Effect of cell cycle on the regulation of the cell surface and secreted forms of type I and type II human tumor necrosis factor receptors

The cell cycle has been shown to regulate the biological effects of human tumor necrosis factor (TNF), but to what extent that regulation is due to the modulation of TNF receptors is not clear. In the present report we investigated the effect of the cell cycle on the expression of surface and soluble TNF receptors in human histiocytic lymphoma U-937. Exposure to hydroxyurea, thymidine, etoposide, bisbensimide, and democolcine lead to accumulation of cells primarily in G₁/S, S, S/G₂/M, G₂/M, and M stages of the cell cycle, respectively. Whilie no significant change in TNF receptors occurred in cells arrested in G₁/S or S/G₂ stages, about a 50% decrease was observed in cells at M phase of the cycle. Scatchard analysis showed a reduction in receptor number rather than affinity. In contrast, cells arrested at S phase (thymidine) showed an 80% increase in receptor number. The decrease in the TNF receptors was not due to changes in cell size or protein synthesis. The increase in receptors, however, correlated with an increase in total protein synthesis (to 3.8-fold of the control levels). A proportional change was observed in the p60 and p80 forms of the TNF receptors. A decrease in the surface receptors in cells arrested in M phase correlated with an increase in the amount of soluble receptors. The cellular response to TNF increased to 8- and 2-fold in cells arrested in G₁ and S phase, respectively; but cells at G2/M phase showed about 6-fold decrease in response. In conclusion, our results demonstrate that the cell cycle plays an important role in regulation of cell-surface and soluble TNF receptors and also in the modulation of cellular response. © 1995 Wiley-Liss, Inc.     

Immunocytochemical colocalization of adhesive proteins with clathrin in human blood platelets: further evidence for coated vesicle-mediated transport of von Willebrand factor,fibrinogen and fibronectin

Coated membranes and vesicles play an important role in receptor-mediated endocytosis and intracellular trafficking in various cell types, and are also present in blood platelets. Platelets take up certain proteins from the blood plasma, such as von Willebrand factor and fibrinogen, and these substances are transferred to storage granules. The receptors for these plasma proteins on the platelet plasma membrane have been well characterized, but morphological evidence for their transport to the storage granules is not yet available. In an attempt to clarify this aspect, we employed postembedding immunocytochemistry on platelets embedded in the acrylic resin LR White. Clathrin as the major coat component of coated vesicles was localized in the cytoplasm, on the plasmic faces of -granules and the open canalicular system, and on the plasmic face of the plasma membrane. Colocalizations of the adhesive proteins, von Willebrand factor, fibrinogen and fibronectin, with clathrin could be observed at the same typical locations as coated vesicles were seen in Araldite-embedded material. These colocalizations have not been reported to date and furnish further evidence for a coated vesicle-mediated transport of blood plasma-derived adhesive proteins from their receptors on the outer plasma membrane to the -granules.     

Linkage analysis and allelic imbalance in human breast cancer kindreds using microsatellite markers from the short arm of chromosome 3

Eight Icelandic breast cancer kindreds were subjected to linkage analyses with respect to 28 microsatellite loci dispersed along the short arm of chromosome 3. Breast tumors derived from these kindreds were concurrently scored for allelic imbalance with ten of the markers. Linkage to most markers could be excluded on the basis of negative LOD scores and haplotype analyses, although some moderately positive LOD scores resulted. A high frequency of imbalance in the familial tumors was seen with two of the markers in comparison with results obtained from sporadic material. The highest frequency (68%) of imbalance was detected with the marker D3S1217, which is located on 3p14.2-p14.1. Imbalance at the D3S1211 locus, which is more telomeric (3p24.2-p22), was not significantly elevated in the familial tumors. We suggest that the genetic defect responsible for breast cancer susceptibility in these families either promotes instability in the 3p14.2-p14.1 region or enhances the selective advantage of such changes.     

Behavioral adaptations of two phytophagous insects feeding on two species of phototoxic Asteraceae

Two phototoxic plants of the Asteraceae family were studied in relation to species of phytophagous insects for which they are hosts:Argyrotaenia velutinana Wlk. feeding onChrysanthemum leucanthemum L. andChlorochlamys chloroleucaria (Guenée) colonizingRudbeckia hirta L. The toxicity of these two plants is related to the presence of acetylenes and thiophenes that induce a light-mediated production of deleterious singlet oxygen and other free radicals (phototoxicity). Results showed that females ofA. velutinana laid their eggs preferentially in the shade and the larvae adopted hiding behaviors, such as bending of ligulate corollas and silk spinning to build opaque shelters. By avoiding direct exposure to the sun, both behaviors may reduce phototoxicity associated with ingested plant materials. Furthermore, larvae ofC. chloroleucaria demonstrated a preference in the field for pollen, which constitutes a nonphototoxic tissue of their host plant. Experimental alterations of these specific behaviors induced important biological consequences for larvae of both insects such as mortality or reduction of larval growth rate. These results reinforce the idea that behavior may constitute an efficient adaptation to avoid phototoxicity.     

Einige neue oder bemerkenswerte Flechten mit gyalectoiden Apothecien von Nord-Indien und Nepal

This paper presents the results of taxonomic investigation of 8 species of lichens with gyalectoid apothecia collected in North-India and Nepal. Four species are recognized as new:Dimerella isidiata (sp. nova),D. nepalensis (sp. nova),Gyalideopsis lithophila (sp. nova) andRamonia nepalensis (sp. nova). Four species are reported for the first time from Nepal:Coenogonium moniliforme, Gyalectidium caucasicum, Gyalidea lecideopsis andG. scutellaris.     

