Mechanism of the fluorescent light induced suppression of Curly phenotype in Drosophila melanogaster.

A dominant mutation Curly (Cy), frequently used as a marker on the second chromosome in Drosophila melanogaster, was previously shown to be suppressed by several factors, including larval crowding, low temperature, and fluorescent light. While the first two factors affect this mutation only partially, fluorescent tube exposed flies exhibit an almost completely suppressed (wild type) phenotype. This suppressive effect is the result of a combination of the electric field and light, both factors being produced by common fluorescent tubes. In this study, experiments were carried out to clarify the basic mechanism of this unique phenomenon. Two fluorescent tube sensitive stages of Drosophila development were found in the second half of embryonic development and first half of the pupal stage. Riboflavin, which is administered to Drosophila larvae with yeast, and decomposed by light, seems to play a key role in this phenomenon. In a medium lacking riboflavin caused by light exposure, Cy expression is inhibited by the action of electric field. Positive results of experiments with lithium ions, which block the opening of Ca(2+) channels, support the hypothesis that electromagnetic fields may alter ion currents during ontogenic development of Drosophila, and thus influence, expression of the Cy gene. Also, fluorescent light induces an overexpression of a specific protein in the imaginal wing disc of Cy pupae.

Mortality caused by experimental infection with the yeast Candida haemulonii in the adults of Ornithodoros moubata (Acarina: Argasidae).

A relatively high rate of mortality among engorged females of Ornithodoros moubata (Murray, 1877) was observed in our laboratory colony. The general aim of the study was to identify the causative agent responsible for this mortality. The diagnostic tests were performed by Yeast Identification Service (CBS-Delft, Netherlands) and the pathogen was identified as the yeast Candida haemulonii (van Uden et Kolipinski, 1962) Meyer et Yarrovi, 1978. The artificial infection study was performed by intrahaemocoelic inoculation of yeast suspension, resulting in a mortality of 37%. The maximum mortality of ticks infected per os by contaminated blood meal was 13%. Re-isolated yeast cells from haemolymph of dead and paralysed ticks were apparently identical with primary yeast cells, without loosing reproductive abilities. An occasional formation of elongated chains of yeast cells (pseudomycelium) was recorded. The majority of ticks infected in both experiments mentioned above survived and displayed no evident symptoms of the infection. The presence of yeast cells in the haemolymph of surviving ticks was not detected. The in vitro phagocytosis assay performed with FITC-labelled yeast cells showed that about 4% of tick haemocytes were phagocytically active against the pathogenic yeast cells. Thus phagocytosis seems to be a potent defence reaction against spreading and multiplying of the yeast C. haemulonii within the tick haemocoel.

Purification and characterization of the lysozyme from the gut of the soft tick Ornithodoros moubata.

The gut of the adult soft ticks Ornithodoros moubata displays high lytic activity against the bacteria Micrococcus luteus. The activity differed in the range of two orders of magnitude among individual animals and increased on average 4 fold during the first week following ingestion. In homogenates of first instar nymphs the activity was much lower increasing exponentially as nymphs neared the first molt. The protein responsible for this activity was purified out of gut contents of adult ticks by means of affinity adsorption on magnetic-chitin followed by two chromatography steps on cation exchange FPLC column MonoS. The homogeneous active protein has a mass of 14006 +/- 20 Daltons as determined by MALDI-TOF mass spectrometry. The N-terminal amino-acid sequence of this protein is K-V-Y-D-R-C-S-L-A-S-E-L-R with the highest similarity to the lysozyme from liver of rainbow trout and to lysozymes from digestive tracts of several mammals. The motif DRCSLA is specific for the digestive lysozymes of several dipteran insects. Based on this evidence, we have identified the protein as the tick gut lysozyme. The tick gut lysozyme has a pI near 9.7 and retains its full activity after treatment at 60 degrees C for 30 minutes. The pH optimum of the tick lysozyme was in the range from pH 5-7. Only marginal activity could be detected at pH > 8 which raises the question about the function of lysozyme in anti-bacterial defense in the environment of the tick gut.

A putative host cell receptor for tick-borne encephalitis virus identified by anti-idiotypic antibodies and virus affinoblotting.

Anti-idotypic monoclonal antibodies (anti-ID MAbs) were made against two mouse MAbs that neutralize the infectivity of the tick-borne encephalitis (TBE) virus. Three of the anti-ID MAbs (1) inhibited the binding of respective idiotypic MAb to the TBE virus antigen, (2) inhibited the infectivity of TBE virus when preincubated with virus-susceptible cells, and (3) bound to the surface of virus-susceptible but not virus-nonsusceptible cells. They recognized a 35-kD protein in immunoblotting analysis. Identification of this protein as a component of a putative TBE virus receptor was supported by the viroblot technique. In this assay, two polypeptide signals of 35 and 18 kD were obtained after incubation of blotted cell membrane proteins with the TBE virion antigen.

Animal virus receptors.

The term 'receptor' is generally accepted as the cell-surface component that participates in virus binding and facilitates subsequent viral infection. Recent advances in technology have permitted the identification of several virus receptors, increasing our understanding of the significance of this initial virus-cell and virus-host interaction. Virus binding was previously considered to involve simple recognition and attachment to a single cell surface molecule by virus attachment proteins. The classical concept of these as single entities that participate in a lock-and-key-type process has been superseded by new data indicating that binding can be a multistep process, often involving different virus-attachment proteins and more than one host-cell receptor.

Lectins and tick-pathogen interactions: a minireview.

Lectins and their glycosylated receptors in a system of the tick-transmitted pathogen are the addressed topics which the minireview is dealing with. They participate in the reciprocal protein-saccharide interactions in the transmission of the causative agents of the tick-borne encephalitis and Lyme borreliosis by the ticks. Functional significance of the tick tissue specific lectins as well the lectins/aggulutinis of the transmitted pathogens in molecular ecology of the tick borne diseases has been shown.