A biometric study of some hybridizing Crataegus populations in Denmark

Crataegus curvisepala Lindm., C. laevigata (Poiret) DC. and C. monogyna Jacq. (Rosaceae) form hybrid complexes in Denmark due to introgression. C. palmstruchii Lindm. seems to be variously introgressed individuals of C. laevigata. C. eremitagensis Raunk., C. raavadensis Raunk. and C. schumacheri Raunk. apparently belong to C. curvisepala x laevigata. The delimitation between C. curvisepala x laevigata and C. laevigata x monogyna is discussed.     

Solubilization and characterization of active neuropeptide Y receptors from rabbit kidney

Active neuropeptide Y receptors were solubilized from rabbit kidney membranes using the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid (CHAPS). In membrane fragments and soluble extracts neuropeptide Y binding was time dependent, saturable, reversible, and of high affinity. Scatchard analysis of equilibrium binding data indicated a single class of binding sites with respective KD and Bmax values of 0.09 nM and 530 fmol/mg of protein for the membrane-bound receptors and 0.10 nM and 1585 fmol/mg of protein for the soluble receptors. Neuropeptide Y binding was specifically inhibited by the nonhydrolyzable GTP analog guanosine 5'-O-(3-thiotriphosphate) in a concentration-dependent manner, with IC50 values of 28 and 0.14 microM for membrane-bound and soluble receptors, respectively, suggesting that neuropeptide Y receptors are functionally coupled to GTP-binding regulatory proteins. Cross-linking studies were performed with the heterobifunctional N-hydroxysuccinimidyl-4-azidobenzoate and the monofunctional neuropeptide Y derivative, azidobenzoyl and led to the identification of a 100 kDa peptide that should represent the covalently labeled neuropeptide Y receptor.     

On the history of nuclear matrix manifestation

The nonchromatin proteinous residue of the cell nucleus was revealed in our laboratory as early as in 1948 and then identified by light and electron microscopy as residual nucleoli,intranuclear network and nuclear envelope before 1960,This structure termed afterwards as “nuclear residue“,“nuclear skeleton“,“nuclear cage“,“nuclear carcass“etc.,was much later(in 1974) isolated,studied and entitled as “nuclear matrix“ by Berezney and Coffey,to whom the discovery of this residual structure is often wronly ascribed.The real history of nuclear matrix manifestation is reported in this paper.     

Does urbanization affect selective pressures and life‐history strategies in the common blackbird (Turdus merula L.)?

Urbanization, one of the most extreme land‐use alterations, is currently spreading, and the number of species confronting these changes is increasing. However, contradictory results of previous studies impede a clear interpretation of which selective pressure (nest predation or food limitation) is more important in urban habitats compared with natural situations, and whether birds can confront them by adjusting their life‐history strategies. We investigated life‐history syndromes of three common blackbird (Turdus merula) populations differing in their human influence (urban, rural, and woodland). We analysed daily nest predation and nestling starvation rates to assess the relative importance of these selection pressures in each habitat. Simultaneously, several life‐history traits were investigated to determine if T. merula seem adapted to their main source of selection. Food limitation was more important in the city, whereas nest predation was the most important selective force in the forest. The rural habitat was characterized by an intermediate influence of these two factors. Life‐history syndromes, as the covariation of a suite of traits, confirmed these results because T. merula seem well adapted to the main cause of selection in each habitat. Our results are consistent with urbanization imposing new challenges on birds, and that they adaptively respond to them. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 759–766.     

Unsteady wall shear stress in a distensible tube

An asymptotic expression of the wall shear stress (WSS) in an elastic tube is deduced for small values of the Womersley parameter. In the case of a rigid tube this asymptotic expression is shown to compare better with the exact solution than Poiseuille's or Lambossy's approximations. Its integration in a one-dimensional model of the internal carotid artery blood flow predicts more marked systolic and less marked diastolic WSS than those predicted by the commonly used Poiseuille's approximation.     

Midline Signalling Systems Direct the Formation of a Neural Map by Dendritic Targeting in the Drosophila Motor System

A fundamental strategy for organising connections in the nervous system is the formation of neural maps. Map formation has been most intensively studied in sensory systems where the central arrangement of axon terminals reflects the distribution of sensory neuron cell bodies in the periphery or the sensory modality. This straightforward link between anatomy and function has facilitated tremendous progress in identifying cellular and molecular mechanisms that underpin map development. Much less is known about the way in which networks that underlie locomotion are organised. We recently showed that in the Drosophila embryo, dendrites of motorneurons form a neural map, being arranged topographically in the antero-posterior axis to represent the distribution of their target muscles in the periphery. However, the way in which a dendritic myotopic map forms has not been resolved and whether postsynaptic dendrites are involved in establishing sets of connections has been relatively little explored. In this study, we show that motorneurons also form a myotopic map in a second neuropile axis, with respect to the ventral midline, and they achieve this by targeting their dendrites to distinct medio-lateral territories. We demonstrate that this map is “hard-wired”; that is, it forms in the absence of excitatory synaptic inputs or when presynaptic terminals have been displaced. We show that the midline signalling systems Slit/Robo and Netrin/Frazzled are the main molecular mechanisms that underlie dendritic targeting with respect to the midline. Robo and Frazzled are required cell-autonomously in motorneurons and the balance of their opposite actions determines the dendritic target territory. A quantitative analysis shows that dendritic morphology emerges as guidance cue receptors determine the distribution of the available dendrites, whose total length and branching frequency are specified by other cell intrinsic programmes. Our results suggest that the formation of dendritic myotopic maps in response to midline guidance cues may be a conserved strategy for organising connections in motor systems. We further propose that sets of connections may be specified, at least to a degree, by global patterning systems that deliver pre- and postsynaptic partner terminals to common “meeting regions.”     

