Biomedical subjects

T Iwamoto

Publications and source records attributed to T Iwamoto.

At least 145 records · Page 8Linked to original sources

PubMed1998

Transgenic mouse model for skin malignant melanoma.

We report here on a novel metallothionein-I (MT)/ret transgenic mouse line in which skin melanosis, benign melanocytic tumor and malignant melanoma metastasizing to distant organs develop stepwise. The process of tumor development and its malignant transformation in this line may resemble that of the human giant congenital melanocytic nevus that is present at birth and that frequently gives rise to malignant melanoma during aging. We observed an increase in the expression level and activity of the ret transgene during the disease progression. That increase in transgene expression accompanied an activation of mitogen-activated protein kinases (MAPKs) and c-Jun as well as matrix metalloproteinases. These results suggest that progressive dysregulation of the expression level of the ret transgene might play a crucial role in the malignant transformation of melanocytic tumors developed in the MT/ret transgenic mouse line.

Animals↗

PubMed1998

Diffusion-weighted MR imaging of the hippocampus and temporal white matter in Alzheimer's disease.

We investigated the changes in water diffusion in the hippocampus and the temporal white matter (the temporal stem) in eight patients with possible Alzheimer's disease (AD), 10 patients with probable AD, and 10 age-matched controls, using coronal diffusion-weighted magnetic resonance (MR) imaging. Apparent diffusion coefficients (ADCs) were derived for the three orthogonal axes and an index of diffusion anisotropy (IDA = ADC(max-min)/ADC(mean)) was then calculated. Although no significant differences were found in ADC and IDA values in the hippocampal body between controls and patients, vertical (superior-inferior) ADC values and ADC(mean) values in the temporal stem of patients with AD were significantly higher than those in controls, and IDA values were therefore significantly lower in patients with possible or probable AD than those in controls. Moreover, IDA values in the temporal stem were significantly correlated with the clinical severity. These results suggest that decreased fiber density, such as the disruption and loss of axonal membranes or myelin, occur early in the temporal stem, probably due to secondary degeneration related to grey matter pathology including the medial temporal lobe.

Aged↗

PubMed1998

Xanthine oxidase inhibition attenuates kupffer cell production of neutrophil chemoattractant following ischemia-reperfusion in rat liver.

We investigated the effects of the xanthine oxidase inhibitor, BOF-4272, on the production of cytokine-induced neutrophil chemoattractant (CINC) following reperfusion injury in rat liver. Ischemia was induced for 30 minutes by portal vein occlusion. Animals were pretreated with intravenous injection of BOF-4272 (1 mg/kg) or heparin (50 U/kg) 5 minutes before vascular clamp. Both BOF-4272 and heparin limited increases in the chemoattractant compared with nonpretreated rats. Pretreatment with BOF-4272 plus heparin resulted in an additive effect. Most cells immunostained for chemoattractant were macrophages in sinusoids. In vitro chemoattractant production by Kupffer cells isolated from animals pretreated with heparin or BOF-4272 was significantly lower than by Kupffer cells from nonpretreated animals. Expression of transcripts in liver for chemoattractant peaked 3 hours after reperfusion in nonpretreated animals, while pretreatment with heparin or BOF-4272 significantly decreased chemoattractant mRNA levels. In vitro chemoattractant transcription and production could be induced in naive Kupffer cells by hypoxanthine and xanthine oxidase, but BOF-4272 prevented these increases. We conclude that Kupffer cells release chemoattractant in response to oxygen radicals reducible by xanthine oxidase inhibition.

Animals↗

PubMed1998

Aqueous solubilization of transmembrane peptide sequences with retention of membrane insertion and function.

We recently reported that the peptide C-K4-M2GlyR mimics the action of chloride channels when incorporated into the apical membrane of cultured renal epithelial monolayers. C-K4-M2GlyR is one of a series of peptides that were prepared by the addition of lysine residues to the N- or C-terminus of the M2 transmembrane sequence of the brain glycine receptor. This study addresses how such modifications affect physical properties such as aqueous solubility, aggregation, and secondary structure, as well as the ability of the modified peptides to form channels in epithelial monolayers. A graded improvement in solubility with a concomitant decrease in aggregation in aqueous media was observed for the M2GlyR transmembrane sequences. Increases in short-circuit current (I(SC)) of epithelial monolayers were observed after treatment with some but not all of the peptides. The bioactivity was higher for the more soluble, less aggregated M2GlyR peptides. As described in our previous communication, sensitivity of channel activity to diphenylamine-2-carboxylate, a chloride channel blocker, and bumetanide, an inhibitor of the Na/K/2Cl cotransporter, was used to assess changes in chloride selectivity for the different assembled channel-forming peptides. The unmodified M2GlyR sequence and the modified peptides with less positive charge are more sensitive to these agents than are the more highly charged forms. This study shows that relatively insoluble transmembrane sequences can be modified such that they are easier to purify and deliver in the absence of organic solvents with retention of membrane association, insertion, and assembly.

