Hiroyoshi Ninomiya

The Vascular Bed in the Rabbit Ear: Microangiography and Scanning Electron Microscopy of Vascular Corrosion Casts

The vascular bed of the rabbit ear has been studied with light microscopy, microangiography and scanning electron microscopy of resin casts in a series of 20 ears. The major arteries supplying the ear were the central and rostral auricular branches of the caudal auricular artery. The caudal auricular branch was not observed, except as a small vessel supplying the rostral auricular base. The central auricular branch supplied blood to most of the auricular integument and was surrounded by capillaries extended from those supplying the skin. The periarterial capillaries formed a fine, compact network in the tunica media and were closely related to the central auricular branch. Evidence is presented suggesting that this vascular mechanism has a counter‐current heat‐exchange function for regulating body temperature. The artery had the well‐developed internal elastic lamina and intimal cushions that regulate blood flow at the branching sites. A number of arteriovenous anastomoses were also observed between arterioles and venules, particularly in marginal regions of the ear. The intimal cushions and arteriovenous anastomoses might play an additional role in thermoregulation by regulating local blood flow in the ear.

Comparative anatomy of the ophthalmic rete and its relationship to ocular blood flow in three species of marine mammal

OBJECTIVE To examine the blood supply to the eyes of bottlenose dolphin (Tursiops truncatus), spotted seal (Phoca largha), and California sea lion (Zalophus californianus). Emphasis is placed on exploring the anatomic function in the context of aquatic life. PROCEDURE Methyl methacrylate casts were prepared and studied using a scanning electron microscope. Infrared images of the eye were recorded using a thermocamera. RESULTS In all three marine species, blood is supplied to the ophthalmic rete. The main source of blood supply to the rete is the basilar rete via the spinal rete in the dolphin and via the ophthalmic artery in the seal and sea lion. The retinal and choroidal arteries are derived from the rete. The dolphin rete showed a very well-developed arterial network occupying most of the orbit. The rete in pinnipeds was less developed with several entwining arteries, unlike that in cetaceans. Thermographic examination revealed that the eye shows a higher degree of thermal emission than adjacent areas of the skin in these 3 species. DISCUSSION The role of the rete in aquatic mammals appears to conserve ocular temperature so that the appropriate operating temperature for photoreceptors and ocular muscles can be maintained in a cold ambient temperature. Additionally, the rete might have a flow-damping effect by maintaining resistance to blood flow in the orbit. This study highlights the special nature of ocular vascular anatomy and function that enabled the unique adaptation of aquatic mammals to life in aquatic habitats.

Vascular Architecture of the Canine Prepuce

The blood supply of the canine prepuce is described as studied with gross dissection and acrylic resin injection casts. The conclusions of this study are based on gross dissection of 10 animals and 12 injection cast preparations. The arterial supply and the venous drainage is described in some detail and compared with similar descriptions by other investigations utilizing similar and varied techniques.

Microvasculature of the California sea lion (Zalophus californianus) eye and its functional significance.

OBJECTIVE To examine the ocular circulation in California sea lions (Zalophus californianus). ANIMALS STUDIED Eyes were obtained postmortem from three sea lions that died while in captivity. PROCEDURES Specimens from sea lions were investigated using scanning electron microscopy (SEM) of vascular corrosion casts. The thermal characteristics of live animal eyes were measured using an infrared imaging system. RESULTS The major orbital artery of the sea lion was the ophthalmic artery. The artery was remarkably thick in diameter, showed a marked convolution and formed an ophthalmic rete around the optic nerve at the posterior pole of the eyeball. The long posterior ciliary artery terminates to form a prominent inner arterial circle at the pupillary margin. The iridial arteries originated from the arterial circle showing either a crimped or somewhat coiled course, extending toward the root of the iris and formed a root supplying a large amount of blood to the iris and ciliary bodies. The venules in the conjunctiva formed a well-developed venous plexus. The vortex veins showed a dilation and constriction at the site passing through the sclera. Thermographic examination revealed that the eye showed a higher degree of thermal emission than adjacent skin areas. CONCLUSIONS These characteristics suggest that the ocular vasculature might play roles in thermoregulation as well as in hemodynamics by draining a large amount of blood so that the appropriate operating temperature for the eye can be maintained in a deep and cold aquatic environment.

The Capillary Circulation in the Penile Skin of the Dog

The microcirculation of the penile skin of the dog is described. This study is based on the examination of the penile skin vasculature of 14 adult dogs in which injection cast preparations of the capillary systems had been made. The capillary organization was examined with the aid of a scanning electron microscope. The organization of the capillary system and associated microregulatory vessels are presented as a model for further investigation of micro‐circulatory anatomy and physiology.

Microvascular growth of 7,12‐dimethylbenz(α)anthracene‐induced adenocarcinomas in rats: histology and scanning electron microscopy of resin casts

Vascular changes at various stages of growth of 7,12-dimethylbenz(alpha)anthracene (DMBA)-induced mammary adenocarcinomas in 22 female Sprague-Dawley rats were investigated using histology, immunohistochemistry and scanning electron microscopy (SEM) of corrosion casts. In the early stage of tumour growth, capillaries within the neoplasms were thin, with 8-10 microm diameter, and characterized by rows of vascular sprouts representing extensive neovascularization and formation of a high-density capillary plexus. In the intermediate stage of tumour growth, the growing tumour was multi-nodular and tumour cells were arranged in a tubulopapillary pattern. Capillaries formed spheroid vascular capsules and were characterized by dilation, to a diameter of 10-80 mum, and blind ends. In the late stage of tumour growth, a remarkable reduction in the number of vascular endothelial growth factor-positive cells and Ki-67-stained nuclei was demonstrated. The tunica media of nutritive arteries displayed a tendency to atrophy. Many arteriovenous anastomoses between the major arteries and the veins were found in regions just before their entry into the tumour. The central regions of the tumour were degenerative and necrotic, and vasculature was confined to surface regions of the tumour, forming a basket-like configuration around the avascular central regions. Resin leakages representing haemorrhage or oedema and distortions such as flattening, break-off and strangulations of capillaries were frequently observed, all of which are known as late tumour signs. We concluded that these microvascular alterations might change the homogeneity of tumour perfusion and contribute to necrosis in central portions of the tumour.

Testicular Vascular Organization in Naturally Occurring Unilateral Cryptorchidism of an Adult Male Pig

ブタに自然発生した潜伏精巣(一側性)の血管系の変化を,アクリル樹脂鋳型法で肉眼および走査型電子顕微鏡で立体的に観察した.また,比較のために反対側の陰嚢内(正常)の精巣も同様の方法で標本を作成して観察した.潜伏精巣では正常な精巣に比べ,主要血管が著しく蛇行しており,精細管をとりまく毛細血管には退行変化と思われる所見が認られ,その毛細血管網も荒廃していた.こうした血管系の変化と潜伏精巣に特有の精上皮脱落との関連について考察した.