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.     

视觉系统皮层下细胞的方位和方向敏感性

视觉方位、方向选择性曾被认为是高等哺乳动物视皮层细胞的特有功能。近年来大量的实验结果表明,视皮层下的外膝体神经元和视网膜神经节细胞都具一定程度的方位和方向敏感性,这些性质是遗传决定的,不受后天环境的影响。在外膝体内,已为视皮层细胞高度的方位、方向选择性和功能柱的形成做出了初步的分类与编组,提供了前级安排。这种皮层下的方位、方向敏感性细胞在发育过程中传递和加工了环境视觉信息,促进了视皮层更强的方位、方向选择性机制和方位功能柱的形成。外膝体在视觉信息平行处理通道的形成上起着分类集聚的重要作用。     

THE SITE OF ORIGIN OF ELECTRICAL RESPONSES IN VISUAL CELLS OF THE LEECH, HIRUDO MEDICINALIS

In leech visual cells the presumed light-absorbing structures are microvilli arising from the membrane of what would seem to be a large intracellular vacuole. This vacuole, however, is an extracellular compartment, since it communicates with the intercellular spaces through narrow channels. Therefore, the membrane of the microvilli is—as in other invertebrate visual cells—a part of the cell membrane. Visual responses recorded with an electrode within the vacuole were compared with the intracellular recordings. Following illumination the vacuole becomes negative with respect to the outside fluid, while the cells are depolarized. This finding indicates that inward current penetrates the cell through the microvillar membrane. It is concluded, therefore, that the electrical response (receptor potential) originates as a result of changes in the properties of the light-absorbing membrane.     

ORGANIZATION AND ACTIVITY IN THE PRE- AND POSTOVULATORY FOLLICLE OF NECTURUS MACULOSUS

The established follicle envelope of Necturus maculosus consists of a layer of follicle cells (granulosa) surrounding the developing oocyte, a layer of theca comprised of connective tissue cells, fibers, and matrix, and a layer of serosal cells. The changes in shape and fine structure of these layers during differentiation accompanying oogenesis are described. The cells and capillaries of the follicle envelope are engaged in an extensive pinocytotic activity, the details of which are described. We used cytochemical techniques to analyze the activity of the follicle envelope with respect to lipid accumulation and alkaline phosphatase activity. Radioautographic results indicate that cells of the follicle envelope are capable of incorporating tritium-labeled uridine and amino acids at certain times during oocyte growth. A comparative analysis was made of the soluble proteins in follicle envelopes isolated from immature oocytes and of those in follicle envelopes isolated from nearly mature oocytes and in postovulatory follicles. After the oocyte is ovulated, the cells of the follicle envelope are converted into a postovulatory follicle. The cells of the postovulatory follicle undergo further differentiation resulting in their becoming actively engaged in the formation of a secretion, the details of which are described at the electron microscope level. Analysis of the postovulatory follicle by thin-layer chromatography and cytochemistry demonstrated the presence of a wide variety of lipid substances and the possible presence of steroid. That the postovulatory follicle may be engaged in steroid biosynthesis is also suggested by studies involving the demonstration of 3 β-hydroxysteroid dehydrogenase activity with cytochemical techniques applied to frozen sections and to soluble proteins separated by gel electrophoresis.     

THE DIFFERENTIATION OF PIGMENT CELLS IN CULTURES OF CHICK EMBRYONIC NEURAL RETINAE

Neural retinal cells of 8–9 day-old chick embryos were differentiated into pigment cells in the conditions of cell culture for about 25 days. The increase of pigment cells in vitro was semi-quantitatively shown, by counting the number of black foci of pigmented cells per plate throughout the culture period. The increase paralleled the increase in the activity of tyrosinase. The addition of a small number of pigment cells freshly dissociated from tapeta to the cultures of neural retinae did not increase the number of black foci in vitro . Electron microscopic observations revealed the morphological differences of melanin granules between those in pigment cells of the neural retinal cultures and those in cultured tapetum cells. It was discussed that pigment cells appearing in the neural retinal cultures were derived from neural retinal cells, but not from contaminated cells of the tapetum.     

