| 1. |
- Beaty, D.W, et al.
(författare)
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The potential science and engineering value of samples delivered to Earth by Mars sample return : International MSR Objectives and Samples Team (iMOST)
- 2019
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Ingår i: Meteoritics and Planetary Science. - : John Wiley & Sons. - 1086-9379 .- 1945-5100. ; 54:S1, s. 3-152
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Tidskriftsartikel (refereegranskat)abstract
- Executive Summary: Return of samples from the surface of Mars has been a goal of the international Mars science community for many years. Affirmation by NASA and ESA of the importance of Mars exploration led the agencies to establish the international MSR Objectives and Samples Team (iMOST). The purpose of the team is to re-evaluate and update the sample-related science and engineering objectives of a Mars Sample Return (MSR) campaign. The iMOST team has also undertaken to define the measurements and the types of samples that can best address the objectives. Seven objectives have been defined for MSR, traceable through two decades of previously published international priorities. The first two objectives are further divided into sub-objectives. Within the main part of the report, the importance to science and/or engineering of each objective is described, critical measurements that would address the objectives are specified, and the kinds of samples that would be most likely to carry key information are identified. These seven objectives provide a framework for demonstrating how the first set of returned Martian samples would impact future Martian science and exploration. They also have implications for how analogous investigations might be conducted for samples returned by future missions from other solar system bodies, especially those that may harbor biologically relevant or sensitive material, such as Ocean Worlds (Europa, Enceladus, Titan) and others. Summary of Objectives and Sub-Objectives for MSR Identified by iMOST: Objective 1 Interpret the primary geologic processes and history that formed the Martian geologic record, with an emphasis on the role of water. Intent To investigate the geologic environment(s) represented at the Mars 2020 landing site, provide definitive geologic context for collected samples, and detail any characteristics that might relate to past biologic processesThis objective is divided into five sub-objectives that would apply at different landing sites. 1.1 Characterize the essential stratigraphic, sedimentologic, and facies variations of a sequence of Martian sedimentary rocks. Intent To understand the preserved Martian sedimentary record. Samples A suite of sedimentary rocks that span the range of variation. Importance Basic inputs into the history of water, climate change, and the possibility of life 1.2 Understand an ancient Martian hydrothermal system through study of its mineralization products and morphological expression. Intent To evaluate at least one potentially life-bearing “habitable” environment Samples A suite of rocks formed and/or altered by hydrothermal fluids. Importance Identification of a potentially habitable geochemical environment with high preservation potential. 1.3 Understand the rocks and minerals representative of a deep subsurface groundwater environment. Intent To evaluate definitively the role of water in the subsurface. Samples Suites of rocks/veins representing water/rock interaction in the subsurface. Importance May constitute the longest-lived habitable environments and a key to the hydrologic cycle. 1.4 Understand water/rock/atmosphere interactions at the Martian surface and how they have changed with time. Intent To constrain time-variable factors necessary to preserve records of microbial life. Samples Regolith, paleosols, and evaporites. Importance Subaerial near-surface processes could support and preserve microbial life. 1.5 Determine the petrogenesis of Martian igneous rocks in time and space. Intent To provide definitive characterization of igneous rocks on Mars. Samples Diverse suites of ancient igneous rocks. Importance Thermochemical record of the planet and nature of the interior. Objective 2 Assess and interpret the potential biological history of Mars, including assaying returned samples for the evidence of life. Intent To investigate the nature and extent of Martian habitability, the conditions and processes that supported or challenged life, how different environments might have influenced the preservation of biosignatures and created nonbiological “mimics,” and to look for biosignatures of past or present life.This objective has three sub-objectives: 2.1 Assess and characterize carbon, including possible organic and pre-biotic chemistry. Samples All samples collected as part of Objective 1. Importance Any biologic molecular scaffolding on Mars would likely be carbon-based. 