ber die M�glichkeiten der Kapillarverengung im Zentralnervensystem

The morphology of spastic intracerebral arterioles

Pial and parenchymatous vessels of cat cerebral cortex were subjected to electrical stimulation by direct current by the application of a silver gel electrode to the vessel wall. A current of small intensity (5V, 10mA, 2s) was sufficient to produce spastic constriction of the pial arteries. Arterial spasm was always segmental and lasted up to 20 min. Intracerebral vessels were stimulated by applying a DC of 20 to 100 V, 20 to 150 mA for 30 s to the brain. Intracerebral muscular vessels showed varying diameters and spastic segments in frozen sections and by electron microscopy. The lumen of spastic vessels was collapsed. The vessel wall convoluted, indicating that the factors causing spastic constriction are different from those responsible for physiological vessel wall constriction. In many cases the perivascular tissue of moderately constricted or spastic arterial vessels was destroyed while the tissue around capillaries always remained intact. It is suggested that periarterial tissue destruction is the result of the sudden and powerful constriction in muscular arteries.

Computer tomography in cerebral death

Computer tomography has been applied in a material of six patients meeting the criteria for cerebral death. The primary intracranial pathology, haemorrhages, infarction and contusions were demonstrable. No generalized reduction of the attenuation characteristic of infarction was found in spite of angiographic arrest of the intracranial circulation. Compression and obstruction of small brain vessels may in some cases be the primary cause of arrest of the brain circulation in cerebral death and not an increase of the intracranial pressure to levels approaching or surpassing the mean systemic arterial pressure.

Cerebrovascular ultrastructural alterations after intra-arterial infusions of ouabain, scilla-glycosides, heparin and histamine

Cardiac glycosides which inhibit Na/K-ATPase (ouabain, scilliroside, scillirosidin) as well as heparin and histamine were infused into a cannulated branch of the middle cerebral artery or by isolated head perfusion in cats and dogs. Ouabain permeating the blood-brain barrier (BBB) caused the same selective swelling of astrocytes and of certain presynaptic elements as after direct application to the brain tissue. The other cellular elements of brain tissue and the vascular endothelium did not react, although the latter was exposed to the highest drug concentrations (about 10-3 M ouabain). By the swelling about one third of the capillaries became more or less constricted accompanied by an increase in endothelial vesiculation and in the number of osmiophilic inclusions in all cells of the vascular wall and of the pericapillary tissue. Osmiophilic material resembling plasma proteins occured in widened intercellular clefts indicating an increased BBB permeability after survival times (40 min). In contrast to the capillaries some terminal vessels are dilated which may correspond to shunt vessels causing an inhomogeneous, even increased cerebral blood flow after ouabain. Scilliroside and scillirosidin cause essentially the same changes as ouabain, but of smaller intensity and extent. In the present study, neither histamine nor heparin caused any structural change of the vessels or brain tissue.