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Biomedical subjects

K Egawa

Publications and source records attributed to K Egawa.

At least 73 records · Page 4Linked to original sources
PubMed1995

Isolation of a novel ras-recision gene that is induced by hydrogen peroxide from a mouse osteoblastic cell line, MC3T3-E1.

Hydrogen peroxide appears to mediate growth factor actions, and it inhibits DNA synthesis in normal mouse osteoblastic cells (MC3T3-E1) at non-toxic doses. However the sensitivity of cells to H2O2 is greatly decreased in their ras-transformants. To understand the molecular basis of this sensitivity to H2O2, we attempted to identify H2O2-inducible cDNA clones from MC3T3 cells by differential screening of cDNA libraries, and one of such genes, named HIC-53, was isolated. The level of HIC-53 mRNA was moderately increased by H2O2 as well as by calcium ionophore or dexamethasone, but was not increased by the addition of serum, tumor promoting phorbol ester, or epidermal growth factor. Among mouse organs, HIC-53 mRNA levels were higher in the kidney and lung, but were almost undetectable in the brain, heart, bone, muscle or spleen. In MC3T3 cells transformed with v-Ki-ras, the HIC-53 mRNA level was markedly decreased, and effect of H2O2 was abolished. Although the biological function of HIC-53 is unknown at present, the predicted amino acid sequence exhibited some similarity with bovine cardiac Na+/Ca+ exchanger. The nucleotide sequence of HIC-53 cDNA showed no significant similarity with other known gene sequences.

Amino Acid Sequence↗
PubMed1995

The effect of fatigue caused by electrical induction or voluntary contraction on Ia inhibition in human soleus muscle.

A comparison of the effect of fatigue caused by electrical induction or voluntary contraction on Ia inhibition in human soleus muscle was investigated in fourteen healthy male subjects. The Hoffmann reflex (H reflex) was employed to elucidate the contribution of fatigue induced contraction to the Ia inhibition. A statistically significant difference (P < 0.05) in H reflex amplitude between the intermittent stimulation at 15 Hz and voluntary contraction was observed. Our study suggested that Ia inhibition in human soleus muscle, caused by electrically induced or voluntary contraction, induced differences in the number of impulses in the group Ia fibers, between the two conditions.

Adult↗
PubMed1995

Thiazolidine derivatives ameliorate high glucose-induced insulin resistance via the normalization of protein-tyrosine phosphatase activities.

The mechanisms for the insulin resistance induced by hyperglycemia were investigated by studying the effect of high glucose concentration (HG) and its modulation by thiazolidine derivatives, on insulin signaling using Rat 1 fibroblasts expressing human insulin receptors (HIRc). Incubating HIRc cells in 27 mM D-glucose for 4 days impaired the insulin-stimulated phosphorylation of pp185 and receptor beta-subunits. Both protein kinase C activities and phorbol dibutyrate binding to intact cells were unchanged; however, cytosolic protein-tyrosine phosphatase (PTPase) activity increased within 1 h prior to the impairment of insulin receptor kinase in HG cells (Maegawa, H., Tachikawa-Ide, R., Ugi, S., Iwanishi, M., Egawa, K., Kikkawa, R., Shigeta, Y., and Kashiwagi, A. (1993) Biochem. Biophys. Res. Commun. 197, 1078-1082). Increased PTPase activity was consistent with a 2-fold increase in the amount of PTP1B, and anti-PTP1B antibody inhibited this increment of cytosolic PTPase activity in HG cells. Co-incubating cells with pioglitazone prevented these abnormalities in cytosolic PTPase, the PTP1B content and the impaired phosphorylation of pp185 and receptor beta subunits in HG cells. Finally, HG cells had impaired insulin-stimulated alpha-amino-isobutyric acid uptake, which was ameliorated by exposure to thiazolidine derivatives. In conclusion, exposing cells to high glucose levels desensitizes insulin receptor function, and thiazolidine derivatives can reverse the process via the normalization of cytosolic PTPase, but not of protein kinase C.

Aminoisobutyric Acids↗
PubMed1995

Suppression of cytotoxic T lymphocyte activity by gamma/delta T cells in tumor-bearing mice.

