PeerJ
type: channel
link: https://peerj.com/articles/
description: Articles published in PeerJ
publisher: PeerJ Inc.
publication name: PeerJ
issn: 2167-8359
items: Coping with shorter days: do phenology shifts constrain aphid fitness?
items: Marked increase in rat red blood cell membrane protein glycosylation by one-month treatment with a cafeteria diet
items: Do the effects of crops on skylark (Alauda arvensis) differ between the field and landscape scales?
items: Pest control of aphids depends on landscape complexity and natural enemy interactions
items: Constant illumination reduces circulating melatonin and impairs immune function in the cricket Teleogryllus commodus
items: Photos provide information on age, but not kinship, of Andean bear
items: Influence of a hyperlipidic diet on the composition of the non-membrane lipid pool of red blood cells of male and female rats
items: Urinary microRNA can be concentrated, dried on membranes and stored at room temperature in vacuum bags
items: Using signals associated with safety in avoidance learning: computational model of sex differences
items: Allele specific expression in worker reproduction genes in the bumblebee Bombus terrestris

Coping with shorter days: do phenology shifts constrain aphid fitness?
type: item
type: AcademicArticle
description: Climate change can alter the phenology of organisms. It may thus lead seasonal organisms to face different day lengths than in the past, and the fitness consequences of these changes are as yet unclear. To study such effects, we used the pea aphid Acyrthosiphon pisum as a model organism, as it has obligately asexual clones which can be used to study day length effects without eliciting a seasonal response. We recorded life-history traits under short and long days, both with two realistic temperature cycles with means differing by 2 °C. In addition, we measured the population growth of aphids on their host plant Pisum sativum. We show that short days reduce fecundity and the length of the reproductive period of aphids. Nevertheless, this does not translate into differences at the population level because the observed fitness costs only become apparent late in the individual’s life. As expected, warm temperature shortens the development time by 0.7 days/°C, leading to faster generation times. We found no interaction of temperature and day length. We conclude that day length changes cause only relatively mild costs, which may not decelerate the increase in pest status due to climate change.
format: application/pdf
format: text/html
creator: Jens Joschinski
creator: Thomas Hovestadt
creator: Jochen Krauss
subject: Animal Behavior
subject: Biodiversity
subject: Ecology
subject: Entomology
subject: Evolutionary Studies
description: doi:10.7717/peerj.1103
publisher: PeerJ Inc.
rights: © 2015 Joschinski et al.
abstract: Climate change can alter the phenology of organisms. It may thus lead seasonal organisms to face different day lengths than in the past, and the fitness consequences of these changes are as yet unclear. To study such effects, we used the pea aphid Acyrthosiphon pisum as a model organism, as it has obligately asexual clones which can be used to study day length effects without eliciting a seasonal response. We recorded life-history traits under short and long days, both with two realistic temperature cycles with means differing by 2 °C. In addition, we measured the population growth of aphids on their host plant Pisum sativum. We show that short days reduce fecundity and the length of the reproductive period of aphids. Nevertheless, this does not translate into differences at the population level because the observed fitness costs only become apparent late in the individual’s life. As expected, warm temperature shortens the development time by 0.7 days/°C, leading to faster generation times. We found no interaction of temperature and day length. We conclude that day length changes cause only relatively mild costs, which may not decelerate the increase in pest status due to climate change.
bibliographic citation: Joschinski et al. (2015) Coping with shorter days: do phenology shifts constrain aphid fitness?. PeerJ 3:e1103 https://doi.org/10.7717/peerj.1103
date submitted: 2015-05-28
date accepted: 2015-06-24
issued: 2015-07-16
is part of: PeerJ
license: http://creativecommons.org/licenses/by/4.0/
author list: Agent
  family name: Joschinski
  given name: Jens
author list: Agent
  family name: Hovestadt
  given name: Thomas
author list: Agent
  family name: Krauss
  given name: Jochen
doi: 10.7717/peerj.1103
volume: 3
issn: 2167-8359
publication name: PeerJ
publication date: 2015-07-16
copyright: © 2015 Joschinski et al.
attribution name: Joschinski et al.

