bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fitness conflicts and the costs of sociality in communal egg layers: a theoretical model and empirical tests
Authors: Loeb M. L. G. , Zink A. G. 
Published: December 2005

Abstract
Individuals within complex social groups often experience reduced reproduction owing to coercive or suppressive actions of other group members. However, the nature of social and ecological environments that favour individual acceptance of such costs of sociality is not well understood. Taxa with short periods of direct social interaction, such as some communal egg layers, are interesting models for study of the cost of social interaction because opportunities to control reproduction of others are limited to brief periods of reproduction. To understand the conditions under which communal egg layers are in fitness conflict and thus likely to influence each other's reproduction, we develop an optimality model involving a brood guarding ‘host’ and a nonguarding disperser, or ‘egg dumper’. The model shows that when, where intermediate-sized broods have highest survival, lifetime inclusive fitnesses of hosts and dumpers are often optimized with different numbers of dumped eggs. We hypothesize that resolution of this conflict may involve attempts by one party to manipulate the other's reproduction. To test model predictions we used a lace bug (Heteroptera: Tingidae) that shows both hosts and egg dumpers as well as increased offspring survival in response to communal egg laying. We found that egg-dumping lace bugs oviposit a number of eggs that very closely matches predicted fitness optimum for hosts rather than predicted optimum of dumpers. This result suggests that dumpers pay a social cost for communal egg laying, a cost that may occur through host suppression of dumper reproduction. Although dumper allocation of eggs is thus sub-optimal for dumpers, previous models show that the decision to egg dump is nevertheless evolutionarily stable, possibly because hosts permit just enough dumper oviposition to encourage commitment to the behaviour.
Do mothers producing large offspring have to sacrifice fecundity?
Authors: Fischer K. , Bot A. N. M. , Brakefield P. M. , Zwaan Bas J. 
Published: December 2005

Abstract
We artificially selected on egg size in a butterfly to study the consequences for fecundity, reproductive effort and offspring fitness. Correlated responses in either pupal mass, larval or pupal development time were virtually absent. Offspring size was positively related to fitness, but only partly traded off against fecundity. Rather, total reproductive effort (measured as fresh mass), egg water content and the decline of egg size with female age increased in the large-egg selected lines compared to either small-egg or control lines. Accounting for these effects showed that reproductive investment (in dry mass) was in fact similar across lines. Such mechanisms may enable increased investment in (early) offspring without a reduction in their number, revealing a much more complex picture than a simple trade-off between offspring size and number. Substantial variation among replicates suggests that there are different underlying mechanisms for change, rather than any single, unitary pathway.
Asymmetric gene flow and constraints on adaptation caused by sex ratio distorters
Authors: Telschow A. , Engelstädter J. , Yamamura N. , Hammerstein P. , Hurst G.D.D. 
Published: December 2005

Abstract
Asymmetric gene flow is generally believed to oppose natural selection and potentially impede adaptation. Whilst the cause of asymmetric gene flow has been seen largely in terms of variation in population density over space, asymmetric gene flow can also result from varying sex ratios across subpopulations with similar population sizes. We model the process of adaptation in a scenario in which two adjacent subpopulations have different sex ratios, associated with different levels of infection with maternally inherited endosymbionts that selectively kill male hosts. Two models are analyzed in detail. First, we consider one host locus with two alleles, each of which possesses a selective advantage in one of the subpopulations. We found that local adaptation can strongly be impeded in the subpopulation with the more female biased population sex ratio. Second, we analyze host alleles that provide resistance against the male-killing (MK) endosymbionts and show that asymmetric gene flow can prevent the spread of such alleles under certain conditions. These results might have important implications for the coevolution of MK bacteria and their hosts.
The costs and benefits in an unusual symbiosis: experimental evidence that bitterling fish (Rhodeus sericeus) are parasites of unionid mussels in Europe
Authors: Reichard M. , Ondračková M. , Przybylski M. , Liu H. , Smith C. 
Published: December 2005

