Biomedical subjects

T Imai

Publications and source records attributed to T Imai.

At least 19 recordsLinked to original sources

PubMed1992

Cellular mechanism of thrombin on endothelin-1 biosynthesis and release in bovine endothelial cell.

We have studied the cellular mechanism responsible for induction of preproendothelin (preproET)-1 mRNA and release of ET-1 by thrombin in cultured bovine endothelial cells (ECs). Thrombin induced an immediate and dose-dependent formation of inositol-1,4,5-trisphosphate (IP3) with a concomitant increase in intracellular Ca2+ concentration ([Ca2+]i). The thrombin-induced ET-1 release was abolished either by a phospholipase C inhibitor, a protein kinase C (PKC) inhibitor, or an intracellular Ca(2+)-chelator, whereas a Ca(2+)-channel antagonist was ineffective. A selective thrombin inhibitor (argatroban) decreased IP3 formation and the increase in [Ca2+]i and ET-1 release stimulated by thrombin. Northern blot analysis revealed that thrombin-induced expression of preproET-1 mRNA was inhibited completely by a PKC inhibitor and partially by argatroban. These data suggest that thrombin is involved in the mechanism of preproET-1 mRNA expression and subsequent ET-1 release, possibly through activation PKC and mobilization of intracellular Ca2+ resulting from the receptor-mediated phosphoinositide breakdown in ECs.

Animals↗

PubMed1992

C33 antigen recognized by monoclonal antibodies inhibitory to human T cell leukemia virus type 1-induced syncytium formation is a member of a new family of transmembrane proteins including CD9, CD37, CD53, and CD63.

C33 Ag was originally identified by mAb inhibitory to syncytium formation induced by human T cell leukemia virus type 1. The Ag was shown to be a highly heterogeneous glycoprotein consisting of a 28-kDa protein and N-linked oligosaccharides ranging from 10 to 50 kDa. In the present study, cDNA clones were isolated from a human T cell cDNA expression library in Escherichia coli by using mAb C33. The identity of cDNA was verified by immunostaining and immunoprecipitation of transfected NIH3T3 cells with mAb. The cDNA contained an open reading frame of a 267-amino acid sequence which was a type III integral membrane protein of 29.6 kDa with four putative transmembrane domains and three putative N-glycosylation sites. The C33 gene was found to belong to a newly defined family of genes for membrane proteins, such as CD9, CD37, CD53, CD63, and TAPA-1, and was identical to R2, a cDNA recently isolated because of its strong up-regulation after T cell activation. Availability of mAb for C33 Ag enabled us to define its distribution in human leukocytes. C33 Ag was expressed in CD4+ T cells, CD19+ B cells, CD14+ monocytes, and CD16+ granulocytes. Its expression was low in CD8+ T cells and mostly negative in CD16+ NK cells. PHA stimulation enhanced the expression of C33 Ag in CD4+ T cells by about 5-fold and in CD8+ T cells by about 20-fold. PHA stimulation also induced the dramatic size changes in the N-linked sugars previously shown to accompany human T cell leukemia virus type 1-induced transformation of CD4+ T cells.

Amino Acid Sequence↗

PubMed1992

Stem cell factor enhances proliferation, but not maturation, of murine megakaryocytic progenitors in serum-free culture.

The effects of recombinant rat stem cell factor (SCF/c-kit ligand) on murine megakaryocytopoiesis were studied using partially purified bone marrow cells derived from normal and 5-fluorouracil (5-FU)-treated mice in a serum-free culture system. SCF alone did not support the formation of megakaryocyte (M) and granulocyte-macrophage-megakaryocyte (GMM) colonies. However, the addition of SCF to cultures containing interleukin-3 (IL-3) resulted in a significant increase in the number of M and GMM colonies formed by bone marrow cells from normal mice, whereas IL-6 augmented only M colony growth. The stimulatory effect of SCF was approximately three to four times as high as that of IL-6 on the primitive progenitors capable of megakaryocytic-lineage expression derived from 5-FU-treated mice. In addition, SCF, but not IL-6, significantly increased the number of constituent cells in the individual M colonies supported by IL-3. On the other hand, SCF did not exert any effect on the size and DNA content of megakaryocytes in IL-3-dependent M and GMM colonies, whereas IL-6 enhanced the maturation of megakaryocytes. These results suggest that SCF stimulates the proliferative process in megakaryocytic progenitors and that the main activity of IL-6 is the promotion of megakaryocyte maturation.

