Triple cones found in retinas of 3 fish species.

Triple cones were found in the retinas of 3 species of fishes indigenous to the Woods Hole area. The function of these triple cones can not be deduced from the behavior patterns of these fishes.     

Tracts of putative ultraviolet receptors in the retina of the two-year-old brown trout (Salmo trutta) and the Atlantic salmon (Salmo salar)

We previously showed that the brown trout possesses UV-sensitive cones in its retina that are lost in 2-year-old fish. However, present investigations reveal that in the narrow growth zone along the periphery and the ventral embryonic fissure, the formation of these cones continues in trout and salmon.     

Biochemical compartmentation of fish tissues. II. Nonspecific phosphomonoesterases in brain.

The specific activities of acid and alkaline phosphatases in different regions of the brain of 9 nutritionally important fishes were worked out. The region consisting of pituitary, hypothalamus and thalamus showed the highest acid and alkaline phosphatase activities. Least activities of both the enzymes were found in the cerebellum and medulla oblongata. The piscivorous fishes contain the highest acid and alkaline phosphatase activity followed by cat fishes and major carps. The distributional pattern of these 2 enzymes in 4 regions of the brain of 9 fishes is the same.     

Dense core vesicles in cerebral cortex of the human fetus.

The present study clearly demonstrates that by the 15th week of gestation dense core vesicles appear within the human cerebral cortex. These vesicles can be identified within axon cylinders, axon growth cones, and axon synaptic terminals. The role of these vesicles is speculative, yet, their very presence at this early fetal stage seems to reflect an advanced state of synaptic vesicle development.     

Cone myoid elongation and rod myoid contraction are inhibited by colchicine in the trout retina

Summary Retinal photoreceptors of lower vertebrates undergo photomechanical changes (elongation or shortening) in response to light or dark. Colchicine, a microtubule-disrupting drug, blocks cone, but not rod elongation. Instead, rod shortening is blocked by this drug, thus suggesting that different mechanisms mediating these responses are involved in rods and cones.Acknowledgments. This work was supported by a grant from the Quebec Ministry of Education (FCAC). We thank Carole Marullo for technical assistance.     

The vertebrate connexin family

Connexins are chordate-specific transmembrane proteins that can form gap junctional channels between adjacent cells. With the progress in vertebrate genome sequencing, it is now possible to reconstruct the main lines in the evolution of the connexin family from fishes to mammals. Four connexin groups are only found in fishes. Otherwise, the differences between fishes and mammals can be explained by two gene losses (Cx39.9 and Cx43.4) after the divergence of the Reptilia, and three gene duplications (the generation of Cx26 and 30 from a preCx26/30 sequence, Cx30.3 and 31.1 from a preCx30.3/ 31.1 sequence, and Cx31.3 from an uncertain origin). Orthologs of most connexins can be found throughout the vertebrates from fishes to mammals. As judged from the recently defined connexins in tunicates, the original connexin might be related to the ortholog groups of Cx36, 39.2, 43.4, 45 or 47. Received 1 December 2005; received after revision 8 January 2005; accepted 31 January 2006     

Neuronal growth cone migration

The neuronal growth cone is a semi-autonomous portion of the developing neuron that is highly specialized for motile activity. Migrating neurons may share some features with neuronal growth cones. I review some of what has been learned about growth cone initiation, the differentiation of axons and dendrites, the role of the cytoskeleton in motility, the movements of membrane vesicles, the factors regulating the rate and direction of growth cone movement, and the further differentiation of growth cones as they enter the target area and initiate synaptogenesis. Where appropriate, I draw comparisons to what is known about the migration of neurons.     

Primitive actimoterigian fishes can synthesize ascorbic acid

Amphibians and reptiles evolved with the capacity to synthesize ascorbic acid. Some higher vertebrates, like bats, guinea pigs, primates, and humans have lost the microsomal enzyme gulonolactone oxidase, and in cases of ascorbic acid deficiency suffer from symptoms of scurvy. The question of whether the capacity to synthesize ascorbate is also present in lower vertebrates could throw light on the evolution of this pathway. In order to find out whether ascorbic acid synthesis took place in two primitive Actinopterigian fish, the paddlefish (Polydon spathula) and the white sturgeon (Acipenser transmontanus) were fed with a scorbutogenic diet or diet(s) supplemented with a graded level of ascorbic acid. We found no growth depression nor external symptoms of scurvy, which would be pronounced in modern bony fishes (Teleostei) under similar conditions. The tissue level of ascorbate in both these primitive species indicated that vitamin C in intestine and liver is not depleted when fed a scorbutogenic diet. Gulonolactone oxidase activity was found in the kineys of the Actinopterigian fishes. Thus, I question the accepted evolutionary pathway for ascorbic acid biosynthesis in lower vertebrates and suggest that the modern bony fishes,Teleostei, lost their ability to express the gulonolactone oxidase genes after they had separated during the Silurian from their common ancestor with the coelacanths (Latimeria) and Dipnoi.     

Ultrastructure and biochemistry of the pineal organ in deep-sea lanternfishes (Myctophidae)

Pineal structural and biochemical adaptations in lanternfishes included: 1) few photoreceptor outer segment discs; 2) conventional synapses between photoreceptors and pineal neurons; and 3) low levels (0-60 pg/pineal) of serotonin compared to those (greater than 1.0 ng/pineal) in the goldfish pineal organ. These findings suggest reduced photosensory and/or neuroendocrine functions in these deep-sea fishes.     

