214 research outputs found
The Morphological Identity of Insect Dendrites
Dendrite morphology, a neuron's anatomical fingerprint, is a
neuroscientist's asset in unveiling organizational principles in the
brain. However, the genetic program encoding the morphological identity of a
single dendrite remains a mystery. In order to obtain a formal understanding of
dendritic branching, we studied distributions of morphological parameters in a
group of four individually identifiable neurons of the fly visual system. We
found that parameters relating to the branching topology were similar throughout
all cells. Only parameters relating to the area covered by the dendrite were
cell type specific. With these areas, artificial dendrites were grown based on
optimization principles minimizing the amount of wiring and maximizing synaptic
democracy. Although the same branching rule was used for all cells, this yielded
dendritic structures virtually indistinguishable from their real counterparts.
From these principles we derived a fully-automated model-based neuron
reconstruction procedure validating the artificial branching rule. In
conclusion, we suggest that the genetic program implementing neuronal branching
could be constant in all cells whereas the one responsible for the dendrite
spanning field should be cell specific
In silico characterization of the family of PARP-like poly(ADP-ribosyl)transferases (pARTs)
BACKGROUND: ADP-ribosylation is an enzyme-catalyzed posttranslational protein modification in which mono(ADP-ribosyl)transferases (mARTs) and poly(ADP-ribosyl)transferases (pARTs) transfer the ADP-ribose moiety from NAD onto specific amino acid side chains and/or ADP-ribose units on target proteins. RESULTS: Using a combination of database search tools we identified the genes encoding recognizable pART domains in the public genome databases. In humans, the pART family encompasses 17 members. For 16 of these genes, an orthologue exists also in the mouse, rat, and pufferfish. Based on the degree of amino acid sequence similarity in the catalytic domain, conserved intron positions, and fused protein domains, pARTs can be divided into five major subgroups. All six members of groups 1 and 2 contain the H-Y-E trias of amino acid residues found also in the active sites of Diphtheria toxin and Pseudomonas exotoxin A, while the eleven members of groups 3 – 5 carry variations of this motif. The pART catalytic domain is found associated in Lego-like fashion with a variety of domains, including nucleic acid-binding, protein-protein interaction, and ubiquitylation domains. Some of these domain associations appear to be very ancient since they are observed also in insects, fungi, amoebae, and plants. The recently completed genome of the pufferfish T. nigroviridis contains recognizable orthologues for all pARTs except for pART7. The nearly completed albeit still fragmentary chicken genome contains recognizable orthologues for twelve pARTs. Simpler eucaryotes generally contain fewer pARTs: two in the fly D. melanogaster, three each in the mosquito A. gambiae, the nematode C. elegans, and the ascomycete microfungus G. zeae, six in the amoeba E. histolytica, nine in the slime mold D. discoideum, and ten in the cress plant A. thaliana. GenBank contains two pART homologues from the large double stranded DNA viruses Chilo iridescent virus and Bacteriophage Aeh1 and only a single entry (from V. cholerae) showing recognizable homology to the pART-like catalytic domains of Diphtheria toxin and Pseudomonas exotoxin A. CONCLUSION: The pART family, which encompasses 17 members in the human and 16 members in the mouse, can be divided into five subgroups on the basis of sequence similarity, phylogeny, conserved intron positions, and patterns of genetically fused protein domains
T Cells of Different Developmental Stages Differ in Sensitivity to Apoptosis Induced by Extracellular NAD
