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At least 109 records · Page 6Linked to original sources
PubMed2002

The zebrafish T-box genes no tail and spadetail are required for development of trunk and tail mesoderm and medial floor plate.

T-box genes encode transcriptional regulators that control many aspects of embryonic development. Here, we demonstrate that the mesodermally expressed zebrafish spadetail (spt)/VegT and no tail (ntl)/Brachyury T-box genes are semi-redundantly and cell-autonomously required for formation of all trunk and tail mesoderm. Despite the lack of posterior mesoderm in spt(-);ntl(-) embryos, dorsal-ventral neural tube patterning is relatively normal, with the notable exception that posterior medial floor plate is completely absent. This contrasts sharply with observations in single mutants, as mutations singly in ntl or spt enhance posterior medial floor plate development. We find that ntl function is required to repress medial floor plate and promote notochord fate in cells of the wild-type notochord domain and that spt and ntl together are required non cell-autonomously for medial floor plate formation, suggesting that an inducing signal present in wild-type mesoderm is lacking in spt(-);ntl(-) embryos.

Alleles↗
PubMed1993

Circulatory pattern and structure in the tail and tail fins of Xenopus laevis tadpoles.

This investigation was initiated with the intent of study capillary sprouting in the tadpole tail fin microcirculation of the African clawed frog, Xenopus laevis, using a combination of intravital video recordings and electron microscopy. The tadpoles were observed daily for periods up to one hour during one to two weeks. The capillary sprouts originated mostly from postcapillary venules, and within 24-48 h merged with other capillary sprouts, subsequently establishing a capillary loop with blood flow. As the circulatory patterns developed further, capillary regressions also occurred. As the electron microscope analyses of the capillary sprouts progressed, it became obvious that a thorough electron microscope study of the blood vessels of the tadpoles was required in order to explore structural characteristics of arterial and venous blood vessels. Thus, this article deals primarily with the general organization of the tadpole tail circulation, and the ultrastructural characteristics of the vascular walls. A subsequent article will deal with the role of endothelial cells, fibroblasts and pericytes in the process of capillary sprouting and regression, based on intravital recordings and electron microscope analyses.

Animals↗
PubMed1992

Molecular architecture of acetylcholinesterase collagen-tailed forms; construction of a glycolipid-tailed tetramer.

Asymmetric forms of Torpedo acetylcholinesterase (AChE) are produced in COS cells by the simultaneous expression of collagenic subunits (Q) and catalytic T subunits (AChET). Truncated AChET delta subunits, from which most of the C-terminal peptide (TC) had been deleted by mutagenesis, did not associate with Q subunits. The TC peptide is therefore necessary for the association of the AChET and Q subunits. In order to determine the orientation of the Q subunit in the collagen-tailed forms, we have developed an antiserum against its non-collagenic C-terminal domain, expressed as a fusion protein in Escherichia coli. This antiserum, which recognized the Q subunit in Western blots, was found to react with intact asymmetric forms, but not with collagenase-treated forms, from which the distal part of the tail had been cleaved, suggesting that the N-terminal non-collogenic domain (QN) is responsible for the interaction with the AChET subunits. This was confirmed by creating a chimeric subunit (QN/HC), in which QN was linked to the C-terminal peptide of the H subunit of Torpedo AChE, which contains the glycophosphatidylinositol (GPI) cleavage/attachment signal: co-expression of AChET and QN/NC produced GPI-anchored tetramers, which were sensitive to PI-PLC and largely exposed to the external surface of the cells. We thus demonstrate that: (i) the HC peptide is sufficient to determine the addition of a glycolipid anchor and (ii) the QN domain is sufficient to bind a catalytic AChET tetramer by interacting with the TC peptide.

Acetylcholinesterase↗
PubMed2001

Preliminary risk assessment of the wet landscape option for reclamation of oil sands mine tailings: bioassays with mature fine tailings pore water.

