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Biomedical subjects

M Kitagawa

Publications and source records attributed to M Kitagawa.

At least 199 records · Page 11Linked to original sources
PubMed1998

Agreement between predicted risk and prevalence of Down syndrome in second-trimester triple-marker screening in Japan.

Based on 9350 pregnant Japanese women who were screened by serum triple-marker determination, accuracy of predicted risk for Down syndrome was examined using 24 Down syndrome cases detected either prenatally or postnatally. The correlation is statistically very high (r = 0.98) between the predicted risks and the prevalence of Down syndrome cases. Here we emphasize that this could be accomplished only by an extensive follow-up study, implemented in our prospective intervention programme.

Amniocentesis↗
PubMed1998

Clinicopathologic features of neuroendocrine carcinomas of the stomach: appraisal of small cell and large cell variants.

OBJECTIVE: To clarify the clinicopathologic features of neuroendocrine carcinomas (NECs) of the stomach, we reviewed 56 cases of surgically treated gastric carcinomas with a solid growth or with areas containing patterns characteristic for neuroendocrine (NE) tumors. METHODS: Of the 56 cases reviewed, we selected 33 cases of NEC based both on histologic patterns common to NE tumors and on histochemical/immunohistochemical results. RESULTS: The average age of patients with NEC was 69.8 years (range, 44-92 years). The majority of patients were men (male-female ratio, 23:10). The most frequently affected site was the upper third (46%) of the stomach. Grossly, 9 cases of NEC were fungating and 24 were ulcerated. As compared with 23 patients with non-NEC tumors, the patients with NECs had a worse prognosis. Histologically, NECs had a variety of histologic patterns, including solid, organoid, trabecular, pseudoglandular, spindle cell, and rosettelike. Based on both cell size and morphologic features, we subdivided NECs into 2 variants, namely, small cell NEC and large cell NEC. Our series included 12 cases of small cell NEC and 21 cases of large cell NEC. CONCLUSIONS: Compared with small cell NECs, large cell NECs had a higher mitotic count, larger polygonal cells, a lower nuclear-cytoplasmic ratio, coarser nuclear chromatin, and more frequent conspicuous nucleoli. Large cell NEC was an aggressive tumor with a very poor prognosis (median survival time, 15.2 months; 1-year survival rate, 58%), which approached that for small cell NEC.

Adult↗
PubMed1998

Coexistence of proguanylin (1-15) and somatostatin in the gastrointestinal tract.

In order to identify proguanylin-secreting cells, we have raised an antiserum against the synthetic fragment of human proguanylin (1-15) and have examined the proguanylin-positive cells in the human and rat gastrointestinal tract by immunohistochemical methods. Numerous proguanylin (1-15)-immunoreactive cells were found in the gastrointestinal tract. They were either pyramidal or spindle shaped in the stomach. Spindle-shaped cells, frequently possessing long slender processes, were located at the base of the pyloric epithelium and did not extend to the lumen. In the duodenum and jejunum, these cells were mostly pyramidal in shape and often had a slender process towards the lumen. The immunostaining was completely blocked by the human proguanylin (1-15) fragment. Paneth and goblet cells were negative against this antiserum. The number of serotonin-positive cells was much larger than that of proguanylin-positive cells in all the segments tested. The number of proguanylin-positive cells decreased from the jejunum to the ileum and very few cells were observed in the colon. In contrast to serotonin-positive cells, most somatostatin-positive cells were also positive for proguanylin. Thus, proguanylin (1-15) or its related protein appears to coexist with somatostatin in intestinal endocrine D cells which may be a source of circulating proguanylin. Proguanylin, like somatostatin, may also regulate intestinal function as a local regulator.

Animals↗
PubMed1997

Geranylgeranylpyrophosphate, a metabolite of mevalonate, regulates the cell cycle progression and DNA synthesis in human lymphocytes.

