Effect of phospholipid and detergent on the Schiff base of cephalopod rhodopsin and metarhodopsin

In the visual pigment, the chromophore retinal is bound through a Schiff base linkage with the protein moiety, opsin. The secondary interaction of retinal with opsin was studied in cephalopod rhodopsin and its photoproduct, metarhodopsin. The pK of the protonation of the Schiff base in metarhodopsin was affected by the phospholipids and detergents surrounding the protein, and varied between 9.2 and 6.9. Among nonionic detergents, the fatty acid ester of sucrose behaved like phospholipids but other detergents changed the protein conformation so that the pK of the Schiff base in metarhodopsin became nearly equal to the pK of N-retinylidene butylamine. This tendency was manifested in rhodopsin as the formation of a 380 nm pigment.

Molecular weight and structural studies on cephalopod rhodopsin

The protein moiety of squid (Watasenia scintillans) rhodopsin has been shown to have a molecular weight of 46 800 by means of amino acid analysis. This value was comparable to the value (51 000) obtained from SDS-polyacrylamide gel electrophoresis. After the squid eyes were incubated at 10 degrees C for 8 days, the rhodopsin showed a molecular weight of 39 000 on electrophoresis. The smaller molecular weight was ascertained by amino acid analysis of the rhodopsin; and may result from autolysis by the lysosomal enzyme. The rhodopsin in rhabdomeric membranes and in detergent solution was treated with chymotrypsin, papain or subtilisin. These enzymes first produced the 39 000 dalton rhodopsin and then cleaved this into the 25 000 and 14 000 dalton peptides without bleaching. The rhodopsin was attacked by proteases and readily lost an approx. 12 000 dalton peptide portion. This portion included the COOH-terminal and was rich in glutamic acid, proline, glycine, alanine and tyrosine residues.

Studies on cephalopod rhodopsin. Fatty acid esters of sucrose as effective detergents

Squid rhodopsin was extracted with solutions of fatty acid esters of sucrose (monolaurate and monostearate) and purified by DEAE-cellulose and concanavalin A-Sepharose affinity chromatography. The purified rhodopsin (A280/A480 = 2.5) contained 2.3 mol of glucosamine and 1.2 mol of phospholipid per mol of rhodopsin. The photoproduct metarhodopsin was also stable in these detergent solutions as in digitonin solution. Concanavalin A had no affinity for retinochrome.

Formation of the two-dimensional hexagonal lattice of bacteriorhodopsin in reconstituted brown membrane

The aggregation state of reconstituted bacteriorhodopsin molecules in the brown membrane has been investigated by X-ray diffraction and CD spectra. It has been confirmed that reconstituted bacteriorhodopsin molecules form the hexagonal lattice spontaneously whereas bacterioopsin molecules do not.

Fractionation of rhodopsin and other components in the rod outer segment membrane by ammonium sulfate salting-out

Purified bovine rod outer segment membrane was solubilized in a mixture of 1.5% cholic acid/20% saturated ammonium sulfate and 0.05 M phosphate buffer (pH 7.5). The solubilized rod outer segment membrane was fractionated with ammonium sulfate and 70--90% of rhodopsin (A278/A498= 1.6--1.9) was recovered in the fraction of 50 to 60% saturation with ammonium sulfate, giving a highly concentrated solution of purified rhodopsin (A1CM 498 = 83). By the method of ammonium sulfate salting-out, the solubilized rod outer segment membrane was divided into several fractions without a loss of components. The components in each fraction were examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Rhodopsin and opsin amounted to 93% of the total protein in the membrane. Other proteins with molecular weights of 46 000, 52 000, 56 000, 70 000, 95 000, 105 000, 130 000 and 270 000 were also detected. Most of phospholipids in the rod outer segment membrane remained in the supernatant above 60% saturation with ammonium sulfate.

