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Biomedical subjects

K Kitamura

Publications and source records attributed to K Kitamura.

At least 19 recordsLinked to original sources
PubMed2006

Intracranial angiosarcoma arising from a schwannoma.

Angiosarcomas rarely arise from schwannomas, but we describe here a case of angiosarcoma that arose from a remnant of a benign vestibular schwannoma that had been removed 10 years earlier. The patient was a 66-year-old man with no sign of neurofibromatosis. Although we attempted surgical resection, we could not totally remove the tumour. The patient died nine months after diagnosis, primarily as result of an abscess in the cerebellum and base of the skull. The histological diagnosis was confirmed by the immunohistochemical findings of positivity for CD34 antigen and S-100 protein in the resected tumour.A review of the literature revealed four other cases of angiosarcoma with schwannoma, all of which arose from an extracranial nerve. The present case is the first report of an angiosarcoma with schwannoma arising from an intracranial locus.

Aged↗
PubMed2006

Inhibition of prostasin-induced ENaC activities by PN-1 and regulation of PN-1 expression by TGF-beta1 and aldosterone.

Prostasin has been shown to regulate sodium handling in the kidney. Recently, a serine protease inhibitor, protease nexin-1 (PN-1), was identified as an endogenous inhibitor for prostasin. Therefore, we hypothesized that PN-1 may regulate sodium reabsorption by reducing prostasin activity, and that expression of PN-1 was regulated by transforming growth factor-beta1 (TGF-beta1) or aldosterone, like prostasin. cRNAs for epithelial sodium channel (ENaC), prostasin, and PN-1 were expressed in Xenopus oocytes, and the amiloride-sensitive sodium currents (I(Na)) were measured. The effect of TGF-beta1 and aldosterone on the mRNA and protein abundance of PN-1 and ENaC was detected by real-time polymerase chain reaction and immunoblotting in M-1 cells. Expression of PN-1 substantially decreased prostasin-induced I(Na) by approximately 68% in oocytes. Treatment of M-1 cells with 20 ng/ml TGF-beta1 significantly increased protein expression of PN-1 by 3.8+/-0.5-fold, whereas administration of 10(-6) M aldosterone markedly decreased protein expression of PN-1 to 53.7+/-6.7%. Basolateral, but not apical, application of TGF-beta1 significantly reduced I(eq). To elucidate the involvement of PN-1 in basal ENaC activity, we silenced the expression of PN-1 by using short-interfering RNA. This increased I(eq) by 1.6+/-0.1-fold. Our study indicates that PN-1 could have a natriuretic role by inhibiting prostasin activity and suggests the possibility that aldosterone and TGF-beta reciprocally regulate the expression of PN-1 in renal epithelial cells contributing to salt retention or natriuresis, respectively by an additional mechanism. PN-1 could represent a new factor that contributes to regulation of ENaC activity in the kidney.

Aldosterone↗
PubMed2006

Plasma adrenomedullin level and development of hypertension.

The hypotensive peptide adrenomedullin (AM) is assumed to act as a factor inhibitory on elevation of blood pressure and on progression of the hypertensive organ damage, and plasma AM levels are elevated in patients with hypertension. The aim of the present study is to explore whether or not a rise in plasma AM levels precedes the development of hypertension. Normotensive local residents without apparent cardiovascular or renal disease (n = 177) were divided into low and high AM groups based on the median concentration of AM in plasma (11.9 fmol/ml), and followed up for 3 years for development of hypertension. The incidence of hypertension was higher in the residents with high AM than low AM levels (27.8 vs 11.5%, P < 0.01), whereas a similar analysis of plasma levels of atrial or brain natriuretic peptides revealed no such difference. The plasma AM level was found to be a significant parameter for the development of hypertension in a univariate analysis (P < 0.01), but not in a multivariate analysis. Meanwhile, the plasma AM level was significantly (P < 0.01) correlated with age and body mass index (BMI), two variables independently significant for the development of hypertension. The present findings suggest that an elevation of the plasma AM level associated with aging and increased BMI precedes the development of hypertension in the normotensive subjects.

Adrenomedullin↗
PubMed2006

Optical-damage-free guided second-harmonic generation in 1% MgO-doped stoichiometric lithium tantalate.

Room-temperature cw second-harmonic generation from telecom wavelengths, with 30% W(-1) cm(-2) efficiency and second-harmonic power levels up to 41 mW, was achieved in buried waveguides fabricated by reverse-proton exchange in 1% MgO-doped stoichiometric lithium tantalate without any evidence of optical damage. The technology proves suitable for the realization of efficient nonlinear frequency converters and all-optical devices.

Journal Article↗
PubMed2006

Roles of CLCA and CFTR in electrolyte re-absorption from rat saliva.

