Die antennalen Sensillen von Dipterenlarven und Larven verwandter Insektenordnungen

Sensillen sind „Kleinsinnesorgane“ der Arthropoda, die die Wahrnehmung einer Vielzahl unterschiedlicher Reize ermöglichen. Trotz großen Interesses an diesen Sinnesorganen ist die Frage nach den Homologieverhältnissen und der Evolution von Sensillen weitgehend ungeklärt. In der vorliegenden Arbeit werden daher die antennalen Sensillen von Larven aller größeren monophyletischen Gruppen der Diptera, sowie einiger mit den Diptera verwandter Holometabola raster- und transmissionselektronenmikroskopisch untersucht und vergleichend beschrieben. Die larvalen Antennen der Holometabola sind vor allem wegen der verhältnismäßig kleinen Anzahl von Sensillen besonders geeignete Modellobjekte, da dies die ultrastrukturelle Analyse des jeweils gesamten Sensilleninventars der Antennen ermöglicht. Obwohl die REM-Untersuchung der larvalen Antennen eine enorme äußere Vielfalt an Sensillenformen offenbart, zeigt die Analyse der inneren Ultrastruktur, daß die antennalen Sensillen von insgesamt 32 Dipterenarten und vier holometabolen Außengruppenvertretern nach strukturellen Kriterien nur zehn unterschiedlichen Sensillentypen zugeordnet werden können. Darüber hinaus lassen „modalitätsspezifische Strukturen“ Rückschlüsse auf die Funktionen der Sensillen zu. So deuten die Befunde darauf hin, daß es sich bei den Sensillentypen um olfaktorische, kontaktchemosensitive, gustatorische, thermo-, hygro- bzw. thermo-/hygrosensitive Sensillen, sowie um mechanosensitive Extero- und Propriorezeptoren handelt. Die Ergebnisse zeigen also, daß die larvalen Antennen, obwohl sie bei den Diptera durchschnittlich nur mit etwa zehn Sensillen ausgestattet sind, über ein ähnlich breites Spektrum der Reizwahrnehmung verfügen wie die imaginalen Antennen, die einige hundert oder gar tausend Sensillen besitzen. Rasterelektronenmikroskopisch konnten vor allem äußerliche Anpassungen der Antennen und Sensillen z.B. an Habitat und Lebensweise der Larve nachgewiesen werden; so sind lange Antennen, und mit ihnen meist auch überwiegend langgestreckte Sensillen, in aquatischen Lebensräumen eindeutig begünstigt, während terrestrisch lebende Larven, besonders in festen Substraten, wie z.B. Holz, eher kurze oder sogar plattenförmig reduzierte Antennen besitzen. Die vergleichende TEM-Untersuchung zeigt jedoch auch, daß Sensillen des gleichen Typs bei den jeweiligen Tieren sowohl in ihrer Position auf den Antennen, als auch in ihren strukturellen Merkmalen übereinstimmen. Nach dem Lagekriterium und dem Kriterium der spezifischen Qualität konnte so die Homologie einzelner antennaler Sensillen der Dipterenlarven für die gesamte Ordnung und teilweise sogar für die Holometabola wahrscheinlich gemacht werden. Über diesen homologen Sensillensatz hinaus konnte gezeigt werden, daß individuelle Sensillen - also kleinste Sinnesorgane - evolutiven Veränderungen unterliegen, die es erlauben ihr Schicksal im Verlauf der Phylogenese zu verfolgen. So belegen die Ergebnisse beispielsweise, daß der antennale Kontaktchemorezeptor „Peg“, bei den cyclorrhaphen Fliegen im Zusammenhang mit der Evolution des Antennen-Maxillar-Komplexes zum Maxillarpalpus verlagert wurde. Bei der vergleichenden Analyse aller antennalen Sensillen waren evolutive Tendenzen feststellbar, die in vielen Punkten mit den etablierten Stammbäumen der Diptera übereinstimmen, aber auch interessante Anregungen für derzeit noch ungeklärte Verwandtschaftsbeziehungen liefern. Für die meisten monophyletischen Gruppen der Diptera fanden sich charakteristische Merkmalskombinationen, die teilweise sogar als Synapomorphien gedeutet werden können. Bezogen auf offene Fragen der Dipterensystematik legen die Sensillenmerkmale beispielsweise ein Schwestergruppenverhältnis zwischen den Anisopodidae (Fenstermücken) und den „orthorrhaphen Fliegen“ nahe, wobei eine enge Verwandtschaftsbeziehung vor allem mit den Tabanomorpha (ohne die Vermileonidae) wahrscheinlich ist. Darüber hinaus führte ein Außengruppenvergleich zwischen den Diptera und einigen anderen Holometabola zu dem Ergebnis, daß der „Cone“ als Komplexchemosensillum ebenso zu den Grundplanmerkmalen holometaboler Insektenlarven gehört, wie zwei Thermo-/Hygrorezeptoren (lS3-Sensillen). Das bedeutet, daß diese individuellen Sensillen über fast 300 Mio. Jahre Evolution bis ins frühe Perm zurückverfolgt werden können