Animals↗

PubMed1992

Strong induction of ICAM-1 in human T cells transformed by human T-cell-leukemia virus type 1 and depression of ICAM-1 or LFA-1 in adult T-cell-leukemia-derived cell lines.

Sixteen human T-cell lines were studied for the expression of a cell-adhesion molecule ICAM-1 and its counter-receptor LFA-1. The cell lines included 3 human T-cell-leukemia-virus-type-I (HTLV-1)-negative cell lines derived from acute lymphoblastic leukemia (ALL) and 13 HTLV-1-positive cell lines, 7 of them established from cord- or peripheral-blood T cells by in vitro transformation with HTLV-1, 2 derived from HTLV-1 carriers, and 4 derived from patients with adult T-cell leukemia (ATL). In sharp contrast to a basal level of ICAM-1 in 3 HTLV-1-negative ALL cell lines, strong induction of ICAM-1 was seen in all HTLV-1-positive T-cell lines except for MT-1, one of the 4 ATL cell lines used in the present study. On the other hand, the expression of LFA-1 (CD11a and CD18) was more or less similar among the cell lines with and without HTLV-1. Interestingly, however, 3 out of 4 ATL cell lines (TL-Om1, H582, HUT102) revealed striking depression of LFA-1 expression. Several lines of evidence strongly argued against direct involvement of the viral transactivator p40tax or some autocrine cytokines in the induction of ICAM-1 in HTLV-1-positive T-cell lines. It was also found that ICAM-1 and LFA-1 were involved in syncytium formation induced in the co-culture of HTLV-1-positive and HTLV-1-negative human T-cell lines. Implications of constitutive expression of ICAM-1 for certain clinical manifestations of ATL and of depression of either ICAM-1 or LFA-1 during progression of ATL are discussed.

Animals↗

PubMed1992

Endothelin receptors in human parathyroid gland.

We studied whether specific receptors for endothelins (ETs) exist in human parathyroid tissues and whether ETs may have any effect on secretion of PTH from parathyroid cells. Binding studies using [125I]ET-1 to the parathyroid membranes obtained from patients with hyperparathyroidism (2 adenomas, 2 hyperplasias) revealed that ET-1 competitively inhibited the binding of [125I]ET-1 to the membranes (the apparent Kd: 62 +/- 18 pM), whereas ET-3 showed biphasic and less steep inhibition curve than ET-1 in all tissue membranes examined. Northern blot analysis of poly(A)+ RNA from the parathyroid adenoma clearly demonstrated gene expression of both ETA and ETB receptors as well as preproET-1. ET-1 inhibited basal PTH secretion from dispersed adenoma cells more potently than ET-3. The present study clearly demonstrates the presence of both ETA and ETB receptor subtypes in human parathyroid tissues through which ETs may modulate PTH secretion in an autocrine and/or paracrine manner.

Adenoma↗

PubMed1992

Recent duplication of the two human CD8 beta-chain genes.

Isolation of cDNA clones encoding the beta-chain of the human T cell surface glycoprotein CD8 revealed the presence of five distinct forms of cDNA resulting from alternative splicing. In the process of analysis of the gene organization, we found that there exist two recently duplicated genes for CD8 beta. These genes, designated CD8 beta 1 and beta 2, consist of nine and seven exons, respectively. The organization of CD8 beta 1 and beta 2 genes is almost identical except in their 3'-ends. There are nine nucleotide differences between the coding regions of the CD8 beta 1 and beta 2 genes in spite of the extremely high similarity of these genes which extends over the entire genes including introns. Pulse field gel analysis demonstrated that CD8 beta 1 and beta 2 genes are located more than 1.5 Mb apart. It was found that the CD8 beta 1 gene is approximately 25 kb upstream from the CD8 alpha gene in the same transcriptional orientation on chromosome 2. Although both CD8 beta 1 and beta 2 genes appear functional from the nucleotide sequence, the five distinct forms of CD8 beta cDNAs and corresponding mRNAs found in thymus, PBL, and leukemic cell line HPB-ALL are all derived by alternative splicing from CD8 beta 1 transcripts.

