SUMMARY Autologous femoral veins grafted between the external iliac arteries in 18 dogs provided a model for studying the hemodynamics and histopathology of vein graft bypasses. The angle of proximal anastomosis was varied by groups (<90°, 90°, >90°) to produce a wide range of flow conditions within the grafts. Four months after implantation, point velocity measurements of blood flow and histological examination of the superior and inferior walls were made at proximal, middle, and distal locations in each graft. Hot-film velocity measurements revealed outwardly skewed velocity profiles in the proximal locations in all grafts, and flow visualization models showed secondary fluid motions and separation zones at those regions. Velocity profiles in the middle and distal regions of the grafts were more symmetrical and showed no flow separation. Histological examination of wall sections along the graft length showed that intimal proliferation occurred focally and ranged from 1 to 100 fita in thickness. No signficant correlation between graft angle and degree of intimal proliferation was found. However, there was a weak inverse correlation between the apparent fluid shear rate and the corresponding degree of intimal proliferation, with the greatest proliferation occurring in the regions experiencing the lowest shearing forces. Regions of low shear rate should be avoided by maintaining adequate flow rates through the grafts and thus minimising losses of patency due to both thrombus formation and intimal proliferation.
The gross and microscopic anatomy of the venom producing parotoid glands of Bufo marinus has been studied by light and electron microscopy and reactions for the presence of glycoprotein and mucopolysaccharides, the catechollamines, 5-hydroxytryptamine or dopamine, glucose-6-phosphatase, adenosine triphosphatase and the steroid nucleus and cholesterol and its esters have been performed. The gland is composed of numerous individual lobules, each lobule surrounded by a double cell layer. The interior surface of the outer layer is thrown into small cytoplasmic projections which traverse a n intercellular space and interdigitate with microvilli formed by the outer plasmalemma of the inner layer. The outer layer resembles smooth muscle-like cells, is rich in adenosine triphosphatase, contains many pinocytotic vesicles and various organelles and may function i n some aspect of venom synthesis, active cellular transport and contraction i n the discharge of the secretory product. The inner layer shows a positive chromaffin reaction, contains various organelles, appears devoid of a plasmalemma on its inner surface and is involved in venom formation and release via a n apocrine type of secretion. The intercellular space is rich in PAS positive materials, while the secretory product, itself, demonstrates a positive chromaffin reaction. The significance of these findings is discussed.
The gross and microscopic anatomy of the venom producing parotoid glands of Bufo alvarius has been studied by light and electron microscopy. Histochemical reactions for the presence of venom constituents and of components in biochemical pathways in the synthesis and release of venom were performed. The gland is composed of numerous lobules. Each lobule is an individual unit with a lumen surrounded by a double cell layer. Microvilli of the outer layer interdigitate with microvilli of the inner layer. Cells of the outer layer resemble smooth muscle cells, are rich in adenosine triphosphatase and glucose-6-phosphatase, and contain numerous pinocytotic vesicles, glycogen granules and various organelles. These organelles include "crystalloids" of what seem to be highly organized agranular reticulum. These outer layer cells probably function in some aspects of venom synthesis, active cellular transport and contraction in the discharge of the secretory product. The inner cell layer demonstrates a positive chromaffin reaction, contains steroid material, various organelles, some pinocytotic vesicles and glycogen granules, and appears devoid of a plasmalemma on its inner surface. This layer is probably involved in venom formation and release via an apocrine type of secretion. Bufo alvarius parotid gland shows significant morphological and histochemical differences from that of B. marinus and more nearly resembles a typical steroid producing organ.
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