Smells like home :Olfactory landmarks in desert ant orientation

Unsere Umwelt ist voller Gerüche, anhand derer sich ein Organismus orientieren kann. Meist werden die Duftstoffe vom Ziel selbst abgegeben und dienen daher der Mehrheit der Insekten als Orientierungshilfe, Futter, einen geeigneten Eiablageplatz oder Partner zu finden. Umgebungsdüfte, das heißt Düfte, die weder im Zusammenhang mit Futter noch mit Fortpflanzung stehen, wurden bis jetzt hauptsächlich als Orientierungshilfe für Langstrecken diskutiert, wie sie zum Beispiel Vögel oder Fische zurücklegen. In der vorliegenden Arbeit wird die Verwendung von Umgebungsdüften in Form von olfaktorischen Landmarken erforscht. Die Tunesischen Wüstenameise Cataglyphis fortis erscheint auf den ersten Blick vielleicht nicht geeignet, geruchsgeleitete Orientierung zu untersuchen, da sie bis jetzt dank ihrer visuellen Orientierungsmechanismen Berühmtheit erlangte. Arbeiterinnen der Wüstenameise entfernen sich während ihrer Futtersuche auf gewundenen Pfaden und über erhebliche Distanzen von ihrem Nest. Im Gegensatz zu den meisten anderen Ameisenarten werden bei der Gattung Cataglyphis keine Pheromonspuren verwendet. Grund dafür sind die kleinen, zufällig verteilten Futterstücke und die hohen Bodentemperaturen, bei denen Pheromone schnell verdampfen würden. Der Rücklauf zum unauffälligen Nesteingang erfolgt auf dem kürzesten Weg mittels Wegintegration. Hierbei werden en route die zurückgelegten Distanzen und die eingeschlagenen Winkel kontinuierlich zu einem Heimvektor aufintegriert. Während ein Sonnenkompass zur Bestimmung der Richtung dient, wird die zurückgelegte Strecke mit Hilfe eines Schrittintegrators, der die Laufbewegung der Beine verarbeitet, bestimmt. In unmittelbarer Nähe des Nestes verlassen sich die Ameisen auf visuelle Landmarken. Nebst visuellen Landmarken fanden wir im unwirtlichen Lebensraum der Wüstenameisen stabile, ortsspezifische Duftmischungen. Da deren Komponenten von den Ameisen wahrgenommen werden können, schließen wir daraus, dass die untersuchten Bodenstrukturen potentiell als olfaktorische Landmarken genutzt werden können. Mit Hilfe eines Feldversuches konnten wir zeigen, dass C. fortis in der Lage ist, die Assoziation zwischen einem spezifischen Umgebungsduft und dem Nesteingang zu lernen und diese Information zu nutzen, um nach Hause zu finden. Ebenso vermochten die Ameisen, den gelernten Duft aus einer Mischung unbekannter Düfte zuerkennen

Smells like home: Desert ants, Cataglyphis fortis, use olfactory landmarks to pinpoint the nest

<p>Abstract</p> <p>Background</p> <p><it>Cataglyphis fortis </it>ants forage individually for dead arthropods in the inhospitable salt-pans of Tunisia. Locating the inconspicuous nest after a foraging run of more than 100 meters demands a remarkable orientation capability. As a result of high temperatures and the unpredictable distribution of food, <it>Cataglyphis </it>ants do not lay pheromone trails. Instead, path integration is the fundamental system of long-distance navigation. This system constantly informs a foraging ant about its position relative to the nest. In addition, the ants rely on visual landmarks as geocentric navigational cues to finally pinpoint the nest entrance.</p> <p>Results</p> <p>Apart from the visual cues within the ants' habitat, we found potential olfactory landmark information with different odour blends coupled to various ground structures. Here we show that <it>Cataglyphis </it>ants can use olfactory information in order to locate their nest entrance. Ants were trained to associate their nest entrance with a single odour. In a test situation, they focused their nest search on the position of the training odour but not on the positions of non-training odours. When trained to a single odour, the ants were able to recognise this odour within a mixture of four odours.</p> <p>Conclusion</p> <p>The uniform salt-pans become less homogenous if one takes olfactory landmarks into account. As <it>Cataglyphis </it>ants associate environmental odours with the nest entrance they can be said to use olfactory landmarks in the vicinity of the nest for homing.</p

Multiple sleep-wake disturbances after stroke predict an increased risk of cardio-cerebrovascular events or death - a prospective cohort study.

