SEARCH · PubMed Health

Results for “Transition Elements”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42Linked to original sources

PubMed2002

Cloning and polymorphism analysis of IL-4 proximal promoter in asthmatic children.

OBJECTIVE: To clone and study the polymorphism within interleukin-4 (IL-4) proximal promoter of asthmatic children. METHODS: The IL-4 proximal promoter segments were amplified and selected by polymerase chain reaction (PCR) and single strand conformation polymorphism (SSCP) with genomic DNA from ten healthy children and forty patients with dominantly allergic familial histories as templates. The selected PCR segments were cloned into recombinant plasmids pIL-4-Jx2. The PCR inserts were sequenced by dideoxy chain termination method. RESULTS: Seven aberrant bands were found in SSCP analysis from forty asthmatic patients. The sequencing results showed that four variant sites were found within or adjacent to the known IL-4 regulatory element. A C to A transversion located at -229 position was just within the positive regulatory element-I (PRE-I) in one patient. A C to T transition adjacent to the negative regulatory element-II (NRE-II) and an extra G adjacent to TATA box were found in two patients. A five base nucleotide deletion was found near signal transducers and activators of transcription-6 responsive element (STAT-6 RE) in one patient. CONCLUSION: There were polymorphisms within the IL-4 proximal promoter of allergic asthmatic patients and these polymorphisms might result in aberrant expression of IL-4 gene and asthma.

Asthma↗

PubMed1980

Analysis of courtship sequences of the hybrids between Drosophila melanogaster and Drosophila simulans.

Several transitions between sequential male courtship elements were analyzed for Drosophila melanogaster, its close relative D. simulans, and two types of hybrid males. Hybrid males from special reciprocal crosses did not differ. While D. melanogaster and D. simulans males differed markedly for the majority of transitions studied, hybrid males showed no consistent pattern with the parent species, being indistinguishable from D. simulans males, indistinguishable from D. melanogaster, or intermediate between them, depending on the trait observed. This suggests independent genetic control of these transitions during male courtship.

Animals↗

PubMed1993

MCB elements and the regulation of DNA replication genes in yeast.

In eukaryotic organisms, genes involved in DNA replication are often subject to some form of cell cycle control. In the yeast Saccharomyces cerevisiae, most of the DNA replication genes that have been characterized to date are regulated at the transcriptional level during G1 to S phase transition. A cis-acting element termed the MluI cell cycle box (or MCB) conveys this pattern of regulation and is common among more than 20 genes involved in DNA synthesis and repair. Recent findings indicate that the MCB element is well conserved among fungi and may play a role in controlling entry into the cell division cycle. It is evident from studies in higher systems, however, that transcriptional regulation is not the only form of control that governs the cell-cycle-dependent expression of DNA replication genes. Moreover, it is unclear why this general pattern of regulation exists for so many of these genes in various eukaryotic systems. This review summarizes recent studies of the MCB element in yeast and briefly discusses the purpose of regulating DNA replication genes in the eukaryotic cell cycle.

Bacterial Proteins↗

PubMed2005

Towards transition modelling for supersonic laminar flow control based on spanwise periodic roughness elements.

Laminar flow control (LFC) is one of the key enabling technologies for quiet and efficient supersonic aircraft. Recent work at Arizona State University (ASU) has led to a novel concept for passive LFC, which employs distributed leading edge roughness to limit the growth of naturally dominant crossflow instabilities in a swept-wing boundary layer. Predicated on nonlinear modification of the mean boundary-layer flow via controlled receptivity, the ASU concept requires a holistic prediction approach that accounts for all major stages within transition in an integrated manner. As a first step in developing an engineering methodology for the design and optimization of roughness-based supersonic LFC, this paper reports on canonical findings related to receptivity plus linear and nonlinear development of stationary crossflow instabilities on a Mach 2.4, 73 degrees swept airfoil with a chord Reynolds number of 16.3 million.

Journal Article↗

PubMed1987

X-ray microanalysis--a method for determination of elements in bladder biopsies.

Chemical elements in biopsies of normal human urothelium and transitional cell carcinoma (TCC) are determined by X-ray microanalysis in combination with scanning electron microscopy. The methodology presented is intended to be used in subsequent studies to compare data of normal urothelium and TCC of different stage and grade.

Calcinosis↗

PubMed2003

Recurrent exon shuffling between distant P-element families.

