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To determine the time-course of morphological changes after excimer laser treatment of atherosclerotic carotid arteries, laser angioplasty was performed in 34 rabbits after production of an intimal plaque (13 +/- 6 cell layers, 30 +/- 9% stenosis) using electrical stimulations. The animals were sacrificed 3, 7, 14, 21, 28, and 42 days after laser treatment. A total or subtotal thrombotic occlusion was found in four cases. No perforation was observed, but in 10 animals histological examination evidenced a partial ablation of the medial layer with signs of local thrombus formation and local reduction of SMC in the media. In five animals a stenosis of more than 50% of luminal reduction was due to intimal proliferation of smooth muscle cells (SMC), as determined by a monoclonal antibody against alpha-actin. After the initial ablation, a continuous increase of intimal cell layers was found, from 7 +/- 6 cell layers (19 +/- 9% stenosis) at 7 days, to 28 +/- 5 cell layers (45 +/- 18% stenosis) at 28 days following excimer laser angioplasty (p less than 0.01). After 42 days no additional increase of intimal thickening occurred. Our data suggest that incidence and morphology is comparable to the proliferative response of SMC following conventional balloon angioplasty.

Feeding animals a diet of increased cholesterol content gave rise to the feeding hypothesis, and balloon experiments were the basis of the injury hypothesis of atherogenesis. When analyzing the sequence of events in arterial walls during atherogenesis, it turned out that in spite of complex causes and courses of stenosing processes in arterial walls the final results were relatively uniform: atheromas of fibromuscular proliferates or a mixture of both develop. Calcification of the thickenings of arterial walls occurs frequently in the progression of the disease. In animal experiments, the development of arteriosclerosis can be speeded up with various experimental techniques and enables study of the action of drugs to inhibit atherogenesis, as well as therapies for restenoses which frequently occur after angioplasty or bypass operations. In studies of drug effects the limitations of animal experiments become obvious when trying to transfer results obtained in animal experiments to the situation in humans. Cultures of cells from human arteries are, therefore, necessary supplements. Mass cultures and clone cultures of arterial walls are, however, very artificial systems. Therefore, co-cultures of endothelial cells, smooth muscle cells, and adventitial tissue have been established which imitate the morphology of arterial walls. With transfilter co-cultures, it has become possible to produce fibromuscular proliferates in vitro. When oxidized LDL-particles and monocytes are added to the culture medium, lipid-containing proliferates develop.

It is little known that photosensitizing porphyrins can be used not only for the localization and photodynamic therapy of tumors, but that they also accumulate in atherosclerotic plaques. This observation might be of interest for the detection and therapy of vascular stenoses. The present study examines whether dihematoporphyrin-ester and -ether, at clinically relevant concentrations, selectively influence cultured smooth muscle cells from human atherosclerotic plaques (primary stenoses and secondary stenoses) in comparison to smooth muscle cells obtained from non-atherosclerotic arteries. The results demonstrate that the drug accumulated to a greater extent in plaque-derived cells than in smooth muscle cells from normal arteries. Even without photoactivation, dihematoporphyrin-ester and -ether significantly decreased the proliferative activity of cells from atherosclerotic plaques. Light exposure of porphyrin-labeled cells resulted in a more pronounced sensitivity of plaque cells when compared with smooth muscle cells from non-atherosclerotic arterial wall. A comparison of the proliferative activity of cells before and after photodynamic reaction demonstrated that this activity was unaltered in surviving smooth muscle cells from non-atherosclerotic arteries, whereas surviving plaque-derived cells exhibited a significantly decreased or even non-proliferative activity. From the in vitro studies, a porphyrin concentration of 1-5 micrograms/ml (= 1-5 mg/kg body weight in vivo after systemic application) seems to be the most suitable dosage. In addition, morphological alterations of the cells caused by photodynamic reaction were documented.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of extracellular glucose on isometric concentrations induced by acetylcholine was investigated under aerobic conditions in rat portal veins. In order to estimate the contractile potency of acetylcholine (ACh), dose-response curves of ACh and nor-epinephrine (NE) were compared. Simultaneously with the mechanical activity, changes in the redox states of pyridine nucleotides (PN) and flavoproteins were detected by a surface-fluorimetric method. Tissue concentrations of glucose, lactate, pyruvate, and ATP were determined parallel to ACh-induced contractions at corresponding intervals. In response to ACh-induced contractions, PN and flavoproteins were oxidized in vessels supplied with glucose. Following 6 h of glucose withdrawal, a small reduction or no change in the redox state was observed; ACh-induced contractions and tissue concentrations of glucose, lactate, pyruvate, and ATP were decreased. When glucose was added, the contraction force was restituted, and the tissue concentrations of glucose, lactate and PN were increased again. The ATP concentration remained decreased. The results suggest that isometric contractions of portal veins are significantly influenced by aerobic glycolysis. A direct effect of glucose on the excitability of vascular smooth muscle is discussed.