Extracellular nucleotides such as ATP and NAD can profoundly affect the functions of lymphocytes, macrophages, and other cells. We have recently shown that extracellular NAD induces rapid apoptosis in naive T cells by a mechanism involving the ADP-ribosylation of cell surface molecules. In the present paper, we describe that T cells of different developmental stages differ in their sensitivity to NAD-induced apoptosis. Thymocytes were less susceptible than peripheral lymph node T cells, and freshly activated cells were more resistant than resting cells. Sensitivity to NAD-induced apoptosis generally correlated with expression of the ADP-ribosyltransferase ART2.2, which is not expressed on thymocytes and shed from peripheral T cells upon activation. Our findings suggest that NAD-induced apoptosis does not play a role during thymic selection of T cells, but rather may play a role by preventing the activation of unwanted bystander T cells during an immune response, and thus may participate in the control of autoimmunity
Monitoring the expression of purinoceptors and nucleotide-metabolizing ecto-enzymes with antibodies directed against proteins in native conformation
Following their release from cells, ATP and NAD, the universal currencies of energy metabolism, function as extracellular signalling molecules. Mammalian cells express numerous purinoceptors, i.e., the nucleotide-gated P2X ion channels and the G-protein-coupled P2Y receptors. Signalling through purinoceptors is controlled by nucleotide-metabolizing ecto-enzymes, which regulate the availability of extracellular nucleotides. These enzymes include ecto-nucleoside triphosphate diphosphohydrolases (ENTPD, CD39 family) and ecto-nucleotide pyrophosphatase/phosphodiesterases (ENPP, CD203 family). Investigation of these receptors and enzymes has been hampered by the lack of available antibodies, especially ones that recognize these proteins in their native conformation. This study reports the use of genetic immunization to generate such antibodies against P2X1, P2X4, P2X7, ENTPD1, ENPTD2, ENPTD5, ENPTD6, ENPP2, ENPP3, ENPP4, ENPP5, and ENPP6. Genetic immunization ensures expression of the native protein by the cells of the immunized animal and yields antibodies directed against proteins in native conformation (ADAPINCs). Such antibodies are especially useful for immunofluorescence and immunoprecipitation analyses, whereas antibodies against synthetic peptides usually function well only in Western-blot analyses. Here we illustrate the utility of the new antibodies to monitor the cell surface expression of and to purify some key players of purinergic signalling
Polyglycerol coated polypropylene surfaces for protein and bacteria resistance
Polyglycerol (PG) coated polypropylene (PP) films were synthesized in a two-
step approach that involved plasma bromination and subsequently grafting
hyperbranched polyglycerols with very few amino functionalities. The influence
of different molecular weights and density of reactive linkers were
investigated for the grafted PGs. Longer bromination times and higher amounts
of linkers on the surface afforded long-term stability. The protein adsorption
and bacteria attachment of the PP-PG films were studied. Their extremely low
amine content proved to be beneficial for preventing bacteria attachment
The Morphological Identity of Insect Dendrites
Dendrite morphology, a neuron's anatomical fingerprint, is a
neuroscientist's asset in unveiling organizational principles in the
brain. However, the genetic program encoding the morphological identity of a
single dendrite remains a mystery. In order to obtain a formal understanding of
dendritic branching, we studied distributions of morphological parameters in a
group of four individually identifiable neurons of the fly visual system. We
found that parameters relating to the branching topology were similar throughout
all cells. Only parameters relating to the area covered by the dendrite were
cell type specific. With these areas, artificial dendrites were grown based on
optimization principles minimizing the amount of wiring and maximizing synaptic
democracy. Although the same branching rule was used for all cells, this yielded
dendritic structures virtually indistinguishable from their real counterparts.
