Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “VESSELS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 847 records · Page 47Linked to original sources
PubMed2005

The effect of longitudinal pre-stretch and radial constraint on the stress distribution in the vessel wall: a new hypothesis.

It is well known that blood vessels shorten axially when excised. This is due to the perivascular tethering constraint by side branches and the existence of pre-stretch of blood vessels at the in situ state. Furthermore, vessels are radially constrained to various extents by the surrounding tissues at physiological loading. Our hypothesis is that the axial pre-stretch and radial constraint by the surrounding tissue homogenizes the stress and strain distributions in the vessel wall. A finite element analysis of porcine coronary artery and rabbit thoracic aorta based on measured material properties, geometry, residual strain and physiological loading is used to compute the intramural stresses and strains. We systematically examined the effect of pre-stretch and external radial constraint in both vessels. Our results show that both stretching in the axial direction and compression in the radial direction lead to a more homogeneous strain and stress state in the blood vessel wall. A "uniform biaxial strain" hypothesis is proposed for the blood vessel wall and the ramifications are discussed.

Animals↗
PubMed1982

Histologic and fine-structural anatomy of the adrenorenal portal vessels in the dog.

Reflex vasoconstriction that occurs in the kidney of the dog can be the result of activation of catecholamine flow reaching the kidney directly from the adrenal medulla via adrenorenal portal vessels. This study was undertaken to learn more about the histologic and fine-structural anatomy of these unusual vessels. We found that they are thin-walled vessels (200-500 micrometers) which are accompanied by many capillaries. These portal vessels have distinctive valves and have sparse, longitudinally arranged musculature which is denser at the base of the valves. The valves in the portal vessels are arranged to permit flow in the direction from the adrenal gland toward the kidney. Smooth muscle at the base of the valve is in close proximity to non-myelinated nerve fibers, suggesting that the opening of these valves may in part be neurally mediated. These unique anatomical features distinguish the adrenorenal portal vessels from other blood vessels and likely have functional importance in control of the adrenorenal circulation.

Adrenal Medulla↗
PubMed2003

Influence of wavelength on response to laser photothermolysis of blood vessels: implications for port wine stain laser therapy.

BACKGROUND AND OBJECTIVE: Treatment of port wine stains (PWS) by photothermolysis can be improved by optimizing laser parameters. We have studied the all-important role of wavelength (lambda) by performing pulsed laser photothermolysis in the vasculature of the chick chorioallantoic membrane (CAM) assay. STUDY DESIGN/MATERIALS AND METHODS: The CAM contains an extensive microvascular network ranging from capillaries with diameter D < 20 microm to blood vessels of D approximately 120 microm. The CAM assay enables observation and real-time video documentation of blood flow in pre-capillary arterioles (A) and post-capillary venules (V). The ScleroPlus trade mark laser (Candela Corp., Wayland, MA) has a smooth output over its fixed 1.5 ms pulse duration and allows the operator to vary several treatment parameters such as wavelength, spot size, and energy. Blood vessels in the CAM were irradiated at two clinically relevant wavelengths, lambda = 587 or 597 nm, constant spot size (7 mm), and at different exposures (E = 5-12 J/cm(2)). Threshold exposure (E(th)) (at which non-reversible damage occurred) were 5 J/cm(2) at 587 nm and 8 J/cm(2) at 597 nm. Mathematical modeling was developed to interpret initial (within 30 seconds) injury of arterioles and venules at both wavelengths as a function of D when varying E. RESULTS: Vessel injury was graded off-line from videotapes. For all combinations of lambda and E, measurable injury was evident within 30 seconds of irradiation and maximal damage was reached in less than 10 minutes. Vessel damage was found to depend strongly on lambda. Damage decreased with increasing vessel size. For all D, damage of arterioles was greater than for corresponding venules. CONCLUSIONS: Selection of the correct wavelength is crucial for successful laser therapy of hypervascular lesions and, ideally, should be based on knowledge of vessel diameters for a specific PWS lesion and of optical penetration depths in blood. As a general statement, smaller blood vessels (D = 10-60 microm) should be treated using shorter wavelengths such as 585 nm. To ensure deposition of sufficient laser energy, irradiation at 585 nm, characterized by lower optical penetration depth in blood, may be preferable for PWS therapy.

