Abstract
Wind-driven snow redistribution can increase the spatial heterogeneity of snow accumulation on ice caps and ice sheets, and may prove crucial for the initiation and survival of glaciers in ...areas of marginal glaciation. We present a snowdrift model (Snow_Blow), which extends and improves the model of Purves, Mackaness and Sugden (1999,
Journal of Quaternary Science
14, 313–321). The model calculates spatial variations in relative snow accumulation that result from variations in topography, using a digital elevation model (DEM) and wind direction as inputs. Improvements include snow redistribution using a flux routing algorithm, DEM resolution independence and the addition of a slope curvature component. This paper tests Snow_Blow in Antarctica (a modern environment) and reveals its potential for application in palaeoenvironmental settings, where input meteorological data are unavailable and difficult to estimate. Specifically, Snow_Blow is applied to the Ellsworth Mountains in West Antarctica where ablation is considered to be predominantly related to wind erosion processes. We find that Snow_Blow is able to replicate well the existing distribution of accumulating snow and snow erosion as recorded in and around Blue Ice Areas. Lastly, a variety of model parameters are tested, including depositional distance and erosion vs wind speed, to provide the most likely input parameters for palaeoenvironmental reconstructions.
Surface exposure ages of glacial deposits in the Ford Ranges of western Marie Byrd Land indicate continuous thinning of the West Antarctic Ice Sheet by more than 700 meters near the coast throughout ...the past 10,000 years. Deglaciation lagged the disappearance of ice sheets in the Northern Hemisphere by thousands of years and may still be under way. These results provide further evidence that parts of the West Antarctic Ice Sheet are on a long-term trajectory of decline. West Antarctic melting contributed water to the oceans in the late Holocene and may continue to do so in the future.
Intrinsically photosensitive retinal ganglion cells (ipRGCs) and their nuclear targets in the subcortical visual shell (SVS) are components of the non-image-forming visual system, which regulates ...important physiological processes, including photoentrainment of the circadian rhythm. While ipRGCs have been the subject of much recent research, less is known about their central targets and how they develop to support specific behavioral functions. We describe Sox14 as a marker to follow the ontogeny of the SVS and find that the complex forms from two narrow stripes of Dlx2-negative GABAergic progenitors in the early diencephalon through sequential waves of tangential migration. We characterize the requirement for Sox14 to orchestrate the correct distribution of neurons among the different nuclei of the network and describe how Sox14 expression is required both to ensure robustness in circadian entrainment and for masking of motor activity.
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► Diencephalic Dlx2−, Helt+, Tal1+, Sox14+ neurons are GABAergic progenitors of the SVS ► Tangential migration mediates SVS network formation ► Sox14 loss of function results in anatomical defects in the SVS ► The SVS is an important modulator of circadian behaviors
Delogu et al. show that GABAergic nuclei involved in luminance detection arise from two transverse stripes of Sox14-positive cells that migrate tangentially to settle in diverse locations. Loss of Sox14 function has a dramatic affect on an animal's responses to light.
► Praxis in school vs. clinical DCD samples compared to age matched controls. ► Dyspraxia can be one component of DCD and not a diagnostic term. ► DCD samples showed similarly impaired praxic ...ability. ► Differences in intransitive imitation were found between the DCD samples.
Dyspraxia, a difficulty in executing an operationalised act, has been associated with Developmental Coordination Disorder (DCD). However, issues relating to the area such as comparisons across modalities, comparisons of school vs. clinical populations, and developmental delay vs. pathology have not been addressed in the same, comprehensive study. In the current study, therefore, familiar gesture production in DCD was addressed in a comprehensive manner to follow-up outstanding issues from previous studies: The production of familiar gestures and praxis imagery in a school (
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26) vs. clinic sample (
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19) of children with DCD was examined in relation to typically developing age matched (
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24) all aged from 9 to 11 years, and two groups of younger children within the age ranges of 5–6 (
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23) and 4–5 (
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26) years. Overall, children with Developmental Coordination Disorder showed an impaired ability to produce familiar gestures compared to their typical peers, and this was dependant on the type of gesture and presentation modality. Differences were found between school and clinic samples of children with DCD, suggestive of the recruitment of different underlying mechanisms in the two samples. The results have a bearing on our understanding of the relationship of developmental dyspraxia to DCD, as well as of the issue of developmental delay vs. pathology.
: Melatonin is known to inhibit insulin secretion from rodent β‐cells through interactions with cell‐surface MT1 and/or MT2 receptors, but the function of this hormone in human islets of Langerhans ...is not known. In the current study, melatonin receptor expression by human islets was examined by reverse transcription‐polymerase chain reaction (RT‐PCR) and the effects of exogenous melatonin on intracellular calcium (Ca2+i) levels and islet hormone secretion were determined by single cell microfluorimetry and radioimmunoassay, respectively. RT‐PCR amplifications indicated that human islets express mRNAs coding for MT1 and MT2 melatonin receptors, although MT2 mRNA expression was very low. Analysis of MT1 receptor mRNA expression at the single cell level indicated that it was expressed by human islet α‐cells, but not by β‐cells. Exogenous melatonin stimulated increases in intracellular calcium (Ca2+i) in dissociated human islet cells, and stimulated glucagon secretion from perifused human islets. It also stimulated insulin secretion and this was most probably a consequence of glucagon acting in a paracrine fashion to stimulate β‐cells as the MT1 receptor was absent in β‐cells. Melatonin did not decrease 3′, 5′‐cyclic adenosine monophosphate (cyclic AMP) levels in human islets, but it inhibited cyclic AMP in the mouse insulinoma (MIN6) β‐cell line and it also inhibited glucose‐stimulated insulin secretion from MIN6 cells. These data suggest that melatonin has direct stimulatory effects at human islet α‐cells and that it stimulates insulin secretion as a consequence of elevated glucagon release. This study also indicates that the effects of melatonin are species‐specific with primarily an inhibitory role in rodent β‐cells and a stimulatory effect in human islets.
