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Biomedical subjects

Y Ikawa

Publications and source records attributed to Y Ikawa.

At least 91 records · Page 5Linked to original sources
PubMed1995

Infrequent mutations of the WT1 gene in primary cancers of the adult urinary tract.

Polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis of all of the ten exons of the WT1 gene and restriction fragment length polymorphism (RFLP) analysis of the WT1 locus were performed on primary urinary tract cancers: seven renal pelvic cancers, one ureteral cancer, 11 bladder cancers, and 22 renal cell cancers. Four human bladder cancer cell lines (T24, JTC30, JTC32, and HUB41) and three human prostate cancer cell lines (PC-3, DU145, and LNCaP) were also examined. None of the primary cancers showed any apparent mutations of the gene, whereas one base substitution of exon 5 was found in DU 145 and gross alteration of the gene was recognized in HUB41. Heterozygosity of polymorphic exon 7 was retained in all of the 12 informative cases, and none of 10 informative cases showed loss of heterozygosity at the WT1 locus in RFLP analysis. It is concluded that mutations of the WT1 gene may not be involved in the formation of malignant tumors of the adult urinary tract.

Adult↗
PubMed1994

Activated Ki-Ras complements erythropoietin signaling in CTLL-2 cells, inducing tyrosine phosphorylation of a 160-kDa protein.

We have previously shown that expression of erythropoietin (EPO) receptor (EPOR) alone failed to confer EPO responsiveness on the interleukin 2-dependent T-cell line CTLL-2, whereas the introduction of the EPOR into interleukin 3-dependent pro-B-cell lines, such as BAF-B03, allowed the cells to proliferate in response to EPO. Here, we report that additional expression of v-Ki-Ras conferred EPO-dependent growth on CTLL-2 cells expressing the EPOR, with additional formation of a high-affinity EPOR. To investigate possible mechanisms of EPOR downstream signaling induced by v-Ki-Ras expression in these CTLL-2-derived cells, we carried out anti-phosphotyrosine immunoblot analysis of the EPOR complex immunoprecipitated with anti-EPOR antibody from lysates of cells with and without cytokine stimulation, revealing two 160-kDa and 130-kDa phosphotyrosyl proteins. An anti-JAK2 antibody did not react with these proteins, suggesting that they may represent cellular components involved in an EPO-EPOR signaling pathway induced by v-Ki-Ras. Similar phosphotyrosyl proteins were present among Friend erythroleukemia cell lines, in which the Friend virus gp55/EPOR complex on the cell surface constitutively sends signals for cell growth.

Cell Division↗
PubMed1994

Increased UV-induced SCEs but normal repair of DNA damage in p53-deficient mouse cells.

UV-induced sister chromatid exchanges (SCEs) in p53-deficient mouse cells were studied to obtain more evidence regarding the involvement of p53 protein in the DNA repair pathway as a checkpoint protein. After 5 J/m2 UV irradiation, mutant-type homozygous cells for p53-deficiency showed the same number of SCEs as the heterozygous and wild-type homozygous cells. In the heterozygous and wild-type homozygous cells, no further increase of SCEs was observed after 10 J/m2 UV irradiation. In contrast, in mutant-type homozygous cells about twice as many SCEs were induced by 10 J/m2 UV as by 5 J/m2 UV. In mutant-type homozygous cells, fractions of S-phase cells decreased just after 10 J/m2 UV irradiation, but recovered to higher than control levels within a short time, while in heterozygous and wild-type homozygous cells, the decrease in S-phase cells was prolonged by more than 6 hr and no increase above control levels was observed. Although no difference in UV sensitivity and repair of UV-induced DNA damage was found among the 3 genotypes, which were determined by the relative colony-forming ability after UV irradiation and removal of thymine dimers and (6-4) photoproducts from cellular DNA, our data strongly suggest an impaired checkpoint function in p53-deficient cells when DNA is damaged.

Animals↗
PubMed1994

Parthenogenetic activation of oocytes in c-mos-deficient mice.

In Xenopus the c-mos proto-oncogene product (Mos) is essential for the initiation of oocyte maturation, for the progression from meiosis I to meiosis II and for the second meiotic metaphase arrest, acting as an essential component of the cytostatic factor CSF. Its function in mouse oocytes is unclear, however, as is the biological significance of c-mos mRNA expression in testes and several somatic tissues. We have generated c-mos-deficient mice by gene targeting in embryonic stem cells. These mice grew at the same rate as their wild-type counterparts and reproduction was normal in the males, but the fertility of the females was very low. The c-mos-deficient female mice developed ovarian teratomas at a high frequency. Oocytes from these females matured to the second meiotic metaphase both in vivo and in vitro, but were activated without fertilization. The results indicate that in mice Mos plays a role in the second meiotic metaphase arrest, but does not seem to be essential for the initiation of oocyte maturation, spermatogenesis or somatic cell cycle.

