Reelin is a ligand for lipoprotein receptors

A signaling pathway involving the extracellular protein Reelin and the intracellular adaptor protein Disabled-1 (Dab1) controls cell positioning during mammalian brain development. Here, we demonstrate that Reelin binds directly to lipoprotein receptors, preferably the very low-density lipoprotein receptor (VLDLR) and apolipoprotein E receptor 2 (ApoER2). Binding requires calcium, and it is inhibited in the presence of apoE. Furthermore, the CR-50 monoclonal antibody, which inhibits Reelin function, blocks the association of Reelin with VLDLR. After binding to VLDLR on the cell surface, Reelin is internalized into vesicles. In dissociated neurons, apoE reduces the level of Reelin-induced tyrosine phosphorylation of Dab1. These data suggest that Reelin directs neuronal migration by binding to VLDLR and ApoER2.

Scrambler and yotari disrupt the disabled gene and produce a reeler-like phenotype in mice

Formation of the mammalian brain requires choreographed migration of neurons to generate highly ordered laminar structures such as those in the cortices of the forebrain and the cerebellum. These processes are severely disrupted by mutations in reelin which cause widespread misplacement of neurons and associated ataxia in reeler mice. Reelin is a large extracellular protein secreted by pioneer neurons that coordinates cell positioning during neurodevelopment. Two new autosomal recessive mouse mutations, scramble and yotari have been described that exhibit a phenotype identical to reeler. Here we report that scrambler and yotari arise from mutations in mdab1, a mouse gene related to the Drosophila gene disabled (dab). Both scrambler and yotari mice express mutated forms of mdab1 messenger RNA and little or no mDab1 protein. mDab1 is a phosphoprotein that appears to function as an intracellular adaptor in protein kinase pathways. Expression analysis indicates that mdab1 is expressed in neuronal populations exposed to Reelin. The similar phenotypes of reeler, scrambler, yotari and mdab1 null mice indicate that Reelin and mDab1 function as signalling molecules that regulate cell positioning in the developing brain.

A human RNA polymerase II complex associated with SRB and DNA-repair proteins

We report here the isolation of a human RNA polymerase II complex containing a subset of the basal transcription factors and the human homologues of the yeast SRB (for suppressors of RNA polymerase B) proteins. The complex contains transcriptional coactivators and increases the activation of transcription. In addition, some components of the RNA polymerase II complex participate in DNA repair.

Exciton-to-Dopant Energy Transfer in Mn-Doped Cesium Lead Halide Perovskite Nanocrystals

We report the one-pot synthesis of colloidal Mn-doped cesium lead halide (CsPbX₃) perovskite nanocrystals and efficient intraparticle energy transfer between the exciton and dopant ions resulting in intense sensitized Mn luminescence. Mn-doped CsPbCl₃ and CsPb(Cl/Br)₃ nanocrystals maintained the same lattice structure and crystallinity as their undoped counterparts with nearly identical lattice parameters at ∼0.2% doping concentrations and no signature of phase separation. The strong sensitized luminescence from d-d transition of Mn²⁺ ions upon band-edge excitation of the CsPbX₃ host is indicative of sufficiently strong exchange coupling between the charge carriers of the host and dopant d electrons mediating the energy transfer, essential for obtaining unique properties of magnetically doped quantum dots. Highly homogeneous spectral characteristics of Mn luminescence from an ensemble of Mn-doped CsPbX₃ nanocrystals and well-defined electron paramagnetic resonance spectra of Mn²⁺ in host CsPbX₃ nanocrystal lattices suggest relatively uniform doping sites, likely from substitutional doping at Pb²⁺. These observations indicate that CsPbX₃ nanocrystals, possessing many superior optical and electronic characteristics, can be utilized as a new platform for magnetically doped quantum dots expanding the range of optical, electronic, and magnetic functionality.

