Matrilins mediate weak cell attachment without promoting focal adhesion formation.

The matrilins form a family of non-collagenous adaptor proteins in the extracellular matrix. The extracellular ligand interactions of matrilins have been studied in some detail, while the potential interplay between matrilins and cells has been largely neglected. Except for matrilin-4, all matrilins mediate cell attachment, but only for matrilin-1 and -3 the binding is clearly dose dependent and seen already at moderate coating concentrations. Even so, much higher concentrations of matrilin-1 or -3 than of fibronectin are required for cell attachment to reach plateau values. Integrins contribute to the matrilin-mediated cell attachment, but the binding does not lead to formation of focal contacts and reorganisation of the actin cytoskeleton. Cells deficient in beta1 integrins are able to adhere, although weaker, and matrilins do not bind the soluble integrin alpha1beta1 and alpha2beta1 ectodomains. Cell surface proteoglycans may promote the attachment, as cells deficient in glycosaminoglycan biosynthesis adhere less well to matrilin-3. Even so, exogenous glycosaminoglycans are not able to compete for the attachment of HaCaT cells to matrilins.     

Protective Role of the Virus-Specific Immune Response for Development of Severe Neurologic Signs in Simian Immunodeficiency Virus-Infected Macaques

The pathogenesis of human immunodeficiency virus-associated motor and cognitive disorders is poorly understood. In this context both a protective and a harmful role of the immune system has been discussed. This question was addressed in the present study by correlating the occurrence of neurologic disease in simian immunodeficiency virus (SIV)-infected macaques with disease progression and the humoral and cellular intrathecal antiviral immune response. Overt neurologic signs consisting of ataxia and apathy were observed at a much higher frequency in rapid progressor animals (6 of 12) than in slow progressors (1 of 7). Whereas slow progressors mounted a strong antiviral antibody (Ab) response as evidenced by enzyme-linked immunosorbent and immunospot assays, neither virus-specific Ab titers nor Ab-secreting cells could be found in the cerebrospinal fluid (CSF) or brain parenchyma of rapid progressors. Similarly, increased infiltration of CD8⁺ T cells and cytotoxic T lymphocytes specific for viral antigens were detected only in the CSF of slow progressors. The finding that neurologic signs develop frequently in SIV-infected macaques in the absence of an antiviral immune response demonstrates that the immune system does not contribute to the development of motor disorders in these animals. Moreover, the lower incidence of neurologic symptoms in slow progressors with a strong intrathecal immune response suggests a protective role of the virus-specific immunity in immunodeficiency virus-induced central nervous system disease.     

Osmotically reactive plasma membrane vesicles prepared from rabbit kidney tubules by mild hypotonic lysis

Plasma membrane vesicles were obtained by hypotonic lysis in an ice-cold medium containing EDTA and MgCl₂. The vesicles were isolated by differential centrifugation. Compared to a total kidney homogenate, a 10–12-fold enrichment of trehalase and alkaline phosphatase (marker enzymes for renal brush border), and a 6-fold enrichment of (Na⁺---:K⁺)-stimulated ATPase, (a marker enzyme for the basal and lateral plasma membrane of the tubule cell), was achieved. Contamination by other cell organelles was very low. The plasma membrane vesicles enclosed small amounts of the cytoplasmic enzymes lactate dehydrogenase and malate dehydrogenase, which exhibited full activity only after their release into the medium by sonication.Electron micrographs of this preparation showed microvilli with drumstick-like expansions, but also spherical vesicles. By measuring the distribution of radio-actively labelled compounds of different molecular weight in a packed sediment of the plasma membranes under isotonic conditions, an intravesicular volume of 82% or 9 μl/mg of membrane protein was estimated. The intravesicular volume decreased when the osmolality of the medium was augmented by raffinose. The scattering of light by the vesicular suspension could be used to monitor rapid volume changes. By this method, the following sequence of flux rates was established: glycerol>erythritol> adonitol>mannitol. The fluxes of LiCl, NaCl, and KCl were almost identical, but faster than those of adonitol and mannitol. The data indicate, that a large fraction of the plasma membrane isolated in this preparation have formed vesicles, and also that they have retained, as far as investigated, the permeability characteristics of the plasma membrane.     

Beziehungen zwischen Struktur und chemischer Zusammensetzung der Spermien vom Bergmolch,Triturus alpestris Laur.

Zusammenfassung Aus isolierten Achsenfäden der Spermien von Triturus alpestris Laur. wurden drei Proteinfraktionen extrahiert und nach ihrer Zusammensetzung analysiert. In der leichtlöslichen Fraktion f3 überwog Arginin, daneben fand sich u.a. Cystin. f1+f2b enthielt weniger Arginin, dafür aber mehr Lysin. Den größten Anteil hatte hier Alanin. In jeder der beiden Fraktionen waren nur neun Aminosäuren vorhanden. Die schwerlösliche Fraktion c3 enthielt außer Cystin, Methionin und Tyrosin alle nachweisbaren Aminosäuren. Außerdem wies die Fraktion f1+f2b nicht weniger als fünf unbekannte Komponenten auf, von denen eine ein hellgrüner Farbstoff war. In geringeren Mengen kamen drei dieser Substanzen in f3 und noch eine in c3 vor. Nach den Ergebnissen des enzymatischen Abbaus an Ultradünnschnitten von glutaraldehydfixiertem Material dürfte die argininreiche Fraktion im Inneren des Achsenfadens, und zwar in seinem distalen Anteil zu lokalisieren sein. Die lysinreiche Fraktion wäre demnach im Inneren des proximalen Anteils zu finden, während die schwerlösliche Komponente c3 mit der außerordentlich widerstandsfähigen Rinde des Achsenfadens identisch wäre. Im Halsstück, das aus einem kristallinen Mantel und einem homogenen elektronendichten zentralen Teil besteht, fanden sich mindestens drei Komponenten. Der Mantel enthielt ein leicht extrahierbares Protein und ein stabiles Gerüst, in dem aromatische Aminosäuren vermehrt vorzukommen scheinen. Der zentrale Teil bestand aus argininreichen Verbindungen. Die Befunde werden im Zusammenhang mit der Bildung von Achsenfaden und Halsstück während der Spermiogenese diskutiert.