An Experimental Model for Resistance Exercise in Rodents

This study aimed to develop an equipment and system of resistance exercise (RE), based on squat-type exercise for rodents, with control of training variables. We developed an operant conditioning system composed of sound, light and feeding devices that allowed optimized RE performance by the animal. With this system, it is not necessary to impose fasting or electric shock for the animal to perform the task proposed (muscle contraction). Furthermore, it is possible to perform muscle function tests in vivo within the context of the exercise proposed and control variables such as intensity, volume (sets and repetitions), and exercise session length, rest interval between sets and repetitions, and concentric strength. Based on the experiments conducted, we demonstrated that the model proposed is able to perform more specific control of other RE variables, especially rest interval between sets and repetitions, and encourages the animal to exercise through short-term energy restriction and “disturbing” stimulus that do not promote alterations in body weight. Therefore, despite experimental limitations, we believe that this RE apparatus is closer to the physiological context observed in humans

An Experimental Model for Resistance Exercise in Rodents

This study aimed to develop an equipment and system of resistance exercise (RE), based on squat-type exercise for rodents, with control of training variables. We developed an operant conditioning system composed of sound, light and feeding devices that allowed optimized RE performance by the animal. With this system, it is not necessary to impose fasting or electric shock for the animal to perform the task proposed (muscle contraction). Furthermore, it is possible to perform muscle function tests in vivo within the context of the exercise proposed and control variables such as intensity, volume (sets and repetitions), and exercise session length, rest interval between sets and repetitions, and concentric strength. Based on the experiments conducted, we demonstrated that the model proposed is able to perform more specific control of other RE variables, especially rest interval between sets and repetitions, and encourages the animal to exercise through short-term energy restriction and “disturbing” stimulus that do not promote alterations in body weight. Therefore, despite experimental limitations, we believe that this RE apparatus is closer to the physiological context observed in humans

Structural Correlates of Rotavirus Cell Entry

Cell entry by non-enveloped viruses requires translocation into the cytosol of a macromolecular complex—for double-strand RNA viruses, a complete subviral particle. We have used live-cell fluorescence imaging to follow rotavirus entry and penetration into the cytosol of its ∼700 Å inner capsid particle (“double-layered particle”, DLP). We label with distinct fluorescent tags the DLP and each of the two outer-layer proteins and track the fates of each species as the particles bind and enter BSC-1 cells. Virions attach to their glycolipid receptors in the host cell membrane and rapidly become inaccessible to externally added agents; most particles that release their DLP into the cytosol have done so by ∼10 minutes, as detected by rapid diffusional motion of the DLP away from residual outer-layer proteins. Electron microscopy shows images of particles at various stages of engulfment into tightly fitting membrane invaginations, consistent with the interpretation that rotavirus particles drive their own uptake. Electron cryotomography of membrane-bound virions also shows closely wrapped membrane. Combined with high resolution structural information about the viral components, these observations suggest a molecular model for membrane disruption and DLP penetration

GASP III. JO36: a case of multiple environmental effects at play?