锦鲤总色素及色素组分的比较研究

用光谱和色谱两种方法对锦鲤的总色素和色素组分进行了研究。研究结果表明,红色锦鲤、乌鲤和绯写锦鲤总色素光谱在可见光区(448nm和470nm)有两个完全相同的吸收峰,黄写锦鲤和昭和三色锦鲤总色素光谱在可见光区(445nm和472nm附近)有两个相近的吸收峰,锦鲤所含色素组分均以杏黄色或橙色为主,其他色素组分为辅。锦鲤黑色色斑是由于黑色素存在时,其他各色素组分的颜色被黑色所掩盖;锦鲤其他色斑的形成则是由于其体内各色素组分以不同比例相互搭配组合的结果。亲缘关系越近的锦鲤其总色素组分就越相似,红色锦鲤和乌鲤均含有六种相同的色素组分,绯写锦鲤除杏黄色和橙色色素组分与前二者的同色色素组分Rf值不同外,其余四种同色色素组分的Rf值均相近;黄写锦鲤与昭和三色锦鲤分别含有三种和四种色素组分且Rf值差异显著。据此推测,红色锦鲤、乌鲤和绯写锦鲤可能具有较近的亲缘关系,而黄写锦鲤、昭和三色锦鲤与前三者之间可能具有较远的亲缘关系。该研究有望为锦鲤增色饵料的研制与开发提供理论依据,使锦鲤的观赏价值和经济价值得到进一步提高。       

VISUAL ADAPTATION AND CHEMISTRY OF THE RODS

1. The reality of a chemical cycle proposed to describe the rhodopsin system is tested with dark adaptation measurements. 2. The first few minutes of rod dark adaptation are rapid following short, slower following long irradiation. As dark adaptation proceeds, the slow process grows more prominent, and occupies completely the final stages of adaptation. 3. Light adaptation displays similar duality. As the exposure to light of constant intensity lengthens, the visual threshold rises, and independently the speed of dark adaptation decreases. 4. These results conform with predictions from the chemical equations.     

食用天然色素的提取及其稳定性研究

研究了食用天然色素的一般提取工艺及其理化性质,并实验分析了光、热、酸碱、防腐剂、氧化还原剂对萝卜红色素、郁金香红色素、郁金香黄色素的稳定性影响。     

THE VISUAL DISCRIMINATION OF INTENSITY AND THE WEBER-FECHNER LAW

1. A study of the historical development of the Weber-Fechner law shows that it fails to describe intensity perception; first, because it is based on observations which do not record intensity discrimination accurately, and second, because it omits the essentially discontinuous nature of the recognition of intensity differences. 2. There is presented a series of data, assembled from various sources, which proves that in the visual discrimination of intensity the threshold difference ΔI bears no constant relation to the intensity I. The evidence shows unequivocally that as the intensity rises, the ratio See PDF for Equation first decreases and then increases. 3. The data are then subjected to analysis in terms of a photochemical system already proposed for the visual activity of the rods and cones. It is found that for the retinal elements to discriminate between one intensity and the next perceptible one, the transition from one to the other must involve the decomposition of a constant amount of photosensitive material. 4. The magnitude of this unitary increment in the quantity of photochemical action is greater for the rods than for the cones. Therefore, below a certain critical illumination—the cone threshold—intensity discrimination is controlled by the rods alone, but above this point it is determined by the cones alone. 5. The unitary increments in retinal photochemical action may be interpreted as being recorded by each rod and cone; or as conditioning the variability of the retinal cells so that each increment involves a constant increase in the number of active elements; or as a combination of the two interpretations. 6. Comparison with critical data of such diverse nature as dark adaptation, absolute thresholds, and visual acuity shows that the analysis is consistent with well established facts of vision.     

