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Biomedical subjects

K Iwai

Publications and source records attributed to K Iwai.

At least 109 records · Page 6Linked to original sources
PubMed1995

Differential protective action of cytokines on radiation-induced apoptosis of peripheral lymphocyte subpopulations.

It is established that soluble factors involved in cell growth can prevent apoptosis of hematolymphoid cell lines in factor-deprived situations. The present study investigates the possible protective effects of various cytokines on radiation-induced apoptosis of apparently quiescent lymphocyte subpopulations. The exposure to gamma-irradiation resulted in appreciable apoptotic changes in all of lymphocyte subpopulations. Natural killer (NK) cells were the most radiosensitive, whereas CD8+ T and B cells showed weaker susceptibility to radiation and CD4+ T cells were relatively radioresistant. The radiation-induced apoptosis in NK cells was significantly inhibited by IL-2. In addition to IL-2, IL-4 and IL-7 rescued both CD4+ and CD8+ T cells from radiation-induced cell death. The viability of B cells was maintained by the presence of IL-4 but not others in culture. Furthermore, we conclude that the protective effect by each cytokine on radiation-induced apoptosis might be partly attributed to enhancement of cellular expression of bcl-2 protein.

Adult↗
PubMed1995

Effects of MCI-225 on memory and glucose utilization in basal forebrain-lesioned rats.

The effects of MCI-225 on amnesia, the cerebral glucose metabolism, and choline acetyltransferase (ChAT) activity in basal forebrain (BF)-lesioned rats were studied in comparison with those of tacrine. Bilateral BF lesions with ibotenic acid impaired the performance in passive avoidance (PA) tasks. Single administration of MCI-225 (10 mg/kg, PO) after a 2-week postoperative recovery period, increased the escape latencies in the PA task, but was not statistically significant. Repeated administration of MCI-225 (0.3 and 1 mg/kg, PO for 6 days) significantly reversed the PA failure. The BF-lesioned rat exhibited a marked decrease in the local cerebral glucose utilization (LCGU) in the frontal cortex, parietal cortex, and caudate-putamen. MCI-225 (1 mg/kg, PO for 5 days) significantly ameliorated the reduction of the LCGU in the parietal cortex. MCI-225 did not change the decrease in the cortical ChAT activity induced by the BF lesion. Repeated administration of tacrine reversed the PA failure (0.3 mg/kg, PO) but failed to prevent the decrement in the LCGU and the ChAT activity. These results suggest that MCI-225 could be effective in the treatment of senile dementia of the Alzheimer type, which is accompanied with both deficit in the BF-cortex cholinergic neuron and cerebral glucose hypometabolism.

Animals↗
PubMed1995

Immunoblot analysis of cellular expression of Bcl-2 family proteins, Bcl-2, Bax, Bcl-X and Mcl-1, in human peripheral blood and lymphoid tissues.

The ability of Bcl-2 to inhibit apoptotic cell death is well established. Several homologues of the bcl-2 gene, such as bax, bcl-x or mcl-1, have recently been identified. Like Bcl-2, both Bcl-XL and Mcl-1 appear to function as repressors of apoptotic cell death, whereas Bax facilitates it, indicating possible interactions among them in the control of cellular survival. To investigate the in vivo role of expression of bcl-2 gene family products, immunoblot analysis using corresponding specific antisera was performed for peripheral blood cells and some lymphoid tissues in humans. We demonstrated that all Bcl-2 family proteins were expressed at various levels in hematolymphoid cell subpopulations isolated from peripheral blood, tonsil, spleen and thymus. Lymphoid expression of Bcl-2 family proteins tended to increase following activation, but declined with time in culture. Loss of Bcl-2 in cultured lymphoid cells was especially marked. Sole expression of Bax, but not other members of the Bcl-2 family, was observed on neutrophils, seemingly reflecting their shortest life-span among blood leukocytes. The results support the notion that a balance of expression of Bcl-2 family proteins may regulate the life and death of hematolymphoid cells at different stages of cell differentiation and activation.

