Molecular Identity (molecular + identity)

Distribution by Scientific Domains

Selected Abstracts

Molecular Identity of the M-Channel

EPILEPSIA, Issue 8 2000
David McKinnon
No abstract is available for this article. [source]

Apparent mitochondrial asymmetry in Xenopus eggs

Natalia Volodina
Abstract Cell polarity is manifest along the animal/vegetal axis in eggs of the frog, Xenopus laevis. Along this axis, maternal cytoplasmic components are asymmetrically distributed and are thought to underlie specification of distinct cell fates. To ascertain the molecular identities of such cytoplasmic components, we have used a monoclonal antibody that specifically stains the vegetal hemisphere of Xenopus eggs. The antigenic protein Vp67 (vegetal protein of 67 kDa) was identified through purification and cloning as a Xenopus homolog of the mitochondrial protein dihydrolipoamide acetyltransferase, a component of the pyruvate dehydrogenase complex. The identification of Vp67 as a mitochondrial protein could indicate that populations of mitochondria are asymmetrically distributed in Xenopus eggs. Developmental Dynamics 226:654,662, © 2003 Wiley-Liss, Inc. [source]

MapQuant: Open-source software for large-scale protein quantification

Kyriacos C. Leptos
Abstract Whole-cell protein quantification using MS has proven to be a challenging task. Detection efficiency varies significantly from peptide to peptide, molecular identities are not evident a,priori, and peptides are dispersed unevenly throughout the multidimensional data space. To overcome these challenges we developed an open-source software package, MapQuant, to quantify comprehensively organic species detected in large MS datasets. MapQuant treats an LC/MS experiment as an image and utilizes standard image processing techniques to perform noise filtering, watershed segmentation, peak finding, peak fitting, peak clustering, charge-state determination and carbon-content estimation. MapQuant reports abundance values that respond linearly with the amount of sample analyzed on both low- and high-resolution instruments (over a 1000-fold dynamic range). Background noise added to a sample, either as a medium-complexity peptide mixture or as a high-complexity trypsinized proteome, exerts negligible effects on the abundance values reported by MapQuant and with coefficients of variance comparable to other methods. Finally, MapQuant's ability to define accurate mass and retention time features of isotopic clusters on a high-resolution mass spectrometer can increase protein sequence coverage by assigning sequence identities to observed isotopic clusters without corresponding MS/MS data. [source]

Regulation of membrane potential and fluid secretion by Ca2+ -activated K+ channels in mouse submandibular glands

Victor G. Romanenko
We have recently shown that the IK1 and maxi-K channels in parotid salivary gland acinar cells are encoded by the KCa3.1 and KCa1.1 genes, respectively, and in vivo stimulated parotid secretion is severely reduced in double-null mice. The current study tested whether submandibular acinar cell function also relies on these channels. We found that the K+ currents in submandibular acinar cells have the biophysical and pharmacological footprints of IK1 and maxi-K channels and their molecular identities were confirmed by the loss of these currents in KCa3.1- and KCa1.1 -null mice. Unexpectedly, the pilocarpine-stimulated in vivo fluid secretion from submandibular glands was essentially normal in double-null mice. This result and the possibility of side-effects of pilocarpine on the nervous system, led us to develop an ex vivo fluid secretion assay. Fluid secretion from the ex vivo assay was substantially (about 75%) reduced in animals with both K+ channel genes ablated , strongly suggesting systemic complications with the in vivo assay. Additional experiments focusing on the membrane potential in isolated submandibular acinar cells revealed mechanistic details underlying fluid secretion in K+ channel-deficient mice. The membrane potential of submandibular acinar cells from wild-type mice remained strongly hyperpolarized (,55 ± 2 mV) relative to the Cl, equilibrium potential (,24 mV) during muscarinic stimulation. Similar hyperpolarizations were observed in KCa3.1- and KCa1.1 -null mice (,51 ± 3 and ,48 ± 3 mV, respectively), consistent with the normal fluid secretion produced ex vivo. In contrast, acinar cells from double KCa3.1/KCa1.1 -null mice were only slightly hyperpolarized (,35 ± 2 mV) also consistent with the ex vivo (but not in vivo) results. Finally, we found that the modest hyperpolarization of cells from the double-null mice was maintained by the electrogenic Na+,K+ -ATPase. [source]

Small-conductance Cl, channels contribute to volume regulation and phagocytosis in microglia

