The physiological basis of seed dormancy in Avena fatua. II. On the involvement of alternative respiration in the stimulation of germination by sodium azide

Chromatography on DEAE-cellulose of an extract from etiolated leaves of sorghum ( Sorghum vulgare Pers. cv. INRA 450), a C₄ plant, gave only one form of phosphoenol pyruvate carboxylase with functional and regulatory properties of a C₃ type plant enzyme. Greening of the leaves resulted in a significant increase in activity. This increase was due to the appearance of a new form of the enzyme, which eluted at lower ionic strength and exhibited new properties. This form was glucose-6-P activated and showed a sigmoidal curve response to the concentration of the substrate phosphoerralpyruvate. These kinetic properties are typical of a C₄ plant enzyme.     

DEMONSTRATION OF ACID PHOSPHATASE-CONTAINING GRANULES AND CYTOPLASMIC BODIES IN THE EPITHELIUM OF FOETAL RAT DUODENUM DURING CERTAIN STAGES OF DIFFERENTIATION

Dense cytoplasmic bodies surrounded by one or two unit membranes and containing mitochondria, vesicles, ribosomes, rough and smooth surfaced endoplasmic reticulum, and lamellated membranes (myelin figures) have been observed in the differentiating mucosa of the duodenum of rat foetuses by electron microscopy. Generally, the cytoplasmic components in the bodies seem to be in varying stages of disintegration. The bodies are found in greatest number on the 17th and 18th day of gestation, i.e. at the onset of differentiation. At this period of development the epithelium is stratified, and the villus formation is initiated by invagination of the epithelium by buds of mesenchyme followed by a splitting of the epithelium along the sides of the invaginations. When the villi have formed, the stratified epithelium has changed to the simple columnar type and the dense bodies have largely disappeared. Simultaneously, the lumen has widened considerably. In a parallel study with the light microscope, frozen sections incubated for the demonstration of acid phosphatase activity revealed the reaction product to be localized in bodies of the same size and distribution as the dense bodies found by electron microscopy. Hence, it seems that the bodies are altered and enlarged lysosomes (cytolysomes) active during the intensive differentiative events in the small intestine during the last part of intra-uterine life.     

Über den Feinbau „Gitterartig” Aufgebauter Plasmaeinschlüsse in den Siebelementen von Dioscorea Reticulata

Zusammenfassung Ein hochgeordnetes System tubulärer Strukturen wurde als bisher unbekannter Plasmaeinschluß in den Siebelementen von Dioscorea reticulata beschrieben. 250 Å weite, kontrastreiche Tubuli ordnen sich in hexagonal dichtester Packung zu 0,2 bis 1,3 großen Körpern an. Die einzelnen Tubuli sind helixähnlich gewunden und geben dem Plasmaeinschluß eine den Heitz-Leyon-Kristallen der Plastiden von Chlorophytum ähnliche Gestalt. Herkunft und Bedeutung dieser Gebilde sind noch weitgehend unbekannt.

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On the fine structure of a lattice-like body in the sieve elements of Dioscorea reticulata

Summary In the parietal protoplast of differentiated sieve elements of Dioscorea reticulata an up to now unknown lattice-like body has been described in detail. Many 250 Å wide tubules combine to form very regularly composed bodies, which are about 0.2 to 1.3 large. Each tubule is twined like a helix and is spaced equidistantly from the adjoining ones, the interval being 450 to 500 Å. On the whole the lattice-like bodies of Dioscorea largely resemble the so-called Heitz-Leyon-crystals of young plastids.

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Acanthocheilonema viteae (Dipetalonema viteae) in mice: attempts to correct the low responder phenotype of the BALB/c host

Attempts were made to correct the low responder phenotype of microfilaraemic Acanthocheilonema viteae (Dipetalonema viteae) infected BALB/c mice through the transfer of immune spleen cells and immune serum from amicrofilaraemic B10 background mice. The transfer of immune cells and serum prior to infection failed to influence development of microfilaraemia in BALB/c recipients. Attempts to alter the course of an established microfilaraemia in BALB/c mice through the transfer of 3 x 10(7) immune spleen cells were unsuccessful but transfer of 3 x 10(8) cells reduced microfilaraemia temporarily. Treating microfilaraemic BALB/c mice with immune serum brought about a rapid reduction in microfilaraemia. This effect was only temporary and numbers of circulating microfilariae returned to control levels within a short time. Repeated serum transfers reduced the microfilaraemia only during the period of treatment. Similar results were obtained when immune serum was given to microfilaraemic, immunodeficient CBA/N mice.     

The effect of chemical stress on the polypeptide composition of the intercellular fluid of barley leaves

The effect of chemical stress on the polypeptide composition of the intercellular fluid of barley (Hordeum vulgare L.) and tomato (Lycopersicon esculentum Mill.) leaves has been studied. In some dicotyledonous plant species, including tomato, exposure to chemical stress leads to the denovo synthesis of intercellular proteins known as pathogenesis-related proteins which have been implicated to be part of a defence mechanism. In barley, however, no such changes in the polypeptide composition of the intercellular fluid could be detected. On the other hand, similar stress conditions induce in barley a strong accumulation of mRNA encoding leaf-specific thionins. These barley thionins represent a novel class of cell-wall proteins toxic to phytopathogenic fungi and are possibly involved in the defence mechanism. These proteins could not be detected in tomato plants. In contrast to the pathogenesis-related proteins of dicotyledonous plants, the leaf-specific thionins of barley are not present in the intercellular fluid of leaves. These results indicate that barley may have evolved a different mechanism to cope with the presence of stress.Abbreviations PAGE polyacrylamide gel electrophoresis - PR pathogenesis-related - SDS sodium dodecyl sulfate