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Biomedical subjects

H Iwai

Publications and source records attributed to H Iwai.

At least 55 records · Page 3Linked to original sources
PubMed1999

Conformational changes of the BS2 operator DNA upon complex formation with the Antennapedia homeodomain studied by NMR with 13C/15N-labeled DNA.

The NMR structures have been determined for a 13C/15N doubly labeled 14 base-pair DNA duplex comprising the BS2 operator sequence both free in solution and in the complex with the Antennapedia homeodomain. The impact of the DNA labeling is assessed from comparison with a previous structure of the same complex that was determined using isotope labeling only for the protein. Differences between the two structure determinations are nearly completely limited to the DNA, which retains the global B -conformation of the free DNA also in the complex. Local protein-induced conformational changes are a narrowing of the minor groove due to the interaction with the N-terminal arm of the homeodomain, and changes of the sugar puckers of the deoxyriboses G5 and C6, which are apparently induced by van der Waals interactions with Tyr25, and with Gln50 and Arg53, respectively. The high conservation of these amino acid residues in homeodomains suggests that protein-induced shifts in some sugar puckers contribute to the affinity of homeodomains to their cognate DNA. The data obtained here with the Antennapedia homeodomain-DNA complex clearly show that nucleic acid isotope-labeling can support detailed conformational characterization of DNA in complexes with proteins, which will be indispensable for structure determinations of complexes containing globally distorted DNA conformations.

Antennapedia Homeodomain Protein↗
PubMed1999

T cells infiltrating from the systemic circulation proliferate in the endolymphatic sac.

It has been reported that autoimmune mechanisms are involved in the development of inner ear disorders such as Meniere's disease and steroid-responsive sensorineural hearing loss. In the present study, using an animal model for graft-versus-host disease, we investigated the immune regulatory mechanism in the endolymphatic sac and demonstrated that donor T cells injected into the systemic circulation of recipients infiltrate and proliferate in the perisaccular region. These findings suggest that immunocompetent cells are supplied from the systemic circulation through blood-labyrinth and blood-endolymph barriers into the endolymphatic sac, and that the endolymphatic sac allows these cells to proliferate locally as a local immune defense. It therefore seems likely that the endolymphatic sac plays a crucial role in not only graft-versus-host disease but also autoimmune inner ear disorders.

Animals↗
PubMed1999

Glucose metabolism and insulin sensitivity in transgenic mice overexpressing leptin with lethal yellow agouti mutation: usefulness of leptin for the treatment of obesity-associated diabetes.

Leptin acts as an adipocyte-derived blood-borne satiety factor that can increase glucose metabolism. To elucidate the therapeutic implications of leptin for obesity-associated diabetes, we crossed transgenic skinny mice overexpressing leptin (Tg/+), which we have developed recently, and lethal yellow KKAy mice (Ay/+), a genetic model for obesity-diabetes syndrome, and examined the metabolic phenotypes of F1 animals. At 6 weeks of age, plasma leptin concentrations in Tg/+ mice with the Ay allele (Tg/+:Ay/+) were significantly higher than those in Ay/+ mice. Although no significant differences in body weight were noted among Tg/+:Ay/+ mice, Ay/+ mice, and their wild-type lean littermates (+/+), glucose and insulin tolerance tests revealed increased glucose tolerance and insulin sensitivity in Tg/+:Ay/+ compared with Ay/+ mice. However, at 12 weeks of age, when plasma leptin concentrations in Ay/+ mice were comparable to those in Tg/+:Ay/+ mice, Tg/+:Ay/+ mice developed obesity-diabetes syndrome similar to that of Ay/+ mice. Body weights of 12-week-old Tg/+:Ay/+ and Ay/+ mice were reduced to those of +/+ mice by a 3-week food restriction; when plasma leptin concentrations remained high in Tg/+:Ay/+ mice but were markedly reduced in Ay/+ and +/+ mice, glucose tolerance and insulin sensitivity in Tg/+:Ay/+ mice were markedly improved as compared with Ay/+ and +/+ mice. The present study demonstrates that hyperleptinemia can delay the onset of impaired glucose metabolism and accelerate the recovery from diabetes during caloric restriction in Tg/+:Ay/+ mice, thereby suggesting the potential usefulness of leptin in combination with a long-term caloric restriction for the treatment of obesity-associated diabetes.

