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Biomedical subjects

K Iizuka

Publications and source records attributed to K Iizuka.

At least 37 records · Page 2Linked to original sources
PubMed1999

Requirement for membrane lymphotoxin in natural killer cell development.

Development of natural killer (NK) cells is thought to depend on interactions between NK progenitors and the bone marrow (BM) microenvironment; however, little is known about the molecular signals involved. Here we show that lymphotoxin (LT) provides an important signal for the development of both NK cells and NK/T cells. LTalpha-/- mice show marked reduction in splenic and BM NK and NK/T cell numbers and dramatically impaired NK and NK/T cell function. Mice deficient in either tumor necrosis factor receptor (TNFR)-I or TNFR-II have normal numbers of NK and NK/T cells, implying that neither of the TNFRs nor soluble LTalpha3 is required for development of these cell types. Reciprocal BM transfers between LTalpha-/- and wild-type mice suggest that close interactions between membrane LT-expressing NK cell precursors and LT-responsive radioresistant stromal cells are necessary for NK cell development. When LT-deficient BM cells are incubated with IL-15, NK cells are formed. In addition, LT-deficient BM cells produce IL-15 after activation. Thus, membrane LT appears to deliver a signal for NK cell development that is either independent of IL-15 or upstream in the IL-15 pathway. These results reveal a novel function for membrane LT in NK and NK/T cell development. They also support a cellular and molecular mechanism by which NK cell precursors themselves deliver essential signals, through the membrane ligand, that induce the microenvironment to promote further NK cell and NK/T cell development.

Animals↗
PubMed1999

Threshold-dependent DNA synthesis by pure pressure in human aortic smooth muscle cells: Gialpha-dependent and -independent pathways.

Mechanical forces related to pressure and flow are important for the etiology of atherosclerosis and hypertension. We hypothesized the presence of mechanosensors that were solely sensitive to pure atmospheric pressure in the absence of shear and tensile stresses. A pressure-loading apparatus was set up to examine the effects of atmospheric pressure on human aortic smooth muscle cells (HASMC). Pressure application of 140 to 180 mmHg produced DNA synthesis in a pressure-dependent manner. In contrast, pressure of 120 mmHg or less produced no significant change. Both extracellular signal-regulated kinase and c-Jun N-terminal kinase activities, but not p38 activity, were stimulated by pressures of more than 160 mmHg. Pertussis toxin (PTx) completely inhibited the pressure-induced increase of DNA synthesis under the high pressure of 200 mmHg. These data suggest that HASMC have a mechanosensing cellular switch for DNA synthesis which is sensitive to pure atmospheric pressure, and that the molecular switch is activated by pressure of more than 140 mmHg. The activation mechanism consists of PTx-sensitive and -insensitive pathways, and the former is activated by high pure pressure.

Aorta↗
PubMed1999

Pharmacological profile of MS-377, a novel antipsychotic agent with selective affinity for sigma receptors.

RATIONALE: MS-377 ((R)-(+)-1-(4-chlorophenyl)-3-[4-(2-methoxyethyl)piperazin-1-yl]me thyl-2- pyrrolidinone L-tartrate) was discovered as a new chemical entity with affinity for sigma receptors and without affinities for dopamine receptors. OBJECTIVE: In the present study, we examined the antipsychotic profile of MS-377 in several in vitro and in vivo experiments. METHODS: As in vitro assays, radioligand binding assays for sigma 1, sigma 2, D2 and 5-HT2 receptors were performed. As in vivo animal models, the effects of MS-377 on several behavioral models induced by phencyclidine (PCP), (+)-N-allylnormetazocine (NANM), apomorphine (Apo) and 5-hydroxytryptamine (5-HTP) were evaluated. All assay systems were conducted using the clinically active antipsychotic agents as reference standards. RESULTS: MS-377 displaced ligand bound to sigma 1 receptors in vitro. However, no such displacement was observed at sigma 2 or 5-HT2 receptors in vitro, or at D2 receptors either in vitro or in vivo. In behavioral studies, MS-377 inhibited both NANM- and PCP-induced head-weaving at low doses in mice and rats, whereas antipsychotic agents used in the present study were only effective against NANM-induced head-weaving behavior in mice. In addition, MS-377 antagonized Apo-induced climbing behavior and 5-HTP-induced head-twitching behavior in mice. MS-377 was inactive in models of extrapyramidal side effect (EPS) liability such as prevention of Apo-induced stereotypy and induction of catalepsy in rats. CONCLUSION: The present study demonstrated that MS-377 had not only anti-PCP activity but also anti-dopaminergic and anti-serotonergic activities in vivo, without acting directly through D2 or 5-HT2 receptors. Therefore, MS-377 could be a novel antipsychotic agent with clinical efficacy for overall symptoms of schizophrenia including its negative symptoms and without EPS liability.

