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Biomedical subjects

K Asami

Publications and source records attributed to K Asami.

At least 91 records · Page 5Linked to original sources
PubMed1992

[Transient subacute encephalopathy induced by high-dose methotrexate treatment in children with acute lymphoblastic leukemia and malignant lymphoma].

Transient subacute encephalopathy was detected in 4 of 83 patients undergoing treatment with high-dose methotrexate (HD-MTX) and citrovorum factor rescue for childhood acute lymphoblastic leukemia and malignant lymphoma from 1984 to 1991. Subacute encephalopathy occurred in relatively older patients and early in the course of treatment with HD-MTX. The average interval between the HD-MTX course and the onset of the neurologic disturbance was 6.5 days. All 4 patients treated had no neurological sequelae. Laboratory evaluations disclosed nontoxic plasma MTX levels at onset of symptom and not detected in liquor. CT in 4 patients disclosed no abnormality, but MR images revealed abnormal signal intensity patterns of cerebral white matter in 2 cases. In one case the abnormal MR finding resolved after 3 months. The pathogenesis of this neurologic symptom remains unknown, but further HD-MTX treatment may be acceptable in follow-up of MR image, because the prognosis of subacute encephalopathy seems favorable.

Adolescent↗
PubMed1990

Frequency domain analysis of membrane capacitance of cultured cells (HeLa and myeloma) using the micropipette technique.

The membrane capacitance and conductance of cultured cells (HeLa and mouse myeloma) are investigated using the micropipette method. Mean values of the membrane capacities were found to be 1.9 microF/cm2 for HeLa cells and 1.0 microF/cm2 for myeloma cells. These values are in agreement with those obtained using the suspension method. Whereas the suspension method is unable to provide the information on membrane conductance, the micropipette method is able to measure even an extremely small membrane conductance if leakage current is negligibly small. The membrane conductances were found, using this technique, to be approximately 90-100 microS/cm2 for both HeLa and myeloma cells. One of the purposes of this study is to establish the frequency profile of membrane capacitance. It was found, however, that membrane capacitances of these cells are independent of frequency between 1 Hz and 1 KHz within the resolution of this technique.

Animals↗
PubMed1989

Dielectric properties of mouse lymphocytes and erythrocytes.

In order to study the effect of the nucleus on dielectric behavior of the whole cell, permittivity (dielectric constant) and conductivity of mouse lymphocytes and erythrocytes were measured over a frequency range from 0.1 to 250 MHz. Erythrocytes (spherocytes) showed a single dielectric dispersion, which was explained by a single-shell model that is a conducting sphere covered with a thin insulating shell. On the other hand, lymphocytes showed a broad dielectric dispersion curve which was composed of two subdispersions. The high-frequency subdispersion, which was not found for erythrocytes, was assigned to the Maxwell-Wagner dispersion of the nucleus occupying about 65% of the total cell volume. Analysis of the lymphocyte dispersion was carried out by a double-shell model, in which a shelled sphere, i.e., nucleus, is incorporated into the single-shell model. The following electrical parameters were consequently estimated; the capacitance of the plasma membrane, 0.86 microF.cm-2; the conductivity of the cytoplasm, 3.2 mS.cm-1; the capacitance and conductance of the nuclear envelope are, respectively, 0.62 microF.cm-2 and 15 S.cm-2, and the permittivity and conductivity of the nucleoplasm are 52 and 13.5 mS.cm-1.

Algorithms↗
PubMed1989

Changes in the nuclear protein kinase activities in the regenerating liver of partially irradiated rat.

