Quantitation of collagen fibril cross-section profiles in aging human veins

The cross-section profiles and the diameter distribution of collagen fibrils were examined quantitatively in normal human internal jugular veins at different ages (first, fifth, and eighth decades). All fibrils showed a regular cross-striation pattern of native-type collagen fibrils irrespective of their cross-section profiles. Irregularly outlined ("dysplastic") fibrillar profiles were observed among the normally occurring circular cross-section profiles. The frequency of such unusual fibrils significantly increased with age. This increase was more pronounced in the tunica media as compared with the tunica adventitia. In the tunica media diameters of collagen fibrils also generally increased with age. In the tunica adventitia, on the other hand, fibrillar diameters were not significantly altered at different ages. The results of this study indicate that the frequency of both the irregularly outlined fibrillar cross-section profiles and increased fibrillar diameters depends on age in normal vascular walls. Therefore, it is concluded that the occurrence of "dysplastic" fibrils is a physiologic age-related phenomenon rather than a morphologic sign of pathologic alteration of collagen. The higher frequency of irregularly outlined collagen fibrils in the tunica media may indicate a higher and/or altered synthetic behavior of smooth muscle cells when compared with fibroblasts of the tunica adventitia.

Intimal thickening of jugular and femoral veins vs arteries in the rabbit following investment

The authors induced intimal thickening in the jugular and femoral veins and in the common carotid and femoral arteries of rabbits by placement of a polyethylene tube cuff. The comparative effects on the intima were studied by light and electron microscopy. Even in the veins, thickening resulted from the migration of medial smooth muscle cells into the intima with subsequent proliferation. Thickening in the arteries consisted of tightly packed smooth muscle cells and a few elastic fibers, whereas that in the veins was characterized by an abundance of collagen fibers, layers of smooth muscle cells, and a few elastic fibers. Capillaries were often observed in the thickened intima of the veins but not of the arteries.

The effect of rigid external support on vein graft adaptation to the arterial circulation

In previous experiments vein graft wall thickening stopped when the ratio of lumen radius to wall thickness equaled that of a normal artery. This led us to postulate that wall stress, which this ratio determines, regulates wall structure. To test this hypothesis we studied the effect of decreasing lumen radius and acutely diminishing wall stress with a rigid, external support. Jugular vein grafts were interposed into the carotid artery of rabbits. The proximal half of the grafts was wrapped with a polytetrafluoroethylene graft. Twelve veins received a tight wrap (2.5 or 3 mm diameter) that decreased the graft diameter, and four received a loose wrap (5 mm diameter) that did not. These grafts were fixed by perfusion after 1 day, 11 days, or 12 weeks. Wall thickness was slightly less in all tight-wrap segments. Total cross-sectional wall area, smooth muscle cell volume, and matrix deposition were significantly reduced in tight-wrap segments. These differences were greatest at 11 days. The observation that narrowing and external support of these vein grafts causes reduction of wall area supports the hypothesis that increased wall stress might be an important stimulus for wall thickening.

Leukocyte mediated vein injury and thrombosis is reduced by a lipoxygenase inhibitor

We have previously demonstrated an in vivo model of deep vein thrombosis which suggests that the neutrophil promotes vascular injury and thrombosis following blood flow stasis. Since leukotrienes are potent mediators of vascular injury and neutrophil (PMN) chemotaxis, we wished to determine if in vivo inhibition of 5-lipoxygenase would reduce neutrophil mediated events in our model. Lipoxygenase was inhibited in vivo with 2,3-diethyl-4-methoxy,1-naphthalenol acetate (U-66,855). The in vivo activity of U-66,855 was demonstrated in 4 cats. Each animal was treated with 5 mg/kg of U-66,855 intravenously. Blood cell leukotriene B4 (LTB4) and thromboxane A2, via its metabolite thromboxane B2 (TBX2) was assessed before and 30, 60, and 120 min after dosing. Blood cell LTB4 and TBX2 production was stimulated by A23187 (24 microM) and assayed by radioimmunoassay. We exposed and isolated a 3-cm segment of the jugular veins from 10 additional cats 5 of which were treated with U-66,855 (5 mg/kg, iv). In order to assess the effect of stasis, the jugular veins were ligated at the thoracic inlet for 2 hr after which the veins were perfused, fixed in 2.5% glutaraldehyde, and prepared for electron microscopy. U-66,855 reduced LTB4 production significantly (P less than 0.01), but not TBX2. In untreated cats, PMNs adhered to and migrated underneath the venous endothelium. Additionally, platelets, fibrin and formed thrombi were found on the basement membrane exposed by the migrating neutrophils. In contrast, we observed significantly reduced PMN adhesion as well as no fibrin deposition in veins obtained from cats treated with U-66,855. The results suggest that 5-lipoxygenase inhibition can significantly reduce undesirable neutrophil/vessel wall interactions.

