443 research outputs found
Bioactivity and structural properties of chimeric analogs of the starfish SALMFamide neuropeptides S1 and S2
Get PDFThe starfish SALMFamide neuropeptides S1 (GFNSALMFamide) and S2 (SGPYSFNSGLTFamide) are the prototypical members of a family of neuropeptides that act as muscle relaxants in echinoderms. Comparison of the bioactivity of S1 and S2 as muscle relaxants has revealed that S2 is ten times more potent than S1. Here we investigated a structural basis for this difference in potency by comparing the bioactivity and solution conformations (using NMR and CD spectroscopy) of S1 and S2 with three chimeric analogs of these peptides. A peptide comprising S1 with the addition of S2's N-terminal tetrapeptide (Long S1 or LS1; SGPYGFNSALMFamide) was not significantly different to S1 in its bioactivity and did not exhibit concentration-dependent structuring seen with S2. An analog of S1with its penultimate residue substituted from S2 (S1(T); GFNSALTFamide) exhibited S1-like bioactivity and structure. However, an analog of S2 with its penultimate residue substituted from S1 (S2(M); SGPYSFNSGLMFamide) exhibited loss of S2-type bioactivity and structural properties. Collectively, our data indicate that the C-terminal regions of S1 and S2 are the key determinants of their differing bioactivity. However, the N-terminal region of S2 may influence its bioactivity by conferring structural stability in solution. Thus, analysis of chimeric SALMFamides has revealed
how neuropeptide bioactivity is determined by a complex interplay of sequence and conformation
Structural analysis of the starfish SALMFamide neuropeptides S1 and S2: The N-terminal region of S2 facilitates self-association
Get PDFThe neuropeptides S1 (GFNSALMFamide) and S2 (SGPYSFNSGLTFamide), which share sequence similarity, were discovered in the starfish Asterias rubens and are prototypical members of the SALMFamide family of neuropeptides in echinoderms. SALMFamide neuropeptides act as muscle relaxants and both S1 and S2 cause relaxation of cardiac stomach and tube foot preparations in vitro but S2 is an order of magnitude more potent than S1. Here we investigated a structural basis for this difference in potency using spectroscopic techniques. Circular dichroism spectroscopy showed that S1 does not have a defined structure in aqueous solution and this was supported by 2D nuclear magnetic resonance experiments. In contrast, we found that S2 has a well-defined conformation in aqueous solution. However, the conformation of S2 was concentration dependent, with increasing concentration inducing a transition from an unstructured to a structured conformation. Interestingly, this property of S2 was not observed in an N-terminally truncated analogue of S2 (short S2 or SS2; SFNSGLTFamide). Collectively, the data obtained indicate that the N-terminal region of S2 facilitates peptide self-association at high concentrations, which may have relevance to the biosynthesis and/or bioactivity of S2 in vivo
Multi-Phase Patterns in Periodically Forced Oscillatory Systems
Full text linkPeriodic forcing of an oscillatory system produces frequency locking bands
within which the system frequency is rationally related to the forcing
frequency. We study extended oscillatory systems that respond to uniform
periodic forcing at one quarter of the forcing frequency (the 4:1 resonance).
These systems possess four coexisting stable states, corresponding to uniform
oscillations with successive phase shifts of . Using an amplitude
equation approach near a Hopf bifurcation to uniform oscillations, we study
front solutions connecting different phase states. These solutions divide into
two groups: -fronts separating states with a phase shift of and
-fronts separating states with a phase shift of . We find a new
type of front instability where a stationary -front ``decomposes'' into a
pair of traveling -fronts as the forcing strength is decreased. The
instability is degenerate for an amplitude equation with cubic nonlinearities.
At the instability point a continuous family of pair solutions exists,
consisting of -fronts separated by distances ranging from zero to
infinity. Quintic nonlinearities lift the degeneracy at the instability point
but do not change the basic nature of the instability. We conjecture the
existence of similar instabilities in higher 2n:1 resonances (n=3,4,..) where
stationary -fronts decompose into n traveling -fronts. The
instabilities designate transitions from stationary two-phase patterns to
traveling 2n-phase patterns. As an example, we demonstrate with a numerical
solution the collapse of a four-phase spiral wave into a stationary two-phase
pattern as the forcing strength within the 4:1 resonance is increased
A Phase Front Instability in Periodically Forced Oscillatory Systems
Full text linkMultiplicity of phase states within frequency locked bands in periodically
forced oscillatory systems may give rise to front structures separating states
with different phases. A new front instability is found within bands where
(). Stationary fronts shifting the
oscillation phase by lose stability below a critical forcing strength and
decompose into traveling fronts each shifting the phase by . The
instability designates a transition from stationary two-phase patterns to
traveling -phase patterns
Tracking human face features in thermal images for respiration monitoring
Get PDFA method has been developed to track a region related to respiration process in thermal images. The respiration region of interest (ROI) consisted of the skin area around the tip of the nose. The method was then used as part of a non-contact respiration rate monitoring that determined the skin temperature changes caused by respiration. The ROI was located by the first determining the relevant salient features of the human face physiology. These features were the warmest and coldest facial points. The tracking method was tested on thermal video images containing no head movements, small random and regular head movements. The method proved valuable for tracking the ROI in all these head movement types. It was also possible to use this tracking method to monitor respiration rate involving a number of head movement types. Currently, more investigations are underway to improve the tracking method so that it can track the ROI in cases larger head movements
Discovery of a neuropeptide that acts as an autotomy-promoting factor
