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T Kosaka

Publications and source records attributed to T Kosaka.

At least 73 records · Page 4Linked to original sources
PubMed1999

Microtubule-dependent movement of symbiotic algae and granules in Paramecium bursaria.

Paramecia demonstrate rotational cytoplasmic streaming, in which some cytoplasmic granules and organelles, including symbiotic algae, flow in a constant direction. To elucidate the mechanism of this streaming, we examined the effects of cytochalasins (cytochalasin B and D, and dihydrocytochalasin B) and nocodazole, which are reagents affecting microfilament and microtubule networks, respectively, in the cell. In previous reports, paramecia have been compressed with a coverslip to facilitate observation of cytoplasmic streaming. Here we found that the cytoplasmic streaming of paramecia was suppressed by such compression and then observed the process without compression in this work. In the presence of cytochalasins, cytoplasmic streaming was not affected. In contrast, treatment with nocodazole (10 microg/ml) resulted in discontinuation of cytoplasmic streaming in paramecia. Immunofluorescent microscopic observations by confocal microscopy revealed that the number of intracellular microtubules in nocodazole-treated cells was markedly decreased compared to that of controls. Electron microscopic observations confirmed the decrease. These results suggest that cytoplasmic microtubules play an important role in the cytoplasmic streaming of paramecia.

Animals↗
PubMed1999

Lymphatic routes of the stomach demonstrated by gastric carcinomas with solitary lymph node metastasis.

To clarify whether or not the lymphatic routes that have long been generally accepted are indeed correct, we retrospectively examined the clinical records of patients with solitary lymph node metastasis from gastric carcinoma. From 735 patients gastrectomized with lymph node dissection (more than D1), 51 (7%) were histologically proven to have only one lymph node involved. In 44 of these 51 patients, the involved nodes were all in the perigastric region (N1). There were also 7 patients with a jumping metastasis to the N2-N3 nodes. Three of them were found along the left gastric artery (#7 according to Japanese classification) and the other 4 were found along either the common hepatic artery (#8) or the proper hepatic artery (#12). The depth of invasion was submucosal in 2, proper-muscular in 2, subserosal in 1, and serosa-exposed in 2, and the conclusive stage was II in 2, IIIa in 3, and IIIb in 2. However, 1 of these patients died of liver cirrhosis and 2 died of pneumonia, while the other 4 were still alive at the time of this report more than 5 years after surgery. These results suggest that not every sentinel node is located in the perigastric region near the primary tumor and that, if the preoperative examination indicates submucosal invasion, then a systematic regional lymph node dissection should therefore be carried out.

Carcinoma↗
PubMed1999

Novel non-apoptotic morphological changes in neurons of the mouse hippocampus following transient hypoxic-ischemia.

Apoptosis has been recently implicated in the dying process of neurons under several pathological conditions including ischemia. However, although apoptosis was originally defined on the basis of its unique ultrastructural features (Kerr et al., 1972. Br. J. Cancer 26, 239-257; Wyllie et al., 1980. Int. Rev. Cytol. 68, 251-306), unambiguous ultrastructural evidence of apoptosis has been rarely demonstrated in the adult brain. In this study, we examined ultrastructural changes in mouse hippocampal neurons after transient hypoxic-ischemia. A small population of dentate granule cells showed typical apoptotic ultrastructures that could be used as internal morphological standards of apoptosis, whereas most other hippocampal neurons consistently showed a distinct form of cellular disintegration. Nuclei of the latter cells shrank and became TUNEL-positive but were distinguishable from apoptotic nuclei by both the presence of characteristic reticular-formed chromatin condensation and the absence of nuclear fragmentation. Perikarya of degenerating neurons also shrank as in apoptosis, but apoptotic bodies were not observed. Although organelles other than mitochondria disappeared almost completely from the perikarya, neither plasma nor mitochondrial membranes were disrupted, indicating that these changes were also different from typical necrosis. The presence of a novel form of cell death suggests the necessity of morphological re-examination of neuronal death, particularly in mature neurons in vivo.