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Relationships between structure and chemical composition of spermatozoa of the newt, Triturus alpestris Laur.

Summary Axial rods from spermatozoa of Triturus alpestris Laur. have been isolated. Three protein fractions therefrom could be extracted and analysed for their composition. Arginine prevailed in the soluble fraction f3, among others also cystine was found. f1+f2b contained less arginine, but more lysine. The highest percentage was found here for alinine. In each of the two fractions only nine amino acids were present. The sparely soluble fraction c3 contained all identifiable amino acids besides cystine, methionine and tyrosine. Moreover, the fraction f1+f2b showed as many as five unknown components, from which one was a light-green colour. To a lesser degree three of these compounds were also found in fraction f3 and still one in fraction c3. According to the results of the enzymatic digestion carried out on ultrathin section of material fixed with glutaraldehyde, the arginine-rich fraction should be localized in the center of the axial rod in its distal part. The lysine-rich fraction would then be found in the center of the proximal part, while the sparely soluble fraction c3 would be identical with the extremely resistant cortex of the axial rod. Within the neck-piece, which consists of a crystalline mantle and a homogenously dark central part, at least three components were present. The mantle contained an easily extractable protein and a stable frame, in which aromatic amino acids seemed to be increased. In the central part arginine prevailed. The results are discussed with regard to the formation of the axial rod and the neck-piece during spermiogenesis.

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Mit dankenswerter Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Experimente am ungefurchten Ei vonPimpla turionellae L. (Hymenoptera) zur Funktionsanalyse des Oosombereichs

Summary In endoplasm close to the posterior pole of the egg ofPimpla one finds conglomerated oosome material, rich in RNA. Investigations after various operations in the oosome region (10% of egg length), before cleavage were intended to show whether pole cells develop, how many segments form and if gonads contain primordial germ cells.Oosome material was squashed with a blunt glass needle. The uninjured part of the egg in front of the oosome region develops blastoderm but no pole cells. It gives rise to a fully segmentated larva with germ cells in the gonads.After ligation of up to 15% of egg length complete embryos with germ cells can develop. The smaller the anterior isolates, the more abdominal segments are missing.By ligation and invagination of the hindpole of eggs with a blunt glass needle, anteriorly material from the oosome region is combined with ooplasm situated more. Translocation of only a small amount of ooplasm results in the same number of abdominal segments in the anterior isolate as in ordinary ligated eggs. Translocation of much ooplasm yields a significantly greater number of abdominal segments. It is immaterial for the metameric segmentation of the embryo whether the oosome is situated before or behind the ligature or is destroyed. But the depth of the invagination and how many segments result do not seem to be correlated.A completely segmentated embryo can develop also after extirpation of the oosome provided care is taken not to injure the hindpole-plasm. No pole-cells result when the complete oosome is missing and the hindpole-plasm is present; loss of part of the oosome results in the development of only a few pole-cells. Thus oosome material is a necessary and quantitative condition for pole-cell differentiation. In one favourable case pole-cells developed in the extraovate because the oosome was followed after some hours by endoplasm and cleavage nuclei.Functions of the oosome are discussed: together with cleavage nuclei it is responsible for pole-cell development. As pole-cells are not invariable precursors of germ-cells, the oosome cannot contain determinants for them. Possibly it includes postembryonic growth modifiers or it could be active in gametogenesis later on. As an egg without oosome-region is able to develop an embryo, this region does not or exclusively contain an activation-center (e. g.Platycnemis), or special hind-pole factors (e. g.Euscelis). In any case the oosome itself does not include these factors. A greater number of segments in the anterior isolate after translocation of ooplasm could be due to its special quality, as inEuscelis andBruchidius whose metameric organisations originate from a bipolar ooplasmic reaction system. Also it could depend only on the increase of ooplasm competent for differentiation-factors in the middle and anterior egg parts.

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Durchgeführt mit Leihgaben der Deutschen Forschungsgemeinschaft und mit Hilfe von Euratom (Verträge Nr. 041-65-10 BIOD und Nr. 077-69-I BIOC mit dem Heiligenberg-Institut).     

Régulation sociale dans les sociétés orphelines d'Evylæus nigripes (Lep.) (Hym.,Halictidæ)

Résumé Dans les sociétés orphelines d'Evylæus nigripes, l'une des ouvrières joue le rôle de reine: elle ne participe pas à la récolte du pollen, demeurant constamment au nid, et assume la plus grande part de la ponte sociale.On établit un parallèle entre les sociétés orphelines et les fondations polygynes de la même espèce: les unes et les autres semblent révéler l'existence d'un effet de groupe.

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Summary In queenless societies ofEvylæus nigripes, one of the workers assumes the rôle of a lost queen: she remains permanently in the nest, lays most of the eggs but does not collect any pollen.Queenless societies of workers resemble polygynous spring associations of this species: both indicate the existence of a group effect.