Community Genetics Reveal Elevated Levels of Sympatric Gene Flow among Morphologically Similar but Not among Morphologically Dissimilar Species of Lake Victoria Cichlid Fish

We examined genetic structure among five species of Lake Victoria haplochromine cichlids in four island communities, using a full factorial sampling design that compared genetic differentiation between pairs of species and populations of varying morphological similarity and geographical proximity. We found that allopatric conspecific populations were on average significantly more strongly differentiated than sympatric heterospecific populations of morphologically similar species. Allopatric heterospecific populations of morphologically dissimilar species were most differentiated. Our work demonstrates that phenotypic divergence can be maintained and perhaps even evolve in sympatry despite considerable gene flow between species. Conversely, phenotypic resemblance among conspecific populations can be maintained despite geographical isolation. Additionally we show that anthropogenically increased hybridization does not affect all sympatric species evenly but predominantly affects morphologically similar and closely related species. This has important implications for the evolution of reproductive isolation between species These findings are also consistent with the hypothesis of speciation reversal due to weakening of divergent selection and reproductive isolation as a consequence of habitat homogenization and offers an evolutionary mechanistic explanation for the observation that species poor assemblages in turbid areas of the lake are characterized by just one or two species in each of a few morphologically distinct genera.

Assimilation and contrast in web product reviews: devaluing the recommendation of a proficient but dissimilar reviewer

When viewing web-consumer reviews consumers encounter the reviewers in an anonymous environment. Although their interactions are only virtual they still exchange social information, e.g. often reviewers refer to their proficiency or consumption motives within the review texts. Do these social information harm the viewers’ perception of the recommended products? The present study addresses this question by applying the paradigm of social comparison (Mussweiler, 2003) to web-consumer reviews. In a laboratory experiment with a student sample (n = 120) we manipulated the perceived similarity between reviewer and viewer and the perceived proficiency of the reviewer. A measurement of achievement goals (Elliott & McGregor, 2001) and average number of hours of study prior to the experiment allowed to introduce the reviewer as high [low] in proficiency and similar [dissimilar] in achievement goals. As predicted, the viewer’s evaluation of the recommended products differed as a function of this social information. Contrasting with the reviewer led to devaluing the products recommended by a proficient but dissimilar reviewer. However, against our prediction social comparison with the reviewer did not affect the viewer`s self-evaluation. Whether social information in web-product reviews affects the viewer`s self-evaluation and induces both social comparison processes remains an open question. Future studies aim to address this by manipulating the informational focus of the viewer, rather than the perceived similarity between viewer and reviewer. So far, the present study extends the application of social comparison to consumption environments and contributes to the understanding of the virtual social identity.

Posterior versus anterior circulation strokes: comparison of clinical, radiological and outcome characteristics

Physicians treating patients with posterior circulation strokes (PCS) tended to debate more on whether or not to introduce anticoagulation rather than performing investigations to identify stroke aetiology, as in patients with anterior circulation strokes (ACS). Recent findings suggest that stroke aetiologies of PCS and ACS are more alike than dissimilar, suggesting that PCS deserve the same investigations as ACS. The characteristics and current diagnostic evaluation between patients with PCS and ACS were compared.

Biomechanical effects of environmental and engineered particles on human airway smooth muscle cells

The past decade has seen significant increases in combustion-generated ambient particles, which contain a nanosized fraction (less than 100 nm), and even greater increases have occurred in engineered nanoparticles (NPs) propelled by the booming nanotechnology industry. Although inhalation of these particulates has become a public health concern, human health effects and mechanisms of action for NPs are not well understood. Focusing on the human airway smooth muscle cell, here we show that the cellular mechanical function is altered by particulate exposure in a manner that is dependent upon particle material, size and dose. We used Alamar Blue assay to measure cell viability and optical magnetic twisting cytometry to measure cell stiffness and agonist-induced contractility. The eight particle species fell into four categories, based on their respective effect on cell viability and on mechanical function. Cell viability was impaired and cell contractility was decreased by (i) zinc oxide (40-100 nm and less than 44 microm) and copper(II) oxide (less than 50 nm); cell contractility was decreased by (ii) fluorescent polystyrene spheres (40 nm), increased by (iii) welding fumes and unchanged by (iv) diesel exhaust particles, titanium dioxide (25 nm) and copper(II) oxide (less than 5 microm), although in none of these cases was cell viability impaired. Treatment with hydrogen peroxide up to 500 microM did not alter viability or cell mechanics, suggesting that the particle effects are unlikely to be mediated by particle-generated reactive oxygen species. Our results highlight the susceptibility of cellular mechanical function to particulate exposures and suggest that direct exposure of the airway smooth muscle cells to particulates may initiate or aggravate respiratory diseases.