Animals↗
PubMed1999

Synaptic localization of the 67,000 mol. wt isoform of glutamate decarboxylase and transmitter function of GABA in the mouse cerebellum lacking the 65,000 mol. wt isoform.

Subcellular localization of the 67,000 mol. wt isoform of glutamate decarboxylase and neurotransmitter function of GABA were investigated in the cerebellum of the mice lacking the 65,000 mol. wt isoform of glutamate decarboxylase. The GABA content decreased by 25% in the cerebellum. Putative GABA-releasing terminals from basket/stellate and Golgi cells were immunostained with glutamate decarboxylase-67 antibody. Basket cell-derived inhibitory postsynaptic currents in Purkinje cells and the high potassium-induced release of GABA were not significantly affected. Although previous investigations have suggested that glutamate decarboxylase-65 is mainly involved in transmitter synthesis and that glutamate decarboxylase-67 is transported to the nerve terminals only after association with glutamate decarboxylase-65, the present results indicate that glutamate decarboxylase-67 is independently concentrated in the nerve terminals and provides GABA for synaptic transmission in the absence of glutamate decarboxylase-65.

Animals↗
PubMed1999

Mechanisms involved in graft-versus-host disease induced by the disparity of minor histocompatibility M1s antigens.

In this study we investigated which type of T cells: high T-cell receptor (TCRhigh, cells of thymic origin) or intermediate TCR (TCRint, cells of extrathymic origin), expanded in the liver and other organs, resulting in the induction of graft-versus-host disease (GVHD) with minor lymphocyte stimulating (M1s) disparity. When 6.5 Gy-irradiated BALB/c (H-2d M1s-1b2a) mice were injected with interleukin-2 receptor beta-chain(-) (IL-2Rbeta(-)) CD3high cells purified from the spleen of B10.D2 (H-2d M1s-1b2b) mice, IL-2Rbeta(+)CD3high cells expanded in the liver and other organs of recipient mice. The majority of these cells were found to be IL-2Ralpha(-)Mel-14(-)CD4(+)Vbeta3(+) in GVHD mice. The CDR3 region in their TCR-alphabeta (i.e. N-Dbeta-N) was polyclonal, although there were skewed usages of Vbeta3 and Jbeta2.4. The majority of cells were confirmed to be of donor origin by the individual discrimination method, namely, they originated from isolated IL-2Rbeta(-)CD3high cells. Interestingly, these T cells lacked cytotoxicity against both a natural killer (NK)-sensitive target and thymocytes with M1s disparity and nondisparity. Another important finding was that activated granulocytes expanded at generalized sites in GVHD mice. The present results raise the possibility that M1s disparity is mainly recognized by TCRhigh cells with unique properties but that direct effector cells that induce GVHD might not be such T cells but rather accompanied granulocytes.

Adoptive Transfer↗
PubMed1999

Morphological observation of canine natural killer cells mediated cytotoxicity.

The cytotoxic effects of canine NK cells on CL-1 target cells were examined by scanning electron microscopy (SEM). NK cell mediated cytotoxicity on CL-1 target cells was detected by 51Cr release assay. SEM showed that a canine NK cell extended projections to the CL-1 target cell. Furthermore, the surface of CL-1 target cells changed a mesh-like structure. Therefore, the cytotoxic effects of canine NK cells on CL-1 target cells were morphologically demonstrated.

Animals↗
PubMed1999

Effect of leukocytapheresis therapy using a leukocyte removal filter in Crohn's disease.

