Cerebral microvascular architecture in the common tree shrew (Tupaia glis) revealed by plastic corrosion casts.

The vascularization of the cerebrum (cerebral cortex and basal ganglia) in the common tree shrew (Tupaia glis) has been studied in detail using vinyl injection and vascular corrosion cast/SEM techniques. It is found that the arterial supply of the cerebral cortex are from cortical branches of the middle cerebral artery (MCA) and of the anterior cerebral artery (ACA). These arteries are in turn branches of the internal carotid artery (ICA). In addition, the cerebral cortex receives the blood from the cortical branches of the posterior cerebral artery (PCA) that originates from the basilar artery (BA). These cortical arteries gives rise to rectilinear orientated intracortical arteries that are divided into dense capillary networks to supply the cerebral cortex. The capillary networks drain the blood into intracortical veins and then into the tributaries of major superficial cerebral veins. The basal ganglia (caudate and lentiform nuclei) are supplied by central or perforating branches of the ACA and MCA. These central or medullary arteries give rise to arterioles that ramify into dense capillary plexuses. The venous blood from both nuclei drains into venules and finally into the tributaries of internal cerebral veins. It is obvious that on the ventral aspect, the diameter of the lateral striate artery (LSA) and of the penetrating arterioles from the MCA are much smaller than that of the MCA. These arterioles have few side branches while the peripheral branches of the superficial cerebral arteries exhibit several series of branches that are gradually reduced in diameter before branching into intracortical arteries. This could be one of the reasons why the rupture of cerebral arteries in man mostly occurs in the those originating from the ventral surface rather than from the dorsolateral surface.

Adrenal microvascularization in the common tree shrew (Tupaia glis) as revealed by scanning electron microscopy of vascular corrosion casts.

The blood supply of the adrenal gland in the common tree shrew (Tupaia glis) was studied by use of transmission electron microscopy and vascular corrosion cast/scanning electron microscopy techniques. It was found that the gland receives its blood supply from branches of the inferior phrenic, aorta and renal arteries. Upon reaching the gland, these arteries divide into cortical and medullary arteries. The cortical arteries give rise to the subcapsular capillary plexuses which partially enclose the clusters of cells in the zona glomerulosa (ZG) and appear as lobular-like microvascular networks before running among the cellular cords in the zona fasciculata (ZF) and zona reticularis (ZR). It was noted that the capillaries in ZG and ZR are with more anastomoses than those in the ZF. Capillaries from the ZR become the sinusoidal capillaries in the adrenal medulla before proceeding to the peripheral radicles of the central vein. The medullary arteries penetrate the adrenal cortex and occasionally give off small branches to supply the inner cortex, especially the ZR. Their main branches break up into small or conventional capillaries in the adrenal medulla. These capillaries drain the blood into the peripheral radicles of the central vein and medullary collecting veins which proceed further into a very large central vein. The present findings illustrate that the adrenal medulla receives two blood supplies that yield somewhat different influences upon the adrenal medulla. The portal blood vessel could not be illustrated in the tree shrew adrenal gland.

Angioarchitecture of the coeliac sympathetic ganglion complex in the common tree shrew (Tupaia glis).

The angioarchitecture of the coeliac sympathetic ganglion complex (CGC) of the common tree shrew (Tupaia glis) was studied by the vascular corrosion cast technique in conjunction with scanning electron microscopy. The CGC of the tree shrew was found to be a highly vascularised organ. It normally received arterial blood supply from branches of the inferior phrenic, superior suprarenal and inferior suprarenal arteries and of the abdominal aorta. In some animals, its blood supply was also derived from branches of the middle suprarenal arteries, coeliac artery, superior mesenteric artery and lumbar arteries. These arteries penetrated the ganglion at variable points and in slightly different patterns. They gave off peripheral branches to form a subcapsular capillary plexus while their main trunks traversed deeply into the inner part before branching into the densely packed intraganglionic capillary networks. The capillaries merged to form venules before draining into collecting veins at the peripheral region of the ganglion complex. Finally, the veins coursed to the dorsal aspect of the ganglion to drain into the renal and inferior phrenic veins and the inferior vena cava. The capillaries on the coeliac ganglion complex do not possess fenestrations.

Microvascularization of the common tree shrew (Tupaia glis) superior cervical ganglion studied by vascular corrosion cast with scanning electron microscopy.

Microvascularization of the superior cervical ganglion (SCG) of the common tree shrew (Tupaia glis) was investigated by the vascular-corrosion-cast technique in conjunction with scanning electron microscopy. It was found that the SCG of the tree shrew is a highly vascularized organ. It receives arterial blood from branches of the external and common carotid arteries which enter the rostral and caudal portions of the ganglion. These arteries give rise to a subcapsular capillary plexus before branching off to form a group of densely packed intraganglionic capillaries. Moreover, the intraganglionic capillaries tend to follow a tortuous course that is essentially parallel to the longitudinal axis of the ganglion, and they form anastomoses with each other. In addition, the intraganglionic capillaries are also connected to a subcapsular capillary plexus. The capillaries of the SCG converge into venules and collecting veins which subsequently drain rostrally and caudally into the systemic veins. However, neither a pattern of blood vessels resembling glomeruli nor a portal-like intraganglionic microcirculation was observed.

Cytoarchitecture of the common tree shrew (Tupaia glis) superior cervical ganglion. A scanning electron microscope study on vascular cast/enzyme-digested superior cervical ganglia.

The cytoarchitecture of the superior cervical ganglion of the common tree shrew was investigated by scanning electron microscopy using the vascular cast technique in conjunction with digestion by collagenase-hyaluronidase/HCl. The main cellular constituents were found to be multipolar neurons that were densely distributed throughout the ganglion. These neurons were covered with a smooth cytoplasmic sheath of satellite cells. After the removal of this sheath by digestion of increased duration, the blebs or knobs on the neuronal surfaces became evident. A meshwork of nerve fibers over the surface of neurons was also observed. Preganglionic sympathetic nerve fibers, giving rise to fine branches that ran toward the postganglionic sympathetic neurons before forming synapses, were demonstrated. Groups of neurons surrounded by capillary loops were also frequently observed.

SEM study on the dorsal lingual surface of the common tree shrew, Tupaia glis.

The dorsal lingual surface of the common tree shrew was examined by SEM after treating it with HCl to remove the mucous substance. Filiform (FI), fungiform (FU) and circumvallate papillae (CI) were observed. The FI exhibited a small circular bulge surrounded by anterior and posterior filamentous processes. FU were scattered among the FI. There were 3 CI separating the anterior 4/5 from the posterior 1/5 of the tongue. In addition, a group of conical projections with caudal orientation was found anterior to the palatoglossal fold on each side of the tongue. Microridges were widely observed on the entire dorsal lingual surface, except on the free surface of FI processes.

Microvascularization of the rat superior cervical ganglion. A three-dimensional observation.

The three-dimensional image of the microvascularization of the rat superior cervical ganglion (SCG) was examined using the vascular corrosion cast technique in conjunction with scanning electron microscopy. It was found that the rat SCG was a highly vascularized organ. Arteries supplying the ganglion gave rise to a subcapsular capillary plexus before branching off to become intraganglionic capillaries. Two types of intraganglionic capillaries, large and small, were observed throughout the organ. Numerous anastomoses among these capillaries were found before they converged into venules and collecting veins. However, a pattern of blood vessels resembling portal-like intraganglionic microcirculation could not be demonstrated.