Thrombin uptake and inhibition on heparinized polytetrafluoroethylene (PTFE) grafts and native sheep vessels

Non-heparinized and covalently-heparinized PTFE grafts, sheep aorta, carotid artery and jugular vein were evaluated according to their ability to adsorb and inactivate thrombin. All surfaces, except non-heparinized PTFE caused considerable losses of enzymatically active thrombin from the solution. Covalently-heparinized PTFE and jugular veins adsorbed thrombin, which was inactivated on subsequent contact with antithrombin III. Despite the same loss from the solution as was encountered with veins arteries adsorbed significantly smaller amounts of thrombin. Protamine treatment of covalently-heparinized PTFE almost totally abolished the ability to adsorb thrombin. It is concluded that 1) arteries possess a stronger thrombin inhibitory capacity than veins, possible explanations to this being a different glucosaminoglycan or the presence of antithrombin III in the arterial wall and 2) that heparinizing PTFE results in a pronounced ability to inactivate thrombin.

[Experimental studies of autologous vein grafts for arterial defect, using fibrin glue]

Compared with end-to-end anastomosis, the procedure for veingrafting is time-consuming and troublesome. The purpose of this study was to resolve these problems. The common carotid artery of the rats was grafted by the jugular vein. The principle of sleeve anastomosis was applied at the proximal suture site and fibrin glue was used at both suture sites to prevent leakage. This method was performed in 67 rats, and conventional veingrafts were done in 41 rats. A high patency rate of 98% and a shortened operating time were obtained in this method. An advantage of this procedure was a reduction in the number of stitches, which reduced the operating time and ensured good vascular healing.

Combined dihydroergotamine and heparin prophylaxis of postoperative deep vein thrombosis: proposed mechanism of action

The cause of postoperative DVT is considered to be changes in blood coagulation, stasis of blood within the veins, and injury to the vein wall. The coagulation changes have been investigated and documented and involve platelet activation, stimulation of the coagulation cascade, and blunting of endogenous fibrinolytic activity. Stasis has been objectively identified by retention of contrast material in soleal sinuses and marked changes in venous flow velocity in patients in the supine position and in those under general anesthesia. Vein wall injury is more controversial, but has been shown to be directly related to venodilation. Such dilation of veins occurs in response to operative trauma, hence venous endothelial damage most likely plays a part in the milieu responsible for postoperative DVT. The prophylaxis provided by the combination of dihydroergotamine and heparin appears to affect each of the three limbs of Virchow's triad. Heparin achieves its prophylactic benefit by activating antithrombin III. Activated antithrombin III affects numerous sites in the coagulation cascade. It has been shown that 1 micrograms of antithrombin III inhibits the formation of 1 unit of thrombin; however, in the presence of heparin, 1 micrograms of activated antithrombin III inhibits 750 units of thrombin. Dihydroergotamine increases venous smooth muscle tone without affecting arteriolar smooth muscle. Hence, it has the effect of preventing stasis without increasing blood pressure. It also affects the platelet membrane, prostaglandin synthesis, and blood distribution, although these findings need to be elucidated. The combination of dihydroergotamine and heparin seems to have a synergistic prophylactic effect in preventing postoperative DVT. Heparin modifies the coagulation changes, whereas dihydroergotamine minimizes stasis and potentially prevents the endothelial damage caused by excessive operative venodilation. Such a combination of effects can explain the synergistic prophylactic efficacy found when dihydroergotamine and heparin were employed in combination in the multicenter trial [42].