The so-called jellyfish galaxies are objects exhibiting disturbed morphology, mostly in the form of tails of gas stripped from the main body of the galaxy. Several works have strongly suggested ram pressure stripping to be the mechanism driving this phenomenon. Here, we focus on one of these objects, drawn from a sample of optically selected jellyfish galaxies, and use it to validate SINOPSIS, the spectral fitting code that will be used for the analysis of the GASP (GAs Stripping Phenomena in galaxies with MUSE) survey, and study the spatial distribution and physical properties of gas and stellar populations in this galaxy. We compare the model spectra to those obtained with GANDALF, a code with similar features widely used to interpret the kinematic of stars and gas in galaxies from IFU data. We find that SINOPSIS can reproduce the pixel-by-pixel spectra of this galaxy at least as good as GANDALF does, providing reliable estimates of the underlying stellar absorption to properly correct the nebular gas emission. Using these results, we find strong evidences of a double effect of ram pressure exerted by the intracluster medium onto the gas of the galaxy. A moderate burst of star formation, dating between 20 and 500 Myr ago and involving the outer parts of the galaxy more strongly than the inner regions, was likely induced by a first interaction of the galaxy with the intracluster medium. Stripping by ram pressure, plus probable gas depletion due to star formation, contributed to create a truncated ionized gas disk. The presence of an extended stellar tail on only one side of the disk, points instead to another kind of process, likely a gravitational interaction by a fly-by or a close encounter with another galaxy in the cluster.Comment: ApJ in press, 26 pages, 18 figure

DRC3 connects the N-DRC to dynein g to regulate flagellar waveform

The nexin-dynein regulatory complex (N-DRC), which is a major hub for the control of flagellar motility, contains at least 11 different subunits. A major challenge is to determine the location and function of each of these subunits within the N-DRC. We characterized a Chlamydomonas mutant defective in the N-DRC subunit DRC3. Of the known N-DRC subunits, the drc3 mutant is missing only DRC3. Like other N-DRC mutants, the drc3 mutant has a defect in flagellar motility. However, in contrast to other mutations affecting the N-DRC, drc3 does not suppress flagellar paralysis caused by loss of radial spokes. Cryo-electron tomography revealed that the drc3 mutant lacks a portion of the N-DRC linker domain, including the L1 protrusion, part of the distal lobe, and the connection between these two structures, thus localizing DRC3 to this part of the N-DRC. This and additional considerations enable us to assign DRC3 to the L1 protrusion. Because the L1 protrusion is the only non-dynein structure in contact with the dynein g motor domain in wild-type axonemes and this is the only N-DRC-dynein connection missing in the drc3 mutant, we conclude that DRC3 interacts with dynein g to regulate flagellar waveform

Absolute proteomic quantification reveals design principles of sperm flagellar chemosensation

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Troetschel, C., Hamzeh, H., Alvarez, L., Pascal, R., Lavryk, F., Boenigk, W., Koerschen, H. G., Mueller, A., Poetsch, A., Rennhack, A., Gui, L., Nicastro, D., Struenker, T., Seifert, R., & Kaupp, U. B. Absolute proteomic quantification reveals design principles of sperm flagellar chemosensation. Embo Journal, 39(4), (2020): e102723, doi:10.15252/embj.2019102723.Cilia serve as cellular antennae that translate sensory information into physiological responses. In the sperm flagellum, a single chemoattractant molecule can trigger a Ca2+ rise that controls motility. The mechanisms underlying such ultra‐sensitivity are ill‐defined. Here, we determine by mass spectrometry the copy number of nineteen chemosensory signaling proteins in sperm flagella from the sea urchin Arbacia punctulata. Proteins are up to 1,000‐fold more abundant than the free cellular messengers cAMP, cGMP, H+, and Ca2+. Opto‐chemical techniques show that high protein concentrations kinetically compartmentalize the flagellum: Within milliseconds, cGMP is relayed from the receptor guanylate cyclase to a cGMP‐gated channel that serves as a perfect chemo‐electrical transducer. cGMP is rapidly hydrolyzed, possibly via “substrate channeling” from the channel to the phosphodiesterase PDE5. The channel/PDE5 tandem encodes cGMP turnover rates rather than concentrations. The rate‐detection mechanism allows continuous stimulus sampling over a wide dynamic range. The textbook notion of signal amplification—few enzyme molecules process many messenger molecules—does not hold for sperm flagella. Instead, high protein concentrations ascertain messenger detection. Similar mechanisms may occur in other small compartments like primary cilia or dendritic spines.We thank Heike Krause for preparing the manuscript. Financial support by the Deutsche Forschungsgemeinschaft (DFG) via the priority program SPP 1726 “Microswimmers” and the Cluster of Excellence 1023 “ImmunoSensation” is gratefully acknowledged. We thank D. Stoddard for management of the UTSW cryo‐electron microscope facility, which is funded in part by a Cancer Prevention and Research Institute of Texas (CPRIT) Core Facility Award (RP170644). This study was supported by HHS|National Institutes of Health (NIH) grant R01 GM083122 and by CPRIT grant RR140082 to D. Nicastro