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Biomedical subjects

K Miyabe

Publications and source records attributed to K Miyabe.

At least 19 recordsLinked to original sources
PubMed2001

Analysis of the surface diffusion of alkylbenzenes and p-alkylphenols in reversed-phase liquid chromatography using the surface-restricted molecular diffusion model.

Surface diffusion of alkylbenzene and p-alkylphenol derivatives was measured in reversed-phase liquid chromatography on a C18-silica column with a methanol/water mixture (70/30, v/v) as the mobile phase. They were analyzed on the basis of the restricted molecular diffusion model for surface diffusion. The temperature dependence of the surface diffusion coefficient (Ds) arises probably from that of molecular diffusivity, suggesting a correlation between surface and molecular diffusion. Other correlations were also observed: (1) an enthalpy-entropy compensation of the retention equilibrium constant, (2) a linear free energy relationship between the retention and surface diffusion, and (3) a linear correlation between the restriction energy of surface diffusion and the isosteric heat of adsorption. The physical meaning of parameters involved in the surface-restricted molecular diffusion model is discussed on the basis of these results. A practical and convenient procedure for the estimation of Ds is also suggested. This study demonstrates how surface diffusion phenomena can be accounted for on the basis of the correlation between surface and molecular diffusion.

Journal Article↗
PubMed2001

Retention and mass transfer characteristics in reversed-phase liquid chromatography using a tetrahydrofuran-water solution as the mobile phase.

The characteristics of the retention and the mass transfer kinetics in reversed-phase liquid chromatography (RPLC) were measured on a system consisting of a C18-silica gel and a tetrahydrofuran-water (50:50, v/v) solution. These parameters were derived from the first and the second moments of the elution peaks, respectively. Further information on the thermodynamic properties of this system was derived from the temperature dependence of these moments. Some correlations previously established were confirmed for this system, namely, an enthalpy-entropy compensation for both retention and surface diffusion and a linear free-energy relationship. These results are compared with those observed in other similar systems using methanol-water (70:30, v/v) and acetonitnile-water (70:30, v/v) solutions. The contribution of surface diffusion to intraparticle diffusion in C18-silica gel particles was shown to be important. The analysis of the thermodynamic properties of surface diffusion suggests that, in these three RPLC systems, its activation energy is lower than the isosteric heat of adsorption. The nature and the extent of the influence of the mobile phase composition on the parameters describing the retention and the mass transfer kinetics are different but the chromatographic mechanisms involved in RPLC systems appear similar, irrespective of the nature of the organic modifier in the mobile phase.

Chromatography, High Pressure Liquid↗
PubMed2000

Dendritic cell-like immunoreactivity in the glomerulus of the olfactory bulb and olfactory nerves of mice.

Dendritic cell-like immunoreactivity was examined in the mouse brain. The glomerulus of the olfactory bulb and the olfactory nerves were stained by antibodies against the dendritic cells, NLDC-145 and MIDC-8, while these structures were not stained by antibodies against microglia or macrophages, F4/80, Mac1 or CD45. Immunoelectron microscopy showed that the immunoreaction for NLDC-145 was localized to the sheath and presynaptic terminals of the olfactory nerves. These findings suggest that the sheath and presynaptic terminals of the primary olfactory nerves have some degree of the antigenicity in common with dendritic cells.

Animals↗
PubMed2000

A kinetic study of mass transfer in reversed-phase liquid chromatography on a C18-silica gel

The characteristic features of mass-transfer kinetics in a reversed-phase (RP) column packed with a C18-silica were studied. The relevant information on phase equilibrium thermodynamics and mass-transfer kinetics was obtained by frontal analysis and the pulse method, respectively. The equilibrium isotherm was accounted for by the simple Langmuir model. The ratio of the axial dispersion coefficient to the mobile-phase flow velocity increased almost linearly with increasing solute concentration. Similarly, the mass-transfer rate coefficient (km) showed a linear dependence on the solute concentration. The positive concentration dependence of km resulted from that of the surface diffusion coefficient, which was interpreted with the chemical potential driving force model. The contribution of axial dispersion to band broadening was predominant in the RP column packed with the medium-size packing material used (particle diameter, 12 microns) whereas that of the kinetics of adsorption/desorption was negligibly small. The results of this study demonstrate how an analysis of the dependence of the mass-transfer kinetics on the flow velocity and the solute concentration allows a better understanding of this kinetics.