Amino Acid Sequence↗

PubMed1998

Na+/Ca2+ exchanger overexpression impairs calcium signaling in fibroblasts: inhibition of the [Ca2+] increase at the cell periphery and retardation of cell adhesion.

We examined the Ca2+ handling property and cell function of CCL39 fibroblasts highly overexpressing the cardiac isoform (NCX1) of Na+/ Ca2+ exchanger. In NCX1 transfectants in 146 mM Na+, ionomycin, alpha-thrombin or thapsigargin only produced a small transient increase in [Ca2+]i compared to the large increase seen in control cells, although resting [Ca2+]i was not significantly different between these cells. In Na+-free medium, in contrast, the [Ca2+]i responses in NCX1 transfectants and control cells stimulated with these agents were not different, indicating that the Ca2+ content of the intracellular store(s) does not decrease on NCX1 transfection. The expression levels of the endoplasmic reticulum and plasma membrane Ca2+-ATPases, and thrombin- or serum-stimulated cell growth were not altered in NCX1 transfectants. The latter finding suggests that Ca2+ signaling in the nucleus is not impaired appreciably. On fluorescence imaging and confocal microscopy, we found that [Ca2+] did not increase in the peripheral cytoplasm of these cells treated with alpha-thrombin in Na+-containing medium. In these NCX1 transfectants, activation of the plasma membrane Ca2+-activated K+ channels by thrombin or ionomycin was markedly suppressed, and the integrin-mediated adhesion to substrate was significantly delayed compared with control cells. NCX1-overexpressing CCL39 cells thus seem to be a good model with which we can study the Ca2+-regulated membrane processes under physiologically relevant conditions.

Animals↗

PubMed1998

Effect of 20 days' bed rest on the reverse cholesterol transport system in healthy young subjects.

OBJECTIVES: To study the effects of 20 days of bed rest on HDL cholesterol, lipoprotein lipase, hepatic triglyceride lipase, cholesterol ester transfer protein and lecithin-cholesterol acyltransferase. DESIGN: A 20-day intervention study. SETTING: Makita general hospital. SUBJECTS: Five male and five female healthy participants, mean age 20.4 years, range 19-24 years. INTERVENTIONS: Twenty days of bed rest. MAIN OUTCOME MEASURES: Lipid, lipoprotein, lipoprotein lipase, hepatic triglyceride lipase, cholesterol ester transfer protein and lecithin-cholesterol acyltransferase. RESULTS: Fasting HDL, HDL2 and HDL3 cholesterol levels decreased from 1.748 to 1.404 mmol L(-1) (P < 0.01), from 0.807 to 0.628 mmol L(-1) (P < 0.01) and from 0.939 to 0.784 mmol L(-1) (P < 0.05), respectively, while VLDL triglyceride levels increased from 0.365 to 0.754 mmol L(-1) (P < 0.05). Plasma post-heparin lipoprotein lipase activity decreased from 0.494 to 0.418 micromol mL(-1) h(-1) (P < 0.01), but plasma post-heparin hepatic triglyceride lipase activity and cholesterol ester transfer protein activity did not change during bed rest. Lecithin-cholesterol acyltransferase activity increased from 72.5 to 84.8 nmol mL(-1) h(-1) (P < 0.001). CONCLUSIONS: Twenty days of bed rest induced a decline in HDL cholesterol levels and an increase in VLDL triglyceride levels. When considering lipoprotein lipase, hepatic triglyceride lipase, cholesterol ester transfer protein and lecithin-cholesterol acyltransferase as factors in the decreased HDL cholesterol, the contribution of lipoprotein lipase is suggested.

Adult↗

PubMed1998

Binding of influenza and paramyxoviruses to Group B Streptococcus with the terminal sialyl-galactose linkage.