Animals↗
PubMed1994

Bovine leukemia virus induces CD5- B cell lymphoma in sheep despite temporarily increasing CD5+ B cells in asymptomatic stage.

To investigate bovine leukemia virus (BLV)-induced leukemogenesis, we infected sheep with BLV and used flow-cytometric and immunohistological analysis to characterize the phenotypic alterations in lymphocytes from peripheral blood and lymph nodes taken from the animals with lymphoma at various stages. In sheep at the asymptomatic stage, depending on the extent of progression of the disease, the proportions of CD2(+)-, CD4(+)-, CD8(+)-, and gamma delta TCR(+)-T cells that coexpressed CD5 decreased, but CD5+ sIgM+ cells as well as CD5- sIgM+ cells increased for a period. The number of CD5+ B cells, however, rapidly decreased in the lymphoma stage. On the other hand, neoplastic lymphocytes appeared to be a monoclonal population derived from a single cell with surface phenotypes of sIgM+, B-cell-specific molecule B2+, major histocompatibility complex (MHC) class II+, OvCD5-, OvCD2-, OvCD4-, OvCD8-, gamma delta TCR-, which suggests that only CD5- B cells proliferate clonally when the disease proceeds to the lymphoma stage. Thus, rapid decrease of CD5+ B cells may be used as a marker of lymphoma stage. To identify the BLV provirus in the CD5- B and CD5+ B cells throughout the course of disease, each fraction of CD5- B and CD5+ B cell was sorted from the peripheral blood by flow cytometry and nested double polymerase chain reaction was performed. In BLV-infected but healthy sheep, BLV integrated both CD5- B and CD5+ B cells. In lymphoma, however, BLV provirus was detected only in CD5- B cells but not in CD5+ B cells. Therefore it appears that a disappearance of BLV-infected CD5+ cells is one of the critical events leading to CD5- B cell lymphoma in sheep. This is in contrast to the BLV-induced lymphoma in cattle which shows CD5+ phenotype.

Animals↗
PubMed1994

Molecular cloning of P-type ATPases on intracellular membranes of the marine alga Heterosigma akashiwo.

Two cDNA clones (HAA13 and HAA1) which include conserved regions of genes of P-type ATPases were isolated from the marine alga Heterosigma akashiwo by a method that included the polymerase chain reaction. The longer cDNA (3286 bp), HAA13, consisted of an open reading frame that encoded a 106 kDa polypeptide of 977 amino acids with several possible transmembrane domains and conserved regions of eukaryotic P-type ATPases. One transmembrane domain had a leucine zipper structure. HAA1 was not a full-length gene (2054 bp) and lacked the 5' region, but it also included the conserved regions and putative transmembrane domains. Antibodies against the regions and putative transmembrane domains. Antibodies against the polypeptides encoded by HAA13 and HAA1 that have been expressed in Escherichia coli reacted with 100 kDa and 95 kDa polypeptides, respectively, on intracellular membranes of H. akashiwo cells. Immunostaining of H. akashiwo cells revealed that the HAA13 antigen was distributed on membranes around chloroplasts and the HAA1 antigen was located on small vesicles.

Adenosine Triphosphatases↗
PubMed1994

Effect of endothelin-1 as growth factor on a human glioma cell line; its characteristic promotion of DNA synthesis.

In addition to its powerful vasoconstrictive activity, endothelin-1 (ET-1) has been recognized to stimulate DNA synthesis in some cell lines. In this study, we confirmed the existence of ET-1 receptor in YKG-1 human glioma cells, and investigated its effect on DNA synthesis in YKG-1 for 6 consecutive days, comparing it with that of epidermal growth factor (EGF), platelet-derived growth factor (PDGF), and insulin-like growth factor-I (IGF-I). Scatchard analysis of the binding data revealed the presence of a single class of high-affinity binding molecule. The apparent dissociation constant (Kd) was 5.2 x 10(-9) M and the maximal binding capacity (B max) was 4.7 x 10(4) sites/cell. The percentage of non-cycling cells was initially more than 85%, and decreased to 55.40%, 24.22%, 11.50%, and 7.51% on days 1, 2, 4, and 6, respectively, after ET-1 stimulation. Although ET-1 reduces the fraction of non-cycling cells more slowly than other growth factors such as EGF, PDGF and IGF-I, it reaches the same level as the others by day 6. These results indicate that YKG-1 human glioma cells have ET-1 receptors and that ET-1 initiates a peculiar slow induction of DNA synthesis in these cells, suggesting that secondary factors might exist to accelerate the DNA synthesis in response to ET-1.

