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Biomedical subjects

Y Bito

Publications and source records attributed to Y Bito.

At least 19 recordsLinked to original sources
PubMed1996

Expansion of the spectral bandwidth by spatial and chemical shift selective saturation in high-speed magnetic resonance spectroscopic imaging.

A new spectral bandwidth expansion technique for high-speed magnetic resonance spectroscopic imaging (MRSI) based on an echo-planar technique is presented. This expansion can be achieved by spatial and chemical shift selective saturation without increasing the total measurement time. In addition, displacement along the slice-select direction due to chemical-shift differences between the measured compounds is also suppressed. Experimental results are shown using a phantom consisting of benzene and acetone. High spatial resolution (1 x 1 mm2) and wide spectral bandwidth (1.5-1.8 kHz; the effective spectral bandwidth has been doubled) are obtained without the displacement along the slice-select direction.

Echo-Planar Imaging↗
PubMed1995

Echo-planar diffusion spectroscopic imaging.

High-speed diffusion spectroscopic imaging based on an echo-planar technique is presented. A pair of diffusion gradients is applied prior to a rapidly oscillating magnetic field gradient which encodes both chemical shift and spatial information. By applying this technique to a phantom consisting of acetone and water, a diffusion spectroscopic image is obtained in about 15 min, about 64 times faster than the time required in the conventional method. The measured diffusion coefficients show good agreement with previously reported values. This kind of diffusion spectroscopic imaging is expected to provide a way to observe more specific metabolism.

Acetone↗
PubMed1994

[Advance of magnetic resonance spectroscopic imaging (MRSI) techniques].

Magnetic resonance spectroscopic imaging (MRSI) can provide density images of various metabolites in the human body, in vivo, by utilizing chemical shift. This technique has received attention as a new method for analyzing the diseased state, via metabolism. It increases the accuracy of diagnosis and provides hope for early diagnosis of brain disease. However, because a measurement time of more than ten minutes to one hour is required for imaging, it has been difficult to use MRSI techniques for clinical diagnosis. Improved techniques for high-speed imaging have recently been developed. This review describes the recent advances in this field.

Animals↗
PubMed1989

Characterization of activation of a partially defective B cell subpopulation with immunocompetence restricted to IgM and IgA.

A B-cell subpopulation (BM-A cell) responding to an antigen with the production of IgM and IgA plaque-forming cells but not of IgG plaque-forming cells was isolated from neonatally bursectomized chickens and was examined for the mode of activation by B-cell mitogens. The BM-A cells did not elevate both glucose consumption and protein synthesis with the B-cell mitogens, in striking contrast to normal B cells. The BM-A cells were also not activated by an activator of protein kinase C, phorbol myristate acetate. Both anti-Ig and a calcium ionophore, A23187, however, primed the BM-A cells to increase intracellular free calcium ion as well as normal B cells. From these results it is conceived that the lack of protein kinase C activation may be responsible for the failure of activation of BM-A cells.

Animals↗
PubMed1988

The protective effect of a new antiallergic agent, KP-136 on mast cell activation: a comparison with disodium cromoglycate.

The protective effects on mast cell activation were compared between a new antiallergic agent, KP-136 and disodium cromoglycate (DSCG), both of which inhibited the immunological degranulation of rat peritoneal mast cells. The IC50 was 0.03 micrograms/ml for KP-136 and 4.7 micrograms/ml for DSCG. KP-136 predominantly acted on the early stage of mast cell activation processes and inhibited the immunological increase in 45Ca uptake. KP-136 also inhibited A23187- and heat-induced degranulation and heat-induced hemolysis. In addition, KP-136 was effective on phospholipase A2-induced degranulation, although the compound did not directly affect the enzyme activity. In all tests for comparison, KP-136 and DSCG had similar profiles of action and the parallel experiments indicated that KP-136 was a more potent inhibitor of mast cell activation than DSCG, having a DSCG-like membrane stabilizing activity.

Animals↗
PubMed1980

A simple method for detecting cells producing antibodies of specific immunoglobulin classes in the chicken.

