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Biomedical subjects

A Ikai

Publications and source records attributed to A Ikai.

At least 37 records · Page 2Linked to original sources
PubMed1996

Neurite-promoting effect of alpha 2-macroglobulin in rat cerebral cortex is mainly associated with alpha 2-macroglobulin receptor.

It has been reported that alpha 2-macroglobulin (alpha 2 M), known as a plasma protease inhibitor, promotes neurite outgrowth of cultured neurons from rat cerebral cortex. The neurons dissociated from 17-day embryonic (E17) rat cerebral cortex were cultured in the medium containing methylamine-modified alpha 2M labeled with fluorescein isothiocyanate (MA- alpha 2 M-FITC). The modified alpha 2 M was taken up by neurons and localized mainly at the base of neurites. The fluorescence intensity of internalized MA- alpha 2 M-FITC in the cell was correlated to the degree of neurites extension. An immunocytochemical study using anti-alpha 2 M receptor (alpha 2 MR) polyclonal antibody showed that the neurons cultured for a longer period were stained weaker than those cultured for a shorter period. Many alpha 2 MRs were expressed when the neurons were likely to be extending the neurites well. From the developmental study of rat cerebrum, the expression of alpha 2 MR reached a maximum at postnatal 2 days (P2) when the neurons started to exhibit active neurite extension. These observations led us to conclude that neurite promoting effect of alpha 2 M acts through alpha 2 M-alpha 2MR binding and/or the following uptake of alpha 2 M.

Animals↗
PubMed1996

Mechanical unfolding of alpha2-macroglobulin molecules with atomic force microscope.

alpha2-Macroglobulin was derivatized with a sulfhydryl cross-linker and sandwiched between a mica substrate and a silicon nitride tip, both coated with gold, of an atomic force microscope and force curve measurement was carried out. An extensive downward deflection of the cantilever was observed in the retracting realm of the curve, when and only when the substrate was covered with the derivatized protein. The result was interpreted in terms of the mechanical stretching and unfolding of a single or a few protein molecules.

Cross-Linking Reagents↗
PubMed1995

Receptor-linked antigen delivery system. Importance of autologous alpha 2-macroglobulin in the development of peptide vaccine.

We have hijacked a process of the receptor-mediated endocytosis to transport peptide antigens into antigen presenting cells (APCs) for the purpose of increasing the level of antigen presentation (named Receptor-Linked Antigen Delivery System (R-LADS)). By coupling an endogenous plasma proteinase inhibitor alpha 2-macroglobulin (alpha 2M) to a synthetic peptide having a partial sequence of HIV-1 envelope protein, alpha 2M was made to carry the peptide into APCs as a part of the normal alpha 2M cycle, which resulted in an increased production of specific antibodies against the peptide (Mitsuda, S., Nakagawa, T., Osada, T., Shimamoto, T., Nakazato, H. and Ikai, A. (1993) Biochem. Biophys. Res. Commun. 194, 1155-1160). We demonstrate here that this procedure becomes a more efficient tool for antibody production when autologous transporter protein was used. By using murine alpha 2M (m alpha 2M) instead of heterologous human alpha 2M (h alpha 2M) when mice were experimental animals, we were able to dramatically enhance the production level of anti-HIV-1 peptide antibodies and shorten the period which is needed for antibody production. We aim to develop effective peptide vaccines by further improving this system.

3T3 Cells↗
PubMed1995

Dangerous angles and depths for middle ear and middle cranial fossa injury during arthroscopy of the temporomandibular joint.

PURPOSE: Several reports have suggested a risk of injury to the middle cranial fossa and middle ear during arthroscopic procedures in the superior joint space of the temporomandibular joint (TMJ). However, there has been no anatomic study of directions and distances of the TMJ from the posterior portal in relation to the risk of mandibular fossa injury. In this study, the angles and depths at which the risk is greatest for injury to the deepest point of the mandibular fossa (DP) and to the middle ear during arthroscopy were analyzed. MATERIALS AND METHODS: Three-dimensional measurements of 96 mandibular fossae in 48 dry skulls were made. RESULTS: It was found that the distance from the lateral rim of the fossa to DP and Hugier's canal was 9.50 +/- 2.07 mm and 17.04 +/- 3.09 mm, respectively. The most dangerous angle for DP injury in the Frankfort horizontal plane (FH plane) was an inclination of the instrument base of -8 degrees dorsad and 17 and 19 degrees caudad in the frontal plane. The most dangerous angle for Hugier's canal injury was a tilting of the instrument base of 15 degrees ventrad in the FH plane and -2 degrees craniad in the frontal plane. However, these values showed a wide range. CONCLUSION: It was concluded that great care must be exercised in manipulation of instruments near the DP and Hugier's canal to avoid injury to the middle ear or penetration into the middle cranial fossa.

Adolescent↗
PubMed1995

Method for immobilizing microbial cells on gel surface for dynamic AFM studies.