Ultrastructure and biochemistry of the pineal organ in deep-sea lanternfishes (Myctophidae)

Summary Pineal structural and biochemical adaptations in lanternfishes included: 1) few photoreceptor outer segment discs; 2) conventional synapses between photoreceptors and pineal neurons; and 3) low levels (0–60 pg/pineal) of serotonin compared to those (>1.0 ng/pineal) in the goldfish pineal organ. These findings suggest reduced photosensory and/or neuroendocrine functions in these deep-sea fishes.     

Influence de la salinité sur la respiration tissulaire chez les Téléostéens

Summary Respiratory measurements by the Warburg method were performed on hepatic, renal and branchial tissues extracted from fishes (tench and eels), kept in either salt or fresh water. The oxygen consumption of hepatic tissues of both tench and eels increased when the fishes were transferred from fresh to salt water. No difference was observed for renal and branchial tissues.     

Intermediate targets and segmental pathfinding

Neurons must often extend axons over fairly long distances, making multiple changes in their trajectory of growth before arriving at their final target. It has become clear that as growth cones navigate these complex projections, they typically extend toward a number of intermediate targets before they contact their final target. Recent work from a variety of systems has identified intermediate targets that seem to play similar roles in vertebrate and invertebrate nervous system development. From these examples it appears that a general model of axon guidance can be proposed whereby neurons are guided to their targets segmentally. Within each segment, an intermediate target appears to be the primary target for growth cone recognition and thus the completion of the journey to the final target is determined by a series of successful segmental pathfinding decisions.     

Aktivität Eiweiss spaltender Enzyme in Fischen

Summary Fresh tissues from sea fishes show much higher activities of cathepsins than the corresponding mammalian tissues. The significance of these findings is discussed. There is no indication for the presence in fresh extracts of fish muscle of either proteinases with a pH optimum near neutrality or of decarboxylases for glutamic and aspartic acids. The activities of glycylglycine dipeptidase in fish muscle are found to be at the upper limit of the values obtained by other workers with mammalian tissues.     

The underwater electro-olfactogram: A tool for the study of the sense of smell of marine fishes

Summary Recording the olfactory receptor activity of marine fishes presents problems due to the shunting of the electrical signals by the highly conductive sea water, which results in significant signal loss. By recording the large signal-to-noise ratio D. C. potentials using the underwater electro-olfactogram (EOG), we were able to study olfactory receptor properties of freshwater and marine fishes in a comparable manner.This work was supported by grants from the National Institutes of Health, Nos. NS-08814 and NS-05258.     

Telodendrial contacts between foveolar cone pedicles in the human retina

The synaptic pedicles of foveolar cones in the human retina contact each other by means of telodendrial processes. Thus direct lateral coupling of photoreceptor terminals exists even in the area of highest acuity function.     

Ein (M,F)-Problem mit Nebenbedingungen

Summary In a former publication, the problem could only be solved under two restrictions. Proof is now given that the cones are extremal in the whole of class I.     

Phyletic affinities among Polystomatidae (Monogenea)]

The chaetotaxy and ciliated cells in two Monogenean larvae of marine fishes are described for the first time: a Monopisthocotylea Diplectanum aequans (Wagener, 1857) Diesing, 1858 parasite of Dicentrarchus Labrax (L) and a Polyopisthocotylea, Microcotyle mormyri Lorenz, 1878 parasite of Pagellus mormyrus (L). A comparative study with the known larvae shows evidence of two larval types in the Monogenea of fishes, related to the two great phyla of the class: the Monopisthocoytylea and Polyopisthocotylea. The Polystomatidae, Monogenea from Amphibia and Chelonia, belong to the Polyopisthocotylea on account of their larval chaetotaxy. But the proximity of the Polystomatidae with the Tetraonchidae, within the Polyonchoinea Bychowsky, 1975 is not confirmed.     

Ein (M,F)-Problem

Summary The proof of the problem which was studied in a former work, was now brought to an end: that among all convex rotatory bodies of the constant lengthsl the cones possess the smallest surfaces ifM is given.     

Biochemical and environmental perspectives on nitrogen metabolism in fishes

Catabolism of nitrogen-containing substances makes a major contribution to the oxidative metabolism in teleostean fishes. In this review, we focus on aspects of the formation, transport, detoxification and excretion of the two most important nitrogenous products of fishes: ammonia (NH₃ plus NH ₄ ⁺ ) and urea. While NH ₄ ⁺ makes up the bulk of nitrogenous waste, it is in equilibrium with the highly toxic NH₃. Ammonia is generated in the liver and excreted through branchial, surface and renal routes. Innocuous urea is derived through hepatic uricolysis or argininolysis and voided through kidney, gill, skin or faeces. Under conditions hampering the release of ammonia, such as exposure to exogenous ammonia, water limitation, or alkaline conditions, some teleosts detoxify ammonia through synthesis of urea by the ornithine-urea cycle in liver. Ammonia and possibly alanine are the prevalent vehicles of internal nitrogen transport. Glutamine is immaterial to interorgan nitrogen transport in fishes, but plays a transient role in the detoxification of ammonia by brain glutamine synthetase.     

Occurrence of carotid labyrinth in the catfish group of teleost fishes

Summary A structure similar in topography and morphology to the carotid labyrinth of amphibians has been found in 4 catfishes, namely,Clarias batrachus, Heteropneustes fossilis, Rita rita andMystus seenghala. The present finding of the presence of the carotid labyrinth in fishes is the first report, and the results are discussed in the light of the amphibious habit of these catfishes.We are grateful to Prof. U.S. Srivastava for providing laboratory facilities and for encouragement. The work was financially supported by the S.C.S.T., U.P. which is thankfully acknowledged.