Bright quantum dots emitting at ∼1,600 nm in the NIR-IIb window for deep tissue fluorescence imaging.

With suppressed photon scattering and diminished autofluorescence, in vivo fluorescence imaging in the 1,500- to 1,700-nm range of the near-IR (NIR) spectrum (NIR-IIb window) can afford high clarity and deep tissue penetration. However, there has been a lack of NIR-IIb fluorescent probes with sufficient brightness and aqueous stability. Here, we present a bright fluorescent probe emitting at ∼1,600 nm based on core/shell lead sulfide/cadmium sulfide (CdS) quantum dots (CSQDs) synthesized in organic phase. The CdS shell plays a critical role of protecting the lead sulfide (PbS) core from oxidation and retaining its bright fluorescence through the process of amphiphilic polymer coating and transferring to water needed for imparting aqueous stability and compatibility. The resulting CSQDs with a branched PEG outer layer exhibited a long blood circulation half-life of 7 hours and enabled through-skin, real-time imaging of blood flows in mouse vasculatures at an unprecedented 60 frames per second (fps) speed by detecting ∼1,600-nm fluorescence under 808-nm excitation. It also allowed through-skin in vivo confocal 3D imaging of tumor vasculatures in mice with an imaging depth of ∼1.2 mm. The PEG-CSQDs accumulated in tumor effectively through the enhanced permeation and retention effect, affording a high tumor-to-normal tissue ratio up to ∼32 owing to the bright ∼1,600-nm emission and nearly zero autofluorescence background resulting from a large ∼800-nm Stoke's shift. The aqueous-compatible CSQDs are excreted through the biliary pathway without causing obvious toxicity effects, suggesting a useful class of ∼1,600-nm emitting probes for biomedical research.

Some Peculiarities of Local Distribution of Multipotent Mesenchymal Stromal Cells after Their Injection into Intact Muscle Tissue in Experiment.

Changes in the muscular tissue after subcutaneous injection of autologous bone marrow multipotent mesenchymal stromal cells transfected with GFP gene and additionally stained with cell membrane dye Vybrant CM-Dil in the projection of ligated femoral vein were studied by light microscopy with luminescence. Stromal cells injected through the skin can appear not only in the damaged tissue where acceleration of regeneration processes is required, but also in intact structures located in superficial or deeper layers. In intact muscular tissue, stromal cells spreading in the perivascular tissue initiate inflammation and migration of macrophages, activate and even trigger sclerotic processes due to differentiation into connective tissue cells (fibroblasts) and stimulation of proliferation and collagen synthesis by host fibroblasts. Injected multipotent mesenchymal stromal cells are gradually phagocytized by macrophages.

Knitted nitinol represents a new generation of constrictive external vein graft meshes.

OBJECTIVE: Constriction of vein grafts with braided external nitinol meshes had previously led to the successful elimination of neointimal tissue formation. We investigated whether pulse compliance, smaller kink-free bending radius, and milder medial atrophy can be achieved by knitting the meshes rather than braiding, without losing the suppressive effect on intimal hyperplasia. METHODS: Pulse compliance, bending stiffness, and bending radius, as well as longitudinal-radial deformation-coupling and radial compression, were compared in braided and knitted nitinol meshes. Identical to previous studies with braided mesh grafts, a senescent nonhuman primate model (Chacma baboons; bilateral femoral interposition grafts/6 months) mimicking the clinical size mismatch between vein grafts and runoff arteries was used to examine the effect of knitted external meshes on vein grafts: nitinol mesh-constricted (group 1); nitinol mesh-constricted and fibrin sealant (FS) spray-coated for mesh attachment (group 2); untreated control veins (group 3), and FS spray-coated control veins (group 4). RESULTS: Compared with braided meshes, knitted meshes had 3.8-times higher pulse compliance (3.43 ± 0.53 vs 0.94 ± 0.12%/100 mm Hg; P = .00002); 30-times lower bending stiffness (0.015 ± 0.002 vs 0.462 ± 0.077 Nmm(2); P = .0006); 9.2-times narrower kink-free bending radius (15.3 ± 0.4 vs 140.8 ± 22.4 mm; P = .0006), and 4.3-times lower radial narrowing caused by axial distension (18.0% ± 1.0% vs 77.0% ± 3.7%; P = .00001). Compared with mesh-supported grafts, neointimal tissue was 8.5-times thicker in group I (195 ± 45 µm) vs group III (23.0 ± 21.0 µm; P < .001) corresponding with a 14.3-times larger neointimal area in group I (4330 ± 957 × 103 µm(2)) vs group III (303 ± 221× 103 µm(2); P < .00004). FS had no significant influence. Medial muscle mass remained at 43.4% in knitted meshes vs the 28.1% previously observed in braided meshes. CONCLUSION: Combining the suppression of intimal hyperplasia with a more physiologic remodeling process of the media, manifold higher kink-resistance, and lower fraying than in braided meshes makes knitted nitinol an attractive concept in external vein graft protection.

