The genetic basis and evolution of red blood cell sickling in deer

Crescent-shaped red blood cells, the hallmark of sickle-cell disease, present a striking departure from the biconcave disc shape normally found in mammals. Characterized by increased mechanical fragility, sickled cells promote haemolytic anaemia and vaso-occlusions and contribute directly to disease in humans. Remarkably, a similar sickle-shaped morphology has been observed in erythrocytes from several deer species, without obvious pathological consequences. The genetic basis of erythrocyte sickling in deer, however, remains unknown. Here, we determine the sequences of human β-globin orthologues in 15 deer species and use protein structural modelling to identify a sickling mechanism distinct from the human disease, coordinated by a derived valine (E22V) that is unique to sickling deer. Evidence for long-term maintenance of a trans-species sickling/non-sickling polymorphism suggests that sickling in deer is adaptive. Our results have implications for understanding the ecological regimes and molecular architectures that have promoted convergent evolution of sickling erythrocytes across vertebrates

Synthesis of Starch-Stabilized Ag Nanoparticles and Hg2+Recognition in Aqueous Media

The starch-stabilized Ag nanoparticles were successfully synthesized via a reduction approach and characterized with SPR UV/Vis spectroscopy, TEM, and HRTEM. By utilizing the redox reaction between Ag nanoparticles and Hg2+, and the resulted decrease in UV/Vis signal, we develop a colorimetric method for detection of Hg2+ion. A linear relationship stands between the absorbance intensity of the Ag nanoparticles and the concentration of Hg2+ion over the range from 10 ppb to 1 ppm at the absorption of 390 nm. The detection limit for Hg2+ions in homogeneous aqueous solutions is estimated to be ~5 ppb. This system shows excellent selectivity for Hg2+over other metal ions including Na+, K+, Ba2+, Mg2+, Ca2+, Fe3+, and Cd2+. The results shown herein have potential implications in the development of new colorimetric sensors for easy and selective detection and monitoring of mercuric ions in aqueous solutions

Species-specific behavioral patterns correlate with differences in synaptic connections between homologous mechanosensory neurons

We characterized the behavioral responses of two leech species, Hirudo verbana and Erpobdella obscura, to mechanical skin stimulation and examined the interactions between the pressure mechanosensory neurons (P cells) that innervate the skin. To quantify behavioral responses, we stimulated both intact leeches and isolated body wall preparations from the two species. In response to mechanical stimulation, Hirudo showed local bending behavior, in which the body wall shortened only on the side of the stimulation. Erpobdella, in contrast, contracted both sides of the body in response to touch. To investigate the neuronal basis for this behavioral difference, we studied the interactions between P cells. Each midbody ganglion has four P cells; each cell innervates a different quadrant of the body wall. Consistent with local bending, activating any one P cell in Hirudo elicited polysynaptic inhibitory potentials in the other P cells. In contrast, the P cells in Erpobdella had excitatory polysynaptic connections, consistent with the segment-wide contraction observed in this species. In addition, activating individual P cells caused asymmetrical body wall contractions in Hirudo and symmetrical body wall contractions in Erpobdella. These results suggest that the different behavioral responses in Erpobdella and Hirudo are partly mediated by interactions among mechanosensory cells

The desmosome and pemphigus

Desmosomes are patch-like intercellular adhering junctions (“maculae adherentes”), which, in concert with the related adherens junctions, provide the mechanical strength to intercellular adhesion. Therefore, it is not surprising that desmosomes are abundant in tissues subjected to significant mechanical stress such as stratified epithelia and myocardium. Desmosomal adhesion is based on the Ca2+-dependent, homo- and heterophilic transinteraction of cadherin-type adhesion molecules. Desmosomal cadherins are anchored to the intermediate filament cytoskeleton by adaptor proteins of the armadillo and plakin families. Desmosomes are dynamic structures subjected to regulation and are therefore targets of signalling pathways, which control their molecular composition and adhesive properties. Moreover, evidence is emerging that desmosomal components themselves take part in outside-in signalling under physiologic and pathologic conditions. Disturbed desmosomal adhesion contributes to the pathogenesis of a number of diseases such as pemphigus, which is caused by autoantibodies against desmosomal cadherins. Beside pemphigus, desmosome-associated diseases are caused by other mechanisms such as genetic defects or bacterial toxins. Because most of these diseases affect the skin, desmosomes are interesting not only for cell biologists who are inspired by their complex structure and molecular composition, but also for clinical physicians who are confronted with patients suffering from severe blistering skin diseases such as pemphigus. To develop disease-specific therapeutic approaches, more insights into the molecular composition and regulation of desmosomes are required

