THE FINE LOCALIZATION OF NUCLEOSIDE TRIPHOSPHATASE ACTIVITY IN THE RETINA OF THE FROG

Nucleoside triphosphatase (NTPase) activity was demonstrated at the submicroscopic level in the frog retina by the Wachstein-Meisel method utilizing various purine and pyrimidine nucleosides. Under the electron microscope magnesium-activated NTPase was localized in the outer and inner segments, and in the plexiform layers. NTPase active sites in the cones were localized diffusely in the 70 to 80 A interspaces between the double membranes of the stacked lamellae and in the investing cytoplasm. In the rods, on the other hand, sites of activity were observed at the periphery of the stacked lamellae as discrete electron opaque deposits measuring 1000 to 1500 A which interdigitated between the lamellae for short distances. Deposits of reaction product appeared more numerous in rods of dark-adapted frogs stimulated with monochromatic light with a wave length of 510 mµ. Enzyme activity was also observed in mitochondria of the rod and cone ellipsoids. In the outer and inner plexiform layers NTPase active sites were present on and between the membranes of axons and the plasma membranes of some of the neurons.     

PIGMENTS OF THE RETINA : II. SEA ROBIN,SEA BASS,AND SCUP

1. Visual purple from the sea robin, sea bass, and scup is almost identical spectroscopically with that from frogs. The interrelations of this pigment with vitamin A and retinene are also the same as in the frog. 2. In strong acids or at pH > 11, the visual yellow of sea robin retinas is converted irreversibly into a pH indicator, yellow in acid and almost colorless in alkaline solution. Unlike neutral visual yellow, the indicator is not removed to form either vitamin A or visual purple. In the ammoniacal retina the reversion of visual yellow itself to purple is accelerated. 3. The combined pigment epithelium and choroid layer in these fishes contain vitamin A, flavine, and an unidentified xanthophyll.     

RENEWAL OF GLYCEROL IN THE VISUAL CELLS AND PIGMENT EPITHELIUM OF THE FROG RETINA

The renewal of glycerol in the visual cells and pigment epithelium of the frog retina was studied by autoradiographic analysis of animals injected with [2-³H]glycerol. Assay of chloroform:methanol extracts showed that the labeled precursor was used mainly in lipid synthesis, although there was also some utilization in the formation of protein. Radioactive glycerol was initially concentrated in the myoid portion of rods and cones, indicating that this is the site of phospholipid synthesis in visual cells. The glycogen bodies (paraboloids) of accessory cones were also heavily labeled, suggesting the diversion of some glycerol into glycogenic pathways. In the pigment epithelium, only the oil droplets became significantly radioactive. The outer plexiform layer (which contains the visual cell synaptic bodies) and the cone oil droplets gradually accumulated considerable amounts of labeled material. Within 1–4 h, labeled molecules began to appear in the visual cell outer segments, evidently having been transported there from the myoid portion of the inner segment. Most of these were phospholipid molecules which became distributed throughout the outer segments, presumably replacing comparable constituents in existing membranes. In rods only, there was also an aggregation of labeled material at the base of the outer segment due to membrane biogenesis. These highly radioactive membranes, containing labeled molecules of lipid and protein, were subsequently displaced along the rod outer segments due to repeated membrane assembly at the base. The distribution of radioactivity supported the conclusion that membrane renewal by molecular replacement is more rapid for lipid than it is for protein.     

STUDIES ON THE UPTAKE AND RELEASE OF RADIOACTIVE TAURINE BY THE FROG RETINA

Abstract— Taurine is taken up into the frog retina by active, sodium dependent, temperature sensitive systems that show both high and low affinity for the amino acid ( K _mabout 50 μ m and 2 m m respectively). Autoradiographs from retinae incubated in radioactively labelled taurine showed heavy grain density over cell bodies in the position of amacrine interneurones and over specific strata in the inner synaptic layer of the tissue. Photoreceptor cells were also labelled.
Taurine, once accumulated by the frog retina, is not lost during the incubation and is only slowly metabolised. Electrical stimulation caused taurine release above the level of spontaneous efflux but light or depolarisation of the tissue with 40m m -potassium chloride did not.     