Two independent stationary P-related neogenes had been previously described in the Drosophila obscura species group and in the Drosophila montium species subgroup. In Drosophila melanogaster, P-transposable elements can encode an 87 kDa transposase and a 66 kDa repressor, but the P-neogenes have only conserved the capacity to encode a 66 kDa repressor-like protein specified by the first three exons. We have previously analyzed the genomic modifications associated with the transition of a P-element into the montium P-neogene, the coding capacity of which has been conserved for around 20 Myr ( Nouaud, D., and D. Anxolabéhère. 1997. Mol. Biol. Evol. 14:1132-1144). Here we show that the P-neogene of some species of the montium subgroup presents a new structure involving the capture of an additional exon from a very distant P-element subfamily. This additional exon is inserted either upstream or downstream of the first exon of the P-neogene. As a result of alternative splicing, these modified neogenes can produce, in addition to the repressor-like protein, a new protein which differs only by the NH2-terminal region. We hypothesize that this protein diversity within an organism results in a functional diversification due to the selective advantage associated with the domestication of the P-neogene in these species. Moreover, the autonomous P-element which provides the additional exons is still present in the genome. Its nucleotide sequence is more than 45% distant from the previously defined P-type element (M-type, O-type, T-type) and defines a new P-type element subfamily referred to as the K-type.

Amino Acid Sequence↗

PubMed2004

Spectroscopic, redox and biological activities of transition metal complexes with ons donor macrocyclic ligand derived from semicarbazide and thiodiglycolic acid.

A novel macrocyclic Schiff base ligand (2,5,9,12,14,18-hexaoxo-7,16-dithia-1,3,4,10,11,13-hexaazacycloocta-decane (H6L) with N4S2 coordinating sites was prepared by the reaction of the semicarbazide and thiodiglycolic acid. The transition metal complexes with macrocyclic ligand were synthesized and characterized by elemental analyses, magnetic susceptibility measurements, molar conductance, IR, electronic, and EPR spectral studies. Mass, 1H NMR and IR spectral techniques suggest the structural features of macrocyclic ligand. Magnetic and electronic spectral studies suggest an octahedral geometry of complexes. Electrochemical behaviour of cobalt, nickel and copper complexes were determined by cyclic voltammetry. The cyclic voltammogram of the copper complex at room temperature shows a quasi-reversible peaks for Cu(III)-->Cu(II) and Cu(II)-->Cu(I) couples. The macrocyclic ligand and its complexes show growth inhibitory activity against pathogenic bacteria and plant pathogenic fungi A. niger, A. alternata and P. variotii. Most of the complexes have higher activities than that of free ligand.

Anti-Bacterial Agents↗

PubMed2005

Electronic structure of orotic acid III geometric feature and thermal properties of some transition metal orotic acid complexes.

The complexes of orotic acid with Co(II), Ni(II), Fe(III), Cu(II), and Cd(II) were prepared and their stoichiometry were determined by elemental analysis. Co(II) and Ni(II) give complexes with orotic acid of 1:1 ratio whereas that of the remaining transition metals give complexes of 1:2 ratio. The stereochemistry of the studied metal complexes has been established by analyses of their electronic spectra and magnetic susceptibilities. The mode of bonding in the studied series of metal complexes was established via, analysis of their infrared spectra. The present analysis leads to the conclusion that all metal ions studied coordinate to orotic acid via N(1) and the adjacent carboxylate group. Thermal decomposition studies of orotic acid complexes have been carried out as to understand the status of water molecules present in these complexes as well as to know their general decomposition pattern. Theoretical investigation of the electronic structure of the studied metal complexes has been carried out. MO computations at the HF-level were performed. Charge density distribution, extent of distortion from regular geometry, dipole moment, and orientation were computed and discussed.

Cobalt↗

PubMed2006

Local versus global interactions in nonequilibrium transitions: A model of social dynamics.

A nonequilibrium system of locally interacting elements in a lattice with an absorbing order-disorder phase transition is studied under the effect of additional interacting fields. These fields are shown to produce interesting effects in the collective behavior of this system. Both for autonomous and external fields, disorder grows in the system when the probability of the elements to interact with the field is increased. There exists a threshold value of this probability beyond which the system is always disordered. The domain of parameters of the ordered regime is larger for nonuniform local fields than for spatially uniform fields. However, the zero field limit is discontinous. In the limit of vanishingly small probability of interaction with the field, autonomous or external fields are able to order a system that would fall in a disordered phase under local interactions of the elements alone. We consider different types of fields which are interpreted as forms of mass media acting on a social system in the context of Axelrod's model for cultural dissemination.

Journal Article↗

PubMed2006

Spectroscopic characterization and EPR spectral studies on transition metal complexes with a novel tetradentate, 12-membered macrocyclic ligand.