Spike-Triggered Covariance Analysis Reveals Phenomenological Diversity of Contrast Adaptation in the Retina

When visual contrast changes, retinal ganglion cells adapt by adjusting their sensitivity as well as their temporal filtering characteristics. The latter has classically been described by contrast-induced gain changes that depend on temporal frequency. Here, we explored a new perspective on contrast-induced changes in temporal filtering by using spike-triggered covariance analysis to extract multiple parallel temporal filters for individual ganglion cells. Based on multielectrode-array recordings from ganglion cells in the isolated salamander retina, we found that contrast adaptation of temporal filtering can largely be captured by contrast-invariant sets of filters with contrast-dependent weights. Moreover, differences among the ganglion cells in the filter sets and their contrast-dependent contributions allowed us to phenomenologically distinguish three types of filter changes. The first type is characterized by newly emerging features at higher contrast, which can be reproduced by computational models that contain response-triggered gain-control mechanisms. The second type follows from stronger adaptation in the Off pathway as compared to the On pathway in On-Off-type ganglion cells. Finally, we found that, in a subset of neurons, contrast-induced filter changes are governed by particularly strong spike-timing dynamics, in particular by pronounced stimulus-dependent latency shifts that can be observed in these cells. Together, our results show that the contrast dependence of temporal filtering in retinal ganglion cells has a multifaceted phenomenology and that a multi-filter analysis can provide a useful basis for capturing the underlying signal-processing dynamics

Multiplexed electrophoretic systems for the detection and identification of small ions

Capillary electrophoresis (CE) is regarded as a powerful separation technique that is an alternative or complementary technique to more traditional methods such as gel electrophoresis and liquid chromatography. When applied to the separation of inorganic species, capillary electrophoresis still continues to take second place to other competitive techniques such as ion chromatography (IC) and elemental mass spectrometry. CE is often touted as having several obvious advantages over chromatographic techniques (mostly IC) including high resolving power, speed, instrumental simplicity, flexibility and cost‚ÄövÑv™efficiency. On the other hand, CE is frequently cited as having a number of comparative disadvantages such as poor reproducibility and sensitivity. The work undertaken in this thesis describes technical innovations to harness the inherent advantages of CE whilst minimising the disadvantages as part of the development of a system for the rapid determination of common small environmental anions and cations. It is unique in its capability to analyse directly from a sample flow, making it especially attractive for monitoring purposes. To enable a move from a capillary to a chip‚ÄövÑv™based system, simple, low cost techniques for the manufacture of polymeric microchips and the incorporation of detection electrodes were developed using limited resources to provide further improvements in speed and reduce resource consumption. A multiplexed polymeric microchip system was developed employing a novel hydrodynamic injection mechanism to reduce sample matrix effects and injection bias, and to improve the quantitative performance of the system. Finally, a compact multipurpose microfluidic platform is developed to support future research interests

Multiplexed electrophoretic systems for the detection and identification of small ions

Capillary electrophoresis (CE) is regarded as a powerful separation technique that is an alternative or complementary technique to more traditional methods such as gel electrophoresis and liquid chromatography. When applied to the separation of inorganic species, capillary electrophoresis still continues to take second place to other competitive techniques such as ion chromatography (IC) and elemental mass spectrometry. CE is often touted as having several obvious advantages over chromatographic techniques (mostly IC) including high resolving power, speed, instrumental simplicity, flexibility and cost‚ÄövÑv™efficiency. On the other hand, CE is frequently cited as having a number of comparative disadvantages such as poor reproducibility and sensitivity. The work undertaken in this thesis describes technical innovations to harness the inherent advantages of CE whilst minimising the disadvantages as part of the development of a system for the rapid determination of common small environmental anions and cations. It is unique in its capability to analyse directly from a sample flow, making it especially attractive for monitoring purposes. To enable a move from a capillary to a chip‚ÄövÑv™based system, simple, low cost techniques for the manufacture of polymeric microchips and the incorporation of detection electrodes were developed using limited resources to provide further improvements in speed and reduce resource consumption. A multiplexed polymeric microchip system was developed employing a novel hydrodynamic injection mechanism to reduce sample matrix effects and injection bias, and to improve the quantitative performance of the system. Finally, a compact multipurpose microfluidic platform is developed to support future research interests