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J Yguerabide

Publications and source records attributed to J Yguerabide.

32 records · Page 2Linked to original sources
PubMed1981

Mobility of surface proteins on normal rat macrophages and on a "macrophagelike" rat tumor.

Peritoneal macrophages endocytosed their histocompatibility antigens (RT1), Fc receptors (FcR), and concanavalin A (Con A) receptors after cross-linking by ligands, but did not cap these membrane proteins. The 323N cell, a "macrophage like" tumor cell, under identical conditions capped its surface proteins. Experiments measuring fluorescence recovery after photobleaching showed that the mobile fraction of RT1 was significantly greater in 323N cells than in normal peritoneal macrophages. Presumably, the membrane proteins of 323N are not as tethered to the cytoskeleton, or, if so, are in a nexus that is not the same as that which occurs between membrane proteins of normal macrophages and the cytoskeleton. The mobility of RT1 on normal lymphocytes was also different from that of macrophages. These observations suggest that the movement of membrane molecules is determined by cell type and is regulated by the cytoskeleton which varies in structure and function from cell type to cell type.

Animals↗
PubMed1979

Membrane dynamics of differentiating cultured embryonic chick skeletal muscle cells by fluorescence microscopy techniques.

Changes in membrane fluidity during myogenesis have been studied by fluorescence microscopy of individual cells growing in monolayer cultures of embryonic chick skeletal muscle cells. Membrane fluidity was determined by the techniques of fluorescence photobleaching recovery (FPR), with the use of a lipid-soluble carbocyanine dye, and by fluorescence depolarization (FD), with perylene used as the lipid probe. The fluidity of myoblast plasma membranes, as determined from FPR measurements in membrane areas above nuclei, increased during the period of myoblast fusion and then returned to its initial level. The membrane fluidity of fibroblasts, also found in these primary cultures, remained constant. The fluidity in specific regions along the length of the myoblast membrane was studied by FD, and it was observed that the extended arms of the myoblast have the highest fluidity on the cell and that the tips at the ends of the arms had the lowest fluidity. However, since the perylene probe used in the FD experiments appeared to label cytoplasmic components, changes in fluidity measured with this probe reflect changes in membrane fluidity as well as in cytoplasmic fluidity. The relative change in each of these compartments cannot yet be ascertained. Tips have specialized surface structures, filopodia and lamellipodia, which may be accompanied by a more immobile membrane as well as a more rigid cytoplasm. Rounded cells, which may also have a more convoluted surface structure, show a lower apparent membrane fluidity than extended cells.

Animals↗
PubMed1979

Mobility and density of AgB, "Ia", and Fc receptors on the surface of lymphocytes from young and old rats.

Analysis of spleen cell populations from old Lewis rats (greater than 24 months) and from young Lewis rats (3 to 4 months) in a fluorescence-activated cell sorter indicated that with aging there is a loss of brightly stained Ia and Fc receptor- (FcR) positive cells. The density of AgB, Ia, and FcR was diminished on the surface of cells from old rats. The rate of capping of all three membrane proteins was slower on cells from old rats. Colchicine treatment allows capping of AgB with a single ligand only in young rats. Fluorescence photobleach recovery experiments (FPR) show that the fluidity of the lymphocyte membrane from old rats is diminished and the lateral diffusion of AgB is decreased. The colchicine and FPR experiments suggest that the changes in capping in old rats are due to, in part, alterations in membrane fluidity and cytoskeletal function.

Aging↗
PubMed1978

Microviscosity of mucosal cellular membranes in toad urinary bladder: relation to antidiuretic hormone action on water permeability.

The microviscosity of cellular membranes (or membrane fluidity) was measured in suspensions of single mucosal cells isolated from the urinary bladder of the toad, Bufo marinus, by the technique of polarized fluorescence emission spectroscopy utilizing the hydrophobic fluorescent probe, perylene. At 23 degrees C, 5 mM dibutyryl cyclic 3',5'-AMP decreased the apparent microviscosity of the cell membranes from 3.31 to 3.07 P, a minimum decrease of 7.3% (P less than 0.001) with a physiological time course. Direct visualization of the cell suspension indicated that 98% of the cells were viable, as indicated by Trypan Blue dye exclusion. The fluorescent perylene could be seen only in plasma membranes, suggesting that the measured viscosity was that of plasma membrane with little contribution from the membranes of cellular organelles. Addition of antidiuretic hormone to intact hemibladders stained with perylene produced changes in fluorescence consistent with a similar 7% decrease in apparent microviscosity with a physiological time course. However, finite interpretation of the findings in intact tissue cannot be made because the location and the fluorescent lifetime of the probe could only be conducted on the isolated cells. Comparison with previously determined relationships between water permeability and microviscosity in artificial bilayers suggests that the 7% (a lower limit) decrease in microviscosity would produce only a 6.5% increase in water permeability.