Animals↗
PubMed2004

Magnetic resonance angiography of collateral vessels in a murine femoral artery ligation model.

The in vivo detection of growing collateral vessels following arterial occlusion is difficult in small animals. We have addressed the feasibility of performing high resolution time-of-flight angiograms to monitor the growth of collateral vessels after femoral artery occlusion in mice. We will also present a low-pass quadrature birdcage coil construction with a sufficient signal-to-noise ratio to produce high resolution. After a 4-month recovery period a C57BL/6 mouse with a surgical occlusion of the right femoral artery was used to assess the image quality and time requirements to produce magnetic resonance angiograms sufficient to assess collateral artery development using a two-dimensional gradient echo sequence. At a resolution of 100 x 100 x 100 microm and a matrix size of 256 x 128 x 256 for a 2.56 cm isometric volume, three scans were performed with one, two and four repetitions resulting in signal-to-noise ratios for the femoral artery proximal to the ligation site of 58, 126 and 194, respectively. Five C57BL/6 mice were additionally measured 4 weeks after occlusion using two repetitions and the visual collateral vessels were assessed for number and location: 2.0 +/- 1.2 in quadriceps muscle, 0.6 +/- 0.5 in adductor (deep adductor vessel), 0.0 +/- 0.0 in adductor (surface adductor vessels). The results showed a significant difference, two-sided t-test, p < 0.05, in number of vessels in all the locations. We have shown that this method can be utilized to elucidate the contribution of collateral vessels to arterial flow.

Animals↗
PubMed1987

Intraventricular blood vessels associated with the deep pineal gland of the Mongolian gerbil, Meriones unguiculatus.

Intraventricular blood vessels and choroidal-like cells were studied using scanning electron microscopy and correlative light microscopy. The intraventricular blood vessels were covered on their ependymal surface with a layer of cells essentially identical to the ependyma of the choroid plexus in the gerbil. Similar choroidal-like cells were seen either singly or in clusters associated with the cerebrospinal fluid-contacting pinealocytes of the suprapineal recess. Processes of the cerebrospinal fluid-contacting pinealocytes were seen extending to and making contact with the choroidal-like cells. The intraventricular blood vessels appeared to be derived from the choroid plexus, and typically took one of three courses in and around the surface of the deep pineal: (1) the vessels or their equivalent were located in the suprapineal recess with no indication of penetration into the substance of the deep pineal; (2) the vessels coursed from the suprapineal recess around the anterior surface of the habenular commissure to enter the ventral surface of the deep pineal; or (3) the vessels entered the parenchyma of the deep pineal from its dorsal surface and could be seen coursing through the substance of the gland. The close association between the choroidal-like cells and the intraventricular blood vessels with the deep pineal gland add morphological support for the possibility of interaction between the cerebrospinal fluid, or perhaps the choroid plexus, and the deep pineal gland.

Animals↗
PubMed1976

Ultrastructural changes in blood vessels of peripheral nerves in leprosy neuropathy. I. Tuberculoid and borderline-tuberculoid leprosy patients.

Radial or superficial peroneal nerve biopsies of 6 patients with tuberculoid or borderline-tuberculoid leprosy and 6 control nerve biopsies were examined by electron microscopy. Endoneurial blood vessels showed histopathology in all the leprosy patients. Changes, in particular, involved the basement membrane in postcapillary venules and venules. Multilayered parellel basement membranes, with collagen and ground substance, formed a thick coat ("hyaline zone") around the vessels. It is suggested that the zone inhibits passage of nutrients and metabolites and, thus, contributes to or is the main cause of the local destruction of (unmyelinated) nerve fibres and the lack of nerve fibre regeneration observed in this type of leprosy. The perivascular zone, presumably, is produced by pericytes in response to defects in the "blood-nerve barrier" of endoneurial vessels. In granulomata of leprosy skin lesions, a perivascular zone was not present. The endothelium of endoneurial vessels, in affected nerves, generally was normal. Occasionally, however, gaps and fenestrations were seen and there were histological indications that leakage of blood plasma had occurred through the gaps and through the basement membrane of the endothelium. Occlusion of endoneurial vessels was found only in the oldest patient and the degeneration of nerve fibres generally observed thus is considered not to be caused by ischaemia. Histopathology in epi-and perineurial vessels was definitely less pronounced than in endoneurial vessels.

