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Biomedical subjects

K Kobayashi

Publications and source records attributed to K Kobayashi.

At least 73 records · Page 4Linked to original sources
PubMed2005

Comparative morphological study on the tongue and lingual papillae of horses (Perissodactyla) and selected ruminantia (Artiodactyla).

A common characteristic of horses, Rocky Mountain goats, and cattle is that they all have a well developed lingual prominence on the dorsal surface of the posterior area of the tongue. Foliate papillae were found in the horse studied but not in the goat or in cattle. The horse filiform papillae had a long and slender external form with a thin and slender CTC, while in the goat and cattle the external form consisted of a large thick main process and the CTC consisted of a bundle of numerous rod-shaped protrusions. The special papilla found on the lingual prominence resembled larger filiform-like papillae in the horses; however, in the goat and cattle it was a very thick and large tongue like papillae. The horses had two large vallate papillae, while the goat and cattle had 15 or more vallate papillae at the posterior area of the lingual prominence. This suggests that the fine structure of horse tongues may display a more primitive pattern than that present in goats and cattle.

Animals↗
PubMed2005

Fukutin and alpha-dystroglycanopathies.

Fukuyama-type congenital muscular dystrophy (FCMD), Walker-Warburg syndrome (WWS), and muscle-eye-brain (MEB) disease are clinically similar autosomal recessive disorders characterized by congenital muscular dystrophy, lissencephaly, and eye anomalies. We identified the gene for FCMD and MEB, which encodes the fukutin protein and the protein O-linked mannose beta1, 2-N-acetylglucosaminyltransferase (POMGnT1), respectively. Recent studies have revealed that posttranslational modification of alpha-dystroglycan is associated with these congenital muscular dystrophies with brain malformations. All are characterized by hypoglycosylated alpha-dystroglycan. Fukutin's function and the relation with other alpha-dystroglycanopathies are discussed.

Animals↗
PubMed2004

MCG measurement in the environment of active magnetic shield.

MCG (Magnetocardiography) measurement by a SQUID gradiometer was attempted with only active magnetic shielding (active shielding). A three-axis-canceling-coil active shielding system, where three 16-10-16 turns-coil sets were put in the orthogonal directions, produces a homogeneous magnetic field in a considerable volume surrounding the center. Fluxgate sensors were used as the reference sensors of the system. The system can reduce environmental magnetic noise at low frequencies of less than a few Hz, at 50 Hz and at 150 Hz. Reducing such disturbances stabilizes biomagnetic measurement conditions for SQUIDs in the absence of magnetically shielded rooms (MSR). After filtering and averaging the measured MCG data by a first-order SQUID gradiometer with only the active shielding during the daytime, the QRS complex and T wave was clearly presented.

Electricity↗
PubMed2004

Magnetic noise rejection in the MCG using independent component analysis.

In magnetocardiogram (MCG) measurements, the magnetic noise from any magnetic wire, used to suture the sternum after heart surgery, becomes a problem. As one method of noise rejection, independent component analysis is seen here to be effective. In this study, MCG measurements were carried out under conditions where a wire was attached to a normal subject, also where no wire was attached. Signal processing by independent component analysis was carried out in order to reduce the effect of magnetic noise from the wire. From the comparison of the waveforms after this signal processing and the waveforms where the wire was not attached, it was apparent that the magnetic noise from the wire was reduced. Thus, we have shown that independent component analysis is effective for the reduction of magnetic noise from a magnetic wire, in MCG measurements.

Electricity↗
PubMed2004

Active magnetic compensation composed of shielding panels.

Magnetically shielded rooms (MSRs) with materials of high permeability and active shield systems have been used to shield magnetic noise for biomagnetic measurements up to now. However, these techniques have various disadvantages. Therefore, we have developed a new shielding system composed of shielding panels using an active compensation technique. In this study, we evaluated the shielding performance of several unit panels attached together. Numerical and experimental approaches indicated that the shielding factor of a cubic model composed of 24 panels was 17 for uniform fields, and 7 for disturbances due to car movement. Furthermore, the compensation space is larger than that of an ordinary active system using large coils rather than panels. Moreover, the new active compensation system has the important advantage that panels of any shape can be assembled for occasional use because the unit panels are small and light.

Electromagnetic Fields↗
PubMed2004

3-D magnetic measurement of neuromagnetic response of somatosensory area to different repetition frequencies.

