Visual pigments and the photic environment: the cottoid fish of Lake Baikal.

The endemic cottoid fish of Lake Baikal in Eastern Siberia offer a singular opportunity for examining within a number of closely related species, the relationships of visual pigments, photoreceptor complements and depth within a deep freshwater environment. The lake, the deepest (1600 m) and one of the largest and most ancient in the world, is unique in that the oxygen levels at the bottom are only reduced to about 80% of the surface levels. We have studied, by light microscopy, microspectrophotometry and visual pigment extraction, the retinas from 17 species of Baikal cottoids that live at different depths within the lake. Generally the retinas contain, in addition to rods, large green-sensitive double cones and small blue-sensitive single cones: surprisingly for freshwater fish, the visual pigments are based on Vitamin A1. The lambda max of both rods and cones are displaced to shorter wavelengths with increasing depth. Surface species have cones with lambda max at about 546, 525 and 450 nm and rods at 523 nm, deeper living species retain cones, but with lambda max shifting towards 500 and 425 nm and with rods at 480 nm, whereas the deepest living fish possess only rods (lambda max 480-500 nm). These data clearly show a correlation between photoreceptor complement, visual pigment lambda max and depth, but question the hypothesis that there is a correlation of pigment lambda max with water colour since, in contrast to oceanic waters, the maximum transmission of Baikal water is between 550 and 600 nm.

Immunocytochemical reactivity of rod and cone visual pigments in the sturgeon retina.

Microspectrophotometry and immunocytochemistry with several antivisual pigment antibodies were used to study visual cells of the Siberian sturgeon, Acipenser baeri Brandt. The retina contained rods and three morphological types of cones: large cones with oil drops, small cones with oil drops, and cone-like cells without oil drops. Rods and cone-like drop-free cells were found to possess porphyropsin-549, while the large oil drop-bearing cones contained red-sensitive (P613), green-sensitive (P542), and blue-sensitive (P462) visual pigments. The immunocytochemical staining pattern with three antibodies to visual pigment proteins also revealed one visual pigment in rods and three visual pigments in cones. Rods were labeled with all three antibodies, while the majority of large cones (type I), presumably the red-sensitive ones, were negative with the polyclonal serum AO against bovine opsin. A less-frequently occurring large cone type (type II) was stained by all three antibodies including mAb COS-1 specific to middle-to-long-wave visual pigments in birds and mammals, and is thought to be green-sensitive. An even less-frequent large cone type (type III, probably the blue-sensitive one) did not bind COS-1. The small cones with oil droplets showed immunoreactivities similar to either type II or type III cones. The oil drop-free small photoreceptor exhibited a staining pattern identical with that of rods. These results indicate that the immunocytochemical approach can be used to reveal photoreceptor-specific neural connections in the sturgeon retina.

Spectral characteristics of photoreceptors and horizontal cells in the retina of the Siberian sturgeon Acipenser baeri Brandt.

In the retina of Siberian sturgeon, three spectral classes of photoreceptors were identified by microspectrophotometry. These were rods, oil drop-containing and oil drop-free cones possessing P549, and oil drop-containing cones possessing P613 and P465. With intracellular recordings, rod-driven, cone-driven, and mixed horizontal cells of luminosity type were found, as well as color-opponent horizontal cells of, at least, 6 kinds. Biphasic R/G cells received hyperpolarizing input either from rods or from green cones; in R/B cells, it was from blue cones. Other three types comprised biphasic G/B (or Y/B), RG/B, and triphasic G/BR cells. So the Chondrostean retina has the color-processing circuitry common for all ray-finned fishes.

[A simple highly sensitive recording microspectrophotometer]. / Prostoi vysokochuvstvitel'nyi registriruiushchii mikrospektrofotometr.

A design of the recording microspectrophotometer is described. The instrument possesses an absolutely flat base line and quantum-noise limited detection threshold. Two principal elements of the design are the "jumping" stage, and the logarithmic amplifier with the phase-sensitive detector which converts the photomultiplier output into the optical density signal. The performance of the instrument is illustrated by the recordings of visual pigment spectra in single photoreceptors.

Microspectrophotometric study of visual pigments in five species of geckos.

Photoreceptors and visual pigments were studied by light microscopy and microspectrophotometry in geckos Teratoscincus scincus, Gymnodactylus russovi, G. caspius, G. fedchenkovi and G. kotschui. Type A single, type B double and the thicker members of type C double cells were found to contain a green-sensitive visual pigment with the maximum absorption at 534-537 nm. Blue-absorbing pigment (lambda m = 446-460 nm) was only found in the thinner members of type C doubles.

[Role of cellular organoids in photoreceptor optics (studies on microwave models)]. / Rol' kletochnykh organoidov v optike fotoretseptorov (issledovanie na SVCh-modeliakh).

Action of the refracting structures of the photoreceptor inner segment on the receptor directional sensitivity was studied with the microwave models. Models of photoreceptor cells enlarged by 15 000 times were made of polystyrene foam and irradiated by microwaves (5.7-8.3 mm). Focusing structures (cone ellipsoid and oil drop) increase the power propagating along the photoreceptor outer segment when illuminated axially. However, they sharply increase the directionality of the cell, so that there is no overall gain in sensitivity in the case of a large pupil. It is supposed that the main role of the focusing structures is to narrow the directional sensitivity curve of the photoreceptor, to decrease the effects of the scattered light and to increase the depth of the focus.

[The growth of axons in the periphery after a decrease in the quantity of nerve cells in sympathetic ganglia]. / Rost aksonov na periferii posle umen'sheniia kolichestva nervnykh kletok v simpaticheskikh gangliiakh

The amount of cells in stellate ganglia of rat was decreased by chemical sympathectomy to 30% of the normal amount. At the age of two months sympathectomized rats have no pressor reflexes to asphyxia and femoral nerve stimulation. These responses are restored at the age of four months. The electron-microscopic and fluorescence-microscopic data show that the growth of axons in the remaining adrenergic neurons of sympathectomized animals takes place at the age between two and four months.

[Age changes in rat vasomotor reflexes and sympathetic neuron ultrastructure following chemical sympathectomy]. / Vozrastnye izmeneniia vazomotornykh refleksov i ul'trastruktury simpaticheskikh neironov u krys posle khimicheskoi desimpatizatsii

Prolonged administration of guanethidine (20 mg/kg) to newborn rats caused a marked reduction in the number of cells in stellate ganglia. The administration of guanethidine for 14 days decreased the amount of cells to 30% of the normal (partial sympathectomy), and for 28 days--to 0.5% (complete sympathectomy). At the age of two months the blood pressure pressor reflexes to asphyxia and femoral nerve stimulation were absent in both groups of the sympathectomized animals. These responses, however, were restored in the partially sympathectomized animals at the age of four months. No restoration took place in the completely sympathectomized animals. The electron microscopic studies of neurons in the partially sympathectomized animals showed the presence of a great number of neurofibrils. According to literature data this fact was typical of cells in which an active growth of axon fibers took place.