Adolescent↗
PubMed1987

Ultrastructure of sheathed vessels in the retina from patients with various diseases.

Retinal sheathed vessels from five patients with various vascular diseases were examined by light and electron microscopy. All of these vessels were characterized by a marked increase and disarrangement of collagen fibrils in the media and adventitia. Cytoplasmic processes of glial cells had invaded the adventitia in sheathed vessels and even in unsheathed ones. Thickening and multilamination of the basal laminae were observed in both the sheathed and unsheathed vessels. The lumens of most sheathed vessels were still patent, and the blood cells and endothelial cells of these vessels appeared to be intact. We found no essential differences in the ultrastructure of these vessels in the five patients with various vascular diseases. It is concluded that the increase and disarrangement of collagen fibrils may be mainly related to the ophthalmoscopic appearance of the sheathing and that other factors seem to be of lesser significance.

Adult↗
PubMed1994

Concomitant immunocytochemical study of macrophage cells and blood vessels in disc herniation tissue.

Twenty disc herniations (DH) were studied immunocytochemically for macrophages and blood vessels. Serial thin frozen sections were immunostained with an antibody specific for tissue macrophages (monoclonal antibody to CD68 antigen) and the endothelium of blood vessels (polyclonal antibody to von Willebrand factor). With this method, blood vessels, often abundant, were observed in as many as 16/20 (80%) of the DH studied, 12 disc extrusions and 8 sequestrated discs, whereas abundant macrophages were noted in 11/20 (55%) of the DH. Macrophages were present only in areas with blood vessels and had presumably infiltrated the tissue from them. As has been noted previously, some blood vessels are apparently newly formed as a result of tissue injury, whereas others were present in the disc prior to herniation. This is suggested by the lack of a clear correlation between the presence or absence of blood vessels and the preoperative duration of radicular pain. In areas of the DH where cartilage fragments occurred, both macrophages and blood vessels were particularly abundant.

Adult↗
PubMed1977

Electron-microscopic analysis of iris vessels in two cases of uveitis.

Electron-microscopic analysis of iris biopsy material was carried out paying particular attention to vessels and infiltrating cells. Characteristic changes of vessels and cells were found in two cases. One showed abundant lymphodiapedesis, perivascular infiltration, and vessels appearing morphologically normal. The other showed diffuse infiltration of cells and numerous fenestrated newly formed vessels. In the latter, three different types of opening in the endothelium were observed: (1) separation of intercellular junctions; (2) small pores or defects in the endothelium, and (3) large holes or defects in the endothelium. Cell leakage from normal and newly formed vessels was considered. We concluded that lymphocytes may migrate through the cytoplasm within membrane-bounded vesicles in normal vessels, whereas in newly formed fenestrated vessels cells, including small lymphocytes, may pass through three different types of opening in the endothelium.

Aged↗
PubMedDate not supplied

Major vessel resection during limb-preserving surgery for soft tissue sarcomas.

There is uncertainty in the literature as to whether major vessel involvement in extremity soft tissue sarcomas constitutes an indication for amputation. This retrospective review includes 21 patients who underwent major vessel resection in the context of limb preservation for soft tissue sarcomas. Resected vessels were the common iliac in one, external iliac and common femoral in six, common and superficial femoral in five, superficial femoral in six, distal superficial and popliteal in two, and subclavian vessels in one. Wound infection occurred postoperatively in five patients (24%). One Gore-tex and one vein graft became exposed, but the wounds healed by secondary intention with routine wound care. Three patients (14%) manifested local recurrence, of which one required an amputation. The estimated 5-year survival rate is 63%. Involvement of major vessel(s) by soft tissue sarcomas of the extremities is not in itself an indication for amputation, as with en bloc resection of major vessels the local recurrence and 5-year survival rates parallel those of patients with soft tissue sarcomas not requiring major vessel resection.

Adult↗
PubMed2000

[Dilatation of large retinal vessels after increased intraocular pressure].

