Origin of asteroid rotation rates in catastrophic impacts

The rotation rates of asteroids, which are deduced from periodic fluctuations in their brightnesses, are controlled by mutual collisions. The link between asteroid spin and collision history is usually made with reference to impact experiments on centimetre-scale targets, where material strength governs the impact response. Recent work, however, indicates that for objects of the size of most observed asteroids (> or = 1 km in diameter), gravity rather than intrinsic strength controls the dynamic response to collisions. Here we explore this idea by modelling the effect of impacts on large gravitating bodies. We find that the fraction of a projectile's angular momentum that is retained by a target asteroid is both lower and more variable than expected from laboratory experiments, with spin evolution being dominated by 'catastrophic' collisions that eject approximately 50 per cent of the target's mass. The remnant of an initially non-rotating silicate asteroid that suffers such a collision rotates at a rate of approximately 2.9 per day, which is close to the observed mean asteroid rotation rate of approximately 2.5 d-1. Moreover, our calculations suggest that the observed trend in the mean spin frequency for different classes of asteroids (2.2 d-1 for C-type asteroids, 2.5 d-1 for S-type, and 4.0 d-1 for M-type) is due to increasing mean density, rather than increasing material strength.     

Evolution of intrinsic disorder in eukaryotic proteins

Conformational flexibility conferred though regions of intrinsic structural disorder allows proteins to behave as dynamic molecules. While it is well-known that intrinsically disordered regions can undergo disorder-to-order transitions in real-time as part of their function, we also are beginning to learn more about the dynamics of disorder-to-order transitions along evolutionary time-scales. Intrinsically disordered regions endow proteins with functional promiscuity, which is further enhanced by the ability of some of these regions to undergo real-time disorder-to-order transitions. Disorder content affects gene retention after whole genome duplication, but it is not necessarily conserved. Altered patterns of disorder resulting from evolutionary disorder-to-order transitions indicate that disorder evolves to modify function through refining stability, regulation, and interactions. Here, we review the evolution of intrinsically disordered regions in eukaryotic proteins. We discuss the interplay between secondary structure and disorder on evolutionary time-scales, the importance of disorder for eukaryotic proteome expansion and functional divergence, and the evolutionary dynamics of disorder.     

Brain-wide neuronal dynamics during motor adaptation in zebrafish

A fundamental question in neuroscience is how entire neural circuits generate behaviour and adapt it to changes in sensory feedback. Here we use two-photon calcium imaging to record the activity of large populations of neurons at the cellular level, throughout the brain of larval zebrafish expressing a genetically encoded calcium sensor, while the paralysed animals interact fictively with a virtual environment and rapidly adapt their motor output to changes in visual feedback. We decompose the network dynamics involved in adaptive locomotion into four types of neuronal response properties, and provide anatomical maps of the corresponding sites. A subset of these signals occurred during behavioural adjustments and are candidates for the functional elements that drive motor learning. Lesions to the inferior olive indicate a specific functional role for olivocerebellar circuitry in adaptive locomotion. This study enables the analysis of brain-wide dynamics at single-cell resolution during behaviour.     

A revision of the species of the Neoserica (sensu lato) vulpes group (Coleoptera: Scarabaeidae: Sericini)

This paper revises the species belonging to the Neoserica (sensu lato) vulpes group and results in one new combination, Neoserica (sensu lato) vulpes (Arrow, 1946) comb. nov., and 24 new species originating mainly from south-western China: N. baishuiensis sp. nov., N. baoshana sp. nov., N. biuncinata sp. nov., N. dundai sp. nov., N. ganhaiziana sp. nov., N. heishuiana sp. nov., N. kereni sp. nov., N. laocaiana sp. nov., N. lateriuncinata sp. nov., N. leiboensis sp. nov., N. luzhouana sp. nov., N. ningyuanensis sp. nov., N. nykli sp. nov., N. parausta sp. nov., N. pseudovulpes sp. nov., N. rubellula sp. nov., N. ruzickai sp. nov., N. shinkaisiensis sp. nov., N. sichuanica sp. nov., N. usta sp. nov., N. weishanensis sp. nov., N. xiaguanensis sp. nov., N. kunmingensis sp. nov. and N. yangjiapingensis sp. nov. A key to species and illustrations of genitalia and habitus of adults are given, including distribution maps of all species.

http://zoobank.org/urn:lsid:zoobank.org:pub:3FE6CC54-DB3A-4201-A6F9-332E4A397268     

Double deficiency of cathepsins B and L results in massive secretome alterations and suggests a degradative cathepsin-MMP axis

Endolysosomal cysteine cathepsins functionally cooperate. Cathepsin B (Ctsb) and L (Ctsl) double-knockout mice die 4 weeks after birth accompanied by (autophago-) lysosomal accumulations within neurons. Such accumulations are also observed in mouse embryonic fibroblasts (MEFs) deficient for Ctsb and Ctsl. Previous studies showed a strong impact of Ctsl on the MEF secretome. Here we show that Ctsb alone has only a mild influence on extracellular proteome composition. Protease cleavage sites dependent on Ctsb were identified by terminal amine isotopic labeling of substrates (TAILS), revealing a prominent yet mostly indirect impact on the extracellular proteolytic cleavages. To investigate the cooperation of Ctsb and Ctsl, we performed a quantitative secretome comparison of wild-type MEFs and Ctsb ^?/? Ctsl ^?/? MEFs. Deletion of both cathepsins led to drastic alterations in secretome composition, highlighting cooperative functionality. While many protein levels were decreased, immunodetection corroborated increased levels of matrix metalloproteinase (MMP)-2. Re-expression of Ctsl rescues MMP-2 abundance. Ctsl and to a much lesser extent Ctsb are able to degrade MMP-2 at acidic and neutral pH. Addition of active MMP-2 to the MEF secretome degrades proteins whose levels were also decreased by Ctsb and Ctsl double deficiency. These results suggest a degradative Ctsl—MMP-2 axis, resulting in increased MMP-2 levels upon cathepsin deficiency with subsequent degradation of secreted proteins such as collagen α-1 (I).     

Dietary fat and tissue cholesterol in female rats

Zusammenfassung Junge, ausgewachsene weibliche Ratten nahmen nach 8 Wochen fettreicher Diät mehr Fett auf als solche mit einer fettarmen Diät, aber gleichviel Kalorien. Bei Weibchen mit körperlicher Bewegung war der Cholesteringehalt des Blutes und des Gewebes höher als bei eingesperrten, sitzenden Tieren.

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Financial support for this study was provided by Nutrition Foundation Grant No. 383.     

Dietary carbohydrate and tissue cholesterol concentration in young rats

Zusammenfassung Drei Wochen alte männliche Ratten wurden auf eine Diät gesetzt, aus der die Kohlehydratquelle entweder aus Stärke oder einer Mischung von Kohlehydraten, die dem U. S.- Ernährungsstandard gleicht, bestand. Die Cholestrolansammlung im Gewebe der Ratten, denen nur Stärke gefüttert wurde, stand nicht in Verbindung mit der Gewichtszunahme; dagegen stand die Cholestrolzunahme im Gewebe jener Ratten, die mit einer Mischung von Kohlehydraten ernährt wurden, in direktem Zusammenhang mit der Zunahme in Gewicht.

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Financial support for this study was provided by Nutrition Foundation Grant No. 383.