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Biomedical subjects

K Yoshikawa

Publications and source records attributed to K Yoshikawa.

At least 109 records · Page 6Linked to original sources
PubMed2000

Caspase-3 activation and inflammatory responses in rat hippocampus inoculated with a recombinant adenovirus expressing the Alzheimer amyloid precursor protein.

To elucidate the mechanism of neuronal death in Alzheimer's disease, we investigated the effects of overexpression of wild-type Alzheimer amyloid precursor protein (APP) on neuronal cells and glial cells in vivo. When an APP695-expressing adenovirus was injected into the dorsal hippocampal region, a number of neurons in remote areas were positively stained with anti-APP monoclonal antibody, and underwent severe degeneration from 3 to 7 days after viral inoculation. Most degenerating neurons were immunopositive with both APP and activated caspase-3, but some neurons that expressed activated caspase-3 were not expressing APP from 7 to 14 days after virus injection. In the neighborhood of the degenerating neurons, activated microglia/macrophages, which were identified by the phenotypic marker C3bi receptor (CD11b/c; OX-42), were observed, and some of them appeared to phagocytose the caspase-3-immunopositive degenerating neurons. In addition to microglia/macrophages, infiltrating leukocytes expressing CD45 or CD4 were also detected. These results suggest that the increased accumulation of APP induced not only caspase-3-mediated death machinery, but also inflammatory responses including microglial activation. These inflammatory responses might cause further neurodegeneration through the alternative pathway that might activate the caspase-3-mediated death machinery without APP expression.

Adenoviridae↗
PubMed2000

Activation of fibroblast-derived matrix metalloproteinase-2 by colon-cancer cells in non-contact Co-cultures.

Stromal fibroblasts interact with invading cancer cells by secreting and activating matrix metalloproteinases (MMPs). To elucidate the mechanisms involved in the expression and activation patterns of MMPs, human colon-cancer cell lines Caco-2 and LoVo and colon-fibroblast cell line CCD18-Co were co-cultivated in non-contact and contact conditions which mimic in vivo interaction between cancer cells and fibroblasts before and after cancer invasion respectively. Gelatin zymography disclosed that MMP-2 was secreted from the fibroblasts but not from the cancer cells. The quantity of fibroblast-derived MMP-2 in conditioned medium was not significantly changed in either the contact or the non-contact co-cultures when compared with that of individual cultures of CCD18-Co fibroblasts. Cancer cells in non-contact co-cultures, however, enhanced the activation of fibroblast-derived MMP-2. Transcripts of membrane-type matrix metalloproteinase-1 (MT1-MMP), which is thought to be present on the cell surface and to work as a candidate activator of MMP-2, were detected in both cancer cell lines. Plasma membrane extracts of cancer cells also activated MMP-2 in conditioned media in cell-free conditions. This activation of MMP-2 may be caused by MT1-MMP of the cancer cells, since it was inhibited by a series of MMP inhibitors, including ethylenediaminetetraacetic acid (EDTA), the tissue inhibitor of metalloproteinase-2 (TIMP-2), and the MMP inhibitor CGS 27023A, but not by TIMP-1. Our data demonstrate that in non-contact co-cultures colon-cancer cells activate fibroblast-derived MMP-2 on their plasma membranes. These findings should help to elucidate the mechanism involved in the initial destruction of basement membrane by cancer cells.

Basement Membrane↗
PubMed2000

Disrupted transforming growth factor-beta signaling and deregulated growth in human biliary tract cancer cells.

