Biomedical subjects

Y Okahata

Publications and source records attributed to Y Okahata.

39 records · Page 3Linked to original sources

PubMed1990

Synthetic chemoreceptive membranes. Sensing bitter or odorous substances on a synthetic lipid multibilayer film by using quartz-crystal microbalances and electric responses.

Specific adsorptions of bitter or odorous substances on a synthetic lipid multibilayer matrix (2C18N+2C1/PSS-) were detected by observing frequency changes of a multibilayer-coated quartz-crystal microbalance (QCM). Partition coefficient (P) and diffusion constants (D) of these substances in the lipid matrix could be obtained quantitatively by using the QCM method. There were good correlations between partition coefficients of various bitter or odor substances to the synthetic multibilayer film on the QCM and the intensity of bitter tastes or olfactory receptions in humans: the stronger the intensity of a bitter substance or odorant, the greater the adsorption on the lipid matrix. This indicates that the lipid-coated QCM acts as a sensitive and selective sensor for bitter taste and odor. Electric responses (changes of membrane potential and membrane resistance) of the 2C18N+2C1/PSS-film occurred consecutively by the adsorption of these substances. The bitter or odor substance showing the stronger intensity induced membrane potential change in lower concentrations. It was found that bitter substances having sterically bulky molecular structures adsorb on the surface of the lipid matrix, and the phase-boundary potential of the membrane is thereby changed. On the contrary, odor substances with relatively small or slender structures can penetrate into the lipid matrix and cause reduction of the membrane resistance (the increase of ion permeability). The selective adsorption behavior of bitter and odor substances by molecular shapes was confirmed by adsorption studies of simple C9-10 hydrophobic alcohols having various molecular structures.

Adsorption↗

PubMedDate not supplied

Novel instrumentation monitoring in situ platelet adhesivity with a quartz crystal microbalance.

The quartz crystal microbalance (QCM) in a solution is capable of sensing an extremely small mass change in the nanogram range. In this article, the authors attempted to apply QCM to in situ continuous monitoring of platelet adhesion in plasma. The instrumentation consisted of a piezoelectric quartz crystal vacuum-deposited with gold and connected to two electrodes, an oscillation circuit, a frequency counter, and a DC source (5 V), coupled with a personal computer, a television monitor, and a printer. The authors noted resonant frequency shifts to determine weight increase upon cell adhesion. A QCM sensor, with the sensitivity of 1 ng/Hz, was placed horizontally in platelet poor plasma. The authors did not observe any measurable frequency shift upon adding a suspension of non-adherent cells, such as red blood cells and prostaglandin I2-sensitized platelets, indicating that QCM does not count the increase in the mass of cells that simply settled on the quartz. They did observe, however, a time-dependent frequency shift upon addition of platelet rich plasma. Coupled with visual determination of numbers of adherent platelets and their morphology under scanning electron microscopy, they found that the magnitude of shift and its time dependence seem to correlate not only numbers of adherent platelets, but to their spreading state, indicating that QCM detects only the weight at the focal contact region of adherent cells. This suggested that the former contributes to the early phase of the frequency shift, and the latter contributes to a shift change after a longer period of incubation.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMedDate not supplied

Controlled release from a large capsule membrane corked with phosphatidylethanolamine bilayers: effect of temperature, pH and concentration of Ca2+ ions.

Permeations of a fluorescent probe entrapped in the inner aqueous phase of a large nylon capsule membrane corked with phosphatidylethanolamine bilayers were reversibly controlled by (i) the phase transition of bilayers, (ii) the ambient pH change, and (iii) the addition of Ca2+/EDTA from outside. Their signal-receptive permeation control could be reproduced repeatedly without damaging corking bilayers, in contrast to that of liposomal membranes.

Calcium↗