Animals↗
PubMed1977

Interaction of hemoglobin with red blood cell membranes as shown by a fluorescent chromophore.

Hemoglobin quenching of the fluorescence intensity of 12-(9-anthroyl)stearic acid (AS) embedded in the red blood cell membrane occurs through an energy transfer mechanism and can be used to measure the binding of hemoglobin to the membrane. The binding of hemoglobin to red cell membranes was found to be reversible and electrostatic in nature. Using a theory of energy transfer based on Förster formulation, the quantitative data for the binding were derived. The number of binding sites was found to be 1.4 +/- 0.2 X 10(6) molecules per cell and the binding constant was 0.85 X 10(8) M-1.

Energy Transfer↗
PubMed1977

Classification and localization of hemoglobin binding sites on the red blood cell membrane.

The binding of hemoglobin to the red cell membrane was characterized over a wide range of free hemoglobin concentrations by measurement of membrane bound and supernatant hemoglobin. Scatchard analysis of the binding data revealed two classes of sites: high affinity sites with a binding constant of 1 X 10(8) M-1 and 1.2 X 10(6) sites per cell, and a second, low affinity class of sites with a binding constant of 6 X 10(6)M-1 and 6 X 10(6) sites per cell. The low affinity sites are shown to be nonspecific and appear to be a result of the ghost preparation. The high affinity sites are shown to be specific to the inner surface of the red cell membrane. The competition of hemoglobin and glyceraldehyde-3-phosphate dehydrogenase suggests band III proteins as a potential binding site for hemoglobin.

Binding Sites↗
PubMed1977

Fluidity in the membranes of adult and neonatal human erythrocytes.

Several antigens and receptors are mobile in the plane of the membrane of the intact neonatal human erythrocyte but not in the membrane of the normal adult cell. In this report, measurements of the fluorescence polarization of perylene dissolved in isolated erythrocyte membranes are reported, which are indistinguishable for the two kinds of cells. This result indicates that the viscosities of the membrane interiors of the two cells are the same. The observed mobility differences, therefore, cannot be attributed to different lipid viscosities in the two membranes.

Adult↗
PubMed1973

Photoreversible conductance changes induced by phytochrome in model lipid membranes.

The plant protein phytochrome induces photoreversible conductance changes when added to a black lipid membrane made from oxidized cholesterol. The conductance of the phytochrome-modified membrane is increased by red-light illumination but is decreased by illumination with far-red light. Denatured phytochrome does not affect the conductance of the model membrane.

Cholesterol↗
PubMed1971

Fluorescence spectroscopy of an oriented model membrane.

We have devised a simple method that makes it feasible to apply fluorescence techniques to lipid bilayer membranes to elucidate aspects of their structure and dynamics. Fluorescence excitation, emission, and polarization spectra were obtained from a single spherical bilayer membrane consisting of oxidized cholesterol and fluorescent probe. The emission transition moments of N,N'-di(octadecyl)oxacarbocyanine and 12-(9-anthroyl)-stearic acid were found to be aligned parallel to the plane of the bilayer, whereas that of p-bis-[2-(4-methyl-5-phenyloxazolyl)]-benzene was aligned in a perpendicular direction. All three probes exhibited appreciable rotational mobility, parallel to the plane of the bilayer, in durations of nanoseconds. An attractive feature of this model membrane is that fluorescence measurements can be made at the same time as electrical measurements and perturbations. Also, it may be possible to incorporate functional protein assemblies into this model and to use fluorescence spectroscopy to delineate some aspects of their assembly and function.

Cholesterol↗
PubMed1969

Dependence of the kinetics of singlet-singlet energy transfer on spectral overlap.

Electronic excitation energy can be transferred between chromophores separated by distances of the order of 30 A. Förster proposed that the transfer occurs by a dipole-dipole resonance interaction which depends on certain spectroscopic and geometric properties of the donor-acceptor pair. His prediction that the rate of transfer depends on the inverse sixth power of the distance between the chromophores was verified previously. In this work, we tested a second prediction of Förster's theory, namely, that the transfer rate is proportional to J, the magnitude of the overlap between the emission spectrum of the energy donor and the absorption spectrum of the energy acceptor.The energy donor was an N-methylindole moiety, and the acceptor was a ketone. These chromophores were fused to a rigid steroid that separated them by 10.2 A. Rate constants for singlet-singlet energy transfer in this system were obtained by nanosecond flash spectroscopy. J was varied over a 40-fold range simply by altering the solvent. We found that the transfer rate is proportional to J, as predicted by Förster's theory. The results bear on the potential use of this energy transfer process to measure distances in biological macromolecules. It is evident that the length of such a spectroscopic ruler can readily be controlled by varying the magnitude of the spectral overlap integral of the energy donor-acceptor pair.

Journal Article↗