Prothrombin antigen levels in symptomatic and asymptomatic carriers of the 20210A prothrombin variant

A recently discovered variant in the prothrombin gene (20210A) has been found in approximately 5–10% of patients with venous thromboembolism. It has been shown that patients with this variant present with high levels of prothrombin in plasma and this is maintained to be the most likely mechanism by which the risk of thrombosis is increased. We have evaluated prothrombin antigen levels in 50 carriers of the 20210A allele and compared with non-carriers. 327 subjects were subdivided according to deficiency status and previous thrombosis. 30 symptomatic and 20 asymptomatic carriers had increased mean prothrombin levels as compared to symptomatic ( n  = 178) or asymptomatic ( n  = 99) non-carriers. The percentage of subjects with prothrombin levels above cut-off values of 1.15 u/ml or 1.30 u/ml was significantly higher in carriers of the prothrombin variant as compared to non-carriers, regardless of a previous thrombosis. However, among non-carriers the percentage of those with prothrombin levels above cut-off values was significantly higher in the group of symptomatic as compared to asymptomatic individuals. In conclusion, increased prothrombin antigen levels, as detected by a specific ELISA, were found among 50 symptomatic and asymptomatic carriers of the 20210A prothrombin variant as well as among a large group of symptomatic non-carriers. The data are in agreement with those found by using functional tests for the determination of prothrombin levels in these patients.     

Type 3 iodothyronine deiodinase is highly expressed in the human uteroplacental unit and in fetal epithelium

Type 3 iodothyronine deiodinase (D3) is the major physiologic inactivator of thyroid hormone. This selenoenzyme, previously identified in human placenta and brain, catalyzes the inner-ring deiodination of T(4) to reverse T(3) and T(3) to 3, 3'-diiodothyronine, both of which are biologically inactive. We analyzed D3 expression in several human adult and fetal tissues by immunohistochemistry and correlated the results with D3 activity assays where possible. High D3 expression was present in the placental syncytiotrophoblasts and cytotrophoblasts, endothelium of fetal vessels, and maternal decidua. D3 was also present at other sites of maternal-fetal interface, including the umbilical arteries and vein and the fetal respiratory, digestive, and urinary tract epithelium. Surprisingly, D3 was also present in the endometrial glands of nonpregnant human uteri, and endometrial activity approximated that of term placenta. The presence of D3 at maternal-fetal interfaces is consistent with its role in modulating the thyroid status of the human fetus and its expression in endometrium suggests that local regulation of thyroid status is important in implantation.     

Myocardial dysfunction and abnormal left ventricular exercise response in autonomic diabetic patients

In diabetic patients, the pathophysiologic mechanisms of exercise-induced left ventricular (LV) dysfunction remain controversial. In this study, the role of myocardial contractility recruitment in determining an abnormal LV response to isometric or dynamic exercise has been investigated in 14 diabetic patients with autonomic dysfunction. Ischemic heat disease was excluded by the absence of LV wall motion abnormalities induced by isotonic and isometric exercise and by coronary angiography. Left ventricular and myocardial function were studied at rest, and during isometric and isotonic exercise, by two-dimensional echocardiography; moreover, recruitment of an inotropic reserve was assessed by postextra-systolic potentiation at rest and at peak handgrip. An abnormal response of LV ejection fraction to isometric (9/14) or to dynamic (8/14) exercise was frequent in study patients. In these patients, baseline myocardial contractility was normal, and the significant increase in ejection fraction by postextrasystolic potentiation indicated a normal contractile reserve (65 ± 7% vs. 74 ± 6%, p=0.001). Nevertheless, the downward displacement of LV ejection fraction-systolic wall stress relationships during exercise suggests an inadequate increase in myocardial contractility. However, the abnormal ejection fraction at peak handgrip was completely reversed by postextrasystolic potentiation (67 ± 6% vs. 58.1 ± 10%, p=0.008), a potent inotropic stimulation independent of the integrity of adrenergic cardiac receptors. A defective inotropic recruitment, despite the presence of a normal LV contractile reserve, plays an important role in deexercise LV dysfunction in diabetic patients with autonomic neuropathy.