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.     

Freeze fracture studies of reaction centers from Rhodospirillum rubrum in chromatophores and liposomes

In freeze-fractures of chromatophores of Rhodospirillum rubrum the reaction centers are seen as hexagonal arranged particles of 13 nm diameter with a density of around 5,500 particles per m². Similar regions on the cytoplasmic membrane suggest that these parts are the prospective invagination sites.Isolated reaction centers are easily incorporated into liposomes. In freeze fractures of liposomes particles similar in shape and size, although less dense as in chromatophores are observed. In negative staining much smaller units of only 5 nm in diameter are found indicating that reaction centers occur in the membrane as tri- or tetramers. There is a strong correlation between particle density in chromatophores and titratable reaction centers remaining in these membranes after extraction of reaction centers by detergents; both values are in good agreement with the yield of reaction centers at a given detergent concentration.Abbreviations LDAO Lauryldimethylamine oxide - PF protoplasmic fracture face - EF exoplasmic fracture face     

Effect of sex and size on copper susceptibility of the common guppy, Lebistes reticulatus (Peter)

Multiple regression analyses were conducted to relate rate of toxic action, body weight and concentration for fry, male and female populations of Lebistes reticulatus exposed to copper solutions. For each of these three populations, copper susceptibility decreased as body weight increased. On the basis of the rate of toxic action adjusted with the size factor, the copper susceptibility differed significantly among the fry, male and female populations at the ratios of 2.20:1.55:1.00. When the size factor was not included in calculation, the rate of toxic action or median survival time did not show such a difference between the males and females.     

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.     

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.     

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.     

Electron microscopy of beef heart mitochondrial F1-ATPase

The quaternary structure of isolated and membrane-bound F1-ATPase (submitochondrial particles) has been studied by electron microscopy. A model of the molecule has been proposed: six protein masses are arranged in two layers approximately at the vertices of a triangular antiprism. Computer averaging of the images showed that the frontal view of the molecule can be approximately characterized by mirror plane symmetry.     

Electron microscopy morphology of the mitochondrial network in human cancer

Mitochondria have been implicated in the process of carcinogenesis, which includes alterations of cellular metabolism and cell death pathways. The aim of this review is to describe and analyze the electron microscopy morphology of the mitochondrial network in human cancer. The structural mitochondrial alterations in human tumors are heterogeneous and not specific for any neoplasm. These findings could be representing an altered structural and functional mitochondrial network. The mitochondria in cancer cells, independently of histogenesis, predominantly are seen with lucent-swelling matrix associated with disarrangement and distortion of cristae and partial or total cristolysis and with condensed configuration in minor scale. Mitochondrial changes are associated with mitochondrial-DNA mutations, tumoral microenvironment conditions and mitochondrial fusion–fission disequilibrium. Functionally, the structural alterations suppose the presence of hypoxia-tolerant and hypoxia-sensitive cancer cells. Possibly, hypoxia-tolerant cells are related with mitochondrial condensed appearance and are competent to produce adequate amount of ATP by mitochondrial respiration. Hypoxia-sensitive cells are linked with lucent-swelling and cristolysis mitochondria profile and have an inefficient or null oxidative phosphorylation, which consequently use the glycolytic pathway to generate energy. Additionally, mitochondrial fragmentation is associated with apoptosis; however, alterations in the mitochondrial network are linked with the reduction in sensitivity to apoptosis induces and/or pro-apoptotic conditions. Pharmacological approaches designed to act on both glycolysis and oxidative phosphorylation can be considered as a new approach to selectively kill cancer cells.     

Electron microscopy of the indoleamine-accumulating neurons in the retina of the rabbit

Summary The recently discovered indoleamine-accumulating retinal neurons were studied electron microscopically after destruction of the dopaminergic retinal neurons and subsequent labeling with 5,6-dihydroxytryptamine. These observations confirm earlier fluorescence microscopical studies on the distribution of the indoleamine-accumulating neurons in the rabbit retina. Their perikarya are known to be located in the inner nuclear layer (INL) among the amacrine cell bodies. Their processes are found only in the inner plexiform layer (IPL), most of them in the innermost third part of that layer. The indoleamine-accumulating terminals are pre- and postsynaptic to bipolar neurons in the innermost sublayer of the IPL. Reciprocal synapses are probably the rule. The synaptic vesicles of indoleamine-accumulating synapses onto bipolar cells are arranged in globular clusters around a central electron dense, round body. A number of synapses formed by unlabeled amacrine neurons with postsynaptic indoleamine-accumulating elements were also detected. These synapses were mainly found in the outermost third of the IPL. Synaptic contacts between presynaptic indoleamine-accumulating neurons and postsynaptic unlabeled processes of amacrine cells are very rare.     

Ultrastructural changes in the spermatogonia and spermatocytes of Poecilia reticulata during spermatogenesis

Summary The structure of guppy (Poecilia reticulata) spermatogonia and spermatocytes has been studied using electron microscopy. The spermatogonia, situated at the apex of the seminiferous tubule, are almost all surrounded by a network of Sertoli cells; they have very diffuse chromatin and one or two large nucleoli. The cytoplasm contains relatively few organelles, although annulate lamellae are found. The mitochondria have few cristae and are concentrated at one pole of the cell; they are sometimes found with intermitochondrial cement. These spermatogonia are separated from each other, having no intercellular bridges or inclusion in Sertoli cells, and are relatively undifferentiated; they correspond to stem cells. The spermatogonia beneath the apex are organized into cysts. First-generation spermatogonia are more dense and heterogeneous, their nuclei becoming smaller and their chromatin becoming denser during successive generations. In spermatocytes, the synaptinemal complex exists as a modified form until metaphase. The concentration of organelles in the cytoplasm increases and the organelles become more diversified as spermatogenesis progresses. Many cytoplasmic bridges are observed (several per cell), indicating that the cells remain in contact after several divisions. These changes in germ cell structure have been related to some of the characteristic features of spermatogenesis in guppy, e.g. the large number of spermatogonial generations and the complexity of spermiogenesis.     

Electron microscopy of glycogen degrading enzymes

Single molecules of glycogen phosphorylase b exhibit images in the electron microscope which are similar in shape and dimension to those derived from X-ray crystallography. Phosphorylase alpha exhibits tetramers but shows dimers in the presence of glucose. Glycogen debranching enzyme appears as a monomer with an unusual crescent or shrimp-like shape, with occasional isologous aggregation to circular dimers. The longest dimension of the monomer is very similar to that of the phosphorylase dimer, 11.5 nm. Strong binding of the debranching enzyme to glycogen is readily visualized in the electron microscope. It is suggested that the distinctive shape of the debranching enzyme may be related to its catalytic function.