Abstract
Interspecific symbiotic relationships involve a complex network of interactions, and understanding their outcome requires quantification of the costs and benefits to both partners. We experimentally investigated the costs and benefits in the relationship between European bitterling fish (Rhodeus sericeus) and freshwater mussels that are used by R. sericeus for oviposition. This relationship has hitherto been thought mutualistic, on the premise that R. sericeus use mussels as foster parents of their embryos while mussels use R. sericeus as hosts for their larvae. We demonstrate that R. sericeus is a parasite of European mussels, because it (i) avoids the cost of infection by mussel larvae and (ii) imposes a direct cost on mussels. Our experiments also indicate a potential coevolutionary arms race between bitterling fishes and their mussel hosts; the outcome of this relationship may differ between Asia, the centre of distribution of bitterling fishes, and Europe where they have recently invaded.
Glacial refugia and the phylogeography of Steller's sea lion (Eumatopias jubatus) in the North Pacific
Authors: Harlin-cognato A. , Bickham J. W. , Loughlin T. R. , Honeycutt R. L. 
Published: December 2005

Abstract
Mitochondrial DNA sequence data were used to examine the phylogeographic history of Steller's sea lions (Eumetopias jubatus) in relation to the presence of Plio-Pleistocene insular refugia. Cytochrome b and control region sequences from 336 Steller's sea lions reveal phylogenetic lineages associated with continental refugia south of the ice sheets in North America and Eurasia. Phylogenetic analysis suggests the genetic structure of E. jubatus is the result of Pleistocene glacial geology, which caused the elimination and subsequent reappearance of suitable rookery habitat during glacial and interglacial periods. The cyclic nature of geological change produced a series of independent population expansions, contractions and isolations that had analogous results on Steller's sea lions and other marine and terrestrial species. Our data show evidence of four glacial refugia in which populations of Steller's sea lions diverged. These events occurred from approximately 60 000 to 180 000 years BP and thus preceded the last glacial maximum.
Sediment greenhouse gases (methane and carbon dioxide) in the Lobo‐Broa Reservoir, São Paulo State, Brazil: Concentrations and diffuse emission fluxes for carbon budget considerations
Authors: Abe Donato S. , Adams Donald D. , Galli Corina V. Sidagis , Sikar Elizabeth , Tundisi José G. 
Published: December 2005

AbstractCarbon gases (methane, CH4, and carbon dioxide, CO2) were measured for the first time in sediments of the Lobo‐Broa Reservoir, near São Carlos in São Paulo State, Brazil. It is believed these are the first measurements of this kind in any of the many reservoirs located in Brazil. Even though the Lobo‐Broa Reservoir is classified as oligotrophic, the sediment gas concentrations were exceedingly high, ranging from 0.4–3 mmol L−1 for CH4 and 1–9 mmol L−1 for CO2. Both gases exceeded their in situ gas saturation values at these shallow water depths (7 m in central basin; 11 m at dam), resulting in numerous sediment bubbles. Organic matter was highly concentrated in the reservoir sediments, averaging 25.5% loss on ignition (LOI) (dam) to 26.9% LOI (central basin) for the 0–12 cm depth interval, with values as high as 29–30% LOI (12% organic carbon) in the surface 0–5 mm layer. The theoretical flux of dissolved pore water carbon gases to the sediment–water interface (SWI) averaged 3.4 mmol L−1 m−2 day−1 CH4 and 7.3 mmol L−1 m−2 day−1 CO2 for the surface 0–10 mm. From gas emission measurements at the water surface, it was calculated that 90% of CH4 is consumed either at the SWI or in the water column, resulting in a loss of 0.31 mmol L−1 m−2 day−1 of CH4 to the atmosphere. However, only 20% of the total CO2 gas transported across the water–atmosphere interface (36.3 mmol L−1 m−2 day−1, or 1600 mg CO2 m−2 day−1) was produced in the sediments. The remaining 80% of CO2 probably comes from other carbon sources. With CH4 oxidation in the aerobic water column, close to 30% of the carbon gas flux to the atmosphere could be accounted for by gas production of CO2 and CH4 in the sediments and their diffuse transport to the water column.
The role of prefrontal cortex in object‐in‐place learning in monkeys
Authors: Browning Philip G. F. , Easton Alexander , Buckley Mark J. , Gaffan David 
Published: December 2005