X rays (4.8 Gy) inhibit both DNA synthesis and phosphorylation of histone H1 in the regenerating liver of the rat. To determine the cause of the inhibition of histone H1 phosphorylation, changes in the nuclear protein kinase activities during the prereplicative phase of regeneration were measured. The cAMP-dependent protein kinase activity was low during regeneration, and the changes in the activity were not statistically significant. The cAMP-independent protein kinase activity increased at 15 h, decreased at 18 h, and increased again at 24 h after partial hepatectomy. X irradiation prior to partial hepatectomy did not inhibit the increase at 15 h, but it did inhibit the increase at 24 h. The activity was not inhibited by isoquinolinesulfonamide inhibitors such as H-7, and it was activated by a commercial preparation of an inhibitor protein of the cAMP-dependent kinase. It was also inhibited by quercetin. The possibility that the radiation-sensitive nuclear protein kinase is a nuclear cAMP-independent protein kinase specific for histone H1 is considered.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1988

Frequency domain studies of impedance characteristics of biological cells using micropipet technique. I. Erythrocyte.

This study aims at precise measurement of the membrane capacity and its frequency dependence of small biological cells using the micropipet technique. The use of AC fields as an input signal enables the magnitude and phase angle of membrane impedance to be measured at various frequencies. The micropipet technique was applied to human erythrocyte, and passive membrane capacity and conductivity were determined between 4 Hz and 10 KHz. Membrane capacity thus determined changed from 1.05 to 0.73 microF/cm2 between 4 Hz and 10 KHz. In addition to the micropipet technique, we used suspension method between 50 KHz and 10 MHz for the purpose of supplementing the new method with the one which has been in use for many years. We obtained a membrane capacity of 0.65-0.8 microF/cm2 using this technique. These values agree with the capacitance obtained with the micropipet method. Although this paper discusses only human erythrocytes, the study has been performed with lymphocytes and various forms of cancer cells. This paper is the first of the series of reports on frequency domain studies of the impedance characteristics of various biological cells.

Electric Conductivity↗
PubMed1987

Passive electrical properties of the membrane and cytoplasm of cultured rat basophil leukemia cells. I. Dielectric behavior of cell suspensions in 0.01-500 MHz and its simulation with a single-shell model.

Frequency dependence of relative permittivity (dielectric constant) and conductivity, or the 'dielectric dispersion', of cultured cells (RBL-1 line) in suspension was measured using a fast impedance analyzer system capable of scanning 92 frequency points over a 10 kHz-500 MHz range within 80 s. Examination of the resulting dispersion curves of an improved reliability revealed that the dispersions consisted of at least two separate components. The low-frequency component (dispersion 1) had a permittivity increment (delta epsilon) of 10(3)-10(4) and a characteristic frequency (fc) at several hundred kHz; for the high-frequency component (dispersion 2), delta epsilon was smaller by a factor of 10(2) and fc = 10-30 MHz. Increments delta epsilon for both components increased with the volume fraction of cell suspension, while fc did not change appreciably as long as the conductivity of suspending medium was fixed. By fitting a model for shelled spheres (the 'single-shell' model) to the data of dispersion 1, the dielectric capacity of the plasma membrane phase (Cm) was estimated to be approx. 1.4 microF/cm2 for the cells in an isotonic medium. However, simulation by this particular shell model failed to reproduce the entire dispersion profile leaving a sizable discrepancy between theory and experiment especially at frequencies above 1 MHz where dispersion 2 took place. This discrepancy could not be filled up even by taking into consideration either the effect of cell size distribution actually determined or that of possible heterogeneity in the intracellular conductivity. The present data strongly indicate the need for a more penetrating model that effectively accounts for the behavior of dispersion 2.

Animals↗
PubMed1987

Passive electrical properties of the membrane and cytoplasm of cultured rat basophil leukemia cells. II. Effects of osmotic perturbation.