Side-to-side sutureless vascular anastomosis with magnets.

OBJECTIVE: Abbe and Payr introduced vascular techniques and devices to facilitate vessel anastomosis over a century ago. Obora published the idea of a sutureless vascular anastomosis with use of magnetic rings in 1978. The purpose of this study was to assess the performance of a new magnetic device to perform a side-to-side arteriovenous anastomosis in a dog model. MATERIAL AND METHODS: Male fox hounds (25 kg) were treated preoperatively and daily postoperatively with clopidogrel bisulfate (Plavix) and aspirin. The femoral artery and vein were exposed unilaterally in 3 dogs and bilaterally in 4 dogs (n = 11 anastomoses). A 4-mm arteriotomy was performed, and 1 oval magnet 0.5 mm thick was inserted into the lumen of the artery and a second magnet was applied external to the artery, compressing and stabilizing the arterial wall to create a magnetic port. An identical venous magnetic port was created with another pair of oval magnets. When the 2 ports were allowed to approach each other, they self-aligned and magnetically coupled to complete the arteriovenous anastomosis. Patency was assessed for the first hour with direct observation, again after 9 weeks with duplex ultrasound scanning, and at 10 weeks under direct open observation. The anastomoses were explanted after 10 weeks. Hydrodynamic resistance was measured ex vivo on the final 8 anastomoses by measuring the pressure drop across an anastomosis with a known flow rate. RESULTS: After implantation, very high flow created visible turbulence and palpable vibration. All 11 anastomoses were patent under direct observation and palpation. Ten of 11 anastomoses were clearly patent on duplex scans, and patency of 1 anastomosis was questionable. Hydrodynamic resistance averaged 0.73 +/- 0.33 mm Hg min/mL (mean +/- SEM). CONCLUSIONS: Vascular anastomoses performed with magnets demonstrated feasibility; exhibited 100% patency after 10 weeks in a dog arteriovenous shunt model; lacked apparent aneurysm or other potentially catastrophic failure; demonstrated remodeling of the vessel wall after several weeks to incorporate the magnets, making the magnetic force unnecessary; and warrants further study in vessels with different sizes, flow rates, and locations. CLINICAL RELEVANCE: We present a magnet-based device used to perform side-to-side peripheral vascular anastomoses. Its advantages include the ability to anastomose vessels without requiring circumferential surgical exposure. Vascular anastomosis performed with these magnets demonstrated 100% patency in the dog, lacked apparent aneurysm or other potentially catastrophic failure, and demonstrated remodeling of the vessel wall after several weeks, to incorporate the magnets, making indefinite retention of field strength unnecessary. This technique could enable minimally invasive procedures, such as complex reconstructive and revascularizing surgery, and warrants further study in vessels with different sizes, flow rates, and locations.

