Short-term hypoxic vasodilation in vivo is mediated by bioactive nitric oxide metabolites, rather than free nitric oxide derived from haemoglobin-mediated nitrite reduction.

Local increases in blood flow--'hypoxic vasodilation'--confer cellular protection in the face of reduced oxygen delivery. The physiological relevance of this response is well established, yet ongoing controversy surrounds its underlying mechanisms. We sought to confirm that early hypoxic vasodilation is a nitric oxide (NO)-mediated phenomenon and to study putative pathways for increased levels of NO, namely production from NO synthases, intravascular nitrite reduction, release from preformed stores and reduced deactivation by cytochrome c oxidase. Experiments were performed on spontaneously breathing, anaesthetized, male Wistar rats undergoing short-term systemic hypoxaemia, who received pharmacological inhibitors and activators of the various NO pathways. Arterial blood pressure, cardiac output, tissue oxygen tension and the circulating pool of NO metabolites (oxidation, nitrosation and nitrosylation products) were measured in plasma and erythrocytes. Hypoxaemia caused a rapid and sustained vasodilation, which was only partially reversed by non-selective NO synthase inhibition. This was associated with significantly lower plasma nitrite, and marginally elevated nitrate levels, suggestive of nitrite bioinactivation. Administration of sodium nitrite had little effect in normoxia, but produced significant vasodilation and increased nitrosylation during hypoxaemia that could not be reversed by NO scavenging. Methodological issues prevented assessment of the contribution, if any, of reduced deactivation of NO by cytochrome c oxidase. In conclusion, acute hypoxic vasodilation is an adaptive NO-mediated response conferred through bioactive metabolites rather than free NO from haemoglobin-mediated reduction of nitrite.

Small intestinal mucosa expression of putative chaperone fls485.

BACKGROUND: Maturation of enterocytes along the small intestinal crypt-villus axis is associated with significant changes in gene expression profiles. fls485 coding a putative chaperone protein has been recently suggested as a gene involved in this process. The aim of the present study was to analyze fls485 expression in human small intestinal mucosa. METHODS: fls485 expression in purified normal or intestinal mucosa affected with celiac disease was investigated with a molecular approach including qRT-PCR, Western blotting, and expression strategies. Molecular data were corroborated with several in situ techniques and usage of newly synthesized mouse monoclonal antibodies. RESULTS: fls485 mRNA expression was preferentially found in enterocytes and chromaffine cells of human intestinal mucosa as well as in several cell lines including Rko, Lovo, and CaCo2 cells. Western blot analysis with our new anti-fls485 antibodies revealed at least two fls485 proteins. In a functional CaCo2 model, an increase in fls485 expression was paralleled by cellular maturation stage. Immunohistochemistry demonstrated fls485 as a cytosolic protein with a slightly increasing expression gradient along the crypt-villus axis which was impaired in celiac disease Marsh IIIa-c. CONCLUSIONS: Expression and synthesis of fls485 are found in surface lining epithelia of normal human intestinal mucosa and deriving epithelial cell lines. An interdependence of enterocyte differentiation along the crypt-villus axis and fls485 chaperone activity might be possible.

Dynamic 3-D contrast-enhanced angiography of cerebral tumours and vascular malformations.

We describe the applicability and clinical use of dynamic 3-D contrast-enhanced MR subtraction angiography performed at 3 T with parallel imaging and intelligent k-space readout for imaging both treated and untreated cerebral arteriovenous malformations (AVMs), AV fistulae (AVFs) and brain tumours. An in-plane submillimetre spatial resolution with temporal resolution of one image per 1.3 s was obtained. The spatial resolution was comparable to that of other MRA techniques (i.e. TOF or PC MRA) while the scanning time was markedly reduced and the evaluation of both the arterial and venous vessels was possible with the same imaging sequence. Additional clinical information could be obtained for a variety of CNS disorders. Concerning AVMs, dynamic contrast-enhanced 3-D MRA helped to identify the arterial feeders, the shunting volume, and the location and size of the nidus. However, we found that the most important clinical application was the assessment of shunt occlusion following treatment (i.e. radiosurgery, surgery, or embolization) by determining the absence or presence of early venous filling following injection of contrast agent. Moreover, our MRA technique helped to noninvasively diagnose and classify arteriovenous dural shunts with regard to shunting volume, arterial feeders, and, most importantly, venous drainage pattern. For preoperative imaging of meningeomas, displacement of normal arteries, depiction of tumour feeders and anatomy of the venous system including the tributaries to the large sinuses, their patency, the location of bridging veins, and the extent of tumour vascularization could be assessed. Our findings indicate that dynamic 3-D MRA can help to reduce the scanning time by eliminating additional TOF or PC MRA sequences. With the same imaging sequence, both arterial and venous information can be obtained in a short period of time. In addition, haemodynamic information can be obtained, which may be of importance for a variety of clinical questions. The number of invasive examinations can be reduced during follow-up after treatment of AVF or AVM, and the need to treat dural AV shunts can be assessed noninvasively. In the preoperative investigation of meningeomas, all pertinent information (degree of vascularization, tumour feeders, displacement of arteries, and assessment of large veins) is obtained using a single sequence. We conclude that this MRA sequence may be an alternative to current MRA approaches and will prove an important adjunct for the diagnosis of a variety of neurovascular disorders.