Enhanced intimal thickening of expanded polytetrafluoroethylene grafts coated with fibrin or fibrin-releasing vascular endothelial growth factor in the pig carotid artery interposition model.

OBJECTIVE: Intimal hyperplasia and surface thrombogenicity are major factors in the high failure rate of synthetic small-diameter bypass grafts. Vascular endothelial growth factor is a potent stimulus for endothelial growth, and its provision in a fibrin matrix coating at the luminal graft surface may hold a key to spontaneous graft endothelialization and improved graft patency. METHODS: Pigs underwent bilateral carotid artery interposition of expanded polytetrafluoroethylene grafts either impregnated with fibrin (n = 11)--engineered to locally release vascular endothelial growth factor121 (vascular endothelial growth factor-fibrin; n = 11)--or left uncoated (n = 12). Graft patency was assessed by quantitative carotid angiography followed by graft histomorphometry at the 1-month experimental end point. RESULTS: Patency rates were not significantly different between study groups. Grafts coated with fibrin or vascular endothelial growth factor-fibrin exhibited significantly increased angiographic narrowing at the proximal anastomosis (for both P < .05 vs uncoated) and no difference at the distal anastomosis and the grafts' middle. Histological analysis showed 80% to 90% endothelial coverage and buildup of intima throughout the lengths of all grafts. Examination of the grafts' midportion revealed significantly enlarged neointimal layers of smooth muscle actin-positive cells in grafts coated with vascular endothelial growth factor-fibrin (242 +/- 47 microm2/micron) and fibrin (177 +/- 41 microm2/micron), compared with uncoated grafts (131 +/- 39 microm2/micron) (for both P < .05 vs uncoated). This thickening could not be explained by enhanced inflammation or vessel wall angiogenesis, which were minimal at the experimental end point. CONCLUSIONS: Fibrin and vascular endothelial growth factor produced effects deleterious to graft healing, by increasing the narrowing at proximal anastomosis and neointimal growth beyond that seen in uncoated grafts. It may reflect direct activation by exogenous vascular endothelial growth factor of vascular smooth muscle cells.

Pre-clinical validation of a new intra-operative "dual beam Doppler" blood flowmeter in an artificial circuit.

BACKGROUND: Intra-operative flow measurement during coronary or peripheral bypass operations is helpful for ruling out technical failures and for prediction of complication and patency rates. Preclinical validation of the flowmeters is required in order to rely on the intra-operatively measured results. The aim of this study is to evaluate a new "dual beam Doppler" blood flowmeter before clinical application and to compare it with the established "transit time flow measure-ment" technique in an artificial circuit. METHODS: Measurements were performed in an experimental flow model using pig blood and pig arteries. Three different flowmeters were used: Quantix OR (dual beam doppler flowmeter), CardioMed (transit time flowmeter), and Transonic (transit time flowmeter). Three validation tests were performed to assess correlation, precision, and repeatability of devices. (1) Correlation and agreement analysis was performed with various flow amounts (10-350 mL/min) (n = 160). (2) Device reproducibility and measurement stability were tested with a constant flow (flow amount = 300 mL/min) (n = 30). (3) A user accuracy test (intra- and inter-observer variability) was performed by 5 different observers with a constant flow (flow amount = 205 mL/min) (n = 75). Time collected true flow was used as a reference method in all steps and all tests were performed in a blind manner. Results are shown as mean values +/- standard deviations. Pear-son's correlation and Bland-Altman plot analyses were used to compare measurements. RESULTS: The mean flow was 167 +/- 98 mL/min for true flow and 162 +/- 94 mL/min, 165 +/- 94 mL/min, and 166 +/- 100 mL/min for Quantix OR, CardioMed, and Transonic, respectively. Correlation coefficients between Quantix OR, Medi-Stim, Transonic, and time collected true flow were over 0.98 (P = .01). Most of the measured results ( > 90%) were between +/- 1.96 SD agreement limits in Bland and Altman plot analysis. All devices showed good results in the reproducibility test. During the user accuracy test, larger variance changes were observed between intra- and inter-observer results with the dual beam Doppler flowmeter compared to the 2 used transit time flowmeters when used for single sided vessel access without stabilization device (available from the manufacturer). CONCLUSION: All 3 tested flowmeters showed an excellent correlation to the true flow in an artificial circuit and the accuracy of the tested devices was within agreement limits. Reproducibility of all devices was good and linear. The new dual beam Doppler flow measurement technique compares favorably to the classic transit time method. Clinical use may depend on operator, location, and condition, thus more studies may be required to ensure uniform results using the currently available blood flow measurement devices.

Allopregnanolone and progesterone decrease cell death and cognitive deficits after a contusion of the rat pre-frontal cortex.

We compared the effects of three different doses of allopregnanolone (4, 8 or 16 mg/kg), a metabolite of progesterone, to progesterone (16 mg/kg) in adult rats with controlled cortical impact to the pre-frontal cortex. Injections were given 1 h, 6 h and every day for 5 consecutive days after the injury. One day after injury, both progesterone-treated (16 mg/kg) and allopregnanolone (8 or 16 mg/kg)-treated rats showed less caspase-3 activity, and rats treated with allopregnanolone (16 mg/kg) showed less DNA fragmentation in the lesion area, indicating reduced apoptosis. Nineteen days after the injury, rats treated with progesterone and allopregnanolone (8 or 16 mg/kg) showed no difference in necrotic cavity size but had less cell loss in the medio-dorsal nucleus of the thalamus and less learning and memory impairments compared with the injured vehicle-treated rats. On that same day the injured rats treated with progesterone showed more weight gain compared with the injured rats treated with the vehicle. These results can be taken to show that progesterone and allopregnanolone have similar neuroprotective effects after traumatic brain injury, but allopregnanolone appears to be more potent than progesterone in facilitating CNS repair.

Molecular events involved in neuronal death induced in the mouse hippocampus by in-vivo injection of kainic acid.

Apoptosis results from the activation of a programmed cellular cascade involving several mechanisms. In the present study, we have investigated the implication of three molecules of this cascade, p53, Bax and caspase-3, in neuronal death induced by kainic acid (KA) administration in mouse hippocampus. Using immunocytochemistry, western blot and quantification of enzyme activity, we observed in p53+/+ and p53-/- animals that KA induced neuronal death by both p53-dependent and independent pathways. Moreover, apoptosis (labeled by TUNEL) and the increase of bax and caspase-3 protein expression after the neurotoxic insult appeared to clearly depend on p53 expression.

p53 and Bax implication in NMDA induced-apoptosis in mouse hippocampus.

Seven days after in vivo intrahippocampal administration of NMDA, 3'-OH DNA fragmentations and Bax protein expression were detected in hippocampal neurons of p53+/+ but not p53-/- transgenic mice. Interestingly, neurons showing pycnosis, an early apoptotic phenomena, were present in all genotypes. These results confirm that apoptotic 3'OH DNA fragmentations and Bax protein induction during NMDA-induced apoptosis in adult hippocampal neurons are p53 dependent.