bluuebunny/crossref_metadata_2025_split huggingface dataset:
High recombination frequency creates genotypic diversity in colonies of the leaf-cutting ant Acromyrmex echinatior
Authors: Sirviö A. , Gadau J. , Rueppell O. , Lamatsch D. , Boomsma J. J. , Pamilo P. , Page R. E. 
Published: May 2006

Abstract
Honeybees are known to have genetically diverse colonies because queens mate with many males and the recombination rate is extremely high. Genetic diversity among social insect workers has been hypothesized to improve general performance of large and complex colonies, but this idea has not been tested in other social insects. Here, we present a linkage map and an estimate of the recombination rate for Acromyrmex echinatior, a leaf-cutting ant that resembles the honeybee in having multiple mating of queens and colonies of approximately the same size. A map of 145 AFLP markers in 22 linkage groups yielded a total recombinational size of 2076 cM and an inferred recombination rate of 161 kb cM−1 (or 6.2 cM Mb−1). This estimate is lower than in the honeybee but, as far as the mapping criteria can be compared, higher than in any other insect mapped so far. Earlier studies on A. echinatior have demonstrated that variation in division of labour and pathogen resistance has a genetic component and that genotypic diversity among workers may thus give colonies of this leaf-cutting ant a functional advantage. The present result is therefore consistent with the hypothesis that complex social life can select for an increased recombination rate through effects on genotypic diversity and colony performance.
Frequency-dependent predation and maintenance of prey polymorphism
Authors: Merilaita S. 
Published: May 2006

Abstract
In positive frequency-dependent predation, predation risk of an individual prey correlates positively with the frequency of that prey type. In a number of small-scale experiments individual predators have shown frequency-dependent behaviour, often leading to the conclusion that a population of such predators could maintain prey polymorphism. Using simulations, I studied the dynamics of frequency-dependent predation and prey polymorphism. The model suggests that persistence of prey polymorphism decreases with increasing number of predators that show frequency-dependent behaviour, questioning conclusions about polymorphism based on experiments with few predators. In addition, prey population size, prey crypsis, difference in crypsis between prey morphs and the way the behaviour was adjusted affected the persistence of polymorphism. Under some circumstances prey population remained polymorphic for a shorter time under frequency-dependent than under frequency-independent predation. This suggests that although positive frequency-dependent predator behaviour may maintain prey polymorphism, it is not a sufficient condition for persistent prey polymorphism.
Song similarity predicts hybridization in flycatchers
Authors: Qvarnström A. , Haavie J. , Sæther S. A. , Eriksson D. , Pärt T. 
Published: May 2006

Abstract
Given that population divergence in sexual signals is an important prerequisite for reproductive isolation, a key prediction is that cases of signal convergence should lead to hybridization. However, empirical studies that quantitatively demonstrate links between phenotypic characters of individuals and their likelihood to hybridize are rare. Here we show that song convergence between sympatric pied (Ficedula hypoleuca) and collared flycatchers (F. albicollis) influence social and sexual interactions between the two species. In sympatry, the majority of male pied flycatchers (65%) include various parts of collared flycatcher song in their song repertoire (but not vice versa). Playback experiments on male interactions demonstrate that male collared flycatchers respond similarly to this ‘mixed’ song as to conspecific song. Long-term data on pairing patterns show that males singing a converged song attract females of the other species: female collared flycatchers only pair with male pied flycatchers if the males sing the mixed song type. From the perspective of a male pied flycatcher, singing a mixed song type is associated with 30% likelihood of hybridization. This result, combined with our estimates of the frequency of mixed singers, accurately predicts the observed occurrence of hybridization among male pied flycatchers in our study populations (20.45% of 484 pairs; predicted 19.5%). Our results support the suggestion that song functions as the most important prezygotic isolation mechanism in many birds.
Relationship between thiamine concentration and fermentation patterns in the rumen fluid of dairy cows fed with graded concentrate levels
Authors: Tafaj M. , Schollenberger M. , Feofilowa J. , Zebeli Q. , Steingass H. , Drochner W. 
Published: May 2006