Marked increase in rat red blood cell membrane protein glycosylation by one-month treatment with a cafeteria diet
type: item
type: AcademicArticle
description: Background and Objectives. Glucose, an aldose, spontaneously reacts with protein amino acids yielding glycosylated proteins. The compounds may reorganize to produce advanced glycosylation products, which regulatory importance is increasingly being recognized. Protein glycosylation is produced without the direct intervention of enzymes and results in the loss of function. Glycosylated plasma albumin, and glycosylated haemoglobin are currently used as index of mean plasma glucose levels, since higher glucose availability results in higher glycosylation rates. In this study we intended to detect the early changes in blood protein glycosylation elicited by an obesogenic diet. Experimental Design. Since albumin is in constant direct contact with plasma glucose, as are the red blood cell (RBC) membranes, we analyzed their degree or glycosylation in female and male rats, either fed a standard diet or subjected to a hyper-energetic self-selected cafeteria diet for 30 days. This model produces a small increase in basal glycaemia and a significant increase in body fat, leaving the animals in the initial stages of development of metabolic syndrome. We also measured the degree of glycosylation of hemoglobin, and the concentration of glucose in contact with this protein, that within the RBC. Glycosylation was measured by colorimetric estimation of the hydroxymethylfurfural liberated from glycosyl residues by incubation with oxalate. Results. Plasma glucose was higher in cafeteria diet and in male rats, both independent effects. However, there were no significant differences induced by sex or diet in either hemoglobin or plasma proteins. Purified RBC membranes showed a marked effect of diet: higher glycosylation in cafeteria rats, which was more marked in females (not in controls). In any case, the number of glycosyl residues per molecule were higher in hemoglobin than in plasma proteins (after correction for molecular weight). The detected levels of glucose in RBC were lower tha…
format: application/pdf
format: text/html
creator: Laia Oliva
creator: Cristian Baron
creator: José-Antonio Fernández-López
creator: Xavier Remesar
creator: Marià Alemany
subject: Cell Biology
subject: Diabetes and Endocrinology
subject: Hematology
subject: Metabolic Sciences
description: doi:10.7717/peerj.1101
publisher: PeerJ Inc.
rights: © 2015 Oliva et al.
abstract: Background and Objectives. Glucose, an aldose, spontaneously reacts with protein amino acids yielding glycosylated proteins. The compounds may reorganize to produce advanced glycosylation products, which regulatory importance is increasingly being recognized. Protein glycosylation is produced without the direct intervention of enzymes and results in the loss of function. Glycosylated plasma albumin, and glycosylated haemoglobin are currently used as index of mean plasma glucose levels, since higher glucose availability results in higher glycosylation rates. In this study we intended to detect the early changes in blood protein glycosylation elicited by an obesogenic diet. Experimental Design. Since albumin is in constant direct contact with plasma glucose, as are the red blood cell (RBC) membranes, we analyzed their degree or glycosylation in female and male rats, either fed a standard diet or subjected to a hyper-energetic self-selected cafeteria diet for 30 days. This model produces a small increase in basal glycaemia and a significant increase in body fat, leaving the animals in the initial stages of development of metabolic syndrome. We also measured the degree of glycosylation of hemoglobin, and the concentration of glucose in contact with this protein, that within the RBC. Glycosylation was measured by colorimetric estimation of the hydroxymethylfurfural liberated from glycosyl residues by incubation with oxalate. Results. Plasma glucose was higher in cafeteria diet and in male rats, both independent effects. However, there were no significant differences induced by sex or diet in either hemoglobin or plasma proteins. Purified RBC membranes showed a marked effect of diet: higher glycosylation in cafeteria rats, which was more marked in females (not in controls). In any case, the number of glycosyl residues per molecule were higher in hemoglobin than in plasma proteins (after correction for molecular weight). The detected levels of glucose in RBC were lower tha…
bibliographic citation: Oliva et al. (2015) Marked increase in rat red blood cell membrane protein glycosylation by one-month treatment with a cafeteria diet. PeerJ 3:e1101 https://doi.org/10.7717/peerj.1101
date submitted: 2015-03-27
date accepted: 2015-06-22
issued: 2015-07-16
is part of: PeerJ
license: http://creativecommons.org/licenses/by/4.0/
author list: Agent
  family name: Oliva
  given name: Laia
author list: Agent
  family name: Baron
  given name: Cristian
author list: Agent
  family name: Fernández-López
  given name: José-Antonio
author list: Agent
  family name: Remesar
  given name: Xavier
author list: Agent
  family name: Alemany
  given name: Marià
doi: 10.7717/peerj.1101
volume: 3
issn: 2167-8359
publication name: PeerJ
publication date: 2015-07-16
copyright: © 2015 Oliva et al.
attribution name: Oliva et al.