2.2 Assay for the presence of biosignatures of past life at sites that hosted habitable environments and could have preserved any biosignatures. Samples All samples collected as part of Objective 1. Importance Provides the means of discovering ancient life. 2.3 Assess the possibility that any life forms detected are alive, or were recently alive. Samples All samples collected as part of Objective 1. Importance Planetary protection, and arguably the most important scientific discovery possible. Objective 3 Quantitatively determine the evolutionary timeline of Mars. Intent To provide a radioisotope-based time scale for major events, including magmatic, tectonic, fluvial, and impact events, and the formation of major sedimentary deposits and geomorphological features. Samples Ancient igneous rocks that bound critical stratigraphic intervals or correlate with crater-dated surfaces. Importance Quantification of Martian geologic history. Objective 4 Constrain the inventory of Martian volatiles as a function of geologic time and determine the ways in which these volatiles have interacted with Mars as a geologic system. Intent To recognize and quantify the major roles that volatiles (in the atmosphere and in the hydrosphere) play in Martian geologic and possibly biologic evolution. Samples Current atmospheric gas, ancient atmospheric gas trapped in older rocks, and minerals that equilibrated with the ancient atmosphere. Importance Key to understanding climate and environmental evolution. Objective 5 Reconstruct the processes that have affected the origin and modification of the interior, including the crust, mantle, core and the evolution of the Martian dynamo. Intent To quantify processes that have shaped the planet's crust and underlying structure, including planetary differentiation, core segregation and state of the magnetic dynamo, and cratering. Samples Igneous, potentially magnetized rocks (both igneous and sedimentary) and impact-generated samples. Importance Elucidate fundamental processes for comparative planetology. Objective 6 Understand and quantify the potential Martian environmental hazards to future human exploration and the terrestrial biosphere. Intent To define and mitigate an array of health risks related to the Martian environment associated with the potential future human exploration of Mars. Samples Fine-grained dust and regolith samples. Importance Key input to planetary protection planning and astronaut health. Objective 7 Evaluate the type and distribution of in-situ resources to support potential future Mars exploration. Intent To quantify the potential for obtaining Martian resources, including use of Martian materials as a source of water for human consumption, fuel production, building fabrication, and agriculture. Samples Regolith. Importance Production of simulants that will facilitate long-term human presence on Mars. Summary of iMOST Findings: Several specific findings were identified during the iMOST study. While they are not explicit recommendations, we suggest that they should serve as guidelines for future decision making regarding planning of potential future MSR missions. The samples to be collected by the Mars 2020 (M-2020) rover will be of sufficient size and quality to address and solve a wide variety of scientific questions. Samples, by definition, are a statistical representation of a larger entity. Our ability to interpret the source geologic units and processes by studying sample sub sets is highly dependent on the quality of the sample context. In the case of the M-2020 samples, the context is expected to be excellent, and at multiple scales. (A) Regional and planetary context will be established by the on-going work of the multi-agency fleet of Mars orbiters. (B) Local context will be established at field area- to outcrop- to hand sample- to hand lens scale using the instruments carried by M-2020. A significant fraction of the value of the MSR sample collection would come from its organization into sample suites, which are small groupings of samples designed to represent key aspects of geologic or geochemical variation. If the Mars 2020 rover acquires a scientifically well-chosen set of samples, with sufficient geological diversity, and if those samples were returned to Earth, then major progress can be expected on all seven of the objectives proposed in this study, regardless of the final choice of landing site. The specifics of which parts of Objective 1 could be achieved would be different at each of the final three candidate landing sites, but some combination of critically important progress could be made at any of them. An aspect of the search for evidence of life is that we do not know in advance how evidence for Martian life would be preserved in the geologic record. In order for the returned samples to be most useful for both understanding geologic processes (Objective 1) and the search for life (Objective 2), the sample collection should contain BOTH typical and unusual samples from the rock units explored. This consideration should be incorporated into sample selection and the design of the suites. The retrieval missions of a MSR campaign should (1) minimize stray magnetic fields to which the samples would be exposed and carry a magnetic witness plate to record exposure, (2) collect and return atmospheric gas sample(s), and (3) collect additional dust and/or regolith sample mass if possible.
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| 2. |
- Ewers, Michael, et al.