We investigated the role of the intrinsic mevalonate cascade in DNA synthesis and cell cycle progression in human peripheral blood mononuclear cells (PBMC) stimulated by phytohemagglutinin (PHA). PHA stimulated the expression of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase mRNA prior to the DNA synthesis (S phase). Pravastatin, an HMG-CoA reductase inhibitor, inhibited DNA synthesis and blocked the entry to S phase in PHA-stimulated PBMC. Mevalonate restored these inhibitory effects. Thus, we examined two major metabolites of mevalonate, geranylgeranyl-pyrophosphate (GGPP) and farnesyl-pyrophosphate (FPP), using a novel liposome system for uptake into the cells. GGPP, not FPP, restored the pravastatin-induced inhibitions. These data indicated that 1) the intrinsic mevalonate cascade plays critical roles for the entry to S phase and DNA synthesis, and that 2) GGPP is an essential metabolite of mevalonate cascade for cell cycle progression in PBMC stimulated by PHA.

Acyl Coenzyme A↗
PubMed1997

Molecular cloning and characterization of a novel mitochondrial phosphoprotein, MIPP65, from rat liver.

A novel 65-kDa protein (designated MIPP65), which was phosphorylated by PKN in vitro in a manner highly dependent on arachidonic acid, was partially purified from the heat-stable proteins extracted from a 30,000g precipitate of rat liver. The cDNA clones were obtained by polymerase chain reaction using oligonucleotides based on partial amino acid sequences. The complete amino acid sequence deduced from the cDNAs contained two homologous regions with the mitochondrial NADH-ubiquinone oxidoreductase 9-kDa subunit precursor at the amino- and carboxyl-termini, whereas the central region was not related to any known proteins and contained a serine cluster. Northern blotting and immunoblotting analyses indicated that MIPP65 was expressed ubiquitously in rat tissues. Immunofluorescence analysis of the endogenous MIPP65 using polyclonal antiserum against MIPP65 showed a predominantly mitochondrial localization in C6 glioma cells. The recombinant MIPP65 expressed in COS7 cells showed a similar pattern of localization to that in C6 glioma cells. On the other hand, deletion of the amino-terminal region of MIPP65 abrogated such localization, indicating that the amino-terminal region contained a mitochondrial-targeting signal. From [32P]orthophosphate-labeled C6 glioma cells, the endogenous MIPP65 could be immunoprecipitated as a phosphoprotein with antiserum against MIPP65. These results suggest that MIPP65 is a novel mitochondrial phosphoprotein that is a candidate substrate for PKN.

Amino Acid Sequence↗
PubMed1997

Polyploidization and functional maturation are two distinct processes during megakaryocytic differentiation: involvement of cyclin-dependent kinase inhibitor p21 in polyploidization.

The mechanism of megakaryocytic differentiation was investigated using human megakaryocytic leukemia cell line UT-7. Polyploidization of UT-7 cells was induced by the microtubule-depolymerizing agent, nocodazole, and 12-O-tetradecanoylphorbol-13-acetate (TPA), but the effect was much more striking with nocodazole. By contrast, induction of cytoplasmic maturation, as judged by beta-thromboglobulin production and platelet factor 4 expression, was more prominent in TPA-treated cells than in nocodazole-treated cells. Nocodazole and TPA could act synergistically to increase ploidy and to enhance the expression of mature phenotypes. Human thrombopoietin induced functional maturation but not polyploidization in UT-7 cells and also acts synergistically with nocodazole. Cyclin-dependent kinase inhibitor p21 was upregulated at the early stage of megakaryocytic differentiation, and overexpression of p21 resulted in an increase in ploidy of UT-7 cells. This suggests that p21 is implicated in polyploidization via suppression of CDC2 activity at mitosis. UT-7 but not HL-60 cells could incorporate [3H]thymidine in the presence of TPA, indicating the presence of megakaryocyte-specific licensing factor to allow DNA replication during differentiation. Taking these data together, we propose that megakaryocytic differentiation consists of two distinct processes, polyploidization and functional maturation, and that these two processes are independently regulated.

