Biomedical subjects

Hiroshi Hamana

Publications and source records attributed to Hiroshi Hamana.

4 recordsLinked to original sources

PubMed2005

Application of polymaleimidostyrene as a convenient immobilization reagent of enzyme in biosensor.

Sulfhydryl groups of glucose oxidase (GOD) were reacted with maleimide groups of polymaleimidostyrene (PMS) which was coated onto the porous carbon sheet, and the carbon sheet immobilized by GOD was combined with an oxygen electrode to fabricate a glucose sensor. The activity of thiolated GOD immobilized to PMS is much larger than that of native GOD immobilized to PMS. The good linear relationship of glucose and oxygen current response was obtained in a concentration range from 0.1 to 2 mM and upper limit of linear range was found to be 3.0 mM. The immobilized GOD activity is highly dependent on pH at immobilization and the maximum activity was obtained at pH 5.5, probably because the SH groups of GOD that are indispensable for generation of enzyme activity is not exposed at this pH. It was found that PMS is very effective reagent to immobilize enzyme strongly via covalent bond, because high density of maleimide groups of PMS can catch not only exposed SH groups but also buried SH groups.

Biosensing Techniques↗

PubMed2004

Oligomer preparation from hexane by radical polyaddition with bis(alpha-trifluoromethyl-beta,beta-difluorovinyl) terephthalate.

Polymer preparation from hexane as a starting material by radical polyaddition with bis(alpha-trifluoromethyl-beta,beta-difluorovinyl) terephthalate [CF(2)=C(CF(3))OCOC(6)H(4)COO-C(CF(3))=CF(2)] was investigated to afford polymers bearing a molecular weight of as high as 5.5 x 10(3), and the polyaddition mechanism including 1,5-radical shift mechanism was proposed.

Journal Article↗

PubMed2004

Sialyl Lewis X-carboxymethylpullulan conjugate: a novel homing device to spleen and lymph nodes.

We have previously found that carboxymethylpullulan (CMPul) conjugated with sialyl Lewis X (Neu5Acalpha2-3Galbeta1-4(Fucalpha1-3)GlcNAc-, 2-3SLex) preferentially accumulates in the lymph nodes and spleen. In the present study, we investigated the structural requirements of the 2-3SLex moiety for this accumulation using rats. Radiolabeled CMPul conjugates with various degrees of substitution (d.s.) of the 2-3SLex moiety were intravenously administered to rats, and their tissue distributions were monitored by radioactivity. When the d.s. was more than 0.5, preferential accumulation in the lymph nodes as well as the spleen was observed. However, when the d.s. was 0.025, little effect of the 2-3SLex moiety was noted. Changes in the carbohydrate structure of 2-3SLex, i.e., a change to alpha2-6-linked sialic acid (Neu5Acalpha2-6Galbeta1-4(Fucalpha1-3)GlcNAc-, 2-6SLex) or an elimination of the fucose (Neu5Acalpha2-3Galbeta1-4GlcNAc-, sialyl N-acethyllactosamine (SLN)), also made the 2-3SLex moiety ineffective. Furthermore, Microautoradiography analyses revealed that 2-3SLex-CMPul was incorporated by particular subsets of macrophages in these tissues, and that CMPul and SLN-CMPul were also located in the same cells to a lesser extent. 2-3SLex-CMPul may be able to serve as a novel drug delivery carrier to target drugs to the peripheral lymphoid tissues.

Animals↗

PubMed2003

Sensitivity-dependent hierarchical receptor codes for odors.

In order to comprehend the strategy of odor encoding by odorant receptors, we isolated 2740 mouse receptor neurons from four olfactory epithelial zones and classified them in terms of their sensitivities and tuning specificities to a chiral pair of odorants, S(+)-carvone (caraway-like odor) and R(-)-carvone (spearmint-like odor). Our approach revealed that the majority of receptors at the lowest effective stimulus concentration represented the principal odor qualities characteristic of each enantiomer by means of the principal odor qualities of the odorants for which the receptors were most sensitive. The chiral-non-discriminating receptors were newly recruited 3.7 times of R(-)-carvone-sensitive receptors and totally became 2.8 times (39/14) of R(-)carvone-sensitive receptors in the subpopulations when the stimulus concentration was increased 10-fold [corrected]. More than 80% of the responsive receptors (an estimated 70 +/- alpha types) exhibited overlapping sensitivities between the enantiomers. The signals from the non-discriminating receptors may be reduced to decode the characteristic odor identity for R(-)-carvone in the brain over an adequate range of stimulus strengths. The information processing of odors appears to involve the selective weighting of the signals from the most sensitive receptors. An analysis of the overall receptor codes to carvones indicated that the system employs hierarchical receptor codes: principal odor qualities are encoded by the most sensitive receptors and lower-ranked odor qualities by less sensitive receptors.

Animals↗