Recent sympatric speciation involving habitat-associated nuptial colour polymorphism in a crater lake cichlid

Even though the idea that modes of speciation other than allopatric speciation are possible in nature is now widespread, compelling examples of ecological speciation in sympatry remain rare. We studied an undescribed radiation of haplochromine cichlids in a young crater lake in western Uganda, and in the small river that is nearby but has currently no known surface connection to the lake. We describe two different modes of speciation that occurred in this cichlid lineage within the past 1,500–10,000 years. Not constrained by gene flow, allopatric divergence between river and lake cichlids affects many different morphological traits as well as nuptial colouration—muted in the river, but intensified and polymorphic in lake cichlids—and neutral genetic differentiation. More surprisingly, we demonstrate a case for sympatric speciation within the small lake that is associated with dramatic differences in male breeding colouration (yellow with bright red-chest versus bright blue) and subtle differences in microhabitat, feeding regime and morphology. Reproductive isolation by assortative mating is suggested by significant differentiation between yellow and blue males in neutral markers of gene flow despite complete sympatry. We hypothesize speciation is mediated by divergent selection on sexual signalling between microhabitats.

     

Leprosy in a prison population: A new active search strategy and a prospective clinical analysis

BackgroundThis study evaluates an active search strategy for leprosy diagnosis based on responses to a Leprosy Suspicion Questionnaire (LSQ), and analyzing the clinical, immunoepidemiological and follow-up aspects for individuals living in a prison population.MethodsA cross-sectional study based on a questionnaire posing 14 questions about leprosy symptoms and signs that was distributed to 1,400 prisoners. This was followed by dermatoneurological examination, anti-PGL-I serology and RLEP-PCR. Those without leprosy were placed in the Non-leprosy Group (NLG, n = 1,216) and those diagnosed with clinical symptoms of leprosy were placed in the Leprosy Group (LG, n = 34).FindingsIn total, 896 LSQ were returned (64%), and 187 (20.9%) of the responses were deemed as positive for signs/symptoms, answering 2.7 questions on average. Clinically, 1,250 (89.3%) of the prisoners were evaluated resulting in the diagnosis of 34 new cases (LG), based on well-accepted clinical signs and symptoms, a new case detection rate of 2.7% within this population, while the NLG were comprised of 1,216 individuals. The confinement time medians were 39 months in the LG while it was 36 months in the NLG (p>0.05). The 31 leprosy cases who responded to the questionnaire (LSQ+) had an average of 1.5 responses. The symptoms “anesthetized skin area” and “pain in nerves” were most commonly mentioned in the LG while “tingling, numbness in the hands/feet”, “sensation of pricks and needles”, “pain in nerves” and “spots on the skin” responses were found in more than 30% of questionnaires in the NLG. Clinically, 88.2% had dysesthetic macular skin lesions and 97.1% presented some peripheral nerve impairment, 71.9% with some degree of disability. All cases were multibacillary, confirming a late diagnosis. Anti-PGL-I results in the LG were higher than in the NLG (p<0.0001), while the RLEP-PCR was positive in 11.8% of the patients.InterpretationOur findings within the penitentiary demonstrated a hidden prevalence of leprosy, although the individuals diagnosed were likely infected while living in their former communities and not as a result of exposure in the prison. The LSQ proved to be an important screening tool to help identify leprosy cases in prisons.     

Dehydroascorbate and glutathione regulate the cellular development of <Emphasis Type=Italic>Nicotiana tabacum</Emphasis> L. SR-1 protoplasts

A Nicotiana tabacum L. SR-1 leaf protoplast system was used to study the effects of dehydroascorbate and glutathione on cellular development. We found that dehydroascorbate is readily taken up by protoplasts and internally reduced to ascorbate. Concomitantly, cell division was inhibited and cell expansion stimulated. In this respect, dehydroascorbate counteracted auxin-mediated leaf protoplast development. In contrast to the effects of dehydroascorbate, glutathione-induced cell dedifferentiation, and this effect is similar to that mediated by high auxin concentrations. We conclude that dehydroascorbate and glutathione affect the auxin-mediated regulation of cellular development. Therefore, the biological role of these compounds extends beyond stress tolerance and defense.     

Topological analysis of the complex formed between neurokinin A and the NK2 tachykinin receptor

Neurokinin A stimulates physiological responses in the peripheral and central nervous systems upon interacting primarily with the tachykinin NK2 receptor (NK2R). In this study, the structure of NKA bound to the NK2R is characterised by use of fluorescence resonance energy transfer. Four fluorescent NKA analogues with Texas red introduced at amino acid positions 1, 4, 7 and 10 were prepared. When bound to a NK2R carrying enhanced green fluorescent protein at the N-terminus, all peptides reduce green fluorescent protein fluorescence from 10% to 50% due to energy transfer. The derived donor-acceptor distances are 46, 55, 59 and 69 A for the fluorophore linked to positions 1-10, respectively. The monotonic increase in distance clearly indicates that the peptide adopts an extended structure when bound to its receptor. The present data are used, in combination with rhodopsin structure, fluorescence studies, photoaffinity labelling and site-directed mutagenesis data to design a computer model of the NKA-NK2R complex. We propose that the N-terminus of NKA is exposed and accessible to the extracellular medium. Subsequent amino acids of the NKA peptide become progressively more buried residues up to approximately one-third of the transmembrane-spanning domain.     