Acute Disease↗
PubMed1995

Safety and pharmacokinetics of iotrolan in hysterosalpingography. Retention and irritability compared with Lipiodol.

RATIONALE AND OBJECTIVES: The authors compared the safety and pharmacokinetics of Iotrolan (water-soluble) in hysterosalpingography (HSG) with those of Lipiodol (oil-soluble). METHODS: Iotrolan and Lipiodol were administered intraperitoneally at doses of 100 mg iodine/kg to female rabbits. Retention in the body was investigated by x-ray imaging, plasma kinetics, and urinary and fecal excretion. Irritability in the abdomen was investigated by histologic examination. RESULTS: Iotrolan was entirely excreted into the urine within 2 days after administration. Conversely, Lipiodol was excreted into the urine, had a half-life of 50 days, and was retained for more than 21 days in the abdomen. Iotrolan induced no inflammatory reaction in the abdomen, whereas Lipiodol induced a marked abdominal inflammatory reaction, including granuloma formation. Iotrolan had no effect on iodine concentration in the thyroid; Lipiodol increased iodine concentration significantly. CONCLUSIONS: Iotrolan, which is a water-soluble and nonionic dimeric contrast medium, has potential greater safety for use in HSG than Lipiodol.

Abdomen↗
PubMed1995

Immunohistochemical detection of p53 overexpression in formalin-fixed, paraffin-embedded sections of endometrial carcinoma.

OBJECTIVE: In the past, immunohistochemical detection of p53 has been possible only in the case of fresh-frozen tissues. However using CM1 and an enhanced method based on microwave heating and protease digestion enabled the immunohistochemical detection of p53 overexpression in formalin-fixed, paraffin-embedded sections of endometrial carcinoma, although very few positive stainings were obtained without such an enhanced treatment. To evaluate the enhancement method, a comparative study was performed on frozen materials and paraffin-embedded samples. METHODS: Fifty-three frozen materials, including normal endometrial glands, endometrial hyperplasias and carcinomas, and paraffin-embedded samples from the same patients were used in this study. PAb1801 (mouse monoclonal antibody) was used to analyse p53 overexpression in the frozen sections, while CM1 (rabbit polyclonal anti-p53 antibody) was used for the paraffin sections. RESULTS: PAb1801 and CM1 staining on normal endometriums and endometrial lesions showed a significant degree of concordance between frozen and paraffin-embedded materials. CONCLUSION: Enhanced immunodetection of p53 in paraffin-embedded tissues will provide a useful alternative to the usual fresh-tissue assay.

Carcinoma↗
PubMed1995

Molecular cloning of a novel mitogen-inducible nuclear protein with a Ran GTPase-activating domain that affects cell cycle progression.

We have cloned a novel cDNA (Spa-1) which is little expressed in the quiescent state but induced in the interleukin 2-stimulated cycling state of an interleukin 2-responsive murine lymphoid cell line by differential hybridization. Spa-1 mRNA (3.5 kb) was induced in normal lymphocytes following various types of mitogenic stimulation. In normal organs it is preferentially expressed in both fetal and adult lymphohematopoietic tissues. A Spa-1-encoded protein of 68 kDa is localized mostly in the nucleus. Its N-terminal domain is highly homologous to a human Rap1 GTPase-activating protein (GAP), and a fusion protein of this domain (SpanN) indeed exhibited GAP activity for Rap1/Rsr1 but not for Ras or Rho in vitro. Unlike the human Rap1 GAP, however, SpanN also exhibited GAP activity for Ran, so far the only known Ras-related GTPase in the nucleus. In the presence of serum, stable Spa-1 cDNA transfectants of NIH 3T3 cells (NIH/Spa-1) hardly overexpressed Spa-1 (p68), and they grew as normally as did the parental cells. When NIH/Spa-1 cells were serum starved to be arrested in the G1/G0 phase of the cell cycle, however, they, unlike the control cells, exhibited progressive Spa-1 p68 accumulation, and following the addition of serum they showed cell death resembling mitotic catastrophes of the S phase during cell cycle progression. The results indicate that the novel nuclear protein Spa-1, with a potentially active Ran GAP domain, severely hampers the mitogen-induced cell cycle progression when abnormally and/or prematurely expressed. Functions of the Spa-1 protein and its regulation are discussed in the context of its possible interaction with the Ran/RCC-1 system, which is involved in the coordinated nuclear functions, including cell division.