Eighteen patients with active Crohn's disease were treated with one leukocytapheresis session per week for a five-week intensive therapy, decreasing to one leukocytapheresis session per month for five sessions of initial maintenance therapy. Nutritional indices, inflammatory reactions, flow cytometry profiles, and cytokine production were also assessed before and after the intensive and initial maintenance therapy. Nine of the patients (50%) attained remission at the end of the intensive therapy. The nine non-remission patients had exhibited longer periods of suffering and more severely affected sites prior to the therapy. In 14 of 18 patients (77.8%), the nutritional indices, Internal Organization of Inflammatory Bowel Disease (IOIBD) score and Crohn's Disease Activity Index (CDAI) improved from the pretherapy levels, but only the remission group (50%) showed improvement in C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). The remission group showed significantly higher pretherapy CD4+ CD45+ cell ratios and interleukin-2 (IL-2) production than the non-remission group, and significantly lower activated cells.

Adult↗
PubMed1998

Quantitative analysis of GABAergic neurons in the mouse hippocampus, with optical disector using confocal laser scanning microscope.

The numerical densities (NDs) of glutamic acid decarboxylase (GAD) 67 immunoreactive (IR) neurons in the mouse hippocampus were estimated according to the optical disector method using a confocal laser scanning microscope (CLSM), and the cell sizes of disector-counted neurons were measured. Particularly, we focused on the dorsoventral differences of the NDs and cell sizes in individual subdivisions and layers. The NDs of GAD67-IR neurons were larger at the ventral level than at the dorsal level in most subdivisions and layers, except in the stratum pyramidale (SP) of the CA1 region and stratum radiatum (SR) of the CA3 region. In the whole hippocampus, the ND of GAD67-IR neurons was 5.7+/-0.2x103/mm3 at the dorsal level, and 7.3+/-0.3x103/mm3 at the ventral level. The laminar differences showed that the NDs of GAD67-IR neurons in the principal cell layers were generally larger than those in the dendritic layers in each subdivision. The ND of GAD67-IR neurons was largest in the SP of the CA1 region at the dorsal level (13.5+/-0.9x103/mm3), and smallest in the molecular layer (ML) of the dentate gyrus (DG) at the dorsal level (1.7+/-0.2x103/mm3). The mean cell sizes of GAD67-IR neurons also showed prominent dorsoventral and laminar differences. In the CA3 region, the mean cell size of GAD67-IR neurons was smaller at the dorsal level than at the ventral level, while in the DG, it was larger at the dorsal level than at the ventral level. On the other hand, the mean cell size of GAD67-IR neurons in the CA1 region showed no significant dorsoventral difference. In the whole hippocampus, the mean cell size of GAD67-IR neurons was slightly smaller at the dorsal level (somatic profile area 149.2+/-2.5 microm2) than at the ventral level (154.2+/-2.9 microm2). The laminar differences showed that the mean cell sizes of GAD67-IR neurons in the principal cell layers were generally larger than those in the dendritic layers in each subdivision. The mean cell size of GAD67-IR neurons was largest in the SP of the CA3 region at the ventral level (180.7+/-8.7 microm2), and smallest in the stratum lacunosum-moleculare (SLM) of the CA3 region at the dorsal level (115.9+/-7.9 microm2). The cell size distributions in individual layers revealed that GAD67-IR neurons were roughly classified into two subgroups. The composition of these subgroups suggested the heterogeneity of GAD67-IR neurons in the mouse hippocampus in view of cell size

Animals↗
PubMed1998

Biologically active oligodeoxyribonucleotides. 5. 5'-End-substituted d(TGGGAG) possesses anti-human immunodeficiency virus type 1 activity by forming a G-quadruplex structure.

