Transgenesis in fish

Gene transfer into fish embryo is being performed in several species (trout, salmon, carps, tilapia, medaka, goldfish, zebrafish, loach, catfish, etc.). In most cases, pronuclei are not visible and microinjection must be done into the cytoplasm of early embryos. Several million copies of the gene are generally injected. In medaka, transgenesis was attempted by injection of the foreign gene into the nucleus of oocyte. Several reports indicate that the injected DNA was rapidly replicated in the early phase of embryo development, regardless of the origin and the sequence of the foreign DNA. The survival of the injected embryos was reasonably good and a large number reached maturity. The proportion of transgenic animals ranged from 1 to 50% or more, according to species and to experimentators. The reasons for this discrepancy have not been elucidated. In all species, the transgenic animals were mosaic. The copy number of the foreign DNA was different in the various tissues of an animal and a proportion lower than 50% of F1 offsprings received the gene from their parents. This suggests that the foreign DNA was integrated into the fish genome at the two cells stage or later. An examination of the integrated DNA in different cell types of an animal revealed that integration occurred mainly during early development. The transgene was found essentially unrearranged in the fish genome of the founders and offsprings. The transgenes were therefore stably transmitted to progeny in a Mendelian fashion. Southern blot analysis revealed the presence of possible junction fragments and also of minor bands which may result from a rearrangement of the injected DNA. In all species, the integrated DNA appeared mainly as random end-to-end concatemers. In adult trout blood cells, a small proportion of the foreign DNA was maintained in the form of non-integrated concatemers, as judged by the existence of end fragments. The transgenes were generally only poorly expressed. The majority of the injected gene constructs contained essentially mammalian or higher vertebrates sequences. The comparison of the expression efficiency of these constructs in transfected fish and mammalian cells indicates that some of the mammalian DNA sequences are most efficiently understood by the fish cell machinery. Chloramphenicol acetyl transferase gene under the control of promoters from Rous sarcoma virus, and human cytomegalovirus, was expressed in several tissues of transgenic fish. Chicken -crystallin gene was expressed in several tissues of transgenic fish. Rainbow trout growth hormone cDNA driven by the Rous sarcoma virus promoter was expressed in transgenic carps leading to a faster growth of these animals. The antifreeze protein gene from flounder was expressed in transgenic salmon. These data indicate that transgenesis in fish is relatively easy but that fish gene sequences must be preferably used to obtain a good expression of the transgenes. Fish is a good biological model, specially for developmental studies and it is an increasing part of human food. For these reasons, transgenesis in fish is most likely to be more and more practised in the coming years.     

Electro-actography in fresh-water fish

Zusammenfassung Es wird eine Methode beschrieben, das Aktogramm von Fischen und anderen Süsswasserbewohnern zu bestimmen aufgrund der vom Autor entdeckten, von diesen Organismen erzeugten äusseren schwachelektrischen Felder.     

Reliability of intraperitoneal injections in fish

Résumé L'hormone thyréotrope¹²⁵I fut injectée en doses variées dans le péritoine de Cyprins. Les pertes de substance par écoulement dépassèrent le 50% des doses. Les meilleures rétentions furent obtenues avec de petits volumes, injectés à travers l'intestin, après bouchage du cloaque avec du liquide silicone.     

Acoustic localization in an ostariophysian fish

Summary Under approximate free field conditions acoustic localization could be demonstrated in an ostariophysian fish, the ide (Leuciscus idus). The efficient vibration links of both sacculi with the unpaired swimbladder (via the Weberian ossicles) do apparently not preclude directional hearing in this important group of freshwater fish.The authors gratefully acknowledge the efforts of Mr M. Kleisma in the conduction of preliminary laboratory and field experiments. We thank Dr J. Ringelberg for making available to us the field facilities of the Limnological Laboratory, University of Amsterdam. Dr E. Meelis, Institute of Theoretical Biology, Leyden, has checked the applied statistics.     

Temperature acclimation and learning in fish

Summary Control fish acclimated at 21°C learned to swim upright following the attachment of floats to their ventral surfaces, while fish acclimated at both 5°C and 33°C failed to learn the swimming skill. Fish previously acclimated at 5°C and then transferred to 21°C 48 h before the task, learnt the swimming skill better than the control fish, but fish acclimated at 33°C and transferred to 21°C failed to acquire the new skill. Acclimation temperature, therefore, significantly modifies the learning behaviour of fish.     

Changes induced by manganese in fish testis

Summary Exposure ofColisa fasciatus, a freshwater teleost, to 2500 mg/l manganese sulphate for 90 h caused decreased spermatogenic activity and hemorrhage in the testes.     

Occurrence of synapses in olfactory epithelium of fish

Zusammenfassung Nachweis von Synapsen in der Riechschleimhaut des FischesChanna punctatus, die als Verbindung zwischen primärer und sekundärer Riechzelle aufgefasst werden.

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We wish to thank Dr.Rameshwar Singh, our colleague in this department, for his helpful suggestions.     

Autoradiographic studies of yolk nucleus in fish oocytes

Résumé L'expulsion de la matière nucléolaire dans les ufs du poisson est étudiée ici par autoradiographie. Employant la cytidine-H₃, nous avons vu que le RNA nucléolaire passe dans le cytoplasme sous forme diffuse, et non comme un nucléole complet appelé « noyau-jaune ».

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I wish to thank Dr.D. J. Fluke and Dr.H. S. Roberts for the supply of autoradiographic material.     

Gamma-aminobutyric acid (GABA) in fish erythrocytes

Zusammenfassung Nachweis, dass-Aminobuttersäure und Taurin bei den 3 verwandten Plattfischarten Flunder, Scholle und Kliesche die wichtigsten intraerythrozytären freien Aminosäuren sind.

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This work supported by the Nasen Foundation (Norway) and the Norwegian Research Council for Science and the Humani ties (NAVF).     

Shedding by rod photoreceptors after sunrise in fish

Diurnal shedding by retinal rods was studied in wild cutthroat trout,Oncorhyncus clarki, hatchery rainbow trout,Oncorhyncus mykiss, and the plains killifish,Fundulus zebrinus, by counting the shed tips of rod outer segments ingested as phagosomes by pigment epithelial cells. After sunrise, phagosomes increased in all species, but fewer occurred in trout, and these were elevated from 3 to 9 hours after sunrise. Shedding occurred earlier in the light period and was more robust in killifish, with phagosomes elevated from 1.5 to 6 hours after sunset. The data suggest that both production of phagosomes by shedding and their subsequent disposal are slower at the lower temperatures experienced by trout. Otherwise, rod shedding produced under natural lighting is not appreciably different than that provoked by sudden onset of artificial light.