Biomedical subjects

K Yoshikawa

Publications and source records attributed to K Yoshikawa.

At least 19 recordsLinked to original sources

PubMed2007

Manipulation of cell-sized phospholipid-coated microdroplets and their use as biochemical microreactors.

Cell-sized water droplets coated by a phospholipid layer mimicking the inner surface of living cells were manipulated by laser tweezers and used as biochemical microreactors. The cell-sized phospholipid-coated microdroplets (CPMDs) consisted of a water droplet in mineral oil with a diameter of 1-100 microm and coated by 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine. We monitored the time development of biochemical reactions in a single CPMD obtained after the controlled fusion of two CPMDs containing a substrate and an enzyme, respectively. We present results on two enzymatic reactions: calcein production in the presence of esterase and green fluorescence protein expression.

Biochemistry↗

PubMed2006

Relationship between apical membrane elasticity and stress fiber organization in fibroblasts analyzed by fluorescence and atomic force microscopy.

To investigate the relationship between cellular microelasticity and the structural features of cytoskeletons (CSKs), a microindentation test for apical cell membranes and observation of the spatio-distribution of actin CSKs of fibroblasts were performed by fluorescence and atomic force microscopy (FM/AFM). The indentation depths of apical cell membranes were measured from AFM force-indentation (f-i) curves under equal final loads and mapped two-dimensionally to show the relative distribution of local microelasticity on cell membranes. Intracellular spatial distribution of actin CSKs was visualized fluorescently by high Z-resolution cross-sectional observation of a cell on which indentation mapping analysis had been performed in advance. Structural features of stress fibers (SFs) were observed as three typical patterns of dense SF, sparse SF and sparser SF cell groups, which were quantitated using the degree of orientation in apical SFs (ASFs) that had been defined using two-dimensional Fourier analysis. In indentation depth maps, the upper nuclear region was markedly softer than the pseudopodium region. The mean indentation depth of the upper nuclear region decreased with increased SF density in whole cells and the degree of orientation of ASF, although the pseudopodium region did not exhibit such a trend. The apical membrane of adhered cells was found to tend to stiffen with the increase in both density and degree of orientation of SFs.

Actins↗

PubMed2006

Structural transition of actin filament in a cell-sized water droplet with a phospholipid membrane.

Actin filament, F-actin, is a semiflexible polymer with a negative charge, and is one of the main constituents of cell membranes. To clarify the effect of cross talk between a phospholipid membrane and actin filaments in cells, we conducted microscopic observations on the structural changes in actin filaments in a cell-sized (several tens of micrometers in diameter) water droplet coated with a phospholipid membrane such as phosphatidylserine (PS; negatively charged head group) or phosphatidylethanolamine (PE; neutral head group) as a simple model of a living cell membrane. With PS, actin filaments are distributed uniformly in the water phase without adsorption onto the membrane surface between 2 and 6 mM Mg2+, while between 6 and 12 mM Mg2+, actin filaments are adsorbed onto the inner membrane surface. With PE, the actin filaments are uniformly adsorbed onto the inner membrane surface between 2 and 12 mM Mg2+. With both PS and PE membranes, at Mg2+ concentrations higher than 12 mM, thick bundles are formed in the bulk water droplet accompanied by the dissolution of actin filaments from the membrane surface. The attraction between actin filaments and membrane is attributable to an increase in the translational entropy of counterions accompanied by the adsorption of actin filaments onto the membrane surface. These results suggest that a microscopic water droplet coated with phospholipid can serve as an easy-to-handle model of cell membranes.

Journal Article↗

PubMed2006

Elongation/compaction of giant DNA caused by depletion interaction with a flexible polymer.