Ultrastructural analogies between intimal alterations in veins from diabetic patients and animals with STZ-induced diabetes.

The aim of this study was to document similarities and differences between veins from human diabetic patients and an experimentally induced diabetic animal model. The saphenous vein and posterior tibial vein from diabetic patients and the femoral vein from rats were studied. An increase in the extracellular matrix with migration of smooth muscle cells and endothelial alterations were observed in the intima of all specimens. These findings demonstrate that there is a high degree of similarity between the pathological changes in the venous wall during human diabetes mellitus and streptozotocin (STZ) induced-diabetes. This finding validates STZ induced-diabetes in rats as a model for further experimental study to clarify the fate of the diabetic venous wall when used as a graft.

Experimental study of mechanical microvascular anastomosis with new biodegradable ring device.

The commercially available mechanical vascular anastomotic device with ring-pin technique employs polyethylene rings and stainless steel pins, but even after healing of the anastomotic site, the ring remains. To resolve this disadvantage, the ring material was replaced by biodegradable material, and a ring coupling device was fabricated. This new ring was used to anastomose the femoral vein of rabbits, and morphological observations were made macroscopically and by light and scanning electron microscopy. Of the 58 anastomosed veins, 54 were patent, giving a patency rate of 92.9%. The ring was largely absorbed 15 weeks after anastomosis and completely after 30 weeks. Histologically, re-endothelialisation was observed in 1 week. Infiltration of inflammatory cells was significant around the ring at 3 weeks, but inflammation subsided within 6 weeks. There were no findings indicating adverse effects of the stainless steel pins remaining outside the vascular wall.

Long-term studies of cold-stored rabbit femoral artery and vein autografts.

UNLABELLED: In previous studies we have shown that 80-100% of rabbit femoral vascular autografts cold-stored at 4 degrees C for 3 weeks remain patent 3 weeks after reinsertion in the femoral artery. The present study reports the effect on graft patency of increasing either the period of cold storage prior to reinsertion or the duration of reperfusion to 6 months. Rabbit femoral blood vessels were cold-stored (CS) at 4 degrees C for varying periods. CS autografts were reinserted into the contralateral leg for 3 weeks or 6 months. Graft patency was determined and grafts examined by histological, immunohistochemical and electron microscopical techniques. Six months after reinsertion patency of 4-week CS arterial and 1-week CS venous grafts was 40% and 27% respectively, very much lower than the 80-100% seen after 3 weeks reperfusion. Arterial grafts CS for 6 months had a patency rate of 70% after 3 weeks reperfusion but 0% after 6 months. Morphological examination suggests that the delayed failure of cold-stored vascular grafts is caused by thrombus superimposed on intimal hyperplasia within the graft. CONCLUSIONS: Cold-stored vascular grafts are useful prostheses when only 3-4 weeks graft patency is required. They are not suitable for use when long-term graft patency is needed.

Participation of angiogenesis from rat femoral veins in the neovascularization of adjacent occluded arteries.