Spleen cells derived from tumor-bearing mice prove useful for the elucidation of the mechanism determining how tumor cells evade cytotoxic T lymphocytes (CTL) in tumor-bearing hosts. Our data indicate that inactive CTL or precursor CTL specific for tumor antigens are present among lymphocytes of tumor-bearing mice. However, their activity is inhibited by a soluble factor produced by other cells present in the same source. Inhibition of the cytolytic reaction was also detected in the culture supernatant of spleen cells obtained from normal mice, precultured in the presence of tumor cell culture supernatant and interleukin-2 (IL-2). Cell-depletion and cell-purification studies let us conclude that cells that produced the CTL-inhibitory factor (CTL-IF) were gamma/delta T cells. The gamma/delta T cells that were activated in vivo in tumor bearers were able to produce CTL-IF after isolation and in vitro culture. Maximum activation of gamma/delta T cells was achieved by antigenic stimulation and by suppression of cells that interfered with the activation of gamma/delta T cells. CTL-IF, which was assayed by use of CTL clones, did not show antigen specificity. Inhibition depended on a relatively heat- and acid-stable, but alkali-labile molecule with a molecular mass of less than 10 kDa. The latter characteristics imply that CTL-IF does not resemble any of the known lymphokines produced by gamma/delta T cells. These observations emphasize the crucial role of the gamma/delta T cells in the escape of tumor cells from the attack of tumor-specific CTL.

Animals↗
PubMed1995

Protection against metastasis by immunization with an allogeneic lymphocyte antigen.

Q5 antigens are expressed on the surface of various experimental murine tumor cells. They share partially common antigenicity with Qa-2 alloantigens expressed on normal lymphocytes. For that reason we tested the immunoprotection by anti-Qa-2 immunization of mice against a Q5+ tumor. Nerve fibrosarcoma (NSFA) tumor, which specifically develops metastasis in the lung, has been reported to be poorly immunogenic. However, expression of the Q5 antigen was evident on the surface of NFSA cells. After immunizing (C3H/He x B6.K1)F1 (Qa-2-) mice with B6 (Qa-2+) lymphocytes, the protection against the proliferation of the semi-syngeneic NFSA tumor was examined. First, immunization of normal mice induced resistance to NFSA cell transplants. Second, when the tumor cells were transplanted to the hind foot of a mouse and the resulting tumor was removed by amputating the leg, the mice were protected against the development of lung metastasis after immunization by intraperitoneal inoculation of B6 cells 3 days after tumor removal. Immunization with attenuated NFSA cells in this system failed to protect the mice from lung metastasis. On the other hand, inoculation of the mice with B6 cells without removal of the original tumor on the foot showed little effect on the progression of the tumor. Thus, cytotoxic T lymphocytes (CTL), which seemed to be present in an inactive form in the mice from which the tumor had not been removed, were induced in the mice after the removal of the major tumor followed by immunization with B6 lymphocytes. The induction of CTL by the immunization was suppressed in mice bearing large tumors. Cells stimulated by the tumor antigen seemed to be involved in the suppression. It was also shown that the Q5 antigen is the direct recognition target of the CTL since the activity of Q5-specific CTL clones in lysing tumor cells was inhibited by a monoclonal antibody specific for the Q5 antigen. In contrast to immunization with attenuated tumor cells, our novel allogeneic lymphocyte immunization procedure offers high CTL activation, by-passing the induction of T cell unresponsiveness.

Amputation, Surgical↗
PubMed1995

Amplification and analysis of promoter region of insulin receptor gene in a patient with leprechaunism associated with severe insulin resistance.

