Dynamics of the cytoskeleton in Amoeba proteus

Fluorescein-labeled muscle actin was microinjected into Amoeba proteus and followed during intracellular redistribution by means of the image-intensification technique. The fully polymerization-competent protein becomes part of the endogenous actomyosin system undergoing dynamic changes over time periods of several hours. Single-frame analysis of long-term sequences enabled the direct demonstration of both the contractile activities and morphological transformations of microfilaments in normally locomoting, immobilized and phagocytozing specimens. In normally locomoting cells the filament layer undergoes continuous changes in spatial distribution depending on the actual pattern of cytoplasmic streaming and cell shape. The highest degree of differentiation is always maintained in the intermediate region between the front and the uroid, thus indicating this segment of the cortex to be the most important site in generating motive force for pseudopodium formation and ameboid movement. In immobilized cells contracted by the application of ruthenium red or relaxed by different anesthetics, the filament layer forms a continuous thick sheath beneath the cell surface or becomes completely disintegrated. In phagocytozing cells the local polymerization of actin at the tip of pseudopodia forming the food-cup and around the nascent phagosome points to a significant participation of the actomyosin system in the process of capturing and constricting prey organisms. Although our results provide clear evidence for the overall importance of motive force generation according to the hydraulic pressure theory, some motile phenomena exist in Amoeba proteus that cannot exclusively be explained by this mechanism.     

Microbodies (Glyoxysomes and Peroxisomes) in Cucumber Cotyledons: Correlative Biochemical and Ultrastructural Study in Light- and Dark-grown Seedlings

The changes in activities of glyoxysomal and peroxisomal enzymes have been correlated with the fine structure of microbodies in cotyledons of the cucumber (Cucumis sativus L.) during the transition from fat degradation to photosynthesis in light-grown plants, and in plants grown in the dark and then exposed to light. During early periods of development in the light (days 2 through 4), the microbodies (glyoxysomes) are interspersed among lipid bodies and contain relatively high activities of glyoxylate cycle enzymes involved in lipid degradation. Thereafter, these activities decrease rapidly as the cotyledons expand and become photosynthetic, and the activity of glycolate oxidase rises to a peak (day 7); concomitantly the microbodies (peroxisomes) become preferentially associated with chloroplasts.     

Über das gleichzeitige Vorkommen von zweierlei Eiweißkörpern in den Zellkernen vonPseudolysimachion spicatum und einigen anderen Scrophulariaceen

Zusammenfassung Die Zellkerne vonPseudolysimachion spicatum, Veronica cymbalaria undV. gentianoides enthalten zweierlei Eiweißkörper von je nach dem Entwicklungszustand unterschiedlicher Konsistenz. Bis zum Höhepunkt ihrer Entwicklung liegen sie als anscheinend amorphe flüssige oder gelartige Gebilde vor. Später tritt — mit gewebespezifischen Unterschieden — Verfestigung und Kristallisation ein, und zwar bei beiden nicht gleichzeitig und z. T. auch nur beim großen. Beiderlei Körper unterscheiden sich deutlich in physikalischer und chemischer Hinsicht, außerdem in ihrer Entwicklungsgeschichte und Strukturveränderung. Sie fehlen in den Schließzellen, im Antherentapetum, in den Pollenmutterzellen, Pollenkörnern, im Embryosack, im Endosperm und im Embryo.Die Zellkerne in der Blattepidermis vonPenstemon barbatus enthalten ebenfalls zweierlei Eiweißkörper. Davon liegt einer als kugeliges Gebilde, der andere als Kristallstapel vor.

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Summary In the nuclei ofPseudolysimachion spicatum, Veronica cymbalaria, V. gentianoides there occur two different kinds of protein bodies. They clearly differ from one another in physical and chemical regard as well as in their ontogeny. At first they are amorphous, liquid or geluous. As a rule a consolidation or crystallization with differences according to the tissue takes place after the climax of the development, and that not at the same time within both bodies. In the stomata cells, pollen mother cells, in the embryo sac, in the endosperm, in the endothelium and in the embryo both bodies do not occur.The nuclei in the epidermis of the leaves ofPenstemon barbatus also contain two different kinds of protein bodies, one of them appearing as a round body, and the other one as a pile of crystal plates.