The neovascularization of the arterial wall in human and experimental pathology has been demonstrated. The occlusion of the of the rat femoral artery is a suitable model for the study of these angiogenesis processes. Newly formed capillaries growing into the arterial wall have been described in this model. The origin of these ingrowing capillaries has been attribute to the preformed surrounding venules and capillaries. The contribution of the adjacent femoral vein with a supplementary population of vascular sprouts could also be possible. To test this hypothesis in half of the occluded arteries, the adventitia was removed from the side facing the femoral vein. Between 1 and 3 days after surgery several alterations were found both in the endothelial cells and the smooth muscle cells of the tunica media. Between 3 and 6 days, solid or canalized endothelial sprouts were observed arising from the femoral vein. By days 4 and 6, newly formed capillaries grew into the adventitia and tunica media of the femoral artery. Some of them, penetrated the internal elastic lamina. This microvascular penetration from the femoral vein was more prominent in the area of the ostium of the collateral and when the adventitia was removed. Some ingrowing capillaries were in continuity with the endothelial cells of the arterial neointima. At days 7 and 8, regressing capillaries were observed in the neomicrovasculature network between artery and vein, with a selective loss of the smaller vessels. From day 9 onwards, fewer and larger vascular channels were present between the femoral vein and the femoral artery. An arterial neolumen contained what appeared to be circulating "fresh" blood. Quantitatively, the venous neocapillary density increased from days 4 to 6 and then declined significantly by day 8. The arterial neocapillary density increased form days 4 to 8 and declined significantly by day 12. Moreover, both densities were significantly greater when the arterial adventitia was removed. The perfusion with barium solution showed the presence of the contrast material in the newly formed vessels, the lumen of the femoral vein, and the neolumen of the occluded arterial segment. The present findings indicate that putative angiogenic molecules released form the occluded arterial segment may reach the adjacent wall of the vein inducing neovascularization from it. The vein vascular sprouts are connected to the ingrowing capillaries in the occluded arterial wall and to the neocapillaries form the preexisting pericytic microvasculature. When the arterial adventitia were removed up to 2 times greater vein neocapillary's density was observed suggesting an easily access of the putative angiogenic factors to the vein.

Microscopic observations on the great saphenous vein at the upper third level of the thigh and at the level of discharge into the femoral vein

For the microscopical study of the great saphenous vein wall, the venous segments from six male necropsiedcadavers: were obtained three young individuals between 16 and 35 years old and three aged individuals between 50 and 83 years old. The tunica media of the great saphenous vein at the upper third level of the thigh belonging to both young and aged individuals is made up of two layers: an internal formed by fascicles of smooth longitudinal muscular fibers and the external layer made up by fascicles of smooth circular muscular fibers. At the level of the discharge in the femoral, the tunica media of the great saphenous vein wall of both, young and aged individuals, is made up of one layer, whose fascicles of smooth muscular fibers are circularly orientated in relation to the vascular axis. The tunica adventitia of the great saphenous vein wall at the upper third level of the young individuals thigh, presents elastic fibers whereas it the aged individuals it is made up of fascicles of smooth longitudinal fibers; at the level of the femoral vein disdarge in both young and aged individuals, the tunica adventitia presents a fiber elastic constitution. The young and aged individuals' parietal venous valve is elastic fiber in nature. The young individuals' ostial valve is also elastic and that of aged individuals is muscular fiber in nature.

Functional and morphological evaluation of canine veins following preservation in different storage media.

Injuries of endothelial and smooth muscle cells of autologous vein due to preservation in standard storage media may be responsible for graft failure. The effects of vein preservation with University of Wisconsin solution (UWs) on endothelial and smooth muscle cell function and morphology were compared to the effects of preservation with autologous whole blood (AWB) and normal saline (NS), which are frequently used in cardiovascular surgery. Canine external jugular and common femoral vein segments were preserved in the different solutions at 4 degrees C for 45 min and 24 hr. Rings (4-5 mm in length) from control and preserved veins were evaluated by isometric tension studies at 37 degrees C and by scanning and transmission electron microscopy. Differences between groups were evaluated by Student's t test or Mann-Whitney U test and by analysis of the variance, and considered to be significant at P < 0.05. Sensitivities to norepinephrine (NE) showed that a 45-min vein storage in AWB (5.7 +/- 0.2 mumol/L) but not in NS (5.8 +/- 0.2 mumol/L) or UWs (6.5 +/- 0.2 mumol/L) had a deleterious effect on function of smooth muscle (P < 0.05) when compared to control veins (6.6 +/- 0.2 mumol/L). Maximum contractile responses and sensitivities to NE were significantly altered (P < 0.05) after 24-hr vein storage in AWB (0.09 +/- 0.02 g/mm2 and 5.4 +/- 0.07 mumol/L) and NS (0.12 +/- 0.03 g/mm2 and 5.6 +/- 0.08 mumol/L) but not in UWs (0.36 +/- 0.06 g/mm2 and 6.4 +/- 0.07 mumol/L). With both storage times, acetylcholine-induced endothelium-dependent maximum relaxations and sensitivities were significantly reduced (P < 0.05) in veins stored in AWB and NS, but not in UWs, compared with controls. Similarly, transmission electron microscopy revealed marked neutrophil migration beneath the intimal surface of vessels and extensive separation and desquamation of endothelial cells with exposure of subendothelial structures in veins stored in AWB and NS. The results suggest that UWs is a suitable storage medium when compared to AWB and NS.