Biliary tract carcinoma is a common neoplasm in Japan, and its treatment is difficult because it tends to promote fibrosis and easily invades surrounding tissues. To better characterize the biological features of this carcinoma, we investigated abnormalities in the transforming growth factor-beta (TGF-beta) signaling pathway in five human biliary tract cancer cell lines: RBE, KMBC, SK-ChA-1, Mz-ChA-1, and Mz-ChA-2. We stably transfected into these cells the luciferase reporter plasmid carrying promoter of the plasminogen activator inhibitor-1 gene, the expression of which is stimulated by TGF-beta1. Treating the KMBC and Mz-ChA-1 cells with TGF-beta1 neither inhibited cell growth nor stimulated luciferase activity. In contrast, the RBE and Mz-ChA-2 cells responded well to TGF-beta1 treatment. TGF-beta1-treated SK-ChA-1 cells exhibited attenuated luciferase activity and their growth was not inhibited. Smad4 mRNA was not detected in SK-ChA-1 and Mz-ChA-1 cells by Northern blot analysis. Genetic analysis disclosed a nonsense mutation in the Mad homologue 2a domain of the Smad4 gene in the SK-ChA-1 cells and a heterozygous deletion in the TGF-beta type II receptor gene in the KMBC cells. Expression of the exogenous Smad4 gene in the Mz-ChA-1 cells by transient transfection restored their luciferase activity. When these TGF-beta1-insensitive and less-TGF-beta1-sensitive cell lines were xenografted into nude mice, they developed tumors that had more prominent, intervening fibrosis (desmoplasia) than the tumors caused by TGF-beta1-sensitive cells. Thus, a tight correlation between disruption of the TGF-beta signaling pathway and deregulated growth of cancer cells has been demonstrated in biliary tract carcinoma. This seems to be a critical event in this carcinoma and may also be correlated with stromal cell reaction in cancer invasion.

Animals↗
PubMed2000

Somatosensory evoked potentials to a threshold air-puff can predict stimulus detection in human subjects.

Somatosensory evoked potentials (SEPs) and reaction time (RT) were studied following a threshold intensity air-puff stimulation of the skin in nine subjects. We delivered brief air-puffs, at the threshold intensity of about 50% detection probability, to the volar surface of the right hand at the base of the index finger. The SEPs were averaged separately for detected and undetected stimuli. Prior to the SEP data collection, RTs to the same intensity threshold stimulus were measured. P300 SEP late component was recorded in response to detected stimuli and was not to undetected stimuli. However, in one subject, P300 was associated with undetected stimuli, suggesting errors in the psychophysical task. The peak latency of P300 was 316+/-29 ms (mean+/-SD) and earlier than the average RT (390+/-43 ms). These results demonstrate that SEPs can correctly predict perception of the threshold air-puff stimulus.

Adolescent↗
PubMed2000

Characterization and chromosomal mapping of a human Necdin pseudogene.

The necdin gene is expressed predominantly in postmitotic neurons and encodes a growth suppressor that interacts with the transcription factors E2F1 and p53. Human necdin gene (NDN) is maternally imprinted and located in Prader-Willi syndrome deletion region 15q11.2-q12. We isolated an NDN homologous sequence from a human genomic DNA library. The homologous sequence is overall 83% identical with necdin cDNA sequence, and possesses a short poly(A) stretch at the 3' end and direct repeats at both ends. Expression of the homologous sequence, which lacks a 5' promoter sequence, was undetected in cultured human cell lines. We mapped this sequence to chromosome 12q14-q21.1 by fluorescence in situ hybridization. These characteristics of the NDN-homologous sequence are consistent with those of processed pseudogenes. The information about the necdin pseudogene in the human genome will be useful for genetic studies on NDN-associated neurogenic disorders.

Base Sequence↗
PubMed2000

Analysis of all exons of TSC1 and TSC2 genes for germline mutations in Japanese patients with tuberous sclerosis: report of 10 mutations.

Twenty-seven Japanese patients with the tuberous sclerosis complex (TSC), consisting of 23 sporadic and 4 familial cases, were tested for mutations in the TSC1 and TSC2 genes, using single-strand conformational polymorphism analysis and direct sequencing. Four possible pathogenic mutations were found in the TSC1 gene, including three frame shifts and a nonsense mutation in a familial case. All mutations were expected to result in a truncated hamartin gene product. The TSC2 gene analysis identified six possible pathogenic mutations only in the sporadic cases, including two frame shifts, one in-frame deletion, and three missense mutations. Two of the TSC2 mutations were expected to result in a truncated tuberin gene product. These results of the Japanese TSC patients were compatible with the reports from Europe and the United States, i.e., (1) TSC1 mutations are rarer in sporadic cases than in familial cases, (2) substantial numbers of sporadic cases arise from mutations in the TSC2 gene, and (3) mutations of the TSC1 gene may cause premature truncation of hamartin.

Adolescent↗
PubMed2000

A case of monoclonal gammopathy associated with acute myelomonocytic leukemia with eosinophilia suggested to be the result of lineage infidelity.

