Autopsy Case of Bilateral Optic Nerve Aplasia with Microphthalmia: Neural Retina Formation Is Required for the Coordinated Development of Ocular Tissues.

Human congenital anomalies provide information that contributes to the understanding of developmental mechanisms. Here we report bilateral optic nerve aplasia (ONA) with microphthalmia in the autopsy of the cadaver of a 70-year-old Japanese female. The gross anatomical inspection of the brain showed a cotton thread-like cord in the presumed location of the optic nerve tract or chiasm. Histologically, no neural retina, optic nerve bundle or retinal central vessels were formed in the eye globe, and the retinal pigment cells formed rosettes. The cornea, iris, and lens were also histologically abnormal. Immunohistochemically, no retinal cells expressed beta III tubulin, and Pax6- immunoreactive cells were present in the ciliary non-pigmented epithelial cells. This case of ONA could be attributed to the agenesis of retinal projection neurons as a sequel to the disruption of neural retina development. The neural retina formation would coordinate the proper development of ocular tissues.

Recent developments in morphology of lymphatic vessels and lymph nodes.

This paper reviews the morphology of lymphatics and lymphangiogenesis in vivo, microenvironments that promote lymphangiogenesis, and the structure and function of lymph nodes. Lymphatic capillaries consist of a single layer of lymphatic endothelial cells (LECs) and have valves, while collecting lymphatics are endowed with smooth muscle cells (SMCs) and valves besides a single layer of LECs. In the embryonic rat diaphragm, LECs first migrate presumably according to interstitial fluid flow and later join to form lymphatic vessels. SMCs of the collecting lymphatics are apparently differentiated from mesenchymal cells. LECs cultured on Cell Culture Inserts under a low oxygen condition proliferate very well and form a lymphatic network. LECs cultured on a collagen fiber network with a natural three-dimensional (3D) architecture under low oxygen rapidly form a 3D lymphatic network. The lymph node initiates an immune response as a critical crossroads for the encounter between antigen-presenting cells, antigens from lymph, and lymphocytes recruited into nodes from the blood. The node consists of spaces lined with LECs and parenchyma. High endothelial venules in the node strongly express Aquaporin-1, suggesting their involvement in the net absorption of water from lymph coming through afferent lymphatics. SMCs in node capsules seem to be involved in squeezing out lymphocytes and lymph. (English Translation of J Jpn Col Angiol 2008; 48: 107-112.).

A case of double aortic arch accompanied by sub-aortic and pre-aortic left brachiocephalic veins and anomalous origin and course of left vertebral artery.

During the elective course of human dissection at the University of Toyama in 2007, we encountered a rare case of double aortic arch accompanied by sub- and pre-aortic left brachiocephalic veins (LBV), and anomalous origin and course of the left vertebral artery in a Japanese elderly female. The double aortic arch formed a complete vascular ring that encircled the trachea and the esophagus. The sub-aortic LBV traversed below the aortic arches between the ascending aorta and the trachea. In addition, there was a small pre-aortic LBV passing anterior to the origins of the aortic arches. The left vertebral artery originated from the left aortic arch and entered the transverse foramen of C3, while the right vertebral artery originated from the right subclavian artery and entered the transverse foramen of C6.

Structure and function of rat lymph nodes.

The lymph node comprises a critical crossroad for encounters between antigen presenting cells, antigens from lymph, and lymphocytes recruited into lymph nodes from the blood. The node consists of spaces lined with lymphatic endothelial cells and parenchyma. The former spaces can be divided into the subcapsular sinuses, lymphatic labyrinths in the deep cortex, intermediate sinuses, and medullary sinuses. The sponge-like framework of the node parenchyma is composed of collagen fibers invested with reticular cells. The parenchyma can be divided into the cortex, deep cortex, and medullary cord. Lymphocytes migrate from the node parenchyma into the lymphatic labyrinths in the deep cortex. Close to the labyrinths are high endothelial venules (HEVs), through which circulating lymphocytes enter the node parenchyma. HEVs strongly express Aquaporin-1, suggesting that HEVs are involved in the net absorption of water, but not protein, from lymph coming through afferent lymphatics. Many LYVE-1 positive sinus reticular cells (i.e., lymphatic endothelial cells) with attached macrophages form a network within the lumen of the medullary sinuses. Fluids and migrating cells arriving at the node preferentially flow through the subcapsular sinuses, intermediate sinuses, and medullary sinuses in this order. Fluids and migrating cells may also enter the cortex through gaps in the floor of the subcapsular sinuses.