Guillaume Ducharme
Abstract The shape and volume of microglia (brain immune cells) change when they activate during brain inflammation and become migratory and phagocytic. Swollen rat microglia express a large Cl, current (IClswell), whose biophysical properties and functional roles are poorly understood and whose molecular identity is unknown. We constructed a fingerprint of useful biophysical properties for comparison with IClswell in other cell types and with cloned Cl, channels. The microglial IClswell was rapidly activated by cell swelling but not by voltage, and showed no time-dependence during voltage-clamp steps. Like IClswell in many cell types, the halide selectivity sequence was I, > Br, > Cl, > F,. However, it differed in lacking inactivation, even at +100 mV with high extracellular Mg2+, and in having a much lower single-channel conductance: 1,3 pS. Based on these fundamental differences, the microglia channel is apparently a different gene product than the more common intermediate-conductance IClswell. Microglia express several candidate genes, with relative mRNA expression levels of: CLIC1 > ClC3 > ICln , ClC2 > Best2 > Best1 , Best3 > Best4. Using a pharmacological toolbox, we show that all drugs that reduced the microglia current (NPPB, IAA-94, flufenamic acid and DIOA) increased the resting cell volume in isotonic solution and inhibited the regulatory volume decrease that followed cell swelling in hypotonic solution. Both channel blockers tested (NPPB and flufenamic acid) dose-dependently inhibited microglia phagocytosis of E. coli bacteria. Because IClswell is involved in microglia functions that involve shape and volume changes, it is potentially important for controlling their ability to migrate to damage sites and phagocytose dead cells and debris. [source]

SK channels and the varieties of slow after-hyperpolarizations in neurons

Fivos Vogalis
Abstract Action potentials and associated Ca2+ influx can be followed by slow after-hyperpolarizations (sAHPs) caused by a voltage-insensitive, Ca2+ -dependent K+ current. Slow AHPs are a widespread phenomenon in mammalian (including human) neurons and are present in both peripheral and central nervous systems. Although, the molecular identity of ion channels responsible for common membrane potential mechanisms has been largely determined, the nature of the channels that underlie the sAHPs in neurons, both in the brain and in the periphery, remains unresolved. This short review discusses why there is no clear molecular candidate for sAHPs. [source]

Genetics of dermatofibrosarcoma protuberans family of tumors: From ring chromosomes to tyrosine kinase inhibitor treatment

Nicolas Sirvent
Dermatofibrosarcoma protuberans (DP) is a rare, slow-growing, infiltrating dermal neoplasm of intermediate malignancy, made up of spindle-shaped tumor cells often positive for CD34. The preferred treatment is wide surgical excision with pathologically negative margins. At the cytogenetic level, DP cells are characterized by either supernumerary ring chromosomes, which have been shown by using fluorescence in situ hybridization techniques to be derived from chromosome 22 and to contain low-level amplified sequences from 17q22-qter and 22q10,q13.1, or t(17;22), that are most often unbalanced. Both the rings and linear der(22) contain a specific fusion of COL1A1 with PDGFB. Similar to other tumors, the COL1A1-PDGFB fusion is occasionally cryptic, associated with complex chromosomal rearrangements. Although rings have been mainly observed in adults, translocations have been reported in all pediatric cases. DP is therefore a unique example of a tumor in which (i) the same molecular event occurs either on rings or linear translocation derivatives, (ii) the chromosomal abnormalities display an age-related pattern, and (iii) the presence of the specific fusion gene is associated with the gain of chromosomal segments, probably taking advantage of gene dosage effects. In all DP cases that underwent molecular investigations, the breakpoint localization in PDGFB was found to be remarkably constant, placing exon 2 under the control of the COL1A1 promoter. In contrast, the COL1A1 breakpoint was found to be variably located within the exons of the ,-helical coding region (exons 6,49). No preferential COL1A1 breakpoint and no correlation between the breakpoint location and the age of the patient or any clinical or histological particularity have been described. The COL1A1-PDGFB fusion is detectable by multiplex RT-PCR with a combination of forward primers designed from a variety of COL1A1 exons and one reverse primer from PDGFB exon 2. Recent studies have determined the molecular identity of "classical" DP, giant cell fibroblastoma, Bednar tumor, adult superficial fibrosarcoma, and the granular cell variant of DP. In approximately 8% of DP cases, the COL1A1-PDGFB fusion is not found, suggesting that genes other than COL1A1 or PDGFB might be involved in a subset of cases. It has been proposed that PDGFB acts as a mitogen in DP cells by autocrine stimulation of the PDGF receptor. It is encouraging that inhibitory effects of the PDGF receptor tyrosine kinase antagonist imatinib mesylate have been demonstrated in vivo; such targeted therapies might be warranted in the near future for treatment of the few DP cases not manageable by surgery. © 2003 Wiley-Liss, Inc. [source]

Grapevine yellows in Northern Italy: molecular identification of Flavescence dorée phytoplasma strains and of Bois Noir phytoplasmas

S. Botti
Abstract Aims:, Verify the presence and the molecular identity of phytoplasmas in Northern and Central Italy vineyards where yellows diseases are widespread. Methods and Results:, Phytoplasma presence and identity were determined by PCR/RFLP analyses on 16S ribosomal gene testing 1424 symptomatic samples. The 65% of samples resulted phytoplasma infected; in particular 256 samples were found positive to phytoplasmas belonging to group 16SrV (mainly Flavescence dorée associated), and the remaining 37% was infected by phytoplasmas belonging to ribosomal subgroup 16SrXII-A (Stolbur or Bois Noir associated). 16SrV ribosomal group representative strains were further typed for variability in SecY and rpS3 genes. The results showed the presence of phytoplasmas belonging to 16SrV-C, 16SrV-D and to a lesser extent, 16SrV-A subgroup. Conclusions:, Possible relationships between genetic polymorphisms of phytoplasma strains belonging to subgroup 16SrV-C and their geographic distribution and/or epidemic situations were detected. Significance and Impact of the Study:, Bois Noir and Flavescence dorée phytoplasmas are present in significant percentages in the areas under investigation. Molecular tools allowed to identify phytoplasma-infected plants and the genes employed as polymorphism markers resulted useful in distinguishing and monitoring the spreading of the diseases associated with diverse phytoplasmas belonging to 16SrV subgroup in vineyards. [source]