Cell Cycle↗
PubMed1994

A novel nonreceptor tyrosine kinase, Srm: cloning and targeted disruption.

We have isolated a novel nonreceptor tyrosine kinase, Srm, that maps to the distal end of chromosome 2. It has SH2, SH2', and SH3 domains and a tyrosine residue for autophosphorylation in the kinase domain but lacks an N-terminal glycine for myristylation and a C-terminal tyrosine which, when phosphorylated, suppresses kinase activity. These are structural features of the recently identified Tec family of nonreceptor tyrosine kinases. The Srm N-terminal unique domain, however, lacks the structural characteristics of the Tec family kinases, and the sequence similarity is highest to Src in the SH region. The expression of two transcripts is rather ubiquitous and changes according to tissue and developmental stage. Mutant mice were generated by gene targeting in embryonic stem cells but displayed no apparent phenotype as in mutant mice expressing Src family kinases. These results suggest that Srm constitutes a new family of nonreceptor tyrosine kinases that may be redundant in function.

Amino Acid Sequence↗
PubMed1994

Role of cell-mediated immunity in bovine leukemia virus (BLV) infection in ruminants: its implication for the vaccination strategy against retroviruses.

Recent studies in the immunopathogenesis of bovine leukemia virus (BLV) infection in ruminants, reviewed herein, provide an insight into the vaccination strategy against retrovirus infection. It was shown that vaccination of naive sheep with a recombinant vaccinia virus (RVV) expressing BLV envelope glycoprotein protected the animals against BLV infection. The involvement of cell-mediated immunity (CMI) in this phenomenon was strongly suggested. The postinfection vaccination, that is, the vaccination of BLV-infected animals with RVV, also significantly suppressed BLV replication in the carrier animals. These findings support the idea that vaccination against retroviruses should put its emphasis on the induction of CMI and that such vaccine could be used not only for prophylactic but also for therapeutic purposes.

Animals↗
PubMed1994

Fyn expression during early neurogenesis in mouse embryos.

Fyn is a member of the Src family of tyrosine kinases which are thought to play important roles in cell to cell interactions during morphogenesis. The developmental profile of Fyn expression was examined using mutant mice in which lacZ gene was introduced into this locus. The expression was characteristic in the neural system. Though at low levels, it was detected in the headfold at embryonic day (E) 7.5 and in the luminal surface of neuroectoderm along the entire neural groove at E8.5. The expression appeared regional in rhombomeres at E8.5 and E9.5. Consistent expression was also found at a low level in the notochord. The expression was high in later stages of the neural tube which consists of three layers; it was in the marginal layer but not in the germinal layer. High expression was also found in developing dorsal root filaments of neural crest origin. Non-expression in dividing neuroepithelial cells and expression in developing neural fibers appeared ubiquitous features of Fyn expression throughout the entire brain.

Animals↗
PubMed1994

Immunopathologic study and characterization of the phenotype of transformed cells in sheep with bovine leukemia virus-induced lymphosarcoma.

We used monoclonal antibodies and immunohistologic examination of lymph nodes, to elucidate the pathogenesis of lymphosarcoma induced by infection with bovine leukemia virus (BLV). The superficial cervical lymph nodes from 3 BLV-infected but apparently healthy sheep and 5 sheep with full-blown lymphosarcoma were examined. We also investigated the integration of bovine leukemia provirus by use of Southern blotting. In lymph nodes from sheep lacking clinical signs of infection, in which the provirus had been integrated at multiple sites in the genome, many large hypertrophic follicles were observed in the cortex. These follicles had germinal centers consisting of CD4+T cells and B cells that expressed surface IgM (sIgM) and major histocompatibility complex (MHC) class-II antigens, but not B cell-specific B2 molecule. The percentage of CD4+T cells in the cortex was significantly (P < 0.05) higher than that of the controls and sheep with lymphosarcoma. In all sheep with lymphosarcoma, the lymph nodes were completely destroyed by proliferating neoplastic cells, and in addition, small atrophic follicles, which consisted of normal B-cell marker-positive cells, were seen near the trabecula and the subcapsule. In these instances, neoplastic cells appeared to be a monoclonal population derived from a single CD5- B-cell lineage and to be classified as 2 types, CD5-CD4-CD8-B2+MHC class-II+sIgM+ and CD5-CD4-CD8-B2+MHC class-II+sIgM-. Moreover, CD8+T cells infiltrated diffusely throughout the tumorous lymph nodes apart from the atrophic follicles, and CD4+ cells were observed around atrophic follicles. Both types of T cells were small-size, normal lymphocytes with round and noncleaved nuclei, and were apparently non-neoplastic cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Erythropoietin receptor and interleukin-2 receptor use different downstream signaling pathways for proliferation and apoptosis-block.