PURPOSE: To measure dilation of large retinal branch vessels. METHODS: Diameters of a vessel section of a branch artery and vein were examined by the retinal vessel analyzer. Intraocular pressure (IOP) was increased briefly by an oculo-oscillo-dynamograph. The examination was repeated after 2 weeks. RESULTS: A vessel reaction was found in all volunteers. The mean venous diameter decreased 9.9 +/- 9.4% during the suprasystolic phase of intraocular pressure. A maximal dilation was found in arteries (7.0 +/- 6.2%) and veins (9.3 +/- 5.2%) 1 min after lowering of IOP. The results were reproduced in the second examination for veins in all phases of the examination and for arteries in the middle phase after lowering IOP (4 min). Various changes in mean systolic blood pressure did not significantly affect reproducibility of the vessel reaction. CONCLUSION: The vessel reaction caused by rise in IOP can be measured for single vessel sections. The venous reaction is well reproducible in healthy volunteers. Further research should examine the benefit of this method in the diagnosis and follow-up of glaucoma.

Adult↗
PubMed2006

Immunolocalization of tight junction proteins in blood vessels in human germinal matrix and cortex.

Brain development occurs in a specialized environment maintained by a blood-brain barrier (BBB). An important structural element of the BBB is the endothelial tight junction (TJ). TJs are present during the embryonic period, but BBB impermeability accrues over an extended gestational interval. In studies of human premature infants, we used immunomicroscopy to determine if amounts of the TJ proteins ZO-1, claudin and occludin increase with gestational age in vessels of germinal matrix (GM) and cortex. By 24 weeks postconception (PC), TJ proteins were present in both GM and cortical vessels, but immunoreactivity in the GM of the youngest subjects was less than in older subjects. At 24 weeks PC, TJ protein immunoreactivity in GM vessels was less than in cortical vessels suggesting that TJ maturation progresses along a superficial to deep brain axis. This concept correlates with conclusions from previous analyses of the expression of brain endothelial cell alkaline phosphatase (AP) activity. AP appears in cortical vessels before appearing in deep white matter and GM vessels. Together, these data indicate that differentiation of some functional specializations is still in progress in GM vessels during the third trimester. This maturation could relate to the pathogenesis of germinal matrix hemorrhage-intraventricular hemorrhage.

Blood Vessels↗
PubMed2006

Efficacy and quality of vessel sealing: comparison of a reusable with a disposable device and effects of clamp surface geometry and structure.

BACKGROUND: During the past few years, a variety of energy-based techniques for vessel ligation have been introduced. With the use of a porcine model and different devices for bipolar vessel sealing (BiClamp and LigaSure), we studied the impact of different clamp surface structures on the efficacy and quality of vessel sealing. METHODS: Eight Swabian Hall pigs underwent splenectomy, nephrectomy, salpingo-oophorectomy, and small bowel resection with the use of bipolar vessel sealing devices designed for open and laparoscopic surgery. Vessel sealing with clamps with a smooth (nonstructured) surface (BiClamp for open surgery and LigaSure for laparoscopic surgery) was compared to that of clamps with a structured (grooved, wafer-like) surface (BiClamp for laparoscopic surgery and LigaSure for open surgery). Measurements of sealed vessels (2- to 7-mm diameter) included the seal failure rate, instrument sticking, and heat-associated morphological vascular wall alterations. RESULTS: Analysis of seal failures did not reveal significant differences between the different devices for both open [BiClamp, 17.9% (17/95); LigaSure, 15.5% (11/71)] and laparoscopic surgery [BiClamp, 2.8% (1/36); LigaSure, 8.6% (3/35)]. Comparing all data of structured versus smooth clamp surfaces, the seal failure rate was lower using clamps with a structured (11.2%) compared to a smooth surface (15.4%). Instrument sticking and thermal spread were found to be significantly increased after sealing with structured surfaces, regardless of whether devices designed for open (p < 0.05 and p < 0.001, respectively) or laparoscopic surgery (p < 0.001 and p < 0.01, respectively) were used. CONCLUSION: Clamps with a structured surface seem to be superior to those with a smooth surface for successful bipolar vessel sealing, as indicated by an increase of thermal spread. However, the more pronounced instrument sticking represents an undesired side effect and should encourage the search for more inert materials to further improve the sealing procedure.

Animals↗
PubMed1988

Ultrastructural characteristics of new vessels in proliferative diabetic retinopathy.

