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  • 1
    ISSN: 1436-2813
    Keywords: pseudointimal hyperplasia ; fibril length ; PTFE ; animal model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In addition to the polytetrafluoroethylene (PTFE) vascular graft (G) with its conventionally smooth surface, a unique PTFE graft with a ridged outer wall (T) is now also currently available for clinical use. Although an excellent antikinking property is provided by this unique outer structure, the possible influence of the structure on the formation of pseudointima has not yet been investigated in detail. Four kinds of T grafts (3 mm inner diameter, 3 cm long) with various fibril lengths (FL, T-15, T-30, T-60, T-90) and a G graft with 30 μm FL (G-30) were implanted into the inferior vena cava of rabbits. The patency of the grafts at 4 weeks were as follows: 6/8(T-15), 6/8(T-30), 5/8(T-60), 0/8(T-90) and 4/6 (G-30). Pseudointimal hyperplasia (PH) of the T grafts advanced as the FL increased, judging by the thickness of the pseudointima, cellular density, and maturity of fibroblasts. In addition, the maturity of endothelial-like cells on the luminal surface increased as the FL increased. The degree of pseudomintimal hyperplasia in G-30 was comparable to that of T-15, although the maturity of the endothelial-like cells was similar to that of T-60. Microscopically, there was a microheterogeneity of cellular density in T grafts probably due to the uneven outer structure. In conclusion, not only FL but also the outer structure of PTFE may thus influence the formation of the pseudointima.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1436-2813
    Keywords: prostacyclin analogue ; pseudointimal hyperplasia ; venous prosthesis ; animal model ; smooth muscle cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of this study was to evaluate the effect of a novel prostaglandin I2 analogue, beraprost (BPT), on the pseudointimal hyperplasia (PIH) of polytetrafluoroethylene (PTFE) prostheses. A total of 12 rabbits were equally divided into three groups. The control group was given a placebo daily, group 1 was given BPT orally 2 mg/kg per day, and group 2 was given BPT orally 4 mg/kg b.i.d. Exactly 1 cm of the inferior vena cava was resected and replaced by a 3-cm PTFE tube graft. All the grafts were patent when harvested 4 weeks after implantation, but the lumens were narrowed to various extents by PIH. PIH, determined by the dry weight of the intraluminal tissue deposit, was significantly (P〈0.01) suppressed in groups 1 and 2 compared with the control group. High-magnification light microscopy with various staining methods revealed the PIH to be composed mainly of smooth muscle cells (SMCs) and collagen fibrils in all three groups. Transmission electron microscopy revealed that the majority of SMCs in groups 1 and 2 were contractile in form, in contrast with the synthetic form seen in the control group. In conclusion, BPT attenuated the PIH of PTFE grafts by inhibiting the phenotype change in the SMCs.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1433-0350
    Keywords: Key words Quantitative measurement ; CSF flow dynamic ; Phase-contrast cine MR ; Hydrocephalus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  This investigation was undertaken to characterize CSF flow at the level of the aqueduct of Sylvius with a phase-contrast cine MR pulse sequence in 28 healthy volunteers. Sixteen patients with obstructive hydrocephalus and 11 patients with normal pressure hydrocephalus (NPH) were investigated with the same sequence before and after CSF diversion. The peak CSF flow velocity and stroke volume in the aqueduct increased significantly in the NPH group and decreased significantly in the obstructive hydrocephalus group. After lumboperitoneal shunting in the NPH group, the retrograde flow of CSF was anterogradely converted and the peak flow velocities decreased somewhat. The clinical diagnosis of NPH was well correlated with the results of cine MRI. After endoscopic III ventriculostomy in the obstructive hydrocephalus group we noted increased CSF flow velocity with markedly increased stroke volume at the prepontine cistern. Phase-contrast cine MR is useful in evaluating CSF dynamics in patients with hyperdynamic aqueductal CSF or aqueductal obstruction.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1619-7089
    Keywords: Key words: Autism ; Brain ; Technetium-99m ethyl cysteinate dimer ; Single-photon emission tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The neuro-anatomical substrate of autism has been the subject of detailed investigation. Because previous studies have not demonstrated consistent and specific neuro-imaging findings in autism and most such studies have been performed in adults and school-aged children, we performed a retrospective review in young children in search of common functional and anatomical abnormalities with brain single-photon emission tomography (SPET) using technetium-99m ethyl cysteinate dimer (ECD) and correlative magnetic resonance imaging (MRI). The patient population was composed of 23 children aged 28–92 months (mean: 54 months) who met the diagnostic criteria of autism as defined in the DSM-IV and CARS. Brain SPET was performed after intravenous injection of 185–370 MBq of 99mTc-ECD using a brain-dedicated annular crystal gamma camera. MRI was performed in all patients, including T1, T2 axial and T1 sagittal sequences. SPET data were assessed visually. Twenty patients had abnormal SPET scans revealing focal areas of decreased perfusion. Decreased perfusion of the cerebellar hemisphere (20/23), thalami (19/23), basal ganglia (5/23) and posterior parietal (10/23) and temporal (7/23) areas were noted on brain SPET. By contrast all patients had normal MRI findings without evidence of abnormalities of the cerebellar vermis, cerebellar hemisphere, thalami, basal ganglia or parietotemporal cortex. In conclusion, extensive perfusion impairments involving the cerebellum, thalami and parietal cortex were found in this study. SPET may be more sensitive in reflecting the pathophysiology of autism than MRI. However, further studies are necessary to determine the significance of thalamic and parietal perfusion impairment in autism.
    Type of Medium: Electronic Resource
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