb, the presence of Tg was demonstrated in 96.5% of the cases. The mAb gave better results than the pAb on poorly differentiated and anaplastic thyroid carcinomas. Many of the thyroid carcinomas in this study, especially the poorly differentiated and anaplastic type, failed to react with all four mAb to Tg. These results confirm the notion of the heterogeneity of Tg in thyroid carcinomas and indicate that a battery of carefully selected mAb can be successfully used for routine histopathologic detection of Tg in these tumors.

Prevalence of Autoantibodies to Thyroperoxidase in Patients with Various Thyroid and Autoimmune Diseases

An original radioimmunoassay for quantitation of circulating autoantibodies (aAb) to thyroperoxidase (TPO) proved to be well suited for large scale routine testing. The present study was aimed to assess the prevalence of aAb to TPO in patients with various thyroid and autoimmune disease and, for comparison, in women referred for reproductive disorders and indication of in vitro fertilization. Anti-TPO aAb were measured in sera from 32 healthy subjects and 262 patients thoroughly investigated for thyroid dysfunction. As determined in healthy subjects, the normal level of aAb to TPO in serum ranged from 0.30 to 3.07 mg/l (of affinity-purified) anti-TPO aAb. Anti-TPO and anti-MIC aAb levels were both normal in 115 patients and correlated well (r = 0.835, P less than 0.001) in the remaining 147 patients. Coexistence of normal level of anti-TPO aAb and abnormal level of anti-MIC aAb was found in 4 patients and ascribed to a lack of specificity or sensitivity of the test for anti-MIC aAb. Coexistence of abnormal level of anti-TPO aAb and normal level of anti-MIC aAb was found in 67 patients of whom 62 presented only slightly elevated (3.1 to 10.0 mg/l) anti-TPO aAb concentration; the 5 remaining patients, all with overt thyroid autoimmune disease, showed anti-TPO levels between 10.7 to 100.7 mg/l.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine plasma level and A2A adenosine receptor expression: correlation with laboratory tests in patients with neurally mediated syncope

Objectives The purpose of this study was to investigate the hypothesis that responses to the ATP test and head-up tilt test (HUT) may be correlated with different purinergic profiles. Design and setting The ATP and HUT identify distinct subsets of patients with neurally mediated syncope (NMS). Adenosine and its A2A receptors (A2AR) may be implicated in the pathophysiology of NMS in patients with positive HUT. Nothing is known about the purinergic profile of patients with positive ATP. Patients and measures This prospective study includes a consecutive series of patients with suspected NMS. All patients underwent both HUT and ATP. Before testing, samples were collected for measurement of baseline adenosine plasma level (APL) and expression. Results A total of 46 patients (25 men and 21 women) with a mean age of 57±18 years were enrolled. The HUT test was positive in 27 patients and the ATP test in 20. Both tests were positive in 9 and negative in 8. High APL was associated with high probability of positive HUT while low APL was associated with high probability of positive ATP. Expression of A2AR was lower in patients with positive ATP than in those with positive HUT. Conclusion These findings indicate that patients with NMS present different purinergic profiles and that responses to HUT and ATP are correlated with these profiles.

Cytotoxic assay of circulating thyroid peroxidase antibodies.

This study describes an assay for the detection of cytotoxicity for thyroid cells in serum of patients with autoimmune thyroiditis. Quantitative measurement may be performed by DNA or [3H] leucine incorporation determinations. The cytotoxic effect is localized in the gamma-globulin fraction, and is complement-mediated. It is thyroid specific i.e. it is not observed with fibroblasts and patients with other autoimmune diseases (patients with lupus erythematosis or glomerulonephritis) do not have cytotoxic antibodies directed against thyroid cells. The thyroid cytotoxicity is related to the presence of antimicrosomal antibodies and the effect of circulating antibodies is inhibited by human thyroid peroxidase. These results strengthen the possible implication of circulating antithyroid peroxidase antibodies in thyroid damage observed in autoimmune thyroiditis.

