| 1. |
- Orlando, Ludovic, et al.
(författare)
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Recalibrating Equus evolution using the genome sequence of an early Middle Pleistocene horse
- 2013
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 499:7456, s. 74-
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Tidskriftsartikel (refereegranskat)abstract
- The rich fossil record of equids has made them a model for evolutionary processes(1). Here we present a 1.12-times coverage draft genome from a horse bone recovered from permafrost dated to approximately 560-780 thousand years before present (kyr BP)(2,3). Our data represent the oldest full genome sequence determined so far by almost an order of magnitude. For comparison, we sequenced the genome of a Late Pleistocene horse (43 kyr BP), and modern genomes of five domestic horse breeds (Equus ferus caballus), a Przewalski's horse (E. f. prze-walskii) and a donkey (E. asinus). Our analyses suggest that the Equus lineage giving rise to all contemporary horses, zebras and donkeys originated 4.0-4.5 million years before present (Myr BP), twice the conventionally accepted time to the most recent common ancestor of the genus Equus(4,5). We also find that horse population size fluctuated multiple times over the past 2 Myr, particularly during periods of severe climatic changes. We estimate that the Przewalski's and domestic horse populations diverged 38-72 kyr BP, and find no evidence of recent admixture between the domestic horse breeds and the Przewalski's horse investigated. This supports the contention that Przewalski's horses represent the last surviving wild horse population(6). We find similar levels of genetic variation among Przewalski's and domestic populations, indicating that the former are genetically viable and worthy of conservation efforts. We also find evidence for continuous selection on the immune system and olfaction throughout horse evolution. Finally, we identify 29 genomic regions among horse breeds that deviate from neutrality and show low levels of genetic variation compared to the Przewalski's horse. Such regions could correspond to loci selected early during domestication.
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| 2. |
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| 3. |
- Rasmussen, Sune Olander, et al.
(författare)
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Ice-core data used for the construction of the Greenland Ice-Core Chronology 2005 and 2021 (GICC05 and GICC21)
- 2023
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Ingår i: Earth System Science Data. - 1866-3508 .- 1866-3516. ; 15:8, s. 3351-3364
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Tidskriftsartikel (refereegranskat)abstract
- We here describe, document, and make available a wide range of data sets used for annual-layer identification in ice cores from DYE-3, GRIP, NGRIP, NEEM, and EGRIP. The data stem from detailed measurements performed both on the main deep cores and shallow cores over more than 40 years using many different setups developed by research groups in several countries and comprise both discrete measurements from cut ice samples and continuous-flow analysis data.The data series were used for counting annual layers 60 000 years back in time during the construction of the Greenland Ice-Core Chronology 2005 (GICC05) and/or the revised GICC21, which currently only reaches 3800 years back. Now that the underlying data are made available (listed in Table 1) we also release the individual annual-layer positions of the GICC05 timescale which are based on these data sets.We hope that the release of the data sets will stimulate further studies of the past climate taking advantage of these highly resolved data series covering a large part of the interior of the Greenland ice sheet.
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| 4. |
- Sinnl, Giulia, et al.
(författare)
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A multi-ice-core, annual-layer-counted Greenland ice-core chronology for the last 3800 years : GICC21
- 2022
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 18:5, s. 1125-1150
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Tidskriftsartikel (refereegranskat)abstract
- Ice-core timescales are vital for the understanding of past climate; hence they should be updated whenever significant amounts of new data become available. Here, the Greenland ice-core chronology GICC05 was revised for the last 3835 years by synchronizing six deep ice cores and three shallow ice cores from the central Greenland ice sheet. A new method was applied by combining automated counting of annual layers on multiple parallel proxies and manual fine-tuning. A layer counting bias was found in all ice cores because of site-specific signal disturbances; therefore the manual comparison of all ice cores was deemed necessary to increase timescale accuracy. After examining sources of error and their correlation lengths, the uncertainty rate was quantified to be 1 year per century. The new timescale is younger than GICC05 by about 13 years at 3835 years ago. The most recent 800 years are largely unaffected by the revision. Between 800 and 2000 years ago, the offset between timescales increases steadily, with the steepest offset occurring between 800 and 1100 years ago. Moreover, offset oscillations of about 5 years around the average are observed between 2500 and 3800 years ago. The non-linear offset behavior is attributed to previous mismatches of volcanic eruptions, to the much more extensive dataset available to this study, and to the finer resolution of the new ice-core ammonium matching. By analysis of the common variations in cosmogenic radionuclides, the new ice-core timescale is found to be in alignment with the IntCal20 curve (Reimer et al., 2020).
