53 research outputs found
Expanding dispersal studies at hydrothermal vents through species identification of cryptic larval forms
Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Marine Biology 157 (2010): 1049-1062, doi:10.1007/s00227-009-1386-8.The rapid identification of hydrothermal vent-endemic larvae to the species level is a key
limitation to understanding the dynamic processes that control the abundance and
distribution of fauna in such a patchy and ephemeral environment. Many larval forms
collected near vents, even those in groups such as gastropods that often form a
morphologically distinct larval shell, have not been identified to species. We present a
staged approach that combines morphological and molecular identification to optimize
the capability, efficiency, and economy of identifying vent gastropod larvae from the
northern East Pacific Rise (NEPR). With this approach, 15 new larval forms can be
identified to species. A total of 33 of the 41 gastropod species inhabiting the NEPR, and
26 of the 27 gastropod species known to occur specifically in the 9° 50’ N region, can be
identified to species. Morphological identification efforts are improved by new
protoconch descriptions for Gorgoleptis spiralis, Lepetodrilus pustulosus, Nodopelta
subnoda, and Echinopelta fistulosa. Even with these new morphological descriptions, the
majority of lepetodrilids and peltospirids require molecular identification. Restriction
fragment length polymorphism digests are presented as an economical method for
identification of five species of Lepetodrilus and six species of peltospirids. The
remaining unidentifiable specimens can be assigned to species by comparison to an
expanded database of 18S ribosomal DNA. The broad utility of the staged approach was
exemplified by the revelation of species-level variation in daily planktonic samples and
the identification and characterization of egg capsules belonging to a conid gastropod
Gymnobela sp. A. The improved molecular and morphological capabilities nearly double
the number of species amenable to field studies of dispersal and population connectivity.Funding was provided by as Woods Hole Oceanographic Institution Deep Ocean
Exploration Institute grant to L.M and S. Beaulieu, National Science Foundation grants
OCE-0424953, OCE-9712233, and OCE-9619605 to L.M, OCE-0327261 to T.S., and
OCE-0002458 to K. Von Damm, and a National Defense Science and Engineering
Graduate fellowship to D.A
Expression of excess receptors and negative feedback control of signal pathways are required for rapid activation and prompt cessation of signal transduction
Cellular signal transduction is initiated by the binding of extracellular ligands to membrane receptors. Receptors are often expressed in excess, and cells are activated when a small number of receptors bind ligands. Intracellular signal proteins are act
The effects of upper and lower limb exercise on the microvascular reactivity in limited cutaneous systemic sclerosis patients
Background: Aerobic exercise in general and high intensity interval training (HIIT) specifically is known to improve vascular function in a range of clinical conditions. HIIT in particular has demonstrated improvements in clinical outcomes, in conditions that have a strong macroangiopathic component. Nevertheless, the effect of HIIT on microcirculation in systemic sclerosis (SSc) patients is yet to be investigated. Therefore, the purpose of the study was to compare the effects of two HIIT protocols (cycle and arm cranking) on the microcirculation of the digital area in SSc patients.
Methods: Thirty four limited cutaneous SSc patients (65.3 ± 11.6 years old) were randomly allocated in three groups (cycling, arm cranking and control group). The exercise groups underwent a twelve-week exercise program twice per week. All patients performed the baseline and post-exercise intervention measurements where physical fitness, functional ability, transcutaneous oxygen tension (ΔtcpO2), body composition and quality of life were assessed. Endothelial-dependent as well as-independent vasodilation were assessed in the middle and index fingers using LDF and incremental doses of acetylcholine (ACh) and sodium nitroprusside (SNP). Cutaneous flux data were expressed as cutaneous vascular conductance (CVC).
Results: Peak oxygen uptake increased in both exercise groups (p<0.01, d=1.36). ΔtcpO2 demonstrated an increase in the arm cranking group only, with a large effect, but not found statistically significant,(p=0.59, d=0.93). Endothelial-dependent vasodilation improvement was greater in the arm cranking (p<0.05, d=1.07) in comparison to other groups. Both exercise groups improved life satisfaction (p<0.001) as well as reduced discomfort and pain due to Raynaud's phenomenon (p<0.05). Arm cranking seems to be the preferred mode of exercise for study participants as compared to cycling (p<0.05). No changes were observed in the body composition or the functional ability in both exercise groups.
Conclusion: Our results suggest that arm cranking has the potential to improve the microvascular endothelial function in SSc patients. Also notably, our recommended training dose (e.g., a 12-week HIIT program, twice per week), appeared to be sufficient and tolerable for this population. Future research should focus on exploring the feasibility of a combined exercise such as aerobic and resistance training by assessing individual's experience and the quality of life in SSc patients.