Amisulpride↗
PubMed1999

Effects of isoproterenol on IL-2 and cAMP production in peripheral T cells from asthmatic and non-asthmatic subjects sensitive to Candida.

Immunity to Candida albicans (Candida) is characterized by a Th-1 type pattern of reactivity. Candida is rarely a cause antigen for bronchial asthma. Beta agonists have been found to inhibit secretion of IL-2 from T cells through intracellular cAMP elevation. We examined effects of isoproterenol (ISO) on Candida-stimulated T cells. Peripheral T cells obtained from six Candida-sensitive asthmatics, six Candida-sensitive non-asthmatic subjects, and six normal donors by Ficoll-Hypaque gradient centrifugation and nylon-wool column chromatography were incubated with Candida antigen or concanavalin A (Con A) in the absence or presence of ISO. Secretion of IL-2 and intracellular accumulation of cAMP were assayed by ELISA. Con A induced secretion of IL-2 in each of the three groups. Candida antigen induced IL-2 secretion in the normal and the non-asthmatic subjects, but not in the asthmatics. ISO, which reduced Con A-induced secretion of IL-2 in a dose-dependent manner, had no effect on Candida-induced secretion of IL-2. Although ISO increased the intracellular concentration of cAMP in untreated and Con A-treated T cells from all donors, cells from the normal and the non-asthmatic subjects, but not from the asthmatics, that were co-incubated with ISO and Candida had lower levels of cAMP than those treated with ISO alone. It is suggested that Candida antigen induces secretion of IL-2 and reduces ISO-inducible accumulation of cAMP in Candida-responsive IL-2 secreting cells, which may make Candida-induced secretion of IL-2 insensitive to ISO.

Asthma↗
PubMed1999

Interferon-gamma rescues TNF-alpha-induced apoptosis mediated by up-regulation of TNFR2 on EoL-1 cells.

Recent studies show that apoptosis is important for the resolution of chronic inflammation. Using a human myeloblastic leukemia cell line, EoL-1, we investigated the effect of interferon-gamma (IFN-gamma), which differentiates EoL-1 into monocyte/macrophage-like cells on Fas antigen (Fas)- and tumor necrosis factor-alpha (TNF alpha)-induced apoptosis. Both TNF and anti-Fas monoclonal antibody (CH-11) induced apoptosis of EoL-1 cells. Pretreatment with IFN-gamma for 72 hours enhanced the CH-11-induced apoptosis with up-regulation of Fas. However, the treatment markedly inhibited the TNF-induced apoptosis. In flow cytometric analysis, EoL-1 expressed two types of tumor necrosis factor receptors (TNFR1 and TNFR2), and the expression of TNFR2 but not of TNFR1 was up-regulated significantly after the IFN-gamma treatment. The TNF-induced apoptosis was mimicked by a TNFR1 stimulating antibody (htr-9), and was reversed by a TNFR1 blocking antibody (H398). Although the TNFR1-mediated cytotoxic signal was not affected by IFN-gamma pretreatment, blocking TNFR2 by a specific antagonistic antibody (utr-1) canceled the inhibitory effect of IFN-gamma. In conclusion, TNF-induced apoptosis was mediated preferentially by TNFR1, and the anti-apoptotic effect of IFN-gamma was result from up-regulated TNFR2 in EoL-1 cell line. This cell line is a useful model to provide new insights into crosstalk among Fas/FasL-, TNF-, and IFN-gamma-mediated signaling.