Structural changes in giant DNA induced by the addition of the flexible polymer Polyethylene Glycol (PEG) were examined by the method of single-DNA observation. In dilute DNA conditions, individual DNA assumes a compact state via a discrete coil-globule transition, whereas in concentrated solution, DNA molecules exhibit an extended conformation via macroscopic phase segregation. The long-axis length of the stretched state in DNA is about 10(3) times larger than that of the compact state. Phase segregation at high DNA concentrations occurs at lower PEG concentrations than the compaction at low DNA concentrations. These opposite changes in the conformation of DNA molecule are interpreted in terms of the free energy, including depletion interaction.

Bacteriophage T4↗

PubMed2006

CyberKnife stereotactic radiotherapy for patients with malignant glioma.

OBJECTIVE: The CyberKnife is a new frameless image-guided radiosurgical modality. The authors report on their experience using the CyberKnife in 25 patients with malignant gliomas. METHODS: Twenty-five patients with histologically proven malignant gliomas (18 glioblastoma: GB, 7 anaplastic astrocytoma: AA) were treated with the CyberKnife at Konan St. Hill Hospital between June 1998 and November 2002. CyberKnife therapy was performed on 44 lesions (31 GB lesions, 13 AA lesions) in the 25 patients. The median target volume was 19.1 mL (range: 0.3 - 90.2). The median prescribed dose was 20.3 Gy (range: 13.9 - 26.4). Patient-, tumor-, and treatment-related variables were analyzed by univariate analysis, and survival curves were generated by the Kaplan-Meier product limit. RESULTS: In the 18 GB patients, the median survival after diagnosis was 20.7 months (82.6 weeks) with a mean follow-up of 85.7 weeks. Of the 7 AA patients, 6 were alive at the time of analysis with follow-up periods ranging from 11.4 to 52.8 months. Patients younger than 70 years had a median survival after diagnosis of 37.1 months, compared to 12.4 months for older patients (p = 0.003). Similarly, patients with well-controlled lesions had a median survival after diagnosis of 39.8 months compared to 16.0 months for those with uncontrolled lesions (p = 0.031). Late delayed radiation necrosis was seen in 1 GB patient. No other patient suffered acute or delayed neurological morbidity after CyberKnife therapy. CONCLUSION: This is the first report of CyberKnife stereotactic radiotherapy applied to the treatment of malignant gliomas. The frameless and painless CyberKnife stereotactic radiotherapy has the potential to be as useful for treatment of malignant glioma as other radiosurgical modalities.

Adult↗

PubMed2006

The role of cyberknife radiosurgery/radiotherapy for brain metastases of multiple or large-size tumors.

OBJECTIVE: Focused, highly targeted radiosurgery and fractionated radiotherapy using the Cyberknife are useful treatments for multiple or large metastases. Here we present our results of Cyberknife radiosurgery for 71 patients with 148 metastatic brain lesions. METHODS: There were 32 women and 39 men with a median age of 63 (range: 30-88) years. Radiographic follow-up was available for 60 patients with 104 lesions. The mean and median initial volumes of the tumor per lesion were 6.6 and 2.9 cm(3) (range: 0.1-53.2 cm(3)), respectively, at the time of the initial Cyberknife treatment. Forty patients (56%) had a single lesion, and 31 (44%) had multiple lesions (range: 2-7) at initial treatment. The number of fractions ranged from 1 to 3, and forty (27%) of 148 lesions were treated by a fractionated course of Cyberknife therapy. The mean marginal dose was 20.2 Gy (range 7.8-30.1 Gy, median: 20.7 Gy). RESULTS: At 44 weeks of median follow-up, there were no permanent symptoms resulting from radiation necrosis. Overall 6-month and 1-year survival rates were 74% and 47%, respectively, and the median survival time was 56 weeks. The Karnofsky performance score and extracranial metastasis were significant prognostic factors at 6 months and 1 year, respectively, in both univariate and multivariate analyses. Age or multiple metastases did not influence prognosis at 6 months and 1 year. Local control was achieved in 83% (86 lesions). After additional radiosurgical or surgical salvage, no patient died as a result of intracranial disease. Twenty-five patients developed 92 new metastases (range 1-13) outside of the treated lesions with 22.4 weeks of median follow-up. Among them, 21 patients (84 lesions) were treated by salvage Cyberknife. CONCLUSION: Despite the inclusion of an unfavorable group of patients with large tumors, our results for survival and tumor control rates are comparable to those of published series. The Cyberknife provides the advantage of allowing for fractionated treatment to multiple or large-size tumors.