Disabled-1 acts downstream of Reelin in a signaling pathway that controls laminar organization in the mammalian brain

Mutation of either reelin (Reln) or disabled-1 (Dab1) results in widespread abnormalities in laminar structures throughout the brain and ataxia in reeler and scrambler mice. Both exhibit the same neuroanatomical defects, including cerebellar hypoplasia with Purkinje cell ectopia and disruption of neuronal layers in the cerebral cortex and hippocampus. Despite these phenotypic similarities, Reln and Dab1 have distinct molecular properties. Reln is a large extracellular protein secreted by Cajal-Retzius cells in the forebrain and by granule neurons in the cerebellum. In contrast, Dab1 is a cytoplasmic protein which has properties of an adapter protein that functions in phosphorylation-dependent intracellular signal transduction. Here, we show that Dab1 participates in the same developmental process as Reln. In scrambler mice, neuronal precursors are unable to invade the preplate of the cerebral cortex and consequently, they do not align within the cortical plate. During development, cells expressing Dab1 are located next to those secreting Reln at critical stages of formation of the cerebral cortex, cerebellum and hippocampus, before the first abnormalities in cell position become apparent in either reeler or scrambler. In reeler, the major populations of displaced neurons contain elevated levels of Dab1 protein, although they express normal levels of Dab1 mRNA. This suggests that Dab1 accumulates in the absence of a Reln-evoked signal. Taken together, these results indicate that Dab1 functions downstream of Reln in a signaling pathway that controls cell positioning in the developing brain.

The HIV-1 long terminal repeat contains an unusual element that induces the synthesis of short RNAs from various mRNA and snRNA promoters

We describe an unusual element that activates the synthesis of short transcripts from a wide variety of mRNA and small nuclear RNA (snRNA) promoters, including the U6 RNA polymerase III promoter. This inducer of short transcripts (IST) is located between positions -5 and +82 relative to the cap site in the HIV-1 LTR. In the presence of IST, the total transcriptional activity of the different promoters is greatly increased, but the resulting additional RNA molecules are short, ending around position +60. IST is not the RNA target (TAR) for Tat trans-activation; however, because it relies entirely on cellular factors for activity, IST may serve to provide abundant RNA targets for Tat trans-activation without a requirement for full-length viral mRNA expression.

Reconstitution of human TFIIA activity from recombinant polypeptides: a role in TFIID-mediated transcription

Human TFIIA activity is composed of three subunits (alpha, beta, gamma). Here we report the isolation of a human cDNA clone encoding the gamma-subunit and the reconstitution of TFIIA activity from recombinant polypeptides (holo-TFIIA). Protein-protein interaction analysis established that the beta and gamma subunits of TFIIA interact with the TBP component of TFIID. The alpha-subunit is recruited into the complex by association with the gamma-subunit. Functional studies indicate that recombinant TFIIA stimulates basal TFIID-dependent transcription but is without effect on TBP-dependent transcription. Our studies indicate that TFIIA not only functions by physically removing negative components present in TFIID (antirepression), as demonstrated previously, but that it can stimulate basal transcription through components of the TFIID complex. Holo-TFIIA also stimulated activation of transcription in vitro as well as in vivo in transfected HeLa cells.

Cytogenetic and molecular studies of trisomy 13

Chromosome heteromorphisms, restriction fragment length polymorphisms, or both were used to study the parental origin of 33 cases of simple trisomy 13 and eight cases of translocation trisomy 13. The most common origin for the simple trisomies was non-disjunction at maternal meiosis I, while for the translocations an equal number of paternally and maternally derived cases was observed. In seven of the simple trisomies, information was obtained from both the cytogenetic and molecular markers, making it possible to study recombination between the two non-disjoined chromosomes. Five of the seven cases involved errors at meiosis I, with crossing over being detected in two of three cases of maternal origin and in one of two cases of paternal origin. This indicates that absence of recombination because of pairing failure is unlikely to be of major importance in the genesis of trisomy 13.

Au Exchange or Au Deposition: Dual Reaction Pathways in Au-CsPbBr3 Heterostructure Nanoparticles

We have designed a facile synthetic strategy for the selective deposition of Au metal on all-inorganic CsPbBr₃ perovskite nanocrystals that includes the addition of PbBr₂ salt along with AuBr₃ salt. PbBr₂ is necessary because the addition of Au³⁺ to solutions of CsPbBr₃ nanocrystals otherwise results in the exchange of Au³⁺ ions from solution with Pb²⁺ cations within the nanocrystal lattice to produce Cs₂Au^IAu^IIIBr₆ nanocrystals with a tetragonal crystal structure and a band gap of about 1.6 eV, in addition to Au metal deposition. Including excess Pb²⁺ ions in solution prevents the exchange reaction. Au metal deposits on the surface of the nanocrystals to produce the Au-CsPbBr₃ heterostructure nanoparticles with an Au particle diameter determined by the Au³⁺ ion concentration. Fluorescence quenching caused by Au deposition monotonically increases with deposition size, but the fluorescence quantum yield (QY) is significantly greater than if any cation exchange has occurred. An optimized synthesis can produce Au-CsPbBr₃ nanoparticles with 70% QY and no evidence of cation exchange.

