Heart rate and rhythm patterns in the fetus, neonate and child

Imperial Users onl

The role of interference and trace decay in the retention of a simple psychomotor task

The purpose of the present study was to try to distinguish between the interference theory and trace decay theory and to try to establish whether one or a combination of the two best accounts for the forgetting shown in motor short-term memory (STM). The experiment was a seven by three factorial design with repeated measures on the second factor. The first factor was number of prior responses which the S experienced on the linear slide apparatus, and the number of responses ranged from zero through six. The second factor, length of the retention interval between practice and recall, had values of 5 sec., 40 sec., and 75 sec. Neither main effect of retention interval nor number of prior responses were significant. The interaction of retention interval and number of prior responses was also nonsignificant. No definite conclusions could be drawn from the present study, but other studies were considered and Pepper and Herman\u27s recent two-process theory of motor STM was discussed

Calcium signalling and calcium pools in a Drosophila epithelium

The Drosophila Malpighian tubule is an ideal model epithelium for the study of fluidtransport and cell signalling. The tubule is the primary osmoregulatory tissue in the fly and Ca2+ signalling plays a critical role in controlling the fluid secretion rate of this organ. This project describes the use of powerful transgenic and fluorescent reporter techniques to further understand the mechanics of Ca2+ signalling in the cells of this tissue. In particular,the contribution of internal Ca2+ stores to the diuretic peptide-induced Ca signals has been investigated. In an attempt to unravel the role of the ER in these signals, an approach involving the Ca2+ sensitive photoprotein aequorin was undertaken. Transgenic flies were generated that could express ER-targeted aequorin; this in theory would have allowed real-time measurements of [Ca2+] ER in tubules during agonist stimulation. Unfortunately this method is presently not achievable in Drosophila, due to problems with targeting signals and the retention properties of the insect ER. As an alternative strategy a fluorescent Ca2+ reporter was developed that is targeted and functional in the ER. Transgenic flies were generated that could express this new reporter, ERpicam, in a cell specific manner. This has allowed realtime monitoring of [Ca2+]ER levels in a live intact tissue during stimulation with neuropeptides. The results were surprising, as they imply that the ER plays no role in the generation of LP3-induced Ca2+ signals in some cells of the tubule. The impact of these Ca2+ signals on mitochondrial Ca2+ levels was also investigated using targeted aequorin and new improved targeted fluorescent reporters. Mitochondria in the tubule do take up Ca2+ during the signalling events, however, the dynamics of this uptake are in contrast with the majority of data collected in other cell systems. Both the aequorin and fluorescent reporter techniques revealed that [Ca2+]mt levels in both cell types of the tubule do not increase in conjunction with the primary IP3-induced component of the signal but instead with the slower secondary response. This project also describes the identification and characterisation of the Drosophila secretory pathway Ca2+/Mn2+ ATPase (SPCA). The discovery that this multiply-sphced ATPase is targeted to multiple organelles will have important implications for further understanding of Ca2+ and Mn2+ transport in all cellular systems. Furthermore, it has uncovered roles for this protein in tubule function and has proved to be a powerful tool for dissecting the Ca2+ signals in this tissue through overexpression studies. Most interestingly, overexpression of a Golgi-localised SPCA results in a potentiation of EP3-mduced Ca increases in cells of the tubule, implying that this organelle plays a significant role in generating these responses. During the initial investigation of the Drosophila SPCA, development of a new gene knock-in method for Drosophila was theorised in an attempt to elucidate the expression and function of the SPCA. This technology is based on spliceosome-mediated trans-splicing. It can allow specific targeting of pre-mRNAs in transgenic Drosophila and enable reprogramming of the mature mRNA. The system has been adapted and successfully demonstrated in transgenic flies, however further work and refinement is needed before it can be used as a generic tool. These approaches have made significant advances into understanding the unusual Ca2+ signalling events of this epithelium and this work can be continued to gain further insight into how renal function is controlled in Drosophila and higher organisms

Strengthening the emergency healthcare system for mothers and children in The Gambia

A system to improve the management of emergencies during pregnancy, childbirth, infancy and childhood in a region of The Gambia (Brikama) with a population of approximately 250,000 has been developed

Marine seismic surveys and ocean noise : time for coordinated and prudent planning

Marine seismic surveys use intense (eg >= 230 decibel [dB] root mean square [RMS]) sound impulses to explore the ocean bottom for hydrocarbon deposits, conduct geophysical research, and establish resource claims under the United Nations Convention on the Law of the Sea. The expansion of seismic surveys necessitates greater regional and international dialogue, partnerships, and planning to manage potential environmental risks. Data indicate several reasons for concern about the negative impacts of anthropogenic noise on numerous marine species, including habitat displacement, disruption of biologically important behaviors, masking of communication signals, chronic stress, and potential auditory damage. The sound impulses from seismic surveys - spanning temporal and spatial scales broader than those typically considered in environmental assessments - may have acute, cumulative, and chronic effects on marine organisms. Given the international and transboundary nature of noise from marine seismic surveys, we suggest the creation of an international regulatory instrument, potentially an annex to the existing International Convention on the Prevention of Pollution from Ships, to address the issue.Publisher PDFPeer reviewe

Context-dependent lateralized feeding strategies in blue whales.

