Orientation and ingestion rates of larval Anopheles albimanus in response to floating particles

Response of fourth-instar larvae of Anopheles albimanus Wiedemann (Diptera: Culicidae) to food and inert particles floating at the water surface was studied. In a choice test, larvae aggregated at powdered organic materials (blood meal, liver powder alfalfa flour and wheat flour) but not at inert materials (kaolin, chalk or charcoal). Larvae responded positively to proteins as well as some carbohydrates, but not to cellulose. Retention of larvae at food sources found by random locomotion was found to be responsible for larval aggregation. Larvae ingested food particles 6–9 times faster than insert particles. The significance of Anopheline feeding behavior in the development of formulations of stomach toxins (bacterial agents) used in larval control is discussed.

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Zusammenfassung Die vorliegende Studie befasst sich mit Verhaltensreaktionen von Anopheles albimanus Viertlarven auf an der Wasseroberfläche schwimmende Partikel. Verteilung und Orientierung der Larven wurde in einer Wahlapparatur quantifiziert. Nach Auftrag von Alfalfamehl, Weizenmehl, Stärke, Blutmehl, Leberpulver und Fischmehl wurde Aggregation der Larven in den beköderten Fächern der Apparatur beobachtet. Sowohl Proteine (Casein) als auch einige Kohlehydrate (Amylose, Amylopectin) lösten Aggregationen der Larven aus. Im Unterschied dazu führte Auftrag von Kreide, Kaolin, Polyaethylenpulver, Talcum oder Cellulose nicht zu Aggregationen. Zur Beschreibung der Entstehung larvaler Aggregationen bei Futterstoffen wurden die Schwimmbewegungen der Larven in Anwesenheit von Weizenmehl als Ködersubstanz quantifiziert. Da keine Attraktion der Larven im Sinne einer gerichteten Schwimmbewegung beobachtet werden konnte, wird geschlussfolgert, dass sofortige Beendung der Suchaktivität der Larven bei zufällig gefundenen Futterquellen für die beobachteten Aggregationen bei organischen Substanzen verantwortlich ist.Die Fressraten der Larven bei Angebot verschiedener Substanzen im Überschuss wurde bestimmt. Larven fülten drei von insgesamt sechs Darmabschnitten innerhalb von 15–30 min bei Angebot von Futtersubstanzen, während die Füllung von nur zwei Darmabschnitten mit inerten Materialien erst nach 90–120 min zu beobachten war. Die Resultate werden in Bezug auf wasseroberflächengebundene Formulierungen von Frassgiften diskutiert. Inerte Trägersubstanzen werden wahrscheinlich wesentlich langsamer aufgenommen als Futtersubstanzen. Da An. albimanus Larven nicht von Futterquellen angezogen werden, ist eine rasche und wirksame Giftaufnahme besonders dann zu erwarten, wenn die gesamte Oberfläche der Brutgewässer mit toxinhaltigen Trägerpartikeln bedeckt werden kann.

     

The transepithelial potential difference in the gills of the fiddler crab,Uca tangeri: Influence of some inhibitors

Summary Euryhaline Crustacea living in dilute media, counterbalance the salt loss by active absorption of NaCl across the gill epithelium. To investigate the mechanisms involved in salt absorption, transeptithelial potential difference (PD_te) was measured in isolated, perfused gills of the fiddler crab,Uca tangeri. The influence of some specific inhibitors of epithelial ion transport on the PD_te was tested.With symmetrical conditions on both sides of the epithelium, the posterior gills ofUca tangeri showed a spontaneous PD_te of +5 to +10 mV, that is an active transport potential which was positive on the bath side as referred to the hemolymph side. This potential decreased considerably after application of KCN or 2,4-dinitrophenol (DNP) to the perfusion saline.Omission of K⁺ from the perfusion saline or addition of ouabain led to a reversible drop of the PD_te, suggesting that the absorption of Na⁺ and also of Cl^– is driven by the (Na⁺+K⁺)ATPase located in the basolateral membrane of the epithelial cells.Perfusion of the hemolymph space with saline containing diphenylamine-2-carboxylate (DPC) or the loop diuretic furosemide resulted in a decrease of the PD_te.After application of amiloride to the bath saline the PD_te increased. Half-maximum response to amiloride was reached at a concentration of about 10^–5 mol·l^–1. This suggests that one of the Na⁺ pathways across the apical membrane may consist of Na⁺ channels.Abbreviations PD _te transepithelial potential difference - DPC diphenylamine-2-carboxylate - R _ps resistance of perfusate shunt - R _te transepithelial resistance - R _in input resistance - DNP 2,4-dinitrophenol Parts of this study have been reported at the 1st Congress of Comparative Physiology and Biochemistry, Liège 1984, and at the Vth European Colloquium on Renal Physiology, Frankfurt, 1985     

A monozygotic twin pair with Rett syndrome

Summary A five-year-old, monozygotic, Turkish female twin pair with Rett syndrome is described. The twins are almost completely concordant in all clinical signs. This observation suggests a genetic cause of Rett syndrome.     