Lipopolysaccharide and lipoteichoic acid induce different immune responses in the bovine mammary gland

Different pathogens, such as Escherichia coli and Staphylococcus aureus, can be responsible for different outcomes of mastitis; that is, acute and severe or chronic and subclinical. These differences in the disease could be related to different mammary responses to the pathogens. The objective of this study was to determine if intramammary challenge with the endotoxins lipopolysaccharide (LPS), from E. coli, and lipoteichoic acid (LTA), from Staph. aureus, induce different immune responses in vivo in milk cells and mammary tissue. To provide a reference level for comparing the challenge and to show the different stimulation of the mammary immune system on a quantitatively similar level, dosages of LPS and LTA were chosen that induced an increase of somatic cells in milk to similar maxima. One udder quarter in each of 21 lactating dairy cows was challenged with 0.2 mug of LPS or 20 mug of LTA. From these quarters and from respective control quarters, milk cells or tissue biopsies were obtained at 0, 6, and 12h relative to the challenge to measure mRNA expression of tumor necrosis factor-alpha (TNFalpha), IL-1beta, IL-8, lactoferrin, and RANTES (regulated upon activation, normal T-cell expressed and secreted). Furthermore, if no biopsies were performed, hourly milk samples were taken for measurement of somatic cell count, lactate dehydrogenase (LDH), and TNFalpha. Somatic cell count increased in all treatments to similar maxima with LPS and LTA treatments. Concentrations of TNFalpha in milk increased with LPS but not with LTA. The activity of LDH in milk increased in both treatments and was more pronounced with LPS than with LTA. The mRNA expression of TNFalpha, IL-1beta, IL-8, and RANTES showed increases in milk cells, and LPS was a stronger inducer than LTA. Lactoferrin mRNA expression decreased in milk cells with LPS and LTA treatments. The measured factors did not change in either treatment in mammary tissue. Challenge of udder quarters with dosages of LPS and LTA that induce similar increases in SCC stimulate the appearance of different immune factor patterns. This dissimilar response to LPS and LTA may partly explain the different course and intensity of mastitis after infection with E. coli and Staph. aureus, respectively.

Binding sites of muscarinic and adrenergic receptors in gastrointestinal tissues of dairy cows suffering from left displacement of the abomasum

Muscarinic acetylcholine (M) and adrenergic (AR) receptors mediate gastrointestinal motility. Using radioligand binding assays and real-time polymerase chain reaction, the densities of binding sites and mRNA levels of M(2), M(3), alpha(2AD)- and beta(2)-AR were compared in muscle tissues from the abomasal fundus, pylorus, duodenum, caecum, and external loop of the spiral colon of eight cows with left displacement of abomasum (LDA), and of eight healthy cows. Specific binding of the [(3)H]-ligands to each of the four receptors was competitive and saturable. Binding sites of M(2) (all intestinal sites), M(3) (duodenum and caecum), and of alpha(2AD)-AR (abomasal fundus) were lower (P<0.05) in cows with LDA than in healthy cows. The coefficients of correlation between binding sites and mRNA transcripts of receptors were dissimilar in cows with LDA and healthy cows. The decrease in densities of M (intestine) and of alpha(2AD)-AR (abomasum) receptors suggests their implication in the impairment of motility associated with or leading to LDA.

Castration of lambs: a welfare comparison of different castration techniques in lambs over 10 weeks of age

Seventy male lambs over 10 weeks of age were castrated using Burdizzo, rubber rings, or surgery to assess the acute and long-term effects of castration. All castrations were performed under local anaesthesia. The surgically castrated lambs were additionally sedated with xylazine and the sedation reversed with tolazoline. The frequency of abnormal postures and immediate behavioural responses indicated that surgically castrated lambs were most distressed; the lambs castrated using Burdizzo and rubber rings were not dissimilar to those of the control group. Between 1.5 and 9h after castration, signs of pain and distress were at a lower level in lambs anaesthetised with bupivacaine compared with those treated with lidocaine. Due to the markedly faster wound healing, Burdizzo castration seemed to be preferable (fewer signs of long-term pain) when compared to the rubber ring technique. It was concluded that local anaesthesia with bupivacaine, followed by the Burdizzo method is the preferable technique for the castration of lambs older than 10 weeks of age.