Amino Acid Sequence↗

PubMed1992

Concomitant expression of receptor subtype and isopeptide of endothelin by human adrenal gland.

We studied whether specific receptors for endothelin (ET) isopeptide exist in human aldosterone-producing adenoma and normal adrenal cortex, and whether ET isopeptides are produced by human adrenal gland. Competitive binding studies using [125I]ET-1 as a radioligand revealed the presence of a single class of high-affinity binding sites for ET-1 with the apparent KD of 70 +/- 31 pM and Bmax of 226 +/- 139 fmol/mg protein in adenoma membranes almost comparable to those in adjacent normal cortex. The apparent Ki for ET-2 and ET-3 were 89 +/- 33 pM and 82 +/- 16 pM, respectively. Northern blot analysis of poly(A)+ RNA of adenoma and adjacent normal cortex using cDNAs for ET receptor subtype (ETA, ETB) and ET isopeptide (ET-1, ET-3) as probes revealed that ETA and ETB receptors as well as ET isopeptides (preproET-1, preproET-3) are concomitantly expressed in both tissues. Our data demonstrate for the first time that ET receptor subtype (ETA and ETB) and ET isopeptide (ET-1 and ET-3) are concomitantly expressed by human adrenal cortex, suggesting the potential role of ETs as a local mediator in human adrenal gland.

Adenoma↗

PubMed1992

Effects of three distinct natriuretic peptides on receptor binding and guanylate cyclase activities in rat glioma cells.

Receptor binding and cyclic GMP generation by three distinct natriuretic peptides (ANP, BNP, CNP) were studied in a cultured rat glioma cell line (C6). Binding studies revealed the presence of high-affinity binding sites for three natriuretic peptides with almost comparable affinities. In contrast, CNP and BNP were almost equipotent in stimulating intracellular cyclic GMP generation over the low concentration range, but CNP caused further elevation in the high concentration range, whereas ANP was minimally effective. Our data suggest that the glioma cells possess receptors more responsive to CNP than ANP and BNP despite no apparent correlation between receptor binding affinities and cyclic GMP responses.

Animals↗

PubMed1992

Pharmaceutical evaluation of ibuprofen fast-absorbed syrup containing low-molecular-weight gelatin.

Two kinds of ibuprofen syrups were prepared and evaluated. One was a suspending syrup, prepared by using hydroxypropyl methylcellulose (HPMC) as a dispersing agent, and the other was a dry syrup containing low-molecular-weight gelatin (LM gelatin). The dissolution behaviors of ibuprofen from syrups were studied, and both syrups showed size-dependent dissolution; the smaller particles exhibited faster dissolution. The in vivo absorption behaviors of the syrups were compared with that of commercial tablets of ibuprofen in beagle dogs and human volunteers. The absorption rates following oral administrations of syrups were much greater than those following administration of commercial tablets. Moreover, both syrups reduced the bitter taste and irritation of the oral mucosa caused by ibuprofen; the dry syrup markedly masked these side effects. These results suggest that the dry syrup containing LM gelatin improves some of the pharmaceutical properties of ibuprofen, and that the LM gelatin may be used in a variety of oral dosage forms.

Administration, Oral↗

PubMed1992

Canadian Mennonites and individuals residing in the Friesland region of The Netherlands share the same molecular basis of 17 alpha-hydroxylase deficiency.

A common mutation within the CYP17 gene that causes 17 alpha-hydroxylase deficiency, a form of congenital adrenal hyperplasia, has been found by direct sequencing of polymerase chain reaction (PCR) fragments of genomic DNA from six families residing in the Friesland region of the Netherlands. The mutation is a 4-base duplication within exon 8 of the CYP17 gene, which alters the reading frame encoding the C-terminal 26 amino acids of cytochrome P45017 alpha. This mutation has previously been found in two Canadian patients who are members of ostensibly unrelated Mennonite families. The Mennonite Churches derive their name from Menno Simons, an early leader of the sect in Friesland. Presumably this 4-base duplication appeared within the Friesian population prior to emigration of the Mennonites from the Netherlands.

