Competitive feeding behaviours in captive Terrapene c. carolina

Two groups of box turtles (Terrapene carolina carolina) were observed for 15 weeks in pens where they competed for daily rations of meal worms. Hierarchies based on competitive-encounters won or lost were reliably stable and were accompanied by behaviours ranging from biting to pushing. Hierarchies based on precedence to initial meal worms within sessions were not reliable as the turtles did not anticipate or respond quickly to the onset of food availablity.     

Modelling the Cell Cycle and Cell Movement in Multicellular Tumour Spheroids

This paper analyses a recent mathematical model of avascular tumour spheroid growth which accounts for both cell cycle dynamics and chemotactic driven cell movement. The model considers cells to exist in one of two compartments: proliferating and quiescent, as well as accounting for necrosis and apoptosis. One particular focus of this paper is the behaviour created when proliferating and quiescent cells have different chemotactic responses to an extracellular nutrient supply. Two very different steady-state behaviours are identified corresponding to those cases where proliferating cells move either more quickly or more slowly than quiescent cells in response to a gradient in the extracellular nutrient supply. The case where proliferating cells move more rapidly leads to the commonly accepted spheroid structure of a thin layer of proliferating cells surrounding an inner quiescent core. In the case where proliferating cells move more slowly than quiescent cells the model predicts an interesting structure of a thin layer of quiescent cells surrounding an inner core of proliferating and quiescent cells. The sensitivity of this tumour structure to the cell cycle model parameters is also discussed. In particular variations in the steady-state size of the tumour and the types of transient behaviour are explored. The model reveals interesting transient behaviour with sharply delineated regions of proliferating and quiescent cells.     

Regulation of active and quiescent somatic stem cells by Notch signaling

Somatic stem/progenitor cells actively proliferate and give rise to different types of mature cells (active state) in embryonic tissues while they are mostly dormant (quiescent state) in many adult tissues. Notch signaling is known to regulate both active and quiescent states of somatic stem cells, but how it regulates these different states is unknown. Recent studies revealed that the Notch effector Hes1 is expressed differently during the active and quiescent states during neurogenesis and myogenesis: high in the quiescent state and oscillatory in the active state. When the Hes1 expression level is high, both Ascl1 and MyoD expression are continuously suppressed. By contrast, when Hes1 expression oscillates, it periodically represses expression of the neurogenic factor Ascl1 and the myogenic factor MyoD, thereby driving Ascl1 and MyoD oscillations. High levels of Hes1 and the resultant Ascl1 suppression promote the quiescent state of neural stem cells, while Hes1 oscillation-dependent Ascl1 oscillations regulate their active state. Similarly, in satellite cells of muscles, known adult muscle stem cells, high levels of Hes1 and the resultant MyoD suppression seem to promote their quiescent state, while Hes1 oscillation-dependent MyoD oscillations activate their proliferation and differentiation. Therefore, the expression dynamics of Hes1 is a key regulatory mechanism of generating and maintaining active/quiescent stem cell states.     

A preliminary analysis of sleep-like states in the cuttlefish Sepia officinalis

Sleep has been observed in several invertebrate species, but its presence in marine invertebrates is relatively unexplored. Rapid-eye-movement (REM) sleep has only been observed in vertebrates. We investigated whether the cuttlefish Sepia officinalis displays sleep-like states. We find that cuttlefish exhibit frequent quiescent periods that are homeostatically regulated, satisfying two criteria for sleep. In addition, cuttlefish transiently display a quiescent state with rapid eye movements, changes in body coloration and twitching of the arms, that is possibly analogous to REM sleep. Our findings thus suggest that at least two different sleep-like states may exist in Sepia officinalis.     

Nemertean predation on the tropical fiddler crab Uca musica

We saw 79 predatory interactions between a new speciesof monostiliferous, suctorial hoplonemertean and thefiddler crabs Uca musica (77 cases) and U.stenodactylus (2 cases). At an intertidal sand barin the Pacific entrance of the Panama Canal, worms ateabout 0.1% of the adult crab population per day. Themode of attack and the spatial and temporaldistributions of interactions suggest the worm is anambush predator. When struck by a worms sticky,mucous-covered proboscis, crabs produced copious foamfrom their buccal area. Mucous-laden crabs thatescaped, again foamed indicating that the foam maycounteract the mucus. If the attack led to a kill,the struggling crab soon became quiescent, as istypical in other nemertean-prey interactions. Theworm inverted its proboscis, found ingress to thecrabs body and fed. Crabs escaped by autotomizingappendages entwined by the proboscis, by forcefullypulling away and by remaining quiescent, then movingaway when the worm inverted its proboscis and beforeit entered the crab. Immobility, a response to visualpredators, may falsely indicate paralysis to the wormand cause it to invert its proboscis, therebyproviding the crab with an opportunity to escape. This predator-prey interaction seems to incorporategeneralized predator tactics and fortuitous preydefenses that give worms and crabs about an evenchance of success.     

