Biomedical subjects

Koichi Ogawa

Publications and source records attributed to Koichi Ogawa.

At least 19 recordsLinked to original sources

PubMed2006

Site-directed mutations in Alanine 223 and Glycine 255 in the acceptor site of gamma-Cyclodextrin glucanotransferase from Alkalophilic Bacillus clarkii 7364 affect cyclodextrin production.

A cyclodextrin glucanotransferase (CGTase) from Bacillus clarkii 7364 converts starch into gamma-cyclodextrin (gamma-CD) with high specificity. Comparison of the deduced amino acid sequence of this CGTase with those of other typical CGTases revealed that several amino acids are deleted or substituted with others at several subsites. Of these amino acids, Ala223 at subsite +2 and Gly255 at subsite +3 in the acceptor site of the enzyme were replaced by several amino acids through site-directed mutagenesis. The replacement of Ala223 by lysine, arginine and histidine strongly enhanced the gamma-CD-forming activity in the neutral pH range. On the other hand, all mutants obtained on replacing Gly255 with the above amino acids showed significant decreases in the gamma-CD-forming activity. Taking into account both the kinetic parameters and pKa values of the side chains of the three basic amino acids, the protonation state of the amino groups in their side chains at subsite +2 seems to enhance the hydrogen bonding interaction between these basic amino acids and the glucose residues of linear oligosaccharides. The enhancement of the interaction may play an important role by helping the substrate reach subsite +1, hence increasing the gamma-CD-forming activity and kcat value.

Amino Acid Sequence↗

PubMed2006

Remodeling of connexin 43 in the diabetic rat heart.

In the Streptozotocin-induced diabetic rat heart, a decrease in the conductivity and suppression of electrical cell-to-cell coupling were observed. To clarify this mechanism, the present study was performed to investigate alterations of the gap junction connexin 43 (Cx43) using immunoblotting, immunohistochemistry, electron-microscopic analyses. An enhanced activation of PKCepsilon, an augmentation of PKCepsilon-mediated phosphorylation of Cx43, a decrease in the total amount of Cx43, a reduction in the area of immunoreactive particles for Cx43 at the intercalated disk, distribution of Cx43 to cell periphery or cytoplasm and the internalization approximately annular profiles of the gap junction were all characteristically recognized in the diabetic heart. Such abnormalities in the expression of Cx43 were alleviated by treatment with either lysosomal (NH(4)Cl, Leupeptin) or proteasomal inhibitor (ALLN). These results suggest that the PKCepsilon-mediated hyperphosphorylation of Cx43 makes Cx43 vulnerable to proteolytic degradation and that a decrease in the conductivity in the diabetic heart is also caused by a decrease in the number of gap junction channels due to an acceleration of the proteolytic degradation of Cx43. The remodeling of Cx43 induced by the activation of PKCepsilon may therefore contribute to the formation of the arrhythmogenic substrate in the diabetic heart. The cardioprotective effect of the remodeling of Cx43 by PKCepsilon is discussed.

Animals↗

PubMed2006

Development of a collimator blurring compensation method using fine angular sampling projection data in SPECT.

Due to the collimator aperture, spatial resolution of SPECT data varies with source-to-detector distance. Since the radius of detector rotation is bigger when scanning larger patients, spatial resolution is degraded in these cases. Emitted gamma rays travel not only along the central axis of the collimator hole but also off-axis due to the collimator aperture. However, an off-axis ray at one angle would be a central-axis ray at another angle; therefore, raw projection data at one angle can be thought of as an ensemble of central-axis rays collected from a small arc equal to the collimator aperture. Thus, fine angular sampling can compensate for collimator blurring. By using a sampling pitch of less than half the collimator aperture angle, compensation was performed by subtracting the weighted sum of the projection data from the raw projection data. Collimator geometry and detector rotation radius determined the weighting function. Cylindrical phantom with four different-sized rods and torso phantom for Tl-201 cardiac SPECT simulation were used for evaluation. Aperture angle of the collimator was 7 degrees. Projection sampling pitch was 2 degrees. In both phantom studies, the proposed method showed improvement in contrast and reduction of partial volume effect, thereby indicating that the proposed method can compensate adequately for image blurring caused by the collimator aperture.