BACKGROUND In the general population, sleep-wake disturbances (SWD) have been shown to increase the risk of cardio- and cerebrovascular events (CCE) including death. Systematic studies on the effect of SWD on the risk of CCE in patients with stroke are lacking. METHODS Patients with acute ischemic stroke or transient ischemic attack (TIA) were prospectively recruited. Four SWD were analyzed: 1) sleep-disordered breathing (SDB) with respirography, 2) insomnia (by insomnia severity index, ISI), 3) restless legs syndrome (RLS, by International RLS Study Group rating scale) and 4) self-estimated sleep duration at 1 and 3 months. A "sleep burden index" as the mean of z-transformed values from assessments of these four SWD was created. The occurrence of CCE was recorded over a follow-up of 3.2±0.3 years (mean±standard deviation). RESULTS We assessed 437 patients (87% ischemic stroke, 13% TIA, 64% males) with a mean age of 65.1±13.0 years. SDB (respiratory event index, REI≥5) was present in 66.2% thereof. Insomnia (ISI≥10), RLS and extreme sleep duration affected 26.2%, 6.4% and 13.7% of the patients 3-month post-stroke. Seventy out of the 437 (16%) had at least one CCE during the follow-up. The sleep burden index was associated with a higher risk for subsequent CCE including death (Odds Ratio = 1.80 per index unit, 95% CI: 1.19-2.72, p=0.0056). CONCLUSION The presence of multiple SWDs constitutes a risk for subsequent CCE (including death) within the first three years following stroke. Larger systematic studies should assess the sleep burden index' utility for patients' risk stratification in clinical practice

A high-throughput behavioral paradigm for Drosophila olfaction - The Flywalk

How can odor-guided behavior of numerous individual Drosophila be assessed automatically with high temporal resolution? For this purpose we introduce the automatic integrated tracking and odor-delivery system Flywalk. In fifteen aligned small wind tunnels individual flies are exposed to repeated odor pulses, well defined in concentration and timing. The flies' positions are visually tracked, which allows quantification of the odor-evoked walking behavior with high temporal resolution of up to 100 ms. As a demonstration of Flywalk we show that the flies' behavior is odorant-specific; attractive odors elicit directed upwind movements, while repellent odors evoke decreased activity, followed by downwind movements. These changes in behavior differ between sexes. Furthermore our findings show that flies can evaluate the sex of a conspecific and males can determine a female's mating status based on olfactory cues. Consequently, Flywalk allows automatic screening of individual flies for their olfactory preference and sensitivity.This study was supported by fundings from the Max Planck Society to BSH

Nod1 also dampens <i>S.</i> Typhimurium Δ<i>msbB</i>-induced colitis.

<p>Streptomycin-pretreated C57Bl/6, <i>Nod1^−/−</i> and DKO mice were orally infected with <i>S.</i> Typhimurium Δ<i>msbB</i> for 2 days. (A) <i>S.</i> Typhimurium colonization of ileum, cecum and colon. Dashed line: limit of detection; cfu: colony forming units. (B) Pathology scores of infected ceca. Statistical analysis: 1way ANOVA with Bonferroni's multiple comparison post-test. * <i>p</i><0.05; ** <i>p</i><0.01. (C) H&E staining of infected cecum sections. Original magnification 200×; scale bars = 100 µm.</p

Impaired bacterial clearance and exacerbated inflammation in <i>Nod2^−/−</i> mice.