Do the effects of crops on skylark (Alauda arvensis) differ between the field and landscape scales?
type: item
type: AcademicArticle
description: The promotion of biodiversity in agricultural areas involves actions at the landscape scale, and the management of cropping patterns is considered an important means of achieving this goal. However, most of the available knowledge about the impact of crops on biodiversity has been obtained at the field scale, and is generally grouped together under the umbrella term “crop suitability.” Can field-scale knowledge be used to predict the impact on populations across landscapes? We studied the impact of maize and rapeseed on the abundance of skylark (Alauda arvensis). Field-scale studies in Western Europe have reported diverse impacts on habitat selection and demography. We assessed the consistency between field-scale knowledge and landscape-scale observations, using high-resolution databases describing crops and other habitats for the 4 km2 grid scales analyzed in the French Breeding Bird Survey. We used generalized linear models to estimate the impact of each studied crop at the landscape scale. We stratified the squares according to the local and geographical contexts, to ensure that the conclusions drawn were valid in a wide range of contexts. Our results were not consistent with field knowledge for rapeseed, and were consistent for maize only in grassland contexts. However, the effect sizes were much smaller than those of structural landscape features. These results suggest that upscaling from the field scale to the landscape scale leads to an integration of new agronomic and ecological processes, making the objects studied more complex than simple “crop ∗ species” pairs. We conclude that the carrying capacity of agricultural landscapes cannot be deduced from the suitability of their components.
format: application/pdf
format: text/html
creator: Christophe Sausse
creator: Aude Barbottin
creator: Frédéric Jiguet
creator: Philippe Martin
subject: Agricultural Science
subject: Conservation Biology
subject: Ecology
subject: Environmental Sciences
subject: Spatial and Geographic Information Science
description: doi:10.7717/peerj.1097
publisher: PeerJ Inc.
rights: © 2015 Sausse et al.
abstract: The promotion of biodiversity in agricultural areas involves actions at the landscape scale, and the management of cropping patterns is considered an important means of achieving this goal. However, most of the available knowledge about the impact of crops on biodiversity has been obtained at the field scale, and is generally grouped together under the umbrella term “crop suitability.” Can field-scale knowledge be used to predict the impact on populations across landscapes? We studied the impact of maize and rapeseed on the abundance of skylark (Alauda arvensis). Field-scale studies in Western Europe have reported diverse impacts on habitat selection and demography. We assessed the consistency between field-scale knowledge and landscape-scale observations, using high-resolution databases describing crops and other habitats for the 4 km2 grid scales analyzed in the French Breeding Bird Survey. We used generalized linear models to estimate the impact of each studied crop at the landscape scale. We stratified the squares according to the local and geographical contexts, to ensure that the conclusions drawn were valid in a wide range of contexts. Our results were not consistent with field knowledge for rapeseed, and were consistent for maize only in grassland contexts. However, the effect sizes were much smaller than those of structural landscape features. These results suggest that upscaling from the field scale to the landscape scale leads to an integration of new agronomic and ecological processes, making the objects studied more complex than simple “crop ∗ species” pairs. We conclude that the carrying capacity of agricultural landscapes cannot be deduced from the suitability of their components.
bibliographic citation: Sausse et al. (2015) Do the effects of crops on skylark (Alauda arvensis) differ between the field and landscape scales?. PeerJ 3:e1097 https://doi.org/10.7717/peerj.1097
date submitted: 2015-03-20
date accepted: 2015-06-19
issued: 2015-07-16
is part of: PeerJ
license: http://creativecommons.org/licenses/by/4.0/
author list: Agent
  family name: Sausse
  given name: Christophe
author list: Agent
  family name: Barbottin
  given name: Aude
author list: Agent
  family name: Jiguet
  given name: Frédéric
author list: Agent
  family name: Martin
  given name: Philippe
doi: 10.7717/peerj.1097
volume: 3
issn: 2167-8359
publication name: PeerJ
publication date: 2015-07-16
copyright: © 2015 Sausse et al.
attribution name: Sausse et al.

Pest control of aphids depends on landscape complexity and natural enemy interactions
type: item
type: AcademicArticle
description: Aphids are a major concern in agricultural crops worldwide, and control by natural enemies is an essential component of the ecological intensification of agriculture. Although the complexity of agricultural landscapes is known to influence natural enemies of pests, few studies have measured the degree of pest control by different enemy guilds across gradients in landscape complexity. Here, we use multiple natural-enemy exclosures replicated in 18 fields across a gradient in landscape complexity to investigate (1) the strength of natural pest control across landscapes, measured as the difference between pest pressure in the presence and in the absence of natural enemies; (2) the differential contributions of natural enemy guilds to pest control, and the nature of their interactions across landscapes. We show that natural pest control of aphids increased up to six-fold from simple to complex landscapes. In the absence of pest control, aphid population growth was higher in complex than simple landscapes, but was reduced by natural enemies to similar growth rates across all landscapes. The effects of enemy guilds were landscape-dependent. Particularly in complex landscapes, total pest control was supplied by the combined contribution of flying insects and ground-dwellers. Birds had little overall impact on aphid control. Despite evidence for intraguild predation of flying insects by ground-dwellers and birds, the overall effect of enemy guilds on aphid control was complementary. Understanding pest control services at large spatial scales is critical to increase the success of ecological intensification schemes. Our results suggest that, where aphids are the main pest of concern, interactions between natural enemies are largely complementary and lead to a strongly positive effect of landscape complexity on pest control. Increasing the availability of seminatural habitats in agricultural landscapes may thus benefit not only natural enemies, but also the effectiveness of a…
format: application/pdf
format: text/html
creator: Emily A. Martin
creator: Björn Reineking
creator: Bumsuk Seo
creator: Ingolf Steffan-Dewenter
subject: Agricultural Science
subject: Biodiversity
subject: Ecology
subject: Natural Resource Management
description: doi:10.7717/peerj.1095
publisher: PeerJ Inc.