Role of caveolin-1 in thyroid phenotype, cell homeostasis, and hormone synthesis: in vivo study of caveolin-1 knockout mice.

In human thyroid, caveolin-1 is localized at the apex of thyrocytes, but its role there remains unknown. Using immunohistochemistry, (127)I imaging, transmission electron microscopy, immunogold electron microscopy, and quantification of H(2)O(2), we found that in caveolin-1 knockout mice thyroid cell homeostasis was disrupted, with evidence of oxidative stress, cell damage, and apoptosis. An even more striking phenotype was the absence of thyroglobulin and iodine in one-half of the follicular lumina and their presence in the cytosol, suggesting that the iodide organification and binding to thyroglobulin were intracellular rather than at the apical membrane/extracellular colloid interface. The latter abnormality may be secondary to the observed mislocalization of the thyroid hormone synthesis machinery (dual oxidases, thyroperoxidase) in the cytosol. Nevertheless, the overall uptake of radioiodide, its organification, and secretion as thyroid hormones were comparable to those of wild-type mice, suggesting adequate compensation by the normal TSH retrocontrol. Accordingly, the levels of free thyroxine and TSH were normal. Only the levels of free triiodothyronine showed a slight decrease in caveolin-1 knockout mice. However, when TSH levels were increased through low-iodine chow and sodium perchlorate, the induced goiter was more prominent in caveolin-1 knockout mice. We conclude that caveolin-1 plays a role in proper thyroid hormone synthesis as well as in cell number homeostasis. Our study demonstrates for the first time a physiological function of caveolin-1 in the thyroid gland. Because the expression and subcellular localization of caveolin-1 were similar between normal human and murine thyroids, our findings in caveolin-1 knockout mice may have direct relevance to the human counterpart.

Human Autoantibodies Modulate the T Cell Epitope Repertoire but Fail to Unmask a Pathogenic Cryptic Epitope

Abs can tune the responses of Ag-specific T cells by influencing the nature of the epitope repertoire displayed by APCs. We explored the interaction between human self-reactive T cells and human monoclonal autoantibodies from combinatorial Ig-gene libraries derived from autoimmune thyroiditis patients and specific for the main autoantigen thyroid peroxidase (TPO). All human mAbs extensively influenced the T cell epitope repertoire recognized by different TPO-specific T cell clones. The action of the human mAbs was complex, because sometimes the same Ab suppressed or enhanced the epitopes recognized by the 10 different TPO-specific T cell clones. The human mAbs could modulate the epitope repertoire when TPO was added exogenously and when expressed constitutively on the surface of APCs. However, they could not unmask an immunodominant cryptic TPO epitope. In this study, we show that human autoantibodies influence the activity of self-reactive T cells and prove their relevance in concealing or exposing epitopes recognized by self-reactive T cells. However, our results further stress the biological significance of the immunodominant cryptic epitope we have defined and its potential importance in the evolution of autoimmunity.

Monoclonal antibody–assisted stimulation of adenosine A2A receptors induces simultaneous downregulation of CXCR4 and CCR5 on CD4+ T-cells

Immunocompetent cells express various G-protein-coupled receptors that transduce extracellular signals across the plasma membrane. Among them, CXCR4 and CCR5 chemokines receptors and adenosine A(2A) receptors (A(2A)R) are involved in inflammatory processes. Considering that A(2A)R activation may have incidence on CXCR4 and CCR5 protein expression through heterologous desensitization process, we tested Adonis, an agonist-like monoclonal antibody to A(2A)R on CD4+ CEM T-cells. We found that Adonis inhibited the CEM cell growth, upregulated A(2A)R and downregulated CXCR4 and CCR5 without modifying the CD4 expression. By reducing the expression of CXCR4 and CCR5 chemokines receptors utilized as entry co-receptors by HIV-1 during viral infection of CD4 expressing cells, Adonis stimulation of A(2A)R appears as a valuable means to treat infected cells.