Adult↗

PubMed2006

Different results of the Salmonella umu test between three isomers of phenylenediamine (PDA) derivatives.

A post-treatment assay of the umu test was performed to detect genotoxicity of 10 phenylenediamine (PDA) derivatives using Salmonella typhimurium TA1535/pSK1002 with/without S9 mix. Seven chemicals (o-PDA, 4-chloro-o-PDA, 4-nitro-o-PDA, p-PDA, 2-chloro-p-PDA, 2-nitro-p-PDA, and 2,5-diaminotoluene) showed positive results with S9 mix, but three chemicals (m-PDA, 4-chloro-m-PDA, and 2,4-diaminotoluene) were negative with and without S9 mix. Four of 7 chemicals (o-PDA, 4-chloro-o-PDA, 4-nitro-o-PDA, and 2-nitro-p-PDA) that gave positive results with S9 mix were also positive without S9 mix. These results indicate that the genotoxicity of PDA derivative possessing m-position amino substituents was not detected in the umu post-treatment assay using TA1535/pSK1002.

Animals↗

PubMed2005

Comparative analysis of transcriptional responses to saline stress in the laboratory and brewing strains of Saccharomyces cerevisiae with DNA microarray.

To construct yeast strains showing tolerance to high salt concentration stress, we analyzed the transcriptional response to high NaCl concentration stress in the yeast Saccharomyces cerevisiae using DNA microarray and compared between two yeast strains, a laboratory strain and a brewing one, which is known as a stress-tolerant strain. Gene expression dynamically changed following the addition of NaCl in both yeast strains, but the degree of change in the gene expression level in the laboratory strain was larger than that in the brewing strain. The response of gene expression to the low NaCl concentration stress was faster than that to the high NaCl concentration stress in both strains. Expressions of the genes encoding enzymes involved in carbohydrate metabolism and energy production in both strains or amino acid metabolism in the brewing strain were increased under high NaCl concentration conditions. Moreover, the genes encoding sodium ion efflux pump and copper metallothionein proteins were more highly expressed in the brewing strain than in the laboratory strain. According to the results of transcriptome analysis, candidate genes for the creation of stress-tolerant strain were selected, and the effect of overexpression of candidate genes on the tolerance to high NaCl concentration stress was evaluated. Overexpression of the GPD1 gene encoding glycerol-3-phosphate dehydrogenase, ENA1 encoding sodium ion efflux protein, and CUP1 encoding copper metallothionein conferred high salt stress tolerance to yeast cells, and our selection of candidate genes for the creation of stress-tolerant yeast strains based on the transcriptome data was validated.

Gene Expression Regulation, Fungal↗

PubMed2005

Sensing the distance to a source of periodic oscillations in a nonlinear chemical medium with the output information coded in frequency of excitation pulses.

A spatially distributed excitable chemical medium can collect and process information coded in the propagating pulses of excitation. We consider the problem of distance sensing with the use of a nonlinear chemical medium. We demonstrate that a sensor that can feel the distance separating it from a source of periodic excitations can be constructed by a proper geometrical arrangement of excitable and nonexcitable regions. The sensor returns information about the distance in the frequency of outgoing pulses. The sensor functionality is tested by simulations based on the Rovinsky-Zhabotinsky model. The results are confirmed in experiments performed for a ruthenium-catalyzed Belousov-Zhabotinsky reaction.

Journal Article↗

PubMed2005

Different pathways in mechanical unfolding/folding cycle of a single semiflexible polymer.