Laterality effects in judgment of the identity and position of letters: a signal detection analysis

In two experiments subjects received 100 ms tachistoscopic presentations, either to left or right of fixation, of a rectangular matrix of 12 cells. On each trial three cells were filled, each with a different symbol drawn from a set of 12 letters and digits. In one (the “letter” experiment) subjects had to decide whether a particular letter (nominated at the end of the trial) had been one of the three presented. In a second (the “position” experiment) they had to decide whether a cell in the matrix (again nominated at the end of the trial) had been one of those that contained a symbol. Judgments were made on a four-point rating scale, and measures of sensitivity and response bias were calculated. In the letter experiment sensitivity was greater for presentations to right of fixation, and in the position experiment for those to left.

Self-Assembled Epitaxial Au-Oxide Vertically Aligned Nanocomposites for Nanoscale Metamaterials

Metamaterials made of nanoscale inclusions or artificial unit cells exhibit exotic optical properties that do not exist in natural materials. Promising applications, such as super-resolution imaging, cloaking, hyperbolic propagation, and ultrafast phase velocities have been demonstrated based on mostly micrometer-scale metamaterials and few nanoscale metamaterials. To date, most metamaterials are created using costly and tedious fabrication techniques with limited paths toward reliable large-scale fabrication. In this work, we demonstrate the one-step direct growth of self-assembled epitaxial metal-oxide nanocomposites as a drastically different approach to fabricating large-area nanostructured metamaterials. Using pulsed laser deposition, we fabricated nanocomposite films with vertically aligned gold (Au) nanopillars (∼20 nm in diameter) embedded in various oxide matrices with high epitaxial quality. Strong, broad absorption features in the measured absorbance spectrum are clear signatures of plasmon resonances of Au nanopillars. By tuning their densities on selected substrates, anisotropic optical properties are demonstrated via angular dependent and polarization resolved reflectivity measurements and reproduced by full-wave simulations and effective medium theory. Our model predicts exotic properties, such as zero permittivity responses and topological transitions. Our studies suggest that these self-assembled metal-oxide nanostructures provide an exciting new material platform to control and enhance optical response at nanometer scales.

Size- and temperature-dependent photoluminescence spectra of strongly confined CsPbBr3 quantum dots

Lead-halide perovskite nanocrystals (NCs) are receiving much attention as a potential high-quality source of photons due to their superior luminescence properties in comparison to other semiconductor NCs. To date, research has focused mostly on NCs with little or no quantum confinement. Here, we measured the size- and temperature-dependent photoluminescence (PL) from strongly confined CsPbBr₃ quantum dots (QDs) with highly uniform size distributions, and examined the factors determining the evolution of the energy and linewidth of the PL with varying temperature and QD size. Compared to the extensively studied II-VI QDs, the spectral position of PL from CsPbBr₃ QDs shows an opposite dependence on temperature, with weaker dependence overall. On the other hand, the PL linewidth is much more sensitive to the temperature and size of the QDs compared to II-VI QDs, indicating much stronger coupling of excitons to the vibrational degrees of freedom both in the lattice and at the surface of the QDs.

Characterization of the inducer of short transcripts, a human immunodeficiency virus type 1 transcriptional element that activates the synthesis of short RNAs

The inducer of short transcripts, or IST, is an unusual transcriptional element located downstream of the human immunodeficiency virus type 1 (HIV-1) promoter. IST activates HIV-1 transcription, but the resulting RNAs are short and end at approximately position +59. IST, therefore, appears to promote the formation of transcription complexes that are unable to elongate efficiently. This activity contrasts with that of TAR, the target for Tat trans-activation, which upon binding of the viral protein Tat promotes the formation of transcription complexes capable of efficient elongation through the entire viral genome. We have localized and characterized the IST element. Our results indicate that IST is located mainly between positions -5 and +26, although the sequences from positions +40 to +59 also contribute to IST activity. Unlike TAR, which is an RNA element, IST appears to be a DNA element. Thus, the HIV-1 R region is a complex regulatory region with RNA and DNA elements that promote the formation of transcription complexes with different elongation properties.