Lateralized behaviors benefit individuals by increasing task efficiency in foraging and anti-predator behaviors [1-4]. The conventional lateralization paradigm suggests individuals are left or right lateralized, although the direction of this laterality can vary for different tasks (e.g. foraging or predator inspection/avoidance). By fitting tri-axial movement sensors to blue whales (Balaenoptera musculus), and by recording the direction and size of their rolls during lunge feeding events, we show how these animals differ from such a paradigm. The strength and direction of individuals' lateralization were related to where and how the whales were feeding in the water column. Smaller rolls (≤180°) predominantly occurred at depth (>70 m), with whales being more likely to rotate clockwise around their longest axis (right lateralized). Larger rolls (>180°), conversely, occurred more often at shallower depths (<70 m) and were more likely to be performed anti-clockwise (left lateralized). More acrobatic rolls are typically used to target small, less dense krill patches near the water's surface [5,6], and we posit that the specialization of lateralized feeding strategies may enhance foraging efficiency in environments with heterogeneous prey distributions

Basking sharks and oceanographic fronts: quantifying associations in the north-east Atlantic

Understanding the mechanisms linking oceanographic processes and marine vertebrate habitat use is critical to effective management of populations of conservation concern. The basking shark Cetorhinus maximus has been shown to associate with oceanographic fronts – physical interfaces at the transitions between water masses – to exploit foraging opportunities resulting from aggregation of zooplankton. However, the scale, significance and variability of these observed associations have not yet been established. Here, we quantify the influence of mesoscale (10s – 100s km) frontal activity on habitat use over timescales of weeks to months. We use animal-mounted archival tracking with composite front mapping via Earth Observation (EO) remote sensing to provide an oceanographic context to individual shark movements. We investigate levels of association with fronts occurring over two spatio-temporal scales, (i) broad-scale seasonally persistent frontal zones and (ii) contemporaneous mesoscale thermal and chl-a fronts. Using random walk simulations and logistic regression within an iterative generalised linear mixed modelling (GLMM) framework, we find that seasonal front frequency is a significant predictor of shark presence. Temporally-matched oceanographic metrics also indicate that sharks demonstrate a preference for productive regions, and associate with contemporaneous thermal and chl-a fronts more frequently than could be expected at random. Moreover, we highlight the importance of cross-frontal temperature change and persistence, which appear to interact to affect the degree of prey aggregation along thermal fronts. These insights have clear implications for understanding the preferred habitats of basking sharks in the context of anthropogenic threat management and marine spatial planning in the northeast Atlantic

Marine mammals and sonar : dose-response studies, the risk-disturbance hypothesis and the role of exposure context

This manuscript was written following the Behavioral Response Research Evaluation Workshop (BRREW), jointly sponsored by the US Office of Naval Research, US Navy Living Marine Resources, and US National Oceanic and Atmospheric Administration - National Marine Fisheries Service. PLT acknowledges funding from the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland). MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions.1. Marine mammals may be negatively affected by anthropogenic noise. Behavioural response studies (BRSs) aim to establish a relationship between the exposure dose of a stressor and associated behavioural responses of animals. A recent series of BRSs have focused on the effects of naval sonar on cetaceans. Here we review the current state of understanding of the impact of sonar on marine mammals and highlight knowledge gaps and future research priorities. 2. Many marine mammal species exhibit responses to naval sonar. However, responses are highly variable between and within individuals, species and populations, highlighting the importance of context in modulating dose-response relationships. 3. There is increasing support for the risk-disturbance hypothesis as an underlying response mechanism. This hypothesis proposes that sonar sounds may be perceived by animals as a threat, evoking an evolved anti-predator response. An understanding of responses within both the dose-response and risk-disturbance frameworks may enhance our ability to predict responsiveness for unstudied species and populations. 4. Many observed behavioural responses are energetically costly, but the way in which these responses may lead to long-term individual and population level impacts is poorly understood. Synthesis and Applications Behavioural response studies have greatly enhanced our understanding of the potential effects of navy sonar on marine mammals. Despite data gaps, we believe a dose-response approach within a risk-disturbance framework will enhance our ability to predict responsiveness for unstudied species and populations. We advocate for (1) regulatory frameworks to utilise recent peer-reviewed research findings when making predictions of impact (where feasible within assessment cycles), (2) regulatory frameworks to account for the inherent uncertainty in predictions of impact, and (3) investment in monitoring programmes that are both directed by recent research and offer opportunities for validation of predictions at the individual and population level.Publisher PDFPeer reviewe

First direct measurements of behavioural responses by Cuvier's beaked whales to mid-frequency active sonar

Most marine mammal­ strandings coincident with naval sonar exercises have involved Cuvier's beaked whales (Ziphius cavirostris). We recorded animal movement and acoustic data on two tagged Ziphius and obtained the first direct measurements of behavioural responses of this species to mid-frequency active (MFA) sonar signals. Each recording included a 30-min playback (one 1.6-s simulated MFA sonar signal repeated every 25 s); one whale was also incidentally exposed to MFA sonar from distant naval exercises. Whales responded strongly to playbacks at low received levels (RLs; 89–127 dB re 1 µPa): after ceasing normal fluking and echolocation, they swam rapidly, silently away, extending both dive duration and subsequent non-foraging interval. Distant sonar exercises (78–106 dB re 1 µPa) did not elicit such responses, suggesting that context may moderate reactions. The observed responses to playback occurred at RLs well below current regulatory thresholds; equivalent responses to operational sonars could elevate stranding risk and reduce foraging efficiency.Publisher PDFPeer reviewe