The relationship between vessel wall injury and venous thrombosis: an experimental study

The relative importance of stasis, vessel wall damage and hypercoagulability in the pathogenesis of venous thrombosis remains disputed. While the combination of local vascular stasis and systemic hypercoagulability can be shown to produce experimental thrombi within a few minutes, it has been claimed that vessel wall damage is also a necessary component of venous thrombogenesis. In this experimental study, mechanical crushing of the jugular veins produced patchy areas of denuded endothelium, with underlying vessel wall oedema, as seen by ultrastructural examination. While the exposed subendothelium became covered with activated platelets following restored blood flow, there was no fibrin formation after 5 min. When blood flow was restored for 60 min following the crush injury, white cells could be seen adhering to and migrating through the vessel wall, although there was still no visible fibrin. The addition of venous stasis for 20 min did not lead to the formation of stasis thrombi in association with the damaged areas. The present experiments demonstrate that, far from there being subtle endothelial damage contributing to acute venous thrombosis, even readily demonstrable damage is a poor stimulus to fibrin formation at local sites of vessel wall injury.

Comparative evaluation of the effects of an ionic vs. a nonionic contrast medium on the venous endothelium. Preliminary scanning electron microscopic observations

Isolated segments of the right jugular veins of six mongrel dogs were exposed to solutions of 60% diatrizoate (3 dogs) and 60% iopamidol (3 dogs) in vivo. Normal blood flow was re-established after 3 minutes of exposure to the contrast material. The left jugular veins served as controls. Veins were harvested at 1, 24, and 48 hours and studied by light and scanning electron microscopy. Changes consisting of cellular swelling, denudation, platelet aggregation and fibrin deposition were uniform and prominent with diatrizoate. Response to iopamidol was minimal consisting only of cellular swelling. The study suggests that post-phlebographic thrombophlebitis may be reduced by the use of nonionic contrast materials.

Scanning electron-microscopic study of experimentally induced intimal tears in rabbit arteries

A scanning electron-microscopic study of the intimal surface of anastomosed arteries of experimental arteriovenous fistulae in 20 rabbits was conducted to determine the effect of altered haemodynamics on the arterial wall. Control arteriotomies were performed on 12 animals on the contralateral common carotid arteries. The rabbits were killed from 1 to 447 days postoperatively. Transverse intimal tears involving the internal elastic lamina developed in both proximal and distal segments of the anastomosed artery as early as 5 days postoperatively. Some were covered with thrombus and attenuated endothelial cell remnants, but all tears became endothelialised by 7 days. Endothelial cells in the floor of the tears had prominent nuclei and were smaller and more plentiful than the normal intima but, in longstanding fistulae, they resumed a more elongated spindle shape. Tears similar to those in the experimental arteries were found in most control arteriotomies, being confined to the suture zone. The results reveal the profound effect of altered haemodynamics on the arterial wall.

Intimal hyperplasia in arterial autogenous vein grafts: a new animal model

A new animal model is presented, in which the changes in arterial autogenous vein grafts in rabbits can be studied. Intimal hyperplasia has developed four weeks after grafting. The thickness of the intima has been measured at this time. The potential uses of the model are discussed.

Total hip replacement induces injury to remote veins in a canine model

The effects of total hip replacement on the condition of the luminal surface of the jugular and femoral veins and the carotid and femoral arteries were studied in healthy dogs. Four hours after the completion of surgery, most of the blood was removed by whole-body perfusion and the vessels were partially fixed in situ by glutaraldehyde perfusion, harvested, and prepared for scanning electron microscopy. In control dogs (held under anesthesia) the luminal surfaces of the veins (including valves and confluences) and arteries were covered by intact endothelium and were free of adhering blood cells. The arteries from dogs that were operated on were also free of damage. In contrast, the veins from dogs that were operated on showed a series of roughly parallel microtears around 70 to 80 per cent of the confluences of the side branches with the jugular or femoral vein. The basement membrane as well as the endothelial sheet was torn, thereby exposing underlying connective-tissue fibers and smooth muscle cells. The endothelium separated along intercellular junctions. The tears were infiltrated with many leukocytes and platelets and some erythrocytes. Subtle endothelial changes and patchy leukocyte adhesion occurred away from the side branches. The mechanism or mechanisms remain to be elucidated.

The effects of embolectomy-thrombectomy catheters on vascular architecture

The purpose of this report is to describe the evolution of an embolectomy-thrombectomy catheter (ETC) injury over a six week period. Carotid arteries and jugular veins in six adult dogs were subjected to ETC withdrawals at a standard velocity and balloon size. Vascular segments were excised as early as one hour and as late as six weeks. The specimens were prepared for light, scanning electron and transmission electron microscopic examination. In early specimens, arteries and veins showed endothelial denudation followed by regeneration. In later specimens, the arteries showed progressive disruption of the internal elastic lamina and marked subendothelial proliferation (arteriosclerosis). By the sixth week the artery's intima was equal in thickness to the media. The veins showed only regenerating endothelium without alterations of the subendothelium. Exposure of canine vasculature to ETC procedures caused pronounced transmural damage in the arteries and only endothelial alterations in the veins.