Organization and developmental aspects of lymphatic vessels.

The lymphatic system plays important roles in maintaining tissue fluid homeostasis, immune surveillance of the body, and the taking up dietary fat and fat-soluble vitamins A, D, E and K. The lymphatic system is involved in many pathological conditions, including lymphedema, inflammatory diseases, and tumor dissemination. A clear understanding of the organization of the lymphatic vessels in normal conditions would be critically important to develop new treatments for diseases involving the lymphatic vascular system. Therefore, the present paper reviews the organization of the lymphatic vascular system of a variety of organs, including the thyroid gland, lung and pleura, small intestine, cecum and colon in the rat, the diaphragm in the rat, monkey, and human, Peyer's patches and the appendix in the rabbit, and human tonsils. Methods employed include scanning electron microscopy of lymphatic corrosion casts and tissues with or without treatment of alkali maceration technique, transmission electron microscopy of intact tissues, confocal microscopy in conjunction with immunohistochemistry to some lymphatic-specific markers (i.e., LYVE-1 and VEGFR-3), and light microscopy in conjunction with enzyme-histochemistry to 5'-nucleotidase. Some developmental aspects of the lymphatic vessels and lymphedema are also discussed.

Lymph circulation in the liver.

The liver produces a large amount of lymph, which is estimated to be 25 to 50 % of lymph flowing through the thoracic duct. The hepatic lymphatic system falls into three categories depending on their locations: portal, sublobular, and superficial lymphatic vessels. It is suggested that 80 % or more of hepatic lymph drains into portal lymphatic vessels, while the remainder drains through sublobular and capsular lymphatic vessels. The hepatic lymph primarily comes from the hepatic sinusoids. Our tracer studies, together with electron microscopy, show many channels with collagen fibers traversing through the limiting plate and connecting the space of Disse with the interstitial space either in the portal tracts, or around the sublobular veins. Fluid filtered out of the sinusoids into the space of Disse flows through the channels traversing the limiting plate either independently of blood vessels or along blood vessels and enters the interstitial space of either portal tract or sublobular veins. Fluid in the space of Disse also flows through similar channels traversing the hepatocytes intervening between the space of Disse and the hepatic capsule and drains into the interstitial space of the capsule. Fluid and migrating cells in the interstitial space pass through prelymphatic vessels to finally enter the lymphatic vessels. The area of the portal lymphatic vessels increases in liver fibrosis and cirrhosis and in idiopathic portal hypertension. Lymphatic vessels are abundant in the immediate vicinity of the hepatocellular carcinoma (HCC) and liver metastasis. HCCs expressing vascular endothelial growth factor-C are more liable to metastasize, indicating that lymphangiogenesis is associated with their enhanced metastasis.

Bilateral variations of the vertebral arteries: the left originating from the aortic arch and the left and right entering the C5 transverse foramina.

During the dissection course for second year medical students at the University of Toyama in 2005, we encountered variations of the bilateral vertebral arteries: the left directly came off from the aortic arch as the third branch between the left common carotid artery and the left subclavian artery and entered the transverse foramen of C5, instead of C6, whereas the right originated from the right subclavian artery and entered the transverse foramen of C5. The present vertebral artery of each side was possibly formed by the 6th cervical intersegmental artery linked with the longitudinal anastomoses between the cervical intersegmental arteries. Detailed knowledge of vertebral artery variations is crucially important for surgical treatment of blood vessels in the brain, neck and chest.

Surgical anatomy of the cervical carotid artery for carotid endarterectomy.

