Treatment of experimentally induced cerebral atherothromboembolism in an animal model with streptokinase and taurochenodeoxycholate.

In cerebral atherothromboembolic accidents it is essential to quickly remove both the thrombotic and cholesterol crystal vascular obstructions. In this study we induced cerebral atheroembolic infarction in adult male NZW rabbits. Post induction we treated groups of animals with saline, streptokinase (SK)-only, or streptokinase and taurochenodeoxycholate (TCDC). The tissues were fixed 24 hours later and the infarcts were then measured. No remarkable damage resulted from the agents' use in the cerebral vascular bed, or in the hepatic parenchyma. Both treatments produced a dramatic reduction in the area and perimeter measurements of the infarcts when compared to control-treated animals. Both SK treatments drastically reduced the sizes of induced infarcts. It is suggested that a combined thrombolytic/emulsification treatment may drastically reduce the extent and distribution of cerebral infarcts which result from cerebral atherothromboembolism.

Combined streptokinase and taurochenodeoxycholate action on experimentally induced atherothromboemboli. Chandler Tube Study.

Atheroembolic lesions consist of both thrombus and atheroma, including cholesterol crystals; therefore, dissolution requires both a thrombotic agent and a lipid emulsifier. In vitro tests were performed in a Chandler tube apparatus to assess the effectiveness of predetermined dose and concentration levels for such agents. Between 0.065 and 0.1 mL of human atheroma, concentrated at 125 mg/mL, was added to 1 mL of recalcified rabbit whole blood in a Chandler tube to produce an atherothromboembolus. Specified amounts of streptokinase (SK) and/or taurochenodeoxycholate (TCDC) were introduced into the tube, either SK first, followed 30 minutes later by TCDC, or in the reverse order. The experimental thrombi were measured for length and weight, and samples from representative thrombi were processed and examined with both light and transmission electron microscopy. The combined SK/TCDC treatment appears to work best of all the treatments in reducing the size of the experimental thrombi and their cholesterol crystal components; and better than the TCDC/SK treatment. It is suggested that this combined treatment might be useful in the treatment of atherothromboembolism.

An assessment of the extent and distribution of experimentally induced cerebral atheroembolic vascular occlusions and infarcts.

Certain types of stroke, TIAs and Amaurosis Fugax can result from atheroembolism from the Carotid bifurcation. This study was undertaken to establish qualitative and quantitative baseline criteria in an animal model for future studies evaluating the effectiveness of thrombolytic and cholesterol emulsifying agents which could eliminate or reduce experimentally induced occlusive atheroembolic lesions. Sixteen male NZW rabbit received sublethal intracarotid injections of human atheroma. After 24 hours the animals were sacrificed, having their brains fixed by cardiac perfusion. Each left hemisphere was coronally sliced anteroposteriorly at 3 mm intervals, and paraffin or methacrylate sections were taken from each slice and stained with H & E or Toluidine Blue. Samples from infarcted tissue were processed for TEM observation. Each section was projected onto the digitizing tablet of a Microplan II image analysis system. The perimeter length, area and maximum diameter were measured for each infarct. The regional distribution of each infarct per section level was recorded on stereotaxic atlas diagrams. The vascular lesions were characteristic of cerebral atheroembolic occlusions. The infarcts were distributed primarily in the cortical and subcortical regions, and were largest in the distribution territory of the Middle Cerebral artery. The morphometric parameters of the infarcts were highly variable at all slice levels.

Assessment, in vitro, of the thrombogenicity of embolic homologous arterial thrombus material and of cholesterol crystals.

One of the complications associated with atherothromboembolic lesions is thrombosis. Recent evidence suggests that a non-lipid component of atheroma is intensely thrombogenic. To determine whether other of the embolic components might be thrombogenic, both homologous arterial thrombus material and pure cholesterol crystals were assessed by adding 0.9 mg of thrombus material or an equivalent quantity of crystals to 1 ml aliquots of recalcified rabbit arterial blood in tests designed to measure either clotting times or the size and weight of thrombi experimentally induced in a Chandler tube apparatus. This data was compared to that of comparative saline control conditions. The results indicate that homologous arterial thrombus material is moderately thrombogenic and that cholesterol crystals are not thrombogenic. This study demonstrates that embolizing arterial thrombus material could be contributory to secondary, and thus potentially more injurious, reactions in embolic vascular disease, and that cholesterol crystals appear not to contribute to complicating secondary thrombotic reactions.