A series of hexadeoxyribonucleotides (6-mers), d(TGGGAG), substituted with a variety of aromatic groups at the 5'-end were synthesized and tested for anti-human immunodeficiency virus type 1 (HIV-1) activity. While unmodified d(TGGGAG) (31) had no anti-HIV-1 activity, compound 23 with a 3,4-di(benzyloxy)benzyl (DBB) group at the 5'-end potently inhibited the HIV-1IIIB-induced cytopathicity of MT-4 cells in vitro (IC50 = 0.37 microM) without cytotoxicity up to 40 microM. A thermal denaturation study on the 5'-end-substituted 6-mers by means of the circular dichroism (CD) spectra demonstrated that the aromatic substituent attached at the 5'-end of the 6-mer strongly enhanced the formation of a parallel helical structure consisting of four strands (quadruplex). On the contrary, compound 36, in which one of the guanosines of 23 was replaced by a thymidine, did not form a quadruplex, thus exhibiting no anti-HIV-1 activity. Moreover, both compound 15, with a tert-butyldiphenylsilyl group solely at its 3'-end, and compound 21, with a relatively small substituent, a benzyl group, at the 5'-end, formed quadruplexes but had no anti-HIV-1 activity. These findings led us to the conclusion that both the quadruplex structure and the aromatic substituent with adequate size at the 5'-end are crucial for the interaction of the 5'-end-substituted 6-mers with the V3 loop as well as the CD4 binding site on viral gp120, resulting in anti-HIV-1 activity.

Anti-HIV Agents↗
PubMed1998

GABAergic axon terminals at perisomatic and dendritic inhibitory sites show different immunoreactivities against two GAD isoforms, GAD67 and GAD65, in the mouse hippocampus: a digitized quantitative analysis.

Glutamic acid decarboxylase (GAD), the gamma-aminobutyric acid (GABA)-synthetic enzyme, consists of two isoforms, GAD67 and GAD65. Although distributions of the two GAD isoforms at the somatic level are known to be heterogeneous among different subpopulations of GABAergic neurons, those at the synaptic level have not been investigated. In order to analyze quantitatively the two GAD-isoform immunoreactivities in axon terminals, we combined confocal laser scanning microscopy with digitized image analysis to measure the gray levels of immunofluorescent signals for the two GAD isoforms in a large number of individual boutons in each hippocampal and dentate layer of the mouse. Synaptic boutons exhibited lamina-specific immunoreactivities against the GAD isoforms. Boutons in the principal cell layers (stratum pyramidale of the hippocampus proper and the granule cell layer of the dentate gyrus) showed more intense immunoreactivity against GAD67 than those in the dendritic layers (strata lacunosum-moleculare, radiatum, and oriens of the hippocampus proper and the molecular layer of the dentate gyrus). By contrast, boutons in the dendritic layers showed more intense immunoreactivity against GAD65 than those in the principal cell layers. Such differential distributions could be correlated to the GAD-isoform immunoreactivities in the axon terminals originating from parvalbumin-containing neurons, a particular subpopulation of hippocampal GABAergic neurons mainly innervating the perisomatic domain of principal neurons. In addition to previously reported physiological and pharmacological differences between the GABAergic synapses on perisomatic domain and those on distal dendrites, the present results suggest a functional differentiation of GABAergic synapses between these two inhibitory sites.

Animals↗
PubMed1998

Secretion of tetrain, a Tetrahymena cysteine protease, as a mature enzyme and its identification as a member of the cathepsin L subfamily.

A protease in the culture medium of Tetrahymena pyriformis was purified to homogeneity. The purified protease had an apparent molecular mass of 28 kDa on SDS/PAGE. The amino acid sequences of the N-terminal and internal peptides of the protease showed complete identity with those of tetrain, an enzyme previously reported as a Tetrahymena cysteine protease but not characterized in detail. Two overlapping cDNA clones for tetrain were sequenced, and the nucleotide sequence predicts that these clones encode a 330-amino acid protein composed of a 16-residue N-terminal signal sequence followed by a 103-residue propeptide and a 211-residue mature protease. The primary structure and enzymatic properties support the conclusion that tetrain belongs to the cathepsin L subfamily. Immunoblotting analyses showed that mature tetrain was found exclusively in the culture medium. Immunofluorescence microscopy demonstrated that tetrain was concentrated in or around the food vacuoles of cells in the late logarithmic phase, but the staining of food vacuoles was not obvious in the stationary phase. These results suggest that tetrain is synthesized at the logarithmic phase and is secreted into the culture medium as a mature form.

