Ectoparasitic Acugutturid Nematodes of Adult Lepidoptera

Noctuidonema guyaneme is an interesting ectoparasite of adult Lepidoptera that feeds on hosts from at least five families with its long stylet. Noctuidonema guyanense spends its entire life on the adult moth and is sustained as it is passed from moth to moth during host mating. Overlapping host generations are essential for parasite survival. This nematode occurs throughout tropical and subtropical America and is transported by at least one of its hosts, Spodoptera frugiperda, during migration to northern sites in the United States each spring. Noctuidonema guyanense debilitates its hosts. Research conducted to help determine the biological control importance of this nematode is reviewed. Two additional species, N. daptria and N. dibolia, are now known for Noctuidonema.     

Discrimination of phase spectra in complex sounds by the bullfrog (Rana catesbeiana)

1. Male bullfrogs at two different natural calling sites were presented with playbacks of synthetic advertisement calls differing in phase spectra. Sounds were presented in a ABA design to analyze the ability of the animals to perceive changes in repeated series of stimuli.
2. The number of individual croaks in an answering call significantly increased over repeated presentations of two of the three stimulus phase types in condition A1. There were significantly fewer croaks to the third stimulus. These data suggest that two stimuli were perceived in a similar manner.
3. Latency of calling to stimuli presented in conditions A and B changed in response to shifts in phase spectrum at a low density calling site. These differences were significant when comparing latency to playbacks where shifts in the phase spectrum changed the temporal fine-structure and waveform periodicity of the stimulus.
4. The increase in number of croaks and decrease in response latency across condition A1 and the increase in latency in condition B suggest that discrimination may take the form of stimulus-specific sensitization. In this context, sensitization might reflect an increase in arousal due to repeated presentation of a salient stimulus.
5. The operation of a hypothetical ‘mating call detector,’ based on linear summation of temporal responses from the eighth nerve, provides output similar to the behavioral results.

     

Laboratory gloves as a source of trace element contamination

Contamination in a trace element laboratory can come from a variety of sources, including laboratory gloves. Therefore, vinyl and latex gloves were obtained from as many manufacturers as would supply gloves. These gloves were either prepared for acid-washing and subsequent soaking in an acid solution, or immersed in an acid solution for a duration of either 1 min or 1 h. Incubation washes were analyzed for a variety of trace elements by flame atomic abosrption spectroscopy (AAS) or inductively coupled mass spectrometry (ICP-MS). Results indicated that only three brands of vinyl gloves were acceptable for use in a trace element laboratory, whereas others had contamination of different elements. Latex gloves contained such high levels of biologically important elements that they were not considered suitable for routine trace element work. Vinyl gloves of choice should be routinely acid-washed before use in a trace element laboratory.     

Fungal colonization of synthetic substrates for use in space craft

Summary Materials being used or considered for use in space flight were examined for their susceptibility to fungal colonization. The materials included soft goods (clothing) and insulation and fabrication products such as Velcro^® attachments and elastic cord binders. Materials were exposed for at least 28 days in a highhumidity chamber colonized with over 50 species of fungi, including those species recommended for determining recalcitrance of materials to fungal biodegradation. At least nine of 25 products demonstrated extensive microscopic colonization by fungi, mostly byAcremonium obclavatum. Challenge procedures that rely on observations with the unaided eye, or 40×magnification of growth by a restricted number of fungal species with a cellulosic substrate as a positive control, are insufficient for determining the resistance of synthetic substrates to fungal colonization.     

Fungal production of volatiles during growth on fiberglass.

Acoustic and thermal fiberglass insulation materials used in heating, ventilation, and air-conditioning systems were colonized with fungi in laboratory chambers. The mixed fungal population, principally Aspergillus versicolor, Acremonium obclavatum, and Cladosporium herbarum, produced odoriferous volatiles, including 2-ethyl hexanol, cyclohexane, and benzene. These volatiles may be related to poor indoor air quality and the sick building syndrome.     

L-Alanine absorption in human intestinal Caco-2 cells driven by the proton electrochemical gradient

In human Caco-2 intestinal epithelial layers, xxxl-alanine absorption can be energized by a proton gradient across the brush-border membrane. Acidification of the apical medium, even in Na⁺-free media, is associated with a saturable net transepithelial absorption of xxxl-alanine. xxxl-Alanine transport causes cytosolic acidification consistent with proton/amino acid symport. xxxl-Alanine transport in Na⁺-free media is rheogenic, stimulating an inward short-circuit current in voltageclamped epithelial monolayers. By measurement of rapid xxxl-alanine influx across the apical membrane, xxxl-alanine-stimulated inward short-circuit current and intracellular acidification in the same cell batch, we estimate xxxl-alanine/proton stoichiometry to be 10.62 ±0.25 (xxxsd) (short-circuit current) or 10.73 ±0.19 (intracellular acidification). From competition studies, it is likely that xxxl-proline, -aminoisobutyric acid, and -alanine, but not xxxl-valine and xxxl-serine, are substrates for protonlinked, substrate transport in the brush border of Caco-2 cells.This study was supported by the Wellcome Trust (to D.T.T. and N.L.S.) and the LINK Programme in Selective Drug Delivery and Targeting (funded by the SERC/MRC/DTI and Industry). Charlotte Ward gave excellent technical assistance.     

