Liquid-to-solid phase transition of oskar ribonucleoprotein granules is essential for their function in Drosophila embryonic development

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Ultrastructural and cytochemical studies of acid phosphatase and trimetaphosphatase in rat peritoneal mast cells developing in vivo

Summary The ultrastructural and cytochemical features of peritoneal mast cells of the rat were studied. Immature mast cells show specific cytoplasmic granules of different sizes, the smaller ones localized in the Golgi region. The rough endoplasmic reticulum and Golgi apparatus are well developed, and mitochondria are numerous. Nuclei show deep indentations. Acid phosphatase is present in the Golgi saccules, in GERL (Golgi apparatus-endoplasmic reticulumlysosome) and in some small granules. It is not present in mature granules. Trimetaphosphatase is present in the Golgi saccules, in GERL, in most immature granules and in some mature granules. These enzymes appear to be transported and packaged into granules by the Golgi apparatus, suggesting that the specific mast cell granules may be a form of lysosome. The results of this study are consistent with the hypothesis that peritoneal mast cells may be derived from macrophage-like precursors.     

Ultrastructure of endocrine pancreatic granules during pancreatic differentiation in the grass snake,Natrix natrix L. (Lepidosauria,Serpentes)

We used transmission electron microscopy to study the pancreatic main endocrine cell types in the embryos of the grass snake Natrix natrix L. with focus on the morphology of their secretory granules. The embryonic endocrine part of the pancreas in the grass snake contains four main types of cells (A, B, D, and PP), which is similar to other vertebrates. The B granules contained a moderately electron‐dense crystalline‐like core that was polygonal in shape and an electron‐dense outer zone. The A granules had a spherical electron‐dense eccentrically located core and a moderately electron‐dense outer zone. The D granules were filled with a moderately electron‐dense non‐homogeneous content. The PP granules had a spherical electron‐dense core with an electron translucent outer zone. Within the main types of granules (A, B, D, PP), different morphological subtypes were recognized that indicated their maturity, which may be related to the different content of these granules during the process of maturation. The sequence of pancreatic endocrine cell differentiation in grass snake embryos differs from that in many vertebrates. In the grass snake embryos, the B and D cells differentiated earlier than A and PP cells. The different sequence of endocrine cell differentiation in snakes and other vertebrates has been related to phylogenetic position and nutrition during early developmental stages.     

SAMHD1 controls innate immunity by regulating condensation of immunogenic self RNA

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Extraction and detection methods for polyphosphate storage in autotrophic planktonic organisms

Different extraction procedures were employed to characterise the polyphosphate granules in autotrophic planktonic organisms, the green microalgae Chlorella vulgaris and the cyanobacterium Synechocystis sp. strain PPC 6803. The effectiveness of these methods was assessed using epifluorescence microscopic analysis of DAPI stained specimens as well as by electron spectroscopic imaging. The results clearly indicate that NaOH and hot water treatment followed by filtration of the extracts are suitable to obtain a cell free suspension of intact polyphosphate granules without hydrolysing the polymers. The methods described are useful to gain physiological information on the phosphorus status of autotrophic planktonic organisms.     

Nervenfasern mit ultrastrukturell verschiedenen Elementargranula im Hypophysenhinterlappen des Rhesusaffen

Zusammenfassung Im Hypophysenhinterlappen des Affen lassen sich elektronenmikroskopisch zwei Arten markarmer, neurosekrethaltiger Nervenfasern beobachten. Sie unterscheiden sich voneinander durch den Typ der Elementargranula, die sie enthalten.In Nervenfasern des Typs I haben die Elementargranula einen Durchmesser von 1500 bis 3500 Å. Sie besitzen eine geringe Elektronendichte und enthalten oft kreisförmig angeordnete Proteinkörnchen. Vereinzelt sind kristallähnliche Formationen des Granulainhalts zu erkennen.Die Elementargranula in Nervenfasern des Typs II messen 1200–2200 Å im Durchmesser. Ihr Inhalt besitzt infolge eng aneinander gelagerter granulärer Teilchen eine weitaus größere Elektronendichte als die Granula des Typs I. Kristallähnliche Granulaeinschlüsse waren nicht zu sehen.Die ultrastrukturelle Differenzierung zweier Nervenfasergruppen im Hypophysenhinterlappen wirft die Frage auf, ob es sich bei dem einen Typ um vasopressin-bei dem anderen Typ um oxytocinhaltige hypothalamische Nervenfasern handelt.Die Pituizyten im Hypophysenhinterlappen des Rhesusaffen besitzen Granula (1500 bis 3000 Å) mit einer Innenstruktur ähnlich den Neurosekretgranula vom Typ II. Sie enthalten außerdem größere, fein granulierte osmiophile Grana.