Amino Acid Sequence↗
PubMed1998

The presenilin 1 mutation (M146V) linked to familial Alzheimer's disease attenuates the neuronal differentiation of NTera 2 cells.

Mutations in presenilin 1 (PS1) gene are the major cause of early-onset familial Alzheimer's disease. The biological functions of PS1 remain elusive, although accumulating evidence suggests that PS1 may play an important role in development and differentiation. To learn about the significance of PS1 in the differentiation of neuronal cells, we established NTera 2 (NT2) cell lines stably expressing wild-type (wt) or M146V mutant human PS1, and compared the differentiation of both types of cell lines into postmitotic neurons upon retinoic acid (RA) treatment. After 25 days of RA treatment, a significant proportion of cells differentiated into neurons in NT2 cells expressing wt PS1 (27.7% of total cells), which was comparable to that in untransfected cells, whereas very few cells differentiated into neurons in NT2 cells expressing M146V mutant PS1 (2.6% of total cells). These results suggest that mutant PS1 attenuates the potentials of NT2 cells to differentiate into neurons.

Alzheimer Disease↗
PubMed1998

Chemically defined neuron groups and their subpopulations in the glomerular layer of the rat main olfactory bulb: III. Structural features of calbindin D28K-immunoreactive neurons.

The present study analyzed three-dimensional structural features and synaptic contacts of morphologically and chemically identified calbindin D28K-immunoreactive neurons in the glomerular layer of the rat main olfactory bulb by means of combined confocal laser scanning light microscopy, high-voltage electron microscopy and electron microscopic serial section/three-dimensional reconstruction. Most of calbindin D28K-immunoreactive neurons were identified as the periglomerular cell type by combined high-voltage electron microscopic and confocal laser scanning light microscopic observations, and the minority were the short-axon cell type and others. The combined confocal laser scanning light microscopic and electron microscopic study revealed that the calbindin D28K-immunoreactive neurons exhibited unique synaptic contact patterns; they received asymmetrical synapses from presumed mitral/tufted dendrites and made conversely symmetrical synapses with them. About 30% of asymmetrical postsynaptic sites and about 40% of symmetrical presynaptic sites formed reciprocal pairs of synapses. Calbindin D28K-immunoreactive dendrites and somata also received synapses from GABA-like-immunoreactive profiles containing numerous pleomorphic, and a few dense-cored, vesicles. On the other hand, surprisingly, calbindin D28K-immunoreactive neurons had almost no synaptic contacts from olfactory nerve terminals. The present study clearly revealed that calbindin D28K-immunoreactive neurons are a type of periglomerular cell involving unique synaptic contacts that have not been reported so far, and thus indicated that so-called periglomerular cells should be heterogeneous in their synaptic connections as well as in their chemical and structural features.

Animals↗
PubMed1998

Effect of Bacillus subtilis spore administration on activation of macrophages and natural killer cells in mice.

The effect of Bacillus subtilis (strain A102) spores on the activation of murine macrophages and natural killer cells (NK) was examined. The macrophage activity and NK activity were enhanced by oral administration of A102 spores, and slightly enhanced by oral administration of culture supernatant. There was no difference in the results of macrophage activity and NK activity using other live or dead spores. The NK activity and macrophage activity were increased with increments of concentration up to 0.1 g per mouse, and both activities were decreased at concentration of more than 0.15 g per mouse. The NK activity was increased 1 and 2 days after oral administration of A102 spores, and the activity level 2 days after administration was about 3-fold higher than the level prior to treatment. Macrophage activity was also increased from 1 to 3 days after oral administration of A102 spores, and the activity level 3 days after administration was about 3-fold higher than the level prior to treatment. The induction of interferons at 1 day after oral administration in mouse serum was 5-fold higher than that in controls. These findings indicate that oral administration of A102 gave rise to the induction of interferons, and it is likely that macrophages and NK cells were activated by interferons.