AbstractPrevious ablation studies in monkeys suggest that prefrontal cortex is involved in a wide range of learning and memory tasks. However, monkeys with crossed unilateral lesions of frontal and temporal cortex are unimpaired at concurrent object–reward association learning but are impaired at conditional learning and the implementation of memory‐based performance rules. We trained seven monkeys preoperatively on an associative learning task that required them to associate objects embedded in unique complex scenes with reward. Three monkeys then had crossed unilateral lesions of frontal and inferior temporal cortex and the remaining monkeys had bilateral prefrontal cortex ablation. Both groups were severely impaired postoperatively. These results show that both bilateral prefrontal cortex ablation and frontal–temporal disconnection impair associative learning for objects embedded in scenes. The results provide evidence that the function of frontal–temporal interactions in memory is not limited to conditional learning tasks and memory‐dependent performance rules. We propose that rapid object‐in‐place learning requires the interaction of frontal cortex with inferotemporal cortex because visual object and contextual information which is captured over multiple saccades must be processed as a unique complex event that is extended in time. The present results suggest a role for frontal–temporal interaction in the integration of visual information over time.
Late N‐methyl‐d‐aspartate receptor blockade rescues hippocampal neurons from excitotoxic stress and death after 4‐aminopyridine‐induced epilepsy
Authors: Ayala Gabriela X. , Tapia Ricardo 
Published: December 2005

AbstractThe intrahippocampal perfusion of 4‐aminopyridine (4‐AP) in the rat produces immediate seizures and delayed neuronal death, due to the overactivation of N‐methyl‐d‐aspartate (NMDA) receptors by endogenous glutamate released from nerve endings. With the same time course, 4‐AP also induces the expression of the cell stress marker heat shock protein 70 (HSP70) in the contralateral non‐damaged hippocampus. We have used this experimental model to study the mechanisms of the delayed neuronal stress and death. The NMDA receptor antagonist (+)‐5‐methyl‐10,11‐dihydro‐5H‐dibenzo(a,d)cyclohepten‐5,10‐imine maleate (MK‐801), administered intraperitoneally 30 or 60 but not 120 min after 4‐AP perfusion, when animals show intense electroencephalography epileptiform activity, prevented the delayed neurodegeneration whereas the seizures continued for about 3 h as in the control animals. With an identical time window, MK‐801 treatment also modified the pattern of HSP70 expression; the protein was expressed in the protected perfused hippocampus but no longer in the undamaged contralateral hippocampus. The possible role of Ca2+ in the delayed cell death and HSP70 expression was also studied by coperfusing the intracellular Ca2+ chelator 1,2‐bis(2‐aminophenoxy)ethane‐N,N,N′,N′‐tetra‐acetic acid tetrakis(acetoxymethyl ester) with 4‐AP. This treatment resulted in protective and HSP70 effects very similar to those of MK‐801. These results suggest that the seizures are not linked to neurodegeneration and that NMDA receptors need to be continuously overactivated by endogenous glutamate for at least 60 min in order to induce delayed neuronal stress and death, which are dependent on Ca2+ entry through the NMDA receptor channel.
A postnatal switch in GABAergic control of spinal cutaneous reflexes
Authors: Hathway Gareth , Harrop Emily , Baccei Mark , Walker Suellen , Moss Andrew , Fitzgerald Maria 
Published: December 2005