A patient with leprechaunism associated with severe insulin resistance was studied to identify the molecular and genetic basis for insulin resistance. Insulin binding and surface labeling of transformed lymphocytes prepared from the patient showed a significantly decreased insulin receptor number on the cell surface. Southern blot analysis of the insulin receptor gene showed no evidence of large insertions or deletions. Furthermore, direct sequencing of all 22 exons and exon-intron junctions of the insulin receptor gene failed to show any missense mutations, nonsense mutations, or mutations at exon-intron junctions. However, Northern blot analysis indicated significantly decreased insulin receptor mRNA expression in the patient's cells. Moreover, restriction endonuclease digestion of the amplified cDNA suggested that the expression levels of one allele were less efficient than the other. These findings suggested that the regulatory region of the insulin receptor gene might have abnormalities. Therefore, we examined the 5' flanking region of the insulin receptor gene. Southern blot analysis showed no major deletions or insertions between positions -1,823 and -2 relative to the translation initiation site. A 5' flanking region of the insulin receptor gene spanning positions -881 approximately +7 was amplified by polymerase chain reaction (PCR) and introduced into a reporter plasmid carrying the human growth hormone (hGH) gene. The nucleotide sequence of the amplified fragment showed two polymorphic sites at positions -603 and -500 in the patient, as well as in normal subjects. No other abnormal sequence was found in the patient. Promoter activity measured by hGH expression in transfected mouse L cells was not influenced by the polymorphism at position -603 located in a cluster of GC boxes.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗
PubMed1995

Isolation of a human allo-peptide presented by HLA-B51 molecules.

Recent studies have demonstrated directly that alloreactive mouse CTL recognize peptides presented by MHC class I molecules. However, there is no direct evidence that human alloreactive CTL recognize peptides presented by HLA class I molecules. We have isolated an HLA-B51 alloreactive CTL clone, 2B3, that did not kill the TAP defective cell lines T2 and .174, whereas it killed the TAP-positive cell line T1 and .174 cells transfected with TAP genes. These findings suggested that this clone recognizes a TAP-dependent allo-peptide. We attempted to isolate the human allo-peptide recognized by the 2B3 clone from HLA-B51 molecules. A naturally occurring HLA-B*5101 binding peptide isolated from T1 cells was recognized by the 2B3 clone. The peptide was also isolated from HLA-B*5101 molecules purified from C1R-B*5101 cells. In the present study, we directly demonstrated that a human alloreactive CTL clone recognizes peptide presented by HLA class I molecules.

Antigen Presentation↗
PubMed1995

Epidermoid cyst with sweat ducts on the torso.

We report a case of an epidermoid cyst arising on the upper chest that had a remarkable histologic pattern composed of structures resembling eccrine ducts in the horny layer and an acrosyringium. The expression of carcinoembryonic antigen (CEA) was also demonstrated immunohistochemically within these ductal structures. Eccrine ducts have been reported recently, in epidermoid cysts located in the palmoplantar region. The cyst described here suggests that epidermoid cysts derived from eccrine ducts may also appear on the torso.

Carcinoembryonic Antigen↗
PubMed1995

Multiple giant molluscum contagiosa with cyst formation.

We report a case of multiple cystic tumors distributed on the scalp, face, neck, and upper trunk of a 68-year-old male. In all five cysts examined, the presence of molluscum contagiosum virus (MCV) was demonstrated electron microscopically, and the typical histological features of MCV infection were observed in the cyst wall. In one lesion, histological features suggesting a follicular origin of the cyst were seen.

Aged↗
PubMed1995

Detection of human papillomaviruses and eccrine ducts in palmoplantar epidermoid cysts.

Although epidermoid cysts of the palms and soles have long been assumed to develop following implantation of an epidermal fragment as a result of a penetrating injury, the pathogenic mechanism is still controversial, and the discovery of a more common aetiological agent is awaited. Clinical, histological, immunohistochemical and molecular biological studies were performed on 119 epidermoid cysts of palmoplantar location, in order to examine the role of the eccrine ducts, and human papillomavirus (HPV), in the pathogenesis of this disorder. Characteristic histological features were found, including intracytoplasmic eosinophilic bodies (ICB: in 14 cases, 12%) in the cyst wall, vacuolar structures (V: in 28 cases, 24%), or parakeratotic nuclei (P: in 85 cases, 71%) within the keratinous mass in the cyst cavity. Ductal structures suggesting eccrine ducts (E: in 63 cases, 53%) were also found in the cyst wall or in the cyst cavity. Either ductal structures or carcinoembryonic antigen expression (66 cases, 55%) were noted in a total of 73 cases (61%). Papillomavirus common antigens were detected in 36 cases (30%) showing one or more of the three distinct histological features, i.e. ICB, V and P. Subsequently, hybridization experiments to detect HPV DNA were performed in 47 cases, revealing an association between cysts showing ICB or V and the presence of HPV 60 DNA sequences. On the basis of our results, we propose that epidermoid cysts in the palmoplantar regions may develop from eccrine ducts, and that HPV and injury may play a role in their pathogenesis.