Repression of Hybrid Dysgenesis in Drosophila Melanogaster by Individual Naturally Occurring P Elements

Individual P elements that were genetically isolated from wild-type strains were tested for their abilities to repress two aspects of hybrid dysgenesis: gonadal dysgenesis and mutability of a double-P element-insertion allele of the singed locus (sn(w)). These elements were also characterized by Southern blotting, polymerase chain reaction amplification and DNA sequencing. Three of the elements were 1.1-kb KP elements, one was a 1.2-kb element called D50, and one was a 0.5-kb element called SP. These three types of elements could encode polypeptides of 207, 204, and 14 amino acids, respectively. Gonadal dysgenesis was repressed by two of the KP elements (denoted KP(1) and KP(6)) and by SP, but not by the third KP element (KP(D)), nor by D50. Repression of gonadal dysgenesis was mediated by a maternal effect, or by a combination of zygotic and maternal effects generated by the P elements themselves. The mutability of sn(w) was repressed by the KP(1) and KP(6) elements, by D50 and by SP, but not by KP(D); however, the SP element repressed sn(w) mutability only when the transposase came from complete P elements and the D50 element repressed it only when the transposase came from the modified P element known as Δ2-3. In all cases, repression of sn(w) mutability appeared to be mediated by a zygotic effect of the isolated P element. Each of the isolated elements was also tested for its ability to suppress the phenotype of a P-insertion mutation of the vestigial locus (vg(21-3)). D50 was a moderate suppressor whereas SP and the three KP elements had little or no effect. These results indicate that each isolated P element had its own profile of repression and suppression abilities. It is suggested that these abilities may be mediated by P-encoded polypeptides or by antisense P RNAs initiated from external genomic promoters.     

Topoisomerase activity associated with SV40 large tumor antigen.

Purified preparations of simian virus 40 (SV40) large tumor antigen (LT) from three different sources, including LT expressed from a recombinant baculovirus, were found to relax negatively supercoiled cyclic DNA molecules, whether or not they contained SV40 sequences. Relaxation was stimulated by MgCl2 but not by ATP, and inhibited by camptothecin, suggesting the involvement of an enzymatic activity similar to that of topoisomerase I (topo I). However, the pH requirements for relaxation by respectively LT and topo I are different. Also, antibodies reacting with LT inhibited relaxation by preparations of LT but not topo I, whereas antibodies inhibiting relaxation by topo I had no effect on relaxation by LT. Reconstruction experiments suggested that both procedures used to purify LT, immunoaffinity chromatography and DEAE-Sepharose chromatography, separate topo I from LT. Finally, relaxing activity was found in over 40 preparations of LT, and in the few instances where activity could not be found, it probably had been lost during storage, rather than absent from the start. Whereas these results seem to exclude that the activity being detected is that of a contaminant of LT, they would be consistent with this activity being that of a stable topo-LT complex, or else intrinsic to LT itself.     

Epithelial M cells in the rabbit caecal lymphoid patch display distinctive surface characteristics

The follicle-associated epithelium (FAE) in the rabbit caecal lymphoid patch is characterised by the presence of membranous (M) cells, which are believed to be functionally equivalent to those present at other sites of gut-associated lymphoid tissue (GALT). Caecal patch M cells display distinctive features compared with those of other GALT sites, despite similar general morphology and expression of the M cell marker vimentin, suggesting marked heterogeneity in the apical surface of M cells at discrete GALT sites. Electron microscopy reveals that rabbit caecal patch M cells differ from those in the small intestinal Peyer's patch FAE: the former have a prominent aspect within the epithelium and possess microvilli which are longer than those of adjacent enterocytes. Many of the M cells in peripheral regions of the caecal patch FAE are not associated with leucocytes and may thus represent an immature M cell population. The M cells are also histochemically distinct from adjacent enterocytes and from Peyer's patch M cells, showing greater expression of brush-border alkaline phosphatase activity and affinity for certain lectins (peanut and wheat germ agglutinins, Bandeiraea simplicifolia agglutinin II). The differences in the brush-border morphology and glycocalyx structure between M cells at different GALT sites may affect their function at these sites by influencing the interaction of luminal antigens and microorganisms with the M cell surface. The present data also support the hypothesis that M cells arise directly from differentiation of crypt stem cells and not from the transformation of existing fully differentiated enterocytes.     

Identification of a wheat (Triticum aestivum) cell line lacking a specific divalent cation requirement

A wheat (Triticum aestivum L.) cell line, derived from anther culture of an F₁ hybrid, has exogenous Ca²⁺, to that of calcium-dependent cells grown on complete medium. The calcium-independent cell line has been grown in the absence of Ca²⁺ for more than 1.5 years. The cell line grew at a rate similar to that on complete medium for up to 12 weeks, if supplied with any one of the divalent cations, Ca²⁺, Mg²⁺, Mn²⁺, Zn²⁺, Cu²⁺ or Co²⁺, but declined and appeared necrotic when all 6 of these were removed from the medium. The calcium-independence trait, while identified in tissue culture, was also observed in germinated immature embryos of the same hybrid and one of its parental inbred lines.