Ca2+ channel currents and contraction in CaVbeta3-deficient ileum smooth muscle from mouse

Voltage activated L-type Ca(2+) channels are the principal Ca(2+) channels in intestinal smooth muscle cells. They comprise the ion conducting Ca(V)1 pore and the ancillary subunits alpha(2)delta and beta. Of the four Ca(V)beta subunits Ca(V)beta(3) is assumed to be the relevant Ca(V)beta protein in smooth muscle. In protein lysates isolated from mouse ileum longitudinal smooth muscle we could identify the Ca(V)1.2, Ca(V)alpha(2), Ca(V)beta(2) and Ca(V)beta(3) proteins, but not the Ca(V)beta(1) and Ca(V)beta(4) proteins. Protein levels of Ca(V)1.2, Ca(V)alpha(2) and Ca(V)beta(2) are not altered in ileum smooth muscle obtained from Ca(V)beta(3)-deficient mice indicating that there is no compensatory increase of the expression of these channel proteins. Neither the Ca(V)beta(2) nor the other Ca(V)beta proteins appear to substitute for the lacking Ca(V)beta(3). L-type Ca(2+) channel properties including current density, inactivation kinetics as well as Cd(2+)- and dihydropyridine sensitivity were identical in cells of both genotypes suggesting that they do not require the presence of a Ca(V)beta(3) protein. However, a key hallmark of the Ca(V)beta modulation of Ca(2+) current, the hyperpolarisation of channel activation is slightly but significantly reduced by 4 mV. In addition to L-type Ca(2+) currents T-type Ca(2+) currents could be recorded in the murine ileum smooth muscle cells, but T-type currents were not affected by the lack of Ca(V)beta(3). Both proteins, Ca(V)beta(2) and Ca(V)beta(3) are localized near the plasma membrane and the localization of Ca(V)beta(2) is not altered in Ca(V)beta(3) deficient cells. Spontaneous contractions and potassium and carbachol induced contractions are not significantly different between ileum longitudinal smooth muscle strips from mice of both genotypes. In summary the data show that in ileum smooth muscle cells, Ca(V)beta(3) has only subtle effects on L-type Ca(2+) currents, appears not to be required for spontaneous and potassium induced contraction but might have a function beyond being a Ca(2+) channel subunit.     

Down-regulation of E-cadherin in human bronchial epithelial cells leads to epidermal growth factor receptor-dependent Th2 cell-promoting activity

Airway epithelial cells are well-known producers of thymus- and activation-regulated chemokine (TARC), a Th2 cell-attracting chemokine that may play an important role in the development of allergic airway inflammation. However, the mechanism responsible for up-regulation of TARC in allergy is still unknown. In the asthmatic airways, loss of expression of the cell-cell contact molecule E-cadherin and reduced epithelial barrier function has been observed, which may be the result of an inadequate repair response. Because E-cadherin also suppressed multiple signaling pathways, we studied whether disruption of E-cadherin-mediated cell contact may contribute to increased proallergic activity of epithelial cells, e.g., production of the chemokine TARC. We down-regulated E-cadherin in bronchial epithelial cells by small interference RNA and studied effects on electrical resistance, signaling pathways, and TARC expression (by electric cell-substrate impedance sensing, immunodetection, immunofluorescent staining, and real-time PCR). Small interference RNA silencing of E-cadherin resulted in loss of E-cadherin-mediated junctions, enhanced phosphorylation of epidermal growth factor receptor (EGFR), and the downstream targets MEK/ERK-1/2 and p38 MAPK, finally resulting in up-regulation of TARC as well as thymic stromal lymphopoietin expression. The use of specific inhibitors revealed that the effect on TARC is mediated by EGFR-dependent activation of the MAPK pathways. In contrast to TARC, expression of the Th1/Treg cell-attracting chemokine RANTES was unaffected by E-cadherin down-regulation. In summary, we show that loss of E-cadherin-mediated epithelial cell-cell contact by damaging stimuli, e.g., allergens, may result in reduced suppression of EGFR-dependent signaling pathways and subsequent induction of Th2 cell-attracting molecule TARC. Thus, disruption of intercellular epithelial contacts may specifically promote Th2 cell recruitment in allergic asthma.     