(författare)
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Body mass index is associated with biological CSF markers of core brain pathology of Alzheimer's disease
- 2012
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Ingår i: Neurobiology of Aging. - : Elsevier BV. - 1558-1497 .- 0197-4580. ; 33:8, s. 1599-1608
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Tidskriftsartikel (refereegranskat)abstract
- Weight changes are common in aging and Alzheimer's disease (AD) and postmortem findings suggest a relation between lower body mass index (BMI) and increased AD brain pathology. In the current multicenter study, we tested whether lower BMI is associated with higher core AD brain pathology as assessed by cerebrospinal fluid (CSF)-based biological markers of AD in 751 living subjects: 308 patients with AD, 296 subjects with amnestic mild cognitive impairment (MCI), and 147 elderly healthy controls (HC). Based upon a priori cutoff values on CSF concentration of total tau and beta-amyloid (A beta(1-42)), subjects were binarized into a group with abnormal CSF biomarker signature (CSF+) and those without (CSF-). Results showed that BMI was significantly lower in the CSF+ when compared with the CSF- group (F = 27.7, df = 746, p < 0.001). There was no interaction between CSF signature and diagnosis or apolipoprotein E (ApoE) genotype. In conclusion, lower BMI is indicative of AD pathology as assessed with CSF-based biomarkers in demented and nondemented elderly subjects. Published by Elsevier Inc.
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| 3. |
- Kotrschal, Alexander, et al.
(författare)
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The mating brain : early maturing sneaker males maintain investment into the brain also under fast body growth in Atlantic salmon (Salmo salar)
- 2014
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Ingår i: Evolutionary Ecology. - : Springer Science and Business Media LLC. - 0269-7653 .- 1573-8477. ; 28:6, s. 1043-1055
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Tidskriftsartikel (refereegranskat)abstract
- It has been suggested that mating behaviours require high levels of cognitive ability. However, since investment into mating and the brain both are costly features, their relationship is likely characterized by energetic trade-offs. Empirical data on the subject remains equivocal. We investigated if early sexual maturation was associated with brain development in Atlantic salmon (Salmo salar), in which males can either stay in the river and sexually mature at a small size (sneaker males) or migrate to the sea and delay sexual maturation until they have grown much larger (anadromous males). Specifically, we tested how sexual maturation may induce plastic changes in brain development by rearing juveniles on either natural or ad libitum feeding levels. After their first season we compared brain size and brain region volumes across both types of male mating tactics and females. Body growth increased greatly across both male mating tactics and females during ad libitum feeding as compared to natural feeding levels. However, despite similar relative increases in body size, early maturing sneaker males maintained larger relative brain size during ad libitum feeding levels as compared to anadromous males and females. We also detected several differences in the relative size of separate brain regions across feeding treatments, sexes and mating strategies. For instance, the relative size of the cognitive centre of the brain, the telencephalon, was largest in sneaker males. Our data support that a large relative brain size is maintained in individuals that start reproduction early also during fast body growth. We propose that the cognitive demands during complex mating behaviours maintain a high level of investment into brain development in reproducing individuals.
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| 4. |
- Shao, Yi Ta, et al.
(författare)
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Androgen feedback effects on LH and FSH, and photoperiodic control of reproduction in male three-spined sticklebacks, Gasterosteus aculeatus
- 2013
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Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 182, s. 16-23
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Tidskriftsartikel (refereegranskat)abstract
- Sexual maturation in the stickleback is controlled by photoperiod. The aim of this study was to find out whether changes in feedback effects exerted by sex steroids could mediate the photoperiodic effect, which is regarded to be of an all-or-nothing character. To that end, males were castrated and treated with different doses of testosterone (T) and in one experiment also with the aromatase inhibitor fadrozole (AI) and kept under different photoperiods. In control fish, long day (LD 16:8) stimulated maturation, associated with more hypertrophied kidneys (a secondary sexual character) and higher levels of pituitary lhb and fshb mRNA than under short day conditions (LD 8:16). Under LD 8:16, low doses of T suppressed both lhb and fshb mRNA levels. However, with the use of high doses of T and/or longer photoperiods the inhibitory effects on lhb and fshb mRNA levels became less clear or instead positive effects were observed. Under intermediate photoperiod conditions, the negative feedback effect of a low dose of T on fshb was more prominent with shorter photoperiods, whereas no such shift was observed for lhb mRNA. The inhibitory effect of the low dose of T on lhb mRNA levels under LD 8:16 was abolished by AI, whereas the stimulatory effect of the high dose of T was not. The negative feedback effects were more marked under short days than under long days, whereas positive feedback effects were more marked under long days. The suppression of both fshb and lhb mRNA levels by low androgen levels, especially under short days, may inhibit maturation completely unless a rise of androgens above threshold levels would allow complete maturation.