Effect of laser soldering irradiation on covalent bonds of pure collagen

Laser tissue welding and soldering is being increasingly used in the clinical setting for defined surgical procedures. The exact induced changes responsible for tensile strength are not yet fully investigated. To further improve the strength of the bonding, a better understanding of the laser impact at the subcellular level is necessary. The goal of this study was to analyze whether the effect of laser irradiation on covalent bonding in pure collagen using irradiances typically applied for tissue soldering. Pure rabbit and equine type I collagen were subjected to laser irradiation. In the first part of the study, rabbit and equine collagen were compared using identical laser and irradiation settings. In the second part of the study, equine collagen was irradiated at increasing laser powers. Changes in covalent bonding were studied indirectly using the sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) technique. Tensile strengths of soldered membranes were measured with a calibrated tensile force gauge. In the first experiment, no differences between the species-specific collagen bands were noted, and no changes in banding were found on SDS-PAGE after laser irradiation. In the second experiment, increasing laser irradiation power showed no effect on collagen banding in SDS-PAGE. Finally, the laser tissue soldering of pure collagen membranes showed virtually no determinable tensile strength. Laser irradiation of pure collagen at typical power settings and exposure times generally used in laser tissue soldering does not induce covalent bonding between collagen molecules. This is true for both rabbit and equine collagen proveniences. Furthermore, soldering of pure collagen membranes without additional cellular components does not achieve the typical tensile strength reported in native, cell-rich tissues. This study is a first step in a better understanding of laser impact at the molecular level and might prove useful in engineering of combined collagen-soldering matrix membranes for special laser soldering applications.

Magnetic field exposure and neurodegenerative diseases--recent epidemiological studies

OBJECTIVES: To analyse the results of recent studies not yet included in a 2003 report of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) on occupational exposure to low-frequency electromagnetic fields as potential risk factor for neurodegenerative diseases. METHODS: A literature search was conducted in the online databases of PubMed, ISI Web of Knowledge, DIMDI and COCHRANE, as well as in specialised databases and journals. Eight studies published between January 2000 and July 2005 were included in the review. RESULTS: The findings of these studies contribute to the evidence of an association between occupational magnetic field exposure and the risk of dementia. Regarding amyotrophic lateral sclerosis, the recent results confirm earlier observations of an association with electric and electronic work and welding. Its relationship with magnetic field exposure remains unsolved. There are only few findings pointing towards an association between magnetic field exposure and Parkinson's disease. CONCLUSIONS: The epidemiological evidence for an association between occupational exposure to low-frequency electromagnetic fields and the risk of dementia has increased during the last five years. The impact of potential confounders should be evaluated in further studies.

Gene duplication: a drive for phenotypic diversity and cause of human disease

Gene duplication is one of the key factors driving genetic innovation, i.e., producing novel genetic variants. Although the contribution of whole-genome and segmental duplications to phenotypic diversity across species is widely appreciated, the phenotypic spectrum and potential pathogenicity of small-scale duplications in individual genomes are less well explored. This review discusses the nature of small-scale duplications and the phenotypes produced by such duplications. Phenotypic variation and disease phenotypes induced by duplications are more diverse and widespread than previously anticipated, and duplications are a major class of disease-related genomic variation. Pathogenic duplications particularly involve dosage-sensitive genes with both similar and dissimilar over- and underexpression phenotypes, and genes encoding proteins with a propensity to aggregate. Phenotypes related to human-specific copy number variation in genes regulating environmental responses and immunity are increasingly recognized. Small genomic duplications containing defense-related genes also contribute to complex common phenotypes.