Heritable circadian period length in a wild bird population

Timing is essential, but circadian clocks, which play a crucial role in timekeeping, are almost unaddressed in evolutionary ecology. A key property of circadian clocks is their free-running period length (τ), i.e. the time taken for a full cycle under constant conditions. Under laboratory conditions, concordance of τ with the ambient light–dark cycle confers major fitness benefits, but little is known about period length and its implications in natural populations. We therefore studied natural variation of circadian traits in a songbird, the great tit (Parus major), by recording locomotor activity of 98 hand-raised, wild-derived individuals. We found, unexpectedly, that the free-running period of this diurnal species was significantly shorter than 24 h in constant dim light. We furthermore demonstrate, to our knowledge for the first time in a wild vertebrate, ample genetic variation and high heritability (h² = 0.86 ± 0.24), implying that period length is potentially malleable by micro-evolutionary change. The observed, short period length may be a consequence of sexual selection, as offspring from extra-pair matings had significantly shorter free-running periods than their half-siblings from within-pair matings. These findings position circadian clocks in the ‘real world’ and underscore the value of using chronobiological approaches in evolutionary ecology. Evolutionary ecologists study variation and its fitness consequences, but often have difficulties relating behavioural variation to physiological mechanisms. The findings presented here open the possibility that properties of internal, circadian clocks affect performance in traits that are relevant to fitness and sexual selection.     

Continuous Enzymatic Regeneration of Electron Acceptors Used by Flavoenzymes: Cellobiose Dehydrogenase-Catalyzed Production of Lactobionic Acid as an Example

An efficient enzymatic bioprocess is described in which lactose, an abundant renewable resource produced by the dairy industry, is completely and efficiently converted with a specific productivity of up to 32 g (kU h)^-1 into lactobionic acid, without the formation of any by-products. The key biocatalyst of this new process is the fungal enzyme cellobiose dehydrogenase which oxidizes several β-1,4-linked disaccharides including lactose specifically at position C-1 of the reducing sugar moiety to the corresponding lactones. The electron acceptor employed in this reaction is continuously regenerated with the help of laccase, a H₂O-producing, copper-containing oxidase, and therefore has to be added in low, catalytic amounts only. Redox mediators that were successfully employed in this novel process and hence are compatible with the laccase regeneration system include benzoquinone, ABTS, ferricyanide, or ferrocene, amongst others. Factors affecting operational stability of the biocatalysts employed in this process include the redox mediator used, the temperature, and importantly the volumetric gas flow necessary for maintaining the dissolved oxygen tension. Lactobionic acid is a mild and sweet tasting acid with excellent chelating properties. These useful characteristics have lead to a growing number of patents for diverse applications in the food, pharmaceutical and detergent industries.     

Migrating swans profit from favourable changes in wind conditions at low altitude

Because energy reserves limit flight range, wind assistance may be of crucial importance for migratory birds. We tracked eight Bewicks swans Cygnus columbianus bewickii, using 95-g satellite transmitters with altimeters and activity sensors, during their spring migration from Denmark to northern Russia in 1996. During the 82 occasions where a swans location was recorded in flight, average flight altitude was 165 m a.s.l. with a maximum of 759 m a.s.l., despite winds often being more favourable at higher altitudes. We also counted Bewicks swans departing from the Gulf of Finland and subsequently passing an observatory in the next major stop-over area 800 km further north in the White Sea, northern Russia, during the springs of 1994, 1995 and 1996. A comparison of these counts with wind data provided evidence for Bewicks swans using favourable changes in wind conditions to embark on migration. Changes in the numbers of birds arriving in the White Sea correlated best with favourable changes in winds in the Gulf of Finland 1 day earlier. Again, migratory volume showed a correlation with winds at low altitudes only, despite wind conditions for the swans being more favourable at high altitudes. We conclude that the relatively large Bewicks swan tends to gear its migration to wind conditions at low altitude only. We argue that Bewicks swans do not climb to high altitudes because of mechanical and physiological limitations with respect to the generation of power for flight and to avoid rapid dehydration.Communicated by F. Bairlein     

Identifying object categories from event-related EEG: toward decoding of conceptual representations

Multivariate pattern analysis is a technique that allows the decoding of conceptual information such as the semantic category of a perceived object from neuroimaging data. Impressive single-trial classification results have been reported in studies that used fMRI. Here, we investigate the possibility to identify conceptual representations from event-related EEG based on the presentation of an object in different modalities: its spoken name, its visual representation and its written name. We used Bayesian logistic regression with a multivariate Laplace prior for classification. Marked differences in classification performance were observed for the tested modalities. Highest accuracies (89% correctly classified trials) were attained when classifying object drawings. In auditory and orthographical modalities, results were lower though still significant for some subjects. The employed classification method allowed for a precise temporal localization of the features that contributed to the performance of the classifier for three modalities. These findings could help to further understand the mechanisms underlying conceptual representations. The study also provides a first step towards the use of concept decoding in the context of real-time brain-computer interface applications.