Tiling among stereotyped dendritic branches in an identified Drosophila motoneuron,,

F. Vonhoff
Abstract Different types of neurons can be distinguished by the specific targeting locations and branching patterns of their dendrites, which form the blueprint for wiring the brain. Unraveling which specific signals control different aspects of dendritic architecture, such as branching and elongation, pruning and cessation of growth, territory formation, tiling, and self-avoidance requires a quantitative comparison in control and genetically manipulated neurons. The highly conserved shapes of individually identified Drosophila neurons make them well suited for the analysis of dendritic architecture principles. However, to date it remains unclear how tightly dendritic architecture principles of identified central neurons are regulated. This study uses quantitative reconstructions of dendritic architecture of an identified Drosophila flight motoneuron (MN5) with a complex dendritic tree, comprising more than 4,000 dendritic branches and 6 mm total length. MN5 contains a fixed number of 23 dendritic subtrees, which tile into distinct, nonoverlapping volumes of the diffuse motor neuropil. Across-animal comparison and quantitative analysis suggest that tiling of the different dendritic subtrees of the same neuron is caused by competitive and repulsive interactions among subtrees, perhaps allowing different dendritic compartments to be connected to different circuit elements. We also show that dendritic architecture is similar among different wildtype and GAL4 driver fly lines. Metric and topological dendritic architecture features are sufficiently constant to allow for studies of the underlying control mechanisms by genetic manipulations. Dendritic territory and certain topological measures, such as tree compactness, are most constant, suggesting that these reflect the intrinsic molecular identity of the neuron. J. Comp. Neurol. 518:2169,2185, 2010. © 2010 Wiley-Liss, Inc. [source]

Synaptic specializations exist between enteric motor nerves and interstitial cells of Cajal in the murine stomach

Elizabeth A.H. Beckett
Abstract Autonomic neurotransmission is thought to occur via a loose association between nerve varicosities and smooth muscle cells. In the gastrointestinal tract ultrastructural studies have demonstrated close apposition between enteric nerves and intramuscular interstitial cells of Cajal (ICC-IM) in the stomach and colon and ICC in the deep muscular plexus (ICC-DMP) of the small intestine. In the absence of ICC-IM, postjunctional neural responses are compromised. Although membrane specializations between nerves and ICC-IM have been reported, the molecular identity of these specializations has not been studied. Here we have characterized the expression and distribution of synapse-associated proteins between nerve terminals and ICC-IM in the murine stomach. Transcripts for the presynaptic proteins synaptotagmin, syntaxin, and SNAP-25 were detected. Synaptotagmin and SNAP-25-immunopositive nerve varicosities were concentrated in varicose regions of motor nerves and were closely apposed to ICC-IM but not smooth muscle. W/WV mice were used to examine the expression and distribution of synaptic proteins in the absence of ICC-IM. Transcripts encoding synaptotagmin, syntaxin, and SNAP-25 were detected in W/WV tissues. In the absence of ICC-IM, synaptotagmin and SNAP-25 were localized to nerve varicosities. Reverse transcriptase polymer chain reaction (RT-PCR) and immunohistochemistry demonstrated the expression of postsynaptic density proteins PSD-93 and PSD-95 in the stomach and expression levels of PSD-93 and PSD-95 were reduced in W/WV mutants. These data support the existence of synaptic specializations between enteric nerves and ICC-IM in gastric tissues. In the absence of ICC-IM, components of the synaptic vesicle docking and fusion machinery is trafficked and concentrated in enteric nerve terminals. J. Comp. Neurol. 493:193,206, 2005. © 2005 Wiley-Liss, Inc. [source]

The ,1L -adrenoceptor is an alternative phenotype of the ,1A -adrenoceptor

C P Nelson
Despite over two decades of research, the molecular identity of the ,1L -adrenoceptor phenotype has remained elusive. In this issue of the BJP, Gray et al. (2008) provide persuasive evidence that the in vivo ,1L -adrenoceptor phenotype requires the expression of the ,1A -adrenoceptor gene. They have shown that in mice lacking the functional ,1A -adrenoceptor gene, ,1L -mediated responses to noradrenaline in prostate smooth muscle are substantially attenuated. These findings support earlier evidence that the ,1L -adrenoceptor profile represents a functional phenotype of the ,1A -adrenoceptor gene product, but additional cell background-dependent factors must act in concert with the ,1A -adrenoceptor protein to determine whether an ,1L - or a classical ,1A -adrenoceptor profile is expressed. The challenge remains to establish the nature of these cellular factors and the mechanism(s) by which they influence G-protein-coupled receptor pharmacology. British Journal of Pharmacology (2008) 155, 1,3; doi:fn1; published online 23 June 2008 [source]