A molecular basis for Cl- re-absorption has not been well-characterized in salivary ductal cells. Previously, we found strong expression of a rat homologue proposed to be Ca2+-dependent Cl- channels (rCLCA) in the intralobular ducts of the rat submandibular gland. To address the question as to whether rCLCA and cystic fibrosis transmembrane conductance regulator (CFTR) are involved in Cl- re-absorption, we evaluated the electrolyte content of saliva from glands pre-treated with a small interfering RNA (siRNA). Retrograde injection into a given submandibular duct of an siRNA designed to knock down either rCLCA or CFTR reduced the expression of each of the proteins. rCLCA and CFTR siRNAs significantly increased Cl- concentration in the final saliva during pilocarpine stimulation. These results represent the first in vivo evidence for a physiological significance of rCLCA, along with CFTR, in transepithelial Cl- transport in the ductal system of the rat submandibular gland.

Absorption↗
PubMed2005

Oxidative stress by glutathione depletion induces osteonecrosis in rats.

OBJECTIVE: We recently implicated in vivo oxidative stress in the development of osteonecrosis in a steroid-induced osteonecrosis model in the domestic rabbit. In the present experiment we devised a new non-traumatic model using the rat to investigate the relationship between oxidative stress and the development of osteonecrosis. METHODS: Seven 24-week-old male Wistar rats were subcutaneously injected with the pro-oxidant buthionine sulphoximine (BSO) 500 mg/kg for 14 consecutive days (group B) and eight rats received injections of vehicle (physiological saline; group N). The rats in both groups were killed after 14 days, and their bilateral femurs were examined histopathologically. Blood levels of reduced glutathione (GSH), total cholesterol (T-cho) and triglycerides (TG) were also determined. RESULTS: GSH was significantly decreased in group B compared with group N (P < 0.01). No significant differences were found in T-cho or TG. Osteonecrosis was not detected in any animal in group N in contrast to five of seven animals in group B (P < 0.05). CONCLUSION: BSO is an inducer of oxidative stress, in particular interfering with the synthesis of GSH in vivo. In the present study, GSH levels were markedly reduced by BSO, whereas neither T-cho nor TG was significantly changed. The high rate of osteonecrosis noted in group B suggests that oxidative stress alone may be sufficient to promote the development of osteonecrosis at certain sites.

Animals↗
PubMed2005

A clinical, genetic, and neuropathologic study in a family with 16q-linked ADCA type III.

Presented is the new kindred with autosomal dominant cerebellar ataxia linked to chromosome 16q22.1 (16q-ADCA type III) associated with progressive hearing loss. By haplotype analysis, the critical interval was slightly narrowed to three megabase regions between GATA01 and D16S3095. Neuropathologic study of 16q-ADCA type III demonstrated characteristic shrinkage of Purkinje cell bodies surrounded by synaptophysin-immunoreactive amorphous material containing calbindin- and ubiquitin-positive granules.

Adolescent↗
PubMed2005

Unconstrained detection of respiration rhythm and pulse rate with one under-pillow sensor during sleep.

A completely non-invasive and unconstrained method is proposed to detect respiration rhythm and pulse rate during sleep. By employing wavelet transformation (WT), waveforms corresponding to the respiration rhythm and pulse rate can be extracted from a pulsatile pressure signal acquired by a pressure sensor under a pillow. The respiration rhythm was obtained by an upward zero-crossing point detection algorithm from the respiration-related waveform reconstructed from the WT 2(6) scale approximation, and the pulse rate was estimated by a peak point detection algorithm from the pulse-related waveform reconstructed from the WT 2(4) and 2(5) scale details. The finger photo-electric plethysmogram (FPP) and nasal thermistor signals were recorded simultaneously as reference signals. The reference pulse rate and respiration rhythm were detected with the peak and upward zero-crossing point detection algorithm. This method was verified using about 24 h of data collected from 13 healthy subjects. The results showed that, compared with the reference data, the average error rates were 3.03% false negative and 1.47% false positive for pulse rate detection in the extracted pulse waveform. Similarly, 4.58% false negative and 3.07% false positive were obtained for respiration rhythm detection in the extracted respiration waveform. This study suggests that the proposed method is suitable, in sleep monitoring, for the diagnosis of sleep apnoea or sudden death syndrome.

Adult↗
PubMed2005

Prime-boost vaccination with plasmid DNA and a chimeric adenovirus type 5 vector with type 35 fiber induces protective immunity against HIV.

Immunization involving a DNA vaccine prime followed by an adenovirus type 5 (Ad5) boost elicited a protective immune response against SHIV challenge in monkeys. However, the hepatocellular tropism of Ad5 limits the safety of this viral vector. This study examines the safety and immunogenicity of a replication-defective chimeric Ad5 vector with the Ad35 fiber (Ad5/35) in BALB/c mice and rhesus monkeys. This novel Ad5/35 vector showed minimal hepatotoxicity after intramuscular administration with the novel Ad5/35 vector. In addition, an Ad5/35 vector expressing HIV Env gp160 protein (Ad5/35-HIV) generated strong HIV-specific immune responses in both animal models. Priming with a DNA vaccine followed by Ad5/35-HIV boosting yielded protection against a gp160-expressing vaccinia virus challenge in BALB/c mice. The Ad5/35-HIV vector was significantly less susceptible to the pre-existing Ad5 immunity than a comparable Ad5 vector. These findings indicate that an Ad5/35 vector-based HIV vaccine may be of considerable value for clinical use.