SummaryThe objective of this study was to investigate the relationship between the thiamine concentration and the fermentation patterns [pH, concentration of short‐chain fatty acids (SCFA)] in the free liquid (FRL) and particle‐associated liquid (PARL) of the rumen in dairy cows fed with graded concentrate levels in the diet. Four ruminally cannulated Holstein cows in mid lactation were fed [semi‐ad libitum, 18 kg dry matter (DM)/day] diets consisting of hay (H) and slowly degradable concentrate (C), offered in five different H:C ratios (% DM basis) in the following sequence: period 1, 30:70; period 2, 40:60; period 3, 50:50; period 4, 60:40 and period 5, 75:25. A negative quadratic relationship was observed between thiamine concentration in FRL and intake of dietary thiamine (R2 = 0.36), of concentrate (R2 = 0.38) and of digestible non‐fibre carbohydrates (R2 = 0.37). The thiamine concentration in PARL was higher (p ≤ 0.05) compared to FRL. The ruminal thiamine concentration correlated negatively to pH and positively to concentrations of SCFA and propionate in the rumen. R2 of these relationships varied markedly (0.002 and 0.77), depending on time after feeding and fluid digesta compartment. The higher R2 were observed at 8 and 11 h after the morning feeding for FRL (R2 0.46–0.71) and PARL (R2 0.41–0.77), respectively.
Bee pollen product supplementation to horses in training seems to improve feed intake: a pilot study
Authors: Turner K. K. , Nielsen B. D. , O'Connor C. I. , Burton J. L. 
Published: May 2006

SummaryThe objective of this study was to determine the efficacy of supplementation of Dynamic Trio 50/50, a bee pollen‐based product, to improve physical fitness, blood leukocyte profiles, and nutritional variables in exercised horses. Ten Arabian horses underwent a standardised exercise test (SET), then were pair‐matched by sex and fitness and randomly assigned to BP (receiving 118 g of Dynamic Trio 50/50 daily) or CO (receiving 73 g of a placebo) for a period of 42 days. A total collection was conducted from days 18 to 21 on six geldings to determine nutrient retention and neutral detergent fibre (NDF) and acid detergent fibre (ADF) digestibility. Horses were exercise conditioned and completed another SET on day 42.V160andV200were calculated from SET heart rates (HR). Lactate, glucose, haematocrit (HT) and haemoglobin (HB) concentrations were determined from SET blood samples. Total leukocyte count, and circulating numbers of various leukocytes and IgG, IgM and IgA concentrations were determined in rest and recovery blood samples from both SETs. Geldings on BP (n = 3) ate more feed than CO. BP had less phosphorus excretion, and tended to retain more nitrogen. BP tended to digest more NDF and ADF while having lower NDF digestibility and tending to have lower ADF digestibility. No treatment differences existed forV160andV200, HR, lactate, HT and HB. There was a trend for lymphocyte counts to be lower in BP than CO on day 42. Dynamic Trio 50/50 supplementation may have a positive effect on performance by helping horses in training meet their potentially increased nutrient demands by increasing feed intake and thus nutrient retention.
Determination of effective dosage of GH‐releasing factor for blood GH responses in mithun (Bos frontalis)
Authors: Mondal Mohan , Rajkhowa Chandan , Prakash B. S. 
Published: May 2006