Using the virus-binding assay and scanning electron microscopy (SEM), influenza A and B type viruses and two paramyxoviruses, parainfluenza (Sendai) and mumps viruses, were found to bind to Group B Streptococcus (GBS), type Ia and II, with the terminal sialyl-galactose linkage, although some viruses detached during the sample processing for SEM, and mumps virus did not bind to GBSIa. Binding of viruses eluted from GBS at 37 degrees C depended on combination of virus and GBS. The biological significance of these findings is discussed.

Bacterial Capsules↗

PubMed1998

Ultrastructure of murine tumour cell lines defective in MHC class I expression before and after interferon-gamma treatment.

Two tumour cell clones, 6D1 and 4C2 cells, which are defective both in the major histocompatibility gene complex (MHC) class I expression and in the endogenous antigen presentation, are recovered with interferon (IFN)-gamma treatment. The present study describes the ultrastructure of these cells by using scanning and transmission electron microscopy in relation to the effect of IFN-gamma treatment. The general morphology of these cells was found to be similar to each other and comparable to that of a tumour cell clone, 4A1 cells, of the same origin, normal in MHC class I expression; they exhibited a fibroblast-like appearance and had many blebs on all the cell surfaces, with desmosome-like junctions between cells. On IFN-gamma treatment, surface fine blebs appeared less, and mitochondria became more densely stained. Expression of MHC class I molecules on the cell surface was much higher in the IFN-gamma treated 6D1 and 4C2 cells than in untreated cells, when estimated by immunoelectron microscopy. The addition of an epitope peptide to these cells did not enhance the class I expression, which differed from other antigen presentation-defective cells such as RMA-S cells, nor change the cell surface morphology.

Animals↗

PubMed1998

Polymerase chain reaction analysis of the Y chromosome long arm in azoospermic patients: lack of the Y chromosome recognition motif (YRRM1) gene.

We analyzed DNA from a patient with azoospermia whose Y chromosome was cytogenetically normal. A total of 16 loci on the Y chromosome long arm were examined: 15 loci between DYS7E and DYZ1, and the Y chromosome RNA recognition motif (YRRM1) locus, a candidate gene for the azoospermic factor AZF. We did not detect the YRRM1 gene in this patient. This finding supports the theory that YRRM1 is an essential gene for spermatogenesis.

Adult↗

PubMed1998

Regulation of the Na+/H+ exchanger in fibroblasts overexpressing the Na+/Ca2+ exchanger.

To assess the role of Ca2+ in regulation of the Na+/H+ exchanger (NHE1),we used CCL-39 fibroblasts overexpressing the Na+/Ca2+ exchanger (NCX1). Expression of NCX1 markedly inhibited the transient cytoplasmic Ca2+ rise and long-lasting cytoplasmic alkalinization (60-80% inhibition) induced by alpha-thrombin. In contrast, coexpression of NCX1 did not inhibit this alkalinization in cells expressing the NHE1 mutant with the calmodulin (CaM)-binding domain deleted (amino acids 637-656), suggesting that the effect of NCX1 transfection involves Ca2+-CaM binding. Expression of NCX1 only slightly inhibited platelet-derived growth factor BB-induced alkalinization and did not affect hyperosmolarity- or phorbol 12-myristate 13-acetate-induced alkalinization. Downregulation of protein kinase C (PKC) inhibited thrombin-induced alkalinization partially in control cells and abolished it completely in NCX1-transfected cells, suggesting that the thrombin effect is mediated exclusively via Ca2+ and PKC. On the other hand, deletion mutant study revealed that PKC-dependent regulation occurs through a small cytoplasmic segment (amino aids 566-595). These data suggest that a mechanism involving direct Ca2+-CaM binding lasts for a relatively long period after agonist stimulation, despite apparent short-lived Ca2+ mobilization, and further support our previous conclusion that Ca2+- and PKC-dependent mechanisms are mediated through distinct segments of the NHE1 cytoplasmic domain.

Animals↗

PubMed1998

Differential inhibition of Na+/Ca2+ exchanger isoforms by divalent cations and isothiourea derivative.

We compared the properties of three mammalian Na+/Ca2+ exchanger isoforms, NCX1, NCX2, and NCX3, by analyzing the effects of Ni2+ and other cations as well as the recently identified inhibitor isothiourea derivatives on intracellular Na+-dependent 45Ca2+ uptake into CCL-39 (Dede) fibroblasts stably expressing each isoform. All these NCX isoforms had similar affinities for the extracellular transport substrates Ca2+ and Na+. Ni2+ inhibited 45Ca2+ uptake by competing with Ca2+ for the external transport site, with 10-fold less affinity in NCX3 than in NCX1 or NCX2. Ni2+ and Co2+ were most efficient in such discrimination of NCX isoforms, although their inhibitory potencies were less than those of La3+ and Cd2+. The monovalent cation Li+ stimulated 45Ca2+ uptake rate by all NCX isoforms similarly with low affinity, although the extent of stimulation was somewhat smaller in NCX1. On the other hand, the isothiourea derivative KB-R7943 was threefold more inhibitory to NCX3 than to NCX1 or NCX2. Thus distinct differences in the kinetic and pharmacological properties were detected between NCX3 and the other two isoforms.