Ultrastructure of human and transplanted canine veins: effects of different preparation media

Human saphenous veins were studied to determine alterations resulting from preparation by moist gauze wrapping, balanced salt solution immersion, and heparinized whole blood storage at 4 degrees C. Morphologic derangements of endothelial cells, smooth muscle cells, and adventitial tissues were pronounced in the nonblood preparations. In a second study, 20 canine jugular vein segments were interposed into the iliofemoral arterial circulation, with half the grafts prepared in balanced salt solution and half in whole blood. Veins were harvested monthly for 10 months, being subjected to light and electron microscopic examinations. No thromboses or stenoses occurred. Diffuse graft dilatation affected veins three times more often when stored in lactated Ringer's solution than when stored in heparinized blood. Medial thinning, ranging from 20% to 54%, occurred in veins stored in the balanced salt solution. Endothelial regeneration was complete in all grafts within 30 days after implantation. However, medial and adventitial injury to veins prepared in balanced salt solution appeared progressive, with fibrodysplastic tissue replacing smooth muscle cells. Plasmacytosis and neutrophil infiltrates, consistent with chronic active inflammation, often accompanied fibroproliferative changes. Alterations in medial structures, rather than endothelial injury, may have an important influence on the long-term durability of transplanted vein grafts.

Scanning electron-microscopic study of the inner surface of experimental aneurysms in rabbits

A scanning electron-microscopic study of the inner surface of experimental saccular aneurysms in rabbits was conducted to demonstrate the effects of haemodynamics on the aneurysmal wall. Animals with aneurysms were killed from 2 to 83 weeks postoperatively, and the controls from 7 to 51 weeks. In both series, re-endothelialization was complete in approximately 2 weeks. In control tissue endothelium was normal, and sutures caused mild distortion of the luminal surface. In the aneurysms, there were tracts of spindle-shaped cells, often arranged in whorl-like patterns and interspersed with regions of polyhedral cells with thickened intercellular borders, prominent stomata and numerous microvilli. In some areas, long filamentous intercellular processes were prominent. The few jet lesions seen were covered with polyhedral cells and were less complex than those in arteriovenous fistulae. Ridges, caused by elevated subendothelial connective tissues were crescentic or circular, outlining depressions and craters, as if delineating vortices. The carotid artery opposite the aneurysm exhibited endothelium similar to normal tissue, except in older aneurysms where corrugations caused by the internal elastic lamina were completely or partially absent. The experiments demonstrate the effect of intra-aneurysmal haemodynamics on the topography of the endothelium and subendothelial tissues of the sac wall, and support the concept that endothelial topography in the vascular system under physiological conditions is haemodynamically determined.

Aggressive meningioma with jugular vein extension. Case report with ultrastructural observations

A meningioma that was seen initially as a mass in the upper portion of the neck in a 44-year-old woman was studied by light and electron microscopy. Light microscopy demonstrated that the tumor was within the lumen of the internal jugular vein. Ultrastructural features led to the diagnosis of meningioma. The clinical findings indicate that the tumor arose within the cranial cavity, invaded a venous sinus, and extended down the internal jugular vein into the upper portion of the neck.

Autogenous vein graft thrombosis following exposure to calcium-free solutions (calcium paradox)

The morphological and functional effects of calcium-free and calcium-containing solutions on canine jugular vein intima were examined under conditions which closely resemble those techniques currently employed in peripheral vascular and aortocoronary bypass surgery. Veins that had been exposed only to calcium-containing solutions remained patent for the duration of the experimental period. Vein perfusion with a calcium-free solution, however, resulted in disruption of the jugular vein intima once calcium ions were reintroduced. Autogenous as a femoral arterial graft became thrombosed within 60 minutes. It is therefore suggested that vein grafts of autogenous origin be irrigated with calcium-containing solutions to prevent intimal damage and thrombosis.