SummaryA study was undertaken to determine the effective dosage of GH‐releasing hormone (GRF) required to produce blood GH response in mithun (Bos frontalis), a semi‐wild ruminant species. For the purpose, 12 mithuns averaging 11.5 months of age and 146 kg body weight (BW) were randomly assigned to receive GRF (n = 12), administered at 0 (normal saline), 5, 10 and 20 μg per 100 kg BW. Blood samples were collected prior to and after GRF administration at −60, −45, −30, −15, −10, −5, 0 min and 5, 10, 15, 30 and thereafter, at 15‐min interval up to 8 h post‐GRF were assayed for plasma GH. For all the dosages, the pre‐treatment GH concentrations and corresponding area under GH response curve (AUC) were similar (p > 0.05). The post‐GRF plasma GH responses to different dosages of GRF viz. 5, 10 and 20 μg per 100 kg BW and corresponding AUCs were higher (p < 0.05) than those recorded in normal saline‐treated controls. The GH responses to 10 and 20 μg GRF per 100 kg BW and corresponding AUCs were higher (p < 0.05) than those registered in mithuns administered with 5 μg GRF per 100 kg BW. Interestingly, post‐GRF concentration of plasma GH and AUCs were not different for 10 and 20 μg GRF per 100 kg BW dosages. In all animals treated with GRF, a peak of GH was registered within 10 to 20 min post‐GRF. Following 5 μg GRF per 100 kg BW, GH concentrations were maintained at higher level for 90 min post‐GRF and thereafter became similar to that of controls and it was 435 min for 10 and 20 μg GRF per 100 kg BW dosages. In conclusion, our results suggest that 10 μg GRF per 100 kg BW is the dosage, which can be used for augmentation of mithun production.
The State and its Welfare State: How do Welfare State Changes Affect the Make‐up of the Nation State?
Authors: Rothgang Heinz , Obinger Herbert , Leibfried Stephan 
Published: May 2006

AbstractWith respect to changes in the welfare states of OECD countries, scholars most of the time are looking for common trends; that is, they look for similar movements in different states, such as welfare state retrenchment, recalibration, etc. As we show in this article, data on welfare state spending and financing do not, however, support such stark tendencies like retrenchment. We therefore suggest looking for corridor effects rather than level effects, i.e. analysing changes in the dispersion of welfare state regimes rather than shifts in the mean values. Our analysis suggests that convergence, i.e. decreasing diversity among states in spending, financing and regulation patterns, may have been the most important pattern of welfare state change in the last three decades – a pattern easily overlooked in past and current research. Convergence of welfare state regimes also affects our views on the modern nation state itself since the varieties of welfare capitalism in the twentieth century are themselves an expression of the sovereignty and autonomy of the nation state. If nation states are forced to surrender national particularities, to mellow their characteristic differences and to move incrementally towards a one‐size‐fits‐all common model via ‘shrinking corridors’, such a blurring of welfare regimes, such a beclouding of difference, should also be regarded as a significant change taking place in the centre of the Western nation state's make‐up.
Earnings of Immigrants in Sweden, 1978 to 1999
Authors: Gustafsson Björn , Zheng Jinghai 
Published: May 2006

ABSTRACTThis paper aims to illuminate the deteriorating situation of immigrants in the Swedish labour market. Two questions are in focus. First, is the pattern of a deteriorating labour market situation and increased difficulty entering the economy of the host country applicable to all immigrants? Second, are immigrants more vulnerable to the state of the economy than natives? Large samples of immigrant women and immigrant men as well as large samples of native men and women for the period 1978 to 1999 are studied by observing annual earnings. Low annual earnings signal a weak labour market attachment.The results show that while earnings of foreign‐born relative to natives deteriorated for less‐privileged immigrants, this was not the case for young adults originating from the north‐western part of Europe and North America. In addition, there were no indications of newer immigrants of such origins faring worse than their peers who had arrived earlier when observed during the same number of years since immigration. In contrast, earnings of immigrants from southern and eastern Europe and countries outside Europe, who arrived during the first part of the 1980s, were lower than for their counterparts who had arrived earlier. Non‐European immigrants who arrived during the first half of the 1980s had earnings in the mid‐1990s that were remarkably low.Less‐privileged immigrants are more vulnerable than natives to the state of the economy as measured by the unemployment rate. Recently arrived immigrants are more vulnerable to the state of the economy and some signs indicate vulnerability weakens by year since immigration. Thus, a low unemployment rate is relatively more important for categories of immigrants that are not in a privileged situation in the host country.
How Integrated are Finns in the Swedish Labour Market? Outcomes of Free Labour Mobility
Authors: Saarela Jan , Rooth Dan‐Olof 
Published: May 2006