Efeito de glicosaminoglicanos na prevençäo de trombose em enxertos veno-venosos microcirúrgicos no rato / Glycosaminoglicans in the prevention of thrombosis in veno-venous microsurgical grafts in the rat

Visando a contribuir para o desenvolvimento de métodos de prevençäo de trombose em enxertos veno-venosos realizados por técnica microcirúrgica, o presente trabalho teve por objetivo avaliar comparativamente o efeito da heparina, de uma heparina de baixo peso molecular (enoxaparina) e do sulfato de heparan na prevençäo do desenvolvimento de trombo nesses enxertos no rato, utilizando doses antitrombóticas determinadas em modelo de trombose de veia cava. Pretendeu-se também realizar estudo ultra-estrutural dos enxertos em que se pode, eventualmente, prevenir a formaçäo de trombos, visando verificar uma eventual diferença na açäo das drogas sobre a formaçäo dos mesmos e sobre o endotélio. No modelo de ligadura de veia cava, a heparina teve eficácia nas doses de 200 UI/kg EV e 400 UI/kg SC, a enoxaparina nas doses de 1,5 mg/kg EV e 2 mg/kg SC e o sulfato de heparan nas doses de 2,5 mg/kg EV e 15 mg/kg SC. Os animais foram divididos em 4 grupos de tratamento: grupo controle; grupo heparina, grupo enoxaparina e grupo sulfato de heparan. A heparina foi administrada por via intravenosa, em dose de 200 UI por kg, imediatamente antes do início do procedimento cirúrgico e, após 3 horas, complementada com doses de 400 UI por kg, por via subcutânea, de 12 em 12 horas. A enoxaparina foi administrada por via intravenosa, em dose de 1,5 mg por kg, imediatamente antes do início do procedimento cirúrgico e, após 3 horas, complementada com doses de 2,0 mg por kg, por via subcutânea, de 12 em 12 horas. O sulfato de heparan foi administrado por via intravenosa, em dose de 2,5 mg por kg, imediatamente antes do início do procedimento cirúrgico e, após 3 horas, complementada com doses de 15,0 mg por kg, por via subcutânea, de 12 em 12 horas. O enxerto veno-venoso foi realizado em 56 animais. A avaliaçäo desses enxertos foi realizada 15 minutos (16 ratos) e 48 horas (40 ratos) após a liberaçäo do fluxo sangüíneo. No grupo controle, verificou-se trombose oclusiva do enxerto venoso em 9 dos 10 animais. No grupo tratado com heparina, houve trombose oclusiva em 4 dos 10 animais. No grupo enoxaparina, a trombose oclusiva ocorreu em 9 dos 10, e no grupo sulfato de heparan, em 3 dos animais. Houve diferença significante quanto ao número de trombose oclusiva nos enxertos quando se comparam os animais dos grupos heparina e sulfato de heparan com os animais do grupo controle...

Healing of microvenous polytetrafluoroethylene (PTFE) prostheses implanted into the rat femoral vein by means of 3M precise.