Carotid endarterectomy (CEA) is the main treatment for atherosclerotic plaque of the cervical internal carotid artery. The surgical anatomy of the carotid arteries was studied in the carotid triangle of 49 cadavers. The carotid bifurcation was located at the level of the lower third of C-3. The superior thyroid artery arose from the anterior wall of the external carotid artery in 70% of specimens and from the distal portion of the common carotid artery in 30%. The lingual artery arose as a separate trunk between the origins of the superior thyroid and facial arteries in 81% of specimens, with the facial artery from a common trunk in 18%, and with the superior thyroid artery in 1%. The occipital artery arose from the posterior aspect of the external carotid artery above the level of origin of the facial artery in 57% of specimens, between the origins of the facial and lingual arteries in 32%, and below the origin of the lingual artery in 11%. The origin of the occipital artery was positioned low and the distal portion of the occipital artery was crossed by the hypoglossal nerve in 20%. The ascending pharyngeal artery arose from the posterior wall of the external carotid artery above the level of origin of the lingual artery in 66% of specimens, below the origin of the lingual artery in 9%, from the proximal portion of the occipital artery in 19%, from the carotid bifurcation in 2%, and from the internal carotid artery in 2%. The branches of the external carotid artery are the key landmarks for adequate exposure and appropriate placement of cross-clamps on the carotid arteries. It is necessary to understand the surgical anatomy of the carotid arteries to carry out successful removal of plaque and minimize postoperative complications in a bloodless surgical field.

Three-dimensional architecture of elastin and collagen fiber networks in the human and rat lung.

Collagen and elastin fibers are the major components of the lung connective tissue, but their spatial organization has not been well documented. We have demonstrated the three-dimensional architecture of collagen and elastin fiber networks in the human and rat lung using scanning electron microscopy. These networks in their original forms were extracted by an alkali-water maceration technique and a formic acid treatment, respectively. The collagen fibers formed a continuum extending throughout the lung and pleura. They were condensed in the alveolar mouth and subdivided into smaller fibers in the alveolar septa, thus forming basket-like networks. Sizes of the alveolar pores in the collagen fiber network of the alveolar septa became larger with age. In the collapsed lung, collagen fibers in the alveolar mouths and septa took on wavelike configurations, while in the inflated lung they became straight. The elastin fibers also formed a continuum, rich in the alveolar mouths and poor in the alveolar septa, were quite straight without any wavelike configuration. Transmission electron microscopy showed that collagen and elastin fibers were intermingled, suggesting that both fiber systems may act as parallel mechanical elements to stress or strain applied. Our results suggest that at low levels of strain the wavy collagen fibers are easily extended to allow alveolar mouths and alveoli to expand, with most of the stress being borne by adjacent elastin fibers, while at higher levels collagen fibers become straight and limit any further distension of alveolar ducts and alveoli. The elastin fiber continuum appears to permit the lung to effectively recoil or retract. The present study has also shown that alveolar pores enlarge with age, suggesting that collagen remodeling may be related to the pathogenesis of emphysema.

Origins and pathways of fluid entering sublobular lymphatic vessels in cat livers.

The liver, which produces a large volume of lymph, has a lymphatic system which can be classified into three categories: portal, sublobular, and superficial lymphatic vessels. As little is known about the origin and pathways of sublobular lymph, this study demonstrates pathways of interstitial fluid flowing into sublobular lymphatic vessels. Livers from cats whose thoracic ducts were either ligated or non-ligated were examined by light-, transmission electron- and scanning electron-microscopy (SEM). Complete ligation of the thoracic duct caused significant dilation of the hepatic sinusoids, the space of Disse, and channels passing through the limiting plate. Sublobular interstitial space and sublobular lymphatic vessels were also expanded. The channels between hepatocytes forming the limiting plate contained collagen fibers, and connected the space of Disse with a sublobular interstitial space. The alkali-water maceration/SEM confirmed that collagen fibers traversing the layer of the limiting plate independently of blood vessels connected collagen fibers in the space of Disse with those in the sublobular space. Complete ligation of the thoracic duct also showed an accumulation of mast cells and plasma cells in the sublobular interstitial space. Our data suggest that fluid in the space of Disse flows along collagen fibers in channels traversing the limiting plate as well as those along the sinusoids and central veins that drain into sublobular veins, and enters the sublobular interstitial space to finally lead into sublobular lymphatic vessels. Our study has also shown that hepatic lymphostasis causes the accumulation of mast cells and plasma cells in the sublobular interstitial space, which may be involved in lymphangiogenesis and fibrogenesis.

Pathways for movement of fluid and cells from hepatic sinusoids to the portal lymphatic vessels and subcapsular region in rat livers.