Chemical and biological assays have been carried out on the "pore water" that results from the settling of the tailings that accompany bitumen recovery from the Athabasca oil sands. Examination of the nonacidic extracts of pore water by gas chromatography-mass spectroscopy allowed the identification of numerous two- to three-ring polycyclic aromatic compounds (PACs), to a total concentration of 2.6 micrograms/L of pore water. The PACs were biodegraded by microflora naturally present in the pore water. Acute toxicity was associated principally with the acidic fraction (naphthenic acids) of pore water extracts according to the Microtox assay; other work has shown that acute toxicity dissipates fairly rapidly. Both individual PACs and concentrated pore water extracts showed minimal levels of binding to the rat Ah receptor and induced minimal ethoxyresorufin-O-deethylase activity in primary rat hepatocytes, showing an insignificant risk of inducing monooxygenase activity. Taken together with previous work showing negligible mutagenic activity of these extracts, we conclude that it should be possible to develop tailing slurries into biologically productive artificial lakes.

Animals↗
PubMed1997

The human GCAP1 and GCAP2 genes are arranged in a tail-to-tail array on the short arm of chromosome 6 (p21.1).

GCAP1 and GCAP2 are related Ca(2+)-binding proteins that activate photoreceptor guanylate cyclase(s). We showed previously that the human GCAP1 gene, consisting of four exons, is located at 6p21.1 (locus designation GUCA). To identify the chromosomal location of the GCAP2 gene, we first cloned its cDNA and determined its intron-exon distribution by PCR analysis. The results show that the introns of the GCAP2 gene are positioned exactly as in the GCAP1 gene and are nearly double in size. Sequence similarity between the two genes, however, is limited to portions of exons 1 and 2. The GCAP1 and GCAP2 genes are transcribed into single mRNA species (1.7 and 2.2 kb, respectively) and are detectable only in the retina by Northern blotting. The GCAP2 gene was found by somatic human-hamster hybrid panel analysis and FISH to reside at GUCA in a region indistinguishable from that of GCAP1. PCR analysis with exon 4-specific primers showed that the genes are in a tail-to-tail array less than 5 kb apart and altogether span less than 20 kb of genomic DNA. The identical gene structures and loci of GCAP1 and GCAP2, and the identical function of the gene products, are consistent with gene duplication event.

Amino Acid Sequence↗
PubMed1996

Co-amplification to tail-to-tail copies of MuRVY and IAPE retroviral genomes on the Mus musculus Y chromosome.

We have isolated a clone from a C57BL/6 genomic library that contains both part of the Y Chromosome-specific 8.7 kbp MuRVY genome (Hutchinson and Eicher, J. Virol. 63, 4043, 1989) and a full-length 8.3 kbp Intracisternal A Particle genome (IAPE-Y), in a tail-to-tail organization. Although IAPs are encoded by a disperse multigene family (approximately 1000 copies per haploid genome), we present evidence that a significant proportion of the IAP-related sequences are present on the Y Chromosome (Chr) and that a >25 kbp genomic sequence, which contains the two proviral genomes, has been amplified on the Y Chr. Two discrete amplified families of MuRVY retroviral genomes distinguishable by a polymorphic restriction site were detected, suggestive that amplification occurred in incremental stages. The presence of MuRVY-related DNA sequences, but absence of IAPE-Y-related DNA sequences in Mus spretus suggests that the IAPE-Y retrotransposition event occurred after the evolutionary divergence of the lineages leading to Mus musculus and Mus spretus, and that the amplification of MuRVY occurred independently in the two lineages.

Animals↗
PubMed1989

Stable binding of Drosophila heat shock factor to head-to-head and tail-to-tail repeats of a conserved 5 bp recognition unit.

The minimal DNA sequence required for the formation of a stable complex with Drosophila heat shock factor (HSF) in vitro is an inverted repeat of a 5 bp recognition unit, -GAA-. Surprisingly, both permutations of this 5 bp unit, head-to-head and tail-to-tail, bind to HSF with similar affinity and with striking 2-fold symmetry. HSF also binds to longer arrays of inverted 5 bp units, and the size of the HSF footprint increases with the addition of each 5 bp unit to these arrays. However, the electrophoretic mobility of the HSF-DNA complexes decreases most distinctly with the addition of every three 5 bp units. Cross-linking of purified HSF in the absence of DNA generates complexes with the sizes expected of HSF trimers. We propose that trimers of HSF bind to DNA and that the number of HSF subunits in direct contact with DNA is determined by the number of correctly positioned 5 bp recognition units.

