Biomedical subjects

Osamu Ohtani

Publications and source records attributed to Osamu Ohtani.

10 recordsLinked to original sources

PubMed2006

Establishment and characterization of conditionally immortalized endothelial cell lines from the thoracic duct and inferior vena cava of tsA58/EGFP double-transgenic rats.

The basic biology of blood vascular endothelial cells has been well documented. However, little is known about that of lymphatic endothelial cells, despite their importance under normal and pathological conditions. The lack of a lymphatic endothelial cell line has hampered progress in this field. The objective of this study has been to establish and characterize lymphatic and venous endothelial cell lines derived from newly developed tsA58/EGFP transgenic rats harboring the temperature-sensitive simian virus 40 (SV40) large T-antigen and enhanced green fluorescent protein (EGFP). Endothelial cells were isolated from the transgenic rats by intraluminal enzymatic digestion. The cloned cell lines were named TR-LE (temperature-sensitive rat lymphatic endothelial cells from thoracic duct) and TR-BE (temperature-sensitive rat blood-vessel endothelial cells from inferior vena cava), respectively, and cultured on fibronectin-coated dishes in HuMedia-EG2 supplemented with 20% fetal bovine serum and Endothelial Mitogen at a permissive temperature, 33 degrees C. A temperature shift to 37 degrees C resulted in a decrease in proliferation with degradation of the large T-antigen and cleavage of poly (ADP-ribose) polymerase. TR-LE cells expressed lymphatic endothelial markers VEGFR-3 (vascular endothelial growth factor receptor), LYVE-1 (a lymphatic endothelial receptor), Prox-1 (a homeobox gene product), and podoplanin (a glomerular podocyte membrane mucoprotein), together with endothelial markers CD31, Tie-2, and VEGFR-2, whereas TR-BE cells expressed CD31, Tie-2, and VEGFR-2, but no lymphatic endothelial markers. Thus, these conditionally immortalized and EGFP-expressing lymphatic and vascular endothelial cell lines might represent an important tool for the study of endothelial cell functions in vitro.

Animals↗

PubMed2006

Activation of MEK/ERK and PI3K/Akt pathways by fibronectin requires integrin alphav-mediated ADAM activity in hepatocellular carcinoma: a novel functional target for gefitinib.

We have shown that the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor gefitinib ('Iressa', ZD1839) inhibits the development of intrahepatic metastases of hepatocellular carcinoma CBO140C12, and EGFR transactivation by tumor necrosis factor-alpha is a possible target of gefitinib. In the present study, we focused on the fibronectin (FN)-dependent signaling pathway to further elucidate the antimetastatic activity of gefitinib in CBO140C12 cells. We initially observed that FN induced activation of extracellular signal-regulated kinase (ERK), p38 and Akt, as well as cell proliferation and CBO140C12 cell invasion. These responses were mediated by EGFR tyrosine kinase, because gefitinib inhibited these effects of FN. FN-induced ERK, p38 and Akt activation was partly blocked by the Arg-Gly-Asp (RGD)-pseudo-peptide FC-336, anti-alphav integrin antibody RMV-7, the broad-spectrum matrix metalloprotease inhibitor GM6001 and the broad spectrum a disintegrin and metalloprotease (ADAM) inhibitor TAPI-1. But these inhibitors had no effect on EGF-induced signaling pathways, suggesting that integrins and ADAM may be upstream components of EGFR in these responses. These results suggest that FN-induced activation of ERK, p38, Akt, cell proliferation and invasion was mediated, at least in part, via integrins, ADAM and EGFR, and that this FN-induced signaling pathway might be involved in the antimetastatic activity of gefitinib.

ADAM Proteins↗

PubMed2005

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.

Aged↗

PubMed2004

Morphological changes in capillaries in the ischemic brain in Wistar rats.

The microvasculature in the brain plays a vital role in the maintenance of brain perfusion, and fulfills the dynamic requirements of normal brain functions. It is well known that collateral circulation can be induced by ischemia in cerebral infarctions, but it is not known whether cerebral ischemia affects microvasculatures in the ischemic region. In the present study, we examined quantitatively serial changes in capillaries following bilateral common carotid artery ligation in Wistar rats. After the animals were perfused with tetramethylrhodamine isothiocyanate-labeled gelatin 3 h (n = 9), 1 day (n = 9), 7 days (n = 9) and 28 days (n = 9) after the ligation, capillary diameters in the brain sections were measured with a confocal laser-scanning microscope. Capillary diameters of the cerebellum did not differ among all groups, while those in the ischemic regions decreased significantly 3h after the ligation (p<0.01), thereafter gradually returned toward the baseline level, and became significantly larger (168% of the control) 28 days after the ligation (p< 0.01). The density of capillaries in the frontal and parietal cortices increased approximately to 1.3-fold of those of the control level 28 days after the ligation. Transmission electron microscopy showed that the mean ratio of the inner diameter to the outer diameter of capillaries in the frontal cortex became significantly greater 28 days after the ligation (p<0.05). Our data indicate that capillaries dilate in the ischemic brain region in the chronic phase of cerebral ischemia. It is also suggested that neovascularization occurs in the ischemic brain region.

Animals↗

PubMed2004

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.

Adult↗

PubMed2003

Reversible light-driven structural changes between the mono- and bilayer stacking alignments in 4-octadecyloxystilbazolium arylcarboxylate films.

The present investigation deals with the light-driven morphological changes in multilamella films of N-methyl-4-octadecyloxystilbazolium arylcarboxylates (C18OStz+X-) cast on glass slides. The results of XRD analysis show a photostimulated layer expansion and shrinkage of the stacked thin films along the c-axis under alternative illumination at >350 and 254 nm, respectively. It was revealed that such lamellar changes could be switched either way by a reversible transformation between the mono- and bilayer units in these stacked multilamella films. Moreover, such controlled structural adjustments in the alignment could be initiated by the photocyclodimerization of the stilbazolium moieties of the arylcarboxylate salts; i.e., a monolayer-to-bilayer transformation could be induced at a stage of only 10% cyclodimer formation. The photoinduced patterning on the surface of the films was also analyzed by SEM and fluorescence microscopic investigations.

Journal Article↗

PubMed2003

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.

Animals↗

PubMed2003

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.

Animals↗

PubMed2003

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.

Animals↗

PubMed2002

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.

Amygdala↗