rights: © 2015 Martin et al.
abstract: Aphids are a major concern in agricultural crops worldwide, and control by natural enemies is an essential component of the ecological intensification of agriculture. Although the complexity of agricultural landscapes is known to influence natural enemies of pests, few studies have measured the degree of pest control by different enemy guilds across gradients in landscape complexity. Here, we use multiple natural-enemy exclosures replicated in 18 fields across a gradient in landscape complexity to investigate (1) the strength of natural pest control across landscapes, measured as the difference between pest pressure in the presence and in the absence of natural enemies; (2) the differential contributions of natural enemy guilds to pest control, and the nature of their interactions across landscapes. We show that natural pest control of aphids increased up to six-fold from simple to complex landscapes. In the absence of pest control, aphid population growth was higher in complex than simple landscapes, but was reduced by natural enemies to similar growth rates across all landscapes. The effects of enemy guilds were landscape-dependent. Particularly in complex landscapes, total pest control was supplied by the combined contribution of flying insects and ground-dwellers. Birds had little overall impact on aphid control. Despite evidence for intraguild predation of flying insects by ground-dwellers and birds, the overall effect of enemy guilds on aphid control was complementary. Understanding pest control services at large spatial scales is critical to increase the success of ecological intensification schemes. Our results suggest that, where aphids are the main pest of concern, interactions between natural enemies are largely complementary and lead to a strongly positive effect of landscape complexity on pest control. Increasing the availability of seminatural habitats in agricultural landscapes may thus benefit not only natural enemies, but also the effectiveness of a…
bibliographic citation: Martin et al. (2015) Pest control of aphids depends on landscape complexity and natural enemy interactions. PeerJ 3:e1095 https://doi.org/10.7717/peerj.1095
date submitted: 2015-04-15
date accepted: 2015-06-18
issued: 2015-07-16
is part of: PeerJ
license: http://creativecommons.org/licenses/by/4.0/
author list: Agent
  family name: Martin
  given name: Emily A.
author list: Agent
  family name: Reineking
  given name: Björn
author list: Agent
  family name: Seo
  given name: Bumsuk
author list: Agent
  family name: Steffan-Dewenter
  given name: Ingolf
doi: 10.7717/peerj.1095
volume: 3
issn: 2167-8359
publication name: PeerJ
publication date: 2015-07-16
copyright: © 2015 Martin et al.
attribution name: Martin et al.

Constant illumination reduces circulating melatonin and impairs immune function in the cricket Teleogryllus commodus
type: item
type: AcademicArticle
description: Exposure to constant light has a range of negative effects on behaviour and physiology, including reduced immune function in both vertebrates and invertebrates. It is proposed that the associated suppression of melatonin (a ubiquitous hormone and powerful antioxidant) in response to the presence of light at night could be an underlying mechanistic link driving the changes to immune function. Here, we investigated the relationship between constant illumination, melatonin and immune function, using a model invertebrate species, the Australian black field cricket, Teleogryllus commodus. Crickets were reared under either a 12 h light: 12 h dark regimen or a constant 24 h light regimen. Circulating melatonin concentration and immune function (haemocyte concentration, lytic activity and phenoloxidase (PO) activity) were assessed in individual adult crickets through the analysis of haemolymph. Constant illumination reduced melatonin and had a negative impact on haemocyte concentrations and lytic activity, but its effect on PO activity was less apparent. Our data provide the first evidence, to our knowledge, of a link between exposure to constant illumination and variation in haemocyte concentration in an invertebrate model, while also highlighting the potential complexity of the immune response following exposure to constant illumination. This study provides insight into the possible negative effect of artificial night-time lighting on the physiology of invertebrates, but whether lower and potentially more ecologically relevant levels of light at night produce comparable results, as has been reported in several vertebrate taxa, remains to be tested.
format: application/pdf
format: text/html
creator: Joanna Durrant
creator: Ellie B. Michaelides
creator: Thusitha Rupasinghe
creator: Dedreia Tull
creator: Mark P. Green
creator: Therésa M. Jones
subject: Entomology
subject: Environmental Impacts
subject: Environmental Sciences
subject: Zoology
description: doi:10.7717/peerj.1075
publisher: PeerJ Inc.