Aging↗
PubMed1999

Increased glucose metabolism and insulin sensitivity in transgenic skinny mice overexpressing leptin.

Excess of body fat, or obesity, is a major health problem and confers a higher risk of cardiovascular and metabolic disorders such as diabetes, hypertension, and coronary heart disease. Leptin is an adipocyte-derived satiety factor that plays an important role in the regulation of energy homeostasis, and its synthesis and secretion are markedly increased in obese subjects. To explore the metabolic consequences of an increased amount of leptin on a long-term basis in vivo, we generated transgenic skinny mice with elevated plasma leptin concentrations comparable to those in obese subjects. Overexpression of leptin in the liver has resulted in complete disappearance of white and brown adipose tissue for a long period of time in mice. Transgenic skinny mice exhibit increased glucose metabolism accompanied by the activation of insulin signaling in the skeletal muscle and liver. They also show small-sized livers with a marked decrease in glycogen and lipid storage. The phenotypes are in striking contrast to those of recently reported animal models of lipoatrophic diabetes and patients with lipoatrophic diabetes with reduced amount of leptin. The present study provides evidence that leptin is an adipocyte-derived antidiabetic hormone in vivo and suggests its pathophysiologic and therapeutic implications in diabetes.

Animals↗
PubMed1999

[Evaluation of frozen section diagnosis of parotid gland tumors].

A retrospective study is presented comparing the results of 167 frozen section diagnoses of surgical extirpated parotid gland tumors with permanent-section diagnoses. Percentages of correct diagnosis for malignancy (cases correctly classified as benign or malignant tumors) and of correct diagnosis for histopathology (cases in which frozen section diagnosis and permanent-section diagnosis were identical) were calculated. Percentages of correct diagnosis for malignancy in all cases, benign cases, and malignant cases were 98.8%, 99.3%, and 95.8%, respectively. Percentages of correct diagnosis for histopathology in all cases, benign cases, and malignant cases were 94.0%, 97.2%, and 75.0%, respectively. These results are superior to the previous reports both of frozen section diagnosis and of fine-needle aspiration biopsy diagnosis although the data for histopathological diagnosis in malignant tumors are average compared to previous reports. We conclude that diagnoses of most parotid gland tumors based on frozen section examination are reliable and accurate, but caution should be exercised in malignant tumors diagnosis.

Biopsy, Needle↗
PubMed1999

[Clinical study of parotid tumors: a 20 year statistical analysis of 633 cases].

During the 20 years from 1977 to 1996, 633 cases underwent excisions of parotid tumors (539 benign and 94 malignant) in the department of Otolaryngology of Kansai Medical University. The incidence of Warthin's tumors in the years from (1987 to 1996) was higher than that in the years from 1977 to 1986. On the other hand, the incidence of mucoepidermoid carcinomas was less than in previous reports. Tumors accompanied with spontaneous pain or facial nerve palsy and with invasion to both lobes frequently indicated malignancy. Facial nerve palsy caused by either benign or malignant tumors before operation showed no improvement after surgery. The incidences of facial nerve palsy (1.0% in benign, and 18.3% in malignant) and Frey's syndrome (17.8% in benign, and 18.3% in malignant) after surgery were lower than those in other reports of both benign and malignant tumors. Five-year mortality was 76.1%. All deaths that occurred five years after operation involved highly grade malignant tumors.

Adenolymphoma↗
PubMed1999

Experimental impression tray fabricated with a NiTi shape memory alloy plate.