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| 5. |
- Shao, Yi Ta, et al.
(författare)
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Schistocephalus solidus infections increase gonadotropins and gonadotropin releasing hormone (GnRH3) mRNA levels in the three-spined stickleback, Gasterosteus aculeatus
- 2012
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Ingår i: Parasitology international. - : Elsevier BV. - 1383-5769 .- 1873-0329. ; 61:3, s. 470-474
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Tidskriftsartikel (refereegranskat)abstract
- Parasites often impair the reproduction of their hosts, one well known case being the cestode Schistocephalus solidus which is a common parasite in three-spined sticklebacks. Gasterosteus aculeatus. One of the possible ways that this could be exerted is by suppression on the brain-pituitary-gonadal (BPG) axis. In this study, mRNA levels of FSH-beta and LH-beta and of GnRH2 (cGnRH II) and GnRH3 (sGnRH) were measured via Q-PCR in infected and uninfected fish sampled from the field a few weeks before the onset of breeding. The pituitary mRNA levels of both FSH-beta and LH-beta were higher in infected males than in uninfected males. Also in females, FSH-beta mRNA levels were higher in infected individuals than in others, whereas there was no significant difference found in LH-beta expression. Brain mRNA levels of GnRH3 were higher in infected fish than in uninfected fish in both sexes, but no difference was found in GnRH2 mRNA levels. Thus, infection by S. solidus was able to alter the expressions not only of gonadotropins (GtHs), but also of GnRH which has not been observed previously. However, the effects are opposite to what should be expected if the parasite suppressed reproduction via actions on the brain-pituitary level. The gonads are perhaps more likely to be impaired by the parasites in other ways, and changed feedbacks on the BPG axis could then lead to the increases in GtHs and GnRH.
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| 6. |
- Trombley, Susanne, 1979-, et al.
(författare)
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Effects of androgens on the leptin system in immature male Atlantic salmon parr
- 2018
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Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 257, s. 122-129
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Tidskriftsartikel (refereegranskat)abstract
- Leptin modulates all levels of the reproductive endocrine axis in mammals, and in turn, both leptin and the leptin receptor are regulated by sex steroids. The aim of this study was to investigate if sex steroids regulate the leptin system also in fish. Immature one-year old male Atlantic salmon parr were implanted with Silclear capsules that were either empty or filled with 11-ketoandrostenedione (11 KA) or testosterone (T) and the effects of 35-days treatment were investigated on measures of maturation, gene expression of leptin (lepa1, lepa2), leptin receptor (lepra1) and circulating plasma leptin. Both 11-KA and T stimulated the reproductive axis by increasing testes weight and up-regulated pituitary lh-beta mRNA levels and for T also fsh-beta. T up-regulated transcription levels of lepa1 and lepra1 in the pituitary, while 11-KA had no effect. Leptin receptor expression in the testis was unaltered by either androgen. T up-regulated lepa1 mRNA levels significantly also in the liver, but had no effect on lepa2, and 11 KA did not affect hepatic gene expression of either lepa1 or lepa2. Plasma leptin levels did not differ significantly between treatments. The results indicate that androgens regulate gene expression of leptin and the leptin receptor in different tissues in fish and that the effects of leptin might be tissue specific considering plasma levels remained unaltered. Overall, the results suggest a role for leptin in fish reproduction, where sex steroids are able to regulate components of the leptin system differentially in liver and important tissues of the reproductive axis. (C) 2017 Elsevier Inc. All rights reserved.
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| 7. |
- Trombley, Susanne, et al.
(författare)
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Effects of long-term restricted feeding on plasma leptin, hepatic leptin expression and leptin receptor expression in juvenile Atlantic salmon (Salmo salar L.)
