Takuro Murakami

Bral1, a brain-specific link protein, colocalizing with the versican V2 isoform at the nodes of Ranvier in developing and adult, mouse central nervous systems

Bral1, a brain-specific hyaluronan-binding protein, has been cloned recently. To gain insight into the role of Bral1, we generated a specific antibody against this protein. We have examined the detailed localization pattern of Bral1 protein and compared it with that of other members of the lectican proteoglycan family, such as brevican and versican, with which Bral1 is predicted to interact. The immunoreactivity of Bral1 antibody was predominantly observed in myelinated fiber tracts in the adult brain and could be detected at P20 in the white matter of the developing cerebellum, suggesting that expression starts when axonal myelination takes place. Furthermore, immunostaining demonstrated that Bral1 colocalized with the versican V2 isoform at the nodes of Ranvier. The present data suggest that Bral1 may play a pivotal role in the formation of the hyaluronan-associated matrix in the CNS that facilitates neuronal conduction by forming an ion diffusion barrier at the nodes.

Molecular cloning of Bral2, a novel brain-specific link protein, and immunohistochemical colocalization with brevican in perineuronal nets

The hyaluronan binding chondroitin sulphate proteoglycans, called lecticans, are the abundant extracellular matrix molecules in the developing and/or adult brain. The link proteins (LPs) are also known to be coordinately present in brain. We report here the molecular cloning and expression analysis of a novel member of LPs: Bral2, predominantly expressed in brain. The Bral2 mRNA expression is first detected at P20 and continued through adulthood, suggesting its functional importance and association with adult-type lecticans. The substantial immunoreactivity of Bral2 is found in several nuclei throughout the midbrain and hindbrain in a perineuronal net pattern. In situ hybridization revealed that Bral2 is synthesized by these neurons themselves, especially by the GABAergic neurons in the cerebellar cortex. Interestingly, the colocalization and synergic importance of Bral2 and brevican in the perineuronal nets is indicated by the comparative immunohistochemical analysis using wild-type and brevican-deficient mouse brain. Our results suggest that Bral2 is involved in the formation of extracellular matrix contributing to perineuronal nets and facilitate the understanding of a functional role of these extracellular matrices.

Pancreatic insulo‐acinar portal systems in humans, rats, and some other mammals: Scanning electron microscopy of vascular casts

Scanning electron microscopy of vascular casts showed that in the mouse, rat, and guinea pig, the pancreatic endocrine islets were frequently interlobular in position and emitted insulo‐venous efferent vessels directly draining into veins. In these animals, the intralobular islets, located within the exocrine lobules, issued insulo‐acinar portal vessels continuous with the lobular capillaries in addition to the insulo‐venous efferent vessels. In humans, monkeys, cows, pigs, dogs, cats, and rabbits, essentially all islets in the pancreas were intralobular in location and emitted the insulo‐acinar portal vessels only. In man and animals examined, especially in the murine species, many lobules lacked an islet, therefore the insular control over the exocrine pancreas seemed to be effected in more or less restricted areas of lobules. Microsc. Res. Tech. 37:478–488, 1997.

Three-dimensional microanatomy of perineuronal proteoglycan nets enveloping motor neurons in the rat spinal cord

Summary. Spinal motor neurons possess reticular coats of extracellular matrix proteoglycans on their somata and proximal dendrites. In order to define the anatomical background of the network, spatial relationships of the perineuronal proteoglycans with synaptic boutons and astrocyte processes were analyzed in rat motor neurons by TEM after histochemical detection of the substances with cationic iron colloid, and by SEM after exposure of the cytoarchitecture with NaOH maceration. Narrow intercellular channels filled with proteoglycan were found to extend along the surface of the neurons to form a homogeneous network of a mesh size of about 1 µm. The system of perineuronal channels consisted of two parts: a primary intervaricose net which meandered among synaptic boutons on the surface of the motor neuron, and secondary subvaricose nets which irrigated interfaces between larger boutons and the neuron. No elements in the perineuronal cytoarchitecture coincided with the meshwork of proteoglycan, indicating the involvement of postsynaptic factors in the distribution of the substance. Thin astrocyte processes surrounding the neurons formed a distinct network with heterogeneous meshes corresponding to boutons of various sizes. The perineuronal glial nets extended their surface area in contact with the intervaricose nets of proteoglycan by complex cellular interdigitations. The subvaricose nets of proteoglycan compartmentalized multiple synapses on large boutons, suggesting an involvement in the division of the synapses during development.