Journal Article↗
PubMed2000

Influence of the column radial heterogeneity on the determination of single-component isotherms by the elution by characteristic point method.

The influence of the column radial heterogeneity on the determination of equilibrium isotherm data by the elution by characteristic point (ECP) method is studied using nondimensional numerical calculations and taking into account typical radial distributions of the mobile phase flow velocity and the column efficiency across a column. Overloaded elution peaks were calculated with the equilibrium-dispersive model as a function of four dimensionless parameters, the number of theoretical plates at the center of the column, the Langmuir equilibrium constant, the retention and the loading factors. The influence of the mass transfer resistances and the radial heterogeneity of the column on the ECP data was analyzed by comparing the true isotherm and the one estimated from the diffuse profile of overloaded peaks. The results provide information on the accuracy of the ECP method. The error made increases with increasing degree of radial heterogeneity. This error can be corrected by using the results of the nondimensional numerical calculations, allowing a further extension of the applicability of the ECP method.

Chromatography↗
PubMed2000

Determination of the lumped mass transfer rate coefficient by frontal analysis.

The validity of measurements of the lumped mass transfer rate coefficient (km,L) is studied on the basis of experimental data acquired under Langmuir isotherm conditions, in reversed-phase liquid chromatography. Two different methods were used, the perturbation method and frontal analysis. Accurate values of km,L can be properly obtained by the perturbation method because, with this method, the chromatographic processes take place under locally linear isotherm conditions. Values of km,L can also be derived from the breakthrough curves obtained in frontal analysis. Because the contribution of axial dispersion to band broadening was larger than that of the mass transfer resistances, the apparent axial dispersion coefficient (Da) was first derived from the breakthrough curve by applying the equilibrium-dispersive model. Then, the value of km,L was calculated from Da. The values of km,L determined by the two methods were in close agreement in the range of nondimensional Langmuir equilibrium constants (r= 1/[1+KLC0]) between 0.32 and 0.85, irrespective of the mobile phase flow velocity. Thus, frontal analysis can be used for kinetic studies of the mass transfer in chromatographic columns.

Chromatography, Liquid↗
PubMed2000

Glycoprotein Ibalpha-bound thrombin functions as a serine protease to produce macromolecular activators of phagocytosis from platelets.

Production of macromolecular activators of phagocytosis from platelets (MAPPs) was observed when the lysate of fresh platelets was incubated with MAPP precursors and thrombin. An 800-Da MAPP activator (PMA-II) was obtained by Superdex peptide gel filtration of the lysate after thrombin treatment. The necessity of thrombin in MAPP production in fresh platelets was confirmed by the action of anti-thrombin monoclonal antibody or anti-thrombin III and heparin. To specify the thrombin receptor on which the thrombin forming PMA-II binds, the effects of thrombin-receptor-derived peptides and anti-thrombin receptor antibodies on MAPP production by stored platelets which have lost their thrombin content were investigated. DYYPEEDTEGD involved in glycoprotein Ibalpha and anti-glycoprotein Ibalpha antibody prevented stored platelets from producing MAPP. These observations suggest that thrombin bound to glycoprotein Ibalpha functions as a serine protease in MAPP formation.