rights: © 2015 Durrant et al.
abstract: Exposure to constant light has a range of negative effects on behaviour and physiology, including reduced immune function in both vertebrates and invertebrates. It is proposed that the associated suppression of melatonin (a ubiquitous hormone and powerful antioxidant) in response to the presence of light at night could be an underlying mechanistic link driving the changes to immune function. Here, we investigated the relationship between constant illumination, melatonin and immune function, using a model invertebrate species, the Australian black field cricket, Teleogryllus commodus. Crickets were reared under either a 12 h light: 12 h dark regimen or a constant 24 h light regimen. Circulating melatonin concentration and immune function (haemocyte concentration, lytic activity and phenoloxidase (PO) activity) were assessed in individual adult crickets through the analysis of haemolymph. Constant illumination reduced melatonin and had a negative impact on haemocyte concentrations and lytic activity, but its effect on PO activity was less apparent. Our data provide the first evidence, to our knowledge, of a link between exposure to constant illumination and variation in haemocyte concentration in an invertebrate model, while also highlighting the potential complexity of the immune response following exposure to constant illumination. This study provides insight into the possible negative effect of artificial night-time lighting on the physiology of invertebrates, but whether lower and potentially more ecologically relevant levels of light at night produce comparable results, as has been reported in several vertebrate taxa, remains to be tested.
bibliographic citation: Durrant et al. (2015) Constant illumination reduces circulating melatonin and impairs immune function in the cricket Teleogryllus commodus. PeerJ 3:e1075 https://doi.org/10.7717/peerj.1075
date submitted: 2015-01-08
date accepted: 2015-06-12
issued: 2015-07-16
is part of: PeerJ
license: http://creativecommons.org/licenses/by/4.0/
author list: Agent
  family name: Durrant
  given name: Joanna
author list: Agent
  family name: Michaelides
  given name: Ellie B.
author list: Agent
  family name: Rupasinghe
  given name: Thusitha
author list: Agent
  family name: Tull
  given name: Dedreia
author list: Agent
  family name: Green
  given name: Mark P.
author list: Agent
  family name: Jones
  given name: Therésa M.
doi: 10.7717/peerj.1075
volume: 3
issn: 2167-8359
publication name: PeerJ
publication date: 2015-07-16
copyright: © 2015 Durrant et al.
attribution name: Durrant et al.

Photos provide information on age, but not kinship, of Andean bear
type: item
type: AcademicArticle
description: Using photos of captive Andean bears of known age and pedigree, and photos of wild Andean bear cubs <6 months old, we evaluated the degree to which visual information may be used to estimate bears’ ages and assess their kinship. We demonstrate that the ages of Andean bear cubs ≤6 months old may be estimated from their size relative to their mothers with an average error of <0.01 ± 13.2 days (SD; n = 14), and that ages of adults ≥10 years old may be estimated from the proportion of their nose that is pink with an average error of <0.01 ± 3.5 years (n = 41). We also show that similarity among the bears’ natural markings, as perceived by humans, is not associated with pedigree kinship among the bears (R2 < 0.001, N = 1,043, p = 0.499). Thus, researchers may use photos of wild Andean bears to estimate the ages of young cubs and older adults, but not to infer their kinship. Given that camera trap photos are one of the most readily available sources of information on large cryptic mammals, we suggest that similar methods be tested for use in other poorly understood species.
format: application/pdf
format: text/html
creator: Russell C. Van Horn
creator: Becky Zug
creator: Robyn D. Appleton
creator: Ximena Velez-Liendo
creator: Susanna Paisley
creator: Corrin LaCombe
subject: Animal Behavior
subject: Conservation Biology
subject: Ecology
subject: Zoology
description: doi:10.7717/peerj.1042
publisher: PeerJ Inc.
rights: © 2015 Van Horn et al.
abstract: Using photos of captive Andean bears of known age and pedigree, and photos of wild Andean bear cubs <6 months old, we evaluated the degree to which visual information may be used to estimate bears’ ages and assess their kinship. We demonstrate that the ages of Andean bear cubs ≤6 months old may be estimated from their size relative to their mothers with an average error of <0.01 ± 13.2 days (SD; n = 14), and that ages of adults ≥10 years old may be estimated from the proportion of their nose that is pink with an average error of <0.01 ± 3.5 years (n = 41). We also show that similarity among the bears’ natural markings, as perceived by humans, is not associated with pedigree kinship among the bears (R2 < 0.001, N = 1,043, p = 0.499). Thus, researchers may use photos of wild Andean bears to estimate the ages of young cubs and older adults, but not to infer their kinship. Given that camera trap photos are one of the most readily available sources of information on large cryptic mammals, we suggest that similar methods be tested for use in other poorly understood species.