3T3 Cells↗
PubMed1995

[Estimation of effective dose from CT examination].

Tissue or organ doses related to radiological risk were determined for four different types of CT scanners with a spiral scan function. Dose measurements were performed using a Rando phantom and two types of thermoluminescent dosimeters. The effective doses recommended by the International Commission on Radiological Protection in 1990 were evaluated using the tissue or organ doses determined with the phantom measurement. The resultant effective dose per CT examination ranged from 4.6 to 10.8 mSv for chest examination and from 6.7 to 13.3 mSv for upper abdominal examination. It should be noted that the effective dose from CT examination will be increased by increasing in the frequency of CT examinations and technical development of CT scanners.

Humans↗
PubMed1994

Molecular characterization of a second iron-responsive element binding protein, iron regulatory protein 2. Structure, function, and post-translational regulation.

Several genes critical to the uptake, sequestration, and utilization of iron are regulated at the post-transcriptional level. The mRNAs encoded by these genes contain highly conserved stem-loop structures called iron-responsive elements (IREs). IREs function as the nucleic acid-binding sites for a cytosolic RNA-binding protein called the IRE-binding protein or IRE-BP. Binding of the IRE-BP to IREs is reversibly regulated by the iron status of the cell. The IRE-BP is highly conserved among human, rat, mouse, and rabbit, and it is identical to the cytosolic form of aconitase. In this study, we demonstrate that a distinct human gene encoding a protein which is 57% identical to the initially described IRE-BP, now referred to as iron regulatory protein 1 or IRP1, is also capable of binding to IREs with the same in vitro affinity and specificity the originally identified protein. This second gene product, which we call IRP2, is expressed in many tissues, but its mRNA abundance and tissue distribution are different from IRP1. In most cell lines tested, levels of IRP2 are inversely regulated by iron levels due to iron-dependent regulation of the half-life of the protein. In addition to changes in total amounts of IRP2, we demonstrate that the IRE binding activity of IRP2 can also vary up to 4-fold in the absence of any change in IRP2 protein levels. The possible reasons for the existence of a second IRP are discussed.

Amino Acid Sequence↗
PubMed1994

Differential expression of bcl-2 and susceptibility to anti-Fas-mediated cell death in peripheral blood lymphocytes, monocytes, and neutrophils.

The recently identified Fas antigen (Ag) is a cell surface molecule that can mediate apoptosis. The cytoplasmic product of proto-oncogene bcl-2 has been shown to prolong the cellular survival by inhibiting apoptosis. To elucidate the physiologic significance of expression of both molecules, we examined the expression of Fas Ag and bcl-2 on blood leukocyte populations and evaluated their sensitivity to the cytolytic action of anti-Fas antibody. Although Fas Ag was expressed on a fraction of lymphocytes, both neutrophils and monocytes expressed Fas Ag constitutively. In contrast, there was marked difference among these leukocytes regarding bcl-2 expression. Lymphocytes expressed bcl-2 intensely, but monocytes showed weaker bcl-2 expression, and neutrophils were essentially absent for bcl-2 expression. Seemingly reflecting this lack of bcl-2-expression, neutrophils more easily underwent apoptotic cell death in vitro as compared with monocytes and lymphocytes. We showed that anti-Fas antibody affectively accelerated apoptotic cell death in neutrophils. However, the apoptosis-inducing effect of anti-Fas antibody was minimal on monocytes, and lymphocytes were resistant to this antibody. These results suggest that anti-Fas-mediated cell death may, in part, be determined by bcl-2 expression status in Fas+ lymphoid and hematopoietic cells.

Adult↗
PubMed1994

Efficient induction of immunoglobulin production in neonatal naive B cells by memory CD4+ T cell subset expressing homing receptor L-selectin.