Antibodies, Monoclonal↗
PubMed1999

A major role for the rho-associated coiled coil forming protein kinase in G-protein-mediated Ca2+ sensitization through inhibition of myosin phosphatase in rabbit trachea.

1 G protein-mediated Ca2+ sensitization of airway smooth muscle contraction was investigated with respect to the relative importance of Rho-associated coiled coil forming protein kinase (ROCK) and protein kinase C (PKC). We examined the effects of Y-27632, a ROCK inhibitor, and GF 109203X, a PKC inhibitor, on guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS)-induced contraction in alpha-toxin- or beta-escin-permeabilized rabbit trachea. 2 Although pre-treatment with Y-27632 dose-dependently inhibited GTPgammaS (10 microM)-induced Ca2+ sensitization of alpha-toxin-permeabilized trachea, a Y-27632-insensitive component (approximately 16% of the maximum contraction) was retained during the early phase of the GTPgammaS response in the presence of Y-27632 (100 microM). 3 GF 109203X (5 microM) abolished 1 microM 4beta-phorbol 12, 13-dibutyrate (PDBu)-induced, but only partially inhibited the GTPgammaS-induced Ca2+ sensitization. A combination of Y-27632 (100 microM) and GF 109203X (5 microM) totally abolished the GTPgammaS response. 4 GTPgammaS caused only a small contraction in the absence of Ca2+. Wortmannin (30 microM), a myosin light chain kinase (MLCK) inhibitor, completely inhibited Ca2+-induced contraction. ATP-triggered contraction of the strip which had been treated with calyculin A (1 microM), a phosphatase inhibitor, in rigor solutions was markedly slowed by worthmannin (30 microM), but not by Y-27632 (100 microM), in the presence of GTPgammaS and Ca2+. 5 GTPgammaS, but not PDBu, contracted the beta-escin-permeabilized trachea in the absence of Ca2+, but the presence of Ca2+-independent MLCK. 6 We conclude that ROCK plays a primary role in G-protein-mediated Ca2+ sensitization, which requires MLCK activity, with minor contribution of PKC to the early phase of contraction, and PDBu utilizes conventional PKC(s) in airway smooth muscle.

Amides↗
PubMed1999

Serous-lined extramural tunnel technique for uretero-ileal implantation in urinary diversion.

PURPOSE: We present our initial experience of a serous-lined extramural tunnel technique for anti-refluxing uretero-ileal anastomosis in five cases of orthotopic ileal bladder and four cases of continent ileal pouch. METHODS/RESULTS: Ureters were implanted into serous-lined tunnels formed from a detubularized W-configurated ileal segment. Neither upper tract dilatation nor reflux were observed in any patient postoperatively. CONCLUSION: The technique can provide an effective uretero-ileal anastomosis for reflux prevention with minimal use of the ileal segment and without the use of any artificial materials.

Adolescent↗
PubMed1999

An alpha-cardiac myosin heavy chain gene mutation impairs contraction and relaxation function of cardiac myocytes.

