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 Thatcher illusion in humans and monkeys

Primates possess the remarkable ability to differentiate faces of group members and to extract relevant information about the individual directly from the face. Recognition of conspecific faces is achieved by means of holistic processing, i.e. the processing of the face as an unparsed, perceptual whole, rather than as the collection of independent features (part-based processing). The most striking example of holistic processing is the Thatcher illusion. Local changes in facial features are hardly noticeable when the whole face is inverted (rotated 180°), but strikingly grotesque when the face is upright. This effect can be explained by a lack of processing capabilities for locally rotated facial features when the face is turned upside down. Recently, a Thatcher illusion was described in the macaque monkey analogous to that known from human investigations. Using a habituation paradigm combined with eye tracking, we address the critical follow-up questions raised in the aforementioned study to show the Thatcher illusion as a function of the observer''s species (humans and macaques), the stimulus'' species (humans and macaques) and the level of perceptual expertise (novice, expert).     

The cytomegalovirus enhancer: a pan-active control element in transgenic mice.

In an effort to identify widely active positive regulatory elements, we have examined the action of the cytomegalovirus enhancer-promoter in transgenic mice. These elements activated expression in 24 of 28 tissues tested. The greatest expression was observed in the heart, kidney, brain, and testis. Maximum expression further localized to specific cells within the heart and kidney.     

Functional asymmetry of the F0 motor in bacterial ATP synthases

F₁F₀ ATP synthases use the electrochemical potential of H⁺ or Na⁺ across biological membranes to synthesize ATP by a rotary mechanism. In bacteria, the enzymes can act in reverse as ATP-driven ion pumps creating the indispensable membrane potential. Here, we demonstrate that the F₀ parts of a Na⁺- and H⁺-dependent enzyme display major asymmetries with respect to their mode of operation, reflected by the requirement of ∼100 times higher Na⁺ or H⁺ concentrations for the synthesis compared with the hydrolysis of ATP. A similar asymmetry is observed during ion transport through isolated F₀ parts, indicating different affinities for the binding sites in the a/c interface. Together with further data, we propose a model that provides a rationale for a differential usage of membrane potential and ion gradient during ATP synthesis as observed experimentally. The functional asymmetry might also reflect an important property of the ATP synthesis mechanism in vivo . In Escherichia coli , we observed respiratory chain-driven ATP production at pH 7–8, while P -site pH values < 6.5 were required for ATP synthesis in vitro . This discrepancy is discussed with respect to the hypothesis that during respiration lateral proton diffusion could lead to significant acidification at the membrane surface.     

Flow separation, an important mechanism in the formation of mean pulmonary pressure during high-frequency oscillation

Mean pressures within the lungs and lung volume, respectively, are clinically important parameters. During ventilation by way of high-frequency oscillation (HFO), these parameters have been shown to be strongly frequency dependent. To identify mechanisms leading to mean pressure formation during HFO, findings of the theory of stationary flow were extended to oscillatory flow by a quasi-stationary approach. To confirm the theoretical findings, in-vitro experiments on HFO-models were performed. Flow separation was found to be an important mechanism in the formation of mean pressure. Flow separation causes a significant flow resistance, which may be distinctly different for in- and outflow. During oscillatory flow, a mean pressure difference thus results. This mechanism is of particular importance in bifurcations, which are present in the HFO-circuit as well as in the airways. With the direction-dependent flow separation, a general mechanism was found, which accounts for differing mean pressure values within the lungs with different HFO-circuits. This mechanism also contributes to interregionally different mean pressure values within the lungs.     

Resolution of d,l-menthol by interesterification with triacetin using the free and immobilized lipase of Candida cylindracea

Summary Interesterification in isooctane with triacetin as an acyl donor was found to be a new and effective method of racemic resolution of d,l-menthol, when using the free and immobilized lipase of Candida cylindracea. No water was produced by this highly stereoselective type of reaction in contrast to ester synthesis with acetic acid as an acyl donor. Even with diacetin no possible back reaction occurred and the enzyme was easily separated from the reaction solution as opposed to ester hydrolysis in aqueous systems. Inhibition of interesterification was caused by increasing concentrations of the acyl donor triacetin by more than 10 mmol·l^-1 on the one hand, and especially by diacetin on the other hand. The reaction product menthyl acetate had no influence. By adding water the interesterification activity of the lipase was reduced significantly. An alteration of the acyl donor triacetin to longerchained triglycerides caused changes in higher specific activities but poor enantioselectivities of the products, as in the case of ester synthesis starting from longer-chained organic acids.Dedicated to Prof. Dr. Fritz Wagner on the occasion of his 60th birthday     

Keratin and vimentin expression in early organogenesis of the rabbit embryo

Summary The expression of vimentin and keratins is analysed in the early postimplantation embryo of the rabbit at 11 days post conceptionem (d.p.c.) using a panel of monoclonal antibodies specific for single intermediate filament polypeptides (keratins 7, 8, 18, 19 and vimentin) and a pan-epithelial monoclonal keratin antibody. Electrophoretic separation of cytoskeletal preparations obtained from embryonic tissues, in combination with immunoblotting of the resulting polypeptide bands, demonstrates the presence of the rabbit equivalents of human keratins 8, 18, and vimentin in 11-day-old rabbit embryonic tissues. Immunohistochemical staining shows that several embryonic epithelia such as notochord, surface ectoderm, primitive intestinal tube, and mesonephric duct, express keratins, while others (neural tube, dermomyotome) express vimentin, and a third group (coelomic epithelia) can express both. Similarly, of the mesenchymal tissues sclerotomal mesenchyme expresses vimentin, while somatopleuric mesenchyme (abdominal wall) expresses keratins, and splanchnopleuric mesenchyme (dorsal mesentery) expresses both keratins and vimentin. While these results are in accordance with most results of keratin and vimentin expression in embryos of other species, they stand against the common concept of keratin and vimentin specificity in adult vertebrate tissues. Furthermore, keratin and vimentin are not expressed in accordance with germ layer origin of tissues in the mammalian embryo; rather the expression of these proteins seems to be related to cellular function during embryonic development.Supported by the Deutsche Forschungsgemeinschaft and by the Netherlands Cancer Foundation