Artifacts↗

PubMed2006

Three-dimensional characteristics of submandibular salivary gland of ageing rats: an HRSEM study.

The characteristics of the submandibular glands of ageing Wistar rats were studied using light and high-resolution scanning electron microscopy (HRSEM) methods. For light microscopy, the samples were fixed in Bouin solution and embedded in paraffin. Sections were stained with hematoxilin-eosin and Azo-Carmin. For conventional scanning electron microscopy, the tissues were fixed in modified Karnovsky solution, and treated with NaOH solution for 3-4 days. The O-D-O method was used for HRSEM. The samples were fixed in 2% osmium tetroxide, macerated in diluted osmium and dehydrated in an increasing series of ethanol. The samples were dried in a critical point dryer, coated with gold-palladium and examined in a Hitachi high-resolution scanning electron microscope, S-900. The results showed that submandibular glands with lobules are separated by connective tissue septum. The acinar formations and the ducts, revealing the serous and mucous cells were observed. After fracture in liquid nitrogen and treatment with NaOH solution to remove the cellular components, the original disposition of the collagen bundles fibers were revealed corresponding to the round, oval or irregular acinar and ductal structures. In the cytoplasm, organelles such as mitochondria, rough endoplasmic reticulum, Golgi apparatus and serous and mucous secretory granules were observed localized in the apical portion in three-dimensional HRSEM images. The serous secretory granules presented different sizes and shapes showing the modifications which occurred in the ageing rats. The striated duct cells revealed the presence of the secretory cells and mitochondria in parallel disposition. The mitochondrial cristae were noted in three-dimensional aspects. The lumen presented numerous cytoplasmic microprojections. The lumen of excretor ducts are covered by polygonal epithelial cells containing numerous microplicae.

Aging↗

PubMed2006

Quantitative assessment of tumour extraction from dermoscopy images and evaluation of computer-based extraction methods for an automatic melanoma diagnostic system.

The aims of this study were to provide a quantitative assessment of the tumour area extracted by dermatologists and to evaluate computer-based methods from dermoscopy images for refining a computer-based melanoma diagnostic system. Dermoscopic images of 188 Clark naevi, 56 Reed naevi and 75 melanomas were examined. Five dermatologists manually drew the border of each lesion with a tablet computer. The inter-observer variability was evaluated and the standard tumour area (STA) for each dermoscopy image was defined. Manual extractions by 10 non-medical individuals and by two computer-based methods were evaluated with STA-based assessment criteria: precision and recall. Our new computer-based method introduced the region-growing approach in order to yield results close to those obtained by dermatologists. The effectiveness of our extraction method with regard to diagnostic accuracy was evaluated. Two linear classifiers were built using the results of conventional and new computer-based tumour area extraction methods. The final diagnostic accuracy was evaluated by drawing the receiver operating curve (ROC) of each classifier, and the area under each ROC was evaluated. The standard deviations of the tumour area extracted by five dermatologists and 10 non-medical individuals were 8.9% and 10.7%, respectively. After assessment of the extraction results by dermatologists, the STA was defined as the area that was selected by more than two dermatologists. Dermatologists selected the melanoma area with statistically smaller divergence than that of Clark naevus or Reed naevus (P = 0.05). By contrast, non-medical individuals did not show this difference. Our new computer-based extraction algorithm showed superior performance (precision, 94.1%; recall, 95.3%) to the conventional thresholding method (precision, 99.5%; recall, 87.6%). These results indicate that our new algorithm extracted a tumour area close to that obtained by dermatologists and, in particular, the border part of the tumour was adequately extracted. With this refinement, the area under the ROC increased from 0.795 to 0.875 and the diagnostic accuracy showed an increase of approximately 20% in specificity when the sensitivity was 80%. It can be concluded that our computer-based tumour extraction algorithm extracted almost the same area as that obtained by dermatologists and provided improved computer-based diagnostic accuracy.