A simple plaque method for detecting cells producing antibodies of specific immunoglobulin class in the chicken is described. This method is based upon the inability of chicken antibody to activate guinea-pig complement. IgM- and IgG-specific plaque-forming cells in the spleen of chickens immunized with sheep red blood cells were detected using guinea-pig complement and rabbit anti-chicken-mu- or gamma-chain serum. The specificity of the immunoglobulin class of plaques was confirmed by the abolition of class-specific hemolytic plaques after treatment of the lymphoid cells with rabbit antisera specific for chicken heavy chains in the presence of guinea-pig complement. The method is very simple and rapid, and IgM and IgG specific plaques are reliably detected.

Animals↗
PubMed1980

Gel to liquid-crystalline phase transitions of lipids and membranes isolated from Escherichia coli cells.

Differential scanning calorimetry (DSC) was used to examine the relationship of the gel to liquid-crystalline phase transition of lipids to fatty acid composition with membrane lipids and spheroplast membranes isolated from cells of a wild strain and an unsaturated fatty acid auxotroph of Escherichia coli grown under various conditions. These lipids and membranes underwent thermotropic phase transitions at different temperatures depending on the thermal properties of their constituent fatty acids. The lipid phase transition occurred at higher temperatures in biomembranes than in extracted lipids. DSC thermograms of lipids synthesized by bacterial cells which were observed at a temperature scanning rate as slow as 0.3 K min-1 were characterized by a distinctly plain peak summit. Endothermic peaks given by samples derived from elaidic acid-enriched cells were relatively narrow and asymmetric. The discrepancy between the transition temperatures measured with extracted lipids and with membraneous fractions, and the shape of the endothermic peaks, are discussed.

Calorimetry, Differential Scanning↗
PubMed1980

The development of unusual B-cell functions in the testosterone-propionate-treated chicken.

Chickens were treated with 4 mg of testosterone propionate on the twelfth day of embryonic life. Bursal remnants of testosterone-treated chickens were very small in size and had very few or no bursal follicles: the lymphoid tissue was replaced substantially by fibrosis. Testosterone-treated chickens formed almost exclusively IgM antibodies to sheep red blood cells and influenza virus, whereas no IgM or IgG response to Brucella abortus or Salmonella pullorum, and no IgG response to sheep red blood cells was demonstrable. Surgical removal of bursal remnants of testosterone-treated chickens at hatching did not significantly affect IgM response to sheep red blood cells. These B-cell functions of testosterone-treated chickens were not improved by addition of T cells, as shown by adoptive cell transfer experiments. Thus, there appears to be an unusual type B-cell development which is independent of the bursa of Fabricius.

Animals↗
PubMed1980

The B-cell development independent of the bursa of Fabricius but dependent upon the thymus in chickens treated with testosterone propionate.

Spleen cells taken from chickens treated with testosterone propionate, surgically bursectomized and immunized, were treated with anti-bursa-cell antiserum in the presence of complement, and transferred together with the mixed antigens into immunodeficient chickens. The recipient chickens showed restored capacity for antibody response to sheep red blood cells. In contrast, adoptive immune responses by spleen cells from normal chickens were abolished by treating with anti-bursa-cell antiserum in the presence of complement. These findings indicate that antibody-forming cells in TP-treated chickens do not bear cell-surface antigens specific for bursa cells; Testosterone-treated chickens were thymectomized at 7 days of age and immunized with the mixed antigens; the chickens thus treated were not able to produce antibodies. Thymocytes and thymus-derived cells taken from normal chickens were transferred into the testosterone-treated and surgically thymectomized chickens; but the antibody responses were not restored, indicating that absence of antibody formation in testosterone-treated, thymectomized birds is not due to lack of T cells as such. This result was confirmed by using adoptive transfer of B cells taken from testosterone-treated chickens together with T cells.

Animals↗
PubMed1980

A T-cell subpopulation committed to help B cells for immune responses restricted to IgM type.