Mean systemic pressure and mean pulmonary pressure: their effects on the total artificial heart

Mean systemic pressure (MSP) and mean pulmonary pressure (MPF), which are mean driving pressures for venous return in the natural heart, were studied in 11 calves in which the natural heart had been replaced with a total artificial heart (TAH). They were measured simply by stopping the artificial heart pumping. Although blood translocation from the arterial to the venous side was not performed, the eventual right and left atrial pressures reached six to eight seconds after stopping the TAH would represent MSP and MPP with reasonable accuracy. The MSP varied from nine to 3k mmHg (20+/-6 mmHg), whereas the MPP varied from nine to 39 mmHg (22+/-7 mmHg). The MSP varied in close relation to the right atrial pressure prior to cessation of the TAH (r=0.9124). Increases in RAP and MSP were mainly attributed to an increase in circulating blood volume. In the performance of the TAH, MSP (or MPP), proper diastolic duration and vacuum application during diastole was of prime importance in determining the end-diastolic ventricular volume.

Studies on cephalopod rhodopsin: photoisomerization of the chromophore

Photoisomerization of the chromophore of squid rhodopsin is dependent upon the irradiation temperature. Above 0 degrees C, only 11-cis in equilibrium all-trans reaction proceeds and the all-trans leads to 9-cis reaction is limited to extremely low efficiency. At liquid nitrogen temperature, 11 cis in equilibrium all-trans in equilibrium 9-cis reaction takes place. At intermediary low temperatures (-80 degrees C to -15 degrees C) another isomer of retinal may be produced by the irradiation, which forms a pigment having an absorbance maximum at 465 nm (P-465). The formation of P-465 decreases remarkably in the narrow temperature range from -30 degrees C to 0 degrees C where mesorhodopsin converts to metarhodopsin. Medsorhodopsin is quite different from metarhodopsin in the photoisomerization of the chromophore because P-465 is produced from the former but not from the latter. No P-465 is produced both at liquid nitrogen temperature and above 0 degrees C. P-465 is more labile than any of the other photoproducts so far known, that is isorhodopsin, alkaline and acid metarhodopsins. P-465 is converted to metarhodopsin by irradiation.

Refinement in application of total artificial heart, with improvement in survival and histopathological findings

Recent improvements in total artificial heart (TAH) experiments have changed the pathological findings as well as the concept of the TAH. In the past 3 years, 67 experiments were performed in our laboratory. This study concerns the 11 calves operated upon most recently. Histopathological findings in the lungs, kidneys, livers and spleens of these animals were greatly improved over findings from previously studied animals. Disseminated intravascular coagulation (DIC) syndrome has been seen in only 1 calf. These improvements can be attributed to the following factors: (1) Improved management of the lumg during surgery has essentially eliminated pulmonary insufficiency;(2) liver damage has been successfully prevented by the discovery of the relationship between high right atrial pressure and anemia; (3) careful aseptic surgical procedures and optimal prophylactic use of antibiotics and anticoagulants have minimized the incidence of infection and clot formation.

Gamma-radiolysis of D-glucose in aerated, aqueous solution

Gamma-Radiolysis of D-glucose in aerated, aqueous solution gives mainly D-glucono-1,5-lactone, D-arabino-hexosulose, and D-ribo-hexos-3-ulose, together with D-xylo-hexos-4-ulose, D-xylo-hexos-5-ulose, and other pentose, tetrose, and triose derivatives as minor products, which were estimated by mass spectrometry of their alditol-d acetates. These hexose derivatives appear to be produced by the decomposition of D-glucose peroxy-radicals which are formed by the reaction of the primary radicals of D-glucose with oxygen. Bond scission of the peroxy-radicals yields triose, tetrose, and pentose. A radiolysis mechanism for the degradation of D-glucose in aerated, aqueous solution is proposed, based on the reaction of several kinds of D-glucose radical with oxygen.

One 25 day survivor with total artificial heart

One calf, which weighed 87 kilograms, survived for 25 days with a total artificial heart (TAH) implanted orthotopically. All hemodynamic parameters stayed normal except the right atrial pressure (RAP), which increased gradually toward the end of the experiment. The cardiac output was maintained between 8.0 and 11.0 L. per minute. Kidney function was well maintained, and no pulmonary insufficiency was noted. Infection became obvious after 2 weeks of pumping although it was controlled to the extent that the calf was able to eat, to several factors, amont them mechanical damage to red blood cells, infection, malnutrition, and liver damage. The calf was standing until 30 minutes before its sudden death from cerebral thromboembolism. The calf's activity throughout the postoperative course convinced us of the feasibility of clinical application and of immediate application to studies of cardiovascular physiology and pharmacology.