Adrenal Hyperplasia, Congenital↗

PubMed1992

Brain lesions of the Leigh-type distribution associated with a mitochondriopathy of Pearson's syndrome: light and electron microscopic study.

Pearson's syndrome is a disease of refractory sideroblastic anemia and exocrine pancreatic dysfunction due to abnormal mitochondrial DNA (mtDNA). A male infant with Pearson's syndrome developed necrosis of both thalami and basal ganglia when he suffered from gastroenteritis at 1 year and 11 months of age. He died of sepsis at the age of 2 years and 4 months. Analysis of mtDNA from various organs revealed abnormal mtDNA with deletion by 5 kbp, confirming the diagnosis. At autopsy, the brain had symmetrical cavities in putamen, caudate nuclei and medial nuclei of the thalami. Ferruginous granules in nerve cells in medial thalamic nuclei, and scattered round bodies with neuronophagia in lateral nuclei were found at light microscopic observation. Electron microscopy showed that these granules were composed of radiating spicules and a dense layer containing packed cytoplasmic organelles, respectively. The macroscopic distribution of brain lesions was very similar to and characteristic of Leigh's disease. This similarity leads to the supposition that defective intracellular energy utilization common to Leigh's disease could be responsible for brain lesions in this case. Although the histological appearance was somewhat atypical for Leigh's disease, very acute formation of brain lesions in this case was thought to have caused the histological difference.

Anemia, Sideroblastic↗

PubMed1992

Intracisternal inclusions in Schwann cells of the sural nerve.

Biopsy of the sural nerve in a 74-year-old man with chronic neuropathy demonstrated Schwann cells that possessed multiple cisterns of rough endoplasmic reticulum filled with 7- to 8-nm filaments and perinuclear cisterns that were markedly distended with fine granular substances and electron-dense globules. To our knowledge, this is the third case exhibiting filamentous inclusions in Schwann cells. Unlike the previous cases, however, this case showed inclusions in the distended perinuclear cisterns and axonal degeneration. The significance of these alterations remains to be elucidated.

Aged↗

PubMed1992

Myelination of two axons by a single Schwann cell.

A Schwann cell can form only one internode of myelin around an axon. However, we observed the formation by a single Schwann cell of myelin around two axons of different diameters in the sural nerve of a 45-year-old man with mononeuritis multiplex. Schwann cell processes spiraled in the same direction around each axon, forming mesaxons. The findings in this case appear to be an undescribed type of aberrant myelination.

Axons↗

PubMed1992

Significance of multidisciplinary therapy for hepatocellular carcinoma.

The effect of multidisciplinary therapy for hepatocellular carcinoma (HCC) was evaluated in 121 resected cases. The 5-year survival was 100% for absolute curative resection (12 cases), 59.1% for relative curative resection (n = 37) and 10.9% for relative non-curative resection (n = 59). However, none of the patients survived for more than 3 years after absolute non-curative resection (n = 13). The non-recurrence in the preoperative TAE groups was different from that in non-TAE groups undergoing absolute and relative curative resection. The 1- and 3-year non-recurrence rates for relative non-curative resection were 92.3% and 53.8%, respectively, for the preoperative TAE group and 56.1% and 28.1%, respectively for the non-TAE group. These data show that preoperative TAE is effective in relative non-curative resection. Functional disturbances of the coagulation-fibrinolysis system in cirrhotic patients were improved after PSE. All patients undergoing hepatectomy after PSE had an uneventful postoperative course, including well-maintained function of the coagulation-fibrinolysis system and a decrease in splenic volume. At 1 year after hepatectomy, cirrhotic patients with critical liver function and poor coagulation-fibrinolysis showed appreciable hepatic regeneration. One patient died of hepatic failure 1 year after the operation. In recurrent HCC, the 1-, 2- and 3-year survival values after reresection were 100%, 75.0% and 25.0%, respectively. The respective values following TAE were 79.0%, 42.0% and 9.0%. Three cases of recurrent HCC were effectively treated, i.e., two patients achieved a partial response and one showed no change, by continuous intra-arterial infusion of 5-FU and lentinan with intermittent one-shot injections of epirubicin using a subcutaneous infusion pump. These three patients are alive at 1 year and 7 months, 1 year and 4 months and 6 months after the treatment, respectively.