Acute myelomonocytic leukemia (AMMoL) accompanied by monoclonal gammopathy is a rare condition, and its pathogenesis and the cytogenetic mechanism of such leukemogenesis have not been determined in detail. A case of AMMoL with eosinophilia accompanied by immunoglobulin G kappa monoclonal gammopathy is described. Immunophenotypic studies of the peripheral blood and bone marrow mononuclear cells revealed no evidence of abnormally proliferating cells of B-lineage. DNA analyses of bone marrow mononuclear cells containing leukemic cells revealed rearrangement of the kappa-light chain (Igkappa) gene and c-myc and c-jun proto-oncogenes. The intensities of the rearranged bands for these genes on Southern blot analysis suggested the existence of a major population of leukemic cells with rearranged Igkappa gene and minor population(s) of leukemic cells with rearranged c-myc and/or c-jun proto-oncogene(s) in the patient's bone marrow and indicated the occurrence of genetic evolutionary changes in leukemic cells in this patient before starting chemotherapy. These results suggest that these leukemic cells are the most likely candidate for immunoglobulin G kappa monoclonal protein production, and structural abnormalities of c-myc and c-jun proto-oncogenes may have contributed to the evolution of leukemic cells in this patient.

Blotting, Southern↗
PubMed2000

Estimation of 99mTc-MAG3 clearance by single-sample methods and camera-based methods.

We compared single-sample methods, proposed by Russell et al. and Bubeck et al., and camera-based methods in calculating 99mTc-MAG3 clearance, and determined camera-based methods that provide estimates comparable to those measured by the Russell method. Twenty-one patients underwent 99mTc-MAG3 renal scintigraphy, and clearance was measured by the Russell method and Bubeck method. Various renogram parameters were determined based on the slope of the renogram and area under the renogram, and correlated with the clearance measured by the Russell method. Camera-based clearance was calculated with the obtained regression equations and with equations determined previously using the Bubeck method as a standard. The Bubeck method provided lower measures than the Russell method in high renal function. Clearance measured by the Russell method was well correlated with renogram parameters, and clearance calculated with the obtained regression equation was comparable to that measured by the Russell method. When camera-based clearance was predicted with the previous equation, it was lower than the result obtained by the Russell method in high function. In conclusion, there are systematic differences in 99mTc-MAG3 clearance calculated by different methods. The camera-based methods obtained in this study appear to facilitate comparison of results obtained by the Russell method and camera-based method.

Adult↗
PubMed2000

Immune gene therapy of experimental mouse brain tumor with adenovirus-mediated gene transfer of murine interleukin-4.

We examined the antitumor activity of replication-deficient adenoviral vectors carrying the murine interleukin-4 (IL-4) gene (AdCIL4) using a syngeneic brain tumor model in mice. Mice implanted with malignant astrocytoma cells infected with AdCIL4 survived significantly longer than those in the control groups. Immunocytochemical analysis of the tumors showed that AdCIL4 caused the strong up-regulation of MHC class II antigen expression by the tumor cells and macrophages, and consequent infiltration by CD8+ T lymphocytes. This study demonstrates the efficacy of IL-4 gene transfection mediated by adenoviral vectors for intracerebral tumor and characterizes the immunoreaction caused by AdCIL4.

Adenoviridae↗
PubMed2000

Vitamin B6 phototoxicity induced by UVA radiation.

We have previously reported that pyridoxine shows UVA-induced cytotoxicity. Four other vitamin B6 compounds (pyridoxal, pyridoxamine, pyridoxal phosphate, and pyridoxamine phosphate) are metabolically more important in vivo than pyridoxine. These compounds were examined for UVA phototoxicity to cultured human fibroblasts. The cytotoxicity was measured by post-UVA irradiation colony-forming ability. All the B6 compounds except pyridoxal phosphate showed cytotoxicity. Pyridoxamine phosphate, which is the most important form of vitamin B6 in vivo, had the strongest cytotoxic effect. To examine the involvement of reactive oxygen species in the phototoxicity, we performed an electron spin resonance study using the spin trapping agent, 5,5-dimethyl-1-pyrroline N-oxide, and diethylenetriaminepentaacetic acid. We failed to detect radicals derived from vitamin B6. The cytotoxic effect remained in UVA-irradiated solutions for at least 30 min after the end of UVA irradiation. Hydrogen peroxide was produced in the solution, but the amount was not enough to cause cytotoxicity. In addition, the cells from xeroderma pigmentosum patients who belong to group A or C showed survival curves similar to those of normal fibroblasts. This suggests that cyclobutane pyrimidine dimers or 6-4 photoproducts of DNA were not involved in this damage. These findings suggest that UVA-induced vitamin B6 cytotoxicity is caused by toxic photoproducts resulting from irradiated vitamin B6.

