Structural and Functional Impact of SRP54 Mutations Causing Severe Congenital Neutropenia

1. Download : Download high-res image (235KB)
2. Download : Download full-size image

     

The Phylogenetic Position of the Rhizocephala: Are They Truly Barnacles?

Incorporation of the Rhizocephala in the Cirripedia, reflecting the traditional view that these parasites evolved from a setose feeding barnacle, has recently been challenged in favour of rhizocephalans being the sister group to all other Thecostraca or a scenario where they evolved from a free-living, ‘precirripede’ ancestor. Adult morphology is useless in discussing the monophyly of the Cirripedia, since rhizocephalan adults are too reduced to furnish any phylogenetic evidence. But numerous, detailed similarities in nauplii and cyprids of the Thoracica, Acrothoracica and Rhizocephala as well as the ultrastructure of their sperm are synapomorphic relative to other Thecostraca and indicate that these three orders form a monophylum. There is evidence that the stylet in the rhizocephalan kentrogon is homologous to an element in the ancestral mouth field. If so, the Rhizocephala probably evolved before setose feeding was adopted, and constitute the sister group to the Acrothoracica and Thoracica. This conclusion is based on frail evidence so the term Cirripedia should be retained to comprise the Rhizocephala, Thoracica, and Acrothoracica. These three orders all possess remarkably similar cyprids, adapted to accomplish irreversible settlement by cement secretion and initiate metamorphosis, so their last common ancestor was most probably a permanently sessile organism.     

Regulation of the photosynthetic electron transport during dark-light transitions by activation of the ferredoxin-NADP+-oxidoreductase in higher plants

Absorbance changes associated with the oxidation and reduction of cytochrome f belong to the classical observations about the interaction of the two photosystems. A complex induction pattern of cytochrome f oxidation results, if both photosystems are excited simultaneously. This indicates a light-modulated regulation of the photosynthetic electron transport, which we examined for intact biological systems of decreasing complexity. The ferredoxin-NADP⁺-oxidoreductase (FNR) is suggested to be activated by light and inactivated in the dark. This is pointed out by the kinetics of variable fluorescence and by the influence of different artificial electron acceptors on the cytochrome f kinetics. The photoreduction of NADP⁺ by carefully prepared thylakoids demonstrates the activation process directly.This work was supported by the Deutsche Forschungsgemeinschaft.     

12-O-tetradecanoyl phorbol 13-acetate stimulates the myristylation of an approximately 82 kDa protein in HL-60 cells

We have studied protein acylation using [3H]myristate in the two leukemia cell lines HL-60 and HL-60 Blast II. The latter is a variant which does not differentiate after treatment with 12-O-tetradecanoyl phorbol 13-acetate (TPA). The acylation profiles of the two cell lines as examined by SDS-PAGE differed. TPA induced the myristylation of an approximately 82 kDa protein in the sensitive cells, but not in the resistant cells. Myristic acid was shown to be covalently linked to these proteins. Analysis of the cell lipids labelled with [3H]myristate showed that in contrast to observations with the proteins, the changes induced by TPA were observed in both TPA-sensitive and TPA-resistant cells. We conclude that the induction of myristylation may be an important step in the mechanism of differentiation.     

Parathyroid cell variants may be provoked during immersion fixation

Summary Parathyroid glands of cattle, dogs, cats, mice and rats were immersed in glutaraldehyde or mixtures consisting of glutaraldehyde, formaldehyde and acrolein in either Na-phosphate, Na/K-phosphate or Na-cacodylate buffer, and postfixed with OsO₄ in the same buffers or, alternatively, in s-collidine.Excellent preservation of bovine, feline and murine parathyroid glands was achieved with fixation mixtures containing 1% glutaraldehyde, 1.5–2% formaldehyde and 2.5–5% acrolein in 0.1 M Na-cacodylate with or without Ca²⁺ and Mg²⁺, Na-phosphate or Na/K-phosphate at 4°C followed by postfixation with 1% OsO₄ in the same buffers or in s-collidine containing sucrose, Ca²⁺ and Mg²⁺. This procedure largely abolished the occurence of parathyroid cell variants. Bovine parathyroid glands were also satisfactorily preserved with 1% glutaraldehyde and 2% formaldehyde whereas 1% glutaraldehyde and 2.5 or 5% acrolein, lower or higher buffer osmolarity, or immersion at room temperature led to vacuolization of RER and to breakdown of membranes. In contrast, all fixation protocols led to the formation of dark and light cell variants and to multinucleated syncytial cells in dog and rat parathyroids. The results thus show that parathyroid cell variants arise during immersion fixation and that aldehydes, buffers and temperature are important factors for provoking parathyroid cell variants.     