The Conserved G-Protein Coupled Receptor FSHR-1 Regulates Protective Host Responses to Infection and Oxidative Stress

The innate immune system’s ability to sense an infection is critical so that it can rapidly respond if pathogenic microorganisms threaten the host, but otherwise maintain a quiescent baseline state to avoid causing damage to the host or to commensal microorganisms. One important mechanism for discriminating between pathogenic and non-pathogenic bacteria is the recognition of cellular damage caused by a pathogen during the course of infection. In Caenorhabditis elegans, the conserved G-protein coupled receptor FSHR-1 is an important constituent of the innate immune response. FSHR-1 activates the expression of antimicrobial infection response genes in infected worms and delays accumulation of the ingested pathogen Pseudomonas aeruginosa. FSHR-1 is central not only to the worm’s survival of infection by multiple pathogens, but also to the worm’s survival of xenobiotic cadmium and oxidative stresses. Infected worms produce reactive oxygen species to fight off the pathogens; FSHR-1 is required at the site of infection for the expression of detoxifying genes that protect the host from collateral damage caused by this defense response. Finally, the FSHR-1 pathway is important for the ability of worms to discriminate pathogenic from benign bacteria and subsequently initiate an aversive learning program that promotes selective pathogen avoidance.     

The joy of sex pheromones

Sex pheromones provide an important means of communication to unite individuals for successful reproduction. Although sex pheromones are highly diverse across animals, these signals fulfil common fundamental roles in enabling identification of a mating partner of the opposite sex, the appropriate species and of optimal fecundity. In this review, we synthesize both classic and recent investigations on sex pheromones in a range of species, spanning nematode worms, insects and mammals. These studies reveal comparable strategies in how these chemical signals are produced, detected and processed in the brain to regulate sexual behaviours. Elucidation of sex pheromone communication mechanisms both defines outstanding models to understand the molecular and neuronal basis of chemosensory behaviours, and reveals how similar evolutionary selection pressures yield convergent solutions in distinct animal nervous systems.EMBO reports advance online publication 13 September 2013; doi:10.1038/embor.2013.140     

Coordinate control of growth arrest states in normal human diploid fibroblasts: effect of cloned SV40 tumor antigen genes

The growth arrest states of quiescence and senescence in normal human diploid fibroblasts (HDF) are related but distinct phenomena. In an effort to (1) understand the extent to which arrest in the quiescent state and arrest in the senescent state share common regulatory mechanisms, and (2) test our hypothesis that when the quiescent phenotype is altered in HDF, then the senescent phenotype is likewise altered, we have transfected HDF with cloned SV40 tumor antigen genes. Introduction of the tumor antigen genes results in a loss of the ability to enter both the quiescent arrest state and the senescent arrest state but does not immortalize the cells or create significant aneuploidy.     

Habitat selection by helminths: a hypothesis

How do liver worms find the liver? Why are heartworms always found in the heart? Attempts to answer these questions have invariably yielded inconclusive results. A major problem has been the use of models or hypotheses derived from studies of free-living organisms. The parasite's environment is distinct from free-living environments in several fundamental ways and these differences will impact on the evolution of parasite behaviours. In this article, Michael Sukhdeo outlines a hypothesis for habitat selection behavior of helminths that is based on the specific environmental conditions within the host.     

Immunofluorescence localization of the regulatory subunit type II of cAMP-dependent protein kinase in PC12 and 3T3 cells in different proliferative states

Localization of the regulatory subunit of cAMP-dependent protein kinase type II was studied in proliferating and quiescent fibroblasts 3T3 and in a cell line of neural origin pheochromocytoma PC12. In actively proliferating PCl2 cells the regulatory subunit was found to be localized in the nucleus. Transition of these cells into a quiescent state was accompanied by a regulatory subunit translocation to the cytoplasm. In 3T3 cells the regulatory subunit was localized in the cytoplasm both in the quiescent and proliferating (though less actively than PC12 cells) states. Similar results were obtained both with monoclonal antibodies and with rabbit monospecific antiserum raised against the regulatory subunit type II from pig brain.     

Angiostrongylus cantonensis: in vitro cultivation from the first-stage to infective third-stage larvae

The first-stage larvae of Angiostrongylus cantonensis were cultured in various media at 27 degrees C. The most suitable medium for the development was Chernin's balanced salt solution supplemented with 10% L-15, 10% tryptose phosphate broth, 20% fetal calf serum, and 26 mM sodium bicarbonate. Addition of sodium bicarbonate to the medium facilitated early development of the first-stage larvae. When the first-stage larvae were cultured in the medium under 5% CO2 in air, the worms developed gradually to become quiescent and showed the C shape. Thereafter, the larvae developed to the second stage, retaining their first sheath. About 23 days later, the larvae began to develop to the third stage, being enclosed within the sheaths of the first and second molts. Under these conditions, the larvae developed uniformly and 82% of the larvae reached the third stage 50 days later. About 70% of the third-stage larvae discarded their two sheaths, showing almost the same size as those obtained in vivo. When these exsheathed larvae were inoculated into rats, they developed into adult worms and deposited numerous first-stage larvae.     