The humoral response in newborns is mainly restricted to IgM production, which may be attributable to the naive nature of both B and T cells at birth. In light of the current evidence that memory (CD45RO+) CD4+ T cells help B cell differentiation, the present study was undertaken to examine whether a specified population within memory CD4+ T cells could induce the maturation of neonatal naive B cells. In the conventional PWM-stimulated cultures, the generation of IgG- and IgA-producing cells in addition to IgM production by neonatal B cells was significantly enhanced by co-cultures with memory, but not naive, CD4+ T cells. Memory CD4+ T cells were further divided into two populations based on expression of homing receptor L-selectin. These memory CD4+ T cell subpopulations appeared to behave in different fashions concerning help for Ig production by naive (sIgD+) and mature (sIgD-) B cells. L-selectin-negative memory CD4+ T cells exhibited helper function for Ig secretion by mature B cells. Intriguingly, Ig production by neonatal B cells as well as adult naive B cells, although less than that by mature B cells, was efficiently promoted by L-selectin-positive memory CD4+ T cells rather than L-selectin-negative ones. The results suggest that the capability of neonatal naive B cells to secrete IgG and IgA can be elicited by appropriate T-cell signals, especially from the L-selectin-positive population within memory CD4+ T cells, seemingly indicating its possible role for isotype switching in B cells.

Adult↗
PubMed1994

Ionizing radiation induces apoptotic cell death in human TcR-gamma/delta+ T and natural killer cells without detectable p53 protein.

The p53 tumor suppressor gene has been shown to be involved in programmed cell death, apoptosis, in murine immature thymocytes after treatment with ionizing radiation. Ionizing radiation also induces apoptosis in peripheral mature lymphocytes. In this work, we investigated the p53 participation in radiation-induced apoptosis in human peripheral blood lymphocytes (PBL) subpopulations. Exposure to gamma-irradiation resulted in an appreciable induction of apoptotic cell death in TcR-alpha/beta+ (CD4+ and CD8+) T cells, TcR-gamma/delta+ T cells, B cells and natural killer (NK) cells, as assessed by DNA fragmentation as well as the morphological characteristics. Importantly, it was found that there was a marked difference among PBL subpopulations as regards the induction of p53 protein by gamma-irradiation. Similar to previous observations for murine thymocytes, p53 induction in TcR-alpha/beta+ T cells and B cells after gamma-irradiation was evident by Western blot analysis. Radiation-induced apoptosis in TcR-alpha/beta+ T cells and B cells was efficiently inhibited by cycloheximide, indicating the requirement of de novo protein synthesis, including p53 protein, for radiation-induced apoptosis in both subpopulations. In marked contrast, no identifiable levels of p53 protein were induced in either TcR-gamma/delta+ T or NK cells after gamma-irradiation. In addition, it was demonstrated that radiation-induced cell death in TcR-gamma/delta+ T and NK cells could be prevented by interleukin-2, but not by cycloheximide. These results imply that radiation-induced lymphocytic apoptosis can be mediated by p53-dependent or -independent mechanisms.

Adult↗
PubMed1994

Effects of capsaicin analogs on adrenal catecholamine secretion in rats.

To assess the relationship among the structure, pungency and thermogenic action, a series of capsaicin analogs with saturated acyl moieties (heptanoyl to eicosanoyl vanillylamide) were synthesized. Pungency of the compounds and the thermogenic action, which was examined by the potential of the compounds (655 nmol/kg, i.v.) to enhance adrenal catecholamine secretion for 15 min in anesthetized rats, were compared. On the chain length of the acyl moieties of the analogs, nonanoyl to octadecanoyl vanillylamide caused strong adrenal catecholamine secretion, but heptanoyl vanillylamide and eicosanoyl vanillylamide caused weak or no response. Pungent analogs except heptanoyl vanillylamide and non-pungent analogs except eicosanoyl vanillylamide had strong potency to secrete adrenal catecholamine.

Adrenal Medulla↗
PubMed1994

Involvement of 4F2 antigen expressed on the MHC-negative target cells in the recognition of murine CD3+CD4-CD8- alpha beta (V alpha 4/V beta 2) T cells.