Mineral cycling in a tropical palm forest

Nutrient cycling and biomass characteristics of a tropical palm forest dominated byOrbignya cohune were found to be different from thsoe of hardwood dominated forests. The cohune palm forest had a high proportion of biomass in leaves (5%), a reduced sapling layer, a large amount of standing forest litter and an exceptionally low decomposition rate factor (0.1 year^–1). Mineral concentrations in palm leaves were generally lower than in hardwood species with the exception of Na, which was exceptionally high inOrbignya cohune. Biomass was estimated at 226 tons ha^–1 containing 1173 kg ha^–1 N; 126 kg ha^–1 P; 437 kg ha^–1 K; 1869 kg ha^–1 Mg; 125 kg ha^–1 Ca, and 2177 kg ha^–1 Na. Soils of cohune association did not differ significantly from those of neighbouring hardwood dominated associations with the exception of Na which occurred in higher concentration because of bioaccumulation in the dominant. The results suggest that the growth habits and physiology of a dominant can strongly influence some of the ecological parameters used to describe aforest association.     

Die postembryonale Entwicklung und die funktionelle Anatomie des Gnathosoma in der Milbenfamilie Erythraeidae (Acarina,Prostigmata)

Zusammenfassung Das Gnathosoma von sieben Arten der Milbenfamilie Erythraeidae wurde untersucht. Die postembryonale Entwicklung der Cuticula-Strukturen, der Muskulatur und der Drüsen wird beschrieben.Das Gnathosoma der Larven weist Cheliceren auf, die aus Grundglied und klauenförmigem Digitus mobilis bestehen. Sie liegen dem Infracapitulum dorsal auf und inserieren an einem Paar Capitular-Apophysen. Bei den Protound Tritonymphen unterliegt das Gnathosoma der Histolyse und wird anschließend jeweils neu ausgebildet. Bei der Deutonymphe und beim Adultus ist es gegenüber der Larve stark abgewandelt: Die Tracheenstämme sind aus den Capitular-Apophysen der Larve abzuleiten. Die Stech-Cheliceren entsprechen dem Grundglied der larvalen Cheliceren, und ihre medialen Protraktoren gehen aus den Levator-Muskeln der Cheliceren der Larve hervor.Der Weg der Sekrete der podocephalischen und infracapitulären Drüsen über die Dorsalfläche des Infracapitulum erfährt mit dem Erwerb schmaler Stech-Cheliceren eine radikale Umstellung des Schutzes gegen Austrocknung. Während bei der Larve die breiten Cheliceren-Grundglieder den Sekretweg überdecken, und der Raum zwischen den Grundgliedern und dem Infracapi-tulum zusätzlich durch das ölartige Sekret der Intercheliceraldrüse ausgefüllt wird, schließen sich bei der Deutonymphe und beim Adultus die Lateralkiele der Genae über den Stech-Cheliceren zusammen, und der hintere Abschnitt des Cervix wird in das Idiosoma eingesenkt. Dadurch wird der Cervix zu einem internen Cervicalkanal umgebildet.Der Mundraum wird bei den aktiven Stadien durch die lipidartigen Sekrete der Buccal- und Labialdrüsen geschützt.Die phylogenetischen Beziehungen der Parasitengona innerhalb der Prostigmata und der Erythraeidae innerhalb der Parasitengona werden diskutiert.

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Postembryonic development and functional anatomy of the gnathosoma in the family Erythraeidae (Acarina, Prostigmata)

Summary The gnathosoma of seven species of the Erythraeidae was investigated. The postembryonic development of the cuticular structures, the musculature and the glands are described.In the larval gnathosoma, the chelicerae consist of a basal segment and a claw. They rest upon the dorsal surface of the infracapitulum. The basal segments are attached to a pair of capitular apophyses (sigmoid pieces). During the two molts larva to protonymph and deutonymph to tritonymph, the gnathosoma is histolysed. Directly afterwards it is rebuilt. Compared to the larva, in the deutonymph and in the adult it undergoes profound changes: The capitular apophyses are transformed to parts of the tracheae, the basal segment of each chelicera to a styliform chelicera, and the levator muscles of the chelicerae to medial protractors of the styliform chelicerae.The secretions of the podocephalic and infracapitular glands proceed along the dorsal surface of the infracapitulum to the buccal cavity. In the larva, the way of the secretions is protected against desiccation by the broad basal segments of the chelicerae, that cover the infracapitulum. In addition the oily secretion of the intercheliceral gland seals the space between the infracapitulum and the chelicerae. By obtaining styliform chelicerae the protection against desiccation undergoes a radical change: The lateral ridges of the infracapitulum join above the chelicerae, and the posterior part of the cervix is transferred back into the idiosoma. Thus the cervix is transformed into an internal canal.In the active instars, the buccal cavity is protected by the lipid-like secretions of the buccal glands and labial glands.The phylogenetic relationships of the Parasitengona within the Prostigmata, and of the Erythraeidae within the Parasitengona are discussed.

     

Improved analysis of hemagglutination assays for quantitation of lectin activity

A method to quantitate lectin activity based on hemagglutination assay in microtiter plates is described. In addition to the normal method of visual titer evaluation an electronic particle counter is used for counting of nonagglutinated cells in the microtiter wells; this allows a rapid, quantitative determination of the amount of lectin required to agglutinate 50% of the countable single cells. It is also recommended that counting results should be related to a standard curve of concanavalin A to improve the reproducibility of the assay.     

Cynoglossopsis somaliensis,sp. nov., und die GattungCynoglossopsis (Boraginaceae)

Cynoglossopsis somaliensis H. Riedl, sp. nov., is described as a new species of the hitherto monotypic genusCynoglossopsis Brand which is closest related toCynoglossum L. but has to be included inBoraginoideae-Eritrichieae from the way the nutlets are attached to the gynobasis.