We studied the ultrastructural characteristics of 23 vascularized preretinal membranes removed from 22 eyes during pars plana vitrectomy for proliferative diabetic retinopathy. Traction detachment of the macula was the most frequent reason for surgery (15 of 22 eyes), followed by nonclearing vitreous hemorrhage (seven of 22 eyes). Vessels found in the membranes were studied by serial sectioning and categorized as having either developing, mature, or regressing characteristics. Developing vessels were seen in ten of 23 membranes (43%), mature vessels in 19 of 23 membranes (83%), and regressing vessels in 13 of 23 membranes (57%). Endothelial fenestrations and cell separations were rare. With three-dimensional reconstruction, we found that new vessels often extended cytoplasmic processes into the extracellular matrix and that lumina were present even at the distalmost tips of the vessels. Solid cords of endothelial cells were not seen. We concluded that in proliferative diabetic retinopathy, new vessels develop by a process of focal extracellular matrix degradation, generalized and exuberant extracellular matrix production, cytoplasmic microvillus extension into the extracellular matrix, and active lumen formation.

Adult↗
PubMed1993

Tone dependent nitric oxide production in ovine vessels in vitro.

We have determined the role of endogenous nitric oxide (NO) in regulation of vasomotor tone in ovine intrapulmonary and mesenteric vessels with resting tension and elevated vasomotor tone. Third generation intrapulmonary vessel rings and mesenteric vessel rings, 2-3 mm in diameter, were isolated from 20 sheep. NO production in the vessels was assessed by the change in tension induced by NG-nitro-L-arginine methyl ester (L-NAME), a competitive inhibitor of NO synthase. In vessels under resting tension, 10(-4) to 10(-3) M L-NAME induced a significant increase in tension only in veins but not in arteries. When tone was elevated with phenylephrine or U 46,619, a thromboxane A2 analogue, there was now a significant increase in tension in arteries with 10(-4) M L-NAME and in veins with 10(-5) M L-NAME. The increase in tension induced by L-NAME in veins was greater than that in arteries and greater when tone was elevated than under resting tension. Responses of pulmonary and mesenteric vessels were similar. Our data suggest that NO may play a role in regulating venous tone under baseline conditions and that the role of NO in regulation of vasomotor tone becomes more significant in the presence of nonspecific elevation of vasomotor tone in both arteries and veins. We speculate that endogenous NO production may be one mechanism by which pulmonary and systemic vessels counter the effects of vasoconstrictive agents.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMedDate not supplied

Effect of age on blood vessels and neurovascular appositions in the CA1 region of the rat hippocampus.

Rats aged 3, 9, 24 and 30 months were used in this study. Increased basal lamina thickening in capillaries, muscular large vessels and nonmuscular large vessels was shown with advancing age. There is also an age-related increase in the area of mitochondria in smooth muscle cells. These ultrastructural changes may underlie observed age-related functional changes in the vasculature. They may be a compensatory response of the vessel wall cells to a declining capacity to handle the continual and varying shear stress exerted by the blood. Ultrastructural differences between capillaries and the two types of large vessels are reported and discussed in terms of their functional significance. It was noted that there are more dendrites adjacent to capillaries than to large vessels, however, this was unaffected by increasing age. Since advancing age did not alter the number of neuronal processes adjacent to vessels, age-related compromises in vessel function may not be subjected to neuronal regulation.

Aging↗
PubMed1993

Acute effect of cigarette smoking on the coronary circulation: constriction of epicardial and resistance vessels.