Adolescent↗
PubMed1994

Effect of radical scavengers on TNF alpha-mediated activation of the uPA in cultured cells.

Active oxygen, produced by cultured cells following stimulation with various growth factors, seems to be involved in signal transduction leading to cellular responses such as gene expression and growth modulation. In the present study, the intracellular oxidation state was measured in immortalized human endothelial cells (ECV304) after treatment with tumor necrosis factor (TNF) alpha, using a fluorescent dye and a laser-scanning confocal microscope. The intracellular oxidation state was increased 60 min after the addition of TNF alpha, and this increase was abolished by a radical scavenger, N-acetylcysteine (NAC), which is also a precursor of glutathione, and by pyrrolidine dithiocarbamate (PDTC). TNF alpha increased the steady state level of urokinase-type plasminogen activator (uPA), and NAC inhibited this increase at a dose that also inhibited the increase in the intracellular oxidation state. PDTC, on the other hand, did not affect the induction of the uPA gene by TNF alpha. These results suggest that intracellular glutathione level rather than the oxidation state is necessary for the induction of the uPA gene by TNF alpha.

Acetylcysteine↗
PubMed1994

Leu 193 mutation in the cysteine rich region of the insulin receptor inhibits the cleavage of the insulin receptor precursor but not insulin binding.

To characterize the Leu 193 mutant insulin receptor, which was found in a patient with extreme insulin resistance, the mutant insulin receptor was overexpressed in Rat-1 fibroblasts by transfection of mutated insulin receptor cDNA. In the pulse-chase experiment, the cleavage of the proreceptors to the matured receptor subunits was impaired in the cells expressing Leu 193 insulin receptor and therefore, the mutant proreceptors were accumulated in the cell. Insulin bound to the Leu 193 insulin receptor on the cell surface with normal affinity, although the mutation was in the alpha-subunit of the insulin receptor. Therefore, the Leu 193 mutation impaired proreceptor cleavage but not insulin binding.

Animals↗
PubMed1994

Spectral analysis of electromyogram in lumbar muscles: fatigue induced endurance contraction.

In the last few years, epidemiological studies have shown correlations between the low endurance capacity of the erector spinae muscle and low back pain (LBP). In this study, the function of the erector spinae muscle and localized muscle fatigue in LBP were investigated in both LBP patients and control subjects without LBP, using surface multi-channel electromyograms (EMG). Four positions (L1, L2, L4, L5) were chosen as representative locations for the different functions of the erector spinae muscle. Median frequency (fm) parameters of an EMG power density spectrum were monitored to quantify localized muscle fatigue. This research indicated a statistically significant difference (P < 0.05) in fm parameters between the LBP patients and the control subjects. The integrated electromyogram (iEMG) signals of LBP patients were considerably higher than for the control subjects during endurance isometric contraction. Our research suggested that human fatiguing erector spinae muscle, in submaximal voluntary contractions tests, induced a different firing order of motor unit spikes between two groups.

Adult↗
PubMed1994

Utilization of leucine methyl ester for the generation of hybridomas producing monoclonal antibodies specific to tumor-associated antigens.