In the common carotid artery of rabbits, intimal myocyte proliferations were induced by daily repeated local electrical stimulation of the vessel wall in combination with a cholesterol containing diet given for 4 weeks. Some biochemical parameters of the morphologically modified intimal smooth muscle cells were studied and compared with those of samples obtained from nonstimulated tunica media of the contralateral carotid artery. The results show that in relation to dry weight both alkali extractable protein and DNA content of the proliferates are increased to about 125%. In the proliferates, the in-vivo tissue concentrations of glucose and glycogen are only 50-70% of the normal values, whereas the concentration of lactate is increased to about 160%. In-vitro incubation experiments of excised tissues samples from the intimal proliferates and normal media indicate that under an optimal supply of substrates the glucose uptake and lactate production of the proliferates are increased to 140% and 150%, respectively. This results provides evidence for an increased capacity of glycolysis in the proliferates, which in vivo may lead to a decrease in glucose concentration and to an increased concentration of lactate. This investigation shows that modified smooth muscle cells proliferating in the arterial intima exhibit an activated metabolism as seen in other models of arteriosclerosis.

Local and generalized decreases in cerebral circulation most frequently cause severe functional and morphological disturbances in the central nervous system. During a generalized cerebral ischemia, the appearance of signs of disturbances in electrical and metabolic functions follows a characteristic course. These changes have been demonstrated in experimental examples. In severe hypoxia with occlusion of cerebral arteries, the changes in energy metabolism and electrical phenomena are similar to those in ischemia. The typical signs of oligemic hypoxia, anoxic and hypoxic hypoxia, anemic hypoxia, venous hypoxia and histotoxic hypoxia are characterized in this review. In energy deficient brain tissue the ionic fluxes across the membranes of nerve cells, as well as across the smooth muscle cell membranes of the cerebral artery walls, are of particular interest. Cations have been investigated frequently and in this report the interactions between ions which participate in the regulation of vessel wall tension are discussed. Finally, the redistribution of blood flow after occlusion of single brain-supplying arteries is described.

The combination of percutaneous atherectomy and angioscopy enabled a selective "biopsy" of protruding atheromatous plaque material from 11 patients with arterial occlusive disease. The removed specimens were cultivated as adhering explants or single cells were obtained by enzymatic disintegration. The vast majority of the cultivated cells resembled fibroblasts, but could be identified as smooth muscle cells by their smooth muscle alpha-actin content. Proliferation rate was slow with 0.1 doublings per day. Endothelial cells were not observed by immunologic criteria. The described biopsy technique and in vitro evaluation of cultured human atheromatous plaque material may be useful for a better understanding of atherogenesis.

8 mm long sections of common carotid arteries of conscious, freely moving rabbits were electrically stimulated with DC-impulses by chronically implanted gold-electrodes daily for 1/2 h or two times 1/2 h per day for 4--6 weeks. The electrodes were arranged in such a way that the wall was stimulated transmurally, In the initial phase the tension of the vessel wall increased. After 1/2 h of stimulation the artery wall relaxed at the stimulated section. Repetition of stimuli led to smooth muscle cell proliferation within the stimulated region. The smooth muscle cells formed a cushion protruding into the lumen of the artery mainly at the anodic site of the stimulation-arrangement. The proliferating cells were smaller than those of the underlying tunica media. They were identified as smooth muscle cells by electron-microscopy, contained relatively more lysosomes and endoplasmic reticulum than the original media-cells and produced collagen-fibrils and elastic fibrils as an extracellular matrix material. Below very thick cushions of smooth muscle cells necrosis developed. Animals which were additionally fed with 2% cholesterol in normal food developed typical atheromatous plaques at the site of the anodic stimuli.