     

Über Struktur und Innervation der quergestreiften Muskulatur des Oesophagus der Ratte

Zusammenfassung Die Muskelwand des Rattenoesophagus besteht ausschließlich aus quergestreiften Muskelfasern. Diese weisen keine Strukturunterschiede gegenüber gewöhnlichen Skeletmuskeln der Ratte auf. Sie sind in zwei spiralig gegenläufigen Muskelschichten angeordnet. Zwischen den beiden Muskelschichten befindet sich ein mit ChE-Darstellungsmethoden anfärbbarer Plexus myentericus, der an seinen Kreuzungspunkten regelmäßig Ganglienzellen aufweist. 10% der Ganglienzellen sind stark ChE-positiv, es handelt sich um tiberwiegend spezifische AChE.Die Rr. oesophagei des N. vagus zeigen sowohl marklose als auch myelinisierte Axone. Die Endäste, die den Plexus verlassen, um an motorischen Endplatten zu endigen, sind marklos.Die motorischen Endplatten weisen muldenförmige Einsenkungen des Sarkolemms auf. Die subsynaptische Membran ist reichlich in Palten gelegt, auch dort, wo ihr kein terminales Axon aufliegt. Es wurden 2 Arten von terminalen Axonen an den Endplatten festgestellt: 1.Dicke Axone, die mit vielen synaptischen Bläschen angefüllt sind, daneben aber auch einige granulierte Bläschen enthalten. 2. Dünne, fast ausschließlich mit granulierten Bläschen erfüllte Axone. Oft berühren die terminalen Axone einander unmittelbar, bisweilen unter Bildung von Membranverdickungen.

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Structure and innervation of the striated muscle fibres of the esophagus of the rat

Summary The muscular wall of the esophagus of the rat consists exclusively of striated muscle fibers which do not differ from the skeletal muscles of the same animal. These fibres are arranged in two layers running spirally in contrary directions. Between these two layers a ChE-positive myenteric plexus occurs, containing several ganglionic cells at its crossing points. 10 per cent of these ganglionic cells are strongly AChE-positive. The tiny branches of the vagus nerve, passing through the outer muscular layer into the myenteric plexus consist of bundles of unmyelinated as well as myelinated fibres. The terminal branches of the plexus leading to motor endplates are unmyelinated.The motor endplates are situated in trough-shaped impressions of the surface of muscle fibres. The subsynaptic sarcolemma is richly folded, even in places where there is no overlying synaptic terminal.There are two kinds of nerve terminals in the motor endplates: (1) Thick terminals abundantly filled with clear synaptic vesicles but also containing a few dense core vesicles. (2) Thin axons containing predominantly granulated vesicles.The synaptic nerve terminals often come into contact with each other, occasionally forming membrane thickenings at such places.

     

La place des principes d'expérimentation en pisciculture

Summary The author tries to determine the best area and the best experimental design in fish farming. He suggests 0,05 acre ponds to study fish production and 0,12 acre ponds to experiment reproduction and raising of young fish.If some groups controlling especially the effects of ponds areas, the after effects of treatments and the quality of waters, improve the precision of experiments, the best technic finally consists in the use of covariance analysis.In fish production, the determination of the flow and in fish breeding the mensuration of the total length of the females are equivalent to 15 and 32 repetitions of the experiment respectively.

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Résumé L'auteur recherche la superficie et le plan d'expérimentation optimum en pisciculture. Il préconise des étangs de 2 ares pour les études de production et de 5 ares pour les essais de reproduction et alevinage. Si certains groupements contrôlant notamment les superficies des étangs, les arriéres effets de traitements antérieurs, les qualités d'eaux d'alimentation, améliorent la précision de l'essai, l'action la plus efficace revient à l'analyse de la covariance.En pisciculture de production, la détermination des débits et en pisciculture de reproduction alevinage, la mensuration de longueur totale des femelles équivalent respectivement à 15 et 32 répétitions de l'essai.