bibliographic citation: Van Horn et al. (2015) Photos provide information on age, but not kinship, of Andean bear. PeerJ 3:e1042 https://doi.org/10.7717/peerj.1042
date submitted: 2015-04-02
date accepted: 2015-05-31
issued: 2015-07-16
is part of: PeerJ
license: http://creativecommons.org/licenses/by/4.0/
author list: Agent
  family name: Van Horn
  given name: Russell C.
author list: Agent
  family name: Zug
  given name: Becky
author list: Agent
  family name: Appleton
  given name: Robyn D.
author list: Agent
  family name: Velez-Liendo
  given name: Ximena
author list: Agent
  family name: Paisley
  given name: Susanna
author list: Agent
  family name: LaCombe
  given name: Corrin
doi: 10.7717/peerj.1042
volume: 3
issn: 2167-8359
publication name: PeerJ
publication date: 2015-07-16
copyright: © 2015 Van Horn et al.
attribution name: Van Horn et al.

Influence of a hyperlipidic diet on the composition of the non-membrane lipid pool of red blood cells of male and female rats
type: item
type: AcademicArticle
description: Background and objectives. Red blood cells (RBC) are continuously exposed to oxidative agents, affecting their membrane lipid function. However, the amount of lipid in RBCs is higher than the lipids of the cell membrane, and includes triacylglycerols, which are no membrane components. We assumed that the extra lipids originated from lipoproteins attached to the cell surface, and we intended to analyse whether the size and composition of this lipid pool were affected by sex or diet. Experimental design. Adult male and female Wistar rats were fed control or cafeteria diets. Packed blood cells and plasma lipids were extracted and analysed for fatty acids by methylation and GC-MS, taking care of not extracting membrane lipids. Results. The absence of ω3-PUFA in RBC extracts (but not in plasma) suggest that the lipids extracted were essentially those in the postulated lipid surface pool and not those in cell membrane. In cells’ extracts, there was a marked depletion of PUFA (and, in general, of insaturation). Fatty acid patterns were similar for all groups studied, with limited effects of sex and no effects of diet in RBC (but not in plasma) fatty acids. Presence of trans fatty acids was small but higher in RBC lipids, and could not be justified by dietary sources. Conclusions. The presence of a small layer of lipid on the RBC surface may limit oxidative damage to the cell outer structures, and help explain its role in the transport of lipophilic compounds. However, there may be other, so far uncovered, additional functions for this lipid pool.
format: application/pdf
format: text/html
creator: Xavier Remesar
creator: Arantxa Antelo
creator: Clàudia Llivina
creator: Emma Albà
creator: Lourdes Berdié
creator: Silvia Agnelli
creator: Sofía Arriarán
creator: José Antonio Fernández-López
creator: Marià Alemany
subject: Biochemistry
subject: Diabetes and Endocrinology
subject: Hematology
subject: Nutrition
subject: Metabolic Sciences
description: doi:10.7717/peerj.1083
publisher: PeerJ Inc.
rights: © 2015 Remesar et al.
abstract: Background and objectives. Red blood cells (RBC) are continuously exposed to oxidative agents, affecting their membrane lipid function. However, the amount of lipid in RBCs is higher than the lipids of the cell membrane, and includes triacylglycerols, which are no membrane components. We assumed that the extra lipids originated from lipoproteins attached to the cell surface, and we intended to analyse whether the size and composition of this lipid pool were affected by sex or diet. Experimental design. Adult male and female Wistar rats were fed control or cafeteria diets. Packed blood cells and plasma lipids were extracted and analysed for fatty acids by methylation and GC-MS, taking care of not extracting membrane lipids. Results. The absence of ω3-PUFA in RBC extracts (but not in plasma) suggest that the lipids extracted were essentially those in the postulated lipid surface pool and not those in cell membrane. In cells’ extracts, there was a marked depletion of PUFA (and, in general, of insaturation). Fatty acid patterns were similar for all groups studied, with limited effects of sex and no effects of diet in RBC (but not in plasma) fatty acids. Presence of trans fatty acids was small but higher in RBC lipids, and could not be justified by dietary sources. Conclusions. The presence of a small layer of lipid on the RBC surface may limit oxidative damage to the cell outer structures, and help explain its role in the transport of lipophilic compounds. However, there may be other, so far uncovered, additional functions for this lipid pool.