Left Ventricular (LV) myocytes were isolated from 15-wk-old male mice bearing the Arg403 --> Gln alpha-cardiac myosin heavy chain missense mutation (alpha-MHC403/+), a model of familial hypertrophic cardiomyopathy. LV myocytes were classified morphologically: type I, rod shaped with parallel myofibrils; type II, irregularly shaped, shorter and wider than wild-type (WT) control cells, with parallel myofibrils; and type III, irregularly shaped with disoriented myofibrils. Compared with WT myocytes, alpha-MHC403/+ myocytes had fewer type I cells (WT = 74 +/- 3%, alpha-MHC403/+ = 41 +/- 4%, P < 0.01) and more type III cells (WT= 12 +/- 3%, alpha-MHC403/+ = 49 +/- 7%, P < 0.01). In situ histology also demonstrated marked myofibrillar disarray in the alpha-MHC403/+ hearts. With the use of video edge detection, myocytes were paced at 1 Hz (37 degrees C) to determine the effects of the mutation on myocyte function. End-diastolic length was reduced in mutant myocytes, but fractional shortening (% contraction) and sarcomere length were not. Velocity of contraction (-dL/dtmax) was depressed in mutant cells, but more in type II and III cells (-31%) than in type I cells (-18%). Velocity of relaxation (+dL/dt) was also depressed more in type II and III cells (-38%) than in type I cells (-16%). Using fura 2 dye with intracellular Ca2+ transients, we demonstrated that in alpha-MHC403/+ myocytes, the amplitude of the Ca2+ signal during contraction was unchanged but that the time required for decay of the signal to decrease 70% from its maximum was delayed significantly (WT = 159 +/- 8 ms; alpha-MHC403/+ = 217 +/- 14 ms, P < 0.01). Sarco(endo)plasmic reticulum Ca2+-ATPase mRNA levels in alpha-MHC403/+ and WT mice were similar. These data indicate that the altered cardiac dysfunction of alpha-MHC403/+ myocytes is directly due to defective myocyte function rather than to secondary changes in global cardiac function and/or loading conditions.

Action Potentials↗
PubMed1999

Relaxation of contracted rabbit tracheal and human bronchial smooth muscle by Y-27632 through inhibition of Ca2+ sensitization.

The mechanism of Ca2+ sensitization of contraction has not been elucidated in airway smooth muscle (SM). To determine the role of a small G protein, rhoA p21, and its target protein, rho-associated coiled coil-forming protein kinase (ROCK), in receptor-coupled Ca2+ sensitization of airway SM, we studied the effect of (+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl)cyclohexane carboxamide dihydrochloride, monohydrate (Y-27632), a ROCK inhibitor, on isometric contractions in rabbit tracheal and human bronchial SM. Y-27632 completely reversed 1 microM carbachol (CCh)-induced contraction of intact trachea with a concentration producing half-maximum inhibition of effect (IC50) of 1.29 +/- 0.2 microM (n = 5). Although 4beta-phorbol 12,13-dibutyrate (1 microM)-induced Ca2+ sensitization was relatively resistant to Y-27632 in alpha-toxin-permeabilized trachea, CCh (100 microM) plus guanosine triphosphate (GTP) (3 microM)- and guanosine 5'-O-(3'-thiotriphosphate) (10 microM)-induced contractions were relaxed completely by Y-27632 with IC50 of 1.44 +/- 0.3 (n = 6) and 1.15 +/- 0.3 microM (n = 6). Endothelin-1 (1 microM) plus GTP (3 microM)- developed force was also reversed by Y-27632 with IC50 of 4. 10 +/- 1.1 microM (n = 6) in the alpha-toxin-permeabilized bronchus. Both the rabbit and human SM expressed rhoA p21, ROCK I, and its isoform ROCK II. Collectively, rho/ROCK-mediated Ca2+ sensitization plays a central role in the sustained phase of airway SM contraction, and selective inhibition of this pathway may become a new strategy to resolve airflow limitation in asthma.

1-Methyl-3-isobutylxanthine↗
PubMed1999

An enzyme-linked immunosorbent assay using nuclear antigen for detection of feline herpesvirus 1 antibody.

To detect antibody against feline herpesvirus 1 (FHV-1) in the sera of cats, the sensitivity and specificity of an enzyme-linked immunosorbent assay (ELISA) using nuclear antigen was investigated. The standardized optical density readings (ODs) of the ELISA obtained by the 1-step serum dilution (1:80) method were compared with the serum neutralization test (SNT) results, with a correlation of 0.993, and with the hemagglutination inhibition (HI) test results, with a correlation of 0.851. The ODs for the ELISA titers were obtained using the serial serum dilution method and were compared with the SNT results, with a correlation of 0.933, and with the HI test results, with a correlation of 0.987. In the experimental infection of 4 specific-pathogen-free cats, the results of different serologic tests (SNT and HI) and the ELISA using the serial serum dilution method revealed rapid production of antibodies after inoculation, whereas the ELISA using the one-step serum dilution method indicated that titers increased more slowly. These results indicate that with the present ELISA using nuclear antigen, there are fewer demands on time and labor, making the method convenient for monitoring FHV-1 infection.