Quantification of the magnification and distortion effects of a pediatric flexible video-bronchoscope

Background

Flexible video bronchoscopes, in particular the Olympus BF Type 3C160, are commonly used in pediatric respiratory medicine. There is no data on the magnification and distortion effects of these bronchoscopes yet important clinical decisions are made from the images. The aim of this study was to systematically describe the magnification and distortion of flexible bronchoscope images taken at various distances from the object.

Methods

Using images of known objects and processing these by digital video and computer programs both magnification and distortion scales were derived.

Results

Magnification changes as a linear function between 100 mm (×1) and 10 mm (×9.55) and then as an exponential function between 10 mm and 3 mm (×40) from the object. Magnification depends on the axis of orientation of the object to the optic axis or geometrical axis of the bronchoscope. Magnification also varies across the field of view with the central magnification being 39% greater than at the periphery of the field of view at 15 mm from the object. However, in the paediatric situation the diameter of the orifices is usually less than 10 mm and thus this limits the exposure to these peripheral limits of magnification reduction. Intraclass correlations for measurements and repeatability studies between instruments are very high, r = 0.96. Distortion occurs as both barrel and geometric types but both types are heterogeneous across the field of view. Distortion of geometric type ranges up to 30% at 3 mm from the object but may be as low as 5% depending on the position of the object in relation to the optic axis.

Conclusion

We conclude that the optimal working distance range is between 40 and 10 mm from the object. However the clinician should be cognisant of both variations in magnification and distortion in clinical judgements.     

MicroRNA-8 promotes robust motor axon targeting by coordinate regulation of cell adhesion molecules during synapse development

Neuronal connectivity and specificity rely upon precise coordinated deployment of multiple cell-surface and secreted molecules. MicroRNAs have tremendous potential for shaping neural circuitry by fine-tuning the spatio-temporal expression of key synaptic effector molecules. The highly conserved microRNA miR-8 is required during late stages of neuromuscular synapse development in Drosophila. However, its role in initial synapse formation was previously unknown. Detailed analysis of synaptogenesis in this system now reveals that miR-8 is required at the earliest stages of muscle target contact by RP3 motor axons. We find that the localization of multiple synaptic cell adhesion molecules (CAMs) is dependent on the expression of miR-8, suggesting that miR-8 regulates the initial assembly of synaptic sites. Using stable isotope labelling in vivo and comparative mass spectrometry, we find that miR-8 is required for normal expression of multiple proteins, including the CAMs Fasciclin III (FasIII) and Neuroglian (Nrg). Genetic analysis suggests that Nrg and FasIII collaborate downstream of miR-8 to promote accurate target recognition. Unlike the function of miR-8 at mature larval neuromuscular junctions, at the embryonic stage we find that miR-8 controls key effectors on both sides of the synapse. MiR-8 controls multiple stages of synapse formation through the coordinate regulation of both pre- and postsynaptic cell adhesion proteins.     

Congenic strain analysis reveals genes that are rapidly evolving components of a prezygotic isolation mechanism mediating incipient reinforcement

Two decades ago, we developed a congenic strain of Mus musculus, called b-congenic, by replacing the androgen-binding protein Abpa27(a) allele in the C3H/HeJ genome with the Abpa27(b) allele from DBA/2J. We and other researchers used this b-congenic strain and its C3H counterpart, the a-congenic strain, to test the hypothesis that, given the choice between signals from two strains with different a27 alleles on the same genetic background, test subjects would prefer the homosubspecific one. It was our purpose in undertaking this study to characterize the segment transferred from DBA to the C3H background in producing the b-congenic strain on which a role for ABPA27 in behavior has been predicated. We determined the size of the chromosome 7 segment transferred from DBA and the genes it contains that might influence preference. We found that the "functional" DBA segment is about 1% the size of the mouse haploid genome and contains at least 29 genes expressed in salivary glands, however, only three of these encode proteins identified in the mouse salivary proteome. At least two of the three genes Abpa27, Abpbg26 and Abpbg27 encoding the subunits of androgen-binding protein ABP dimers evolved under positive selection and the third one may have also. In the sense that they are subunits of the same two functional entities, the ABP dimers, we propose that their evolutionary histories might not be independent of each other.