Low levels of ill health among elderly non-consulters in general practice

The characteristics of random samples of elderly patients (over 65 years of age), designated as consulters (n = 200) and non-consulters (n = 196), in a group general practice were compared using a postal questionnaire that was validated by comparison with findings by general practitioners in a random sample of 58 responders. A response rate of 90% was obtained, and all non-responders were visited by their general practitioner. The questionnaire had a sensitivity of 79% and a specificity of 82% when compared with general practitioner findings. The use of hospital and social services by non-consulters was low in this practice. Measures of disability and state of health showed that non-consulters were a fit group of the aged. Case finding for problems among elderly people should initially be confined to consulters, who have a high prevalence of problems. Non-consulters are a low risk group that can be assessed only with special effort and extra resources. Once an effective case finding system has been developed it might then be reasonable to consider ways of finding the few patients who have problems but do not consult their doctor.

Psychiatric assessment in remote Aboriginal communities

OBJECTIVE

The objective of this study was to describe the psychiatric assessment of Aboriginal patients from remote Aboriginal communities in Central Australia.

METHOD

The method consisted of a summary of the experiences gained during a dissertation year placement as senior registrar with the Northern Territory Remote Area Mental Health Team.

RESULTS

Remote area Aboriginal psychiatry entails learning a whole new set of skills in terms of history taking and the mental state examination, a knowledge of the importance of extended kinship ties and cultural issues, the use of Aboriginal mental health workers as partners in assessing and managing patients via their families and accepting referrals from a wide range of sources.

CONCLUSIONS

Working on a service providing psychiatric care to remote area Aboriginal communities can be a deeply rewarding personal and professional experience.

Genetic and morphological features of human iPSC-derived neurons with chromosome 15q11.2 (BP1-BP2) deletions

BACKGROUND

Copy number variation on chromosome 15q11.2 (BP1-BP2) causes deletion of CYFIP1, NIPA1, NIPA2 and TUBGCP5; it also affects brain structure and elevates risk for several neurodevelopmental disorders that are associated with dendritic spine abnormalities. In rodents, altered cyfip1 expression changes dendritic spine morphology, motivating analyses of human neuronal cells derived from iPSCs (iPSC-neurons).

METHODS

iPSCs were generated from a mother and her offspring, both carrying the 15q11.2 (BP1-BP2) deletion, and a non-deletion control. Gene expression in the deletion region was estimated using quantitative real-time PCR assays. Neural progenitor cells (NPCs) and iPSC-neurons were characterized using immunocytochemistry.

RESULTS

CYFIP1, NIPA1, NIPA2 and TUBGCP5 gene expression was lower in iPSCs, NPCs and iPSC-neurons from the mother and her offspring in relation to control cells. CYFIP1 and PSD95 protein levels were lower in iPSC-neurons derived from the CNV bearing individuals using Western blot analysis. At 10 weeks post-differentiation, iPSC-neurons appeared to show dendritic spines and qualitative analysis suggested that dendritic morphology was altered in 15q11.2 deletion subjects compared with control cells.

CONCLUSIONS

The 15q11.2 (BP1-BP2) deletion is associated with reduced expression of four genes in iPSC-derived neuronal cells; it may also be associated altered iPSC-neuron dendritic morphology.

The utility of spectral karyotyping in the cytogenetic analysis of newly diagnosed pediatric acute lymphoblastic leukemia