Animals↗
PubMed1999

A novel A-kinase anchoring protein in the heart interacts with G alpha 13.

A cDNA of a tentative A-kinase anchoring protein, presumably coupled with heterotrimeric GTP binding protein alpha 13 subunit (G alpha 13), was cloned from a human heart cDNA library. It was approximately 650 bases and its mRNA was expressed in the heart. Homology search of DNA sequences revealed that it was a novel cDNA with 84% homology with the partial sequence of rabbit cDNA of AKAP 120 without a stop codon. 3'-Rapid Amplification of cDNA Ends (3'-RACE) and yeast functional assay were performed to determine the 3'-end of the cDNA and ribosomal frameshifting was suggested as a translational mechanism. Here we report that a protein encoded by the cDNA may be involved in intracellular signal transduction via the G alpha 13 and PKA in hearts.

A Kinase Anchor Proteins↗
PubMed1999

A possible mechanism of primary ciliary dyskinesia: a case of a segmental defect in ciliary microtubules.

We report here a 13-year-old woman with cough, sputum and fever. The patient had both chronic sinusitis and bronchitis. Chest X-ray and computed tomographic scan of the chest revealed mucous bronchial filling and bronchiectasia in bronchi of bilateral lower lobes, right middle lobe and left upper lobe. Aerosol inhalation scintigraphy with 99mTechnetium demonstrated delays of the discharged tracer. On the basis of these findings, primary ciliary dyskinesia was suggested. This was confirmed by the findings from nasal biopsy with transmission electron microscopy where all of the microtubules were segmentally defected near the basal body in the cilia. On the basis of these findings, we diagnosed the patient with primary ciliary dyskinesia which may be due, at least in part, to segmental defect of ciliary microtubules.

Adolescent↗
PubMed1999

Effect of beta-agonists on production of cytokines by activated T cells obtained from asthmatic patients and normal subjects.

Intracellular levels of cAMP were found to regulate T cell activity. We examined whether beta2-agonists altered cytokine production and cyclic adenosine monophosphate (cAMP) accumulation in concanavalin A (ConA)-activated peripheral T cells from asthmatic patients. Procaterol and isoproterenol weakly decreased the ConA-elicited interleukin (IL)-4 and IL-5 secretion; however, the inhibitory effect of procaterol on the ConA-induced IL-2 secretion was inferior to that of isoproterenol in normal controls and was little in asthmatics. The intracellular accumulation of cAMP by procaterol was not altered compared with that by isoproterenol. Results suggest that there is a qualitative difference between procaterol- and isoproterenol-induced cAMP accumulation in T cells.

Adrenergic beta-Agonists↗
PubMed1999

[Homeostasis of antioxidant status in hemodialysis patients].

Oxidative stress, which occurs when there is excessive free-radical production or low antioxidant levels, makes significant contributions to pathogenesis in many human diseases. Cardiovascular disease is the major cause of mortality in patients receiving hemodialysis. For these patients, oxidative stress and increased lipid peroxidation may contribute to increased risk of atherosclerosis. The aim of this study was to determine if hemodialysis patients were associated with disturbance of homeostasis of antioxidant status. In this experiment, total antioxidant status of serum is measured by its ability to inhibit generation of free radicals from 2,2'-amino-di-[3-ethylbenzthiazole sulphonate] by metmyoglobin and hydrogen peroxide. Status of radical scavengers, such as serum total protein, albumin, uric acid and total bilirubin, was also measured. Blood were collected from three different episodes of hemodialysis. In the first group (n = 29), blood were collected before and after hemodialysis. In the second group (n = 29), blood were collected after dialysis and before next hemodialysis. In the third group (n = 8), blood were collected before hemodialysis. After last hemodialysis, patients started ingesting vitamin C and blood were collected before next hemodialysis. There was a marked reduction of total antioxidant status after hemodialysis in the first group. There was a marked increase in total antioxidant status before next hemodialysis in the second group. High doses of vitamin C caused increase in total antioxidant status in the third group. In conclusion, disturbance of homeostasis of total antioxidant status were observed in patients receiving hemodialysis. This may play a role in the pathogenesis in these groups.

