Pituitary response to environmental osmotic changes in the larval guppy,Lebistes reticulatus (Peters)

Summary The pituitary of the larval guppy, Lebistes reticulatus (Peters), was investigated cytologically in relation to the osmotic properties of the environment. In larvae of Stage I, removed from the mother about one week before birth, the sizes of the nuclei of the prolactin, STH, ACTH, and pars intermedia cells were small. The nuclei of these cell types became larger when Stage I larvae were transferred into fresh water (F. W.); however, these animals did not survice. In Stage-II larvae, removed from the mother just before birth, the nuclei of the abovementioned adenohypophysial cells were larger than those of the Stage-I larvae. Stage-II larvae were able to survive in F. W. Thus, it seem that osmoregulatory mechanisms in the larval guppy develop between Stages I and II.The nuclei of prolactin, STH, ACTH and pars intermedia cells decreased significantly in size after birth (0-hr). When larvae of the 0-hr group were immersed in 1/3 sea water (S. W.), only the nuclei of the ACTH cells increased in size. The neurohypophysis of Stage-I larvae contained a very small amount of aldehyde-fuchsin (AF)-positive material, while the neurohypophysis of Stage-II and 0-hr fish was rich in this material. When Stage-I larvae were immersed in F. W., the neurohypophysis showed as great an accumulation of AF-positive material as Stage-II and 0-hr fish.Supported by grants from Japan Society for Promotion of Science and from Ministry of Education of Japan to Professor Kobayashi, and by grants from the Deutsche Forschungsgemeinschaft to Professor Oksche. A part of this investigation was effected while Professor Kobayashi held a Visiting Professorship at the University of Giessen. We are indebted for histological assistance of Miss I. Woltmann, Mrs. H. Schneider and Mrs. T. Bremer.     

Mitotic and pigment-translocating activities of cultured chromatophores of the guppy, Lebistes reticulatus

Using Ham's F-12 medium, an in vitro culture system permitting cellular survival for over 6 months has been developed for the chromatophores of the guppy. In this culture system, the various types of chromatophores (melanophores, erythrophores and xanthophores) migrated out of the explanted tail fin tissue, retained their pigmentation, and displayed both mitotic and pigment-translocating activities. The mitotic activity was evident during the first 3 or 4 weeks in culture, whereas the pigment-translocating ability persisted for 16 weeks. The cultured chromatophores of male fish displayed pigment aggregation in response to adrenergic agents (epinephrine and norepinephrine) and pigment dispersion in response to alpha-melanocyte stimulating hormone (alpha-MSH), cyclic AMP and dibutyryl cyclic AMP. Cyclic GMP did not elicit pigment-translocating responses in any of the chromatophores.     

Myopathy and steatitis in the common guppy, Poecilia (Lebistes) reticulata (Peters)

There was 1% mortality among female guppies just imported from Southeast Asia. Moribund fish showed discoloration, lethargy and kyphosis. Microscopically, myopathy and steatitis were observed, together with an extensive ceroid storage. These findings are indicative of vitamin E deficiency, and illustrate the risk of using fish of unknown origin in toxicological studies.     

Development of spontaneous motility in the guppy embryo (Lebistes reticulatus) and the effect of spinal transection

Guppy (Lebistes reticulatus) embryos pass through a distinct sequence of motor behaviors that leads to swimming capability during the course of their development. We have characterized these activities in order of appearance, with several corresponding morphological features, as belonging to the coil stage, tail-twitch stage, S-movement stage, and swimming stage. A primary feature of development was an increase in the amount of activity per unit of time over these four stages. The developmental pattern of motility was not interrupted by spinal transection until the onset of swimming, implying that supraspinal information is not required for the occurrence of the primitive behaviors that precede swimming. Elimination of swimming by spinal transection did not elicit a reversion to less complex activities, suggesting that once the cerebral control for swimming is developed, it represents a hardwired system not behaviorally reducible to antecedent components.     

Electron microscopy of two types of reflecting chromatophores (iridophores and leucophores) in the guppy,Lebistes reticulatus Peters

Summary Reflecting chromatophores in the integument of the guppy, Lebistes reticulatus Peters, are of two distinct types, iridophores and leucophores. The iridophores are smaller and fixed, producing a metallic iridescent color. The cytoplasmic organelles involved in the coloration of iridophores are the reflecting platelets, as in the iridophores of other fish and amphibian species on which earlier reports have been made. Spherical granules of pleiomorphic internal structure, quite variable in size but generally 0.2 m to 1.0 m in diameter, are also numerous in the iridophores. The nature of these granules remains unknown.The leucophores are larger, and highly dendritic; their pigment granules are migratory and they exhibit a dull whitish color. Pigment granules of the leucophores are spherical in form, varying from 0.5–0.8 m in diameter, with a double membrane enclosing the internal fibrous materials. Melamine-treatment of the fish caused degenerative changes in the pigment granules and also the other cytoplasmic organelles of the leucophores, whereas the other kinds of chromatophores, including the iridiophores, remained intact. Some problems in general characterization and classification between these two types of chromatophores were discussed.The author wishes to thank Mr. Yoshiro Yamazaki for his assistance in operating the electron microscope, and Dr. Takao Kajishima (Biological Institute, Nagoya University) for his encouragements     

Expression of H-Y Antigen in the Guppy (Lebistes reticulatus)

Expression of a mammalian cross-reactive H-Y antigen on the surface of cells derived from the male guppy ( Lebistes reticulatus ) is demonstrated. This finding further establishes the evolutionary conservation of H-Y antigen among lower vertebrates and provides a basis for speculation on the possible evolutionary association between H-Y antigen and sex determination.     

