Identification of actin microfilaments in the neurosecretory axons of rat neural lobe]

Incubation of rat neural lobes with heavy meromyosin (HMM) after prolonged glycerination, induced characteristic arrowhead decoration of a number of microfilaments at different levels of the neurosecretory axons. In non terminal sections of axons the labelled microfilaments showed preferential relationships with microtubules in addition to occasional contacts with the axolemma and various axonal organelles. In axonal endings, they were mainly associated to microvesicles and appeared to be anchored on the axolemma facing the perivascular space at the level of membranous densifications.     

Modification of the amino-acid efflux during the osmotic adjustment of isolated axons ofCallinectes sapidus

Résumé Au cours du choc hypoosmotique, le volume d'un axone isolé d'une patte de crabe euryhalinCallinectes sapidus est rapidement régularisé. En même temps, on observe une augmentation du flux sortant de l'alanine marquée. Cette augmentation paraît être due à une modification de la membrane axonale, produite par la variation de la pression osmotique dans le milieu d'incubation.     

Adrenergic and cholinergic axons in the mouse iris

Résumé Par la comparaison entre la somme totale des fibrilles nerveuses et celle des fibres adrénergiques des cellules de Schwann de l'iris de la souris, il se confirma que les fibres adrénergiques et cholinergiques terminales sont ici en grande partie concomitantes.     

Genetics of photoreceptor degeneration and regeneration in zebrafish

Zebrafish are unique in that they provide a useful model system for studying two critically important problems in retinal neurobiology, the mechanisms responsible for triggering photoreceptor cell death and the innate stem cell–mediated regenerative response elicited by this death. In this review we highlight recent seminal findings in these two fields. We first focus on zebrafish as a model for studying photoreceptor degeneration. We summarize the genes currently known to cause photoreceptor degeneration, and we describe the phenotype of a few zebrafish mutants in detail, highlighting the usefulness of this model for studying this process. In the second section, we discuss the several different experimental paradigms that are available to study regeneration in the teleost retina. A model outlining the sequence of gene expression starting from the dedifferentiation of Müller glia to the formation of rod and cone precursors is presented.     

Modification of glutamate receptors by phospholipase A2: its role in adaptive neural plasticity

Long-term potentiation (LTP) and long-term depression (LTD) are two electrophysiological models that have been studied extensively in recent years as they may represent basic mechanisms in many neuronal networks to store certain types of information. In several brain regions, it has been shown that these two forms of synaptic plasticity require sufficient dendritic depolarization, with the amplitude of the calcium signal being crucial for the generation of either LTP or LTD. The rise in calcium concentration mediated by the N-methyl-D-aspartate (NMDA) subtype of glutamate receptors has been proposed to stimulate various calcium-dependent enzymatic processes that could convert the induction signal into long-lasting changes in synaptic structure; protein kinases and phosphatases have so far been considered predominantly with regard to LTP and LTD formation. According to several lines of experimental evidence, changes in synaptic function observed with LTP and LTD are thought to be the result of modifications of postsynaptic currents mediated by the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) subtype of glutamate receptors. Moreover, it has become apparent recently that activation of the calcium-dependent enzyme phospholipase A2 (PLA2) could be part of the molecular mechanisms involved in alterations of AMPA receptor properties during long-term changes in synaptic operation. In the present review, we will first describe the results that indicate a critical role of the phospholipases in regulating synaptic function. Next, sections will be devoted to the effects of PLA2 and phospholipids on the binding properties of glutamate receptors, and a revised biochemical model will be presented as an attempt to integrate the PLA2 enzyme into the mechanisms ( in particular kinases and phosphatases) that participate in adaptive neural plasticity. Finally, we will review data relevant to the issue of selective changes in AMPA binding after environmental enrichment and LTP.     

G-band patterns as chromosomal markers,and the interpretation of chromosomal evolution in wild sheep (Ovis)

- . Ovis musimon (2n=54) O. orientalis (2n=54) - - -O. canadensis mexicana (2n=54) O. musimon x O. canadensis ₁₂ - . ₂ 27 . - .

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Supported by National Science Foundation Grant no. GB 32114X and the Sprague Foundation. We thank Dr. T. C. Hsu for assistance in making the chromosome preparations and for advice and encouragement. The Trustees of the Rachelwood Wildlife Research Preserve generously allowed the biopsy of specimens of their custody. Mr.Arthur Popham kindly provided the specimens from Iran while Dr.R. M. Robinson obtained biopsies from the desert sheep.     

Cinephotographic superposition as a technique for the analysis of sub-cellular movement

Zusammenfassung Eine Methode zur einfachen Quantifizierung von gerichteten Bewegungen subzellularer Teile, zum Beispiel in Furchungszellen, wurde entwickelt.

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This work was financed by a grant from the Science Research Council.     

Protein renewall in the photoreceptor outer segments of the pigeon retina

Résumé Les segments externes des bâtonnets de la rétine du pigeon sont totalement renouvelés en 3–4 jours. La distinction fondamentale entre les méchanismes de renouvellement des protéines discales des bâtonnets et des cônes a éte retrouvée dans cette espèce.

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Supported by Grant No. 3287-67 from the Swiss National Found for Scientific Research.

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We thank ProfessorP. G. Waser for support and MissM. Hofmann and Mrs.E. Hofmann for technical assistance.     

Influence of sulfhydryl reagents on the structural and molecular organization of crayfish photoreceptor microvilli

Summary SDS-polyacrylamide gel electrophoresis of isolated photoreceptor membrane from crayfish compound eyes in the absence and presence of the sulfhydryl-reducing agent 2-mercaptoethanol revealed major qualitative and quantitative differences in electrophoretic behaviour of polypeptides. Two peptides of 37 and 69 KD show abnormal migration patterns under the experimental conditions, indicating a possible significance of disulfide bridges for the structural integrity of invertebrate photoreceptor membrane.     

Catecholamines and granular vesicles in adrenergic axons of the developing pineal body of the rat

Resumen Imediatemente después del nacimiento, las fibras adrenérgicas del cuerpo pineal del ratón, contienen solamente vesículas granulosas del tipo grande. Con dós dias, comienzan a aparecer las vesículas granulosas pequeñas; que son las que contienen nor-epinefrina. Se piensa que antes de ésta edad, la nor-epinefrina se localizaria principalmente en un compartimiento extra-vesicular.

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This material was presented at the meetings of the American Association of Anatomists, Kansas City, Missouri, 1967.     

Reticulate evolution and cladism: Tests for the direction of evolution

Summary Reticulate evolution between ancestral-descendant lineages can be critically tested for by investigating the relationship between out-group and mid-point roots on numerically derived cladograms. The western grass-snake provides a worked example for the theoretical test.