Browsing by keyword "Subtraction Technique"
Now showing items 1-3 of 3
-
Magnetic resonance imaging of tissue and vascular layers in the cat retinaPURPOSE: To report the visual resolution of multiple cell and vascular "layers" in the cat retina using MRI. MATERIALS AND METHODS: T2- and diffusion-weighted MRI at 4.7 Tesla was performed. Layer-specific thickness, T2, spin density, apparent diffusion coefficient perpendicular (ADC(perpendicular)) and parallel (ADC(parallel)) to the retinal surface were tabulated. T1-weighted MRI was acquired before and after intravenous administration of Gd-DTPA and subtraction images were obtained. Histology was performed for validation. RESULTS: Three distinct "layers" were observed. The inner strip nearest to the vitreous (exhibiting large T2, ADC, spin density with Gd-DTPA enhancement) overlapped the ganglion cell layer, bipolar cell layer, and the embedded retinal vascular layer. The middle strip (exhibiting small T2, ADC, spin density without Gd-DTPA enhancement) overlapped the photoreceptor cell layer and the inner and outer segments. The outer strip (exhibiting large T2, ADC, spin density with Gd-DTPA enhancement) overlapped the tapetum and choroidal vascular layer. T2, spin density, ADC(perpendicular) and ADC(parallel) of different "layers" were tabulated. The inner strip was slightly thicker than the other two strips. The total thickness, including neural and nonneural retina, was 358 +/- 13 microm (N = 6) by MRI and 319 +/- 77 microm (N = 5) by histology. CONCLUSION: MRI provides a noninvasive tool to study the retina with laminar specificity without depth limitation.
-
Profound misregulation of muscle-specific gene expression in facioscapulohumeral muscular dystrophyFacioscapulohumeral muscular dystrophy (FSHD) is a neuromuscular disorder characterized by an insidious onset and progressive course. The disease has a frequency of about 1 in 20,000 and is transmitted in an autosomal dominant fashion with almost complete penetrance. Deletion of an integral number of tandemly arrayed 3.3-kb repeat units (D4Z4) on chromosome 4q35 is associated with FSHD but otherwise the molecular basis of the disease and its pathophysiology remain obscure. Comparison of mRNA populations between appropriate cell types can facilitate identification of genes relevant to a particular biological or pathological process. In this report, we have compared mRNA populations of FSHD and normal muscle. Unexpectedly, the dystrophic muscle displayed profound alterations in gene expression characterized by severe underexpression or overexpression of specific mRNAs. Intriguingly, many of the deregulated mRNAs are muscle specific. Our results suggest that a global misregulation of gene expression is the underlying basis for FSHD, distinguishing it from other forms of muscular dystrophy. The experimental approach used here is applicable to any genetic disorder whose pathogenic mechanism is incompletely understood.
-
Selective embolization and clot dissolution with tPA in the internal carotid artery circulation of the rabbitWe describe a model of thromboembolic stroke in rabbits that utilizes the Seldinger technique and digital arteriography. The internal carotid arteries of 14 rabbits were catheterized selectively and embolized with autologous blood clots. After embolization, eight rabbits received IV tissue plasminogen activator (tPA); the remaining six were infused with saline and served as controls. After embolization, cerebral arteriograms were obtained at 30-min intervals for 180 min. Cerebral arteriograms obtained after tPA therapy revealed partial or complete thrombus dissolution in seven (88%) of the eight treated rabbits. In the control group, none of the arteriograms of the embolized internal carotid arteries showed thrombus dissolution. In the tPA-treated group, the median time for thrombus dissolution was 60 min. This stroke model is economical, reproducible, and less traumatic to the brain than most of the previously described animal models. It also provides a means to compare the safety and efficacy of various thrombolytic agents in small animals.