PROTEIN SYNTHESIS IN VISUAL CELLS OF LIMULUS

Abstract— The incorporation of l -[4,5-³H]leucine into the primary visual cells of lateral eyes of Xiphusura polyphemus (Limulus) was followed by electron microscopic radio-autography, while protein synthesis in the tissue surrounding the primary cells was measured by scintillation counting of the extracted protein. In the primary cells, the incorporation of radioactivity during 24 h into the rhabdomal membranes was 10–20 times greater in dark than in light, and was especially high in eyes that had been exposed to light before a period of incorporation in the dark. In tissue adjacent to the primary cells, protein synthesis was about 50 per cent greater in eyes exposed to light. These results are interpreted in terms of the photochemistry of Limulus rhodopsin and the competition for ATP between sodium-pump and protein-synthetic mechanisms.     

维生素C对视网膜色素上皮蓝光损伤保护作用的研究(简报)

维生素C为6碳多羟化合物,在化学反应中易失去电子,依次生成半脱氧抗坏血酸和脱氧抗坏血酸。因此,维生素C可作为自由基清除剂,能迅速与超氧阴离子、氢化氧基、过氧化氢、羟自由基反应,生成抗坏血酸自由基。蓝光作为一种短波长,靠近紫外线频段的光,具有能量高的特点,是自然界中导致视网膜色素上皮细胞损伤甚至凋亡的主要光线。本实验通过观察蓝光照射视网膜色素上皮,对其DNA的损伤产生光损伤作用,并比较加入维生素C后对这种光损伤的保护作用,以期探讨维生素C在     

EFFECTS OF CULTURE MEDIA ON THE "FOREIGN" DIFFERENTIATION OF LENS AND PIGMENT CELLS FROM NEURAL RETINA IN VITRO

Neural retinal cells of 3.5-day-old quail embryos were cultured as a monolayer to examine their potentials for differentiation in vitro. The "foreign" differentiation into lentoid and pigment cells was much affected by the choice of medium (Eagle's MEM and Ham's F–12); in Eagle's MEM, neural retinal cells differentiated extensively into lentoid bodies and pigment cells, as previously reported in cultures of chick neural retinal cells, while in Ham's F–12, though the cells proliferated as well as in Eagle's MEM, the "foreign" differentiation is inhibited. When primary cultures were transferred to secondary cultures, the occurrence of "foreign" differentiation did not depend on the medium used for the primary culturing, but wholly on the medium used for secondary cultures. This difference in differentiation in two different media was quantitatively substantiated by measuring the amounts of α-, δ-crystallins and melanins of cultured cells.     

THE QUANTIC AND STATISTICAL BASES OF VISUAL EXCITATION

In the article entitled "The quantic and statistical bases of visual excitation" (J. Gen. Physiol., 1947–48, 31, 269), in footnote 1, at the bottom of page 274, read, The product k (k–1) ..., may be written See PDF for Equation. On page 284, in equation (1) add, t = mτ; m = 1,2,3.... I take this occasion to call attention to the fact that in 1944 van der Velden developed two equations, one of which described the variation of liminal energy with the flash time and the other this variation with the visual angle of the spot; both of them apply in the case of homogeneous populations of receptors (rods). These equations are very similar to mine, obtained in an entirely different manner and published nearly 4 years later. In fact, until very recently I was not aware of the equations of van der Velden, published in Physica, 1944, 11, 179, because the papers published in that journal, and particularly those which are written in Dutch, generally become known to French physiologists as abstracts which are often incomplete. Thus the priority of the theoretical basis of the empirical laws which are directly related to the two equations in question belongs entirely to van der Velden. ERNEST L. M. BAUMGARDT In Vol. 31, No. 3, January 20, 1948, page 261, in equation (1) for H ₂ read H ₁. On page 262, in equation (5) for H read H ₂. On page 265, in the third line from the bottom of the page, for 4 c.mm. read 5.24 c.mm. On the same page, in the second line from the bottom of the page, for 5 c.mm. read 6.86 c.mm.     