A morphometric and ultrastructural study of lithium-induced changes in the medullary collecting ducts of the rat kidney

Summary Rats were given a lithium-containing diet (40 mmol/kg) to Study the effect of lithium on the structure of collecting ducts from the inner stripe of the outer medulla. The results show that there is a significant increase in the volume density of collecting ducts already after one week on this diet. The volume density of both intercalated and principal cells increases, whereas the volume density of mitochondria in the cytoplasm increases in the intercalated cells only. The increased volume of both principal and intercalated cells seems to be part of a general hyperplasia and hyperactivity of the collecting duct, which may in some way be related to the effects of lithium on vasopressinmediated water transport. The specific changes in the intercalated cells may be a consequence of the effects of lithium on distal nephron potassium and hydrogen ion transport in the distal nephron.     

Further antigenic analyses of the fish pathogenic bacteriumVibrio anguillarum

TenVibrio anguillarum strains were selected for an immunoelectrophoretic study. Evidence was provided for existence of two new K antigens which displayed cross-reactivity. The importance of an exact characterization of surface antigens inV. anguillarum is considered.     

Potency of microwave irradiation during fixation for electron microscopy

Liver, skeletal muscle, peripheral nerves, pancreas, thyroid and adrenal cortex were prepared for electron microscopy employing microwave energy either during prefixation with glutaraldehyde or instead of prefixation. Microwave irradiation in the presence of glutaraldehyde in Na/K-phosphate or Na-cacodylate containing CaCl2 and MgCl2 led to distinct appearance of membranes, mainly plasma membrane, and membranes of SER, Golgi complex and mitochondria in liver, pancreas and muscle. The area of high quality fixation, however, was limited to the periphery of samples. On the other hand, SER was dilated in cells of the adrenal cortex, and RER markedly vacuolated in thyroid follicular cells. Microwave irradiation in the presence of Na/K-phosphate and subsequent osmication resulted in preservation of the ultrastructure in similar quality as was obtained by osmication without previous immersion in glutaraldehyde. However, the preservation of SER and Golgi complex in liver and pancreas, and of mitochondria in muscle was greatly improved. Small myelin sheaths remained intact whereas large ones showed focal disintegration. We consider that enhancement of fixation by microwave energy may greatly improve preservation of membranes in some tissues. Successful fixation depends on the use of glutaraldehyde during microwave irradiation, the type of buffer, the addition of ions to increase stabilization, the exposure time to heat, and on postosmication.     

Host plant recognition in monophagous weevils: specificity in feeding responses of Ceutorhynchus constrictus and the variable effect of sinigrin

Host plant relations of the monophagous weevil Ceutorhynchus constrictus Marsh. (Coleoptera: Curculionidae: Ceutorhynchinae) feeding on garlic mustard, Alliaria petiolata (Bieb.) Cavara & Grande (Cruciferae) were studied in the laboratory. Most other crucifers were rejected in choice tests using garlic mustard as a reference plant, but Brassica nigra, Sinapis alba and Thlaspi arvense were as acceptable as the host plant. Flowering plants of Descurainia sophia were acceptable while young plants of this species were not. The most important feeding stimulants in extracts of garlic mustard were uncharged, water soluble compounds. The most abundant glucosinolate in garlic mustard, sinigrin, was a feeding stimulant, too. However, the feeding stimulatory activity of sinigrin was only expressed in the presence of still unidentified uncharged compounds from garlic mustard leaves. Host plant relations in monophagous crucifer-feeding insects is discussed in relation to the distinctness of glucosinolate patterns found in their host plants.

---

Zusammenfassung Ceutorhynchus constrictus Marsh. (Coleoptera: Chrysomelidae: Ceutorhynchinae) ist ein monophager Rüsselkäfer, der an Knoblauchhederich frisst. Das Wirtswahl-Verhalten dieses Käfers ist im Labor untersucht worden. Die meisten Crucifiren waren im Wahlversuche nicht akzeptiert, wenn Knoblauchhederich als Vergleichspflanze vorhanden war. Von Brassica nigra, Sinapis alba, und Thlaspi arvense wurden im Vergleich gleiche Mengen verzehrt wie von der Wirtspflanze. Blühende Descurainia sophia Pflanzen wurden, im Gegensatz zu Jungpflanzen der gleichen Art, angenommen. Die wichtichsten Phagostimulanten in Extrakten von Knoblauchhederich-Blättern waren ungeladene, wasserlösliche Substanzen. Das häufigste Glukosinolat im Knoblauchhederich, Sinigrin, war auch ein Phagostimulant. Doch war die phagostimulierende Wirkung von Sinigrin nur in Kombinationen mit noch nicht identifizierten, ungeladenen Substanzen aus Knoblauchhederich-Blätter nachweisbar. Wirtspfanzen-Beziehungen von monophagen Insekten werden diskutiert im Zusammenhang mit der Eigenart des Glukosinolat-Inhaltes ihrer Wirtspflanzen.