AbstractGABAergic signalling exerts powerful inhibitory control over spinal tactile and nociceptive processing, but during development GABA can be depolarizing and the functional consequences of this upon neonatal pain processing is unknown. Here we show a postnatal switch in tonic GABAA receptor (GABAAR) modulation of cutaneous tactile and nociceptive reflexes from excitation to inhibition, but only in the intact spinal cord. Neonatal and 21‐day‐old (P21) rats were intrathecally treated with one of the GABAAR antagonists bicuculline and gabazine, with both compounds dose‐dependently decreasing hindpaw mechanical and thermal withdrawal thresholds in P21 rats but increasing them in P3 neonates. Intrathecal gabazine also produced an increase in the cutaneous evoked electromyography (EMG) response of the biceps femoris in P21 rates but lowering the response in neonates. Injections of 3H‐gabazine in the L4–L5 region at P3 confirmed that gabazine binding was restricted to the lumbar spinal cord. Spinalization of P3 neonates at the upper thoracic level prior to drug application reversed the behavioural and EMG responses to GABA antagonists so that they resembled those of P21 rats. The effects of spinalization were consistent with gabazine facilitation of ventral root potentials observed in isolated neonatal spinal cord. These data show a marked postnatal developmental switch in GABAergic control of neonatal nociception that is mediated by supraspinal structures and illustrate the importance of studying developmental circuits in the intact nervous system.
ATP activates both receptor and sustentacular supporting cells in the olfactory epithelium of Xenopus laevis tadpoles
Authors: Czesnik Dirk , Kuduz Josko , Schild Detlev , Manzini Ivan 
Published: December 2005

AbstractNucleotides and amino acids are acknowledged categories of water‐borne olfactory stimuli. In previous studies it has been shown that larvae of Xenopus laevis are able to sense amino acids. Here we report on the effect of ATP in the olfactory epithelium (OE) of Xenopus laevis tadpoles. First, ATP activates a subpopulation of cells in the OE. The ATP‐sensitive subset of cells is almost perfectly disjoint from the subset of amino acid‐activated cells. Both responses are not mediated by the well‐described cAMP transduction pathway as the two subpopulations of cells do not overlap with a third, forskolin‐activated subpopulation. We further show that, in contrast to amino acids, which act exclusively as olfactory stimuli, ATP appears to feature a second role. Surprisingly it activated a large number of sustentacular supporting cells (SCs) and, to a much lower extent, olfactory receptor neurons. The cells of the amino acid‐ and ATP‐responding subsets featured differences in shape, size and position in the OE. The latencies to activation upon stimulus application differed markedly in these subsets. To obtain these results two technical points were important. We used a novel dextran‐tetramethylrhodamine‐backfilled slice preparation of the OE and we found out that an antibody to calnexin, a known molecular chaperone, also labels SCs. Our findings thus show a strong effect of ATP in the OE and we discuss some of the possible physiological functions of nucleotides in the OE.
Quantifying the roles of immigration and chance in shaping prokaryote community structure
Authors: Sloan William T. , Lunn Mary , Woodcock Stephen , Head Ian M. , Nee Sean , Curtis Thomas P. 
Published: December 2005

SummaryNaturally occurring populations of bacteria and archaea are vital to life on the earth and are of enormous practical significance in medicine, engineering and agriculture. However, the rules governing the formation of such communities are still poorly understood, and there is a need for a usable mathematical description of this process. Typically, microbial community structure is thought to be shaped mainly by deterministic factors such as competition and niche differentiation. Here we show, for a wide range of prokaryotic communities, that the relative abundance and frequency with which different taxa are observed in samples can be explained by a neutral community model (NCM). The NCM, which is a stochastic, birth–death immigration process, does not explicitly represent the deterministic factors and therefore cannot be a complete or literal description of community assembly. However, its success suggests that chance and immigration are important forces in shaping the patterns seen in prokaryotic communities.
Expression of calcineurin and its interacting proteins in epileptic fowl
Authors: Lakshmikuttyamma Ashakumary , Selvakumar Ponniah , Charavaryamath Chandrashekhar , Singh Baljit , Tuchek John , Sharma Rajendra K. 
Published: December 2005

