We examined changes in the blood flow velocity of brain stem artery (BSA) and middle cerebral artery (MCA) in response to hypercapnic, normocapnic and hypocapnic hyperventilation in seven awake subjects with a transcranial Doppler to determine if there are differences in blood flow control in regional brain perfused by these respective arteries, and to separate the effects of CO2 and ventilation itself on blood flow velocity during CO2 loading. During hypercapnic hyperventilation, BSA flow velocity increased linearly with an increase in end-tidal partial pressure of CO2 (PETCO2). During hypocapnic hyperventilation, BSA flow velocity decreased linearly with decrease in PETCO2, but did not change during normocapnic hyperventilation. The mean CO2 reactivity of BSA was 2.8%/mmHg. The responses of MCA to these hyperventilations and CO2 reactivity were similar to those of BSA. These findings suggest that CO2 rather than ventilation per se is the important stimulus to changes in brain blood flow velocity and that the CO2 responses of brain arteries are not affected by differences in vascular beds.

Adult↗

PubMedDate not supplied

MR angiography of intracranial aneurysms: a comparison of 0.5 T and 1.5 T.

The objective of this paper is to compare the diagnostic efficacy of 3 DFT time-of-flight MR angiography (MRA) at middle-field-strength and high-field-strength in diagnosis of intracranial aneurysms. Thirty-one patients, including 26 patients with angiographically confirmed intracranial aneurysms (n = 28), underwent MRA at 0.5 and 1.5 T. Images were interpreted by six trained observers who were blinded to diagnosis. Twelve projections of MRA of the circle of Willis, by maximum-intensity projection algorithm, were reviewed using continuous confidence-judgement scales. It was found that MRA at 1.5 T was more sensitive than that at 0.5 T in detection of aneurysms. The sensitivity of six observers ranged between 50 and 64% (mean 56%) at 0.5 T, and between 61 and 86 86% (mean 75%) at 1.5 T. In the smaller aneurysms less than 5 mm, the differences between the units became greater. The sensitivity for small aneurysms ranged from 23 to 54% (mean 32%) at 0.5 T, and from 31 to 69% (mean 58%) at 1.5 T. Our conclusion was that high field strength confers higher accuracy in the detection of intracranial aneurysms with MRA with current-generation MR imagers.

Algorithms↗

PubMedDate not supplied

An artificial esophagus consisting of cultured human esophageal epithelial cells, polyglycolic acid mesh, and collagen.

Previously, the authors successfully grafted collagen sheets covered with cultured human esophageal epithelial cells onto latissimus dorsi muscles of athymic mice. To make a tubular artificial esophagus they developed a polyglycolic acid mesh-collagen complex tube whose inner side was epithelialized in vitro by cultured human esophageal epithelial cells. Human esophageal epithelial cells were isolated from normal mucosa resected from specimens of esophageal cancer patients and cultured on the surface of the collagen gel in which polyglycolic acid mesh was embedded. After the culture reached confluence, polyglycolic acid mesh was sutured to create a tubular form lined with cultured cell layers (restructured mucosal tube). Such tubes were wrapped in the latissimus dorsi muscle flaps of athymic rats using a fibrin glue. The animals were killed 4, 8, 20, and 28 days after grafting and the grafted tubes were studied histologically. Up to 28 days after grafting, the luminal structure was maintained without structure. Eight days after grafting, rat fibroblasts infiltrated from the muscle and neovascularization appeared in the collagen layer. The grafted epithelium remained healthy and grew to 15 cell layers by 20 days, much like normal human esophageal epithelium. Staining by anti-laminin monoclonal antibody confirmed a basement membrane.

Animals↗

PubMedDate not supplied

An artificial esophagus constructed of cultured human esophageal epithelial cells, fibroblasts, polyglycolic acid mesh, and collagen.

We have been developing an artificial esophagus constructed of autologous esophageal component cells by cell culture. Because human esophageal epithelial cells are stratified in 20 layers, we attempted to construct an artificial esophageal epithelium 20 twenty layers thick. In in vitro experiments, we investigated how keratinocyte growth factor produced by fibroblasts accelerates the proliferation and differentiation of epithelial cells. Esophageal epithelial cells were cultured on collagen sheets in which dermal fibroblasts (0, 1, 4, 8 x 10(5) cells/ml of collagen) were embedded. In cultured epithelial cells on collagen gels without fibroblasts, 2.1 layer stratification was observed on the 21st day. With 1 x 10(5) fibroblasts/ml of collagen, 3.0 layer stratification was observed, 5.0 layers with 4 x 10(5) fibroblasts, and 18.1 layers with 8 x 10(5) fibroblasts. The degree of epithelial cell stratification was thus correlated with the number of embedded fibroblasts. Tubes constructed of a polyglycolic acid mesh frame, a collagen layer with esophageal fibroblasts, and an inner layer of esophageal epithelial cells were transplanted into muscle flaps of athymic rats. The luminal structures were observed to be patent without stenosis for 14 days. Histology of the epithelium revealed 20 layers of stratification. We thus succeeded in constructing epithelium similar to human esophageal epithelium. In the future we will attempt to use the tubular structures as a substitute for the esophagus after esophagectomy.

Animals↗