T cells of an unique phenotype (CD3+CD4-CD8- alpha beta TCR+) develop in vitro from the hematopoietic progenitors, the majority of which carry homologous alpha beta TCR (V alpha 4J alpha 28/V beta 2D beta 1.1J beta 2.6). In the present study, antigen corresponding to the particular alpha beta TCR was investigated, taking advantage of the fact that growth of T cell hybridomas was arrested by their TCR stimulation. Results indicated that both syngeneic and allogeneic thymocytes, particularly from newborn mice, could specifically inhibit the proliferation of a T cell hybridoma with the V alpha 4/V beta 2 TCR (15H1.2). Proliferation of neither TCR-missing hybridoma subclones nor those with unrelated alpha beta TCRs was affected at all. It was also found that embryonal carcinoma (EC) cells without classical MHC antigens could specifically inhibit the proliferation of 15H1.2 cells. We then raised a mAb, 14.37, against an EC line, OTF9, that could interfere with the ability of them to inhibit the growth of 15H1.2. Pretreatment of 15H1.2 cells with anti-V beta 2 and OTF9 cells with 14.37 mAb respectively completely abrogated the growth inhibition of 15H1.2 by OTF9. The 14.37 antigen was a 120 kDa heterodimer glycoprotein consisting of 85 and 36 kDa proteins. In normal lymphoid tissues, the expression of 14.37 antigen exhibited an apparently inverse relationship with that of class I MHC antigens. Thus, ontogenically it was strongly expressed in fetal and newborn mice, rather rapidly declined thereafter, and remained at very low levels in adult organs. In a given stage, the distribution of 14.37 antigen and class I MHC was rather exclusive to each other.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Mature helper T cell requirement for immunoglobulin production by neonatal native B cells injected intraperitoneally into severe combined immunodeficient (SCID) mice.

It is accepted that human neonatal naive B cells produce mainly IgM in vivo as well as in vitro. Our previous work has demonstrated that i.p. injection of neonatal B cells together with adult mature T cells induces substantial levels of human IgG in the serum of SCID recipient mice. The present study was further attempted to determine the cellular components required for immunoglobulin production by neonatal B cells in SCID mice. When neonatal B and adult T cells were transferred into the SCID mice, human immunoglobulins, largely of IgG, were maximally detected in the serum around 6 weeks after a cell transfer. Depletion of CD4+ T cells from adult T cells resulted in undetectable levels of human immunoglobulin in the serum. By contrast, CD4+ T cell-enriched populations exhibited an enhancing effect on immunoglobulin production by neonatal B cells. Higher levels of immunoglobulin, including IgA and IgM, were detected in the peritoneal fluid than in the serum as early as 2 weeks after the cell transfer. Human T cells expressing activation antigens such as CD45RO and HLA-DR antigens were identified in the peritoneal lavages. These results suggest that neonatal naive B cells are able to differentiate into cells producing all classes of immunoglobulin in the presence of mature CD4+ T cells in a SCID mouse environment. The peritoneal cavity of SCID mice appears to provide a suitable place for immune responses by human cells, possibly in association with a certain xenogeneic reaction.

Adult↗
PubMed1994

Lymphokine-activated killer cytotoxicity against pancreas adenocarcinoma cell lines and vascular endothelial cells.

Eight pancreas carcinoma cell lines of duct cell origin (PCI-6, 10, 19, 24, 35, 43, 55, and 64) were established. Using one of these lines, PCI-24, human umbilical vein endothelial cells (HUVEC), and several recombinant cytokines, conditions and specificity of anti-PCI LAK induction were investigated, with the focus on a search for lymphokine-activated killer (LAK) activity that differentiates neoplastic (PCI) from non-neoplastic (HUVEC) cells. Interferon-gamma (IFN-gamma), IFN-alpha, IL-4, IL-6, and IL-7, but not tumor necrosis factor-alpha (TNF-alpha) or IL-1 beta, induced a weak LAK activity against PCI-24, whereas IL-2-induced (1000 U/mL) LAK exhibited a far more potent cytotoxicity. When these cytokines were added at the suboptimal dose IL-2 (100 U/mL), no significant augmentation in LAK activity was induced. Staphylococcal protein A (SpA) induced LAK activity as potent as that seen with IL-2 (1000 U/mL). Both IL-2-induced and SpA-induced LAK had a potent, dose-dependent cytotoxicity against HUVEC. HUVEC inhibited both IL-2- and SpA-induced LAK cytotoxicity against PCI-24 to almost the same extent as seen with PCI-24. Thus, two potent LAK-inducers did not generate LAK activity that differentiates neoplastic from non-neoplastic cells. Thus, in vitro cytotoxicity of LAK against non-neoplastic endothelial cells is unavoidable when handling cytokines in LAK induction.