THE VISUAL ACUITY AND INTENSITY DISCRIMINATION OF DROSOPHILA

Drosophila possesses an inherited reflex response to a moving visual pattern which can be used to measure its capacity for intensity discrimination and its visual acuity at different illuminations. It is found that these two properties of vision run approximately parallel courses as functions of the prevailing intensity. Visual acuity varies with the logarithm of the intensity in much the same sigmoid way as in man, the bee, and the fiddler crab. The resolving power is very poor at low illuminations and increases at high illuminations. The maximum visual acuity is 0.0018, which is 1/1000 of the maximum of the human eye and 1/10 that of the bee. The intensity discrimination of Drosophila is also extremely poor, even at its best. At low illuminations for two intensities to be recognized as different, the higher must be nearly 100 times the lower. This ratio decreases as the intensity increases, and reaches a minimum of 2.5 which is maintained at the highest intensities. The minimum value of ΔI/I for Drosophila is 1.5, which is to be compared with 0.25 for the bee and 0.006 for man. An explanation of the variation of visual acuity with illumination is given in terms of the variation in number of elements functional in the retinal mosaic at different intensities, this being dependent on the general statistical distribution of thresholds in the ommatidial population. Visual acuity is thus determined by the integral form of this distribution and corresponds to the total number of elements functional. The idea that intensity discrimination is determined by the differential form of this distribution—that is, that it depends on the rate of entrance of functional elements with intensity—is shown to be untenable in the light of the correspondence of the two visual functions. It is suggested that, like visual acuity, intensity discrimination may also have to be considered as a function of the total number of elements active at a given intensity.     

THE VISUAL SYSTEM AND VITAMINS A OF THE SEA LAMPREY

The porphyropsin-vitamin A₂ cycle has been found heretofore only in the retinas of bony fishes capable of existence in fresh water. Cyclostomes, due to their primitive and isolated phylogenetic position, might be expected to possess the rhodopsin-vitamin A₁ cycle common to marine elasmobranchs, almost all marine teleosts, and all terrestrial vertebrates so far examined. Yet the anadromous sea lamprey, Petromyzon marinus, possesses primarily the porphyropsin system, like an anadromous teleost. This observation greatly extends the phylogenetic association of vitamin A₂ with the capacity for freshwater existence. Compared with freshwater and anadromous teleosts, the lamprey retina contains the porphyropsin system in extremely low concentration. The remaining eye tissues, like the retina, contain both vitamins A₁ and A₂, the latter greatly predominant. The livers of larval and adult lampreys, however, appear to contain vitamin A₁ alone. This situation also is not without teleost precedent, since the carp and certain anadromous salmonids display similar reversals of vitamin A pattern in the liver and eye tissues.     

THE VISUAL SYSTEM AND VITAMINS A OF THE SEA LAMPREY

On page 333, Vol. 25, No. 3, January 20, 1942, the cuts for Figs. 1 and 3 should be interchanged. The legends should remain where they now appear.     

OXIDATIVE AND HYDROLYTIC ENZYMES IN THE NEPHRON OF NECTURUS MACULOSUS : Histochemical, Biochemical, and Electron Microscopical Studies

The distribution of oxidative and hydrolytic enzyme activities along the nephron of Necturus maculosus Rafinesque was studied histochemically. The proximal tubule possessed all the demonstrable enzyme activities associated with the hexose-monophosphate shunt and glycolysis, but lacked detectable succinic dehydrogenase and cytochrome oxidase activities. Krebs cycle enzymes other than succinic dehydrogenase were easily detectable. The distal tubule, on the other hand, possessed no detectable hexose-monophosphate shunt enzyme activities, but all demonstrable glycolytic and Krebs cycle enzymes and cytochrome oxidase were present in high activity. These data indicate that the proximal tubule of Necturus probably cannot depend, as can the distal tubule, on the Krebs cycle and cytochrome system to provide energy for its transport processes, an inference supported, in general, by available physiological evidence. The question of the importance of the hexose shunt to proximal tubular function arises. Evidence is presented that the proximal tubular blood supply is primarily venous in nature, a hypothesis which would correlate well with its anaerobic metabolic pattern. In addition, the absence of cytochrome oxidase and succinic dehydrogenase from the proximal tubular cells implies either that they possess very few mitochondria, or that their mitochondria have a very unusual enzymatic pattern. Electron microscopical observations and data obtained from the measurement of the enzyme activities of homogenates of Necturus kidney are presented which indicate that the second hypothesis is more probably correct.