Thirty PTFE prostheses (internal diameter, 1.0 mm; length, 5.0 mm; fibril length, 30 microns) were implanted into rats' femoral veins by means of a coupling device (3M precise microvascular anastomosis system, 3M, St Paul, MN) and evaluated with electron microscopy at regular intervals from 1 day to 3 weeks after implantation to study, in detail, the healing process. Eighty-three percent of mechanically anastomosed grafts were found to be patent. At 1 and 3 days after implantation, the whole length of PTFE was covered with a clot layer containing platelets and a fibrin network. After 1 week, endothelial-like cells originating from the anastomotic sides grew in across the anastomoses. At 3 weeks, the prostheses were completely covered by an endothelial-like cell layer. These results demonstrate that the degree of neo-endothelialization in the microvenous PTFE prosthesis anastomosed with 3M rings was not delayed, as was seen in the healing of microarterial PTFE tubing that was mechanically anastomosed.

Fresh venous allografts in peripheral arterial reconstruction in dogs. Effects of histocompatibility and of short-term immunosuppression with cyclosporine A and mycophenolate mofetil.

To date, no arterial substitute has been shown to be as effective as the autologous saphenous vein in peripheral revascularization procedures. In the present study, the venous allograft was evaluated as a vascular substitute in terms of patency and induction of host immune reactivity, whether used in major histocompatibility complex-incompatible, major histocompatibility complex-incompatible dogs. The immunosuppressive drug therapies were given for a period of 31 days, beginning 1 day before transplantation, and consisted of the use of cyclosporine A, mycophenolate mofetil, or a combination of both. All histoincompatible allografts were thrombosed at 4 or 8 weeks after transplantation with antibody development and cell-mediated cytotoxicity in the graft, whereas histocompatible allografts showed late stenosis without immunologic reactions directed toward donor cells. Given alone, neither cyclosporine A nor mycophenolate mofetil improved the overall patency of venous allografts; thrombosis occurred shortly after cessation of immunosuppression. Still, the cyclosporine A-mycophenolate mofetil combination therapy led to a 100% patency rate at 20 weeks after implantation and immune reactions were markedly reduced. This study shows that the fresh vein allograft is still an attractive and functional alternative to the autologous saphenous vein if the host immunologic reactions are controlled by cyclosporine A-mycophenolate mofetil immunosuppression.

The role of bone traumatization in the initiation of proximal deep vein thrombosis during cemented hip replacement surgery in pigs.

Hip arthroplasty is associated with a high frequency of postoperative solitary proximal deep vein thrombosis which seems most frequently observed when bone cement is used for prosthesis fixation. Eighteen pigs underwent hemiarthroplasty, eight with cement-fixed prostheses and eight with non-cement prosthesis installation. Levels of thrombin-antithrombin (TAT) complexes, tissue plasminogen activator (t-PA) activity and plasminogen activator inhibitor 1 (PAI-1) activity were determined in femoral vein blood from both limbs during and after surgery. On the operated side, TAT increased during bone traumatization followed by a substantial rise in t-PA activity and a gradual decline in PAI-1 activity. This indicates a local per- and post-operative sequential activation of coagulation and fibrinolysis followed by a fibrinolytic shutdown, all reflected in femoral vein blood on the operated side. In the animals receiving noncemented hip prostheses, the same pattern of activation of coagulation and fibrinolysis occurred on the operated side. This was, however, less marked than with the cement-fixed prostheses. Postoperative scanning electron microscopic (SEM) examination of the femoral veins showed thrombi on the operated side in 62% of the animals in the cement group and 25% in the non-cement group. In an additional study with eight animals undergoing cement-anchored hip prosthesis operations the levels of TAT, t-PA and PAI-I were analysed in femoral vein blood, mixed venous blood and arterial blood. Significantly higher levels were found in femoral vein blood compared with mixed venous blood while no significant change was found in arterial blood compared with mixed venous blood. The hyperthermia induced by curing bone cement was effectively conducted by the implanted prosthesis and did not seem to exert major influence on the activation of coagulation. Extreme rotation of the limbs during surgery did not in itself induce visible vein wall damage as judged by SEM. These studies indicate that traumatization of bone marrow during hip surgery induce a marked local activation of coagulation and a high incidence of deep vein thrombosis in proximal veins, in particular if bone cement is used for prosthesis fixation.