Amino Acid Sequence↗
PubMed2000

Restricted diffusion model for surface diffusion in reversed-phase liquid chromatography

The analysis of experimental results in reversed-phase liquid chromatography (RPLC) allows further discussion of the restricted diffusion model of surface diffusion formulated on the basis of the absolute rate theory. Chromatographic data were acquired on different RPLC systems with two series of homologous compounds, several stationary phases having different alkyl ligand densities and ligands of various lengths, and methanol/water mobile phases of different compositions. The enthalpy-entropy compensation observed and the linear free energy relationships found for surface diffusion suggest that the surface diffusion mechanism remains probably the same in all RPLC conditions studied. Whereas the isosteric heat of adsorption approaches zero with decreasing retention, the activation energy of surface diffusion tends toward a finite limit and the surface diffusion coefficient tends toward a value near the corresponding molecular diffusivity. These results support the validity of the restricted diffusion model. The influence of different factors on the validity of this model (i.e., the activation energy and the frequency factor of surface diffusion, and the surface tortuosity) was also considered.

Journal Article↗
PubMed2000

Study on the accuracy of the elution by characteristic point method for the determination of single component isotherms.

The accuracy of the method of elution by characteristic point (ECP) used to determine single component isotherms was studied numerically. Overloaded elution peaks were calculated using the equilibrium-dispersive model of nonlinear chromatography while varying the four parameters, i.e., the number of theoretical plates, the dimensionless Langmuir equilibrium constant, the retention and the loading factor, involved in the fundamental equations of the problem. Single component isotherms were estimated by analyzing the diffuse profile of the elution peaks by the ECP method. Similar results were obtained with the transport-dispersive model. The comparison of these calculated isotherms with the initial Langmuir isotherms provided detailed information on the influence of the mass transfer resistances on the accuracy of the isotherms afforded by the ECP method. The systematic error made on the isotherms depends on the experimental conditions, described by the four parameters. It is expected that this error could be eliminated by correcting the influence of nonequilibrium in the column on the basis of results of the nondimensional calculations. The concentration range of the objective isotherm which can be determined by the ECP method can also be predicted by numerical calculations. The usefulness of the correction strategy and the prediction of the concentration range were experimentally demonstrated.

Chromatography↗
PubMed2000

Kinetic study of the mass transfer of bovine serum albumin in anion-exchange chromatography.

A kinetic study was made on the mass transfer phenomena of bovine serum albumin (BSA) in two different anion-exchange columns (Resource-Q and TSK-GEL-DEAE-5PW). The analysis of the concentration dependence of the lumped mass transfer rate coefficient (km,L) provided the information about the kinetics of the several mass transfer processes in the columns and the anion exchangers, i.e., the axial dispersion, the fluid-to-particle mass transfer, the intraparticle diffusion, and the adsorption/desorption. In the Resource-Q column, the intraparticle diffusion had a dominant contribution to the band broadening compared with those of the other processes. The surface diffusion coefficient (Ds) of BSA showed a positive concentration dependence, by which the linear dependence of km,L on the BSA concentration seemed to be interpreted. On the other hand, in the TSK-GEL-DEAE-5PW column, the contribution of the adsorption/desorption was also important and almost same as that due to the intraparticle diffusion. There are some differences between the intrinsic properties of the mass transfer kinetics inside the two anion exchangers. It was likely that the positive concentration dependence of Ds was explained by the heterogeneous surface model.

Chromatography, Ion Exchange↗
PubMed2000

Influence of the modification conditions of alkyl bonded ligands on the characteristics of reversed-phase liquid chromatography.

The parameters characterizing retention and the mass transfer mechanisms in reversed-phase liquid chromatography were derived from data acquired for a series of compounds on a silica gel bonded to alkyl ligands of various lengths and ligand densities. The adsorption equilibrium constant, the absolute value of the isosteric heat of adsorption, and the activation energy of surface diffusion increase while the surface diffusion coefficient decreases with increasing length of the alkyl chain and density of the C18 ligand. These results are consistent with increasing restriction of the mobility of an increasingly adsorbable molecule. There is a critical level of carbon content above which the four parameters just listed no longer change with increasing alkyl ligand density. This level is likely to depend on the sizes of the alkyl ligand and the sample molecule. Even at high densities of C18 chains, there may be a limitation in the contact area of the sample molecule and the alkyl ligand. The retention behavior on the stationary phases studied is explained by assuming that the sample molecules penetrate into the layer of alkyl ligands. Enthalpy-entropy compensation was demonstrated for surface diffusion. Its mechanism is probably similar on the different stationary phases studied, irrespective of the length and density of the bonded ligand.

