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Biomedical subjects

J C Geer

Publications and source records attributed to J C Geer.

At least 37 records · Page 2Linked to original sources
PubMed1976

Intimal changes in arteriovenous bypass grafts. Effects of varying the angle of implantation at the proximal anastomosis and of producing stenosis in the distal runoff artery.

Autologous arteriovenous bypass grafts were constructed between external iliac arteries in 20 mongrel dogs to determine the development of intimal fibromuscular hyperplasia. Animals received grafts at 55, 90 or 120 degree angles relative to the proximal anastomosis. Five animals with 90 degree angle grafts were also subjected to 80% stenosis in the runoff artery. All grafts showed the development of a fibromuscular tunica intima. Qualitative or quantitative intimal differences were not observed among grafts placed at 90 degree angles, 90 degree angles with runoff artery stenosis, or 120 degree angles. Grafts placed at 55 degree angles relative to the proximal anastomosis developed a consistently thicker fibromuscular layer in the tunica intima when compared to the other groups. These changes which were segmental in nature, occurred in the proximal and distal grafts and over the distal anastomosis.

Animals↗
PubMed1975

Pathology of atherosclerotic heart disease in sudden death. I. Organizing thrombosis and acute coronary vessel lesions.

The significance of organizing thrombosis was investigated in 121 cases of sudden death with atherosclerotic heart disease. Organizing thrombosis was observed in one-third of the cases, and sites at which it was present showed a higher prevalence of acute lesions -- thrombus, plaque rupture, and hemorrhage -- than sites at which it was not present. Acute and subacute coronary lesions were almost entirely restricted to vessels with 75% or greater obstruction. Evidence was presented suggesting that the organization of thrombosis in the coronary arteries was a more extended process than that observed in peripheral arteries.

Autopsy↗
PubMed1975

Pathology of atherosclerotic heart disease in sudden death. II. The significance of myocardial infarction.

The role of myocardial infarction was investigated in 121 cases of sudden death with atherosclerotic heart disease. In addition to supporting other reports which have demonstrated the importance of chronic occlusion of the coronary vessels in relation to the high rate of infarctions found in such cases, the authors presented evidence which showed differences in occurrence in the sites of remote and recent infarctions, a lack of concordance between the sites of recent infarctions, and acute thrombosis in coronary vessels proximal to these lesions. No relationship between patient age or prior symptoms could be associated with the occurrence of infarction. Evidence was also presented which discounted the possible role of transmural infarction in the formation of acute thrombosis. These pathological observations support the concept that sudden cardiac deaths are results of functional instability of the myocardium produced by advanced coronary atherosclerosis.

Adolescent↗
PubMed1974

Experimental aortic intimal thickening. I. Morphology and source of intimal cells.

Repair to injury of the rabbit aorta was studied with special attention to the source of new intimal cells. Two types of injury, suture placement and electrocautery, were used to ascertain whether the type of injury significantly modifies the reparative response of the artery. Cell morphology and DNA synthesis, as determined by autoradiographic localization of tritiated thymidine uptake, were studied sequentially during the course of the repair reaction. Suture injury was the more reliable model for these studies because the magnitude of injury was quite comparable between animals, while with cauterization there was considerable variation in the magnitude of injury. The overall reparative response with the two types of injury was, however, similar. Cell division was first seen in the media adjacent to the injured focus and was followed by migration of medial cells into the intima. In the intima, medial cells continued to divide for a few days and then gradually matured from undifferentiated ovoid cells resembling monocytes to morphologically differentiated smooth muscle cells. Medial cells exhibiting DNA synthesis were both differentiated and undifferentiated smooth muscle cells, supporting previous reports that mature as well as undifferentiated smooth muscle cells are capable of mitosis. However, with injury and repair, the migrating cells appeared to be mainly undifferentiated since there was a predominance of these cells early in the repair reaction in the intima.

Animals↗
PubMed1974

Experimental aortic intimal thickening. II. Endothelialization and permeability.

Experimental aortic intimal thickening has been induced in rabbits by two types of injury, suture placement and electrocautery. Scanning electron microscopy showed that endothelialization of the suture plaque was completed at about 10 days following injury. New endothelial cells had no particular orientation or were oriented at right angles to the adjacent normal aortic endothelium. Realignment parallel with the aortic axis had occurred by 21 days after induction of the lesion. Orientation patterns of new endothelial cells over irregularly shaped cautery-induced intimal thickening were difficult to ascertain. Aortic permeability studies were accomplished by using the tracers horseradish peroxidase (HRP) and ferritin. Several naturally occurring intimal thickenings in normal aortas had greater permeability for HRP than did adjacent normal intima. An enhanced penetration of both tracers was observed in mature intimal lesions produced by both experimental procedures compared to adjacent morphologically normal aortic intima. HRP molecules entered the thickened aortic intima in increased amounts through interendothelial junctions and by endothelial pinocytotic vesicles; ferritin molecules were seen only in pinocytotic vesicles. Increased penetration of HRP was observed for as long as 27 weeks after injury, while that of ferritin was observed only for 3 weeks. The enhanced permeability of the thickened intima as compared to normal for these two tracers of considerably different sizes strongly suggests an increased permeability of endothelium overlying intimal thickening for naturally circulating macromolecules.

Animals↗
PubMed1973

Surface areas of naturally occurring lipid classes and the quantitative microdetermination of lipids.

The surface area (A) of a lipid was directly proportional to the amount of lipid in a surface film (A = k micro moles) measured at constant surface pressure, temperature, and subphase composition. A surface area of 2300 cm(2)/ micro mole was obtained for cholesterol isolated from human adrenal and aorta and for cholesterol from hydrolysates of cholesteryl esters isolated from the same tissues. Unsaturated methyl esters that contained from one to four cis double bonds had the same surface area, 39.4 A(2)/molecule. As a consequence, naturally occurring triglyceride mixtures which had similar saturated-unsaturated fatty acid ratios had the same surface area, 6090 cm(2)/ micro mole. Naturally occurring phospholipid mixtures had the same surface area, 4590 cm(2)/ micro mole, and it appeared that the composition of these mixtures was regulated to control the physical properties of the mixtures. Surface area was much more sensitive than colorimetric procedures for the estimation of cholesterol and triglycerides. The surface area/molecule was a criterion of purity and an expanded surface area/molecule was an indication of autoxidation. Thus, surface area measurements were valuable for both the microdetermination and the characterization of lipid classes.

Cholesterol↗