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| 5. |
- Svensson, Anders, et al.
(författare)
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Bipolar volcanic synchronization of abrupt climate change in Greenland and Antarctic ice cores during the last glacial period
- 2020
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 16:4, s. 1565-1580
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Tidskriftsartikel (refereegranskat)abstract
- The last glacial period is characterized by a number of millennial climate events that have been identified in both Greenland and Antarctic ice cores and that are abrupt in Greenland climate records. The mechanisms governing this climate variability remain a puzzle that requires a precise synchronization of ice cores from the two hemispheres to be resolved. Previously, Greenland and Antarctic ice cores have been synchronized primarily via their common records of gas concentrations or isotopes from the trapped air and via cosmogenic isotopes measured on the ice. In this work, we apply ice core volcanic proxies and annual layer counting to identify large volcanic eruptions that have left a signature in both Greenland and Antarctica. Generally, no tephra is associated with those eruptions in the ice cores, so the source of the eruptions cannot be identified. Instead, we identify and match sequences of volcanic eruptions with bipolar distribution of sulfate, i.e. unique patterns of volcanic events separated by the same number of years at the two poles. Using this approach, we pinpoint 82 large bipolar volcanic eruptions throughout the second half of the last glacial period (12-60ka). This improved ice core synchronization is applied to determine the bipolar phasing of abrupt climate change events at decadal-scale precision. In response to Greenland abrupt climatic transitions, we find a response in the Antarctic water isotope signals (δ18O and deuterium excess) that is both more immediate and more abrupt than that found with previous gas-based interpolar synchronizations, providing additional support for our volcanic framework. On average, the Antarctic bipolar seesaw climate response lags the midpoint of Greenland abrupt δ18O transitions by 122±24 years. The time difference between Antarctic signals in deuterium excess and δ18O, which likewise informs the time needed to propagate the signal as described by the theory of the bipolar seesaw but is less sensitive to synchronization errors, suggests an Antarctic δ18O lag behind Greenland of 152±37 years. These estimates are shorter than the 200 years suggested by earlier gas-based synchronizations. As before, we find variations in the timing and duration between the response at different sites and for different events suggesting an interaction of oceanic and atmospheric teleconnection patterns as well as internal climate variability.
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| 6. |
- Vinther, Anders, et al.
(författare)
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Exercise-induced rib stress fractures: influence of reduced bone mineral density
- 2005
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Ingår i: Scandinavian Journal of Medicine & Science in Sports. - : Wiley. - 1600-0838 .- 0905-7188. ; 15:2, s. 95-99
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Tidskriftsartikel (refereegranskat)abstract
- Exercise-induced rib stress fractures have been reported frequently in elite rowers during the past decade. The etiology of rib stress fractures is unclear, but low bone mineral density (BMD) has been suggested to be a potential risk factor for stress fractures in weight-bearing bones. The present study investigated BMD in seven Danish national team rowers with previous rib stress fracture (RSF) and 7 controls (C) matched for gender, age, height, weight and training experience. Total body scan and specific scans of the lumbar spine (L2-L4), femoral neck and distal radius were performed using a DEXA scanner. The RSF subjects showed significantly lower L2-L4 BMD: RSF: 1.22 +/- 0.05 g cm(-2) (mean +/- SEM) (median 1.19 g cm(-2), range 1.02-1.37 g cm(-2)) compared to C: 140 +/- 0.04 g cm(-2) (median 1.41 g cm(-2), range 1.27-1.57 g cm(-2)) (P=0.028).The present results suggest that low bone mineral density may be a potential risk factor for the development of exercise-induced rib stress fractures in elite rowers.