Erythropoietin (EPO) regulates proliferation and differentiation and prevents apoptosis of erythroid progenitor cells by binding to erythropoietin receptor (EPOR) expressed on the surface of those cells. The mechanism by which EPO signal is transmitted to the cells through EPOR is still unclear. In the present study, we introduced and expressed EPOR in an interleukin-3 (IL-3) dependent pro-B cell line, BAF-B03 and an interleukin-2 (IL-2)-dependent cytotoxic T cell line, CTLL-2 and analyzed their growth response to EPO and the DNA breakdown characteristic to apoptosis after deprivation of the growth factor. BAF-B03-derived cells expressing EPOR proliferated in response to EPO but CTLL-2-derived cells expressing EPOR (C/EPOR) did not. DNA from C/EPOR cells cultured in the absence of IL-2 with or without EPO had similar patterns of DNA breakdown. These results suggest that downstream signaling pathways for the cell proliferation and apoptosis-block are, at least, partially different between EPOR and IL-2 receptor (IL-2R).

Animals↗
PubMed1994

Experimental model for MDS-like myelodysplasia in transgenic mice harboring the SV40 large-T antigen under an immunoglobulin enhancer.

The SV40 large T gene under the control of immunoglobulin enhancer induced hyperproliferation of multi-lineage hematopoiesis in transgenic mice. Hence the disease has been considered to be an appropriate experimental model for MDS-like myelodysplasia, sequential pathological changes in the development of the disease are introduced in the report. Huge splenomegaly was the major gross abnormality, which developed with 100% frequency; neither hepato-renal, nor other thymico-lymphatic involvement was common. During the progressive increase in splenic weight, extensive proliferation of multi-lineage hemopoiesis was prominent, although no differences were apparent in the cellular proportions of each hematopoietic element compared with normal spleens, either in flow-cytometric analysis using markers for each subset of hematopoietic elements, or in the histological findings. In the later phases of the disease, the proliferating cell type tended to shift to a variety of single to oligo-lineage hemopoiesis, but the majority of mice still showed the presence of multi-lineage hemopoiesis; histologically, such hemopoiesis was somewhat dysplastic, but had no apparent nature of leukemic infiltration. Several transplantation-assays essentially supported the low neoplastic potential of proliferating cells even in later phase. A long-term observation was made aiming to induce more frequent transition of this abnormal hemopoiesis into a single-lineage neoplasm by transplantation of pre-onset spleen cells, as well as bone-marrow cells from transgenic mice at an early phase of the disease, into lethally irradiated C57BL/6 mice. This trial resulted in a variety of neoplastic growths in the recipients; not only was myelodysplastic hypercellularity seen, but also, single-lineage hemopoietic malignancies, such as B-cell lymphomas/leukemias, histiocytic malignancies, and even myeloid leukemias. The transition from multi-lineage myelodysplasia into single lineage hemopoiesis at some frequency is reminiscent of myelodysplastic syndromes (MDS) in humans. Higher frequency of transition into lymphoid malignancies may be due partly to the immunoglobulin enhancer used as a promoter unit. The results that the SV40 large T antigen was expressed in every proliferating cells, there was no apparent increase in multi-CSFs activity; together with the results of the transplantation assays suggest that the hyperproliferation of the cells is directly induced by the expression of SV40 large T antigen in the hemopoietic cells themselves.

Animals↗
PubMed1994

Non-receptor tyrosine kinases in mammalian neurogenesis.

Several members of the Src family of non-receptor tyrosine kinases are expressed at high levels in embryonic neural tissues as well as in adult brain. Relatively little has been known, however, about their roles in neural development. Attempts to clarify this by production of mutant mice have been unsuccessful because of gene redundancy. We earlier isolated a new cytoplasmic protein tyrosine kinase, Csk, and showed that it inactivates uniquely all members of non-receptor tyrosine kinases in vitro. Here, we have generated Csk-deficient mouse embryos and shown that Csk is indeed an indispensable negative regulator for all non-receptor tyrosine kinases in vivo, and that regulated activity of these kinases is essential for normal development of mice at the neural stage. The signaling pathway through Src-family kinases during neurulation is also discussed.

Amino Acid Sequence↗