Fragile sites,chromosome evolution,and human neoplasia

Summary In a study of the possible relationship between human fragile sites, chromosomal rearrangements related to neoplasia, and chromosome regions involved in evolutionary changes, we have found that 17 fragile sites related to cancer, 15 fragile sites not related to cancer, and 17 non-fragile regions also related to human malignancy correspond or are close to bands involved in rearrangements that have taken place during chromosomal evolution in primates.     

Detection of Sap-Transmissible Viruses by ELISA in Tissue-Propagated Plants of Red Raspberry during in vitro Culture

Apple mosaic virus and raspberry bushy dwarf virus were detected by ELISA in plantlets of red raspberry still growing in vitro. The plantlets were derived from explants which were excised from plants infected by either of the viruses mentioned. Detection by ELISA of prune dwarf virus in 4-month-old in vitro cultures of sour cherry was reported earlier. Thus, application of ELISA to tissue cultured plants in vitro seems to be an appropriate method for early detection of virus-infected plant cultures.     

Microfungus-yeast mixed cultures in the degradation of amylaceous wastes. II: An experimental design for optimization of yeast production

Summary By means of an experimental factorial design the role of several culture conditions is described and its values determined for the maximum yeast production in mixed cultures ofAspergillus oryzae andRhodotorula glutinis.     

High intensity and blue light regulated expression of chimeric chalcone synthase genes in transgenic Arabidopsis thaliana plants

Summary To establish a genetic system for dissection of light-mediated signal transduction in plants, we analyzed the light wavelengths and promoter sequences responsible for the light-induced expression of the Arabidopsis thaliana chalcone synthase (CHS) promoter fused to the -glucuronidase (GUS) marker gene. Transgenic A. thaliana lines carrying 1975, 523, 186, and 17 by of the CHS promoter fused to the GUS gene were generated, and the expression of these chimeric genes was monitored in response to high intensity light in mature plants and to different wavelengths of light in seedlings. Fusion constructs containing 1975 and 523 by of CHS promoter sequence behaved identically to the endogenous CHS gene under all conditions. Expression of these constructs was induced specifically in response to high intensity white light and blue light. The response to blue light was seen in the presence of the P_fr form of phytochrome. Fusion constructs containing 186 by of promoter sequence showed reduced basal levels of expression and only weak stimulation by blue light but were induced significantly by high intensity white light. These analyses showed that the expression of the A. thaliana CHS gene is responsive to a specific blue light receptor and that sequences between — 523 and — 186 by are required for optimal basal and blue light-induced expression of this gene. The experiments lay the foundation for a simple genetic screen for light response mutants.     

Stearidonic acid (18:4ω3) in Primula florindae

Stearidonic acid (18:4ω3), which is reported to be of rare occurrence in the plant kingdom and which is of considerable dietary and pharmaceutical interest has been found in three closely related Primula species. It occurs, together with γ-linolenic acid (3–4% of the seed oil total fatty acids), in significant percentages in Primula florindae (11%), P. sikkimensis (14%) and P. alpicola (14%). 18:4(ω3 may also be of chemotaxonomic interest in the genus Primula, as high levels may be typical for section Sikkimensis. The only commercial plant source of stearidonic acid known so far is the seed oil of Ribes nigrum.     

Lipid accumulation inRhodotorula glutinis on sugar cane molasses in single-stage continuous culture

Microbial lipids produced byRhodotorula glutinis grown in continuous culture with molasses under nitrogen-limiting conditions were evaluated and the effects of growth rate on fatty acid composition were studied. As the growth rate decreased, cell biomass, lipid content and lipid yield gradually increased. The maximum lipid content recorded was 39% (w/w) of dry cell biomass at a dilution rate of 0.04 h^–1. The growth rate also affected fatty acid composition: oleic acid decreased with decreasing growth rate while stearic acid increased.