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Biomedical subjects

A Bylock

Publications and source records attributed to A Bylock.

31 records · Page 2Linked to original sources
PubMed1983

Local fibrinolytic activity and its structural basis in experimental gastric ulcers.

The stomach contains plasminogen activators localized to submucosal vessels and to the mucosa. To study the release of plasminogen activators from mucosal cells, we induced mucosal damage by pyloric ligature and instillation of 0.5 mol/l HCl in rats. After 4 h, all rats developed focal necrotic lesions and a diffuse mucosal damage, as studied both by light microscopy and by scanning electron microscopy. Diffuse mucosal damage was accompanied by significant increase (P less than 0.001) in mucosal fibrinolytic activity based on plasminogen activators. This activity was probably derived from injured mucosal cells since focal necrotic lesions (erosions and ulcers) with total denudation of the mucosal epithelium lacked fibrinolytic activity. The results obtained in this study support the hypothesis that plasminogen activators are released during cellular degeneration.

Animals↗
PubMed1983

The effect of balloon catheter trauma on surface ultrastructure and fibrinolytic activity in the caval vein in rats.

Surgical procedures in veins such as thrombectomy are followed by a high complication rate. Re-occlusion is not uncommon in spite of primarily successful thrombectomy. The venous endothelium is damaged by the thrombotic process and the mechanical trauma from the balloon will be additive. The endothelial cells are the source of fibrinolytic activators. The present study compared changes in fibrinolytic activity in the vessel walls from the caval veins in rats to ultrastructural changes as seen in the scanning electron microscope. The balloon caused an almost complete denudation of the intima and the lesions were fully covered with platelets 1 hour after trauma. After 3 days reendothelialization had started. The fibrinolytic activity was significantly decreased at 1 and 24 hours following trauma. Reendothelialization was accompanied by return to normal fibrinolytic activity.

Animals↗
PubMed1981

Early reactions of the arterial wall, following mechanical trauma. A scanning and transmission electron microscopy study.

Endothelial injury has for a long time been suggested to be an important factor for the development of atherosclerotic lesions. In this study, a superficial, circumferential, injury to the aortic intima was induced via a catheter covered with small stones, introduced into the femoral artery of rabbits. The immediate answer of the arterial wall and the formed elements of the blood was studied with combined scanning and transmission electron microscopy. De-endothelialization was noted and the denuded areas were almost immediately covered by platelets, spreading over the surface and releasing the contents of their granules by time. At some locations deeper injuries to the elastic laminae of the wall could be noted. Especially frequent around these areas, but also common all over the de-endothelialized surface, leukocytes were seen. Both neutrophils, lymphocytes and monocytes could be found. A demarcation of the border of the injury was noted three days after catheterization.

Animals↗
PubMed1981

Vascular trauma induced by clamping- correlation between surface ultrastructure and fibrinolytic activity.

The effects of application of a vascular clamp for 30 sec were studied on the femoral vessels in rats. Control and injured vessel segments were studied with scanning electron microscopy and with a histochemical method to estimate the fibrinolytic activity in the vessel walls. Endothelial injury with loss of endothelial cells was induced by application of the clamp. This was correlated to a reduction of the fibrinolytic activity in the vessel wall. In arteries re-endothelialization was seen three weeks after induction of the trauma, and it was completed after eight weeks. Venous lesions healed earlier. The re-endothelialization was followed by a return to normal fibrinolytic activity.

Animals↗
PubMed1980

Scanning electron microscopy - some methodological considerations.

Although scanning electron microscopy has been used in arterial research for more than a decade, methodological standards are still subject to dispute. In this presentation, our experience with different methods to prepare arterial tissue is described. Our efforts have been aiming at optimizing the reproducibility of our preparations. The recommended procedure involves fixation at "physiological" arterial pressure in Karnovsky's fixative for a short period, post-fixation by immersion, drying of the tissue with the critical point method and covering it with gold in a sputtering device. The effects of various deviations from this procedure are described. After preparation with the recommended procedure a resolution of 200-400 A has been obtained. General characteristics of the arterial endothelium are concurrent with those described in studies using light microscopy or transmission electron microscopy.

Animals↗
PubMed1979

Surface ultrastructure of human arteries with special reference to the effects of smoking.

The surface ultrastructure of uterine arteries from 20 women was studied with scanning electron microscopy. Specimens were excised and fixed under pressure shortely after removal of the uterus during hysterectomy. Two groups of patients were selected: non-smokers and women who smoked more than 15 cigarettes a day. The prevalence of seven different morphological criteria was evaluated without knowledge of the smoking habits of the patients. Endothelial cells were usually well demarcated and distributed with their length axis paralledl to that of the artery. The cell nucleus was revealed by a gentle bulging into the lumen, and cell borders by the presence of rows of microvilli. Inter- and intracellular holes alon the cell borders were more common in arteries from smokers, whereas microvillie were more common on the cell surfaces of arteries from non-smokers. These differences might be related to cell injury. Previous studies indicate that holes are more frequent in injured than in non-injured cells, whereas the surface of injured cells is often smoother than that of non-injured cells. Therefore, these data may be taken to suggest that smoking can lead to endothelial injury in man.