Algorithms↗

PubMed2006

Alterations of connexin 43 in the diabetic rat heart.

In the streptozotocin-induced diabetic rat heart, a decrease in the conductivity and suppression of electrical cell-to-cell coupling has been observed. To clarify this mechanism, the present study was performed to investigate the gap junction connexin 43 (Cx43) using immunohistochemistry, immunoblot, electron-microscopic analyses. Enhanced activation of PKCepsilon, augmentation of PKCepsilon-mediated phosphorylation of Cx43, a decrease in the total amount of Cx43, a reduction in the number of immunoreactive particles for Cx43 at the intercalated disk and internalization, annular profiles of the gap junction were all recognized in the diabetic heart. Such a deterioration in the expression of Cx43 was alleviated by treatment with either lysosomal (leupeptin) or proteasomal inhibitor (ALLN). These results suggest that the PKCepsilon-mediated hyperphosphorylation of Cx43 makes Cx43 vulnerable to proteolytic degradation, while a decrease in the conductivity in the diabetic heart is also caused by a decrease in the number of gap junction channels due to an acceleration of the proteolytic degradation of Cx43. The remodeling of Cx43 induced by the activation of PKC may therefore contribute to the formation of the arrhythmogenic substrate.

Animals↗

PubMed2006

Topographical relationship between the human lateral circumflex femral artery and saphenous nerve.

This study was performed to investigate causes of various types of topographical relationship between the lateral circumflex femoral artery (L) and the saphenous nerve (S). Femoral artery (F), deep femoral artery (P), L and S of 186 legs of 93 Japanese adult cadavers were submitted to anatomy. Further, the levels of origin of L in thigh were measured. L were classified into nine types by the origins of L and topographical relationship between L and S. The incidence of various types of L is different among researchers. Our findings proved that these differences were caused by the differences in evaluations of twig from ascending branch (AB) or descending branch (DB) of L. In cases of L originating from F, incidence of L positioned in front of S is significantly higher than L originating from P (p < 0.01). In cases of L originating from F, L positioned in front of S originates from F at the significantly more proximal level compared to L positioned posterior to S (p < 0.001). Furthermore, also in cases of L originating from P, L positioned in front of S originates from P at the significantly more proximal level compared to L positioned posterior to S (p < 0.001). It is supposed that the topographical relationship between L and S changes depending on the artery where L originates and the level of origin of L.

Adult↗

PubMed2005

Influence of photon scattering and attenuation on ROI analysis in brain perfusion single-photon emission tomographic imaging of normal subjects.

OBJECTIVE: The aim of this study was to evaluate the effect of scatter and attenuation correction in region of interest (ROI) analysis in brain perfusion single-photon emission tomography (SPECT) and to assess the influence of selecting the reference area on semi-quantification. METHODS: Ten normal subjects were enrolled and injected with 123I-iodoamphetamine to undergo simultaneous emission and transmission scanning for scatter and attenuation correction. We reconstructed three SPECT images from common projection data of each subject: with scatter correction and non-uniform attenuation correction, with scatter correction and uniform attenuation correction, and with uniform attenuation correction applied to data without scatter correction. A program for automated ROI drawing was used to set ROIs on various regions in brain images. Regional count ratios were compared in images with different correction procedures by using three different reference areas. RESULTS: The effect of the combination of scatter and attenuation correction was marked in the precentral, temporal, posterior, hippocampus and especially in the cerebellum. In contrast, it was not appreciable in the central and parietal areas. When using the cerebellar ROI as the reference, the count ratio varied widely depending on the correction procedures. On the other hand, the whole brain reference offered the least variation in the count ratio. CONCLUSIONS: The influence of photon scattering and attenuation was dependent on regions. Since the count in the cerebellar ROI is greatly affected by photon scattering and attenuation, nonuniform attenuation correction combined with scatter correction deserves consideration when using the cerebellar ROI as the reference.

