Biomedical subjects

H Maeda

Publications and source records attributed to H Maeda.

At least 1,351 records · Page 75Linked to original sources

PubMed1980

Effects of dielectric saturation on planar electric double layers in salt solutions.

The effects of dielectric saturation on planar electric double layers in salt solutions are examined by solving the Poisson-Boltzmann equation analytically where the dielectric constant is given as a function of the electric displacement. The activity and the distribution of small ions, the surface potential and the Donnan potential are calculated. The salt exclusion parameter and the Donnan potential decrease while the surface potential increases as a result of the dielectric saturation. The electrostatic entropy is affected considerably by the dielectric saturation while the electrostatic energy is little influenced. Generally, the effects of dielectric saturation on the distribution of small ions and the thermodynamic properties are enhanced by the addition of salt.

Journal Article↗

PubMed1980

Reevaluation of the reaction of formaldehyde at low concentration with amino acids.

Many studies have been reported on the reaction of formaldehyde (FA) with amino acids or proteins, and FA is assumed to react with the alpha-amino group as well as some of the side chain groups. In most of these investigations a large excess of FA relative to amino acids or proteins was employed. In the present study, however, we carried out the reaction with a smaller excess of FA in order to clarify the reactivity, firstly with the alpha-amino groups, and secondly with specific side chain groups. No evidence for so-called Schiff base (-N = CH2) formation was obtained in the reaction with the alpha-amino groups, but the formation of an acid-labile N-hydroxymethyl compound as a major product was suggested by NMR and IR at greater than pH 9.2. There was no indication, however, of the presence of such a product below pH 9.2, and the amount of N-hydroxymethyl product increased in parallel with the reaction pH. The higher the reaction pH (greater than or equal to 9.2), the greater the consumption of FA, up to 2 mol/mol Ala. In addition, the larger the excess of FA, the smaller the amount of free amino group remaining (at pH 9.7). In the assignment of IR spectra, discrete absorption bands of the alpha-carboxyl group of Ala were observed, which reflected ionization states of the alpha-amino group, and these were utilized for analysis of the reaction mechanism. Furthermore, among amino acids with side chain groups, His, Trp, and Arg showed high reactivity and Asn showed moderate reactivity. The products were relatively stable and were purified and subjected to instrumental analyses. Sixteen other amino acids including Tyr and Lys did not yield stable products. The products from Arg were unique because of the non-involvement of the amino group, and were reversibly converted to the original Arg upon acid hydrolysis. The products from His, Trp and Asn all involved amino or amide nitrogen forming cyclic ring structures with methylene derived from FA. The chemical structures of these products were determined on the basis of elemental analyses, MS and NMR.

Amino Acids↗

PubMed1980

Subcellular action of Neocarzinostatin. Intracellular incorporation, DNA breakdown and cytotoxicity.

The subcellular site of action of a proteinaceous antitumor antibiotic neocarzinostatin (NCS) was studied using normal human lymphocytes, Epstein-Barr virus transformed lymphoblastoid cells, osmotically burst lymphoblastoid cells, and colicin E1 plasmid DNA. The rate of DNA strand break in these different types of DNA was found to be in the following order: Colicin DNA > burst cell DNA > lymphoblastoid cell DNA > normal lymphocyte DNA. Furthermore, fluorescence microscopy revealed that lymphoblastoid cells incorporated more fluorescein isothiocyanate labeled NCS than normal cells. High uptake of NCS in lymphoblastoid cells coincided with a high killing rate; low uptake of NCS in lymphocytes resulted in very little cell killing. Uptake velocity using fluorescein diacetate (FDA) also showed that the lymphoblastoid cells exhibited a higher uptake of FDA coinciding with a higher killing rate. The cell killing activity of NCS appears to be closely associated with the rate of intracellular uptake of NCS and subsequent direct degradation of DNA by the drug. This notion is reinforced by the reported finding that the dose required for DNA strand scission is only about 1/100 of that for the inhibition of cap formation. Thus DNA strand scission, rather than the cell membrane, appears to be the primary target of NCS. Enhanced incorporation of many substances is commonly observed upon transformation of cells by viruses, and our present results may provide an important clue toward the explanation of the selective toxicity toward tumor cells of NCS.

Antibiotics, Antineoplastic↗

PubMed1980

A new lysozyme assay based on fluorescence polarization or fluorescence intensity utilizing a fluorescent peptidoglycan substrate.

A new sensitive, rapid and simple method for lysozyme assay is described which is based on either fluorescence polarization or fluorescence intensity using fluorescein-labeled peptidoglycan as a substrate. The peptidoglycan was obtained from Micrococcus lysodeikticus after extensive digestion with Pronase and washing with Triton X-100 followed by various solvents. Subsequently, it was labeled with fluorescein isothiocyanate (FITC) at the amino group of the peptide. When the FITC-labeled substrate was subjected to lysozyme digestion, an increase of fluorescence intensity or a decrease of fluorescence polarization value (P value) was apparent in five minutes at a lysozyme concentrations as low as 0.1 or 0.01 micrograms/ml, respectively. The effect of other hydrolytic enzymes including alpha-mannosidase, proteases and RNase on the P value was found to be negligible. The measured values represented the specificity and dose of lysozyme added. Apparent Vmax and Km values for two different lysozymes, chicken egg white and human, could be determined by this method.

Amino Acids↗

PubMed1980

HLA-DRw3 in juvenile onset diabetes mellitus in Chinese.

Thirty-nine juvenile onset diabetes mellitus (JOD) patients and 57 healthy Chinese were HLA-typed in Taiwan. The incidence of HLA-DRw3 was significantly increased in patients when compared with the control group (R.R. = 5.8, P = 0.0027). The frequencies of HLA-B17, which showed linkage disequilibrium with DRw3, and Bw54 were increased in patients, but these increases were not significant because of the small number tested. The DR antigen associated with JOD was the same among Chinese and Caucasians, which suggested that at least one of the susceptibility genes to JOD would be commonly in linkage disequilibrium with DRw3 in the two populations.

Adult↗

PubMed1980

Human IgE, IgG and IgE antibody synthesis in vitro.

Human IgE biosynthesis in vitro was studied by co-culturing T and B cells from atopic patients and normal controls in the presence of 10 microliter/ml pokeweed mitogen for 7 days. IgE and anti-mite IgE ab in the culture media significantly correlated with those in plasma. Normal T cells suppressed in vitro production of IgE and IgE ab significantly more than did atopic T cells but no difference was found in IgG production. The culture of B cells alone (T-depleted fraction) produced IgE equally as well as the co-culture of T and B cells. Anti-mite IgE ab was also produced by B cells alone from mite-sensitive patients. However, IgE biosynthesis in vitro was not consistently affected by pokeweed mitogen. The results suggest a deficiency of the T suppressor system in atopy and the existence of T-independent IgE-producing cells.

Adult↗

PubMed1980