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| 7. |
- Vinther, Anders
(författare)
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Rib stress fractures in elite rowers
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim was to investigate potential risk factors and suggested injury mechanisms involved in the development of exercise-induced rib stress fractures (RSF) in elite rowers as well as investigate biomechanical and neuromuscular differences of ergometer rowing in stationary and slide-based ergometers. BMD and muscle strength was assessed as well as EMG of thoracic muscles and rowing technique during ergometer rowing in rowers with previous RSF and controls. The RSF subjects displayed reduced lumbar spine BMD, increased co-contraction of thoracic muscles and increased elbow-flexion strength relative to knee-extension strength. Testosterone levels and BMD were measured in male lightweight rowers. Correlations between BMD and testosterone levels as well as years of training were found. The force production during ergometer rowing with and without slides was measured in male and female rowers. During slide-based ergometer rowing male rowers increased stroke rate and decreased peak force. Female rowers displayed a similar but less pronounced response. The neuromuscular activity of muscles potentially involved in RSF development was measured during ergometer rowing with and without slides in male rowers. Slide-based ergometer rowing did not affect the neuromuscular activity significantly, except during the unloaded recovery phase of the rowing stroke. The timing of peak neuromuscular activity of the thoracic muscles coincided with the timing of peak force at the handle supporting rib cage compression as a potential injury mechanism. The Thesis has added knowledge regarding risk factors and injury mechanisms involved in RSF development, which may be useful for future studies on RSF prevention in rowers.
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| 8. |
- Vinther, Anders, et al.
(författare)
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Slide-based ergometer rowing: Effects on force production and neuromuscular activity.
- 2013
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Ingår i: Scandinavian Journal of Medicine & Science in Sports. - : Wiley. - 1600-0838 .- 0905-7188. ; 23:5, s. 635-644
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Tidskriftsartikel (refereegranskat)abstract
- Force production profile and neuromuscular activity during slide-based and stationary ergometer rowing at standardized submaximal power output were compared in 14 male and 8 female National Team rowers. Surface electromyography (EMG) was obtained in selected thoracic and leg muscles along with synchronous measurement of handle force and rate of force development (RFD). Compared to stationary conditions, slide-based peak force decreased by 76 (57-95) N (mean 95% CI) in males (P < 0.001) and 20 (8-31) N (P < 0.05) in females. Stroke rate increased (+10.7%) and late-phase RFD decreased (-20.7%) in males (P < 0.05). Neuromuscular activity in m. vastus lateralis decreased in the initial drive phase from 59% to 51% of EMGmax in males and from 57% to 52% in females (P < 0.01-0.05), while also decreasing in the late recovery phase from 20% to 7% in males and 17% to 7% in females (P < 0.01). Peak force and maximal neuromuscular activity in the shoulder retractors always occurred in the second quartile of the drive phase. In conclusion, peak force and late-phase RFD (males) decreased and stroke rate increased (males) during slide-based compared to stationary ergometer rowing, potentially reducing the risk of overuse injury. Neuromuscular activity was more affected in leg muscles than thoracic muscles by slide-based ergometer rowing.
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| 9. |
- Vinther, Anders, et al.
(författare)
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Testosterone and BMD in Elite Male Lightweight Rowers
- 2008
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Ingår i: International Journal of Sports Medicine. - : Georg Thieme Verlag KG. - 0172-4622 .- 1439-3964. ; 29:10, s. 803-807
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the present study was to investigate if a relationship between BMD and testosterone levels could be identified in elite male lightweight rowers. Thirteen male lightweight national team rowers had their BMD measured in a DEXA scanner. Plasma concentrations of total testosterone (TT), free testosterone (IFT), dihydrotestosterone (DHT) and sex hormone binding globulin (SHBG) and additional parameters related to bone metabolism were measured. Plasma concentrations of TT, FT and DHT were in the lower part of the normal range, while BMD was close to or above normal. BMD of total body and L2-L4 were correlated to years of training (r(s): 0.59, p = 0.034 and r(s): 0.73, p = 0.005) and to TT (r(s): 0.56, p = 0.046 and rs: 0.63, p = 0.021). Moreover, L2 - L4 BMD was correlated to FT (r(s): 0.62, p = 0.024). After adjusting for years of training, partial correlation analysis showed a significant correlation between L2-L4 BMD and TT (r(s): 0.61, p < 0.05). BMD appears to be influenced by both testosterone levels and years of training in elite male lightweight rowers. The relatively high BMD and low testosterone levels indicate that the mechanical loading induced by rowing is more important to BMD than testosterone levels. Prospective investigations are needed to elucidate potential causal relationships.
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