AIDS Vaccines↗
PubMed2005

Angiotensin II stimulates cardiac adrenomedullin production and causes accumulation of mature adrenomedullin independently of hemodynamic stress in vivo.

Adrenomedullin is a potent hypotensive peptide that may act on myocytes to inhibit hypertrophy and on fibroblasts to inhibit growth in vitro induced by mechanical stretching and angiotensin II. Adrenomedullin is processed from the inactive intermediate adrenomedullin precursor with a glycine extension, which is subsequently converted to biologically active mature adrenomedullin by enzymatic amidation. Total adrenomedullin is the sum of intermediate and mature adrenomedullin. We examined the effect of a subpressor dose of angiotensin II on the production of left ventricular adrenomedullin and on protein levels of mature adrenomedullin in the left ventricle in vivo. We also investigated whether the effect is mediated by the angiotensin II type 1 receptor. Concentrations of total and mature adrenomedullin in the left ventricle and mature adrenomedullin-to-intermediate adrenomedullin ratio were significantly increased by angiotensin II infusion, regardless of pressure overload. Total and mature adrenomedullin concentrations significantly correlated with the weight of the left ventricle. Furthermore, increased adrenomedullin gene expression and protein levels were completely suppressed by a subdepressor dose of angiotensin II type 1 receptor blocker. In conclusion, angiotensin II stimulates the production of cardiac adrenomedullin and accumulates mature adrenomedullin in the left ventricle independently of hemodynamic stress. These processes are partially regulated through the angiotensin II type 1 receptor in vivo.

Adrenomedullin↗
PubMed2005

S-carboxymethylcysteine normalises airway responsiveness in sensitised and challenged mice.

S-carboxymethylcysteine (S-CMC) has been used as a mucoregulator in respiratory diseases. However, the mechanism of action of S-CMC on allergic airway inflammation has not yet been defined. In the present study, BALB/c mice were initially sensitised and challenged to ovalbumin (OVA) and, weeks later, re-challenged with OVA (secondary challenge). S-CMC (5-100 mg.kg-1) was administered from 2 days before the secondary challenge through to the day of assay. Mice developed airway hyperresponsiveness (AHR) 6 h after the secondary challenge and increased numbers of neutrophils were present in the bronchoalveolar lavage (BAL) fluid. At 72 h after secondary challenge, mice again developed AHR, but the BAL fluid contained large numbers of eosinophils. S-CMC treatment was found to reduce AHR and neutrophilia at 6 h, as well as eosinophilia and AHR at 72 h. These effects appeared to be dose dependent. Goblet cell hyperplasia, observed at 72 h, was reduced by S-CMC. In BAL fluid, increased levels of interferon-gamma, interleukin (IL)-12 and IL-10 and decreased levels of IL-5 and IL-13 were detected. In conclusion, the data indicate that S-carboxymethylcysteine is effective in reducing airway hyperresponsiveness and airway inflammation at two distinct phases of the response to the secondary allergen challenge in sensitised mice.

Allergens↗
PubMed2004

High-power femtosecond fiber-feedback optical parametric oscillator based on periodically poled stoichiometric LiTaO3.

We demonstrate a synchronously pumped high-gain optical parametric oscillator with feedback through a fiber, using a passively mode-locked Yb:YAG thin-disk laser as a pump source. We obtain as much as 19-W average signal power at a wavelength of 1.45 microm in 840-fs pulses and 7.8 W of idler power at 3.57 microm. The repetition rate of the pulses is 56 MHz, and the transverse beam quality of the generated signal is M2 < 1.6.

Journal Article↗
PubMed2004

Evidence for recombination among isolates of Tobacco leaf curl Japan virus and Honeysuckle yellow vein mosaic virus.

Complete nucleotide sequences of Tobacco leaf curl Japan virus (TbLCJV) isolates from infected tomato ( Lycopersicon esculentum) plants in Nara (-[Jp2], 2764 nt; -[Jp3], 2761 nt), Kochi (-[Koc], 2760 nt) and Yamaguchi (-[Yam], 2758 nt) Prefectures, of Japan were determined. These sequences were compared with each other and the sequences of further begomoviruses from Japan. TbLCJV, TbLCJV-[Jp2], TbLCJV-[Jp3], TbLCJV-[Koc], TbLCJV-[Yam], Honeysuckle yellow vein mosaic virus (HYVMV), Eupatorium yellow vein virus (EpYVV), EpYVV-[MNS2], EpYVV-[SOJ3], EpYVV-[Yam] and EpYVV-[Tob] are monophyletic. The intergenic region (IR) of TbLCJV has highest nucleotide sequence identity with that of HYVMV (93%) whereas the rest of the genomic DNA had higher identity with that of TbLCJV-[Jp2] or -[Jp3] (91 approximately 100%) than with that of HYVMV. In conclusion, TbLCJV has a chimeric genome which may have arisen by recombination between TbLCV-[Jp2] or -[Jp3]-like and HYVMV-like ancestors. Similarly, TbLCJV-[Yam] DNA has a hybrid genome, with a major parent HYVMV and minor parent TbLCJV-[Koc].

DNA, Intergenic↗