Transient potential vanilloid 1 (TRPV1) receptor is an ion channel receptor primarily localized on sensory nerves and activated by specific stimuli to initiate and amplify pain and inflammation, as ...typified by murine models of scald and arthritis. Little is known of the role of TRPV1 in sepsis, an infective disease associated with inflammation. Through use of a sublethal murine model of lipopolysaccharide-induced peritoneal sepsis, we provide novel evidence that genetic deletion of TRPV1 leads to an enhanced onset of various pathological components of systemic endotoxemia. Paired studies of TRPV1 knockout (KO) and wild-type mice demonstrate significantly enhanced hypotension (56±2% vs. 38±6% decrease in blood pressure, n=12), hypothermia (13±3% vs. 7±1% decrease in core temperature, n=6), and peritoneal exudate mediator levels (TNF-α, 0.78±0.2 vs. 0.38±0.1 ng/ml; nitrite, for NO, 35±10 vs. 15±3 μM; n=8) in TRPV1 KO mice, indicating loss of protective effect. Findings correlated with liver edema and raised plasma levels of aspartate aminotransferase in TRPV1 KO mice. These data suggest that TRPV1 may play an important regulatory role in sepsis independent of the major sensory neuropeptide substance P. The findings are relevant to developing strategies that increase the beneficial, and reduce the harmful, components of sepsis to prevent and treat this often fatal condition.--Clark, N., Keeble, J., Fernandes, E. S., Starr, A., Liang, L., Sugden, D., de Winter, P., Brain, S. D. The transient receptor potential vanilloid 1 (TRPV1) receptor protects against the onset of sepsis after endotoxin.
The Weddell Sea sector is one of the main formation sites for Antarctic Bottom Water and an outlet for about one fifth of Antarctica's continental ice volume. Over the last few decades, studies on ...glacial–geological records in this sector have provided conflicting reconstructions of changes in ice-sheet extent and ice-sheet thickness since the Last Glacial Maximum (LGM at ca 23–19 calibrated kiloyears before present, cal ka BP). Terrestrial geomorphological records and exposure ages obtained from rocks in the hinterland of the Weddell Sea, ice-sheet thickness constraints from ice cores and some radiocarbon dates on offshore sediments were interpreted to indicate no significant ice thickening and locally restricted grounding-line advance at the LGM. Other marine geological and geophysical studies concluded that subglacial bedforms mapped on the Weddell Sea continental shelf, subglacial deposits and sediments over-compacted by overriding ice recovered in cores, and the few available radiocarbon ages from marine sediments are consistent with major ice-sheet advance at the LGM. Reflecting the geological interpretations, different ice-sheet models have reconstructed conflicting LGM ice-sheet configurations for the Weddell Sea sector. Consequently, the estimated contributions of ice-sheet build-up in the Weddell Sea sector to the LGM sea-level low-stand of ∼130 m vary considerably.
In this paper, we summarise and review the geological records of past ice-sheet margins and past ice-sheet elevations in the Weddell Sea sector. We compile marine and terrestrial chronological data constraining former ice-sheet size, thereby highlighting different levels of certainty, and present two alternative scenarios of the LGM ice-sheet configuration, including time-slice reconstructions for post-LGM grounding-line retreat. Moreover, we discuss consistencies and possible reasons for inconsistencies between the various reconstructions and propose objectives for future research. The aim of our study is to provide two alternative interpretations of glacial–geological datasets on Antarctic Ice-Sheet History for the Weddell Sea sector, which can be utilised to test and improve numerical ice-sheet models.
ABSTRACTEpidemiological evidence suggests that populations consuming large amounts of soy protein have a reduced incidence of coronary heart disease (1–5). The cardiovascular risks associated with ...conventional hormone replacement therapy in postmenopausal women (5–7) have precipitated a search for alternative estrogen receptor modulators. Here we report that long‐term feeding of rats with a soy protein‐rich (SP) diet during gestation and adult life results in decreased oxidative stress, improved endothelial function, and reduced blood pressure in vivo measured by radiotelemetry in aged male offspring. Improved vascular reactivity in animals fed an SP diet was paralleled by increased mitochondrial glutathione and mRNA levels for endothelial nitric oxide synthase (eNOS) and the antioxidant enzymes manganese superoxide dismutase and cytochrome c oxidase. Reduced eNOS and antioxidant gene expression, impaired endothelial function, and elevated blood pressure in animals fed a soy‐deficient diet was reversed after refeeding them an SP diet for 6 months. Our findings suggest that an SP diet increases eNOS and antioxidant gene expression in the vasculature and other tissues, resulting in reduced oxidative stress and increased NO bioavailability. The improvement in endothelial function, increased gene expression, and reduced blood pressure by soy isoflavones have implications for alternative therapy for postmenopausal women and patients at risk of coronary heart disease.
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