3-D magnetic measurements of the bilateral somatosensory evoked fields (SEFs) by electric stimulus to the right thumb for four normal subjects were carried out, using a three-dimensional (3-D) second-order gradiometer connected to 39-channel SQUIDs, which can detect magnetic field components perpendicular to the scalp (Br) and tangential to the scalp (Btheta, Bphi) simultaneously. To discuss the relationship between the phase lag and stimulus repetition frequency (SRF), the delay times of a component synchronous with the SRFs (1.99 to 27.02 Hz) were calculated by the convolution of the reference signal and the SEF wave (BPF: 15-40 Hz). The phase lag characteristic to the SRF in the contralateral hemisphere to the stimulus was linear in the ranges below 8 Hz and above 8 Hz in all magnetic components. The phase lag characteristic of the ipsilateral hemisphere to the stimulus was linear in only below-8 Hz in all components. It was tested for significance of the linear regression slope (beta not = 0, P<0.05).

Electric Stimulation↗
PubMed2004

3-D magnetic measurement of exercise-induced MCG.

We carried out a three-dimensional (3-D) vector measurement of exercise-induced magnetocardiograms (MCGs) for normal subjects with a wooden and brass-based bicycle ergometer. MCGs were measured by a 3-D second-order gradiometer connected to 39-channel SQUIDs, which can detect magnetic field components perpendicular to the chest wall (Bz) and tangential to the chest wall (Bx, By) simultaneously. Time-frequency analysis was applied to rest times and exercise-induced MCG data. It was shown that the power spectrum of the ST segment was different between the rest times and exercise-induced MCG. Principal component analysis (PCA) was also applied to the result of time-frequency analysis and the time course of frequency for the ST segment was evaluated quantitatively. It found that dominant frequency of the ST segment in the rest time was ranged 5.5 to 6.5 Hz in all components. And it was clearly shown that the peak frequency of the exercise-induced MCG was shifted to 10.5 Hz compared to that of rest MCG.

Electromagnetic Fields↗
PubMed2004

Nature of the well screened state in hard X-ray Mn 2p core-level photoemission measurements of La1-xSrxMnO3 films.

Using hard x-ray (HX; hnu=5.95 keV) synchrotron photoemission spectroscopy (PES), we study the intrinsic electronic structure of La(1-x)Sr(x)MnO(3) (LSMO) thin films. Comparison of Mn 2p core-levels with soft x-ray (SX; hnu approximately 1000 eV) PES shows a clear additional well-screened feature only in HX PES. Takeoff-angle dependent data indicate its bulk (> or =20 A) character. The doping and temperature dependence track the ferromagnetism and metallicity of the LSMO series. Cluster model calculations including charge transfer from doping-induced states show good agreement, confirming this picture of bulk properties reflected in Mn 2p core-levels using HX PES.

Journal Article↗
PubMed2004

GP2/THP gene family of self-binding, GPI-anchored proteins forms a cluster at chromosome 7F1 region in mouse genome.

We investigated the genomic organization of pancreatic zymogen granule membrane-associated protein GP2, a GPI-anchored protein exhibiting self-aggregation at acidic pH, in order to construct a gene-knockout mouse. Cloning and analysis of lambda clones encoding GP2 from 129 Svj mouse genomic DNA libraries showed that the GP2 gene spans about 16.8 kb and includes 11 exons. Identifiable functional domains including a signal sequence, an EGF-like motif, a putative condensing ZP domain, a GPI-anchor attachment site, and a transmembrane sequence for GPI anchoring are encoded in separate exons. Using FISH, the GP2 gene was mapped to mouse chromosome 7F1 near the gene for THP, a GP2 homolog expressed in the cells of thick ascending loop of Henle (TALH) in the kidney. Further analysis of the mouse genome revealed that the THP and GP2 genes are adjacent to one another and are separated by only 3.5 kb in the 7F1 locus. Additionally, the overall structure of the THP gene, 16.2kb with 11 exons, was strikingly similar to that of GP2. This finding suggests that the GP2 and THP genes were generated by gene duplication and evolved separately to acquire regulatory elements leading to tissue-specific expression. Comparative analysis revealed that the 5' flanking region of the THP gene is similar to the first intron of NKCC2, a TALH cell-specific ion-transporter gene. The promoter region of the GP2 gene shares cis-elements found in other pancreas-specific genes. Using this genetic information, a GP2 null mutation was successfully introduced into an ES cell line, and an animal model was established without disruption of THP expression.

Animals↗
PubMed2004

Direct observation of ferromagnetic spin polarization in gold nanoparticles.

We report the first direct observation of ferromagnetic spin polarization of Au nanoparticles with a mean diameter of 1.9 nm using x-ray magnetic circular dichroism (XMCD). Owing to the element selectivity of XMCD, only the gold magnetization is explored. Magnetization of gold atoms as estimated by XMCD shows a good agreement with results obtained by conventional magnetometry. This evidences intrinsic spin polarization in nanosized gold.