Animals↗
PubMed1986

A remarkable amino acid sequence homology between a phage T4 tail fibre protein and ORF314 of phage lambda located in the tail operon.

We have found that the amino acid (aa) sequence of the tip of phage T4 tail fibre (gene 37) shows more than 50% homology with the aa sequence predicted from an open reading frame (ORF314) in the phage lambda genome. ORF314 is near the 3' end of the late morphogenetic operon, beyond gene J coding for the lambda tail fibre. The homologous sequences are for the most part composed of repeated aa, the most remarkable of which is a Gly-X-His-Y-His motif where X and Y are small, uncharged aa, found six times in the T4 protein and seven times in the lambda ORF314 sequence.

Amino Acid Sequence↗
PubMed2004

Early growth response of container-grown selected woody boreal seedlings in amended composite tailings and tailings sand.

Successful reclamation of saline-alkaline sites may be enhanced by revegetating with species that are tolerant to factors that limit normal plant growth. Boreal woody plants tested in this study have shown promise for use in saline habitats. This study was conducted to assess the effects of amendment treatments (peat, pulp waste, agriboost, a combination of pulp waste and fly ash, and mineral fertilizer) on the early growth of three hybrid poplar clones and three coniferous species. Twelve-week and 18-week container-grown hybrid poplar clones and coniferous species, respectively, were monitored for 12 weeks in pot culture in both composite tailings (CTs) and tailings sand (TS) materials obtained from the oil sands plant, Syncrude Canada Ltd., Ft. McMurray, Alberta. These substrates with low nutrients, organic matter, and water-holding capacities, were amended with different organic materials at different rates. Growth, as assessed by the volume increment in both substrates, was generally better for the first 6 weeks than for the last 6 weeks. Growth was reduced during the last 6 weeks due to nutrient depletion over time in these impoverished substrates. Overall, for both substrates, the mineral fertilizer, 20%, 40% and 60% peat were the best amendments treatments for poplar clones with NM-6 being the most productive clone. For coniferous species, 20% and 40% pulp or peat appear to be the best amendment treatments, with lodgepole pine being the most productive species. The inflexion point of the regression functions were found around 30% rate of the amendment materials. The results also indicated that peat and pulp waste were the best amendment treatments for both hybrid poplars and coniferous species whereas the agriboost and mix (combination of pulp waste and fly ash) were the worst.

Canada↗
PubMed2003

The rod opsin pigments from two marsupial species, the South American bare-tailed woolly opossum and the Australian fat-tailed dunnart.

Rod visual pigment genes have been studied in a wide range of vertebrates including a number of mammalian species. However, no marsupials have yet been examined. To correct this omission, we have studied the rod pigments in two marsupial species, the nocturnal and frugivorous bare-tailed woolly opossum, Caluromys philander, from Central and South America, and the arhythmic and insectivorous fat-tailed dunnart, Sminthopsis crassicaudata, from Australia. Phylogenetic analysis establishes that the cloned opsin sequences are orthologues of rod opsin genes from other vertebrate species. The deduced amino acid sequences show that both possess glutamate at residue 122, a feature of rod opsins, and the corresponding gene follows the typical vertebrate rod opsin pattern of five exons separated by four introns. Compared to other vertebrates, a stretch of five residues near the C-terminus is deleted in the rod opsin of both marsupials and all eutherian mammals. From microspectrophotometric measurements, the pigments in the two species show an 8 nm difference in peak absorbance; the molecular basis for this spectral shift is discussed and two candidate substitutions are identified.

Amino Acid Sequence↗
PubMed2005

Evidence for an evolutionary force that prevents epigenetic silencing between tail-to-tail rice genes with a short spacer.