Cerebral atheroembolism. An animal model.

Human atheromatous material was injected into the cerebral vasculature of anaesthetized rabbits via the left common carotid artery. The lethality of varying dosages was determined and the distribution and general character of occlusive vascular lesions which developed were analyzed by light and transmission electron microscopy. It was found that a dose exceeding 55 mg of the atheromatous material (125 mg/ml saline) was lethal in New Zealand white male rabbits weighing between 3 and 5 kg. In nonsurviving animals, parts of the Circle of Willis and usually one or more of its major tributaries were occluded. Some surviving animals exhibited signs of neurologic deficit evidenced by motor dysfunction. Occlusive vascular lesions found in surviving animals were predominantly localized in ipsilateral cortical and subcortical vessels within the distribution territory of the middle cerebral artery. The character of occlusive lesions showed strong evidence of thrombosis. These results demonstrated that this experimental system may be useful as a model for the study of blood-atheroembolic vascular reactions, cerebral infarction development and the testing of agents potentially prophylactic against the development or stabilization of occlusive lesions.

Thrombogenicity of components of atheromatous material. An animal and in vitro model of cerebral atheroembolism.

Human atheromatous material was separated into lipid and nonlipid fractions by ether and chloroform-methyl alcohol procedures. The maximum nonlethal doses of nonlipid, lipid, and whole (unseparated) atheromatous material were 8 mg, between 15 and 30 mg, and between 50 and 60 mg when injected into the left common carotid arteries of rabbits. In vitro production of thrombi showed that the nonlipid material produced thrombi that were larger in volume, weight, and length than those produced by whole material.

Light and scanning electron microscopic observations of the effects of sublethal doses of methotrexate on the rat small intestine.

The small intestines of adult rats were examined by light and scanning-electron microscopy after sublethal doses of methotrexate were injected at 5, 3 and 1 mg, respectively, per rat per day, for three days. Methotrexate inhibited mitosis and thereby disrupted the steady state system of the epithelium. Villi and crypts progressively diminished up to about four and one-half days after the initial injection. Thereafter, recovery began and, by day 7, relatively normal morphology was restored. In the degenerative phase, the loss of crypt-villus continuum was frequently observed, the former crypts forming cyst-like structures. The columnar cells became flat and pleomorphic but epithelial continuity was maintained. Goblet cells apparently decreased in number. Paneth cells, especially in the ileum, appreciably increased in size and number. During the recovery phase, the cystic crypts apparently re-established continuity with the villus epithelium. Size and proportion of all epithelial cell types returned to normal. Scanning electron microscopy showed villus fusion and the cellular pleomorphism and loss of microvilli during the degenerative phase. During recovery of the villi some alteration in orientation and shape remained as shown by scanning electron microscopy.

A region of mitochondrial division in the epithelium of the small intestine of the rat.

Electron microscopic examination of samples from various regions of the rat small intestine was carried out. The number of mitochondria in the epithelial cells was estimated. The counts were made in sections of cells cut along their longitudinal central plane. The errors involved in extrapolating these counts to the whole cells were also estimated. The average mitochondrial number per cell section was 21 in the lower third of the crypts, it gradually increased in the mid and upper thirds and reached about double, 42, at the villus base. The known forms of dividing mitochondria were identified in the mid and upper third of the crypts. The counts remained around 42 along the epithelium of the villi. Crypt cells are continually produced in the lower crypt; these cells migrate to the villi while differentiating into nonproliferative absorptive cells. After inhibiting mitosis by methotrexate, this migration continued (Altmann, '74) and mitochondrial division persisted. In segments of the jejunum isolated surgically from the functional intestine for three weeks, mitosis and cell migration continued, but no evidence of mitochondrial duplication was found. Each mitochondrion probably undergoes a division as the crypt cells migrate from the mid-crypts to the villus. As a result, the villus epithelial cells contain double numbers of mitochondria. It appears that the mitochondrial division is not directly related to mitosis and is elicited by a stimulus present only in the functional intestine.