Carcinogens↗
PubMed1997

Effects of exogenous p16INK4a on growth of cells with various status of cell-cycle regulators.

p16INK4a, a protein that inhibits cyclin-dependent kinase 4 (Cdk4) and Cdk6, is deficient in many human cancers and in established lines of tumor cells. It has been reported that transfection with cDNA for p16INK4a inhibits the growth of cell lines that express retinoblastoma protein (pRB). However, it is unclear whether the introduction of cDNA for p16INK4a affects the growth of cells that express p16INK4a protein. Moreover, the effects of other cell-cycle regulators on the inhibition of cell growth by p16INK4a remain unknown. In this study, cDNA for p16INK4a was used to transfect human cell lines that had various status of expression of RB pathway-related proteins, such as members of the RB family proteins and Cdk-inhibitory proteins. We found that status of p107, p130, p15INK4b, p18INK4c, p21Cip1, p27Kip1, cyclin D1, and Cdk4 were not correlated with the growth-inhibitory activity of exogenous p16INK4a. By contrast, transfection with cDNA for p16INK4a had a significant effect on the growth of cells depended on the status not only of pRB but also of p16INK4a. Although exogenous p16INK4a inhibited the growth of cells that expressed pRB but did not express p16INK4a (pRB+/p16- cells), it had little affect on either pRB+/p16+ cells or pRB-/p16+ cells. Moreover, transfection with cDNA for p16INK4a also inhibited the activity of the E2 promoter of the dehydrofolate reductase gene in the same manner that depended on the absence of p16INK4a, as well as on the presence of pRB. These results suggest that deregulation of the RB pathway by p16INK4a deficiency plays a very important role in the proliferation of cells that lack p16INK4a protein.

Base Sequence↗
PubMed1997

Construction of a contiguous 874-kb sequence of the Escherichia coli -K12 genome corresponding to 50.0-68.8 min on the linkage map and analysis of its sequence features.

The contiguous 874.423 base pair sequence corresponding to the 50.0-68.8 min region on the genetic map of the Escherichia coli K-12 (W3110) was constructed by the determination of DNA sequences in the 50.0-57.9 min region (360 kb) and two large (100 kb in all) and five short gaps in the 57.9-68.8 min region whose sequences had been registered in the DNA databases. We analyzed its sequence features and found that this region contained at least 894 potential open reading frames (ORFs), of which 346 (38.7%) were previously reported, 158 (17.7%) were homologous to other known genes, 232 (26.0%) were identical or similar to hypothetical genes registered in databases, and the remaining 158 (17.7%) showed no significant similarity to any other genes. A homology search of the ORFs also identified several new gene clusters. Those include two clusters of fimbrial genes, a gene cluster of three genes encoding homologues of the human long chain fatty acid degradation enzyme complex in the mitochondrial membrane, a cluster of at least nine genes involved in the utilization of ethanolamine, a cluster of the secondary set of 11 hyc genes participating in the formate hydrogenlyase reaction and a cluster of five genes coding for the homologues of degradation enzymes for aromatic hydrocarbons in Pseudomonas putida. We also noted a variety of novel genes, including two ORFs, which were homologous to the putative genes encoding xanthine dehydrogenase in the fly and a protein responsible for axonal guidance and outgrowth of the rat, mouse and nematode. An isoleucine tRNA gene, designated ileY, was also newly identified at 60.0 min.

Base Sequence↗
PubMed1997

Cell cycle control with minimal participation of Cdk2 in a murine fibrosarcoma clone cultured in protein-free medium.

The differences in the protein expression of cyclins, cyclin-dependent kinases (cdks), and their inhibitors and cdk kinase activities were examined in serum dependent (SD) and independent (PF) clones of the murine fibrosarcoma cell line, Gc-4. The expression of cyclin A in SD was minimal in contrast to PF. Furthermore, cdk2 kinase activity in PF was remarkably lower than that in SD, yet the G1/S transition in PF appeared normal. PF was also resistant against the selective inhibitor of cdk2, butyrolactone I. These findings suggest that tumor cell proliferation and tumor progression can be promoted by the activation of a molecule(s) downstream of cdk2.