Endothelial cells covering the luminal surface of vessels are exposed to at least two different mechanical forces: 1) fluid shear stress produced by the circulation of blood, and 2) periodic stretching and relaxing as a result of the diameter oscillations caused by blood pulsation. In this study we present an apparatus which was constructed to imitate the volume pulse with its typical incisura of the abdominal aorta. Using this apparatus, we exposed cultured endothelial cells to continuously produced cyclic and directional stretching and relaxation for three days. In all experiments cells remained attached and viable when subjected to mechanical stimulation. The vast majority of endothelial cells which underwent mechanical stimulation became elongated and oriented with their longer axis perpendicular to the direction of stretching (angle of cell orientation: alpha = 88.7 degrees +/- 12 degrees; means +/- SD), whereas cells on unstretched membranes had a cobblestone-like appearance and remained in random orientation. In the stretched cells, the factor of elongation was f = 6.8 +/- 1.3; means +/- SD; unstretched cells which exhibited a polygonal shape had a factor of elongation of f = 1.8 +/- 0.8; means +/- SD. In addition, the behavior of cytoskeletal components such as microfilaments and microtubules was examined in the process of cell orientation as both are actively involved in alterations of cell shape and cell migration. Actin filaments were oriented as both are actively involved in alterations of cell shape and cell migration. Actin filaments were oriented in parallel alignment perpendicular to the stretch direction (angle of actin filament orientation: beta = 90.4 degrees +/- 9 degrees; means +/- SD). A distinct orientation of microtubules was not observed, although a noticeable number of microtubules was observed to be in parallel alignment. Furthermore, microtubules of cells which underwent mechanical stimulation exhibited a pronounced asymmetric intracellular distribution with strongly fluorescent cytoplasmic areas in which microtubules seemed to be accumulated. The results indicate that endothelial cell elongation and orientation in vitro can be induced by periodic stretching and relaxation comparable to the periodic oscillations of the vessel wall due to blood pulsation in vivo.

Local transmural electrical stimulation with DC of a carotid artery by means of implanted electrodes causes subendothelial fibromuscular proliferates or atheroma (if the animal receives a cholesterol-containing diet) beneath the anode. The endothelial lining is maintained when weak current is used for stimulation. The model permits studies of permeability of the endothelium in all stages of the plaque development. Ruthenium red as a marker for the glycocalyx is transiently taken up into the cytoplasm of the endothelial cells beneath the anode immediately after a 30 or 60 min lasting stimulation period. When staining the endothelium later than two hours after the end of an acute stimulation period, the ruthenium red staining is again normal. This indicates that the increased permeability to large molecules is reversible. Injection of the calcium entry blocker Flunarizine inhibited the cytoplasmic uptake of ruthenium red, showing that an increased entry of calcium into the endothelial cells may contribute to the disturbance in the permeability of large molecules into the endothelium.

Measurements of the local blood flow through organs by means of heated thermistor-probes enable one to perform continuous recordings of flow. The principle is based on the measurement between a heated and an unheated probe, both implanted in the tissue or placed on the superficial layer of the organ. The flow-measure for this type of blood flow recording is the heat transported from the heated site of the tissue. It is measured in cal-cm(-1)-sec(-1)-degree C(-1). This is the dimension of the heat conductance. Quantification of continuous blood flow measurements in ml flow/g tissue-min has been carried out with combinations of gas clearance and heat transport. It has now become possible to measure blood flow in ml blood-ml(-1) tissue-min(-1) solely with the aid implanted thermistors. Two types of local blood flow measurements are described. 1. Measurements with "slug heating" by which a thermistor is heated for a very short time and the temperature change is subsequently recorded. 2. The measurement of flow by sudden introduction of heat, if a heating coil around a micro-thermistor is switched on or off and the course of the tissue temperature is subsequently followed. It is proven, that the temperature of a point-shaped micro-thermistor in nonperfused tissue and in homogeneous perfused tissue differs only by an exponential factor (see article) where uslug is the temperature field after a slug injection of heat dependent on location, time, blood flow (phi) and partition coefficient for heat (lambda) and where index 0 = unperfused tissue. If the heater is not heated in the form of a delta function but is switched on and the temperature is subsequently recorded or if the heater, after a period of constant temperature, is switched off, the derivatives in respect to time differ only by an exponential factor and can be used as a measure of flow. The evaluation of blood flow is described in detail. The measurements show the following advantages, compared with former techniques: 1. Heat clearance and continuous blood flow measurements by means of heat transport measurements are both possible at the same site. 2. No other operation and procedures are necessary except implantation of the thermistor. 3. Turning on the heater does not affect the tissue and does not cause emotional reactions. As examples the measurements of local blood flow in brain tissue and in the myocardium of conscious animals are described.