Adult↗
PubMed1999

In vivo effects of calcium entry blockers on human parathyroid adenoma cells with special reference to calcium sensing ability and the hormone secretion.

We evaluated the effects of calcium-entry blockers on parathyroid hormone (PTH) secretion by human parathyroid adenoma cells in vitro. Nifedipine and bamidipine inhibited PTH secretion, while diltiazem had no significant effect. Cytosolic calcium concentrations were measured by use of the calcium-sensitive fluorescent dye fluo-3 with confocal laser scanning microscopy. Nifedipine increased the cytosolic concentration of calcium, whereas diltiazem decreased it. Results suggest that, in parathyroid adenoma cells, regulation of PTH secretion with respect to intracellular calcium concentration would be maintained despite differing response of intracellular calcium concentration following exposure to calcium-entry blockers.

Adenoma↗
PubMed1999

Distribution of doxorubicin in the bladder wall and regional lymph nodes after bladder submucosal injection of liposomal doxorubicin in the dog.

PURPOSE: Liposome-encapsulated doxorubicin (Lip-Dox) has increased therapeutic efficacy and reduced toxicity compared to free doxorubicin (Dox). To assess the utility of Lip-Dox for local control of bladder cancer, we examined the distribution of Dox in the bladder wall and the regional lymph nodes of dogs after bladder submucosal injection of Lip-Dox. MATERIALS AND METHODS: In 8 dogs (group SM), Lip-Dox (2 mg.:1 ml.) was injected into the submucosal layer of each lateral bladder wall by using a flexible cystoscope. The other 8 dogs (group IV) underwent intravenous injection of free Dox (4 mg.). Both groups of animals were sacrificed at 1, 3, 5 or 7 days after the injections. The concentration of Dox was measured in both the mucosal and muscle layers of 5 bladder wall sites and also in the external iliac lymph nodes bilaterally. RESULTS: The Dox-concentration in the lymph nodes of group SM was significantly higher (about 15-100 times) than that of group IV throughout the whole follow-up period. The Dox-concentration in the bladder wall for group SM was significantly higher than that in group IV (about 70-930 times at the lateral walls and 2-830 times at the other sites). CONCLUSION: The present results demonstrate that Lip-Dox injected into the bladder submucosally distributes well, both in the whole bladder wall and in regional lymph nodes and remains at a high concentration in these tissues for at least one week after injection.

Animals↗
PubMed1999

Enhanced continent mechanism of tapered ileum by extramural support from pouch-abdominal wall: an experimental study in dogs.

PURPOSE: To construct a reliable continent tube, which is easy to catheterize, we created and evaluated a new continent cutaneous diversion using a tapered ileum combined with extramural support from the pouch-abdominal wall. MATERIALS AND METHODS: Six dogs underwent a procedure in which two ileal segments were tapered and anastomosed to the ileal pouch. One of the segments (continent) was placed between the back surface of the rectus muscle and the wall of the ileal pouch creating a continent tube. The other segment (control) was brought out into the abdominal skin directly without any support from the pouch-abdominal wall. Urodynamic and radiological studies were carried out postoperatively in all dogs. RESULTS: In the continent tubes, the maximum closure pressure with a full pouch was significantly higher than those with an empty pouch (p<0.01). The maximum closure pressures of the continent tubes were significantly higher than those of the control tubes when the pouch was empty (p<0.01). The leak point pressures of the continent tubes were significantly higher than those of the control tubes (p<0.001). In all dogs, the retrograde radiogram of the continent tubes showed perfect canalization without stenosis. CONCLUSION: This study suggests that the continent mechanism of tapered ileum can be greatly enhanced by fixing it between the abdominal and pouch walls, also allowing easy catheterization in contrast to the submucosal tunnel technique.

Abdominal Muscles↗