Adenoviral-mediated gene transfer of a constitutively active form of the retinoblastoma gene product attenuates neointimal thickening in experimental vein grafts.
(25/2259)
PURPOSE: Inappropriate or excessive vascular smooth muscle cell proliferation leads to the development of occlusive lesions in up to 50% of vein grafts. The purpose of this study was to test the hypothesis that induced overexpression of a cytostatic nonphosphorylatable form of the retinoblastoma protein (DeltaRb) would attenuate neointimal thickening in experimental vein grafts. METHODS: A replication-deficient adenovirus vector that encoded a nonphosphorylatable, constitutively active form of DeltaRb was constructed (AdDeltaRb) and contained an NH2-terminal epitope tag from the influenza hemagglutinin molecule (HA). Forty-eight male New Zealand white rabbits underwent surgical exposure of the external jugular vein for transfection with either 3 x 10(10) plaque-forming units/mL AdDeltaRb (n = 16), 3 x 10(10) plaque-forming units/mL control adenovirus (AdBglII, n = 15), or vehicle (n = 17) for 10 minutes at 120 mm Hg. After vector exposure, the vein was excised and interposed end-to-end into the carotid circulation. After 5 days, 12 grafts (four from each group) were excised and assayed for genomic DeltaRb DNA with the polymerase chain reaction or for hemagglutinin molecule expression and localization with immunohistochemistry. The remainder of the grafts (n = 36) were perfusion-fixed after 4 weeks, and 5 microm sections prepared for digital planimetric analysis. RESULTS: Polymerase chain reaction results identified the DeltaRb gene only in the grafts that were transfected with AdDeltaRb. Immunohistochemical analysis results revealed transgene expression in most of the endothelial cells and in many of the smooth muscle cells. After 4 weeks, the grafts that were exposed to AdDeltaRb exhibited a 22% reduction in neointimal thickness (vehicle, 77 +/- 7 microm; AdBglII, 75 +/- 5 microm; AdDeltaRb, 60 +/- 5 microm; P =.05), and medial thickness, luminal diameter, and other parameters were unchanged (medial thickness: vehicle, 72 +/- 10 microm; AdBglII, 85 +/- 7 microm; AdDeltaRb, 69 +/- 9 microm; P = NS; luminal diameter: vehicle, 4.5 +/- 0.2 mm; AdBglII, 4.4 +/- 0.2 mm; AdDeltaRb, 4.7 +/- 0.1 mm; P = NS). CONCLUSION: With this delivery system, adenoviral-mediated gene transfer is highly efficient and induced overexpression of DeltaRb leads to a reduction in vein graft neointimal thickening. (+info)
Specialized structure and metabolic activities of high endothelial venules in rat lymphatic tissues.
(26/2259)
Microscopic, histochemical and ultrastructural techniques were used to define characteristics of high endothelial venules (HEV) in rat lymphatic tissues. This endothelium contained acetyl esterase and acid hydrolase activities which were not altered by lymphocyte depletion. No immunoglobulins were detected on luminal surfaces of HEV by fluorescent antibody staining. Only minor structural differences were seen between HEV within lymph nodes and Peyer's patches. At both sites, high endothelial cells were linked together by macular junctional complexes and interlocking basal foot processes. Endothelial cell cytoplasm moulded about surfaces of lymphocytes migrating through the venular wall, and flocculant deposits of basement membrane formed over lymphocytes penetrating the basal lamina. The endothelium was ensheathed by three to five layers of overlapping reticular cell plates and connective tissue. Each plate was linked to the reticular meshwork of the node by collagen bundles and anchoring filaments which inserted into the plate's external limiting membrane. This permitted individual paltes to separate or approximate each other as tissue and intravascular pressure varied, and lymphocytes moved across the sheath by insinuating themselves into gaps between overlapping plates. This composite structure of the HEV wall appeared to facilitate lymphocyte entry into the node and minimized vascular leakge. (+info)
Segmental differentiations of cell junctions in the vascular endothelium. Arteries and veins.