Cell Line↗
PubMed2000

Involvement of insulin-like growth factor-I in psoriasis as a paracrine growth factor: dermal fibroblasts play a regulatory role in developing psoriatic lesions.

To investigate the contribution of dermal fibroblasts to the development of psoriasis, we examined the expression of mRNA for insulin-like growth factor-I (IGF-I) and its regulator IGF-I binding proteins (IGFBPs) in psoriatic fibroblasts by RT-PCR. We also studied the effect of inflammatory cytokines including interferon gamma (IFN-gamma), tumor necrosis factor alfa (TNF-alpha), and IFN-alpha on the expression of IGF-I and IGFBPs in the fibroblasts. Semiquantitative analysis revealed that IGF-I mRNA expression in psoriatic fibroblasts (PF) was significantly higher than in control fibroblasts (CF). However, no significant difference in IGF-I mRNA was shown between nonlesional psoriatic fibroblasts (NF) and CF. Treatment with IFN-alpha in vitro upregulated IGF-I mRNA in PF and in CF. TNF-alpha appeared to downregulate IGF-I mRNA in PF but had no effect on CF. IFN-gamma did not show a significant effect on IGF-I mRNA levels in any type of fibroblast. IGFBP-3 mRNA was expressed equally in PF and CF, and was not affected by cytokines. The expression of IGFBP-5 mRNA in PF was downregulated by IFN-gamma and TNF-alpha. Taken together, these results indicate that dermal fibroblasts may contribute to the epidermal hyperplasia of psoriasis by promoting keratinocyte proliferation through IGF-I, whose secretion could be modulated by inflammatory cytokines.

Adolescent↗
PubMed2000

Neural substrates for the recognition of newly learned faces: a functional MRI study.

Face recognition is critical to the appreciation of our social and physical relations. Functional magnetic resonance imaging (fMRI) was used to identify brain regions involved in the recognition of newly learned faces. Two experiments were conducted. Experiment 1 contrasted a fixation control task with a face recognition task in which subjects were exposed solely to previously viewed faces (all-target). Experiment 2 compared a fixation control with another face recognition task in which subjects were presented with both novel and viewed faces (half-target). Compared to the fixation control, the all-target face recognition was associated with activation in the bilateral occipital and occipitotemporal regions, whereas the half-target face recognition produced activation in the right parietal and prefrontal regions, in addition to the occipital and occipitotemporal. The all-target minus half-target comparison revealed significant activation in the bilateral fusiform gyrus, suggesting stronger fusiform activity during the all-target than the half-target face recognition. The half-target minus all-target comparison showed significant activation in the superior and inferior parietal lobules and several regions in the right frontal lobe. These findings demonstrated that the bilateral fusiform gyrus is involved, not only in face perception, but in a certain aspect of face recognition memory and that this aspect is related to the actual recognition of previously viewed faces rather than the processing of novel ones, which results are consistent with previous lesion work. The right parietal and frontal regions, in contrast, are differentially more associated with the processes related to the detection of novel faces or retrieval effort.

Adult↗
PubMed2000

Cell cycle regulators in neural stem cells and postmitotic neurons.

In the mammalian central nervous system, neurons withdraw from the cell cycle immediately after their differentiation from proliferative neuroepithelial cells. Even while postmitotic neurons remain in permanent mitotic quiescence, they express a number of cell cycle regulators required for cell cycle progression. This review focuses on the expression and functions of members of the retinoblastoma protein (Rb) family (Rb, p107, p130) and necdin, all of which are growth suppressors that interact with the viral oncoproteins and the E2F family proteins. These molecules are differentially expressed in proliferative neural progenitors and postmitotic neurons in the developing neuroepithelium in vivo and differentiating embryonal carcinoma cells in vitro. During neurogenesis, dysfunction of the Rb family proteins causes impaired neuronal differentiation accompanied by cell death (apoptosis). Thus, the Rb family proteins are essential for both terminal mitosis of neuronal progenitors and survival of nascent neurons. However, the Rb family proteins seem to be dispensable for the maintenance of the postmitotic state of terminally differentiated neurons. Necdin is expressed exclusively in postmitotic cells and may contribute to their permanent mitotic arrest. These cell cycle regulators coordinately act in the generation, survival and demise of postmitotic neurons.