During the course of evolution, the genome should have toned down various types of genomic noise, such as those that cause the unstable expression or gene silencing observed in transgenic organisms. We found a rice genomic segment where two genes, encoding 5-enolpyruvylshikimate-3-phosphate synthase (EPSPs) and ribosomal protein small subunit 20 (rps20), are located in a tail-to-tail orientation and separated by only 300 bp of spacer. It is possible that this kind of structure would give rise to unstable expression due to antisense RNA derived from the neighboring gene. We examined this possibility using Northern blot, reverse transcription-polymerase chain reaction (RT-PCR), and 3' RACE analyses, but obtained no evidence for instability or antisense RNAs of these housekeeping genes. Comparison of the sequences in the corresponding regions among related rice species revealed a lower level of genetic divergence of both the 3'-untranslated region (3'-UTRs) than of the other noncoding regions; in particular both of the boundaries between the 3'-UTRs and the spacer were markedly conserved. The conservation of both the terminal regions is most likely the result of purifying selection, implying a functional role for the strict termination of the transcription of these genes to prevent gene-silencing-related events.

Amino Acid Sequence↗
PubMed1998

Linker histone tails and N-tails of histone H3 are redundant: scanning force microscopy studies of reconstituted fibers.

The mechanisms responsible for organizing linear arrays of nucleosomes into the three-dimensional structure of chromatin are still largely unknown. In a companion paper (Leuba, S. H., et al. 1998. Biophys. J. 74:2823-2829), we study the contributions of linker histone domains and the N-terminal tail of core histone H3 to extended chromatin fiber structure by scanning force microscopy imaging of mildly trypsinized fibers. Here we complement and extend these studies by scanning force microscopy imaging of selectively reconstituted chromatin fibers, which differ in subtle but distinctive ways in their histone composition. We demonstrate an absolute requirement for the globular domain of the linker histones and a structural redundancy of the tails of linker histones and of histone H3 in determining conformational stability.

Animals↗
PubMed2002

Fluorescence studies of pyrene maleimide-labeled translin: excimer fluorescence indicates subunits associate in a tail-to-tail configuration to form octamer.

Translin is an octameric single-stranded DNA binding protein consisting of 228 amino acid residues per monomer. This protein contains two cysteine residues per monomer. Studies of reactions with DTNB show that both cysteines are reactive and exhibit biphasic reaction kinetics. Further studies with two site-directed mutants, C58S and C225S, confirm that Cys-58 reacts slowly while Cys-225 reacts quickly. Pyrene excimer emission was observed for pyrene maleimide-labeled C58S mutant. This was not observed, however, with the pyrene maleimide-labeled C225S mutant. DAS (decay associated spectra) revealed that all excited pyrene labels on C225 residues can form excimers with pyrenes of adjacent subunits within a few nanoseconds. Time-resolved emission anisotropy detects a rotational correlation time appropriate for octameric but not dimeric species. These results indicate proximity for the Cys-225 residues on adjacent monomers and that the subunits must interact in a tail-to-tail orientation. Moreover, disulfide bonds are not required for the formation of an octamer.

Base Sequence↗
PubMed2001

Bimetallic-induced tail-to-tail dimerization and C-H activation of methyl acrylate.

An organometallic complex resulting from tail-to-tail dimerization and C-H activation of methyl acrylate (MA), [Mo(CO2Cp(eta 3-(MeO2C)CH[symbol: see text]CH[symbol: see text]CHCH2(CO2Me)] 2, has been fully characterized from the reaction of the heterobimetallic complex [Cp*Ni=Mo(mu-CO)(CO)2Cp] with MA and an exclusively eta 3-allyl bonding mode of the coupled ligand was established for the first time by X-ray diffraction; formation of 2 is accompanied by that of the mu 3-alkylidyne-capped cluster [NiMo2(mu 3-CCH2CO2Me)(CO)4Cp*Cp2] 3 which results from a double C-H activation of the CH2 group of MA; none of these reactions occur with the corresponding homodinuclear complexes.

Journal Article↗
PubMed1998

Medulloblastoma presenting with tentorial "dural-tail" sign: is the "dural-tail" sign specific for meningioma?