bibliographic citation: Remesar et al. (2015) Influence of a hyperlipidic diet on the composition of the non-membrane lipid pool of red blood cells of male and female rats. PeerJ 3:e1083 https://doi.org/10.7717/peerj.1083
date submitted: 2015-05-19
date accepted: 2015-06-16
issued: 2015-07-14
is part of: PeerJ
license: http://creativecommons.org/licenses/by/4.0/
author list: Agent
  family name: Remesar
  given name: Xavier
author list: Agent
  family name: Antelo
  given name: Arantxa
author list: Agent
  family name: Llivina
  given name: Clàudia
author list: Agent
  family name: Albà
  given name: Emma
author list: Agent
  family name: Berdié
  given name: Lourdes
author list: Agent
  family name: Agnelli
  given name: Silvia
author list: Agent
  family name: Arriarán
  given name: Sofía
author list: Agent
  family name: Fernández-López
  given name: José Antonio
author list: Agent
  family name: Alemany
  given name: Marià
doi: 10.7717/peerj.1083
volume: 3
issn: 2167-8359
publication name: PeerJ
publication date: 2015-07-14
copyright: © 2015 Remesar et al.
attribution name: Remesar et al.

Urinary microRNA can be concentrated, dried on membranes and stored at room temperature in vacuum bags
type: item
type: AcademicArticle
description: Urine accumulates traces of changes that occur in the body and can potentially serve as a better biomarker source. Urinary microRNA is a promising class of non-invasive disease biomarkers. However, long-term frozen human urine samples are not a good source for the extraction of urinary microRNA. In this paper, we demonstrate that urinary microRNA can be concentrated, dried on membranes and stored in vacuum bags at room temperature for several months. The amount of total RNA on the membranes after storage at room temperature for three months was unchanged. The levels of miR-16 and miR-21 exhibited no significant differences (P = 0.564, 0.386). This simple and economical method makes the large-scale storage of clinical samples of urinary microRNA or other nucleic acids possible.
format: application/pdf
format: text/html
creator: Fanshuang Zhang
creator: Xiaoyu Cheng
creator: Yuan Yuan
creator: Jianqiang Wu
creator: Youhe Gao
subject: Biochemistry
subject: Molecular Biology
subject: Urology
description: doi:10.7717/peerj.1082
publisher: PeerJ Inc.
rights: © 2015 Zhang et al.
abstract: Urine accumulates traces of changes that occur in the body and can potentially serve as a better biomarker source. Urinary microRNA is a promising class of non-invasive disease biomarkers. However, long-term frozen human urine samples are not a good source for the extraction of urinary microRNA. In this paper, we demonstrate that urinary microRNA can be concentrated, dried on membranes and stored in vacuum bags at room temperature for several months. The amount of total RNA on the membranes after storage at room temperature for three months was unchanged. The levels of miR-16 and miR-21 exhibited no significant differences (P = 0.564, 0.386). This simple and economical method makes the large-scale storage of clinical samples of urinary microRNA or other nucleic acids possible.
bibliographic citation: Zhang et al. (2015) Urinary microRNA can be concentrated, dried on membranes and stored at room temperature in vacuum bags. PeerJ 3:e1082 https://doi.org/10.7717/peerj.1082
date submitted: 2015-02-28
date accepted: 2015-06-15
issued: 2015-07-14
is part of: PeerJ
license: http://creativecommons.org/licenses/by/4.0/
author list: Agent
  family name: Zhang
  given name: Fanshuang
author list: Agent
  family name: Cheng
  given name: Xiaoyu
author list: Agent
  family name: Yuan
  given name: Yuan
author list: Agent
  family name: Wu
  given name: Jianqiang
author list: Agent
  family name: Gao
  given name: Youhe
doi: 10.7717/peerj.1082
volume: 3
issn: 2167-8359
publication name: PeerJ
publication date: 2015-07-14
copyright: © 2015 Zhang et al.
attribution name: Zhang et al.

Using signals associated with safety in avoidance learning: computational model of sex differences
type: item
type: AcademicArticle
description: Avoidance behavior involves learning responses that prevent upcoming aversive events; these responses typically extinguish when the aversive events stop materializing. Stimuli that signal safety from aversive events can paradoxically inhibit extinction of avoidance behavior. In animals, males and females process safety signals differently. These differences help explain why women are more likely to be diagnosed with an anxiety disorder and exhibit differences in symptom presentation and course compared to men. In the current study, we extend an existing model of strain differences in avoidance behavior to simulate sex differences in rats. The model successfully replicates data showing that the omission of a signal associated with a period of safety can facilitate extinction in females, but not males, and makes novel predictions that this effect should depend on the duration of the period, the duration of the signal itself, and its occurrence within that period. Non-reinforced responses during the safe period were also found to be important in the expression of these patterns. The model also allowed us to explore underlying mechanisms for the observed sex effects, such as whether safety signals serve as occasion setters for aversive events, to determine why removing them can facilitate extinction of avoidance. The simulation results argue against this account, and instead suggest the signal may serve as a conditioned reinforcer of avoidance behavior.