4-Butyrolactone↗
PubMed1997

Activation of Stat1 by mutant fibroblast growth-factor receptor in thanatophoric dysplasia type II dwarfism.

The achondroplasia class of chondrodysplasias comprises the most common genetic forms of dwarfism in humans and includes achondroplasia, hypochondroplasia and thanatophoric dysplasia types I and II (TDI and TDII), which are caused by different mutations in a fibroblast growth-factor receptor FGFR3 (ref. 1). The molecular mechanism and the mediators of these FGFR3-related growth abnormalities are not known. Here we show that mutant TDII FGFR3 has a constitutive tyrosine kinase activity which can specifically activate the transcription factor Stat1 (for signal transducer and activator of transcription). Furthermore, expression of TDII FGFR3 induced nuclear translocation of Stat1, expression of the cell-cycle inhibitor p21(WAF1/CIP1), and growth arrest of the cell. Thus, TDII FGFR3 may use Stat1 as a mediator of growth retardation in bone development. Consistent with this, Stat1 activation and increased p21(WAF1/CIP1) expression was found in the cartilage cells from the TDII fetus, but not in those from the normal fetus. Thus, abnormal STAT activation and p21(WAF1/CIP1) expression by the TDII mutant receptor may be responsible for this FGFR3-related bone disease.

Animals↗
PubMed1997

Expression of p16INK4a suppresses the unbounded and anchorage-independent growth of a glioblastoma cell line that lacks p16INK4a.

p16INK4a is a inhibitory protein of Cyclin-dependent kinase 4(Cdk4).p16 negatively regulates the cell cycle progression from G1 to S phase. Functional p16 is absent from many human cancers, as well as from many established lines of tumor cells. However, it is not clear whether expression of p16 in p16-deficient tumor cells can suppress their anchorage-independent growth. Therefore, we introduced a cDNA for p16INK4a into the human glioblastoma cell line T98G, which lacks a gene for p16INK4a. We isolated several clones that stably expressed various amounts of p16 protein. The doubling time of the various clones was generally prolonged. Clones with high-level expression of p16 protein had characteristics of restricted growth, such as contact inhibition, while the parental T98G cells had no such characteristics. Furthermore, the efficiency of colony formation in soft agar was dramatically decreased in the case of cells that expressed exogenous p16. Our observations suggest that the expression of p16 protein restricts the unbounded growth and the anchorage-independent growth of tumor cells.

Carrier Proteins↗
PubMed1997

Interaction of PKN with alpha-actinin.

PKN is a fatty acid- and Rho-activated serine/threonine protein kinase, having a catalytic domain homologous to protein kinase C family. To identify components of the PKN-signaling pathway such as substrates and regulatory proteins of PKN, the yeast two-hybrid strategy was employed. Using the N-terminal region of PKN as a bait, cDNAs encoding actin cross-linking protein alpha-actinin, which lacked the N-terminal actin-binding domain, were isolated from human brain cDNA library. The responsible region for interaction between PKN and alpha-actinin was determined by in vitro binding analysis using the various truncated mutants of these proteins. The N-terminal region of PKN outside the RhoA-binding domain was sufficiently shown to associate with alpha-actinin. PKN bound to the third spectrin-like repeats of both skeletal and non-skeletal muscle type alpha-actinin. PKN also bound to the region containing EF-hand-like motifs of non-skeletal muscle type alpha-actinin in a Ca2+-sensitive manner and bound to that of skeletal muscle type alpha-actinin in a Ca2+-insensitive manner. alpha-Actinin was co-immunoprecipitated with PKN from the lysate of COS7 cells transfected with both expression constructs for PKN and alpha-actinin lacking the actin-binding domain. In vitro translated full-length alpha-actinin containing the actin-binding site hardly bound to PKN, but the addition of phosphatidylinositol 4, 5-bisphosphate, which is implicated in actin reorganization, stimulated the binding activity of the full-length alpha-actinin with PKN. We therefore propose that PKN is linked to the cytoskeletal network via a direct association between PKN and alpha-actinin.

Actinin↗