Passage of extravascular tracers into canine jugular veins and carotid arteries

Biologically active substances arising in the interstitial space (cell-fiber matrix) of a medium-sized blood vessel or in surrounding tissue might reach the lumen by diffusion. Substances so delivered to the vessel wall-blood interface would be situated to effectively influence the endothelium and to initiate deposition of blood elements on the luminal surface of vessels, thereby contributing to thrombosis and atherosclerosis. This study showed that 125I, 125I-albumin and 125I-fibrinogen passed across the walls of segments of canine jugular veins and carotid arteries that were maintained under 20 cm H2O presure while being suspended in solutions containig the radioactive substances. The ratio of 125I to 125I-protein (albumin, fibrinogen) was predictably greatly increased by diffusion across the vessel wall. Frozen sections cut parallel with the luminal surface of flattened segments of vessels showed a gradient of radioactivity from adventitial to luminal surface of the vessels. Part of the fibrogen (but no albumin) that had reached the inside of the vessel had been broken down into fragments. These observations show that ions and proteins originating in perivascular fluid transverse the wall of medium-sized veins and arteries, presumably by diffusion across complex water-filled channels. Thus biologically active substances arising in perivascular tissue or in the vessel wall itself can be expected to reach the luminal surface of the vessel wall where they can influence endothelium and/or initiate deposition of blood elements on the vessel wall. Furthermore, the action of proteolytic enzymes on protein molecules such as zymogens might give rise to active substances not previously present.

Inhibition of leukocyte locomotion by tocainide, a primary amine analog of lidocaine: at study with 111indium-labeled leukocytes and scanning electron microscopy

The ability of tocainide (a primary amine derivative of lidocaine, 2-amino 2, 6-propionoxylidide) to inhibit leukocyte adhesion to and invasion of canine jugular veins was investigated. Leukocyte adhesion and migration were quantitated by use of 111indium-labeled leukocytes, and the morphologic characteristics of leukocytes and vessel lumen were studied by scanning electron microscopy. The morphologic characteristics of adhering and migrating 111indium-labeled leukocytes were similar to leukocytes that had not been manipulated, thus establishing their suitability for use as a marker for flammation. Exposure of leukocytes to 200 micrograms. per ml. of tocainide in autologous plasma in vitro inhibited adhesion and migration by 68 per cent. When labeled leukocytes were returned to the donor and exposed to intravenously infused tocainide the extent of reduction in adhesion and migration depended on whether tocainide infusion was started before or after neck dissection. Inhibition was only 46 per cent when dissection and injection of 111indium-labeled leukocytes preceded the start of infusion of tocainide but was 87 per cent when tocainide infusion was started before dissection and injection of leukocytes. The plasma level ranged from 25 to 47 microM over the 3 hour, 20 minute-infusion period, being 35 to 40 microM for the last hour. Migration of leukocytes across interendothelial junctions and their accumulation between the endothelial sheet and the basement membrane caused extensive damage to the endothelial lining of these veins. This was reduced when leukocyte migration was reduced. These observations suggest that the leukocyte-induced damage occurring in some sterile inflammations might be reduced by the use of local anesthetic drugs.

The influence of systemic aspirin on rat small diameter vein grafts: a scanning electron microscopic study

Small diameter vein grafts have been shown previously to have a poor patency rate unmedicated rats. Oral aspirin administered to male and female rats for one week pre-operatively reduced the number of platelets laid down on the luminal surface of their grafts, and resulted in a greater number of grafts remaining patent up to one hour after the blood flow through them had been established. The patency rate of grafts examined one to 17 weeks after operation was significantly better in female rats than in males given aspirin pre- and post-operatively. The different effect of aspirin in preventing thrombosis of the vein grafts of the two sexes makes its clinical usefulness for this purpose suspect.

The endothelial surface of large veins of rabbit: scanning electron microscopic observations

The following veins of the rabbit were fixed by perfusion and studied systematically by scanning electron microscopy: sagittal sinus, confluence of sinuses, external jugular vein, superior vena cava, inferior vena cava, greater saphenous, and femoral veins. One result is that the shape and arrangement of endothelial cells of the veins are obviously influenced by hemodynamic shear forces. Two types of subendothelial fibres were demonstrated: "cross-fibers" which correspond to the circular inner muscle cells of the media, and "longitudinal fibers" which correspond to the intimal meshwork of connective tissue fibers. Regional differences are demonstrated in the occurrence of these fibres. Moreover, five morphologically different venous valve types are observed. The functional significance of these different valve types is not yet known.