(27/2259)
A systematic survey of endothelial junctions in elastic (aorta) and muscular (mesenteric) arteries and in medium (renal and mesenteric) and large (cava inferior) size veins has been carried out in the rat using freeze-cleaved preparations. The arterial endothelium is provided with a complex of occluding and communicating junctions (gap junctions) comparable to, though less elaborate than, that described in arterioles. The particles of the occluding junctions behave like "single unit" particles and have the tendency to remain on B faces upon membrane cleavage. In the venous endothelium the junctions take the form of long occluding junctions with few associated communicating junctions (maculae communicantes). As in arterial endothelium, the junctional particles appear preferentially on B faces in cleaved preparations. These structures, although continuous over long distances, are interrupted focally by areas in which the junctional elements are similar to those found in venules: the ridges and grooves are short, discontinuous, randomly distributed along the general line of cell contact, and often particle-free. In muscular arteries two unusual types of junctions are encountered. Both are disposed in loops over short distances along the perimeter of the cell. One type appears to be a strectched-out version of the usual combination of occluding and communcating junctions of the arterial endothelium (this type is also occasionally encountered in the venous endothelium). The other type is reminiscent of the septate junctions found in the epithelia of invertebrates but the apparent similarity remains to be checked by further work. (+info)
Elucidating the origins of the vascular system: a fate map of the vascular endothelial and red blood cell lineages in Xenopus laevis.
(28/2259)
Required to supply nutrients and oxygen to the growing embryo, the vascular system is the first functional organ system to develop during vertebrate embryogenesis. Although there has been substantial progress in identifying the genetic cascade regulating vascular development, the initial stages of vasculogenesis, namely, the origin of vascular endothelial cells within the early embryo, remain unclear. To address this issue we constructed a fate map for specific vascular structures, including the aortic arches, endocardium, dorsal aorta, cardinal veins, and lateral abdominal veins, as well as for the red blood cells at the 16-cell stage and the 32-cell stage of Xenopus laevis. Using genetic markers to identify these cell types, our results suggest that vascular endothelial cells can arise from virtually every blastomere of the 16-cell-stage and the 32-cell-stage embryo, with different blastomeres preferentially, though not exclusively, giving rise to specific vascular structures. Similarly, but more surprisingly, every blastomere in the 16-cell-stage embryo and all but those in the most animal tier of the 32-cell-stage embryo serve as progenitors for red blood cells. Taken together, our results suggest that during normal development, both dorsal and ventral blastomeres contribute significantly to the vascular endothelial and red blood cell lineages. (+info)
Physiological reflux and venous diameter change in the proximal lower limb veins during a standardised Valsalva manoeuvre.
(29/2259)
OBJECTIVES: the aim of this study was to provide normal values for venous diameter at rest, and venous diameter and physiologic venous reflux during a standardised Valsalva manoeuvre. The impact of the patient's sex, body mass index (BMI), and family history was investigated. MATERIAL AND METHODS: eighty legs of 40 healthy volunteers were investigated in a supine position. The median age was 28 years (range 20-66 years). The common femoral vein (CFV), the proximal superficial femoral vein (SFV) and the proximal long saphenous vein (LSV) were investigated by duplex sonography. The following parameters were assessed: resting diameter (VDrest) and maximum diameter (VDmax) as well as reflux time (tr) during the Valsalva manoeuvre. The Valsalva manoeuvre was elicited by a forceful expiration into a tube system. The standard values used were a pressure of 30 mmHg, established within 0.5 seconds (s) and maintained over a time period of at least 3 s. RESULTS: mean VDrest and VDmax were 8.3+/-2.2 and 11.1+/-2.8 mm in the CFV, 5.9+/-1. 3 and 7.2+/-1.6 mm in the SFV and 3.5+/-0.9 and 4.3+/-1.4 mm in the LSV. Mean values for tr were 0.61+/-0.63 s in the CFV, 0.25+/-0.26 s in the SFV and 0.28+/-0.40 s in the LSV. A BMI >22.5 kg/m2 was associated with statistically significant larger values for VDrest and tr. If adjusted for BMI, tr in the SFV and the LSV did not differ by sex. For healthy subjects with first-degree relatives suffering from varicose veins (n=19), mean VDrest in the SFV as well as VD in the LSV was significantly larger (p=0.02, 0.05, respectively). Coefficients of variation for repeated measurements (VDrest, VDmax, tr) in the same segment varied between 3.3% and 16. 4% for the three investigated sites. CONCLUSIONS: normal values for VDrest and VDmax as well as reflux time during a standardised Valsalva manouevre were assessed in the proximal lower limb veins. The influences of BMI, sex and family history were investigated. The described standardised Valsalva manoeuvre led to highly reproducible results and can be recommended for further research projects or as a routine procedure for the assessment of venous reflux. (+info)
Plasma endothelin levels in patients with abdominal aortic aneurysms.