Algorithms↗

PubMed2005

Immunological effects of partially hydrolyzed arabinoxylan from corn husk in mice.

The effect of oral administration of partially hydrolyzed water-soluble corn husk arabinoxylan (CHAX), the average molecular weight of which is about 53 kDa, on immunopotentiating activity was investigated in mice. Oral administration of CHAX to healthy mice significantly augmented the production of interleukin (IL)-2 and interferon (IFN)-gamma with a slight increase in IL-4 in mitogen-induced proliferation of spleen cells. Natural killer (NK) cell activity in spleen cells from mice, which were transplanted tumor and administrated CHAX, was augmented about 2-fold. In model mice of atopic dermatitis, the average ear thickness of mice administrated CHAX was induced by dinitrophenyl-fluorobenzene (DNFB) after injection of an anti-dinitrophenyl (DNP)-IgE monoclonal antibody was much smaller than that in control animals. These results suggest that CHAX has the ability to increase the level of immunopotentiating activity without causing over response of immunological reaction even if it is administrated orally to mice.

Animals↗

PubMed2004

Crystallization and preliminary X-ray study of gamma-type cyclodextrin glycosyltransferase from Bacillus clarkii.

A gamma-cyclodextrin glycosyltransferase (EC 2.4.1.19) from Bacillus clarkii was crystallized using the hanging-drop vapour-diffusion method at 293 K. X-ray diffraction data were collected to 2.2 A. The crystal belongs to space group R3, with unit-cell parameters a = b = 211.6, c = 52.7 A. The asymmetric unit contains one protein molecule, with a corresponding V(M) of 3.03 A(3) Da(-1) and a solvent content of 59.4%. Molecular replacement was successfully carried out using a homology model based on the three-dimensional structure of the CGTase from Thermonanaerobacterium thermosulfurigenes EM1 as a search model.

Bacillus↗

PubMed2004

Image distortion and correction in single photon emission CT.

The task of single photon emission CT (SPECT) is to visualize the physiological function of various organs with the help of radiopharmaceuticals. But the projection data used for image reconstruction are distorted by several factors, making the reconstruction of a quantitative SPECT image very difficult in most cases. These factors include the attenuation and scattering of gamma rays, collimator aperture, data acquisition method, movement of organs, and washout of radiopharmaceuticals. This review article classifies the causes of the distortion in SPECT images and describes correction methods.

Algorithms↗

PubMed2004

InsP3 receptor type 2 and oscillatory and monophasic Ca2+ transients in rat adrenal chromaffin cells.

Muscarinic receptor stimulation induced oscillatory and monophasic Ca(2+) transients in rat adrenal chromaffin cells in the absence of external Ca(2+). As this Ca(2+) mobilization may be mediated by InsP(3), we first explored types of InsP(3) receptors and their intracellular distribution in chromaffin cells. The InsP(3) receptor type 1 was not immunodetected in precipitates of adrenal medulla homogenates and in dissociated adrenal chromaffin cells, whereas an anti-type 3 mAb recognized a faint band with about 250 kDa, but no significant immunoreaction was visible in chromaffin cells. The anti-type 2 mAb strongly detected a band with about 220 kDa and the immunoreaction was observed perinuclearly and at the cell periphery. These results indicate that InsP(3) receptor type 2 is predominant in chromaffin cells. The oscillatory and monophasic Ca(2+) transients were reproduced in simulation based on a three-state kinetic model (shut, open, and inactivated states). Ca(2+) ions were found experimentally and theoretically to turn over rapidly between stores and the cytosol during stimulation. The results suggest that InsP(3) receptor type 2 is responsible for both oscillatory and monophasic Ca(2+) transients and that change in mode of Ca(2+) responses may be accounted for by the kinetic property of the type 2 receptor.