Differential vasodilatory action of 2-octynyladenosine (YT-146), an adenosine A2 receptor agonist, in the isolated rat femoral artery and vein.

The vasodilatory action of 2-octynyladenosine (YT-146), an adenosine A2 receptor agonist, was investigated in the isolated rat femoral artery and vein. Exposure to YT-146 resulted in preferential vasodilatation; the vein was completely dilated at YT-146 concentrations as low as 10(-7) M; in contrast, a concentration of YT-146 greater than 10(-4) M was necessary to induce complete relaxation in the femoral artery. 2-[p-(2-Carboxyethyl)-phenethylamine]-5'-N-ethylcarboxamidoadenosine (CGS 21680) also evoked stronger dilation in the vein than in the artery. The vasodilatory action of N6-cyclopentyladenosine (CPA) was much weaker in the vein than that of YT-146. YT-146-induced vasodilation in the artery was antagonized by neither 10(-7) M 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) nor 3 x 10(-6) M (E)-8-(3,4-dimethoxystylyl)-1,3-dipropyl-7-methylxanthine (KF17837), while the vasodilation in the vein was only antagonized by KF17837, suggesting that the vasodilation may involve adenosine A2 receptor activation in the vein. However, the present study did not provide evidence of a link between adenosine agonist-induced vasodilation and adenosine A2 receptor activation in the artery. The addition of 10(-4) M N omega-nitro-L-arginine partially reversed YT-146-induced vasodilation in the artery, but not in the vein. The reversal of YT-146-induced vasodilation by N omega-nitro-L-arginine in the artery was attenuated by the addition of 10(-3) M L-arginine. Removal of the endothelium decreased YT-146-induced vasodilation in the artery, but not in the vein.(ABSTRACT TRUNCATED AT 250 WORDS)

Continuous intravenous infusion in the unrestrained rat--procedures and results.

1. A method of continuous infusion in the unrestrained rat is described, which provides a scientifically acceptable and easily maintained rodent model for use in toxicological investigations. 2. Sprague Dawley SPF rats had cannulas implanted into the vena cava via the femoral vein, and were continuously infused with physiological saline for a total of 28 or 90 days. 3. The results indicate that there was no change in body weight, food consumption, clinical observations or clinical biochemistry of infused rats when compared to non-infused rats. There were small changes in haematological parameters, however none were toxicologically significant. Urinary volume was increased and urinary specific gravity and osmolality were decreased. At macroscopic and microscopic examination there were findings of scar formation associated with the area of surgery and minimal irritation in the area of the vena cava which accommodated the cannula. 4. These results indicate that implantation of a cannula into the vena cava of a rat and subsequent continuous intravenous infusion of physiological saline produces no toxicological adverse effects over a period of 90 days. Consequently, this model can be recommended for the continuous intravenous administration of test substances to rats.

Effects of cold storage on the subsequent structure and function of microvenous autografts.

A study was undertaken to evaluate the structure and patency of cold stored rabbit femoral veins following reinsertion as autografts for 3 weeks. The periods of cold ischaemic storage were 1, 2, 3 and 4 weeks (n = 10/gp) and 6 and 10 weeks (n = 6/gp). All rabbits were subject to 3 operations under general anaesthesia. In the first, a 4 cm segment of left femoral vein was harvested and stored at 4 degrees C for the specified ischaemic interval. Following storage the graft was microsurgically reinserted at a second operation into the right femoral artery of the donor rabbit. Three weeks later, graft patency was assessed by surgical exploration and the graft processed for light and electron microscopy. Patency rates remained over 80% after 3 weeks in all groups except the 10 week storage group where only 1 of 6 (17%) grafts was patent at 3 weeks. In all groups normal vein structure was absent, being replaced by thin walled necrotic areas or by neointimal ingrowth. The excellent patency rates achieved indicate it is possible to cold preserve extra lengths of vein grafts harvested at initial operation for reuse should regrafting be necessary.