Quiescent fibroblasts are protected from proteasome inhibition-mediated toxicity

Proteasome inhibition is used as a treatment strategy for multiple types of cancers. Although proteasome inhibition can induce apoptotic cell death in actively proliferating cells, it is less effective in quiescent cells. In this study, we used primary human fibroblasts as a model system to explore the link between the proliferative state of a cell and proteasome inhibition-mediated cell death. We found that proliferating and quiescent fibroblasts have strikingly different responses to MG132, a proteasome inhibitor; proliferating cells rapidly apoptosed, whereas quiescent cells maintained viability. Moreover, MG132 treatment of proliferating fibroblasts led to increased superoxide anion levels, juxtanuclear accumulation of ubiquitin- and p62/SQSTM1-positive protein aggregates, and apoptotic cell death, whereas MG132-treated quiescent cells displayed fewer juxtanuclear protein aggregates, less apoptosis, and higher levels of mitochondrial superoxide dismutase. In both cell states, reducing reactive oxygen species with N-acetylcysteine lessened protein aggregation and decreased apoptosis, suggesting that protein aggregation promotes apoptosis. In contrast, increasing cellular superoxide levels with 2-methoxyestradiol treatment or inhibition of autophagy/lysosomal pathways with bafilomycin A1 sensitized serum-starved quiescent cells to MG132-induced apoptosis. Thus, antioxidant defenses and the autophagy/lysosomal pathway protect serum-starved quiescent fibroblasts from proteasome inhibition-induced cytotoxicity.     

Laboratory constraints on feeding behaviours in polymorphic bluegill sunfish (Lepomis macrochirus)

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Sensory Neurons Arouse C. elegans Locomotion via Both Glutamate and Neuropeptide Release

C. elegans undergoes periods of behavioral quiescence during larval molts (termed lethargus) and as adults. Little is known about the circuit mechanisms that establish these quiescent states. Lethargus and adult locomotion quiescence is dramatically reduced in mutants lacking the neuropeptide receptor NPR-1. Here, we show that the aroused locomotion of npr-1 mutants results from the exaggerated activity in multiple classes of sensory neurons, including nociceptive (ASH), touch sensitive (ALM and PLM), and stretch sensing (DVA) neurons. These sensory neurons accelerate locomotion via both neuropeptide and glutamate release. The relative contribution of these sensory neurons to arousal differs between larval molts and adults. Our results suggest that a broad network of sensory neurons dictates transitions between aroused and quiescent behavioral states.     

Multi-neuronal refractory period adapts centrally generated behaviour to reward

Oscillating neuronal circuits, known as central pattern generators (CPGs), are responsible for generating rhythmic behaviours such as walking, breathing and chewing. The CPG model alone however does not account for the ability of animals to adapt their future behaviour to changes in the sensory environment that signal reward. Here, using multi-electrode array (MEA) recording in an established experimental model of centrally generated rhythmic behaviour we show that the feeding CPG of Lymnaea stagnalis is itself associated with another, and hitherto unidentified, oscillating neuronal population. This extra-CPG oscillator is characterised by high population-wide activity alternating with population-wide quiescence. During the quiescent periods the CPG is refractory to activation by food-associated stimuli. Furthermore, the duration of the refractory period predicts the timing of the next activation of the CPG, which may be minutes into the future. Rewarding food stimuli and dopamine accelerate the frequency of the extra-CPG oscillator and reduce the duration of its quiescent periods. These findings indicate that dopamine adapts future feeding behaviour to the availability of food by significantly reducing the refractory period of the brain's feeding circuitry.     

Changes in Postural Syntax Characterize Sensory Modulation and Natural Variation of C. elegans Locomotion

Locomotion is driven by shape changes coordinated by the nervous system through time; thus, enumerating an animal''s complete repertoire of shape transitions would provide a basis for a comprehensive understanding of locomotor behaviour. Here we introduce a discrete representation of behaviour in the nematode C. elegans. At each point in time, the worm’s posture is approximated by its closest matching template from a set of 90 postures and locomotion is represented as sequences of postures. The frequency distribution of postural sequences is heavy-tailed with a core of frequent behaviours and a much larger set of rarely used behaviours. Responses to optogenetic and environmental stimuli can be quantified as changes in postural syntax: worms show different preferences for different sequences of postures drawn from the same set of templates. A discrete representation of behaviour will enable the use of methods developed for other kinds of discrete data in bioinformatics and language processing to be harnessed for the study of behaviour.