The processes of cell growth and budding of the yeast cells Saccharomyces cerevisiae, which were gently immobilized on 3% agar and submerged in culture medium, were successfully imaged with an atomic force microscope for 6-7 h. Similar experiments on chemically fixed cells did not detect any appreciable change in their appearance except in a few scannings at the very beginning, indicating that the dissolution of agar and/or scraping of its surface by the scanning tip, if any, did not significantly interfere with the images taken thereafter. The increment in the height of many of the untreated cells, accompanied by their lateral enlargement, was taken as an indication of successful imaging of the growth process of yeast cells, together with an image of a growing daughter cell attached to its mother cell.

Agar↗
PubMed1995

A method for anchoring round shaped cells for atomic force microscope imaging.

More and more researchers are interested in imaging living (Henderson, 1994) or fixed cells in their natural environment using the atomic force microscope (AFM). However, the AFM tip interacts strongly with the sample, and its z range freedom is limited to a few micrometers. This means that the cells to be imaged have to be strongly attached to the substrate, and imaging is restricted to cells having a flattened shape. Here we propose a simple and inexpensive solution to overcome these limitations. The method we propose is trapping living round shaped cells in a Millipore filter with a pore size comparable to the dimensions of the cell. The highest part of some of the blocked cells protrude through the holes of the filter and can this way be easily observed using the AFM without detachment.

Micropore Filters↗
PubMed1994

Small-angle scattering study of alpha 1 inhibitor III from rat blood plasma.

The alpha 1 proteinase inhibitor III from rat blood plasma, homologous to the alpha 2-macroglobulin family of proteins, has been studied in solution using small-angle scattering of X-rays and of neutrons: the radius of gyration, Rg, was found to be 4.5 nm, and the largest distance within the molecule, Dmax = 14 nm. When the inhibitor reacts with chymotrypsin or methylamine, the resulting derivatives yield slightly higher Rg-values, 4.7 and 4.85 nm, respectively. The data of the native protein are consistent with a model, the projection of which resembles the letter V and which is formed by the two identical halves of an elliptic cylinder with semi-axes of 2.1 and 5.5 nm and a length of 11 nm. This elliptic cylinder model also explained the scattering from the monomeric complement proteins C3 and C4, as well as that from the monomers of the dimeric and tetrameric alpha 2-macroglobulin family of proteins (Osterberg, R., et al. (1991), Biochemistry 30, 7873-7878). Due to the conformational change occurring when the thiol ester bond is split, the cleft in the V-form seems to be closed; and as a result, the models of the chymotrypsin and methylamine derivatives are more compact than that of the native protein.

Acute-Phase Proteins↗
PubMed1994

Monoclonal antibody (VOM2) specific for the luminal surface of the rat vomeronasal sensory epithelium.

Monoclonal antibodies were raised and selected for reactivity with the luminal surface of the rat vomeronasal organ. Among the monoclonal antibodies generated, the one named VOM2 showed specific immunoreactivity within the luminal surface of the rat vomeronasal sensory epithelium. The VOM2 antigen appeared weakly on the luminal surface at postnatal day 14 (P14). After P21, VOM2 immunoreactivity as strong as that in the adult vomeronasal organ was observed. Immunofluorescence staining using VOM2 antibody showed no reactivity on the luminal surface of the adult mouse or hamster vomeronasal organ. An immunoblotting analysis showed that the VOM2 antigen was a protein with a molecular weight of 24,500.

Animals↗
PubMed1994

The kinetics of conformational changes of alpha 2-macroglobulin determined by time resolved X-ray solution scattering.

The rate of gross conformational change of alpha 2-macroglobulin (alpha 2M) during its proteinase trapping was directly determined for the first time using time-resolved X-ray solution scattering. Decrease of radius of gyration was observed under pseudo-first-order conditions with excess proteinases, which exhibited a monophasic time-course. The rate constants were 0.5 +/- 0.1 s-1 and 0.8 +/- 0.2 s-1 for the reaction with chymotrypsin and trypsin, respectively. There was no concentration dependence of the observed rate constants. Therefore, the rate-limiting step of the gross conformational change was not the bimolecular encounter reaction between alpha 2M and proteinases, which requires a new proposal of pre-trapping of proteinases before the gross conformational change.

Chymotrypsin↗
PubMed1994

Kinetic study on myoglobin refolding monitored by five optical probe stopped-flow methods.

The refolding kinetics of horse cyanometmyoglobin induced by concentration jump of urea was investigated by five optical probe stopped-flow methods: absorption at 422 nm, tryptophyl fluorescence at around 340 nm, circular dichroism (CD) at 222 nm, CD at 260 nm, and CD at 422 nm. In the refolding process, we detected three phases with rate constants of > 1 x 10(2) s-1, (4.5-9.3) s-1, and (2-5) x 10(-3) s-1. In the fastest phase, a substantial amount of secondary structure (approximately 40%) is formed within the dead time of the CD stopped-flow apparatus (10.7 ms). The kinetic intermediate populated in the fastest phase is shown to capture a hemindicyanide, suggesting that a "heme pocket precursor" recognized by hemindicyanide must be constructed within the dead time. In the middle phase, most of secondary and tertiary structures, especially around the captured hemindicyanide, have been constructed. In the slowest phase, we detected a minor structural rearrangement accompanying the ligand-exchange reaction in the fifth coordination of ferric iron. We present a possible model for the refolding process of myoglobin in the presence of the heme group.

Animals↗