Glomerular Vessels of the Rat Kidney with Special Reference to Double Efferent Arterioles

Corrosion casts of the blood vascular beds of the rat kidney were prepared with methacrylic methyl ester resin. The casts of the individual glomeruli were isolated and coated with carbon and gold to be observed under the scanning electron microscope.1. True double efferent arterioles arising separately from the glomerulus were encountered in 11 out of the 1, 200 glomeruli examined. They were independent vessels formed separately by the capillaries of different glomerular lobules.2. In 55 out of the 1, 200 glomeruli, the normal efferent arteriole arising singly from the glomerulus showed precocious branching at the hilum of the glomerulus. This type of vessel perhaps was described erroneously as two efferent arterioles in previous light microscope studies.3. Constrictions were often found in the juxtaglomerular segment of the afferent arteriole and rarely in the efferent arteriole. This suggests the occurrence of a sphincter at these sites.4. A preliminary description of the glomerular casts in juvenile rats was made. Occasional duplication of efferent arterioles was found in 8-day-old rats.5. Microdissection of the isolated glomerular casts softened by alcohol enabled the observation of glomerular lobules and their capillary connections. For this purpose the use of resin not containing plasticizer was recommended.

Closed circulation in the rat spleen as evidenced by scanning electron microscopy of vascular casts

Rasterelektronenmikroskopische Beobachtungen der Methakrylatausgüsse der Blutgefässe von Rattenmilz ergeben, dass jedes Arteriolenende unmittelbar mit einem Sinus verknüpft ist. Man bekommt nirgends ein Bild, das eine offene Endigung der Arteriolen in die Milzsträge andeutet. Dieses Ergebnis stützt die «geschlossene» Theorie der Milzgefässe, die neuerdings von der «offenen» Theorie überschattet scheint.

Localization of membrane-associated sialomucin on the free surface of mesothelial cells of the pleura, pericardium, and peritoneum

Abstract Strong anionic sites, as recognized by deposition of cationic colloidal iron even at pH 1.5, were distributed on the free surfaces of the mesothelia of the mouse pleura, pericardium, and peritoneum. Methylation inhibited colloidal iron staining on the surface, and successive saponification restored it. Digestion with neuraminidase or hydrolysis of sialic acid with H2SO4 erased the colloidal iron staining. Lectin Limax flavus agglutinin (LFA), which is specific for sialic acid, labeled the free surface of the mesothelium. All these findings strongly suggested that the surface substance contained sialic acid. Moreover, prior treatment with LFA inhibited the mesothelial surface stain with colloidal iron. In transmission electron microscopy, the colloidal iron (pH 7.3)-stained substance took the shape of fine strands of 50–300 nm in length. These characteristics of the substance on the mesothelial surface correspond well with biochemical properties of membrane-associated sialomucin, whose strong and abundant negative charges produce repulsive forces between facing serosal surfaces. This may contribute to prevent serosal adhesion and to reduce friction during movements of organs.

Microvasculature of the Ovary

Oocyte development and hormone secretion are mutually related functions of the ovary. Oocytes develop and mature within developing follicles. Ovarian hormones are secreted from the stromal intersitial tissue, follicle, and corpora lutea, which are transformed from postovulatory follicles. The follicles, corpora lutea, and stroma compose the cortex of the ovary, and appear during the estrous cycle as successively transforming structures accompanied by very dynamic and continuous changes of their microvascular systems, including active angiogenesis, reconstruction, and degeneration of vessels.

Three-Dimensional Structure of Pulmonary Capillary Vessels in Patients With Pulmonary Hypertension

Pulmonary arterial hypertension, pulmonary veno-occlusive disease, and pulmonary capillary hemangiomatosis are included in the same group (group 1) of clinical classification of pulmonary hypertension.1 Histological changes in the small pulmonary arteries (ie, intimal fibrosis and medial hypertrophy) are similar in these 3 diseases, and clinical presentations of the 3 diseases are often indistinguishable.1 However, it is estimated that the hemodynamics of capillary vessels are quite different in each disease. The hemodynamics of capillary vessels (ie, capillary occlusion) play an important role in cardiovascular diseases.2 Thus, clarification of the differences in the hemodynamics is essential to understand the pathophysiology of these 3 diseases. We obtained lung segments from patients with pulmonary hypertension who underwent living-donor lung transplantation and from patients with …

Routine Methods for Vascular Casting and SEM

Most morphological investigations of tubular, alveolar, and cavity systems have been made by examining tissue slices under the light and transmission electron microscope, by reconstruction of serial sections, and by image-analyzing computers. However, during the past two decades our comprehension of these systems has been greatly facilitated by scanning electron microscopic (SEM) examination of corrosion casts.