Animals↗
PubMed1998

Physiological properties of mouse hippocampal mossy cells.

Physiological properties of mouse mossy cells were analyzed in slice preparations and compared with those of mouse CA3 pyramidal cells. They had larger input resistances, less spike-frequency adaptation, more anomalous rectification, larger amplitude spontaneous EPSP and higher frequency of spontaneous EPSP than CA3 pyramidal cells. In these respects, they resembled rat mossy cells. However, in contrast to rat mossy cells, mouse mossy cells showed pronounced burst after-hyperpolarization, comparable to that of CA3 pyramidal cells. This study revealed that mouse mossy cells are distinct from CA3 pyramidal cells in their physiological properties and further suggested that they might be less vulnerable to excitotoxic damage than rat mossy cells, as the burst after-hyperpolarization is supposed to be important in maintaining a neuron in a relatively nonexcited state.

Action Potentials↗
PubMed1998

Longitudinal study of cerebrospinal fluid levels of tau, A beta1-40, and A beta1-42(43) in Alzheimer's disease: a study in Japan.

To clarify the alterations of tau, amyloid beta protein (A beta) 1-40 and A beta1-42(43) in the cerebrospinal fluid (CSF) that accompany normal aging and the progression of Alzheimer's disease (AD), CSF samples of 93 AD patients, 32 longitudinal subjects among these 93 AD patients, 33 patients with non-AD dementia, 56 with other neurological diseases, and 54 normal control subjects from three independent institutes were analyzed by sensitive enzyme-linked immunosorbent assays. Although the tau levels increased with aging, a significant elevation of tau and a correlation between the tau levels and the clinical progression were observed in the AD patients. A significant decrease of the A beta1-42(43) levels and a significant increase of the ratio of A beta1-40 to A beta1-42(43) were observed in the AD patients. The longitudinal AD study showed continuous low A beta1-42(43) levels and an increase of the ratio of A beta1-40 to A beta1-42(43) before the onset of AD. These findings suggest that CSF tau may increase with the clinical progression of dementia and that the alteration of the CSF level of A beta1-42(43) and the ratio of A beta1-40 to A beta1-42(43) may start at early stages in AD. The assays of CSF tau, A beta1-40, and A beta1-42(43) provided efficient diagnostic sensitivity (71%) and specificity (83%) by using the production of tau levels and the ratio of A beta1-40 to A beta1-42(43), and an improvement in sensitivity (to 91%) was obtained in the longitudinal evaluation.

Aged↗
PubMed1998

Gastric cancer occurring in a patient with Plummer-Vinson syndrome: report of a case.

We report herein the unusual case of a 59-year-old woman with Plummer-Vinson syndrome who developed gastric cancer. The patient had a longstanding history of dysphagia and iron deficiency anemia, for which she had sporadically taken iron supplements that improved the dysphagia to some extent, but not completely. Owing to her tolerance of the dysphagia, she had not been taking iron supplements for the past 17 years. On admission, she was in fair nutritional condition and not anemic. Blood chemistry results were all normal, including the serum iron level. Gastrointestinal radiographic series demonstrated cervical esophageal webs and advanced gastric cancer. Her dysphagia was successfully treated by endoscopic bougienage through the webs, and a distal partial gastrectomy with nodal dissection was performed. Histology of the resected stomach revealed atrophic mucosal change and, by chance, an adenomatous lesion in addition to adenocarcinoma. Her postoperative course was uneventful and she is now well, without any signs of recurrence. Although Plummer-Vinson syndrome is known to be associated with upper alimentary tract cancers, gastric cancer is extremely rare. A discussion on the etiology of Plummer-Vinson syndrome and its link with potential carcinogenesis follows this case report.

Adenocarcinoma↗