We applied multicolor spectral karyotyping (SKY) to a panel of 29 newly diagnosed pediatric pre B-cell ALLs with normal and abnormal G-banded karyotypes to identify cryptic translocations and define complex chromosomal rearrangements. By this method, it was possible to define all add chromosomes in six cases, a cryptic t(12;21)(p13;q11) translocation in six cases, marker chromosomes in two cases and refine the misidentified aberrations by G-banding in two cases. In addition, we identified five novel non-recurrent translocations - t(2;9)(p11.2;p13), t(2;22) (p11.2;q11.2), t(6;8)(p12;p11), t(12;14)(p13;q32) and t(X;8)(p22.3;q?). Of these translocations, t(2;9), t(2;22) and t(12;14) were identified by G-banding analysis and confirmed by SKY. We characterized a t(12;14)( p13;q32) translocation by FISH, and identified a fusion of TEL with IGH for the first time in ALL. We identified a rearrangement of PAX5 locus in a case with t(2;9)(p11.2;p13) by FISH and defined the breakpoint telomeric to PAX5 in der(9)t(3;9)(?;p13). These studies demonstrate the utility of using SKY in combination with G-banding and FISH to augment the precision with which chromosomal aberrations may be identified in tumor cells.

A psychology based approach for longitudinal development in cognitive robotics

A major challenge in robotics is the ability to learn, from novel experiences, new behavior that is useful for achieving new goals and skills. Autonomous systems must be able to learn solely through the environment, thus ruling out a priori task knowledge, tuning, extensive training, or other forms of pre-programming. Learning must also be cumulative and incremental, as complex skills are built on top of primitive skills. Additionally, it must be driven by intrinsic motivation because formative experience is gained through autonomous activity, even in the absence of extrinsic goals or tasks. This paper presents an approach to these issues through robotic implementations inspired by the learning behavior of human infants. We describe an approach to developmental learning and present results from a demonstration of longitudinal development on an iCub humanoid robot. The results cover the rapid emergence of staged behavior, the role of constraints in development, the effect of bootstrapping between stages, and the use of a schema memory of experiential fragments in learning new skills. The context is a longitudinal experiment in which the robot advanced from uncontrolled motor babbling to skilled hand/eye integrated reaching and basic manipulation of objects. This approach offers promise for further fast and effective sensory-motor learning techniques for robotic learning.

Transcriptional activation. Tuning-up transcription

Eukaryotic transcription is a complex process, and recent results identify multiple steps that need to be stimulated to activate transcription, one of which is a change in conformation of the general transcription factor TFIIB.

A Correlation between Blood Flow Volume and Ultrasonic Doppler Wave Forms in the Study of Valve Efficiency

Objective:

To demonstrate a significant correlation between the Doppler waveform and blood flow volume in the assessment of valve efficiency. In particular the objective was to ratify use of the ‘area index’ of the wave form.

Design:

Pearson's correlation and zero line assessment were used. Using a phantom, multiple tests were performed so that a wide spectrum of flow volumes could be compared with corresponding Doppler waves.

Setting:

Private diagnostic imaging clinic with vascular surgical association.

Main outcome measures:

The hypothesis was that there should be a significant correlation between the Doppler wave and the blood flow volume and, in particular, the Doppler area.

Results:

The Doppler wave index EId demonstrated the highest correlation coefficient ( r = 0.97, p<0.01) when compared with the volume index EIV.

Conclusion:

While there is a strong correlation between EId and flow volume, additional study is needed to determine its place in the clinical setting.

The role of mid-gap states in all-inorganic CsPbBr3 nanoparticle one photon up-conversion

CsPbBr₃ nanoparticles that have been treated with NH₄SCN to produce essentially trap-free surfaces show an increase of one photon up-conversion quantum yield with little change to the up-conversion energy of activation, as estimated using an Arrhenius analysis.

Ethical issues in the forced transfusion of Jehovah's Witness children

This paper examines the views of Jehovah's Witnesses in regards to their refusal of blood transfusions for themselves and their children. After setting out the legal framework society presently has in place for dealing with such refusals, the paper reviews the ethics literature that justifies the intervention by the State to force the transfusion of Jehovah's Witness children. It is claimed that the arguments such literature develops are seriously problematic. A different approach is suggested.

IgA myeloma of donor origin arising 7 years after allogeneic renal transplant

We report the case of a 38-year-old man who developed IgA myeloma of donor origin 7 years after allogeneic renal transplant. The diagnosis of multiple myeloma was unequivocal and based on positive results from serum electrophoresis, skeletal survey and bone marrow investigations. The donor origin of the myeloma cells was confirmed by DNA fingerprinting. We believe this is the first reported case of disseminated multiple myeloma of donor origin developing after allogeneic renal transplant and, as such, gives some insight into the natural history and biology of the disease.