Shogo Yamagata

Freeze-fracture of capillary endothelium in rat brain.

SummaryThe rat brain capillary was studied with freeze-fracture technique. The attached plasmalemmal vesicles were quite few in number on the luminal front and sometimes numerous on the contraluminal side. The fracture appearance of some tight junctions showed interconnecting ridges on face A and complementary furrows devoid of particles on face B, comparable to the common tight junction in the normal epithelia. Other tight junctions revealed a preferential disposition of quasicontinuous rows of particles on shallow furrows of face B, resembling the tight junctional strands of capillary endothelium in non-cerebral tissues. Either behavior is probably due to the difference in the fracture plane around the single fibril. In addition, the tight junctional strand could surround the perimeter of the endothelial cell completely although the exposed strand of tight junction was limited in length.

Cell membrane structure of vascular smooth muscle of circle of Willis.

SummaryCell membranes of vascular smooth muscles of the circle of Willis were studied in thin sections and freeze-replicas. The cell membranes were differentiated into a caveolae intracellulares zone and caveolae-free zone, both of which were generally arranged in an alternate manner and parallel to the major axis of the smooth muscle cell. In the former zone, the caveolae intracellulares, about 600 Å in diameter, were neatly oriented in one to several rows running parallel to the longitudinal axis of the muscle cell with a centre-to-centre distance of about 800 Å. The latter zone was of variable width and smooth, apart from membrane particles or scattered caveolae, and corresponded mainly to the dense area and partially to the myofibril area beneath the cell membrane. Membrane particles were generally more numerous on face A than on face B, and their average number per μm2 was about twice as many inside the rows of the caveolae as outside. Rosette formations of membrane particles were often evident at the stomal rims of the caveolae. Adherentes and gap junctions were occasionally found on the caveolae-free areas which often protruded externally. Tight junctions appeared as a collection of scattered strands, which frequently showed free ends and were parallel to each other and also to the major axis of the smooth muscle cell.

Specialized intercellular junctions in human intracranial germinomas

SummaryThree human intracranial germinomas were studied using thin section and freeze-fracture techniques. In thin sections, the spheroidal cells were similar to the seminoma cells of the testis. There were three types of specialized intercellular junctions; desmosomes, gap junctions, and tight junctions, were evident between the spheroidal cells. In freeze-fracture replicas, tight and gap junctions were easily differentiated by their characteristic deployment patterns of their subunits. The tight junction revealed a discontinuous, circular, serpentine, or ramifying complex of ridges and furrows, referred to as fascia occludens. The gap junction was also discontinuous and largely confined to the compartment formed by the ramifying ridges and furrows of tight junctions, and revealed aggregated particles and pits on fracture faces A and B, respectively.

Specialized junctional complexes in human meningioma

SummaryFive human meningiomas were studied with techniques of thin section and freeze-fracture. Three specialized junctional complexes, desmonsomes, gap and tight junctions, were found between adjacent plasma membranes. Desmosomes were not shown in freezefracture replicas; they exhibited a charactersstic structure in thin sections. In thin sections the outer leaflets of adjacent plasma membranes of gap junctions appeared to fuse, obliterating the intercellular space. The gap junction in replicas was irregularly ovoid or polygonal in form, mostly 0.1–1.0 μ in diameter, and characterized by a hexagonal aggregation of particles in face A and associated pits in face B. The outer leaflets of adjacent plasma membranes in the tight junction fused at discrete points in thin sections. In replicas, the tight junction was characterized by short complexes of serpentine or ramifying ridges in face A and furrows in face B, and mostly discontinous in distribution. The histogenesis of meningioma cells was discussed from a standpoint of the characteristic features of the specialized intercellular junctions.

Freeze-fracture images of capillaries in normal and neoplastic pituitaries

SummaryThe capillaries in five human chromophobe adenomas were studied by thinsection and freeze-fracture techniques. Fenestrae were found in the attenuated portions of the endothelium, and plasmalemmal vesicles in the nonfenestrated portions. In freeze-fracture replicas, the fenestrae, 600–700 Å in diameter, were revealed as circular holes in fracture face A and circular broken-off necks in face B, some 40–60 occurred per μm2. When the fracture process passed in a stepwise fashion from the luminal into the contraluminal plasma membrane, the fenestrae at the fracture edge involved both plasma membranes. Similar configuration of fenestrae was evident in the capillary endothelium of the rat pituitary. The fenestrae in the chromophobe adenoma were much less frequent than in the normal rat pituitary.The plasmalemmal vesicles occurring in replicas on one side of the cell did not appear to open to the other side of the cell. When the fracture followed the contours of the attached plasmalemmal vesicles, they appeared as smooth depressions in face A and domes in face B. When the fracture did not follow the contours of the vesicles, they were revealed as holes or depressed circular plaques in face A and broken-off necks or circular constellations of particles in face B. The plasmalemmal vesicles were more abundant and obvious in the tumour than in the normal rat pituitary.

Contractile Activities of Spastic Canine Basilar Arteries and Its Surrounding Clot

A prolonged vasospasm was produced in the canine basilar artery by administration of fresh autogenous arterial blood into the chiasmatic cistern. Lyophilized homogenates of normal and spastic canine basilar arteries as well as of blood clot around the spastic artery, were made, and their contractile activities were studied with the canine basilar artery in vitro. The lyophilized homogenates of the spastic artery and the blood clot induced a sustained, strong contraction, whereas those of the normal artery produced a transient, slight contraction. The contraction induced by the lyophilized homogenates of spastic artery was reduced slightly by methysergide and greatly by phentolamine. It may be suggested that vasoactive substances are present in the spastic artery as well as in its surrounding clot.