Adult↗
PubMed1978

Ultrastructural evidence for an innervation of epithelial enterochromaffine cells in the guinea pig duodenum.

The innervation of the duodenal enterochromaffine cells (E.C.) of the guinea pig was studied at the electronmicroscopic level. Pretreatment with 5-OH-dopamine was performed to visualize catecholaminergic (CA) nervous elements. Near the basement membrane of all examined E.C. in the crypts, bundles of unmyelinated nerve processes were observed, only partly ensheathed in a Schwann cell cover. At least 4 types of processes could be observed. 1) Boutons containing only small clear vesicles, probably cholinergic fibres; 2) boutons with small clear vesicles, and in addition large (greater than 200 nm) granules with a dense matrix (P-type-fibres); 3) boutons with small electron-dense vesicles, probably CA-fibres; and 4) processes with few vesicles but having the appearance of dendrites. No typical synaptic arrangements were observed, but the minimal distance between the E.C. and the nerve bundles was 150 to 250 nm, thus well within the functional limits of the "autonomic gap". Thus epithelial E.C. may be influenced by several types of nervous elements, including CA-fibres.

Adrenergic Fibers↗
PubMed1977

Endothelial structure in rabbits with moderate hypercholesterolaemia. A scanning electron microscopic study.

The aortic surface of rabbits given a supplement of 0.1--0.3 per cent cholesterol to the diet was studied by scanning electron microscopy. In regions where increased haemodynamic strain was anticipated, similar structural changes were observed in normal and hypercholesterolaemic rabbits. However, changes indicating cell injury were more wide-spread in cholesterolfed animals. This suggests that hypercholesterolaemia may increase cell susceptibility to injury. In the same regions, the development of intimal thickenings was observed in cholesterol-fed rabbits. The central parts of such thickenings had been reendothlialized, whereas a region with cell injury surrounded each lesion. In regions with low haemodynamic strain, a loss of fine-structural details was observed in hypercholesterolaemic rabbits. It is suggested that these changes may be related to the deteriorated functional properties of the intact endothelium in such rabbits. In view of these data it is suggested that the interrelationship between hypercholesterolaemia and atherosclerotic arterial disease may partly be due to a deleterious effect of hypercholesterolaemia on the functional and structural integrity of the arterial endothelium.

Animals↗
PubMedDate not supplied

A system for long-term perfusion of rabbit aorta in vitro.

In an in vitro system for the perfusion of arterial tissue, the volume of the incubation chamber should be small, and the composition of the medium should be easily modified. The tissue should consist of media and intima only, and the interaction with the medium should occur via the intimal side. Consecutive sampling of the medium and the tissue should be possible. This paper describes a system with these characteristics. Scanning and transmission electron microscopy of the perfused tissue indicated that the endothelium was intact during the first day and that it still covered more than 95% of the surface after 3 days. On the 2nd day, the nonthrombogenic properties of the endothelium were maintained. The medial smooth muscle cells of the inner two-thirds of the preparation were viable during the perfusion, while the cells in the outer one-third were dead from the start. Still, the metabolic activity of the tissue was stable, at least during the 2nd day as assessed by the study of DNA, protein, and lipid synthesis, as well as by oxygen consumption. We conclude that the perfusion system presented here might be useful in the study of the interaction between cellular and humoral components of the blood and the arterial wall.

Animals↗
PubMedDate not supplied

Endothelial fibrinolysis and ultrastructure following graded mechanical trauma.

For study of the progression and resolution of endothelial damage following mechanical vascular trauma in rats, the effects of a clamp with hydrostatically controlled occlusion pressure were compared with those of a standard mechanical clamp. The endothelial morphology was investigated with scanning electron microscopy and its function with histochemical analysis of plasminogen activator activity. Arterial or venous compression with hydrostatic pressure 1.5 kPa (11 mmHg) for 5 or 20 min produced de-endothelialized areas in veins, but only slight endothelial elevation in arteries. Hydrostatic occlusion of arteries with 12 kPa (90 mmHg) for 30 sec did not affect endothelial morphology and fibrinolytic activity, but after occlusion for 5 or 20 min the endothelium in both arteries and veins was severely damaged. The effects of hydrostatic (12 kPa) clamping on endothelial morphology and function after 5 or 20 min did not differ from those of mechanical (48 kPa = 360 mmHg) clamping. Apposition of vascular walls, except for the shortest time (30 sec) thus injured the endothelium, but minimizing occlusion pressure may reduce structural damage in the vessel wall.

Animals↗