Some preliminary studies of the effects of a static magnetic field on the life cycle of the Lebistes reticulatus (guppy).

Lebistes reticulatus (guppy) was subjected to a continuous treatment of a 500-G homogeneous magnetic field within a specially designed horseshoe magnet encompassing a small aquarium. The experiment was carried through several generations with the following results: in the first generation, the brood size was normal but the gestation period was reduced by 30%; the second generation had an average reduction of spawn rate of 50% and a reduction of the gestation period of 30%; and in the third generation, reproduction was completely inhibited as long as the fish remained within the magnetic field.     

Juxtanuclear changes during the early spermatogenesis in Lebistes reticulatus (Guppy)

Summary The sperm cell of Lebistes reticulatus during Spermatogenesis is studied. The nuclear differentiation correlate to the flagellar outgrowth. Differential distribution in the chromatin condensation corresponds to a new membrane synthesis at the centriolar side of the nucleus. The fan-shaped microtubular bundle in Juxtanuclear position is described and its function as a stabilizing entity is discussed. At the centriolar complex satellites and an intercentriolar lamellated body are investigated. In submicroscopic details the sperm cell of Lebistes distinctively differs from other species previously described.The present investigation was supported by a grant from the Pehr Oscar Klingendahl Foundation.The authors wish to thank Mr. Mauri Nyholm, M. Sc., for his technical advices and Miss Maria Sjöstedt for preparing the specimens.     

Structure of the pineal organs of Anguilla anguilla L. and Lebistes reticulatus Peters (Teleostei)

Résumé Des fibres myocardiques ventriculaires de Rat et des fibres squelettiques rapides des orteils de Grenouille ont été examinées en microscopic électronique après imprégnation par le nitrate de Lanthane ou après traitement par l'acide phosphotungstique.Le nitrate de Lanthane a été utilisé comme marqueur d'espace extracellulaire. Dans le tissu myocardique, it est possible de l'observer dans toutes les ramifications du système T, alors que dans les fibres squelettiques, le glutaraldehyde du mélange fixateur provoque l'obturation de la plupart des tubules et empêche sa pénétration dans leur lumière. Dans tous les cas, cependant, la diffusion du Lanthane s'arrête à 50 Å environ du feuillet externe des membranes plasmatiques ou tubulaires.Le matériel mis en évidence par l'acide phosphotungstique, comportant vraisemblablement des polysaccharides et des glyco-protéines, est localisé à la périphérie de toutes les cellules examinées, y compris dans l'espace de 50 À où ne pénètre pas le Lanthane. Dans les fibres myocardiques, ce matériel est présent de plus dans l'ensemble du système T, mais dans les fibres squelettiques, par contre, il est présent dans les parties intermédiaires et terminales du système L.Il semble que la diversité de localisation et de nature des polyanions présents dans ces deux types de fibres musculaires striées puisse suffire à rendre compte d'un certain nombre de propriétés spécifiques de chacun d'eux.

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Comparative study on physico-chemical properties of the t-system and sarcoplasmic reticulum in two types of striated muscle fibers: the fast muscle fiber of the frog and the myocardial fiber of the rat ventricle

Summary Rat ventricular myocardial fibers and frog toe fast skeletal fibers were examined electron microscopically after Lanthanum nitrate impregnation or after phosphotungstic acid staining.The Lanthanum nitrate was used as an extracellular tracer. In the myocardial tissue, it is possible to observe it in all the T system ramifications, while in the skeletal fibers, the glutaraldehyde fixative elicits the sealing of most tubules and prevents Lanthanum from penetrating into their lumen. In both cases, however, the Lanthanum diffusion stops at about 50 Å from the external plasma membrane layer.The material stained with phosphotungstic acid, probably including polysaccharides and glycoproteins, is localized at the surface of both cell types examined here, even in the 50 Å space where Lanthanum does not penetrate. In the myocardial fibers, this material is also present in the whole T system, but in the skeletal fibers, on the contrary, it is present in the intermediate and terminal parts of the L system.The diversity in localization and nature of the polyanions present in these both types of striated muscular tissue seems to be sufficient to explain some functional properties specific of each of them.

Travail réalisé dans le cadre du programme de recherches de l'équipe associée au C.N.R.S. n 111.