Strain differences in neointimal hyperplasia in the rat.

We performed an initial screen of 11 rat strains by use of a standard balloon injury to the left iliac artery to observe whether genetically determined differences existed in the development of neointimal hyperplasia. Neointimal hyperplasia was assayed 8 weeks after the vascular injury on coded microscopic sections. Statistically significant differences in the percentages of the vascular wall cross-sectional areas composed of intima (percentage intima) secondary to neointimal hyperplasia were noted among the different rat strains (P<0.02), with the Brown-Norway (BN), Dark Agouti, and Milan normotensive strain rats having the highest and the spontaneously hypertensive rats (SHR) having the lowest percentages of intima. In a separate experiment, F1 hybrids of SHRxBN strains and parental BN and SHR underwent the vascular injury, and the parental strains again showed a statistically significant difference from one another in the mean percentage of intima (P<0. 0001). The F1 hybrids showed an average percentage of intima intermediate between those of the parental strains. The average lumen size of the injured BN vessels were significantly smaller than that of the noninjured control vessels (P=0.044), but this significance disappeared when the circular areas of these vessels were calculated without taking neointimal growth into consideration (P=0.649). These results provide the groundwork for a genetic linkage analysis to identify the genes that influence the development of neointimal hyperplasia after vascular injury.

Genome scan and congenic strains for blood pressure QTL using Dahl salt-sensitive rats.

An F2 population (n = 151) derived from Dahl salt-sensitive (S) and Lewis rats was raised on a 8% NaCl diet for 9 weeks and analyzed for blood pressure quantitative trait loci (QTL) by use of a whole genome scan. Chromosomes 5 and 10 yielded lod scores for linkage to blood pressure that were significant; chromosomes 1, 2, 3, 8, 16, 17, and 18 gave lod scores suggestive for linkage. Chromosome 7 gave a significant signal for heart weight with a lesser effect on blood pressure. Congenic strains were constructed by introgressing Lewis low-blood-pressure QTL alleles for chromosomes 1, 5, 10, and 17 into the S genetic background. Congenic strains for chromosomes 1, 5, and 10 had significantly lower blood pressure than S, proving the existence of QTL on these chromosomes, but the chromosome 17 congenic strain failed to trap a contrasting QTL allele. The QTL allele increasing blood pressure originated from S rats for all QTL except those on chromosomes 2 and 7 in which the Lewis allele increased blood pressure. Interactions between each QTL and every other locus in the genome scan yielded significant interactions between chromosomes 10 and 4, and between chromosomes 2 and 3.

Biplane color flow duplex intravenous intravascular ultrasound for arterial visualization.

PURPOSE: To describe a feasibility study in a sheep model using an intravascular ultrasound (IVUS) instrument in an intravenous position to produce color flow, B-mode images of arterial segments along with Doppler blood flow velocities. METHODS: Four healthy adult male sheep were anesthetized for surgical exposure of the right external jugular vein. A 9.0F sheath was also introduced in the common femoral artery for arteriography and device insertion. A 7.5-MHz ultrasound probe with 1-cm graduation markers was passed into the jugular vein. B-mode and color flow pictures were captured at aortic branches in cross and longitudinal sections. Length measurements between aortic branches and Doppler spectral velocities were obtained. Guidewire, balloon, and stent maneuvers were monitored by the stationary intravenous IVUS probe. RESULTS: High-quality visualization of the entire abdominal aorta and its branches was achieved in all animals. With the probe stationary in the vena cava, a 1.5-cm linear segment of the aorta could be continuously observed in both B-mode and color flow ultrasound scans. Insertion and implantation of a Palmaz balloon-expandable stent was guided by intravenous IVUS alone. Selective catheterization of the right renal artery was followed visually by moving the intravenous IVUS probe sequentially. CONCLUSIONS: Intravenous IVUS appears feasible as a guidance and monitoring tool for endovascular interventions. While conventional IVUS provides only cross-sectional images in B-mode, intravenous IVUS captures color flow and Doppler velocity data as well. These added ultrasound modalities may offer potential advantages for guidance of endovascular procedures and endoleak detection.