To the best of our knowledge, the association of a medulloblastoma with a "dural-tail" sign has not been previously reported. A 24-year-old male developed severe headaches and right-sided dysmetria that worsened over 1 month. Magnetic resonance (MR) imaging of the brain demonstrated a heterogeneously enhancing lesion in the posterior fossa. The lesion appeared to be tentortally-based and exhibited a characteristic "dural-tail" sign, which is considered pathognothonic for meningioma. Cerebellar tonsil ectopia and hydrocephalus were also present. The presumptive diagnosis of tentorial meningioma was made. The lesion was resected by a posterior fossa approach. At surgery, the appearance of the tumor was inconsistent with the diagnosis of meningioma, and histopathologic evaluation yielded the diagnosis of medulloblastonia. This case and the literature demonstrate that malignant tumors can present with the characteristic MR imaging appearance of a meningioma. This possibility must be considered when treatment is planned, especially if a nonoperative course is favored.

Case Reports↗
PubMed2002

Elovl1 and p55Cdc genes are localized in a tail-to-tail array and are co-expressed in proliferating cells.

Elovl1 is a ubiquitously expressed gene, the product of which belongs to a highly conserved family of microsomal enzymes, which are involved in the formation of very long chain fatty acids and sphingolipids in yeast to man. To elucidate the structure and regulation of the Elovl gene we have isolated a lambda phage genomic DNA clone containing the entire mouse gene and found that Elovl1 consists of eight exons that are dispersed over 5.4 kb of genomic sequence. Interestingly, sequencing of the lambda clone to completion revealed that the insert contained a segment of the cell cycle gene p55Cdc directed in the opposite orientation. The genes are very tightly linked so that the 3'-end of the long mRNA species are complementary over a short stretch of nucleotides. Although both Elovl1 and p55Cdc are highly conserved genes, a BLAST search implies that the tail-to-tail arrangement has evolved in vertebrates. Despite the non-similar expression pattern in different tissues, mRNA analysis of the two genes disclosed simultaneous transcription during a proliferation-differentiation transition state, which suggests that the two genes may be regulated through a common bi-directional transcription mechanism under specific conditions.

Acetyltransferases↗
PubMed1998

Round-spotted pufferfish (Tetraodon fluviatilis) snf5 gene is oriented in a tail-to-tail manner with the set gene which encodes an inhibitor of protein phosphatase 2A.

The round-spotted pufferfish Tetraodon fluviatilis has a genome size of 380 Mb which is slightly smaller than that of another pufferfish Fugu rubripes rubripes (Fugu). Due to its compact genome and small introns, Fugu has been introduced as a model for genome studies. Recently, the round-spotted pufferfish has also been proposed as a new model for genome studies because of the ease in obtaining material and high-sequence homology to that of Fugu. In this study, we have cloned and characterized the snf5 and set genes from the round-spotted pufferfish. The snf5 gene is composed of 9 exons spanning about 2.9 kb whereas the set gene consists of 8 exons spanning about 2.7 kb. They are linked in a tail-to-tail manner with an intergenic region of about 6.5 kb. So far, the genomic structures of human snf5 and set genes are unknown. Based on our data, the pufferfish SNF5 and SET display high amino acid sequence identity (>90%) with the respective human genes. By primer extension and sequence analysis, we found that putative promoter region of the snf5 gene contains a typical TATA box and numerous potential binding sites for transcription factors including AP1, AP2, AP3, c-Myb, HNF-5, and NF-IL6. As for the set gene, its promoter region does not have any TATA or CCAAT motif and contains a few potential binding sites for transcriptional factors such as c-Myb and gamma-IRE. When these promoter regions were placed upstream of the CAT reporter gene and transfected into a carp CF cell line, the 5'-upstream 1.6-kb DNA fragment of the snf5 gene displayed stronger promoter activity, approximately three-fold higher than that of the 5'-upstream 1.3 kb DNA fragment of the set gene. By transient expression and immunofluorescent staining, we also showed that the pufferfish SNF5 and SET are nuclear proteins, consistent with their postulated roles as transcriptional factors.

Amino Acid Sequence↗