A small experimental impression tray was fabricated with a NiTi shape memory alloy plate. After recovery of the shape memory effect, the upper rims of the tray holding the impression were opened to some extent, the resistance during removal of the model from the impression was significantly decreased compared to a commercially available tray and the tray before recovery of the shape memory effect. The pull-out force of the model from the impression was 23.5(0.2)N for the commercially available tray, 23.5(3.9)N for the experimental tray before recovery of the shape memory effect and 14.7(4.0)N after recovery of the shape memory effect (heated for 15 min at 70 degrees C). Therefore the tray should be useful in teeth fracture free modeling.

Dental Alloys↗
PubMed1998

Improvement of spectrometer energy resolution for high-resolution photoelectron spectroscopy.

For high-energy-resolution photoelectron spectroscopy using synchrotron radiation, the energy resolution of a commercial compact photoelectron spectrometer (hemispherical concentric spectrometer) was improved by reducing the size of the entrance and detector slits and optimizing the operation conditions of the lens voltage. Under the optimized conditions, ray-tracing simulations show that severe spectral intensity decreases can be avoided. An energy resolution of 6.2 meV and a resolving power of 8100 at a kinetic energy of 50 eV were experimentally obtained.

Journal Article↗
PubMed1998

Enzymatic amplification and expression of bovine interleukin-1 receptor antagonist cDNA.

cDNA generated from lipopolysaccharide-stimulated bovine peripheral blood mononuclear cells was used to amplify and clone the bovine interleukin-1 receptor antagonist (IL-1ra) using primers derived from semi-conserved regions between human and mouse IL-1ra sequences. 5' and 3' terminal sequences of bovine IL-1ra were amplified by 5' and 3' rapid amplification of cDNA ends. The deduced amino acid sequence of bovine IL-1ra demonstrated 80%, 78%, 78%, 77% and 76% homology with human, mouse, rat, rabbit and equine sequences, respectively. Recombinant bovine IL-1ra produced in Escherichia coli suppressed the growth inhibitory activity of bovine IL-1beta on A375 cells in a dose-dependent manner, indicating that the present bovine IL-1ra cDNA encodes biologically active proteins.

Amino Acid Sequence↗
PubMed1998

Solvent magnetization artifacts in high-field NMR studies of macromolecular hydration.

With the use of high magnetic fields and improved quality factor ratings of the probeheads in modern NMR spectrometers, radiation damping becomes more and more important. In addition, the demagnetizing field effect from protonated solvents gains significance with the increase of the magnetic field strength. During a typical NMR pulse sequence the magnetic fields caused by these effects become time-dependent, which makes the system nonlinear and may, for example, measurably influence the precession frequencies of all nuclei in the sample. Since radiation damping can affect signals that are several kilohertz away from the solvent resonance, the amplitude, phase, and frequency of the desired signals can be disturbed so as to give rise to spectral artifacts. In particular when difference methods are used to obtain the final spectrum, the data sets may be severely deteriorated by such artifacts. This paper investigates effects from the demagnetizing field and from radiation damping with a selection of pulse sequences in use for studies of macromolecular hydration, and strategies are described for the detection and elimination of the ensuing artifacts.

Artifacts↗
PubMed1998

Induction of immune-mediated hearing loss in SCID mice by injection of MRL/lpr mouse spleen cells.

Induction of immune-mediated hearing loss in SCID mice by injection of MRL/lpr mouse spleen cells The MRL/lpr mouse, which has a mutation in the Fas gene encoding a cell-surface receptor for apoptosis, shows an accumulation of abnormal immunocompetent cells and SLE-like disease. It has recently been reported that this mouse also manifests sensorineural hearing loss (SHL) with cochlear pathology at 20 weeks of age. We examined the effects of injecting MRL/lpr spleen cells on the development of SHL in severe combined immunodeficient (SCID) mice, which originally develop neither SHL nor cochlear pathology. Immune-mediated SHL and cochlear pathology were, indeed, transferred to the SCID mice by the injection of spleen cells from the MRL/lpr mice. These findings suggest that cell-mediated immunity is involved in the development of SHL and cochlear pathology.