Complexes of Cr(III), Mn(II), Co(II), Ni(II) and Cu(II) containing a tetradentate macrocyclic N-donor ligand have been prepared via template reaction of 2,3-pentanedione, ethylene-di-ammine and transition metal ions. The complexes have been characterized on the basis of the elemental analysis, molar conductance, magnetic moment susceptibility, IR, electronic and EPR spectral studies. The complexes are of high spin type and possess four coordinate tetrahedral five coordinate square pyramidal and six coordinated octahedral/tetragonal geometry.

Electron Spin Resonance Spectroscopy↗

PubMedDate not supplied

[EEG correlates of the change in information processing strategy in visual imagery].

Cnanger of the spatial organization of biopotentials (spatial synchronization and disorder, spectral power and coherence) were analyzed during mental creating of visual images from two simple elements: the angle the oblique line. With the transition from the first to the fourth task, the total number of used elements increased from the number suitable for simultaneous presentation and conscious processing (less than 7 +/- 2) to a much higher number. Changes in the characteristics of the spatial organization of biopotentials associated with the increase in the number of the elements can be explained by a change in the information processing strategy, transformation of information processing strategy, i.e. the transition from the left-hemispheric successive (conscious) analyses to the right-hemispheric simultaneous (unconscious) processing. It was shown that this change in the information processing strategy was accompanied by an increase in the index of spatial disorder sensitive to complicated nonlinear processes. Subjects were divided in two groups with different forms of the reorganization of interhemispheric and fronto-occipital relationships of biopotentials. These data are interpreted in terms of different involvement of the unconscious intellectual processes of different layers (subconsciousness and superconsciousness) in the change in information processing strategy.

Adult↗

PubMed1999

The phase transitions and crystal structures of Ba3RM2O7.5 complex oxides (R = rare-earth elements, M = Al, Ga).

The structures of alpha-Ba(3)RAl(2)O(7.5) and beta-Ba(3)RM(2)O(7.5) complex oxides (R = rare-earth elements, M = Al, Ga) have been studied by a combination of X-ray diffraction, electron diffraction (ED) and high-resolution electron microscopy (HREM). The alpha and beta forms have cell parameters related to the perovskite subcell: a = 2a(per), b = a(per)(2)(1/2), c = 3a(per)(2)(1/2), however, the alpha form has an ortho-rhombic unit cell whereas the beta form adopts monoclinic symmetry. The crystal structure of monoclinic Ba(3)ErGa(2)O(7.5) was refined from X-ray powder data (space group P2/c, a = 7.93617(9), b = 5.96390(7), c = 18.4416(2) Å, beta = 91.325(1) degrees, R(I) = 0.023, R(P) = 0.053), the structure of the alpha form (space group Cmc2(1)) was deduced from ED and HREM data. The important feature of the alpha and beta structures is the presence of slabs containing strings of vertex-sharing tetrahedral Al(2)O(7) pairs. Two almost equivalent oxygen positions within the strings can be occupied either in an ordered manner leading to the low-temperature beta phase or randomly resulting in the high-temperature alpha structure. The critical temperature of this order-disorder phase transition was determined by high-temperature X-ray diffraction and by differential thermal analysis (DTA). In situ ED and HREM observations of the second-order phase transition confirmed the symmetry changes and revealed numerous defects (twins and antiphase boundaries) formed during the phase transformation.

Journal Article↗

PubMed1984

The role of astrocytes in the formation of cartilage in gliomas. An immunohistochemical study of four cases.

The occasional presence of focal cartilage in gliomas is generally attributed to metaplasia of the mesenchymal supportive elements. While this mechanism undoubtedly exists, the present report describes a different mode of development of cartilage in four gliomas occurring in young individuals. Two of the tumors were pontine astrocytomas, one was a mixed ependymoma and astrocytoma involving the fourth ventricle and the brainstem, and one was an extraspinal malignant astrocytoma in the lumbar region of a young boy who earlier had been diagnosed as having a pontine glioma for which he received radiation treatment. In all four tumors, transitions from astrocytic to cartilaginous elements were seen, characterized by an increasing deposition of chondroid ground substance between the astrocytes and a gradual morphologic changes of the glial cells to more rounded forms with a vacuolated cytoplasm, indistinguishable from chondrocytes of mesenchymal origin. Many of these cells retained positive staining for glial fibrillary acidic protein by the immunoperoxidase method, attesting to their astrocytic nature. The production of cartilage by neoplastic astrocytes may be related to their ability to secrete, in certain circumstances and occasionally in large amounts, basement membrane material and other forms of mucopolysaccharides, which may become condensed to form a chondroid ground substance. The process appears analogous to that of cartilage formation by epithelial cells in pleomorphic adenomas of the salivary glands.

Adolescent↗

PubMed2003

Who owns Australia's water--elements of an effective regulatory model.