Animals↗

PubMed2004

A morphological study on the human obturator externus muscle with reference to anomalous muscle and anomalous fasciculus originating from the obturator externus muscle.

To elucidate the essential nature of the human obturator externus muscle (OE), the gross anatomy of the anomalous muscle and anomalous fasciculus originating from this muscle as well as the posterior division of the obturator nerve (P) were examined in 73 thighs of 45 Japanese adult cadavers. The investigation of anomalous muscle and anomalous fasciculus was effected by observation of the supernumerary muscular branch and supernumerary muscular twig from the P. The anomalous muscle occurring between the adductor brevis muscle (AB) and adductor minimus muscle (AMi) (37/73 thighs; 50.7%) and the anomalous fasciculus fused to the posterior surface of the AMi (18/73 thighs; 24.7%) were detected. It was demonstrated by the course of the P and the suppling nerve, that the OE was divided into its superior fasciculus (or fasciculi) (SF) and main belly by the P, moreover the anomalous muscle originated from the former and the anomalous fasciculus from the latter. Presumably, in the process of ontogeny, the SF of the original OE retained its original morphology (23/73 thighs; 31.5%), a part of the SF was converted to anomalous muscle (27/73 thighs; 37.0%), the entire SF was converted to anomalous muscle (10/73 thighs; 13.7%), and the entire SF underwent retrogression and disappeared (13/73 thighs; 17.8%). The presence (50/73 thighs; 68.5%) or absence (23/73 thighs; 31.5%) of piercing of the OE by the P seemed to depend upon the circumstances surrounding the morphological change in the SF. The original OE was considered to occur as an OE pierced by the P not possessing any supernumerary muscular branch or twig. Actually, the original OE was confirmed to occur with a low frequency (15/73 thighs; 20.5%). It was inferred that the original OE readily underwent variation in the process of ontogeny due to the influence of the obturator nerve. The segmental composition of the obturator nerve was considered not to be involved in the morphological change in the OE.

Adult↗

PubMed2003

[A variant hemoglobin found by dissociation of blood glucose from HbA1c on routine physical examination].

Discrepancy between HbA1c measured by routine HPLC and blood glucose was observed in four out of 340 persons on physical examination. We investigated whether this discrepancy was due to abnormal hemoglobin. HbA1c was measured by routine HPLC and latex agglutination. For further examinations, a hemoglobin specimen was analyzed by weak cation-exchange column(PolyCAT A) chromatography, ESI/MS and MS/MS. HbA1c levels measured by HPLC were about half of those measured by latex agglutination. An abnormal peak between HbA1c and HbA0 was detected on HPLC chromatography in three consanguineous persons. The abnormal hemoglobin from one of the related person was also confirmed by PolyCAT A chromatography. The hemoglobin specimen contained almost same amounts of normal HbA0 and abnormal Hb. Analyses of the globin by ESI/MS and MS/MS revealed that glutamate at the 22nd amino acid residue of the beta-chain was replaced by alanine. This variant was the same as HbG-Coushatta[beta 22(B4) Glu-->Ala]. Family studies showed that the variant was inherited as a dominant trait. The dissociation observed in the case was due to a presence of a variant hemoglobin. In the other case HbA1c levels measured by the two methods were similarly low, and no abnormal peak was observed on HPLC chromatography. Similar studies on the hemoglobin of this case did not disclose any abnormalities. The low values of HbA1c of this case were considered in the lowest region of the normal range.

Aged↗

PubMed2003

[Visualization of intracranial arteriovenous malformation using multivariate analysis].