Adenocarcinoma↗
PubMed1994

Acute thrombocytopenic purpura associated with primary Epstein-Barr virus infection.

Acute idiopathic thrombocytopenic purpura (ITP) often appears to be related to the sensitization by some viral infections. However, the causative viral agents are not identified in most cases. Although the primary infection with Epstein-Barr virus (EBV) occurs during early childhood in Japan, the majority of cases are usually asymptomatic. A minority are associated with acute infectious mononucleosis (IM), which is characterized by fever, tonsillitis, lymphadenopathy, splenomegaly and liver dysfunction. In this report, three cases are described of children with EBV-induced ITP who clinically had atypical findings of IM. Their primary EBV infections were confirmed by serological test and, in addition, were verified by the enhanced expression of activation antigens (HLA-DR and CD45RO) on T cells as well as the inverted ratio of CD4+ to CD8+ subsets. These observations imply that ITP can occur as one of the host responses during primary EBV infections, irrespective of clinical manifestations. Evaluation of lymphocyte subpopulations may be useful for the assessment of primary EBV infection in ITP.

Acute Disease↗
PubMed1994

Beta-adrenergic stimulation disassembles microtubules in neonatal rat cultured cardiomyocytes through intracellular Ca2+ overload.

Catecholamine cardiotoxicity is attributable in part to Ca2+ overload. To test whether the cytoskeletal structures of microtubules in cardiomyocytes are reversibly injured by catecholamine through excessive Ca2+ influx, morphological changes in the microtubules of neonatal rat myocytes were studied by immunohistochemical technique during exposure to norepinephrine (NE). In intact myocytes, microtubules appeared as a filamentous network throughout the cytoplasm and around the nucleus. NE exposure (10 mumol/L) for > 30 minutes elicited microtubular disassembly in a duration-dependent fashion without any irreversible change in sarcomere structure, and this abnormality recovered within 24 hours after cessation of stimulation. Microtubular disruption scores obtained by semiquantitative assessment were significantly increased in a dose-dependent manner (10.8 +/- 4.0 in the control condition, 23.4 +/- 4.7 at 60 minutes with 10 mumol/L NE), whereas they were significantly attenuated by pretreatment with propranolol (100 mumol/L; score, 11.8 +/- 3.3) but not with phentolamine (100 mumol/L; score, 26.4 +/- 4.8). Isoproterenol (1 mumol/L) and denopamine (10 mumol/L) mimicked the effects of NE, but phenylephrine did not, indicating that NE-induced microtubular disassembly is mediated by beta 1-adrenergic receptor stimulation. This beta-adrenergic receptor-mediated insult was significantly attenuated by a decrease in Ca2+ concentration in the medium from 2 to 0.5 mmol/L and by pretreatment with diltiazem (1 mumol/L). In contrast, microtubular disassembly was induced by an increase in Ca2+ concentration in the medium and an administration of the Ca2+ ionophore A23187, even without beta-adrenergic receptor stimulation. Involvement of intracellular hypoxia and activation of Ca(2+)-calmodulin-dependent kinase or Ca(2+)-dependent neutral protease were excluded from possible mechanisms; however, inhibition of tubulin polymerization by excessive Ca2+ influx during beta-adrenergic receptor stimulation may be primarily involved. We conclude that microtubular structures that support cellular integrity are reversibly injured by beta-adrenergic receptor stimulation through excessive Ca2+ influx.

Adrenergic beta-Agonists↗