Rhythmic activity in frog (Rana pipiens) visual system

Zusammenfassung Nachweis, dass die Netzhaut-Ganglienzellen dritter Klasse beiRana pipiens auf Beleuchtungsperiodenausgleich reaktiv rhythmische potentialfolgen von bursts und firing erzeugen. Als wirksamste Beleuchtungsperioden erwiesen sich solche im mesopischen Bereich bei Mindestdauer von 15 sec. Weder skotopische noch photopische Belichtungen führten zu rhythmischer Aktivität.     

Effect of neonatal unilateral enucleation on the development of orientation selectivity in kitten primary visual cortex]

In normally reared Kittens (6 weeks old), all orientations encoded by visual cells in the primary visual cortex are equally represented. In Kittens of the same age, unilaterally enucleated at birth and reared in identical conditions, 70% of orientation-selective cells preferentially respond to horizontal or vertical orientations.     

Maintenance of visual cells in vitro

Résumé Des fragments de rétine et des cellules visuelles isolées de la grenouilleRana pipiens ont été cultivés dans la chambre de Rose. Bien qu'une dégénérescence morphologique des segments extérieurs des cellules visuelles ait été observée pendant la culture, le pouvoir de réfraction normal et la présence du pigment visuel ont été constatés dans ces segments, les segments intérieurs avec leurs noyaux étant conservés. Mais, l'intensité du pigment visuel a été plus faible que dans la rétine fraîche. Ces résultats montrent que la cellule individuelle du photorécepteur se prête à l'étude physiologiquein vitro.

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Aided by a grant from the National Society for the Prevention of Blindness.     

Local and target-derived actions of neurotrophins during peripheral nervous system development

Neurotrophic factors are present in limiting quantities, and neurons that obtain an adequate supply of the required neurotrophic factor survive whereas those that compete unsuccessfully die. Analysis of null mutant mice for neurotrophins and Trk receptors as well as in vivo experiments in ovo in the chick applying exogenous neurotrophins or neutralising antisera have significantly increased knowledge of the roles they play during development. This review focuses on recent advances in understanding the various roles of neurotrophins in dorsal root ganglion sensory neuron development at different times in embryonic development - an early local role for differentiation of the sensory precursor cells and a later survival-promoting target-derived role for the mature neurons. Neurotrophic factors are present in limiting quantities, and neurons that obtain an adequate supply of the required neurotrophic factor survive whereas those that compete unsuccessfully die. Analysis of null mutant mice for neurotrophins and Trk receptors as well as in vivo experiments in ovo in the chick applying exogenous neurotrophins or neutralising antisera have significantly increased knowledge of the roles they play during development. This review focuses on recent advances in understanding the various roles of neurotrophins in dorsal root ganglion sensory neuron development at different times in embryonic development - an early local role for differentiation of the sensory precursor cells and a later survival-promoting target-derived role for the mature neurons.     

A new functional interpretation of the visual system of male scale insects (Coccida,Homoptera)

Summary In a flight position with vertical body axis, both the dorsolateral and the characteristic ventral lens eyes of male coccid insects are arranged in a horizontal ring around the head. The interpretation that they mainly serve for stabilizing the flight position with regard to the horizon can explain the extraordinary structural features known for these eyes.     

Successful visual epistemic representation

In this paper, I characterize visual epistemic representations as concrete two- or three-dimensional tools for conveying information about aspects of their target systems or phenomena of interest. I outline two features of successful visual epistemic representation: that the vehicle of representation contain sufficiently accurate information about the phenomenon of interest for the user's purpose, and that it convey this information to the user in a manner that makes it readily available to her. I argue that actual epistemic representation may involve tradeoffs between these features and is successful to the extent that they are present.     

Analysis of the immune system with transgenic mice: T cell development

Transgenic mice carrying functionally rearranged T cell receptor genes have contributed significantly to our knowledge of T cell development and thymic positive and negative selection processes. In addition, TCR-transgenic mice have been used to investigate mutations affecting thymocyte development, like scid and lpr. Gene targeting by homologous recombination will allow to analyze more specifically the molecular mechanisms underlying thymic selection and peripheral tolerance.     

Analysis of the immune system with transgenic mice: T cell development

Transgenic mice carrying functionally rearranged T cell receptor genes have contributed significantly to our knowledge of T cell development and thymic positive and negative selection processes. In addition, TCR-transgenic mice have been used to investigate mutations affecting thymocyte development, likescid andlpr. Gene targeting by homologous recombination will allow to analyze more specifically the molecular mechanisms underlying thymic selection and peripheral tolerance.     

Involvement of circadian system in photoperiodic control of pubertal development in female deer mice,Peromyscus maniculatus

Summary Pubertal development in female deer mice,Peromyscus maniculatus, was stimulated by exposure to light cycles of LD 168, LD 630 or LD 654, but not by exposure to cycles of LD 618 or LD 642. These results support the hypothesis that female deer mice use a circadian rhythm of responsiveness to light to measure photoperiodic time.This investigation was supported in part by National Science Foundation Grant PCM 8116880 and U.S. Environmental Protection Agency Grant CR809428010. H.U. is the recipient of Research Ca-reer Development Award 5 KO4 HD00276-02 from the National Institute of Child Health and Human Development.     

Interrelations of glial cells and axons in the postembryonic development of the nervous system ofTubifex tubifex

Summary Transmission electron microscopy was used to study the role of gliosomes in the postembryonic development of the central nervous system in Tubifex (Oligochaetes).     

Dopamine in the visual cortex of the cat

The endogenous content of noradrenaline (NA) and dopamine (DA) was determined by radioenzymatic assays in three different areas of the occipital (visual) cortex, in normal cats as well as in DA-deafferented animals. The use of HPLC methodology enabled us to detect and measure in addition two metabolites of DA: 3, 4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), thus confirming the existence of a DA innervation in this cortical region.     

A visual stimulus in the courtship ofDrosophila suzukii

Summary The males ofDrosophila suzukii have a specific black spot on their wings and this was surgically removed. In this situation, the males were almost normally accepted by the females when they were stored under a diurnal light-dark cycle, but they were somewhat discriminated against by the females previously exposed to continuous light.     

Moth visual potentials in response to middle UV-radiation

Zusammenfassung Das dunkeladaptierte Facettenauge vom NachtschmetterlingManduca sexta wurde mit UV-Licht mittlerer Wellenlänge (2700–3100 Å) bei niedriger Intensität bestrahlt. Der photorezeptorische Anteil des ERGs war vermindert oder verschwunden, aber nachsynaptische Wirkungen wurden beobachtet. Impulsaktivitäten wurden bei einem hauptsächlich efferenten Flugmuskelnerv ausgelöst, wenn das kontralaterale Auge beleuchtet wurde.

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This research was supported in part by a USDA-ERD research grant No. 12-14-100-7742 (33).