The effects of osmotic perturbation on the dielectric behavior of cultured rat basophilic leukemia (RBL-1) cells were examined. Cells exposed to osmolalities (pi) of 145-650 mosmolal showed dielectric dispersions of the following characteristics: Permittivity increment delta epsilon(= epsilon l - epsilon h where epsilon l and epsilon h refer to the low- and high-frequency limit values) for a fixed volume concentration increased with pi; gross permittivity behavior was apparently of a typical Cole-Cole type; however, frequency dependence of conductivity was undulant and could be simulated by a superposition of two separate Cole-Cole type dispersions; separation of these subdispersions along the frequency axis was an increasing function of pi, and so was conductivity increment in the high-frequency region. As examined by light microscopy, the cells were spherical in spite of imposed anisotonic stresses and behaved as osmometers at 200-410 mosmolal. When normalized by dividing by number (not volume) concentration, delta epsilon remained relatively constant irrespective of pi. Apparent membrane capacities (Cm), analyzed by applying a single-shell model, increased systematically from a hypotonic value of approx. 1 microF/cm2 up to 5 microF/cm2 at 650 mosmolal. This increase was interpreted as due to increased cellular 'surface/volume' ratios that were confirmed by scanning electron microscopy. Cole-Cole's beta parameter, which culminated around 0.9 for isotonic cells and declined to approx. 0.8 for anisotonic cells, did not parallel the broadening of cell volume distribution but appeared to reflect changes in the intracellular conductivity caused by the anisotonic challenge. The results indicate that the dispersion method can probe changes in surface morphology as well as subcellular organelles' constitution of living cells.

Animals↗
PubMed1987

Elevation of cerebrospinal fluid sialic acid concentration in children with central nervous system leukemia.

We studied sialic acid in the cerebrospinal fluid (CSF) of 52 children with leukemia and 51 children with non-leukemic diseases. The CSF sialic acid concentration in the children with central nervous system (CNS) leukemia was significantly higher than that in the children with acute lymphoblastic leukemia without CNS involvement, acute non-lymphocytic leukemia without CNS involvement, non-hemopoietic diseases, non-suppurative meningitis, epilepsy, and other neurologic diseases. Serial determinations revealed a rapid decline in the CSF sialic acid concentrations in the patients with CNS leukemia who responded well to the therapy and who were free from relapse of CNS leukemia. The simultaneously determined CSF beta 2 microglobulin concentration did not show any significant changes. These results suggest that the CSF sialic acid may be a good indicator of CNS leukemia.

Adolescent↗
PubMed1987

Correlation of positive syphilis serology with invasive amebiasis in Japan.

Approximately 20% of 52 Japanese males with invasive amebiasis confirmed by gel diffusion precipitin test (GDP) were positive by both Treponema pallidum hemagglutination test (TPHA) and nontreponemal antigen tests, and an additional 20% were positive by TPHA alone. However, none of 109 GDP-negative Japanese males without invasive amebiasis were positive on these serologic tests for syphilis. At least 2 bisexuals and 4 homosexuals were among those with invasive amebiasis. All of these biased males were positive on both TPHA and nontreponemal antigen tests. Four of the biased males had liver abscess and 2 had amebic dysentery or colitis. Bisexual or homosexual males were not found in the negative GDP group. These observations suggest that sexually transmitted amebiasis due to Entamoeba histolytica occurs among sexually biased males in Japan.

Adolescent↗
PubMed1987

Synthesis and phosphorylation of histone H1 and high mobility group proteins in the regenerating rat liver after X irradiation.

A rat was irradiated to the upper abdomen including the liver and then partially hepatectomized. The subsequent synthesis and phosphorylation of histone H1 and nonhistone chromosomal high mobility group (HMG) proteins were investigated. Incorporation of [3H]lysine into histone H1 was increased and reached its peak at 27 h after hepatectomy, and 14 Gy of X rays inhibited the increase. Increase in the incorporation of [3H]lysine into HMG (1 + 2), 14, and 17 which occurred around 27 h after hepatectomy was not inhibited by 14 Gy irradiation. Phosphorylation of histone H1, measured with 32Pi incorporation in vivo, was maximal between 21 and 24 h, and it was inhibited by 4.8 Gy of X rays and delayed with 1.9 Gy. Phosphorylation of HMG 14, which was the only HMG protein phosphorylated under present conditions, was not affected by X irradiation. The [3H]thymidine incorporation into nuclear DNA started increasing at 21 h and reached its maximum at 27 h after hepatectomy. X irradiation with 4.8 Gy inhibited the incorporation, and 1.9 Gy lowered it.