From these principles we derived a fully-automated model-based neuron
reconstruction procedure validating the artificial branching rule. In
conclusion, we suggest that the genetic program implementing neuronal branching
could be constant in all cells whereas the one responsible for the dendrite
spanning field should be cell specific
On-Surface Carbon Nitride Growth from Polymerization of 2,5,8-Triazido-s-heptazine
Carbon nitrides have recently come into focus for photo- and thermal
catalysis, both as support materials for metal nanoparticles as well as
photocatalysts themselves. While many approaches for the synthesis of
three-dimensional carbon nitride materials are available, only top-down
approaches by exfoliation of powders lead to thin film flakes of this
inherently two-dimensional material. Here, we describe an in situ on-surface
synthesis of monolayer 2D carbon nitride films, as a first step towards precise
combination with other 2D materials. Starting with a single monomer precursor,
we show that 2,5,8-triazido-s-heptazine (TAH) can be evaporated intact,
deposited on a single crystalline Au(111) or graphite support, and activated
via azide decomposition and subsequent coupling to form a covalent
polyheptazine network. We demonstrate that the activation can occur in three
pathways, via electrons (X-ray illumination), photons (UV illumination) and
thermally. Our work paves the way to coat materials with extended carbon
nitride networks which are, as we show, stable under ambient conditions
Multivalent grafting of hyperbranched oligo- and polyglycerols shielding rough membranes to mediate hemocompatibility
Hemocompatible materials are needed for internal and extracorporeal biomedical
applications, which should be realizable by reducing protein and thrombocyte
adhesion to such materials. Polyethers have been demonstrated to be highly
efficient in this respect on smooth surfaces. Here, we investigate the
grafting of oligo- and polyglycerols to rough poly(ether imide) membranes as a
polymer relevant to biomedical applications and show the reduction of protein
and thrombocyte adhesion as well as thrombocyte activation. It could be
demonstrated that, by performing surface grafting with oligo- and
polyglycerols of relatively high polydispersity (>1.5) and several reactive
groups for surface anchoring, full surface shielding can be reached, which
leads to reduced protein adsorption of albumin and fibrinogen. In addition,
adherent thrombocytes were not activated. This could be clearly shown by
immunostaining adherent proteins and analyzing the thrombocyte covered area.
The presented work provides an important strategy for the development of
application relevant hemocompatible 3D structured materials
Single domain antibodies: promising experimental and therapeutic tools in infection and immunity
Antibodies are important tools for experimental research and medical applications. Most antibodies are composed of two heavy and two light chains. Both chains contribute to the antigen-binding site which is usually flat or concave. In addition to these conventional antibodies, llamas, other camelids, and sharks also produce antibodies composed only of heavy chains. The antigen-binding site of these unusual heavy chain antibodies (hcAbs) is formed only by a single domain, designated VHH in camelid hcAbs and VNAR in shark hcAbs. VHH and VNAR are easily produced as recombinant proteins, designated single domain antibodies (sdAbs) or nanobodies. The CDR3 region of these sdAbs possesses the extraordinary capacity to form long fingerlike extensions that can extend into cavities on antigens, e.g., the active site crevice of enzymes. Other advantageous features of nanobodies include their small size, high solubility, thermal stability, refolding capacity, and good tissue penetration in vivo. Here we review the results of several recent proof-of-principle studies that open the exciting perspective of using sdAbs for modulating immune functions and for targeting toxins and microbes.Centro de InvestigaciĂłn y Desarrollo en Fermentaciones Industriale
Comparing quantitative image parameters between animal and clinical CT-scanners: a translational phantom study analysis
PurposeThis study compares phantom-based variability of extracted radiomics features from scans on a photon counting CT (PCCT) and an experimental animal PET/CT-scanner (Albira II) to investigate the potential of radiomics for translation from animal models to human scans. While oncological basic research in animal PET/CT has allowed an intrinsic comparison between PET and CT, but no 1:1 translation to a human CT scanner due to resolution and noise limitations, Radiomics as a statistical and thus scale-independent method can potentially close the critical gap.MethodsTwo phantoms were scanned on a PCCT and animal PET/CT-scanner with different scan parameters and then the radiomics parameters were extracted. A Principal Component Analysis (PCA) was conducted. To overcome the limitation of a small dataset, a data augmentation technique was applied. A Ridge Classifier was trained and a Feature Importance- and Cluster analysis was performed.ResultsPCA and Cluster Analysis shows a clear differentiation between phantom types while emphasizing the comparability of both scanners. The Ridge Classifier exhibited a strong training performance with 93% accuracy, but faced challenges in generalization with a test accuracy of 62%.ConclusionThese results show that radiomics has great potential as a translational tool between animal models and human routine diagnostics, especially using the novel photon counting technique. This is another crucial step towards integration of radiomics analysis into clinical practice
- …