It has long been a mystery how fluid and migrating cells in the hepatic sinusoids reach lymphatic vessels in the portal tract. Here we describe previously-unknown channels that connect the space of Disse with the portal tract in the rat liver. Transmission electron microscopy was performed on livers injected with either horseradish peroxidase (HRP) or lipopolysaccharide, and scanning electron microscopy was carried out on livers macerated with KOH. Transmission electron microscopy revealed the presence of channels with collagen fibers traversing the limiting plate. A tracer study showed that HRP was in the channels as well as along inlet venules. Dendritic cells in the hepatic sinusoids or between hepatocytes of the limiting plate were also observed extending their pseudopodia through the channels in the limiting plate to the interstitial space of the portal tract. Scanning electron microscopy further showed that many channels (1-3microm in diameter) penetrated through the limiting plate independently of blood vessels and connected the space of Disse with the interstitial space of the portal tract. In addition, the portal tract possessed prelymphatic vessels that were lined with fibroblast-like cells and frequently contained dendritic cells. The initial segment of the portal lymphatic vessels opened to the interstitial tissue space. These results indicate that fluid and dendritic cells in the hepatic sinusoids probably pass through both the space of Disse and the channels traversing the limiting plate, enter the interstitial space of the portal tracts, and finally move from the prelymphatic vessels to the portal lymphatic vessels.

Fluid and cellular pathways of rat lymph nodes in relation to lymphatic labyrinths and Aquaporin-1 expression.

The aim of the present study was to examine the organization of lymph fluid and cellular pathways and distribution of the membrane water channel Aquaporin-1 (AQP-1) in rat lymph nodes. Lymph fluid and cellular pathways within lymph nodes were examined by fluorescent protein tracer/confocal microscopy and by scanning electron microscopy (SEM), While the distribution of AQP-1 was studied immunohistochemically. Tracer studies showed the subcapsular sinuses continued directly at the hilum or via the intermediate sinuses to the medullary sinuses, and lymphatic labyrinths originating with blind-ends in the deep cortex drained into medullary sinuses. Afferent lymph tracers were also observed in node cortex interstitium. By SEM, lymphatic labyrinths appeared densely filled with lymphocytes and had few intraluminal sinus reticular cells, while medullary sinuses possessed well-developed networks of sinus reticular cells. The presence of many lymphocytes wedged in the walls of the lymphatic labyrinth suggested that lymphocytes migrate between the node parenchyma and lymphatic labyrinths. AQP-1 was distributed on the membrane of lymphatic endothelium and reticular cells as well as on both luminal and abluminal cell membranes of high endothelial venules (HEVs). Our SEM findings support the concept that lymphocytes migrate from the node parenchyma into lymphatic labyrinths in the deep cortex. The nodal distribution of AQP-1 plus the presence of a polarized distribution of ion pumps and/or ion channels in the HEV endothelium hypothesized in our discussion could explain the mechanism of the reported lymph-to-plasma fluid flux in lymph nodes and also facilitate the entry of afferent lymph antigens into the node cortex interstitium.

Synapses on GABAergic neurons in the basolateral nucleus of the rat amygdala: double-labeling immunoelectron microscopy.

Although the basolateral nucleus (BL) of the amygdala is known to contain an abundance of gamma-aminobutyric acid (GABA)ergic neurons that regulate the amygdaloid projection neurons and influence storage and consolidation of memory, it remains to be determined what type of neuronal input controls GABAergic neurons in the BL. We examined the synapses that GABAergic neurons form with GABAergic and noradrenergic neurons and terminals with unknown transmitters by double-labeling immunoelectron microscopy using anti-GABA and dopamine-beta-hydroxylase (DBH) antisera. The medium and small dendrites of the GABAergic neurons were shown to receive symmetric, inhibitory-type synapses from GABAergic axon terminals and asymmetric, excitatory-type synapses from noradrenergic axon terminals. Each segment of the GABAergic neurons from perikarya to dendritic spines received both symmetric and asymmetric synapses from unlabeled axon terminals of various forms and sizes. The incidence rates of the two types of synapses were almost identical. Our results suggest that GABAergic neurons in the BL of the rat amygdala might be affected by the excitatory influence of the noradrenergic system and the inhibitory influence of the GABAergic system. Furthermore, these neurons are also strongly influenced by both excitatory and inhibitory-type synapses from neuronal systems other than the GABAergic and noradrenergic systems.