Animals↗
PubMed1998

Removal of endotoxin and cytokines by plasma exchange in patients with acute hepatic failure.

OBJECTIVES: To compare the circulating concentrations of endotoxin and cytokines in patients with fulminant hepatitis and patients with the severe form of acute hepatitis, and to assess the effects of plasma exchange on the circulating concentrations of these inflammatory mediators in patients with acute hepatic failure. DESIGN: Prospective, consecutive entry study of patients meeting fulminant hepatitis criteria and the severe form of acute hepatitis criteria. SETTING: University hospital, intensive care unit. PATIENTS: Five patients with fulminant hepatitis, eight patients with the severe form of acute hepatitis, two patients with acute-on-chronic hepatic failure, and one patient with postoperative hepatic failure. INTERVENTIONS: Plasma endotoxin, serum tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and IL-6 were determined on admission in five patients with fulminant hepatitis and eight patients with the severe form of acute hepatitis. Circulating concentrations of the inflammatory mediators were measured before and after a single course of plasma exchange in eight patients with acute liver failure, including five patients with fulminant hepatitis, two patients with acute-on-chronic hepatic failure, and one patient with postoperative hepatic failure. MEASUREMENTS AND MAIN RESULTS: TNF-alpha and IL-6 in patients with fulminant hepatitis were significantly higher than in patients with the severe form of acute hepatitis, whereas endotoxin concentrations did not differ between patients with fulminant hepatitis or the severe form of acute hepatitis. IL-1beta was not detectable in patients with either fulminant hepatitis or the severe form of acute hepatitis. Plasma endotoxin concentrations decreased immediately after plasma exchange. Serum concentrations of TNF-alpha and IL-6 were significantly lower after plasma exchange than before plasma exchange. CONCLUSION: TNF-alpha and IL-6 may be important in the pathogenesis of the clinical symptoms that differentiate fulminant hepatitis from the severe form of acute hepatitis, and plasma exchange removes these inflammatory mediators from the circulation of patients with severe liver disease.

Adolescent↗
PubMed1998

Protective effect of passive immunization against TNF-alpha in mice infected with Sendai virus.

TNF-alpha has been reported to be induced in mice infected with Sendai virus. We evaluated the role of TNF-alpha in the virus infection. TNF-alpha was induced locally in proportion to virus titers in the lung. The activity was correlated with suppression of body weight gain. Passive immunization against TNF-alpha improved body weight gain and ameliorated pneumonic lesions in infected mice, and prevented them from lethal infection, but lung virus induced emaciation, pneumonic lesions and death were mediated by TNF-alpha.

Animals↗
PubMed1998

NMR with 13C, 15N-doubly-labeled DNA: the Antennapedia homeodomain complex with a 14-mer DNA duplex.

Nearly complete 1H, 13C and 15N NMR assignments have been obtained for a doubly labeled 14-base pair DNA duplex in solution both in the free state and complexed with the uniformly 15N-labeled Antennapedia homeodomain. The DNA was either fully 13C, 15N-labeled or contained uniformly 13C, 15N-labeled nucleotides only at those positions which form the protein-DNA interface in the previously determined NMR solution structure of the Antennapedia homeodomain-DNA complex. The resonance assignments were obtained in three steps: (i) identification of the deoxyribose spin systems via scalar couplings using 2D and 3D HCCH-COSY and soft-relayed HCCH-COSY; (ii) sequential assignment of the nucleotides via 1H-1H NOEs observed in 3D 13C-resolved NOESY; and (iii) assignment of the imino and amino groups via 1H-1H NOEs and 15N-1H correlation spectroscopy. The assignment of the duplex in the 17 kDa protein-DNA complex was greatly facilitated by the fact that 1H signals of the protein were filtered out in 13C-resolved spectroscopy and by the excellent carbon chemical shift dispersion of the DNA duplex. Comparison of corresponding 13C chemical shifts of the free and the protein-bound DNA indicates conformational changes in the DNA upon complex formation.