OBJECTIVES: This study was performed to determine the acute effect of cigarette smoking on proximal and distal epicardial conduit and coronary resistance vessels. BACKGROUND: Cigarette smoking causes constriction of epicardial arteries and a decrease in coronary blood flow in patients with coronary artery disease, despite an increase in myocardial oxygen demand. The role of changes in resistance vessel tone in the acute coronary hemodynamic effect of smoking has not been examined. METHODS: Twenty-four long-term smokers were studied during cardiac catheterization after vasoactive medications had been discontinued. The effect of smoking one cigarette 10 to 15 mm long on proximal and distal conduit vessel segments was assessed before and immediately after smoking and at 5, 15 and 30 min after smoking (n = 8). To determine the effect of smoking on resistance vessels, coronary flow velocity was measured in a nonobstructed artery with a 3F intracoronary Doppler catheter before and for 5 min after smoking (n = 8). Eight patients were studied without smoking to control for spontaneous changes in conduit arterial diameter (n = 5) and resistance vessel tone (n = 3). RESULTS: The average diameter of proximal coronary artery segments decreased from 2.56 +/- 0.12 mm (mean +/- SEM) before smoking to 2.41 +/- 0.09 mm 5 min after smoking (-5 +/- 2%, p < 0.05). Distal coronary diameter decreased from 1.51 +/- 0.07 to 1.39 +/- 0.06 mm (-8 +/- 2%, p < 0.01). Marked focal vasoconstriction after smoking was observed in two patients. Coronary diameter returned to baseline by 30 min after smoking. There was no change in vessel diameter in control patients. Despite a significant increase in the heart rate-mean arterial pressure product, coronary flow velocity decreased by 7 +/- 4% (p < 0.05) and coronary vascular resistance increased by 21 +/- 4% (p < 0.01) 5 min after smoking. There was no change in these variables in the control subjects. CONCLUSIONS: Smoking causes immediate constriction of proximal and distal epicardial coronary arteries and an increase in coronary resistance vessel tone, despite an increase in myocardial oxygen demand. These acute coronary hemodynamic effects may contribute to the adverse cardiovascular consequences of cigarette smoking.

Analysis of Variance↗
PubMed1993

Intracoronary stenting compared with conventional therapy for abrupt vessel closure complicating coronary angioplasty: a matched case-control study.

OBJECTIVES: A case-control analysis was performed to compare clinical outcome after intracoronary stenting with that after conventional therapy for abrupt vessel closure. BACKGROUND: Previous studies have demonstrated that stenting after abrupt vessel closure results in marked angiographic improvement and preservation of coronary flow, leading to the anticipation of similar improvement in clinical outcome. METHODS: Sixty-one of 92 consecutive patients treated at two clinical sites by intracoronary stenting for abrupt vessel closure were matched, according to angiographic features of closure and estimated left ventricular mass threatened by ischemia, with patients treated conventionally during the 18 months before stent availability. In 33 pairs of matched patients, vessel closure was established; in 28 pairs, it was threatened (coronary dissection or worsening stenosis with preservation of normal anterograde flow). Baseline clinical and angiographic characteristics were comparable in the two matched groups. Patients with indeterminate mechanisms of total occlusion (31%) or dissections < 15 mm long (43%) predominated; patients with visible thrombus (8%) or dissections > 15 mm long (18%) were infrequently represented. Stents were successfully deployed in 60 of 61 patients at a median of 52 min (range 3 to 269) after the onset of closure. RESULTS: When compared with conventional treatment, stenting resulted in less residual stenosis (26% vs. 49% diameter stenosis, p < 0.001), a greater likelihood of restoration of Thrombolysis in Myocardial Infarction (TIMI) grade 3 blood flow (97% vs. 72%, p < 0.001) and a reduction in the need for emergency bypass surgery (4.9% vs. 18%, p = 0.02). However, the incidence of Q wave myocardial infarction was nearly the same in the two groups (32% vs. 20%, respectively, p = NS). In the group with stenting, peak creatine kinase level and the frequency of Q wave infarction after established vessel closure increased with the time to stent placement (p = 0.001 and 0.054, respectively); the incidence of procedure-related Q wave infarction in patients who underwent stenting within 45 min of closure was very low (3.9%). In-hospital death occurred in 3.3% of patients in each treatment group. At a mean of 6.3 months of follow-up after hospital discharge, survival free from late cardiac death, myocardial infarction, bypass surgery or coronary angioplasty was 74.9% and 81.3% in the stent and the control treatment group, respectively (p = NS). CONCLUSIONS: Although early treatment of established vessel closure by intracoronary stenting was associated with a low incidence of both myocardial infarction and emergency bypass surgery, the likelihood or severity of infarction was not reduced among those in whom stents were implanted later. Patients with threatened vessel closure could not be shown to benefit from stent treatment. These data provide preliminary indications for stent placement in the acute period to be validated in larger randomized studies.

Acute Disease↗