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Neurosecretory nerve fibres containing ultrastructurally different elementary granules in the hypophysial posterior lobe of the rhesus monkey

Summary In the posterior lobe of the neurohypophysis of the rhesus monkey, two kinds of unmyelinated nerve fibres containing neurosecretory substance can be discerned with the electron microscope. They differ with respect to the type of elementary granules they contain.In type I nerve fibres the elementary granules have a diameter of 1,500–3,500 Å. They are of little electron-density and often contain circularly arranged protein grains. Crystal-like formations of the content of the granules are sometimes observed.In type II nerve fibres the elementary granules measure 1,200–2,200 Å in diameter. Due to close packing of their granular content they are much more electron-dense than type I granules. Crystal-like inclusions were not seen.The ultrastructural differentiation of two groups of nerve fibres in the posterior lobe raises the question of whether the one type consists of vasopressin-containing and the other of oxytocin-containing hypothalamic nerve fibres.The pituicytes in the hypophysial posterior lobe of the rhesus monkey contain granules (1,500–3,000 Å) with an inner structure similar to type II neurosecretory granules. In addition, they contain larger, finely granulated osmiophilic grains.

Mit dankenswerter Unterstützung durch den Herrn Bundesminister für Bildung und Wissenschaft.     

Intracellular degradation of poly(3-hydroxybutyrate) granules of Zoogloea ramigera I-16-M

Abstract Intracellular degradation of poly(3-hydroxybutyrate) (PHB) in bacteria is not yet clear. The properties of the autodigestion of native PHB granules from Zooglea ramigera I-16-M were examined. The release of d (−)-3-hydroxybutyrate was observed only at pH values higher than about 8.5 and at relatively high ionic strength (optimal concentration 200 mM NaCl). Triton X-100 and diisopropylfluorophosphate inhibited this reaction. Addition of the supernatant fraction of Z. ramigera did not increase the release of d (−)-3-hydroxybutyrate from the native PHB granules. On the other hand, using the protease-treated PHB granules from Alcaligenes eutrophus as a substrate, PHB depolymerase activity was detected in the supernatant fraction of Z. ramigera cells. The soluble PHB depolymerase showed similar properties to the enzyme in the PHB granules. Since PHB depolymerase activity was found in fractions containing d (−)-3-hydroxybutyrate oligomer hydrolase activity, which were separated by DEAE-Toyopearl or by Sephacryl S-100, it is possible that the intracellular PHB depolymerase is identical to the oligomer hydrolase which has been purified already.     

Changes in the Ultrastructure of Prasiola crispa ssp. antarctica under Salinity Stress

The supralittoral green alga Prasiola crispa, collected in Antarctica, was grown at salinities ranging from 0.35 %o to 175 %o. Its ultrastructure was examined by electron microscopy and compared with the ultrastructure of plants grown under standard conditions (35 %o). The thalli had very thick cell walls, making up approximately 50% of the thallus volume. Most of the protoplast was occupied by a single chloroplast. Numerous starch granules in the chloroplast were enlarged under hypo-osmotic conditions and reduced in volume when subjected to hyperosmotic stress indicating a metabolic shift towards low molecular weight organic osmolytes under the latter conditions. Whilst vacuoles were lacking in plants cultured at salinities between 0.35 %o and 35 %o, they developed under hyperosmotic conditions and possibly may serve as compartments accumulating inorganic ions. Growth, photosynthesis and dark respiration were strongly inhibited under higher salinities, whilst they remained almost unaffected under lower salinities (Jacob et al., 1991).     

Control of secretory granule interaction and exocytosis in pancreatic cells

Application of the laser-based technique of photon correlation spectroscopy to anin vitro study of the ionic stability and interaction kinetics of zymogen granules isolated from rat exocrine pancreas is described here. In addition the separation from pancreatic acinar cell cytosol of a factor which stabilizes isolated zymogen granules and inhibits cation-induced granule aggregation is outlined. The basis of this action and the significance of the cytosolic inhibitory factor in the regulation of granule mobility and exocytosisin vivo is discussed.