Intracranial arteriovenous malformations(AVMs) are composed of native deformed vessels where arteries and veins are directly connected in the absence of capillary vessels, and have a complicated three-dimensional(3D) shape. The purpose of this study was to define precisely the location of AVM areas for stereotactic irradiation. The proposed method used a sequence of dynamic X-ray CT images with contrast and opaque media. We analyzed these images by a principal component analysis(PCA) method and extracted component images: artery, vein, and background images. Then we made a fusion image with these three images and displayed the AVM areas. Results showed that the proposed method could identify the physiological location of these AVMs areas. Furthermore, we reconstructed 3D fusion images using two-dimensional component images extracted by the PCA method.

Angiography, Digital Subtraction↗

PubMed2003

Obtaining location of I-125 seed sources for the prostate brachytherapy.

Treatment planning for ultrasound-guided transperitoneal I-125 permanent prostatic implants is a time consuming task, because this treatment uses many seeds (e.g. 50-80) and there are many solutions (seed positions) for optimizing the dose distribution. In conventional treatment planning for brachytherapy the locations of sources are usually input into a computer manually with reference to two X-ray films. We use so many sources in this treatment that we can hardly obtain accurate location of each source. That is, the identification of each seed with two X-ray films is very difficult. Even though we can use X-ray CT images for deciding on the source position, there are artifacts due to the high attenuation material. This paper proposes a method for obtaining accurate locations of radioactive sources from some projection data (e.g. RPO 60, 40, 20, LPO 60, 40, 20 and 0 deg.) with a reconstruction method. In our method for obtaining actual source positions we use an iterative image reconstruction technique. The results obtained by experiments with a simple prostate phantom and the RANDO phantom showed that the locations of dummy seeds were accurately decided with a reconstructed image by six or seven projection data.

Brachytherapy↗

PubMed2003

Hemoglobin variant HbG-coushatta (beta-22 Glu --> Ala) found by dissociation of blood glucose from values of HbA1C measured by HPLC.

OBJECTIVE: Unexpectedly low values of HbA1C, measured by HPLC compared with their blood glucose levels were found in three related persons. We investigated whether this discrepancy was due to abnormal hemoglobin. PATIENTS AND METHODS: HbA1C was measured by latex agglutination and ordinary HPLC. For further examination, a hemoglobin specimen from the 82-year-old female case was prepared and analyzed by PolyCAT A chromatography, ESI/MS and MS/MS. The HbA1C levels of the three cases measured by HPLC were lower than those measured by latex agglutination. The elution profiles on HPLC of the three gave an unusual peak between HbA1C and HbA0. RESULTS: PolyCAT A chromatography revealed two additional peaks which were not present in normal hemolysates. These peaks were revealed to correspond to abnormalities of HbA0 and HbA1C. The amounts of HbA0 and HbX were almost the same (1:0.85) and their glycation ratios were almost equal (5.2% and 5.9%). ESI/MS showed that the woman's intact globin contained an abnormal beta(X)-chain in addition to the normal alpha(A)- and beta(A)-chains. The molecular weight of this abnormal beta(X)-chain was 58 Da lower than that of the normal beta(A)-chain. Glutamate at the 22nd amino acid residue of the beta(A)-chain was replaced by alanine in the abnormal beta(X)-chain. This variant of Hb was revealed to be the same as HbG-Coushatta (beta-22 Glu --> Ala) from the library of variant Hb. Family studies showed that the variant was inherited as a dominant trait. CONCLUSION: The dissociation was due to underestimation of HbA1C in the measurement by HPLC which excluded glycated variant Hb.

Aged↗

PubMed2002

Degeneration of infrared receptor terminals of snakes caused by capsaicin.

Capsaicin, the main pungent ingredient in hot peppers (genus Capsicum), caused degeneration of the infrared receptor terminals in infrared sensitive snakes, Trimeresurus flavoviridis, when it was applied perineurally to a branch of the trigeminal nerve. The degeneration of the terminals was found 6 h after the application. This finding suggests that capsaicin stimulates this infrared receptor terminal, a kind of warm receptor terminal.

Animals↗