蛙离体视网膜中杆系统对锥系统的抑制作用

在蛙离体视网膜标本上研究了由条件刺激(F_c)引起的快速暗适应(RDA)过程中b 波的变化。当F_c超过一定强度时,以501nm 闪光为测试刺激(F_(t(501)))时b波阈值单调下降,先为锥相后为杆相,两者过渡处呈现杆-锥转折;但以654nm闪光为测试刺激时(F_(t(654))),阈值先略有下降,继而上升,之后再下降。F_(t(654))应阈值在RDA 过程中的这种升高是反映575锤系统的活动受到502杆系统抑制的结果,433杆系统对此没有明显的贡献,主要依据是:(1)F_(t(654))反应阈值的上升在时间上与暗适应曲线的杆相的出现一致;(2)在RDA 过程的锥相,反应的光谱敏感性与锥色素吸收光谱一致,而在F_(t(654))反应阈值上升到最大值时,反应的光谱敏感性与502杆色素的吸收光谱非常接近;(3)对502杆系统作用等效的F_(c(439))、F_(c(501))和F_(c(616))作用后,F_(t(654))的敏感度变化在整个RDA 过程中基本相同。     

THE POTENTIAL AND RESPIRATION OF FROG SKIN : I. THE EFFECT OF THE HOMOLOGOUS CARBAMATES. II. THE EFFECT OF CERTAIN LYSINS

Measurements of the O₂ consumption and of the potential of frog skin, made under comparable conditions, show that the homologous carbamates (ethyl, propyl, butyl, and amyl) reduce both the O₂ consumption and the potential, but not in a similar manner. In this respect, the effect of the carbamates is like the effect of reduction in O₂ tension. The simple lysins (saponin and the bile salts), on the other hand, abolish the potential without reducing the O₂ consumption at all. Irrespective of whether one considers the concentration of carbamate in the entire system or the amount of carbamate adsorbed by the frog skin, Traube''s rule relating the effect of a carbamate to its position in the homologous series does not seem to apply.     

STUDIES ON THE PHYSIOLOGICAL EFFECTS OF NON-POLAR-POLAR ORGANIC ELECTROLYTES : I. THE INFLUENCE UPON THE RESTING POTENTIAL OF FROG MUSCLE

1. The commonly used detergents have a poisonous effect, which is due to the non-polar-polar configuration of their organic anion. The non-polar organophilic half of the ion is built up by a long chain of alkyl radicals (8 to 18 carbon atoms), the polar hydrophilic half by a sulfonate or sulfate. If brought into contact with the organic surface membrane of a cell, this structure, due to the strong attachment of the alkyl chains to its surface, and due to the pull of the hydrophilic part towards the surrounding water, is subjected to a heavy stress terminating in tearing to pieces the membrane (by denaturing and loosening the membrane components; bacteriolysis, cytolysis). Correspondingly, with frog muscle, one end of which has been treated with the detergent solution, an irreversible negative injury potential is produced. 2. Applying, instead, the compounds bearing short chains of alkyl radicals (1 to 6 carbon atoms), producing less stress on the membrane and correspondingly a slighter derangement of its architecture, a reversible positive resting potential appears. This is interpreted to be the effect of the non-polar part of the anion, which, due to its surface activity, intrudes into the pores of the membranes, notwithstanding the negative charge of their walls. 3. The short chained detergents seem to be replaceable by various organic "semidetergents," the organophilic behavior of their anion being represented by a slight chemical affinity (NH₂), the hydrophilic by the effect of a carboxyl group (COO) instead of sulfate or sulfonate. The effect of the semidetergents on muscle is a positive reversible potential. Their physiological significance may be visualized as a functional activation.     

STUDIES CONCERNING THE NATURE OF THE SECRETORY ACTIVITY OF THE ISOLATED RINGER-PERFUSED FROG LIVER : I. THE DIFFERENTIAL SECRETION OF PAIRS OF DYESTUFFS

The isolated Ringer-perfused frog liver is able to concentrate in its secretion several hundred or even thousand times a great number of dyestuffs. When two dyestuffs are perfused simultaneously, the liver separates them to a lower or higher degree, some times to such an extent that the secretion of one of them is entirely suppressed by the other. Which one of the two dyestuffs appears prevailingly in the secretion, does not depend upon its diffusibility or lipoid solubility, but perhaps upon its adsorbability. This is concluded from the fact that dyestuffs provided with several (4 to 5) strongly hydrophilic sulfonate groups in their molecule, are not permitted to pass the gland.     

ELECTRIC IMPEDANCE OF THE FROG EGG

Electrical impedance measurements were made upon unfertilized and fertilized eggs of the leopard frog, Rana pipiens, over a frequency range of 0.05 to 10 kc. Average values of 170 ohm cm.² were obtained for the plasma membrane resistance of the egg, 2.0 µf/cm.² for the plasma membrane capacity, 86° for the phase angle of the membrane, and 570 ohm cm. for the specific resistance of the interior. These values did not change upon fertilization. No spontaneous rhythmical impedance changes such as have been found by Hubbard and Rothschild in the trout egg were found in frog eggs.