Fibrin gel-immobilized VEGF and bFGF efficiently stimulate angiogenesis in the AV loop model.
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The modulation of angiogenic processes in matrices is of great interest in tissue engineering. We assessed the angiogenic effects of fibrin-immobilized VEGF and bFGF in an arteriovenous loop (AVL) model in 22 AVLs created between the femoral artery and vein in rats. The loops were placed in isolation chambers and were embedded in 500 microL fibrin gel (FG) (group A) or in 500 microL FG loaded with 0.1 ng/microL VEGF and 0.1 ng/microL bFGF (group B). After two and four weeks specimens were explanted and investigated using histological, morphometrical, and ultramorphological [scanning electron microscope (SEM) of vascular corrosion replicas] techniques. In both groups, the AVL induced formation of densely vascularized connective tissue with differentiated and functional vessels inside the fibrin matrix. VEGF and bFGF induced significantly higher absolute and relative vascular density and a faster resorption of the fibrin matrix. SEM analysis in both groups revealed characteristics of an immature vascular bed, with a higher vascular density in group B. VEGF and bFGF efficiently stimulated sprouting of blood vessels in the AVL model. The implantation of vascular carriers into given growth factor-loaded matrix volumes may eventually allow efficient generation of axially vascularized, tissue-engineered composites. (+info)
Evidence for a direct arteriovenous connection (A-V shunt) between the testicular artery and pampiniform plexus in the spermatic cord of the tree shrew (Tupaia glis).
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In the tree shrew Tupaia glis, 5 or 6 small ramifying arterioles arose directly from the testicular artery and then gave off numerous small capillaries. The capillaries made a series of anastomoses with neighbouring counterpart capillaries to become a complicated network. Some of the capillaries drained into a small venule, which was connected directly with the testicular vein (pampiniform plexus), to form an arteriovenous connection (A-V shunt) between the testicular artery and the pampiniform plexus. This A-V shunt appears to make the transfer of substances from the pampiniform plexus to the testicular artery more efficient. In addition, the shunt may control the volume of the blood draining into the testis. The capillaries were covered by vesiculated cells which were located adjacent to the pericytes. The vesiculated cells contained abundant mitochondria, rough endoplasmic reticulum, a well developed Golgi complex and cytoplasmic vesicles. Their cellular processes were long and surrounded more than one capillary. The morphological features of the vesiculated cells suggest that they may synthesise substances that are released into the network and which affect the activity of the capillaries. Since the cellular processes contacted each other, the cells could provide support for the capillaries and prevent their collapse when the shunts are closed. (+info)
Laser coagulation of placental anastomoses with a 30 degrees fetoscope in severe mid-trimester twin-twin transfusion syndrome with anterior placenta.
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Role of 5-HT1-like receptors in the reduction of porcine cranial arteriovenous anastomotic shunting by sumatriptan.
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1. The new tryptamine derivative sumatriptan (GR43175) is effective in the treatment of migraine. Since several antimigraine agents reduce cranial arteriovenous anastomotic blood flow in the anaesthetized pig, we have investigated the carotid haemodynamic effects of sumatriptan. 2. Sumatriptan (10, 30, 100 and 300 micrograms kg-1, i.v.) reduced total common carotid blood flow, exclusively by affecting its arteriovenous anastomotic fraction; the capillary fraction even increased with the highest doses. 3. These reductions in the carotid arteriovenous anastomotic ('shunt') blood flow were mediated by a 5-HT1-like receptor, as methiothepin, but not ketanserin, antagonized the responses to sumatriptan. 4. Sumatriptan increased the difference in oxygen saturation between arterial and jugular venous blood, which is likely to be a consequence of the reduction of the carotid shunt blood flow. 5. The selective reduction in arteriovenous anastomotic blood flow produced by sumatriptan may reflect its antimigraine action, thought to involve vasoconstriction of those cranial vessels, be they 'shunt' vessels or not, which are distended and inflamed during a migraine attack. (+info)
An endogenously deposited fibrin scaffold determines construct size in the surgically created arteriovenous loop chamber model of tissue engineering.
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