[SEM image analysis of endothelial cells of autogenous vein grafts].

The autogenous veins of 17 dogs were distended with 40kPa, 80kPa and 120kPa pressure prior to grafting to femoral arteries respectively. The sections were harvested immediately, and after 1 week, 4 and 16 weeks and inspected with SEM. The endothelial cells of grafted veins were studied with an image analysis system. The results showed that the desquamation extent of intimal layer correlated positively with pressure. 80 and 120kPa caused relatively severe damage to the endothelium, which was significantly different from that of control group (P < 0.05). We conclude that preimplantation distention of vein grafts should be employed with less than 80kPa pressure, and 120kPa can never be used in clinic, as it adversely affects the course of reendotheli alization. The distention did not make a notable impact to graft patency rate as demonstrated in this experiment.

Healing of microvenous PTFE prostheses implanted into the rat femoral vein.

44 PTFE prostheses (Gore-Tex; ID 1 mm) were implanted into rats' femoral veins by means of the sleeve anastomotic technique and were evaluated at regular intervals from 1 h up till 24 weeks after implantation by means of light and electron microscopy to study in detail their healing process. All prostheses, except one at 1 week and one at 24 weeks after implantation, were patent at the time of removal. Upon implantation, the luminal surface of the prostheses became covered with a thin clot layer. From 1 week onwards, endothelial cells originating from the anastomotic sides grew in across the anastomoses. In addition, small capillary-like orifices were present at the anastomotic sites, from which endothelial cells also seemed to originate. At 2 weeks, in several areas in the mid-region of the prostheses, the fronts of regenerating endothelial cells had reached each other, and about 80% of the luminal surface was covered by endothelium and at 3 weeks, the prostheses were completely covered by an endothelial layer. These results demonstrate that PTFE microvenous prostheses heal exclusively by means of rapid ingrowth of endothelial cells originating from both sides at the anastomoses.

Comparison of laser-assisted fibrinogen-bonded and sutured canine arteriovenous anastomoses.

The effect of laser-assisted fibrinogen bonding (LAFB) on the development of intimal hyperplasia was studied with stress-strain profiles and histologic evaluation of canine arteriovenous fistulas (AVFs). In 19 animals femoral AVFs were created with an 808 nm diode laser after topical application of fibrinogen mixed with indocyanine green dye; in the contralateral limb a sutured AVF was created. The animals were divided into three groups. Group 1 dogs (n = 6) were killed serially up to 4 weeks after surgery to examine the healing of the anastomoses created with LAFB. Group 2 dogs (n = 6) were killed 1 month after surgery, and the fresh specimens were strained axially to produce a stress-strain profile graph. Group 3 dogs (n = 7) were killed 7 months after surgery, and the AVFs were infused with formalin under pressure and histologically prepared to allow comparison of the ratio of maximum to minimum intimal hypertrophy. Fibrinogen used for LAFB was resorbed during the first month after operation without evidence of foreign body reaction or inflammation. Tensile break force was not significantly different in the laser-bonded group (4.6 +/- 2.4 pounds) and the sutured group (4.3 +/- 1.7 pounds). The modulus (tensile break force per square inch), a measure of elasticity, identified the laser-bonded AVF (149 +/- 44 pounds per square inch) to be less rigid than the sutured AVF (203 +/- 35 pounds per square inch) (p less than 0.05). No significant differences in the degree of intimal hyperplasia were noted in any area of the anastomoses. Use of LAFB neither accelerates nor prevents intimal hyperplasia in a canine AVF model.(ABSTRACT TRUNCATED AT 250 WORDS)