AbstractCalcineurin (CaN), a Ca2+–calmodulin (CaM)‐dependent protein phosphatase, is important for Ca2+‐mediated signal transduction. The main objective of this study was to examine the potential role of CaN in epileptic brain and its involvement in neuronal apoptosis. We investigated CaN expression and its interaction with various signaling molecules in normal, carrier and epileptic brain tissues of chicken. Our results revealed higher Ca2+–CaM‐dependent phosphatase activity of CaN and a correspondingly strong immunoreactive band of CaN A in epileptic and carrier brain samples compared with normal brain. Furthermore, immunohistochemical analysis showed a higher level of expression of CaN in epileptic brain tissue. However, the intensity of immunoreactivity was less in carrier than epileptic brain. We observed that the interaction of CaN with m‐calpain and µ‐calpain was strong in carrier and epileptic chickens compared with that in normal birds. In addition, the interaction of CaN with Bcl‐2, caspase‐3 and p53 was greater in carrier and epileptic fowl than in normal chickens. The greater interaction of CaN with various apoptotic factors in epileptic chickens adds to our understanding of the mechanism of CaN signaling in neuronal apoptosis.
Decreased GTP‐stimulated adenylyl cyclase activity in HPRT‐deficient human and mouse fibroblast and rat B103 neuroblastoma cell membranes
Authors: Pinto Cibele S. , Seifert Roland 
Published: December 2005

AbstractDefect of the purine salvage enzyme, hypoxanthine phosphoribosyl transferase (HPRT), results in Lesch–Nyhan disease (LND). It is unknown how the metabolic defect translates into the severe neuropsychiatric phenotype characterized by self‐injurious behavior, dystonia and mental retardation. There are abnormalities in GTP, UTP and CTP concentrations in HPRT‐deficient cells. Moreover, GTP, ITP, XTP, UTP and CTP differentially support Gs‐protein‐mediated adenylyl cyclase (AC) activation. Based on these findings we hypothesized that abnormal AC regulation may constitute the missing link between HPRT deficiency and the neuropsychiatric symptoms in LND. To test this hypothesis, we studied AC activity in membranes from primary human skin and immortalized mouse skin fibroblasts, mouse Neuro‐2a neuroblastoma cells and rat B103 neuroblastoma cells. In B103 control membranes, GTP, ITP, XTP and UTP exhibited profound stimulatory effects on basal AC activity that approached the effects of hydrolysis‐resistant nucleotide analogs. In HPRT–membranes, the stimulatory effects of GTP, ITP, XTP and UTP were strongly reduced. Similarly, in human and mouse skin fibroblast membranes we also observed a decrease in GTP‐stimulated AC activity in HPRT‐deficient cells compared with the respective controls. In mouse Neuro‐2a neuroblastoma membranes, AC activity in the presence of GTP was below the detection limit of the assay. We discuss several possibilities to explain the abnormalities in AC regulation in HPRT deficiency that encompass various species and cell types.
Type A monoamine oxidase is the target of an endogenous dopaminergic neurotoxin, N‐methyl(R)salsolinol, leading to apoptosis in SH‐SY5Y cells
Authors: Yi Hong , Akao Yukihiro , Maruyama Wakako , Chen Kavin , Shih Jean , Naoi Makoto 
Published: December 2005

AbstractMitochondrial monoamine oxidase (MAO) has been considered to be involved in neuronal degeneration either by increased oxidative stress or protection with the inhibitors of type B MAO (MAO‐B). In this paper, the role of type A MAO (MAO‐A) in apoptosis was studied using human neuroblastoma SH‐SY5Y cells, where only MAO‐A is expressed. An endogenous dopaminergic neurotoxin, N‐methyl(R)salsolinol, an MAO‐A inhibitor, reduced membrane potential, ΔΨm, in isolated mitochondria, and induced apoptosis in the cells, which 5‐hydroxytryptamine, an MAO‐A substrate, prevented. In contrast, β‐phenylethylamine, an MAO‐B substrate, did not suppress the ΔΨm decline by N‐methyl(R)salsolinol. The binding of N‐methyl(R)salsolinol to mitochondria was inhibited by clorgyline, a MOA‐A inhibitor, but not by (–)deprenyl, an MAO‐B inhibitor. RNA interference targeting MAO‐A significantly reduced the binding of N‐methyl(R)salsolinol with simultaneous reduction in the MAO activity. To examine the intervention of MAO‐B in the apoptotic process, human MAO‐B was transfected to SH‐SY5Y cells, but the sensitivity to N‐methyl(R)salsolinol was not affected, even although the activity and protein of MAO increased markedly. These results demonstrate a novel function of MAO‐A in the binding of neurotoxins and the induction of apoptosis, which may account for neuronal cell death in neurodegenerative disorders, including Parkinson's disease.