Kinetics of conformational change of a semiflexible polymer under mechanical external field were investigated with Langevin dynamics simulations. It is found that a semiflexible polymer exhibits large hysteresis in mechanical folding/unfolding cycle even with a slow operation, whereas in a flexible polymer, the hysteresis almost disappears at a sufficiently slow operation. This suggests that the essential features of the structural transition of a semiflexible polymer should be interpreted at least on a two-dimensional phase space. The appearance of such large hysteresis is discussed in relation to different pathways in the loading and unloading processes. By using a minimal two-variable model, the hysteresis loop is described in terms of different pathways on the transition between two stable states.

Journal Article↗

PubMed2005

Morphological variation in a toroid generated from a single polymer chain.

A single semiflexible polymer chain folds into a toroidal object under poor solvent conditions. In this study, we examined the morphological change in such a toroidal state as a function of the cross-sectional area and stiffness of the chain together with the surface energy, which characterizes the segmental interaction parameter. Changes in the thickness and outer/inner radius on a toroid are interpreted in terms of these parameters. Our theoretical expectation corresponds to the actual morphological changes in a single giant DNA molecule as observed by electron microscopy.

Journal Article↗

PubMed2005

MR tractography for the evaluation of functional recovery from lenticulostriate infarcts.

OBJECTIVE: To evaluate the anatomic and clinical relationship between the lenticulostriate artery (LSA) territory and the corticospinal tract (CST) in patients with acute infarcts in this territory using MR tractography. METHODS: Thirteen consecutive patients who presented with acute infarcts in the LSA territory and who also had undergone an MRI study within 3 days after symptom onset were studied. Visualization of the CST was achieved by postprocessing the acquired diffusion tensor imaging data. To classify lesion location, the LSA territory was divided into four subsegments, the boundaries of which were drawn by axial and coronal planes crossing through the foramen of Monro. Infarct volume and extent of CST involvement were measured and compared with neurologic findings. RESULTS: All of the infarcts were located in the posterior segment. All of the depicted CSTs crossed the LSA territory only at the posterosuperior quadrant. The extent of CST involvement within the infarcts was correlated with the severity of the patient's motor deficit (p < 0.01) and with the clinical outcome (p < 0.05). CONCLUSIONS: The corticospinal tracts (CSTs) crossed the lenticulostriate artery territory exclusively at the posterosuperior quadrant, and the degree of CST involvement within the infarcts was directly related to stroke severity and functional recovery.

Adult↗

PubMed2005

Quantitative evaluation of cerebrovascular reactivity in brain tissue by a refill kinetic method of transcranial ultrasonic perfusion imaging: a comparison with Doppler sonography.

UNLABELLED: To confirm the reliability of a refill kinetic method of ultrasonic harmonic perfusion imaging (HPI) capable of quantifying separate parameters of microvascular blood flow velocity and volume in brain tissue, we evaluated acetazolamide (ACZ) cerebrovascular reactivity by transcranial HPI in comparison with Doppler sonography (TCD). Methods. HPI during continuous Levovist infusion with changing pulsing intervals (t) and TCD time-averaged maximum velocity (TAMX) in the middle and posterior cerebral arteries were evaluated before and after ACZ administration in 12 patients, 8 without and 4 with a temporal skull defect. Plateau value (A) and rise rate (beta) of intensity (I) represented by HPI time-intensity curves of I(t) = A(1 - e(-beta*t)) were analyzed on the axial diencephalic plane. RESULTS: 1) A significantly decreased in proportion to the region of interest location depth only in the intact skull cases. 2) Despite inter- and intra-individual data scattering, in correspondence with TAMX increases after ACZ, significant beta increases were more frequently identified than increases of A. CONCLUSIONS: Cerebral vasoreactivity analysis utilizing refill kinetics of transcranial HPI can potentially provide separate quantification based on microvascular blood velocity and volume (capillary patency) with consideration of depth-dependant ultrasound attenuation. This should be suitable for bedside evaluation of neurointensive care patients.

Acetazolamide↗

PubMed2005

Contrast-enhanced dynamic MR imaging parameters and histological types of invasive ductal carcinoma of breast.

