Lack of NO Formation Is Involved in the Vasodilative Response to Contrast Media.

Intravascular injection of angiographic contrast media results in peripheral vasodilation and hypotension. The mechanisms underlying these hemodynamic changes are not entirely clear. We hypothesized that increased formation of nitric oxide (NO) could be involved in the vasodilatory response to contrast media. To address this assumption we have investigated whether N(G)-monomethyl-L-arginine (L-NMMA, 200 mg/kg) and N(G)-nitro-L-arginine methyl ester (L-NAME, 50 mg/kg), two specific NO formation inhibitors, can abolish the hypotensive response to intravascular injection of isopaque amin (1 g/kg), a contrast medium, as well as bradykinin (10 µg/kg), a NO-dependent vasodilator, in anaesthetized normotensive rats. In rats before pretreatment with L-NMMA and L-NAME, the absolute values of the average fall in mean arterial pressure (MAP) induced by intravascular injection of isopaque amin and bradykinin were 21.3 +/- 2.1 and 37.2 +/- 4.4 mmHg, respectively. Pretreatment with L-NMMA and L-NAME failed to affect the hypotensive response to isopaque amin; by administering isopaque amin in rats pretreated with L-NMMA and L-NAME the absolute values of the average fall in MAP were 25.6 +/- 4.9 and 23.4 +/- 3.9 mmHg, respectively, similar to the average fall in MAP before treatment with NO formation inhibitors. In contrast, the hypotensive response to bradykinin was significantly inhibited; by administering bradykinin in rats pretreated by L-NMMA and L-NAME, the absolute values of the average fall in MAP were 10.2 +/- 2.8 and 7.2 +/- 2.2 mmHg, respectively, much less than the average fall in MAP before treatment with NO formation inhibitors. We conclude that intravascular injection of isopaque amin causes reduction in systemic arterial pressure. However, this vasodilative effect seems unrelated majorly to augmented endothelium-derived NO formation.

[Bifurcation stenting of unprotected common trunk: a case report and review of the literature]. / Stenting di biforcazione del TC non protetto: caso clinico e riflessioni sulla letteratura.

Left main disease is the most severe form of atherosclerotic heart disease, with severe prognostic implications in the short-medium term. The traditional therapeutic approach has been surgical, with placement of bypass grafts both on the LAD and the circumflex artery. Published experience with the percutaneous approach to left main disease has been disappointing because of acute procedural problems and poor long-term outcome. On the other hand, a review of the literature shows a strong negative selection of patients offered PTCA of left main-stem lesions: most published series are composed of extremely high-risk patients, often in cardiogenic shock or with severe extracardiac multisystem disease, with a prohibitive surgical risk and an inherently poor acute and mid-term prognosis. We describe such a patient, a 77-year-old woman with end-stage renal disease on hemodialysis, who developed unstable angina due to distal critical left main disease, with involvement of the origin of both the LAD and the circumflex branch. Angina did not stabilize with medical therapy; the patient was denied surgery because of a prohibitively high surgical risk. A bifurcation stenting procedure was performed with no acute complications, a satisfactory one-month angiographic follow-up and no recurrence of angina until the death of the patient 4 months after the procedure for extracardiac reasons. As indicated by a recent paper by M. Leon, we likewise suggest that left main disease (especially in its simpler proximal variants) may actually be a good target for state-of-the-art transcatheter interventions, including primary stenting, under close angiographic follow-up and careful positive (instead of negative) selection of patients.

Molecular and cellular aspects of induced thymus development in recombinase-deficient mice.

Thymus development and microenvironment organization require stage- and site-specific cross-talk between thymocyte and stroma. In this study we have used recombinase-activating gene-deficient (RAG-2(-/-)) mice to analyze regulated gene expression both in thymocytes and stromal cells following injection of anti-CD3 monoclonal antibodies as inducer of thymus development. We show that IFN-gamma, TNF-alpha and lymphotactin are transcriptionally regulated in thymocytes, whereas cytoskeletal keratin 14, IL-1alpha and TNF-alpha are regulated in the stroma, quantitatively reproducing the variations associated with beta selection of thymocytes. In addition, RAG-2(-/-) thymus development is associated with entry of epithelial cells into the cell cycle. The histochemical evidence that expanded RAG-2(-/-) thymus becomes undistinguishable from wild-type cortex further suggests that cross-talk phenomena occurring during beta selection of thymocyte are reproduced in this system.

GKLF in thymus epithelium as a developmentally regulated element of thymocyte-stroma cross-talk.

Gut-enriched Krüppel-like factor (GKLF) is a transcriptional regulator expressed in differentiated epithelia. We identified GKLF transcript as a regulated element in thymic epithelium of recombinase-deficient mice during thymus development induced by anti-CD3 antibody injection. This treatment recapitulates the organogenetic process depending on productive rearrangement of T cell receptor (TCR) beta gene with thymocytes expansion and acquisition of the CD4+8+ double positive phenotype. In wildtype mice, GKLF is expressed very early in embryogenesis and becomes intensely up-regulated in thymus epithelium at day 18 of gestation when TCR beta expressing cells have selectively expanded and express both CD4 and CD8. The results presented here suggest that thymocytes may regulate GKLF transcriptionally in the cortical epithelium at the developmental check-point controlled by TCR beta gene rearrangement. Furthermore, GKLF expression in hematopoietic stroma might suggest the thus far uncharacterised participation of this factor in hematopoiesis.

Surface expression and functional competence of CD3-independent TCR zeta-chains in immature thymocytes.

In recombinase-deficient (RAG-2-/-) mice, double-negative thymocytes can be stimulated to proliferate and differentiate by anti-CD3 Abs. CD3 molecules are expressed on the surface of these cells in association with calnexin. In this study, we show that zeta-chains can be recovered as phosphorylated proteins in association with phosphorylated ZAP-70 from anti-CD3-stimulated RAG-2-/- thymocytes, even though they are not demonstrably associated with the CD3/calnexin complex. The lack of a physical association of zeta dimers with the CD3 complex in RAG-2-/- thymocytes and also in a pre-TCR-expressing cell line, as well as the efficient association of zeta dimers with ZAP-70 in the RAG-2-/- thymocytes, suggest that these zeta-chain dimers could contribute to pre-TCR signaling. This idea is supported by the finding that in RAG-2-/- zeta-deficient thymocytes, ZAP-70 and p120cbl were only weakly phosphorylated.

Epithelial V-like antigen (EVA), a novel member of the immunoglobulin superfamily, expressed in embryonic epithelia with a potential role as homotypic adhesion molecule in thymus histogenesis.

Thymus development depends on a complex series of interactions between thymocytes and the stromal component of the organ. To identify regulated genes during this codependent developmental relationship, we have applied an RNA fingerprinting technique to the analysis of thymus expansion and maturation induced in recombinase-deficient mice injected with anti-CD3 antibodies. This approach led us to the identification of a gene encoding a new member of the immunoglobulin superfamily, named epithelial V-like antigen (EVA), which is expressed in thymus epithelium and strongly downregulated by thymocyte developmental progression. This gene is expressed in the thymus and in several epithelial structures early in embryogenesis. EVA is highly homologous to the myelin protein zero and, in thymus-derived epithelial cell lines, is poorly soluble in nonionic detergents, strongly suggesting an association to the cytoskeleton. Its capacity to mediate cell adhesion through a homophilic interaction and its selective regulation by T cell maturation might imply the participation of EVA in the earliest phases of thymus organogenesis.