Animals↗
PubMed1984

Dielectric analysis of mitochondria isolated from rat liver. I. Swollen mitoplasts as simulated by a single-shell model.

A re-evaluation of the dielectric studies on isolated mitochondria (Pauly, H., Packer, L. and Schwan, H.P. (1960) J. Biophys. Biochem. Cytol. 7, 589-601, and ibid. 7, 603-612) is presented. The suspensions of 'mitoplasts' prepared from rat liver mitochondria by a hyposmotic (10 mM KCl) treatment showed a dielectric dispersion with its characteristic frequency lying in the 1-100 MHz range. In the analysis of data special emphasis was put on the choice of the theoretical models to employ after scrutiny of their applicability to the suspensions tested. As such we adopted the theory of Hanai et al. (Hanai, T., Asami, K., and Koizumi, N. (1979) Bull. Inst. Chem. Res., Kyoto Univ. 57, 297-305) that was advanced to include concentrated suspensions of shelled spheres. Curve fittings based on that theory resulted in a better agreement with experiment than the fittings based on a conventional theory for dilute suspensions. Major findings from our analyses on the swollen mitoplasts are that: (i) the limiting membrane of the mitoplasts has a specific electrical capacity of 1 microF/cm2, (ii) the ratio of permittivity (or dielectric constant) for the mitoplast interior and permittivity for the external medium is 0.6-0.7, and (iii) the conductivity ratio between the interior phase and the medium is approx. 0.6. Reasons for discrepancy between the results of Pauly et al. and ours are discussed.

Animals↗
PubMed1984

Dielectric analysis of mitochondria isolated from rat liver. II. Intact mitochondria as simulated by a double-shell model.

The dielectric dispersion of isolated intact mitochondria in suspension has been measured between 10 kHz and 500 MHz. In isotonic KCl media at 4 degrees C, the mitochondria maintained their characteristic 'double membrane' structure as examined by electron microscopy, and the observed dispersion curves were successfully simulated in terms of a superposition of two sub-dispersions having different characteristic frequencies and different permittivity magnitudes. Taking these observations into account we analyzed the dispersion data on the basis of a 'double-shell' model in which two concentric shells are meant to represent the mitochondrial outer and inner membranes. The analyses by a computerized curve-fitting method revealed that: (i) electric capacities for the outer and the inner membrane are 1.7 and 0.5 microF/cm2, respectively, (ii) relative permittivity for the inner compartment (or the equivalent homogeneous matrical space) = 50-60, (iii) outer compartment-to-external conductivity ratio = 0.4-0.6, and (iv) inner compartment-to-external conductivity ratio = 0.14. The implications of these parameter values are discussed with due attention paid to the limitations inherent in our 'double-shell' model approach.

Animals↗
PubMed1984

Health status of Indochinese refugees in Japan: statistical analyses on anemia, eosinophilia and serum alkaline phosphatase.

Detailed statistical analyses were attempted on anemia, eosinophilia and elevation in serum alkaline phosphatase in the Indochinese refugees in Japan. A high statistical correlation was found between hemoglobin concentration and hematocrit for most of the refugees except the Cambodian females. Refugees with parasitic infections, particularly hookworm infection had significantly lower values for hemoglobin concentration and hematocrit. Significant eosinophilia was observed in the refugees infected with hookworms, Strongyloides stercoralis, Rhabditis sp., Endolimax nana and/or Hymenolepis nana. However, these parasites were found in the same subpopulations more frequently than expected by chance. Elevation in serum alkaline phosphatase was observed in young Cambodian immigrants. Analyses showed that the variations of this enzyme could be well predictable by those of enzymes such as serum glutamic oxaloacetic transaminase, which are good markers for liver functions, in Cambodian immigrants, 13-24 of age, whereas no such correlation was observed in non-Cambodians of the same age group.

Adolescent↗