The diagnosis of breast cancer has progressed owing to the improvement of both MRI equipments and MR techniques. CE-MRI is expected to be more useful for diagnosis of the existence and characteristics of breast cancer than mammography and ultrasound. Forty-three breast cancer patients, who underwent breast MRI examination before surgery and had histologically confirmed invasive ductal carcinomas, were included in this study. In 19, seven and 17 of them, carcinomas were histologically classified as papillotubular, solid-tubular, and scirrhous type, respectively. In dynamic MRI studies, the MR parameters were calculated from the signal intensity determined before and at five time-points after a bolus of 0.1 mmol Gd-DTPA/kg in the chosen region of interest (ROI). The differential analysis of MR parameters with reference to histopathology was performed by one-way analysis of variance (ANOVA) in dynamic studies. Four of 15 parameters analyzed, ENH1-2, ENH1, MSLP, and SAT3, were significantly different between papillotubular and scirrhous carcinoma. The dynamic curve of papillotubular carcinoma reached a maximum in the very early phase and then decreased slowly (linear pattern), while that of scirrhous carcinoma peaked in the slightly later phase and then decreased (parabolic pattern). In the differential analysis by Kruskal-Wallis test, although no significant differences were found in any morphological parameters among three histological types, spicula formation and rim enhancement tended to appear comparatively frequently in scirrhous and solid-tubular carcinoma. CE-MRI might reveal the differences of growth characteristics among different histological types of breast carcinomas and provide a diagnostic method useful for estimation of the prognosis of breast cancer.

Adult↗

PubMed2005

Image-guided stereotactic radiosurgery with the CyberKnife for pituitary adenomas.

This study demonstrates the clinical usefulness of image-guided fractionated stereotactic radiosurgery with the CyberKnife system. Twenty-one patients with pituitary adenomas received image-guided stereotactic radiosurgery with the CyberKnife, and were followed up for more than 18 months. The patients consisted of 14 with non-functioning adenomas, 3 with prolactinomas, 2 with acromegaly, and 2 with ACTH-producing tumors. In 20 cases, fractionated radiosurgery was performed. The change in the tumor volume, visual acuity, hormonal function, and complications by this therapy were analyzed in each case. The volume of the tumors ranged from 0.2 cm (3) to 34.9 cm (3) (mean +/- SD: 11.3 +/- 9.2 cm (3)). The mean volumes of the non-functioning and functioning adenomas were 13.3 cm (3) and 7.5 cm (3), respectively. The marginal irradiation dose ranged from 6.4 Gy to 27.7 Gy (mean: non-functioning adenomas 12.6 Gy, functioning adenomas 17.5 Gy), as a dose of a single fraction. The follow-up periods ranged from 18 months to 59 months (mean +/- SD: 35.3 +/- 10.7 months). The tumor control rate was 95.2 %. In 1 case, visual acuity worsened due to cystic enlargement of the tumor. Hormonal function improved in all of the 7 functioning adenomas. The hormone level normalized in 1 prolactinoma, and decreased to less than normal in 1 ACTH-producing adenoma. In 2 cases, hypopituitarism occurred after the therapy. Image-guided stereotactic radiosurgery with the CyberKnife is effective and safe against relatively large pituitary adenomas. Careful long-term follow-up of the patients is necessary because of delayed cystic enlargement of the tumor in rare cases.

Adenoma↗

PubMed2005

Prevention of amputation caused by rheumatic diseases following a novel therapy of exposing bone marrow, occlusive dressing and subsequent epidermal grafting.