- 2012
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Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 175:1, s. 92-99
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Tidskriftsartikel (refereegranskat)abstract
- Leptin is a pleiotropic hormone and plays a key role in body weight regulation, energy homeostasis and lipid store utilization in mammals. In this study, we investigated the effect of feed-restriction on leptin genes (lepa1 and lepa2), leptin receptor (lepr) gene expression and plasma leptin levels in juvenile Atlantic salmon parr. Feed restriction was performed from late April to mid-June, in order to gain insight into the role of the leptin system in energy balance regulation and adiposity in juvenile salmon. A significant increase in lepa1 expression as well as higher levels of plasma leptin was found in feed-restricted fish in June compared to fully fed controls, while lepa2 gene expression decreased in both groups during the treatment period. Lepa2 was, however significantly higher in the feed-restricted group in June. Leptin receptor expression was up regulated during the period of enhanced growth and lipid deposition in the fully fed control, indicating a seasonal effect on the receptor expression in the brain. Both lepa1 and lepa2 genes very mainly expressed in the liver in juvenile salmon, while lepr was expressed in the brain but showed also considerable expression in various peripheral tissues. The study provides evidence that the leptin system is sensitive to the metabolic status of the fish as both season and restricted feeding affect lepa1 and lepa2 gene expression in the liver and brain leptin receptor expression, however, for lepa1 expression and leptin plasma level in an opposite way as that observed in the mammalian system. (C) 2011 Elsevier Inc. All rights reserved.
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| 8. |
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| 9. |
- Trombley, Susanne, et al.
(författare)
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Leptin in fish : possible role in sexual maturation in male Atlantic salmon
- 2013
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Ingår i: Fish Physiology & Biochemistry. - : Springer Science and Business Media LLC. - 0920-1742 .- 1573-5168. ; 39:1, s. 103-106
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Tidskriftsartikel (refereegranskat)abstract
- Leptin plays an important role in energy homeostasis and reproductive function in mammals, while its function in fish is still poorly understood, especially its role in reproduction. In the present study, leptin gene expression and circulating leptin plasma levels were measured during sexual maturation in male Atlantic salmon parr. In maturing male salmon, higher hepatic leptin (lepa1) gene expression levels were observed during mid-spermatogenesis compared to immature fish. An upregulation of leptin during sexual maturation has also been observed in a few other teleost species. The physiological significance of elevated leptin levels during the maturational process in teleosts remains to be explored.
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| 10. |
- Trombley, Susanne, 1979-
(författare)
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Regulation of Leptin by Sexual Maturation and Energy Status in Male Atlantic Salmon (Salmo salar L.) Parr
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Leptin is a peripheral adiposity signal and a key hormone in energy balance regulation in mammals, acting as a link between nutritional status and the endocrine reproductive axis. If this is also the role of leptin in fish is not fully understood. This thesis investigates how different components of the leptin system are affected by sexual maturation and seasonal changes in energy balance in male Atlantic salmon (Salmo salar L.) parr under fully fed and feed-restricted conditions. Moreover, the role of sex steroids as being one of the possible mechanisms by which sexual maturation interacts with leptin is explored.The salmon leptin-a genes, lepa1 and lepa2, were expressed mainly in liver and the leptin receptor (lepr) in brain and ubiquitously in peripheral tissues. Seasonal characterization of the lepa genes and lepr during the growth and reproductive season in one-year old males showed that hepatic lepa1 and lepa2 mRNA levels and plasma leptin levels were down-regulated concomitantly with an increase in weight and body fat. Feed restriction up-regulated hepatic leptin, and pituitary lepr expression as well as plasma leptin levels. Correlation between leptin levels and body lipid stores were either lacking or negative. These findings show that leptin and lepr are sensitive to changes in energy balance, but that leptin might not reflect adiposity in juvenile salmon.Hepatic lepa1 and lepa2, and testicular lepr expression increased during mid- to late spermatogenesis in early maturing males. This up-regulation was preceded by rapid gonadal growth and elevated pituitary follicle-stimulating hormone gene expression levels, whereas peak leptin levels coincided with peak pituitary luteinizing hormone expression and the presence of running milt in the testes. The sex steroids testosterone (T), 11-ketotestosterone and 17-β estradiol stimulated lepa1 and lepa2 gene expression in Atlantic salmon hepatocytes in vitro differentially depending on developmental stage. T was also able to stimulate hepatic lepa1 and pituitary lepa1 and lepr gene expression in immature male salmon in vivo. These results suggest that leptin plays a role in male fish reproduction during later stages of the maturational process and that the elevation of leptin expression during spermatogenesis could be caused by androgen stimulation.
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