Antennapedia Homeodomain Protein↗
PubMed1997

Effect of phospholipids on adsorption and penetration of human T-cell leukemia virus type I.

We have studied the ability of some phospholipids (PLs) and phospholipases (PLases) to interfere with infection of human T-cell leukemia virus type I (HTLV-I). Plating of pseudotype of vesicular stomatitis virus (VSV) bearing envelope antigens of HTLV-I, VSV(HTLV-I), was markedly inhibited by treatment of the cells with cardiolipin (CL) after, but not before, infection. Treatment of the cells with CL after infection also inhibited the plating of VSV pseudotype of bovine leukemia virus (BLV), but scarcely affected VSV infection. Furthermore, the plating of VSV(HTLV-I) was markedly enhanced by treatment with PLCase after infection. Treatment with PLCase, however, did not affect the plating of VSV. These results were also confirmed by polymerase chain reaction (PCR): Formation of proviral DNA was inhibited when indicator cells were treated with CL after cell-free infection of HTLV-I, but not before, and enhanced when indicator cells were treated with PLCase after HTLV-I infection. These findings suggested that PLs might play a role at the early stage of HTLV-I infection.

Adsorption↗
PubMed1997

Anisotropic molecular rotational diffusion in 15N spin relaxation studies of protein mobility.

The backbone dynamics of the uniformly 15N-labeled N-terminal 63-residue DNA-binding domain of the 434 repressor has been characterized by measurements of the individual 15N longitudinal relaxation times, T1, transverse relaxation times, T2, and heteronuclear 15N[1H]-NOEs at 1H resonance frequencies of 400 and 750 MHz. The dependence of an apparent spherical top correlation time, tauR, on the orientation of the N-H bond vector with respect to the principal axes of the global diffusion tensor of the protein was used to establish the fact that the degree of anisotropy of the global molecular tumbling amounts to 1.2, which is in good agreement with the values obtained from model calculations of the hydrodynamic properties. A model-free analysis showed that even this small anisotropy leads to the implication of artifactual slow internal motions for at least two residues when the assumption of isotropic global motion is used. Additional residues may actually undergo internal motions on the same time scale as the global rotational diffusion, in which case the model-free approach would, however, be inappropriate for quantifying the correlation times and order parameters. Overall, the experiments with 434(1-63) demonstrate that the assumption of isotropic rotational reorientation may result in artifacts of model-free interpretations of spin relaxation data even for proteins with small deviations from spherical shape.

Binding Sites↗
PubMed1997

Usefulness of novel imaging modalities in diagnosis of focal nodular hyperplasia of the liver.

A 17-year-old woman was admitted because of a liver tumor found incidentally by ultrasonography. Liver function was normal and there were no markers of hepatitis viruses or malignancy. Abdominal ultrasonography, computed tomography (CT), and magnetic resonance imaging revealed a mass (2 cm in diameter) in the lateral segment of the left lobe of the liver. The lesion was not detected by hepatic arteriography. However, dynamic CT with fast scanning and dynamic CO2-enhanced ultrasonography demonstrated initial central enhancement of the mass followed by centrifugal spread of enhancement to the periphery. Color Doppler flow imaging detected a central color spot, shown to be an artery by a pulsed Doppler spectrum analysis. Fine-needle biopsy confirmed a diagnosis of focal nodular hyperplasia. Dynamic CT with fast scanning, dynamic CO2-enhanced ultrasonography, and color Doppler flow imaging were useful in detecting the vascular pattern specific to focal nodular hyperplasia. Investigation of further cases with these novel imaging modalities should help to establish a comprehensive diagnostic procedure and thus avoid unnecessary surgery for focal nodular hyperplasia, which is a completely benign lesion.

Adolescent↗