format: application/pdf
format: text/html
creator: Milen L. Radell
creator: Kevin D. Beck
creator: Kevin C.H. Pang
creator: Catherine E. Myers
subject: Animal Behavior
subject: Computational Biology
subject: Neuroscience
subject: Psychiatry and Psychology
subject: Computational Science
description: doi:10.7717/peerj.1081
publisher: PeerJ Inc.
rights: © 2015
abstract: Avoidance behavior involves learning responses that prevent upcoming aversive events; these responses typically extinguish when the aversive events stop materializing. Stimuli that signal safety from aversive events can paradoxically inhibit extinction of avoidance behavior. In animals, males and females process safety signals differently. These differences help explain why women are more likely to be diagnosed with an anxiety disorder and exhibit differences in symptom presentation and course compared to men. In the current study, we extend an existing model of strain differences in avoidance behavior to simulate sex differences in rats. The model successfully replicates data showing that the omission of a signal associated with a period of safety can facilitate extinction in females, but not males, and makes novel predictions that this effect should depend on the duration of the period, the duration of the signal itself, and its occurrence within that period. Non-reinforced responses during the safe period were also found to be important in the expression of these patterns. The model also allowed us to explore underlying mechanisms for the observed sex effects, such as whether safety signals serve as occasion setters for aversive events, to determine why removing them can facilitate extinction of avoidance. The simulation results argue against this account, and instead suggest the signal may serve as a conditioned reinforcer of avoidance behavior.
bibliographic citation: Radell et al. (2015) Using signals associated with safety in avoidance learning: computational model of sex differences. PeerJ 3:e1081 https://doi.org/10.7717/peerj.1081
date submitted: 2015-03-04
date accepted: 2015-06-15
issued: 2015-07-14
is part of: PeerJ
license: http://creativecommons.org/publicdomain/zero/1.0/
author list: Agent
  family name: Radell
  given name: Milen L.
author list: Agent
  family name: Beck
  given name: Kevin D.
author list: Agent
  family name: Pang
  given name: Kevin C.H.
author list: Agent
  family name: Myers
  given name: Catherine E.
doi: 10.7717/peerj.1081
volume: 3
issn: 2167-8359
publication name: PeerJ
publication date: 2015-07-14

Allele specific expression in worker reproduction genes in the bumblebee Bombus terrestris
type: item
type: AcademicArticle
description: Methylation has previously been associated with allele specific expression in ants. Recently, we found methylation is important in worker reproduction in the bumblebee Bombus terrestris. Here we searched for allele specific expression in twelve genes associated with worker reproduction in bees. We found allele specific expression in Ecdysone 20 monooxygenase and IMP-L2-like. Although we were unable to confirm a genetic or epigenetic cause for this allele specific expression, the expression patterns of the two genes match those predicted for imprinted genes.
format: application/pdf
format: text/html
creator: Harindra E. Amarasinghe
creator: Bradley J. Toghill
creator: Despina Nathanael
creator: Eamonn B. Mallon
subject: Animal Behavior
subject: Entomology
subject: Evolutionary Studies
subject: Genetics
subject: Zoology
description: doi:10.7717/peerj.1079
publisher: PeerJ Inc.
rights: © 2015 Amarasinghe et al.
abstract: Methylation has previously been associated with allele specific expression in ants. Recently, we found methylation is important in worker reproduction in the bumblebee Bombus terrestris. Here we searched for allele specific expression in twelve genes associated with worker reproduction in bees. We found allele specific expression in Ecdysone 20 monooxygenase and IMP-L2-like. Although we were unable to confirm a genetic or epigenetic cause for this allele specific expression, the expression patterns of the two genes match those predicted for imprinted genes.
bibliographic citation: Amarasinghe et al. (2015) Allele specific expression in worker reproduction genes in the bumblebee Bombus terrestris. PeerJ 3:e1079 https://doi.org/10.7717/peerj.1079
date submitted: 2015-03-08
date accepted: 2015-06-14
issued: 2015-07-14
is part of: PeerJ
license: http://creativecommons.org/licenses/by/4.0/
author list: Agent
  family name: Amarasinghe
  given name: Harindra E.
author list: Agent
  family name: Toghill
  given name: Bradley J.
author list: Agent
  family name: Nathanael
  given name: Despina
author list: Agent
  family name: Mallon
  given name: Eamonn B.
doi: 10.7717/peerj.1079
volume: 3
issn: 2167-8359
publication name: PeerJ
publication date: 2015-07-14
copyright: © 2015 Amarasinghe et al.
attribution name: Amarasinghe et al.

PeerJ
type: Periodical
uri: PeerJ
issn: 2167-8359