Trial registration: ClinicalTrials.gov (NCT number): NCT03058887, February 23, 2017, https://clinicaltrials.gov/ct2/show/NCT03058887?term=NCT03058887&rank=1
Key words: High intensity interval training, vascular function, quality of lif
Keeping an eye on noisy movements: On different approaches to perceptual-motor skill research and training
Contemporary theorising on the complementary nature of perception and action in expert performance has led to the emergence of different emphases in studying movement coordination and gaze behaviour. On the one hand, coordination research has examined the role that variability plays in movement control, evidencing that variability facilitates individualised adaptations during both learning and performance. On the other hand, and at odds with this principle, the majority of gaze behaviour studies have tended to average data over participants and trials, proposing the importance of universal 'optimal' gaze patterns in a given task, for all performers, irrespective of stage of learning. In this article, new lines of inquiry are considered with the aim of reconciling these two distinct approaches. The role that inter- and intra-individual variability may play in gaze behaviours is considered, before suggesting directions for future research
Panmixia in a fragmented and unstable environment: the hydrothermal shrimp Rimicaris exoculata disperses extensively along the Mid-Atlantic ridge
Dispersal plays a fundamental role in the evolution and persistence of species, and especially for species inhabiting extreme,
ephemeral and highly fragmented habitats as hydrothermal vents. The Mid-Atlantic Ridge endemic shrimp species Rimicaris exoculata was studied using microsatellite markers to infer connectivity along the 7100-Km range encompassing the sampled sites. Astonishingly, no genetic differentiation was found between individuals from the different geographic origins, supporting a scenario of widespread large-scale dispersal despite the habitat distance and fragmentation. We hypothesize that delayed metamorphosis associated to temperature differences or even active directed migration
dependent on physical and/or chemical stimuli could explain these results and warrant further studies on adaptation and
dispersal mechanisms
Normalization of ground reaction forces
The appropriateness of normalizing data, as one method to reduce the effects of a covariate on a dependent variable, should be evaluated. Using ratio, 0.67-nonlinear, and fitted normalizations, the aim of this study was to investigate the relationship between ground reaction force variables and body mass (BM). Ground reaction forces were recorded for 40 female subjects running at 3.7 ± 0.18 m·s–1 (mass = 58 ± 6 kg). The explained variance for mass to forces (peak-impact-vertical = 70%; propulsive-vertical = 27%; braking = 40%) was reduced to < 0.1% for mass to ratio normalized forces (i.e., forces/BM1) with statistically significantly different power exponents (p < 0.05). The smaller covariate effect of mass on loading rate variables of 2–16% was better removed through fitted normalization (e.g., vertical-instantaneous-loading-rate/BM0.69±0.93; ±95% CI) with nonlinear power exponents ranging from 0.51 to 1.13. Generally, these were similar to 0.67 as predicted through dimensionality theory, but, owing to the large confidence intervals, these power exponents were not statistically significantly different from absolute or ratio normalized data (p > 0.05). Further work is warranted to identify the appropriate method to normalize loading rates either to mass or to another covariate. Ratio normalization of forces to mass, as predicted through Newtonian mechanics, is recommended for comparing subjects of different masses.</jats:p
Head-torso coordination in police officers wearing loaded tactical vests during running
This is the final version. Available on open access from Elsevier via the DOI in this recordBackground
The influence of load carriage in operational police officers is not well understood despite a relatively high injury rate. Assessing load related changes in head and torso coordination may provide valuable insight into plausible injury mechanisms.
Research question
Do typical police tactical vest loads alter head and torso coordination during running?
Methods
Thirty-eight UK police officers ran at a self-selected pace (>2 ms−1) on a non-motorised treadmill in four vest load conditions (unloaded, and low, high and evenly distributed loads). Peak head and torso tilt, and peak vest displacement were compared between all four conditions. Timings between vest and torso change of direction were compared between the three loaded conditions. The coupling angle between the head and torso calculated using modified vector coding were compared between unloaded and each loaded conditions using Statistical Parametric Mapping.
Results
No significant differences were found between conditions for peak head or torso tilt alone (p > 0.05). Loading equipment low on the vest led to significantly greater mediolateral vest displacements (38 mm) away from the torso than a high (34 mm) or evenly distributed (30 mm) conditions. The vest was found to change direction vertically before the torso in the anterior-posterior direction, and then influence torso motion. The loaded conditions changed the head-torso coupling from in-phase (with head-dominancy) to anti-phase (with torso dominancy) between 55% and 77% stance. Anti-phase with a relatively stationary head and the torso rotating forward likely places a greater concentric demand on the posterior neck muscles relative to unloaded running.
Significance
Current tactical vest designs allow significant extra displacement of load away from the body during running, altering coordination at the head and torso.Innovate UKArktis Endurance Textiles Ltd
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