Journal Article↗
PubMed2004

Evidence for an oscillatory signature in atmospheric neutrino oscillations.

Muon neutrino disappearance probability as a function of neutrino flight length L over neutrino energy E was studied. A dip in the L/E distribution was observed in the data, as predicted from the sinusoidal flavor transition probability of neutrino oscillation. The observed L/E distribution constrained nu(micro)<-->nu(tau) neutrino oscillation parameters; 1.9x10(-3) 0.90 at 90% confidence level.

Journal Article↗
PubMed2004

Predicting gene regulation by sigma factors in Bacillus subtilis from genome-wide data.

MOTIVATION: Sigma factors regulate the expression of genes in Bacillus subtilis at the transcriptional level. We assess the accuracy of a fold-change analysis, Bayesian networks, dynamic models and supervised learning based on coregulation in predicting gene regulation by sigma factors from gene expression data. To improve the prediction accuracy, we combine sequence information with expression data by adding their log-likelihood scores and by using a logistic regression model. We use the resulting score function to discover currently unknown gene regulations by sigma factors. RESULTS: The coregulation-based supervised learning method gave the most accurate prediction of sigma factors from expression data. We found that the logistic regression model effectively combines expression data with sequence information. In a genome-wide search, highly significant logistic regression scores were found for several genes whose transcriptional regulation is currently unknown. We provide the corresponding RNA polymerase binding sites to enable a straightforward experimental verification of these predictions.

Algorithms↗
PubMed2004

Search for electron neutrino appearance in a 250 km long-baseline experiment.

We present a search for electron neutrino appearance from accelerator-produced muon neutrinos in the K2K long-baseline neutrino experiment. One candidate event is found in the data corresponding to an exposure of 4.8 x 10(19) protons on target. The expected background in the absence of neutrino oscillations is estimated to be 2.4+/-0.6 events and is dominated by misidentification of events from neutral current pi(0) production. We exclude the nu(micro) to nu(e) oscillations at 90% C.L. for the effective mixing angle in the 2-flavor approximation of sin((2)2theta(microe)( approximately 1/2sin((2)2theta(13))>0.15 at Deltam(2)(microe)=2.8 x 10(-3) eV(2), the best-fit value of the nu(micro) disappearance analysis in K2K. The most stringent limit of sin((2)2theta(microe)<0.09 is obtained at Deltam(2)(microe)=6 x 10(-3) eV(2).

Journal Article↗
PubMed2004

Limits on the neutrino magnetic moment using 1496 days of Super-Kamiokande-I solar neutrino data.

A search for a nonzero neutrino magnetic moment has been conducted using 1496 live days of solar neutrino data from Super-Kamiokande-I. Specifically, we searched for distortions to the energy spectrum of recoil electrons arising from magnetic scattering due to a nonzero neutrino magnetic moment. In the absence of a clear signal, we found micro(nu)</=(3.6x10(-10))micro(B) at 90% C.L. by fitting to the Super-Kamiokande day-night spectra. The fitting took into account the effect of neutrino oscillation on the shapes of energy spectra. With additional information from other solar neutrino and KamLAND experiments constraining the oscillation region, a limit of micro(nu)</=(1.1x10(-10))micro(B) at 90% C.L. was obtained.

Journal Article↗
PubMed2004

Neuronal protection from glucose deprivation via modulation of glucose transport and inhibition of apoptosis: a role for the insulin-like growth factor system.

Glucose is the brain's major energy source; therefore, loss of neuronal cells is a potential consequence of hypoglycaemia. Since apoptosis is a major mechanism of neuronal loss following a range of insults, we explored potent anti-apoptotic systems (IGF-I and bcl-2) as means of enhancing neuronal survival in the face of glucose deprivation. Human neuroblastoma cells (SH-SY5Y, SHEP and SHEP-bcl-2) were exposed to low glucose as a model of glucopenia-induced neuronal damage. Administration of IGF-I and/or over-expression of the survival gene bcl-2 were exploited to attempt to limit neuronal loss. Neuronal survival mechanisms and interactions between these systems were investigated. Low glucose (0.25-2.5 mM) adversely affected cell growth and survival; however, IGF-I ameliorated these outcomes. Over-expression of bcl-2 blunted low glucose-induced apoptosis and up-regulated IGF-I receptor, with the effect of IGF-I addition being negligible on apoptosis, while significantly enhancing mitochondrial activity. In SH-SY5Y cells, IGF-I significantly changed >two-fold mRNA levels of the apoptosis-related genes gadd45, fas, iNOS, NFkB, TRAIL, without further affecting bcl-2 expression. In low glucose, IGF-I acutely enhanced glucose transport and translocation of GLUT1 protein to the cell membrane. GLUT1 mRNA expression was up-regulated by both IGF-I and bcl-2. The potent anti-apoptotic systems IGF-I and bcl-2 are both thus able to enhance cell survival in a glucose-deprived human neuronal model. Although we clearly show evidence of positive cross-talk via bcl-2 modulation of IGF-I receptor, IGF-I also has enhancing effects on mitochondrial function outside the bcl-2 pathway. The common effect of both systems on enhancement of GLUT-1 expression suggests that this is a key mechanism for enhanced survival. These studies also point to the potential use of IGF-I therapy in prevention or amelioration of hypoglycaemic brain injury.