In an attempt to obtain monoclonal antibodies specific to tumor-associated antigens, C3H/He mice were immunized with syngeneic MM2 tumor cells, and the primed spleen cells were fused with P3-X63-Ag8.653 myeloma cells. The outgrowth of hybridomas, however, was extremely low and monoclonal antibodies were not obtained. The reason for the low hybridoma growth was studied. It was found that MM2 cells used as the immunogen, the fusion partner myeloma cells and the resulting hybridomas shared at least one tumor-associated antigen, namely Q5 antigen. Because of this common antigen, cytotoxic cells, presumably cytotoxic T lymphocytes, which were lytic to the hybridomas, were induced during the culture for generation of the hybridomas. Removal of lysosome-rich cells, including cytotoxic T lymphocytes, from the primed spleen cells before the fusion by treatment with leucine methyl ester, a lysosomotropic agent, drastically improved the outgrowth of hybridomas. By this method, seven stable hybridoma clones producing monoclonal antibodies specific to tumor-associated antigens were obtained. Two of the seven clones were found to secrete monoclonal IgM species, which reacted with the extra-cellular region of the Q5 antigen. This procedure will be an option when production of monoclonal antibodies specific to cell-surface antigens is intended and outgrowth of hybridomas is unexpectedly low.

Animals↗
PubMed1994

HLA-B*3501-peptide interactions: role of anchor residues of peptides in their binding to HLA-B*3501 molecules.

Two HLA-B*3501 binding self-peptides, LPFDFTPGY (37F) and LPGPKFLQY (28H), were isolated from HLA-B*3501 molecules expressed by cultured human B lymphoid cells. Both sequences were consistent with previously reported motifs of HLA-B*3501 binding peptides which carry proline at position 2 and tyrosine at position 9 as anchor residues. Direct binding of these peptides to HLA-B*3501 molecules was quantitated by flow cytometry analysis of RMA-S cells. transfected with the HLA-B*3501 gene (RMA-S-B*3501). Both 37F and 28H peptides bound effectively to HLA-B*3501 molecules. Substitution of amino acids at position 2 and/or 9 of HLA-B*3501 binding peptides markedly reduced their binding to HLA-B*3501 molecules. These results indicate that two anchor residues, proline at position 2 and tyrosine at position 9 are critical in binding of peptides to HLA-B*3501 molecules. Insertion of up to four glycine residues at position 8 of the peptide 37F did not affect its binding affinity to HLA*3501 molecules. These results indicate that long peptides can effectively bind to HLA class I molecules provided that anchor residues are conserved.

Amino Acid Sequence↗
PubMed1994

New types of human papillomaviruses and intracytoplasmic inclusion bodies: a classification of inclusion warts according to clinical features, histology and associated HPV types.

Two new types of intracytoplasmic inclusion bodies (ICBs) associated with distinct clinical features, and the presence of DNA of distinct types of human papillomaviruses (HPVs) are reported. One hundred and seven cutaneous warts containing ICBs were grouped into three categories according to distinct clinicopathological features: 67 were wart lesions with well-known granular (Gr)-ICB, 13 were punctate keratotic lesions with filamentous (Fl)-ICB and 31 were pigmented warts with homogeneous (Hg)-ICB. Molecular biological studies were performed in order to assess a specific association of each group of warts with distinct types of HPV. HPV-1 DNA sequences were detected in all the lesions with a Gr-ICB. Punctate keratotic lesions with Fl-ICB were associated with HPV-63, which was newly cloned from such a lesion. One of the samples also contained HPV-1 DNA. Pigmented warts with Hg-ICBs contained one of the related HPVs, i.e. HPV-4, HPV-60 or a novel type of HPV, HPV-65. Based on these associations, a classification of inclusion warts is proposed.

Adolescent↗
PubMed1993

Pioglitazone ameliorates high glucose induced desensitization of insulin receptor kinase in Rat 1 fibroblasts in culture.

A new oral agent, pioglitazone, increases insulin sensitivity by activating receptor kinase in insulin-resistant rats. To clarify the mechanism, we studied in vitro effects of glucose and pioglitazone on the insulin receptor function using Rat 1 fibroblasts which expressed human insulin receptors. Insulin receptor kinase activity was impaired by incubating cells for 4 days in the presence of 27mM D-glucose. The glucose effect was time- and dose-dependent and also specific for D-glucose, since D-raffinose incubation had no effect. Pioglitazone treatment did not have any effect on intact receptor kinase. However, exposure of both 27mM D-glucose and 0.1 microM pioglitazone to the cells completely prevented the glucose-induced impairment of insulin receptor kinase activity, suggesting that pioglitazone might reverse the processes which are critical for the glucose-induced desensitization of insulin receptor kinase.

Animals↗