Immune responses againt bovine serum albumin by chicken were dependent upon thymus-derived cells. Thirty-five of seventy chickens that had been neonatally thymectomized and subsequently immunized with bovine serum albumin produced IgM antibodies, but not IgG antibodies, against the antigen. T cells (IgM-T cells) of such chickens were able to help B cells to produce IgM antibody responses but were not able to help them to switch IgM- to IgG-antibody responses. Helper activity of the IgM-T cells was much less susceptible to the cytotoxic effect of anti-thymus cell serum and complement than was that of normal T cells. The introduction of the IgM-T cells into normal chickens at the same time as the initiation of immunization of the chickens did not affect immune responses by them at all, indicating the absence of suppressor T cells in the IgM-T cell preparations. Injection of chicken thymus factor into immunodeficient chickens transplanted with normal B cells and IgM-T cells developed the capability to help B cells to switch IgM- to IgG-antibody responses. On the basis of these findings the authors propose the existence of helper T cells which are characterized by peripheralization in early periods of ontogeny, the possession of helper activity for only IgM-antibody responses, the lack of helper activity for the switch from IgM- to IgG-antibody responses and relative insusceptibility to the cytotoxic effect of anti-thymus cell serum and complement.

Animals↗
PubMed1980

A B-cell subpopulation relatively insusceptible to the cytotoxic effect of anti-bursa cell serum and partially defective in immune function.

Chicken B cells treated with diluted anti-bursa cell serum in the presence of complement were transferred together with normal T cells and sheep red blood cells into immunodeficient recipient chickens, and spleen cells taken from these were examined for the development of plaque-forming cells. The production of IgM-plaque-forming cells was considerably more resistant to the cytotoxic effect of the antiserum than that of IgG-plaque-forming cells. Cells producing IgM antibodies were also less susceptible to the cytotoxic effect of the antiserum and complement than were those producing IgG antibodies. Such differential susceptibility of development of IgM- and IgG- plaque-forming cells was observed only in chickens aged about 2 weeks or younger. These findings indicate the existence of a B-cell subpopulation which is relatively insusceptible to the cytotoxic effect of the antiserum and is incapable of switching from IgM- to IgG-immune responses. The B cells resistant to the cytotoxic effect of diluted anti-bursa cell serum and complement were more susceptible to X-irradiation than were normal B cells. Immune responses against sheep red blood cells by the B cells resistant to the cytotoxic effect were dependent upon the help of T cells.

Animals↗
PubMed1978

Relationship between bactericidal action of complement and fluidity of cellular membranes.

The mode of complement-mediated killing of Escherichia coli B cells grown at 25 and 42 degrees C and of E. coli K-12 UFAts cells grown in the presence of oleic and elaidic aicds was examined in relation to their membrane lipid compositions and the thermodynamic properties of membrane phospholipids. Phospholipids isolated from 25 degrees C-grown cells of strain B and from oleic acid-incorporated cells of strain K-12 UFAts had lower phase transition temperatures than did phospholipids from E. coli strain B grown at 42 degrees C or those from strain K-12 UFAts grown on elaidic acid. The rate of cellular susceptibility to complement action closely correlated with the liquid crystalline phase of phospholipids of cell membranes. These findings suggest that membrane fluidity is obligatory for the final expression of complement action.

Blood Bactericidal Activity↗
PubMed1978

The role of the thymus for maturation of transferred bursa cells into immunocompetent B cells in chickens treated with cyclophosphamide.

Chickens injected with cyclophosphamide and X-ray irradiated in the newly hatched period were immunized with a mixture of sheep red blood cells, Brucella abortus and Salmonella pullorum at 4, 5 and 6 weeks of age, and were examined for serum antibody titres, serum immunoglobulin concentration and bursal and splenic structures at 7 weeks of age. The neonatal treatments suppressed completely or almost completely antibody responses, immunoglobulin production and formation of bursal follicles and splenic germinal centres. The transplantation of bursa cells into the chickens immunologically impaired by the treatments restored these functions and structures. In contrast, the transfer of bursa cells into chickens thymectomized, cyclophosphamide-treated and X-ray irradiated did not result in efficient restoration of the bursa-dependent immune system; 10-day-old bursa cells hardly restore the system, although 4-week-old bursa cells did so slightly. The chickens thymectomized, cyclophosphamide-treated, X-ray irradiated and repopulated with 10-day-old bursa cells were examined for the existence of functional B cells with the use of a syngeneic cell transfer system. The experiments verified that immunocompetent B cells had not developed in the chickens thus treated.

Animals↗