ABSTRACTDue to the agreement of a common Nordic labour market, Finns have for several decades constituted the largest immigrant group in Sweden. However, there have been few studies explicitly concerned with how well they are integrated in the labour market. This paper attempts to fill part of this gap by studying how they succeeded before and after the economic crisis in the 1990s. Employment levels and earnings of Finnish immigrants in prime working ages are compared with those of native Swedes by utilizing matched cross sections of the total population from 1990 and 2001. We aim to see how much of any differential can be attributed to simple background factors such as age, gender, educational level, and county of residence. Our findings reveal that earnings and employment levels of Finnish males are about 10 per cent lower than those of native Swedes, and that this performance gap tends to have become wider over time. There is, however, substantial variation across immigrant cohorts, and differentials in educational levels play a significant role only with regard to the earnings gap. In contrast with the males, Finnish females tend to be better integrated, as their labour market outcomes are very similar to those of native Swedes.
Local variation of haemoparasites and arthropod vectors, and intestinal protozoans in spiny mice (Acomys dimidiatus) from four montane wadis in the St Katherine Protectorate, Sinai, Egypt
Authors: Bajer A. , Harris P. D. , Behnke J. M. , Bednarska M. , Barnard C. J. , Sherif N. , Clifford S. , Gilbert F. S. , Siński E. , Zalat S. 
Published: May 2006

AbstractHaemoparasite infections and infestations with potential arthropod vectors were assessed in spiny mice Acomys dimidiatus from four wadis in the arid montane region of the southern Sinai in Egypt in late summer 2000. Five taxa of haemoparasites (Haemobartonella spp. 80%, Hepatozoon sp. 20.6%, Trypanosoma acomys 17.5%, Bartonella spp. 2.5% and Babesia sp. 1.9%) were recorded. Additionally, infections with two intestinal protozoa, Cryptosporidium cf. parvum and Giardia sp., were quantified, both with similar prevalence (17.0 and 17.6%, respectively). 17.9% of mice carried fleas (Parapulex chephrensis and Xenopsylla dipodilli) and 32.1% had lice (Polyplax oxyrrhyncha and Polyplax brachyrrhycha combined). Marked differences in the prevalence and abundance of infections were detected between the four wadis, particularly with respect to T. acomys, Hepatozoon sp. and fleas, which were largely aggregated in just two of the four sites (Wadis Gharaba and Tlah). In contrast, the intestinal protozoa were more common, and abundance was higher, in Wadi El Arbaein. Intrinsic factors also contributed to a variation in prevalence, with strong age‐dependent increases in the prevalence and abundance of Hepatozoon sp., higher mean species richness, prevalence of Cr. cf. parvum, and abundance of Giardia sp. and Hepatozoon sp. in female mice. Haemobartonella spp. showed an age‐dependent reduction in abundance and higher abundance among male mice. A weak association was found between the prevalence of T. acomys and its putative flea vector. The single extrinsic factor in the study, site of capture, was more important than the intrinsic factors in explaining variation in the prevalence and abundance of haemoparasites, intestinal protozoa and arthropod vectors. In the high mountains of southern Sinai, the parasite fauna of spiny mice is distinct in each wadi, and hence we expect the parasites to exert spatially different co‐evolutionary pressures on their hosts, with a resultant variation in host life histories.
Behavioral and endocrine correlates of reproductive failure in social aggregations of captive wolverines (Gulo gulo)
Authors: Dalerum F. , Creel S. , Hall S. B. 
Published: May 2006