This paper identifies and describes a number of global trends in regulatory theory and legal scholarship. It points out the huge level of complexity demanded by globalisation and the unfortunate complication of this is that there is legal indeterminacy. The legal indeterminacy springs from the desire to amend and alter existing models. That has been the thrust of the Council of Australian Governments changes to adapt and add huge amounts of complexity to a flawed system. This paper argues that an effective water regulatory model requires a fundamental re-examination of the concept of water ownership and a capturing by the State of the right to allocate rainfall. This foundation is effective and the way forward to deal with the key issues in this transition phase. The second key element to an effective regulatory model is the concept of performance-based assessment. This requires information and schemes to be set up to work out ways to monitor and evaluate the performance of the utility on selected criteria. For Australia at present there is a dire lack of agreed criteria on these key issues and these have the potential to pull apart the whole process. The key issues are indigenous rights, governance issues, public participation, alteration of pre-existing rights and incorporation of environmental requirements.

Australia↗

PubMed1972

A condensation type porometer for field use.

A double cup transpiration porometer is described which simultaneously measures the resistance to water vapor diffusion from the upper and lower epidermises of a leaf. In use the cups are dried, the porometer is clamped on the leaf, and the transit time required for water vapor to condense on a cold (0 C) reflective surface in each cup is recorded. Since the sensing element remains at constant temperature, only transit time and leaf temperature are required to calculate leaf resistance.

Journal Article↗

PubMed2006

Managing Sure Start in partnership.

In March 2006, Sure Start programmes were mainstreamed, becoming 'Children's Centres' for which local authorities have assumed strategic responsibility. This paper describes an evaluation of a Sure Start local programme Management Board which was conducted in preparation for this transition. Focusing on practices relating to partnership working and community involvement, a distinctive trident evaluation model was used to explore outcomes, processes and multiple stakeholder perspectives through a multi-method approach (incorporating interviews, questionnaires and documentary analysis). This revealed that an effective, collaborative style of working had been fostered between board members, resulting in synergy. Furthermore, a number of governance arrangements were identified that specifically supported partnership developments, including quorum regulations and adherence to decision-making by consensus. A series of recommendations are presented that were made with the aim of strengthening the community voice on the board and preserving the most effective and empowering elements of practice following the transition.

Attitude of Health Personnel↗

PubMed2004

Supported transition-metal oxide catalysts for reduction of sulfur dioxide with hydrogen to elemental sulfur.

This work is for the purpose to find a high performance catalyst for the catalytic reduction of SO2 with H2 as a reducing agent. NiO/gamma-Al2O3 catalyst was found to be the most active catalyst among the seven gamma-Al2O3-supported metal-oxide catalysts tested. With NiO as the active species, of the supports tested, gamma-Al2O3 was the most suitable one and the optimal Ni content was 16 wt%. Using this NiO/gamma-Al2O3 catalyst, we found that the optimal feed ratio of H2/SO2 is 2:1 and the catalyst presulfided with H2 + H2S exhibits a higher performance than that pretreated with H2 or He. XRD patterns reveal that the nickel oxide experienced a transformation to Ni3S2 and NiS, and then to NiS2, the most active nickel sulfide, during the reaction process. The reason for the highest catalyst activity of 16 wt% Ni was attributed to the largest amount of NiS2. Water vapor in the feed gas reactant caused inhibition of catalyst activity, whereas H2S promoted the reduction of SO2. These phenomena were rationalized with the aid of Claus reaction.

Air Pollutants↗

PubMed1995

Transition metal ion activation of DNA binding by the diphtheria tox repressor requires the formation of stable homodimers.

The diphtheria tox repressor (DtxR) is a transition metal ion-dependent regulatory element that controls the expression of diphtheria toxin and several genes involved in the synthesis of siderophores in Corynebacterium diphtheriae. In the presence of transition metal ions apo-DtxR becomes activated and specifically binds to its target DNA sequences. We demonstrate by glutaraldehyde cross-linking that monomeric apo-DtxR is in weak equilibrium with a dimeric form and that upon addition of activating metal ions to the reaction mixture a dimeric complex is stabilized. Addition of the DNA-binding-defective mutant apo-DtxR(delta 1-47) to apo-DtxR in the absence of transition metal ions inhibits conversion of the apo-repressor to its activated DNA-binding form. We also show that the binding of Ni2+ to both apo-DtxR and apo-DtxR(delta 1-47) is cooperative and that upon ion binding there is a conformational change in the environment of the indole ring moiety of Trp-104. For the wild-type repressor the consequences of this conformational change include a shift in equilibrium toward dimer formation and activation of target DNA binding by the repressor. We conclude that the formation of DtxR homodimers is mediated through a protein-protein interaction domain that is also activated on metal ion binding.

Apoproteins↗