Adult↗

PubMed1992

Ataxic variant of adrenoleukodystrophy: MRI and CT findings.

A 28-year-old man developed slowly progressive dysarthria and gait disturbance over 7 years. Neurological examination revealed marked ataxia of articulation and gait, mild ataxia and spasticity of all four limbs without intellectual, visual, auditory, sensory or sphincter dysfunction. No physical signs of adrenal hypofunction were found. However, analysis of fatty acid of plasma sphingomyelin showed an increase in very long chain fatty acids, compatible with the diagnosis of adrenoleukodystrophy. Computed tomography disclosed marked atrophy of the cerebellum and pons, and bilateral low-density lesions in the deep while matter of the cerebellum. Magnetic resonance imaging showed these lesions more clearly, as well as other lesions in the middle and superior cerebellar peduncles, despite the absence of cerebral white matter involvement at the time of presentation. This is a rare case of adrenoleukodystrophy presenting as spinocerebellar degeneration and showing marked atrophy and several parenchymatous lesions of the cerebellum and brain stem.

Adrenoleukodystrophy↗

PubMed1992

Induction of strong homotypic adhesion in human T cell lines positive with human T-cell leukemia virus type 1 by monoclonal antibodies to MHC class I and beta 2-microglobulin.

To identify the cellular receptors and other cell surface molecules playing essential roles in the transmission of human T-cell leukemia virus type 1 (HTLV-1), we have been isolating monoclonal antibodies (mAbs) that are capable of inhibiting HTLV-1-induced syncytium formation. In the present study, we isolated two mAbs, H11 (IgM) and H14 (IgG1), inhibitory to syncytium formation in the coculture of TOM-1 or C91/PL (both HTLV-1-positive human T-cell lines) and MOLT-4/8 (HTLV-1-negative human T-cell line) by immunizing the membrane fraction of human osteosarcoma line HOS. By immunoprecipitation and immunoblotting, H11 and H14 were found to be specific for MHC class I heavy chain and beta 2-microglobulin (beta 2 M), respectively. Among the four commercially obtained mAbs, two mAbs for MHC class I antigen and two mAbs to beta 2 M, one mAb to MHC class I antigen and one mAb to beta 2 M were also found to be inhibitory to the syncytium formation. The functional comparison of these mAbs revealed that the syncytium-inhibitory mAbs induced strong homotypic cell adhesion particularly in the HTLV-1-positive T-cell lines. This cell adhesion was dependent on temperature, energy metabolism, and microfilament function but not on the activity of protein kinase C or divalent cations. These results suggest a novel type of LFA-1-independent cell adhesion induced by signal transduction via MHC class I antigen.

Antibodies, Monoclonal↗

PubMed1992

Physical mapping of a 950-kb region surrounding a locus (D10S102) tightly linked to the MEN2A gene.

We have constructed a long-range contig of cosmid and YAC clones around D10S102, a locus that is tightly linked to the gene responsible for multiple endocrine neoplasia type 2A (MEN2A). With D10S102 as a starting point, a 360-kb cosmid contig was constructed by bidirectional genomic walking, and at least six fragments from these cosmids showed high sequence homology to other species. Five YAC clones were also isolated at the D10S102 locus, and they formed a contig covering 950 kb of genomic DNA. Furthermore, we obtained six RFLP systems from the contig, which will serve as new resources for fine-scale genetic linkage mapping of the MEN2A locus.

Base Sequence↗

PubMed1992

Structure of the bovine endothelin-B receptor gene and its tissue-specific expression revealed by northern analysis.

We have isolated and characterized the gene encoding the bovine endothelin (ET) receptor ETB with seven putative membrane-spanning domains. The gene exists as a single copy of the bovine genome and extends over 36 kilobases. The coding region is divided into seven exons separated by six introns; the first exon encodes the first and second transmembrane domains and each of the following transmembrane domains is encoded by a separate exon. The 5' region of the transcript was examined by the ribonuclease protection analysis; multiple start sites were deduced with no apparent "TATA" box in the expected upstream region. Northern blot analysis demonstrated a widespread but tissue-specific distribution of the ETB receptor in bovine tissues.

Amino Acid Sequence↗