BACKGROUND: Wounds with exposed bones caused by rheumatic diseases commonly result in amputation despite progress in our understanding of wound-healing mechanisms. OBJECTIVES: To determine whether an experimental therapy of bone marrow exposure, an occlusive dressing and subsequent grafting of epidermal sheets accelerates healing and reduces the need for amputation in patients with rheumatic diseases. METHODS: Fifteen patients, including those with rheumatoid arthritis or systemic sclerosis, who had wounds with exposed bones were treated either with the standard procedure, consisting of local wound care, debridement with a scalpel, bed rest and parenteral antibiotics (n = 8), or with a newly developed experimental procedure (n = 7). In that new procedure, the affected bone was initially exposed by debridement with a scalpel, followed by partial excision with a bone scraper until bleeding was observed from the exposed bone. The lesions were immediately covered with an occlusive dressing, and were eventually treated with epidermal grafts obtained from suction blisters. RESULTS: A comparison with standard therapy demonstrated that the time needed for wound healing was similar, but that the newly developed combination therapy reduced the risk of amputation (P = 0.020). No skin ulcers or erosions were observed for at least 1 year in five of seven patients (72%) due to the adoption of stable palmoplantar-type characteristics in grafts derived from the trunk epidermis. CONCLUSIONS: Our study indicates that exposure of bone marrow cells plus an occlusive dressing accelerates the healing of skin ulcers at least partly through the preparation of a healthy well-granulated wound bed and that subsequent epidermal grafting achieves site-specific differentiation through epithelial-mesenchymal interactions.

Adult↗

PubMed2005

Bone marrow cells differentiate into wound myofibroblasts and accelerate the healing of wounds with exposed bones when combined with an occlusive dressing.

BACKGROUND: The usefulness of bone marrow cells in accelerating wound healing has not been evaluated despite increasing evidence that bone marrow contains mesenchymal stem cells that have multipotentiality to differentiate into various types of cells after they enter the microenvironment of a specific tissue (niche). OBJECTIVES: To determine the effects of bone marrow cells and occlusive dressings in promoting wound healing in rats. METHODS: We investigated by grafting, biopsy and immunohistochemistry whether various types of cells derived from green fluorescent protein (GFP)-transgenic rats would differentiate into wound component cells when administered topically on the wounds of rats. We also investigated whether topical application of bone marrow cells with an occlusive dressing would accelerate the healing of wounds with exposed bones, as measured by planimetry. RESULTS: GFP-labelled bone marrow cells contained multipotent stem cells that sufficiently differentiated into wound myofibroblasts presenting with alpha-smooth muscle actin in granulation tissue. Other types of cells, including myocytes, adipocytes, peripheral blood cells from buffy coat and dermal fibroblasts, did not express myofibroblast characteristics morphologically or immunohistochemically. Application of bone marrow cells and an occlusive dressing accelerated the repair of wounds with exposed bones, compared with an occlusive dressing only or with the topical administration of bone marrow cells plus a semidry to dry dressing. CONCLUSIONS: Our study indicates that bone marrow cells accelerate the healing of wounds at least in part through their differentiation into wound myofibroblasts. Thus, treatment of wounds with bone marrow cells and a supportive occlusive dressing is effective in promoting the formation of healthy granulation tissue and also for the preparation of an ideal wound bed.

Animals↗

PubMed2004

Magnetic resonance and biochemical studies during pentylenetetrazole-kindling development: the relationship between nitric oxide, neuronal nitric oxide synthase and seizures.

The major aim of this study was to elucidate the role of nitric oxide (NO) in the development of pentylenetetrazole (PTZ)-kindling as an animal model of primary generalized epilepsy. The daily administration of PTZ is associated with an increase in the amount of neuronal nitric oxide synthase (nNOS). NO generation was measured directly by in vivo and ex vivo electron paramagnetic resonance on rodents undergoing progressive convulsions. We found that primary generalized epilepsy is caused by NO induction during the persistent up-regulation of nNOS expression, but that NO induction is not associated with severe generalized seizures following long-term kindling phenomena after PTZ withdrawal. Morphological changes in the brain structure of rats were measured by magnetic resonance imaging during epileptic convulsions induced by repetitive administration of PTZ. Cerebellum volume for kindled rats decreased 20% but not in rats treated with the nNOS inhibitor, 3Br-7NI, suggesting that generation of NO in the cerebellum is related to decrease in cerebellum volume following PTZ-kindling.

Analysis of Variance↗