<p>Streptomycin-pretreated C57Bl/6 and <i>Nod2^−/−</i> mice were orally infected with wild-type <i>S.</i> Typhimurium or the Δ<i>msbB</i> mutant for the indicated times. <i>S.</i> Typhimurium Δ<i>msbB</i> colonization of the (A) ileum, (B) cecum and (C) colon. The dashed line indicates the limit of detection. cfu: colony forming units. Statistical analysis: one-way ANOVA with Tukey's multiple comparison post-test after logarithmic transformation. (D) <i>S.</i> Typhimurium wild-type colonization 2 days post infection. (E) Pathology scores of <i>S.</i> Typhimurium infected ceca and mock-infected controls at day 2 p.i., Statistical analysis: Student's <i>t</i> test. (F) H&E staining of <i>S.</i> Typhimurium Δ<i>msbB</i> infected cecal sections and mock-infected controls at day 2 p.i. Original magnification: 40×; scale bars = 500 µm; L = lumen, M = mucosa, SM = submucosa. * <i>p</i><0.05; ** <i>p</i><0.01; *** <i>p</i><0.001; ns: not significant.</p

<i>S.</i> Typhimurium Δ<i>msbB</i> infection induces pro-inflammatory gene expression in C57Bl/6 and <i>Nod2^−/−</i> mice.

<p>Gene expression of <i>mcp1</i> and <i>tnfα</i>, were measured by quantitative real-time PCR. Data were normalized to <i>gapdh</i> expression levels; Statistical analysis: 1way ANOVA with Tukey's multiple comparison post-test. * <i>p</i><0.05; ** <i>p</i><0.01; *** <i>p</i><0.001; ns: not significant.</p

Primer sequences used for quantitative real-time PCR.

<p>Primer sequences used for quantitative real-time PCR.</p

<i>Salmonella enterica</i> serovar Typhimurium Δ<i>msbB</i> Triggers Exacerbated Inflammation in Nod2 Deficient Mice

<div><p>The intracellular pathogen <i>Salmonella enterica</i> serovar Typhimurium causes intestinal inflammation characterized by edema, neutrophil influx and increased pro-inflammatory cytokine expression. A major bacterial factor inducing pro-inflammatory host responses is lipopolysaccharide (LPS). <i>S.</i> Typhimurium Δ<i>msbB</i> possesses a modified lipid A, has reduced virulence in mice, and is being considered as a potential anti-cancer vaccine strain. The lack of a late myristoyl transferase, encoded by MsbB leads to attenuated TLR4 stimulation. However, whether other host receptor pathways are also altered remains unclear. Nod1 and Nod2 are cytosolic pattern recognition receptors recognizing bacterial peptidoglycan. They play important roles in the host's immune response to enteric pathogens and in immune homeostasis. Here, we investigated how deletion of <i>msbB</i> affects <i>Salmonella's</i> interaction with Nod1 and Nod2. <i>S.</i> Typhimurium Δ <i>msbB</i>-induced inflammation was significantly exacerbated in <i>Nod2</i>^−/− mice compared to C57Bl/6 mice. In addition, <i>S.</i> Typhimurium Δ<i>msbB</i> maintained robust intestinal colonization in <i>Nod2</i>^−/− mice from day 2 to day 7 p.i., whereas colonization levels significantly decreased in C57Bl/6 mice during this time. Similarly, infection of <i>Nod1</i>^−/− and <i>Nod1/Nod2</i> double-knockout mice revealed that both Nod1 and Nod2 play a protective role in <i>S.</i> Typhimurium Δ<i>msbB</i>-induced colitis. To elucidate why <i>S.</i> Typhimurium Δ<i>msbB</i>, but not wild-type <i>S.</i> Typhimurium, induced an exacerbated inflammatory response in <i>Nod2</i>^−/− mice, we used HEK293 cells which were transiently transfected with pathogen recognition receptors. Stimulation of TLR2-transfected cells with <i>S.</i> Typhimurium Δ<i>msbB</i> resulted in increased IL-8 production compared to wild-type <i>S.</i> Typhimurium. Our results indicate that <i>S.</i> Typhimurium Δ<i>msbB</i> triggers exacerbated colitis in the absence of Nod1 and/or Nod2, which is likely due to increased TLR2 stimulation. How bacteria with “genetically detoxified” LPS stimulate various innate responses has important implications for the development of safe and effective bacterial vaccines and adjuvants.</p></div