Animals↗
PubMed2000

A synthetic peptide of human apoprotein E with antibacterial activity.

In recent years, several endogenous mammalian antibacterial peptides have been described. An amphipathic cationicalpha-helix is a common feature in many cases; therefore, other peptides with this characteristic might also possess antibiotic activity. In fact, a 30-mer peptide of apoprotein E 133-162 (LRVRLASHLRKLRKRLLRDADDLQKRLAVY) was found to have antibiotic activity comparable to those of a classic antibiotic (Gentamicin) and a neutrophil-derived antibiotic peptide (CAP18). Calculation of cationicity, hydrophobicity, and hydrophobic moment and the helical wheel diagram of apoprotein E 133-162 revealed close similarities to CAP18.

Amino Acid Sequence↗
PubMed2000

Local adenovirus-mediated CTLA4-immunoglobulin expression suppresses the immune responses to adenovirus vectors in the brain.

The effect of local administration of two adenovirus vectors, one of which expressed CTLA4-immunoglobulin (AdCTLA), which blocks the B7-CD28 co-stimulatory pathway of T cell activation in the inflammatory response to adenovirus vectors was investigated. Mice injected with AdCTLA and an E1-deleted adenovirus vector that encodes the lacZ gene (AdRL) into the brain showed inflammatory cell infiltration from the early phase until day 6 after injection that was not different from that seen in control mice injected with an E1-deleted adenovirus vector containing no transgene (Ad0) and AdRL. After day 6 the inflammation in the control mice increased, peaked by day 15 and then decreased gradually but persisted until day 60. By contrast, in mice treated with AdCTLA and AdRL the inflammation, especially T cell infiltration, was suppressed after day 15. The anti-adenovirus antibody titer increased gradually until day 60 in the Ad0-AdRL control group, and whereas the mice injected with AdCTLA and AdRL showed lower anti-adenovirus antibody titers than the control group mice after day 15. Neutralizing antibody was not detected in either group. Expression of beta-galactosidase, the gene product of AdRL, at the injection site in the striatum and corpus callosum peaked on day 6 and remained until day 60 although it was very low in both groups; beta-galactosidase expression was similar in the two groups in spite of the difference in the degree and extent of the local immune response in the brain. This study demonstrated that the injection of an adenovirus vector expressing CTLA4-immunoglobulin into the brain suppressed not only local cell infiltration in the brain but also reduced the humoral immune response to adenovirus vectors.

Abatacept↗
PubMed2000

Genetic factors in immunosuppression: precise genetic evidence that polymorphism of TNF-alpha dictates UVB-susceptibility in mice.

Acute low-dose treatment of murine skin with ultraviolet B (UVB) light impairs induction of contact hypersensitivity (CH) to dinitrofluorobenzene (DNFB) in certain inbred strains of mice (termed UVB-susceptible), but not in others (termed UVB-resistant). These deleterious effects of ultraviolet radiation (UVR) are mediated in part by TNF-alpha, which is released from UVR-exposed epidermal and dermal cells. To test the hypothesis that polymorphism of TNF-alpha governs the phenotype of UVB-susceptibility in vivo, various strains of mice received UVB radiation followed by hapten application to induce contact hypersensitivity. Results suggest that the polymorphism at the Tnf-alpha locus dictates UVB susceptibility in vivo.

Animals↗
PubMed2000

Morphological changes in mouse accessory sex glands following neonatal estrogen treatment.

A single injection of beta-estradiol 17-cypionate into the mice within 5 hr after birth induced inflammation in all prostate lobes and the seminal vesicles. Neutrophils emigrated into the lumen through the basal lamina and epithelium of the seminal vesicle and the anterior prostate. Local infiltration of lymphocytes was observed in the stroma and epithelium of ventral prostates. Lymphocytes penetrated through smooth muscle cells into epithelium. This could support the hypothesis that smooth muscle cells are the target of the estrogen action of prostates in estrogenized animals.

Animals↗