(30/2259)
OBJECTIVES: endothelin 1,2 plays a significant role in the process of atherogenesis and vascular wall injury. The aim of this study was to assess whether plasma endothelin 1,2 levels were elevated in patients with large or symptomatic abdominal aortic aneurysms (AAAs). DESIGN: a prospective open study. MATERIALS AND METHODS: plasma endothelin 1,2 levels were measured in 65 consecutive patients with infrarenal aortic aneurysms and compared with the levels in 44 healthy volunteer controls. The data for abdominal aneurysm patients was analysed in four subgroups: (i) small aneurysms (<5 cm), (ii) large aneurysms (>/=5 cm), (iii) asymptomatic aneurysms and (iv) symptomatic aneurysms. Comparisons were made between endothelin 1,2 levels in aneurysm patients and controls and between the different aneurysm subgroups. RESULTS: a highly significant difference (p<0.0001) was found between aneurysm patients and controls. Patients with large aneurysms had significantly higher levels than patients with small aneurysms (p<0.01). There was no statistical difference in endothelin 1,2 levels between symptomatic and asymptomatic patients; however, the highest levels were found in large, symptomatic aneurysms and the lowest in small, asymptomatic aneurysms. CONCLUSIONS: plasma endothelin 1,2 is an endogenous marker of aneurysm diameter. Further studies are required to determine whether it relates to the rate of growth of aneurysms. (+info)
Effects of asymptomatic abdominal aortic aneurysm on the soluble coagulation system, platelet count and platelet activation.
(31/2259)
OBJECTIVES: the aim of the study was to determine the effects of infrarenal asymptomatic abdominal aortic aneurysm (AAA) on platelet count and activation. DESIGN: prospective clinical study in a University Department of Vascular Surgery. PATIENTS: one hundred and five patients with AAA. Thirty-two control patients with symptomatic carotid artery stenoses. METHODS: platelet count (PC), plasma glycocalicin levels, prothrombin ratio (PTR), activated partial thromboplastin time (APPT), fibrinogen and D-dimer were measured in 23 patients with AAA and 16 control patients with symptomatic carotid artery stenoses. PC alone was measured in a further 84 patients with AAA and 16 with carotid artery stenoses. RESULTS: PC was below the normal range in 8/105 patients and mean PC (215x10(9)/l, S.D. 47.5) was significantly lower than that of a control population (242x10(9)/l, S.D. 16.8) and patients with carotid disease (269x10(9)/l, S.D. 57). Glycocalicin level was above the normal range in 7/23 patients and the median level (28 fg/plt) was significantly higher than that of a normal population (21.6 fg/plt) and patients with carotid disease (12.3 fg/plt). Fibrinogen levels, PTR and APPT were all within the normal range. One patient had a minimally elevated level of D-dimer. CONCLUSIONS: the combination of low PC and high glycocalicin levels suggests that there is increased platelet destruction, most likely due to activation within the aneurysm sac. (+info)
rhomboid and Star interact synergistically to promote EGFR/MAPK signaling during Drosophila wing vein development.
(32/2259)
Genes of the ventrolateral group in Drosophila are dedicated to developmental regulation of Egfr signaling in multiple processes including wing vein development. Among these genes, Egfr encodes the Drosophila EGF-Receptor, spitz (spi) and vein (vn) encode EGF-related ligands, and rhomboid (rho) and Star (S) encode membrane proteins. In this study, we show that rho-mediated hyperactivation of the EGFR/MAPK pathway is required for vein formation throughout late larval and early pupal development. Consistent with this observation, rho activity is necessary and sufficient to activate MAPK in vein primordium during late larval and early pupal stages. Epistasis studies using a dominant negative version of Egfr and a ligand-independent activated form of Egfr suggest that rho acts upstream of the receptor. We show that rho and S function in a common aspect of vein development since loss-of-function clones of rho or S result in nearly identical non-autonomous loss-of-vein phenotypes. Furthermore, mis-expression of rho and S in wild-type and mutant backgrounds reveals that these genes function in a synergistic and co-dependent manner. In contrast, spi does not play an essential role in the wing. These data indicate that rho and S act in concert, but independently of spi, to promote vein development through the EGFR/MAPK signaling pathway. (+info)