Analysis of Variance↗
PubMed2004

Antiapoptotic effects of leptin in human neuroblastoma cells.

Many factors regulate nervous system development, including complex cross-talk between local neuroendocrine systems. The adipocyte-secreted hormone leptin, mainly known for its key roles in nutrition and reproductive balance, may also be involved in neuroanatomical organization, myelination processes, and neuronal/glia maturation. SK-N-SH-SY5Y neuroblastoma cells were employed as an in vitro model of human neuronal cells to determine whether leptin exerts neuroprotective activities. We show that SH-SY5Y cells express leptin, the long and short isoforms of the leptin receptor (ObRl, ObRs). In SH-SY5Y cells, leptin induced signal transducer and activator of transcription (STAT)-3 phosphorylation and suppressor of cytokine signaling-3 mRNA expression. Leptin dose-dependently increased cell number (up to 200% at 1 microm by 48 h, P < 0.01), and at 24-48 h, leptin at 100 nm increased SH-SY5Y cell number by 30-50%, respectively. SH-SY5Y cell viability was reduced in serum-free conditions at 24 h, and addition of leptin at 100 nm significantly reduced apoptosis by approximately 20% (P < 0.001). Leptin's antiapoptotic activity required Janus kinase/STAT, MAPK, and phosphatidylinositol-3-kinase activation because the antiapoptotic effects of leptin were abolished, and caspase-3 immunoreactivity increased in the presence of the specific blockers AG490, U0126, or LY294002. Gene array demonstrated that leptin inhibits apoptosis via potent down-regulation of caspase-10 and TNF-related apoptosis-inducing ligand. Our data thus demonstrate, for the first time, that leptin stimulates, in a time- and dose-dependent manner, neuroblastoma cell proliferation and that the underlying mechanisms involve suppression of apoptosis via the Janus kinase-STAT, phosphatidylinositol-3 kinase, and MAPK pathways that culminate altogether in the down-regulation of the apoptotic factors caspase-10 and TNF-related apoptosis-inducing ligand.

Apoptosis↗
PubMed2004

Polo-like kinase 1 overexpression is an early event in the progression of papillary carcinoma.

Polo-like kinase 1 (PLK1) is one of the serine threonine kinases that contributes to cell mitosis and is regarded as a marker of cellular proliferation. However, its protein expression in human carcinoma has not been studied in depth. We investigated PLK1 expression in various thyroid neoplasms in order to elucidate its physiological significance in thyroid carcinoma. Normal follicular cells only occasionally expressed PLK1. In follicular tumours and anaplastic carcinoma, PLK1 overexpression was not a common event and only 5.9% of follicular adenoma, 7.1% of follicular carcinoma, and 11.8% of anaplastic carcinoma overexpressed this protein. However, 43.7% of papillary carcinoma overexpressed PLK1. Polo-like kinase 1 overexpression was more frequently observed in smaller papillary carcinoma lesions, and 62.5% of microcarcinoma (ranging from 4 mm to 1.0 cm) and even 66.7% of incidental carcinoma (less than 4 mm) overexpressed it, whereas this phenomenon could only be seen in 20.0% of lesions larger than 4.0 cm. Furthermore, PLK1 overexpression was not related to cell-proliferating activity evaluated by Ki-67 labelling index, but it was inversely linked to UICC stage, extrathyroidal invasion, and the presence of poorly differentiated lesion as proposed by Sakamoto et al. These findings strongly suggest that, unlike other carcinomas previously studied, PLK1 does not act as a cell cycle regulator but plays a constitutive role in papillary carcinoma especially in the early phase, and may contribute to the malignant transformation of this carcinoma.

Blotting, Western↗