Animals↗

PubMed1998

Larva currens: the usefulness of the agar plate method.

Creeping eruption caused by Strongyloides stercoralis is called larva currens, while those caused by other parasites are called larva migrans. To detect the parasite, the direct smear method was used. However, this method is not very sensitive in detecting S. stercoralis. A 62-year-old male with polyarteritis nodosa cutanea had an erythematous creeping eruption in various regions, such as his lumbar region, abdomen and thigh. The diagnosis of larva currens was made by the clinical appearance and the detection of S. stercoralis in his feces using the direct smear method and the agar plate method. This is the first reported case of larva currens in Japan. The agar plate method was useful and more sensitive than the usual direct smear method for detecting the S. stercoralis in feces and for elucidating the effects of treatment with antiparasitic drugs.

Adult↗

PubMed1998

Streptozotocin-induced diabetic cynomolgus monkey is a model of hypertriglyceridemia with low high-density lipoprotein cholesterol.

Hypertriglyceridemia with low high-density lipoprotein (HDL) cholesterol is a risk factor of cardiovascular disease. We attempted to create an animal model of hypertriglyceridemia with low HDL cholesterol by intravenously injecting 30 mg/kg body weight streptozotocin (STZ) to cynomolgus monkeys. This induced hypoinsulinemia and resulted in a decrease in postheparin plasma lipoprotein lipase (LPL) activity and LPL enzyme mass, reduction of plasma HDL cholesterol and elevation of triglycerides. Low HDL cholesterol subsequently caused a reduction of HDL2b cholesterol, while hypertriglyceridemia caused an elevation of very low-density lipoprotein (VLDL) triglyceridemia. Apolipoprotein CII, a co-factor of LPL, was not affected by STZ administration. These results show that hypertriglyceridemia with low HDL cholesterol results from a reduction of LPL activity without affecting apolipoprotein CII after STZ administration. The STZ-induced diabetic cynomolgus monkey is a model of hypertriglyceridemia with low HDL cholesterol, and may be potentially beneficial for studying atherosclerosis caused by hypertriglyceridemia with low HDL cholesterol.

Animals↗

PubMed1998

Effects of renin-angiotensin system blockade and dietary salt intake on left ventricular hypertrophy in Dahl salt-sensitive rats.

We studied the effects of chronic blockade of the renin-angiotensin system on hypertension and cardiac left ventricular hypertrophy (LVH) in Dahl salt-sensitive (DS) rats given a high-salt or low-salt diet. [Experiment 1] Twelve-week-old male DS rats were fed an 8% NaCl diet and received the angiotensin II receptor (AT1) antagonist, candesartan (3 mg/kg/d), the angiotensin converting enzyme inhibitor enalapril (30 mg/kg/d), or vehicle for 6 wk after 3 wk of 8% salt-loading. Neither candesartan nor enalapril with concomitant high salt-loading attenuated the blood pressure (BP) elevation. LVH was also not attenuated significantly by these treatments. [Experiment 2] After 8 wk of 8% salt-loading, the rats were given a 0.3% NaCl diet and concurrently received candesartan, enalapril, or vehicle for 5 wk. Switching from the high-salt to low-salt diet significantly decreased BP and left ventricular mass in the vehicle-treated animals. Both candesartan and enalapril normalized BP during salt-depletion; the blockade of the renin-angiotensin system produced an additive reduction in LVH. These findings suggest that sodium intake and hemodynamic load, but not the renin-angiotensin system, may be major determinants of the development of LVH in DS rats.

Angiotensin II↗

PubMed1998

Influence of inoculation site of combined oil-adjuvanted vaccine on the antibody response in chickens.