Chromatography, Liquid↗
PubMed1999

Influence of column radial heterogeneity on peak fronting in linear chromatography.

Using numerical calculations of elution peak profiles, an explanation of the fronting behavior of elution peaks in linear chromatography was found in certain radial distributions of the mobile phase flow velocity and local bed efficiency. Fronting peaks are observed only if the flow velocity is higher in the wall region than in the center part of the column and the local efficiency is lower near the wall than in the center. By contrast, tailing or symmetrical peaks are observed if only the flow velocity or the local efficiency are radially heterogeneous. The degree of peak fronting increases with increasing amplitude of the radial distributions. The influence of the radial heterogeneity of the flow velocity on the degree of peak fronting is more severe for high than for low efficiency columns. An equation is suggested to correlate peak fronting behavior for columns of different efficiencies and a procedure proposed for the estimation of the radial distributions of the flow velocity and the local efficiency by analyzing some characteristics of asymmetric peaks.

Chromatography↗
PubMed1999

Kinetic study of the mass transfer of S-Tröger's base in the system cellulose triacetate and ethanol.

A recent study of the mass transfer kinetics of (-)- or S-Tröger's base (TB) between ethanol and microcrystalline cellulose triacetate (CTA) allows an analysis of the concentration dependence of the mass transfer rate coefficient (k(m)). S-TB elutes before R-TB. The retention time of the both compounds decreases with increasing temperature. In this study, experimental data measured between 30 and 50 degrees C were analyzed to provide information on the kinetics of several mass transfer processes which take place in the chromatographic column, i.e., axial and intraparticle dispersion, the fluid-to-particle mass transfer, and the kinetics of adsorption/desorption at the actual adsorption sites. Intraparticle diffusion has the dominant contribution to band broadening at high flow-rates. Both intraparticle diffusivity and the surface diffusion coefficient exhibit a small concentration dependence. The positive dependence of k(m) on the concentration of S-TB seems to result from the properties of the adsorption/desorption kinetics and can be interpreted by considering the phase equilibrium properties. A quantitative analysis of the activation energy of the mass transfer kinetics of S-TB in the CTA column was also attempted.

Cellulose↗
PubMed1993

[Appropriate administration of granulocyte colony stimulating factor for malignant lymphoma of the head and neck].

The effects of granulocyte colony stimulating factor (G-CSF) were evaluated in 9 patients with malignant lymphoma of the head and neck. The effects of 31 cycles of cytotoxic chemotherapy were treated with G-CSF. G-CSF was given by one of the following three routes: 1) administration before or with cytotoxic chemotherapy, 2) administration after cytotoxic chemotherapy with leukocyte counts of more than 2000/mm3, and 3) administration after leukocyte counts had dropped to less than 2000/mm3. The first group consisted of one cycle of CHOP therapy and 2 cycles of VAMA therapy. The second group consisted of 10 cycles of CHOP therapy. The third group consisted of 13 cycles of CHOP therapy and 5 cycles of VAMA therapy. Leukocyte nadirs occurred on around day 14 for CHOP therapy and around day 21 for VAMA therapy without G-CSF treatment. In the first group, the leukocyte nadirs occurred earlier with G-CSF treatment. Additional G-CSF treatments were given in two of the three cycles. In the second group, the leukocyte counts did not drop below 2000/mm3 in three of the ten cycles. Additional G-CSF treatments were given in five of the remaining seven cycles. The two other cycles went without additional treatment. The mean volume of G-CSF was 305 +/- 86 micrograms. In the third group, the leukocyte counts increased to more than 2000/mm3 immediately after G-CSF administration in CHOP therapy. The mean volume was 227 +/- 78 micrograms, significantly less than that of the second group. The leukocyte counts also exceeded 2000/mm3 3-5 days after G-CSF administration in 5 cycles of VAMA therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Antineoplastic Combined Chemotherapy Protocols↗