AbstractSociality in mammals is often viewed as a dichotomy, with sociality contrasted against solitariness. However, variation within these broad categories may have strong effects on individual fitness. For example, reproductive suppression of social subordinates is generally associated with group living, but suppression may also occur in solitary species if the behavioral and physiological processes involved can be modulated by the demographic environment. To investigate whether behavioral and physiological traits that normally are associated with group living might be latent even in a solitary species, we explored the level of sociality and investigated causes and mechanisms of reproductive failure in female wolverines Gulo gulo that experienced a highly aggregated social environment in captivity. Behaviorally, females showed low levels of aggression and intermediate levels of social interactions. Reproductive failure seemed to have been related to low social rank and to have occurred between ovulation and implantation in 13 out of 15 breeding attempts. However, three of eight females observed to mate produced offspring, indicating that no individual female fully managed to monopolize breeding. Reproductive failure was not related to elevated levels of glucocorticoid stress hormones. Rather, elevated glucocorticoid levels during the mating season were associated with successful reproduction. We suggest that social tendencies and physiological mechanisms mediating reproductive suppression may be viewed as reaction norms to the social environment. We further suggest that the social flexibility of solitary carnivores might be greater than is commonly observed, due to ecological constraints that may limit aggregation.
Ancient and modern steps during the domestication of guinea pigs (Cavia porcellus L.)
Authors: Spotorno A. E. , Marín J. C. , Manríquez G. , Valladares J. P. , Rico E. , Rivas C. 
Published: May 2006

AbstractTo test whether there are differences between living lineages of domestic guinea pigs Cavia porcellus, we studied 118 specimens from six breeds collected along six Andean countries as well as 15 from the wild cavy species (Cavia tschudii). The mean weight and body length of 15 adult wild cavies (295±31 g, 242±8.3 mm) were significantly smaller than 25 creole guinea pigs from Bolivia and Chile (639±157 g, 287±23.7 mm, respectively). Eighteen laboratory/pet guinea pigs (including the English Pirbright breed) were also smaller (900±173 g, 308±21 mm) than 25 improved ones from Peru (Tamborada breed, 1241±75.4 g, 317±12 mm) and Ecuador (Auqui breed, 1138±65.5 g, 307±8 mm). Similar size increases appeared in the first axis of a principal component analysis of six skeletal measurements, recovering 84% of total variation. Phylogenetic and haplotype analyses of complete cytochrome b gene sequences consistently joined all 22 domestic individuals (13 shared unambiguous substitutions, 100% bootstrap in 1000 replicates), probably from a single first ancient domestication in the western Andes. Six laboratory/pet sequences were also joined within a common branch (six shared substitutions, 96% bootstrap), probably from a documented European second phase. By contrast, those from improved Auqui joined a northern creole subgroup (one shared substitution, 84% bootstrap), and those from Nativa and improved Tamborada clustered together and with a southern creole subgroup (four shared substitutions, 86% bootstrap); this suggests at least two independent modern events during a more complex third phase, producing two improved guinea pigs selected for size and meat. Cavia tschudii sequences showed some unexpected geographic variation.
Irreversible aggregation of protein synthesis machinery after focal brain ischemia
Authors: Zhang F. , Liu C. L. , Hu B. R. 
Published: May 2006

AbstractFocal brain ischemia leads to a slow type of neuronal death in the penumbra that starts several hours after ischemia and continues to mature for days. During this maturation period, blood flow, cellular ATP and ionic homeostasis are gradually recovered in the penumbral region. In striking contrast, protein synthesis is irreversibly inhibited. This study used a rat focal brain ischemia model to investigate whether or not irreversible translational inhibition is due to abnormal aggregation of translational complex components, i.e. the ribosomes and their associated nascent polypeptides, protein synthesis initiation factors and co‐translational chaperones. Under electron microscopy, most rosette‐shaped polyribosomes were relatively evenly distributed in the cytoplasm of sham‐operated control neurons, but clumped into large abnormal aggregates in penumbral neurons subjected to 2 h of focal ischemia followed by 4 h of reperfusion. The abnormal ribosomal protein aggregation lasted until the onset of delayed neuronal death at 24–48 h of reperfusion after ischemia. Biochemical study further suggested that translational complex components, including small ribosomal subunit protein 6 (S6), large subunit protein 28 (L28), eukaryotic initiation factors 2α, 4E and 3η, and co‐translational chaperone heat‐shock cognate protein 70 (HSC70) and co‐chaperone Hdj1, were all irreversibly clumped into large abnormal protein aggregates after ischemia. Translational complex components were also highly ubiquitinated. This study clearly demonstrates that focal ischemia leads to irreversible aggregation of protein synthesis machinery that contributes to neuronal death after focal brain ischemia.