Inactivated oil-adjuvanted vaccines for ND, IB, and IC serotypes A and C (OILVAX NB2AC) have been marketed from 1993. In the outdoors, various inoculation sites have been used in chickens because to make the inoculation procedure easier. We examined whether differences would be obtained in the antibody response according to the inoculation sites; the subcutaneous inoculation into the back of the neck for OILVAX use, and the thigh, lower thigh, breast and shoulder muscle for the possible application of the inoculation outdoors. The clear order was not found in the NDV-HI titer, IBV-SN titer against Nerima or TM-86 among the inoculation sites used during the examination period. The IC serotypes A and C HI titers did vary among the inoculation sites; the subcutaneous inoculation produced the highest antibody titer, and high antibody titers were observed in the order of lower thigh muscle > or = thigh muscle > breast muscle > or = shoulder muscle inoculation.

Adjuvants, Immunologic↗

PubMed1998

Diffusion-weighted magnetic resonance and magnetization transfer imaging in the assessment of ischemic human stroke.

We compared characteristic features in ischemic stroke lesions from the hyperacute to the chronic stage on diffusion-weighted (DW) and magnetization transfer (MT) images with those on T2-weighted (T2W) images, and assessed changes in apparent diffusion coefficient (ADC), MT effect (MTe), and T2 ratios (infarct/normal) over time. DW images were particularly useful for detecting hyperacute infarcts within 6 hours of onset and in distinguishing acute lesions from chronic lesions. ADC ratios were lower within 7 days after onset and rose toward 1.0 in the subacute phase, becoming relatively isotense on ADC maps, but elevated thereafter. Although MTe ratios were unchanged or only subtly changed in the acute stage, they became significantly lower in the subacute and chronic stages. These combined magnetic resonance (MR) techniques were useful in the assessment of ischemic stroke and facilitated the determination of the age of cerebral infarct.

Aged↗

PubMed1998

[Cerebrovascular diseases in patients with arteriosclerotic aortic aneurysm and arteriosclerosis obliterans studied by carotid ultrasonography and by computed tomography of the brain].

To estimate the incidence of cerebrovascular diseases in arteriosclerotic aortic aneurysm (AA) and arteriosclerosis obliterans (ASO) and their characteristics, 92 patients with AA and 102 patients with ASO were studied with carotid ultrasonography and brain computed tomography (CT), and were compared with 49 patients with hypertension. The mean ages of the patients were 70 to 72 years old and all were male. Hypertension was common in the AA group: diabetes and cigarette smoking were common in the ASO group. Carotid plaque lesions seen on ultrasonography were significantly more common in the AA (66%) and ASO (85%) groups than in the patients with hypertension (39%). The mean carotid diameter was significantly greater in the AA group than in the other two groups. The mean wall thicknesses in the AA and ASO groups were greater than in the patients with hypertension. Computed tomography showed that low-density areas were also common in the AA group (56%) and ASO (53%) groups than in the patients with hypertension (24%). Most of the low-density areas were thought to be lacunae or dilated perivascular spaces in the subinsula and putamen. Moderately and highly severe periventricular lucencies were also common in the AA group. These findings indicate that carotid changes, seen in AA and ASO, reflected the characteristics of arterial lesions, and that arteriolosclerotic lesions were common in patients with AA and ASO. Therefore, cerebrovascular diseases should be taken into account in the management of patients with AA and ASO.

Aged↗

PubMed1998

Characterization of recombinant precursor proteins of the human seminal plasma sperm motility inhibitor synthesized in insect cells.

Human seminal plasma sperm motility inhibitor (SPMI) proteins which are exclusively secreted from seminal vesicles, inhibit sperm motility. It is secreted as biologically active 52 kDa and a mixture of 71 and 76 kDa precursor forms, which are identical to semenogelin-I and II (Sg-I and Sg-II), respectively. To understand the molecular mechanism underlying the inhibition of sperm motility by SPMI proteins, we expressed human Sg-I and Sg-II genes in insect cells using a baculovirus system. The baculoviruses expressing full-size Sg-I and Sg-II proteins that were N-terminally-tagged with a hexahistidine were selected, and were infected with Sf 21 cells. The Sg-I and Sg-II proteins were purified from infected cells by column chromatography using Ni-NTA resin 48 h after infection. The full-size Sg-I and Sg-II proteins were obtained in soluble forms. However, they tended to aggregate to form a gel, as expected from naturally occurring semenogelin. Both the purified recombinant Sg-I and Sg-II proteins showed strong SPMI activities with a complete inhibition of sperm motility at 60 units/mg, equivalent to the natural proteins. This production system that permits the generation of purified Sg-I and Sg-II proteins, as well as mutant derivatives, will be helpful for further study on male infertility.

Animals↗