Get PDFOne of the most remarkable adaptations to survive attacks from predators is to detach an appendageâa process known as autotomy. This occurs in a variety of animals, including lizards (tail), crabs (legs), and starfish (arms). There has been extensive investigation of the evolution, ecology, and biomechanical impact of autotomy,1,2,3 but little is known about neural mechanisms controlling autotomy in animals. However, evidence for the existence of a peptide that acts as an autotomy-promoting factor in starfish has been reported.4 While investigating in vivo effects of a sulfakinin/cholecystokinin-type neuropeptide (ArSK/CCK1) in the starfish Asterias rubens,5,6 we observed that this peptide triggered arm autotomy in some animals. Furthermore, when injection of ArSK/CCK1 was combined with mechanical clamping of an arm, autotomy of the clamped arm occurred in 85% of animals tested, with 46% also autotomizing one or more other arms. In contrast, no autotomy was observed in clamped animals that were injected with water (control). To examine the physiological relevance of these findings, we analyzed expression of ArSK/CCK1 in the autotomy plane, a specialized region at the base of the arms in A. rubens.7,8 In accordance with its in vivo effects, nerve fibers expressing ArSK/CCK1 were revealed in the tourniquet muscle, a band of muscle that mediates constriction of the arm during and after autotomy. We conclude that ArSK/CCK1 acts as an autotomy-promoting factor in starfish and as such it is the first neuropeptide to be identified as a regulator of autotomy in animals
Frozen spatial chaos induced by boundaries
Get PDFWe show that rather simple but non-trivial boundary conditions could induce
the appearance of spatial chaos (that is stationary, stable, but spatially
disordered configurations) in extended dynamical systems with very simple
dynamics. We exemplify the phenomenon with a nonlinear reaction-diffusion
equation in a two-dimensional undulated domain. Concepts from the theory of
dynamical systems, and a transverse-single-mode approximation are used to
describe the spatially chaotic structures.Comment: 9 pages, 6 figures, submitted for publication; for related work visit
http://www.imedea.uib.es/~victo
Mapping the autistic advantage from the accounts of adults diagnosed with autism: A qualitative study
Get PDFThis is the final version. Available on open access from Mary Ann Liebert via the DOI in this recordBackground: Autism has been associated with specific cognitive strengths. Strengths and weaknesses have traditionally been conceptualized as dichotomous.
Methods: We conducted 28 semi-structured interviews with autistic adults. Maximum variation sampling was used to ensure diversity in relation to support needs. We asked which personal traits adults attributed to their autism, and how these have helped in the workplace, in relationships, and beyond. Data were collected in two stages. Responses were analyzed using content and thematic techniques.
Results: The ability to hyperfocus, attention to detail, good memory, and creativity were the most frequently described traits. Participants also described specific qualities relating to social interaction, such as honesty, loyalty, and empathy for animals or for other autistic people. In thematic analysis we found that traits associated with autism could be experienced either as advantageous or disadvantageous dependent on moderating influences. Moderating influences included the social context in which behaviors occurred, the ability to control behaviors, and the extent to which traits were expressed.
Conclusions: Separating autistic strengths from weaknesses may be a false dichotomy if traits cannot be isolated as separate constructs of strengths or deficits. If attempts to isolate problematic traits from advantageous traits are ill conceived, there may be implications for interventions that have reduction in autistic traits as a primary outcome measure.Wellcome Trus
People should be allowed to do what they likeâ: Autistic adultsâ views and experiences of stimming
Get PDFThis is the final version. Available from the publisher via the DOI in this record.Data from participants who consented will be deposited in the
UK Data Service, in 2019.âStereotyped or repetitive motor movementsâ are characterised as core features in the diagnosis of autism, yet many
autistic adults (and the neurodiversity movement) have reclaimed them as âstimmingâ. Supported by a growing body of
scientific research, autistic adults argue that these behaviours may serve as useful coping mechanisms, yet little research
has examined stimming from the perspective of autistic adults. Through interviews and focus groups, we asked 32
autistic adults to share their perceptions and experiences of stimming, including the reasons they stim, any value doing
so may hold for them and their perceptions of othersâ reactions to stimming. Using thematic analysis, we identified
two themes: stimming as (1) a self-regulatory mechanism and (2) lacking in social acceptance, but can become accepted
through understanding. Autistic adults highlighted the importance of stimming as an adaptive mechanism that helps
them to soothe or communicate intense emotions or thoughts and thus objected to treatment that aims to eliminate
the behaviour.Wellcome TrustLeverhulme Trus
Order Parameter Equations for Front Transitions: Planar and Circular Fronts
Full text linkNear a parity breaking front bifurcation, small perturbations may reverse the
propagation direction of fronts. Often this results in nonsteady asymptotic
motion such as breathing and domain breakup. Exploiting the time scale
differences of an activator-inhibitor model and the proximity to the front
bifurcation, we derive equations of motion for planar and circular fronts. The
equations involve a translational degree of freedom and an order parameter
describing transitions between left and right propagating fronts.
Perturbations, such as a space dependent advective field or uniform curvature
(axisymmetric spots), couple these two degrees of freedom. In both cases this
leads to a transition from stationary to oscillating fronts as the parity
breaking bifurcation is approached. For axisymmetric spots, two additional
dynamic behaviors are found: rebound and collapse.Comment: 9 pages. Aric Hagberg: http://t7.lanl.gov/People/Aric/; Ehud Meron:
http://www.bgu.ac.il/BIDR/research/staff/meron.htm
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