Female-biased dispersal and patrilocal kin groups in a mammal with resource-defence polygyny

In most mammals, dispersal rates are higher in males than in females. Using behavioural and genetic data of individually marked bats, we show that this general pattern is reversed in the greater sac-winged bat (Saccopteryx bilineata). Dispersal is significantly female biased and male philopatry in combination with rare male immigration causes a patrilineal colony structure. Female dispersal helps avoid father-daughter inbreeding, as male tenure exceeds female age at first breeding in this bat species. Furthermore, our data suggest that females may engage in extra-harem copulations to mate with genetically dissimilar males, and thus avoid their male descendants as mating partners. Acquaintance with the natal colony might facilitate territory takeover since male sac-winged bats queue for harem access. Given the virtual absence of male immigration and the possible lower reproductive success of dispersing males, we argue that enhancing the likelihood of settlement of male descendants could be adaptive despite local mate competition. We conclude that resource defence by males is important in promoting male philopatry, and argue that the potential overlap of male tenure and female first conception is the driving force for females to disperse.

Evaluation and comparison of cartilage repair tissue of the patella and medial femoral condyle by using morphological MRI and biochemical zonal T2 mapping

The objective of this study was to use advanced MR techniques to evaluate and compare cartilage repair tissue after matrix-associated autologous chondrocyte transplantation (MACT) in the patella and medial femoral condyle (MFC). Thirty-four patients treated with MACT underwent 3-T MRI of the knee. Patients were treated on either patella (n = 17) or MFC (n = 17) cartilage and were matched by age and postoperative interval. For morphological evaluation, the MR observation of cartilage repair tissue (MOCART) score was used, with a 3D-True-FISP sequence. For biochemical assessment, T2 mapping was prepared by using a multiecho spin-echo approach with particular attention to the cartilage zonal structure. Statistical evaluation was done by analyses of variance. The MOCART score showed no significant differences between the patella and MFC (p > or = 0.05). With regard to biochemical T2 relaxation, higher T2 values were found throughout the MFC (p < 0.05). The zonal increase in T2 values from deep to superficial was significant for control cartilage (p < 0.001) and cartilage repair tissue (p < 0.05), with an earlier onset in the repair tissue of the patella. The assessment of cartilage repair tissue of the patella and MFC afforded comparable morphological results, whereas biochemical T2 values showed differences, possibly due to dissimilar biomechanical loading conditions.

Say on Pay: ein Überblick über Gestaltungsoptionen, ökonomische Konsequenzen und Erkenntnisse aus Empirie und Laborexperimenten

Unter dem Stichwort Say on Pay (SoP) haben in den letzen Jahren die meisten Länder der EU und die USA den Aktionären Abstimmungsrechte im Zusammenhang mit der Vergütung des Top-Managements eingeräumt. Zwischen den einzelnen Ländern bestehen jedoch erhebliche Unterschiede hinsichtlich der konkreten Ausgestaltung des SoP. Dieser Beitrag diskutiert die Wirkungen unterschiedlicher Gestaltungsoptionen des SoP auf die Anreizgestaltung und den Nutzen des Managements und der Aktionäre im Rahmen eines einfachen linearen Agency Modells. Dabei erweisen sich das vorvertragliche bindende SoP und das bedingt verpflichtende, nachvertragliche bindende SoP gegenüber den anderen untersuchten Varianten als überlegen. Während das konsultative SoP an seiner mangelnden Durchsetzbarkeit leidet, bietet das nachvertragliche bindende SoP Anreize für opportunistisches Verhalten auf Seiten der Aktionäre und führt deshalb zu Wohlfahrtsverlusten. In Ergänzung der Modellanalyse wird ein Überblick über die wichtigsten empirischen und experimentellen Studien zum Thema SoP gegeben und deren Inhalt im Lichte der Modellergebnisse diskutiert. Most countries of the European Union as well as the US recently introduced shareholder votes on the remuneration of executives, also referred to as “Say on Pay” (SoP). Interestingly, legislators in different jurisdictions opted for quite dissimilar voting right regimes. We provide an overview of the main regulatory approaches and discuss the potential impact of variations in SoP design on the structure of compensation contracts and the utility of shareholders and executives. We find that pre-contractual SoP and conditional post-contractual SoP with binding consequences are in the best interest of shareholders. By contrast, advisory SoP typically suffers from lacking enforceability. We also find that post-contractual SoP with binding consequences results in efficiency losses because it fuels moral hazard on the part of shareholders. We complement the theoretical analysis with a discussion of recent empirical and experimental studies on Say on Pay.