Biomedical subjects

M J Ueda

Publications and source records attributed to M J Ueda.

3 recordsLinked to original sources

PubMed1981

Phagocytosis by macrophages. I. Kinetics of adhesion between particles and phagocytes.

A quantitative method for measuring the initial rate of adhesion of foreign particles to mouse peritoneal macrophages, using protein-coated paraffin oil particles, is described. It was performed to measure the rate of adhesion, which is the first step of phagocytosis, separately from the other phagocytic activities. Kinetic studies showed that the cell-substrate adhesion was a Michaelis-Menten type reaction, which has two rate indices, Km and V. The effects of various reagents on the adhesion rate were analysed. KCN and NaN3 change the rate by affecting V, while the changes in the rate brought about by chlorpromazine and filipin are due to their effect on the Km. Cytochalasin B decreased the adhesion rate, but colchicine did not. The initial rate of adhesion decreased with decreasing temperature. As Arrhenius plot of the initial rate showed a break at 30 degrees C, and gave an activation enthalpy of 14.8 kcal for the process at the physiological temperature. No characteristic change in membrane fluidity was found at 30 degrees C using electron spin resonance spectroscopy.

Animals↗

PubMed1981

Phagocytosis by macrophages. II. The dissociation of the attachment and ingestion steps.

The phagocytic process of mouse peritoneal macrophages was dissociated, using bovine serum albumin (BSA)-coated particles containing spin-labelled cholestanone, into 2 steps: attachment of particles to the cell surface and ingestion of the particles into the cytoplasm. The number of particles was estimated from electron spin resonance (e.s.r.) measurements. The particles ingested into the cytoplasm were distinguished from those attached to the cell surface by treatment with a membrane-impermeable reducing agent, ascorbate. The validity of the assay method was tested under various conditions. The measurements provided accurate and reproducible data. The phagocytic reaction was followed as a function of time and the rate constants for the attachment and ingestion steps were obtained from the initial phase. Both steps were highly dependent on temperature. Divalent cations in the incubation medium were essential for the attachment step but apparently had no effect on the ingestion step. The metabolic inhibitors, KCN and 2-deoxyglucose, inhibited both steps. Cytochalasin B inhibited both steps, while colchicine inhibited only the attachment step but apparently had no effect on the ingestion step.

Animals↗

PubMed1976

A correlation between membrane fluidity and the critical temperature for cell adhesion.

BHK 21 cells can adhere to a protein-coated plastic dish in the presence of Ca2+ at temperatures above 12 degrees C. However, they cannot adhere below 8 degrees C. The ESR spectrum of cells spin-labeled with a stearic acid label indicated that the membrane fluidity changed characteristically at 10 degrees C, 20 degrees C, and 30 degrees C. The critical temperature for cell adhesion coincided well with one of the characteristic temperatures for the membrane fluidity change. In the case of adhesion in the presence of Mg2+, no such correlation was observed.

Calcium↗