Electric and optical anisotropy and their osmotically induced changes of photoreceptor disk membrane vesicles

Electro-optical characterization of the photoreceptor disk membrane vesicle is performed by examining the electric field and concentration dependence of the study-state birefringence of aqueous suspensions of the vesicles. The electric polarizability anisotropy is found to be negative and of large magnitude: alpha 1 - alpha 2 = -(1-3) X 10 cm3. The optical anisotropy is determined to be also negative but of small magnitude: g 1 - g 2 = -1 X 10(-7). The specific Kerr constant deduced from the concentration dependence of the Kerr constant is found to be very large: Ksp = 7 X 10(-4) e.s.u. Upon deforming the vesicles osmotically from the spherical shell to the disk structure, the steady-state birefringence increases by an order of magnitude which is attributed solely to the increase in optical anisotropy attending the corresponding change in the geometric eccentricity of the vesicle. A plausible birefringence mechanism based on the known structural features of the vesicles is proposed, which would account for these findings.

Lateral diffusion of photopigments in photoreceptor disk membrane vesicles by the dynamic Kerr effect

The lateral diffusion of photopigment molecules in the photoreceptor disk membranes, osmotically swollen into spherical vesicles, has been investigated by dynamic Kerr effect measurements. Upon application of a rapidly reversing bipolar electric field to dilute aqueous suspensions of bovine disk membrane vesicles, the birefringence transient shows a characteristic rise and a deep dip corresponding to the first and second pulses, respectively. The birefringence transient is ascribed to the slowly induced dipole moment caused by electric field induced displacement of the photopigment distribution on the vesicular surface. The lateral translational diffusion coefficient is estimated from the time constant of the slowly induced dipole as D = (3.3 +/- 1.2) X 10(-9) cm2 s-1. When spermine, a cationic tetraamine, is bound to the disk membrane vesicles, the relaxation time of the slowly induced dipole is shown to become longer, indicating that the birefringence mechanism is indeed due to the field-induced photopigment displacement.

Permeability to ions of bovine retinal disk membrane vesicles in the bleached state

The permeability of the bleached disk membrane of retinal rod outer segments to univalent and divalent ions is studied by light scattering. The membranes are isolated from frozen dark-adapted bovine retinae, swollen into spherical vesicles in a hypotonic medium and bleached in dilute suspension and their size is determined by elastic and quasi-elastic light scatterings. Various electrolytes are then added to the suspending medium in order to examine their osmotic activity relative to the vesicles deformation characteristics. By following the deformation behavior of the membrane vesicles by elastic light scattering in terms of the oblate ellipsoidal shell model, the osmotic activity of a given electrolyte is qualitatively deduced and thereby the permeability of the membrane to the electrolyte is ranked in reference to a chosen standard, i.e., sucrose. By this method, we show that the permeabilities to Na+, K+, Mg2+ and Ca2+ are all alike, and those to halides (F-, Cl-, Br-, I-), nitrate and phosphates (HPO4(2-)/H2PO4-) are similar. Acetate, however, is about 3-times more permeative, while sulfate is less permeative than the other anions by about the same factor. The viability of our method is checked with use of an ionophore, lasolocid (X-537A), by establishing partial recovery from the osmotic deformation through the suppression of the cation osmotic effect. Ion-induced aggregation and pH-dependent size and shape changes are both found to be insignificant.

Dynamic kerr effect measurements on photoreceptor disk membrane vesicles

Dynamic Kerr effect measurements were performed with dilute aqueous suspensions of monodisperse spherical vesicles (approximately 1 micron diameter), isolated from the rod outer segment of bovine retina. A large birefringence, amounting to the specific Kerr constant of 10(-3) esu, can be observed. When a sufficiently long duration pulse (1 s) is applied, the decay of birefringence can be represented by a single exponential profile, yielding a relaxation time of 100 +/- 20 ms in 1 mM imidazole buffer. This is consistent with the rotatory relaxation time of these spherical membrane vesicles. When a short duration is applied, the birefringence increases more steeply and the decay profile contains several components. The slowest (terminal) relaxation time is 86 +/- 15 ms is due to the same process as the one observed in the slow pulse case.

Photoinduced size change of membrane vesicles from bovine retinal rod outer segment

Quasielastic light-scattering measurements were made on isolated, osmotically swollen, bovine rod outer segment (ROS) disk membranes in aqueous Ficoll. The translational diffusion coefficients determined were (1.66 +/- 0.21) X 10(-9) and (2.31 +/- 0.14) X 10(-9) cm2/s at 25 degrees C for the unbleached and bleached membranes in 5% Ficoll, respectively, yielding the Stokes radii of 0.53 +/- 0.07 micronm for the former and 0.38 +/- 0.02 micronm for the latter. This photoinduced size decrease, which corresponds to a 60% decrease in the intravesicular volume, is far more pronounced than thos reported by others for ROS fragments.

Intact photoreceptor membrane from bovine rod outer segment: size and shape in bleached state

Photoreceptor disk membranes isolated from bovine rod outer segments are suspended in dilute aqueous sucrose (4.36 X 10(-3%)) and bleached, and their size and shape are determined with quasielastic and elastic light scattering. They are found to be extremely homogeneous spherical vesicles with a radius of 0.49 +/- 0.07 mum which appear to have derived from the native disk shape by osmotic swelling.

Emergency surgery for calculous diseases of the upper urinary tract

Nineteen patients with calculous disease of the upper urinary tract presenting as anuria or acute pyonephrosis are reported. The necessity for emergency surgical treatment is stressed. The methods of surgical treatment and the results are discussed.