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PubMedDate not supplied

Ultrastructure of electrophysiologically identified human sinoatrial nodes.

The ultrastructure of freshly excised human sinus node tissue was studied. In three female patients (ages 20, 30, and 36 years) medically refractory disabling episodes of inappropriate sinus tachycardia were surgically treated by extirpation of the sinus node. Each patient underwent intraoperative electrophysiological mapping to determine the area of earliest atrial activation. This area corresponded anatomically to the region of the sinoatrial node and was excised in each patient, the defect repaired using a pericardial patch. The freshly excised SA nodes underwent ultrastructural study. Three types of myocardial cells were identified: pacemaker or polygonal cells with clear cytoplasm, few mitochondria and sparse numbers of contractile elements (P cells); a transitional cell with slightly increased numbers of myofibrils (T cells); and typical atrial myocardial cells with normal numbers of contractile elements. These cell types have previously been identified in post-mortem studies of presumed SA node. The current study confirms the cell types in electrophysiologically documented SA nodes. The one abnormal finding observed in transitional cells in all patients was an increased number of lipofuscin-laden vacuoles. These vacuoles are considered a sign of cell degeneration and their occurrence was totally unexpected in these young adults. In summary, ultrastructural study of electrophysiologically documented human SA nodes confirmed the cell types identified in post-mortem studies. Furthermore, lipofuscin-laden vacuoles were increased in these three patients and this finding may serve as an ultrastructural marker associated with the syndrome of inappropriate sinus tachycardia.

Adult↗

PubMed1988

[Proliferation and differentiation of isolated cells and symplasts of the skeletal muscle tissue of chick embryos].

By means of the radioautography, morphometry and alkaline dissociation methods musculus tibialis anterior has been studied in 30 chick embryos and chickens. The muscle fibers are variable in their diameter and length, number of nuclei 3H-thymidine-labelled including. The greatest variability of the structures is noted in 11-14-day-old embryos. Three classes of myotubes (MT) and symplasts are described. The primary MT are evidently the source of cellular elements, that form new cellular-symplastic structures (muscular-proliferative units) that develop, for some time, in a close connection with the primary MT. Between the extreme morphological variants of structure of the muscular elements, there is a transitional form. All the forms of the myosymplasts and MT reflect various stages of differentiation of the myogenic elements; this results in formation of the cellular-symplastic system--muscle fiber.

Animals↗

PubMed2004

MATE transposable elements in Aspergillus nidulans: evidence of repeat-induced point mutation.

The sequences of five MATE transposable elements were retrieved from the Aspergillus nidulans genome sequence. These elements are 6.1 kb in length and are characterized by 9-10 bp target site duplications, paired approximately 40 bp palindromes close to each end, and in the unmutated elements, 57 clustered Spe-motifs (RWCTAGWY) scattered through their length. Short open reading frames have no known homology. Two of the MATE elements have numerous C --> T transitions on both DNA strands relative to the remaining three elements. These mutations have all the characteristics of repeat-induced point mutation (RIP) previously described in Neurospora crassa, but not experimentally demonstrated in A. nidulans. Ninety-eight percent of mutated cytosines are in CpG and CpA doublets, the former mutating at higher frequency.

Aspergillus nidulans↗

PubMed2006

Element partitioning: the role of melt structure and composition.

We segregated coexisting gabbroic and granitic melts by centrifuging them at high pressures and temperatures and measured the trace element compositions of the melts by laser ablation inductively coupled plasma mass spectrometry. Our results demonstrate that the effect of melt structure contributes about one order of magnitude to crystal/melt partition coefficients. Partitioning of alkali and alkaline earth elements strongly depends on field strength: Amphoteric and lone pair electron elements partition into the polymerized granitic melt; and rare earth, transition, and high field strength elements coordinated by nonbridging oxygens partition remarkably similar into the gabbroic melt. A regular solution model predicts these effects.

Journal Article↗

PubMed2005

Synthesis and structure investigation of the antibiotic amoxicillin complexes of d-block elements.

The study of some transition metals (M) and amoxicillin trihydrate (ACT) ligand complexes (M-ACT) that formed in solution involved the spectrophotometric determination of stoichiometric ratios and their stability constants and these ratios were found to be M:ACT = 1:1, 1:2 and 2:1 in some instances. The calculated stability constants of these chelates, under selected optimum conditions, using molar ratio method have values ranging from K(f) = 10(7) to 10(14). These data were confirmed by calculations of their free energy of formation deltaG, which corresponded to their high stabilities. The separated solid complexes were studied using elemental analyses, IR, reflectance spectra, magnetic measurements, mass spectra and thermal analyses (TGA and DTA). The proposed general formulae of these complexes were found to be ML(H2O)w(H2O)x(OH)y(Cl)2, where M = Fe(II), Co(III), w = 0, x = 2, y = 1, z = 0; M = Co(II), w = 0, x = 1, y = 0, z = 1; M = Fe(III), w = 0, x = 1, y = 2, z = 0; M = Ni(II), Cu(II) and Zn(II), w = 2, x = 0, y = 1, z = 0, where w = water of crystallization, x = coordinated water, y = coordinated OH(-) and z = Cl- in the outer sphere of the complex. The IR spectra show a shift of nu(NH) (2968 cm(-1)) to 2984-2999 cm(-1) of imino group of the ligand ACT and the absence of nu(CO) (beta-lactame) band at 1774 cm(-1) and the appearance of the band at 1605-1523 cm(-1) in all complexes suggest that 6,7-enolization takes place before coordination of the ligand to the metal ions. The bands of M-N (at 625-520 cm(-1)) and of M-O (at 889-7550 cm(-1)) proved the bond of N (of amino and imino groups) and O of C-O group of the ligand to the metal ions. The reflectance spectra and room temperature magnetic measurements refer to octahedral complexes of Fe(II) and Fe(III); square planner form of Co(II), reduced Co(III), Ni(II) and Cu(II)-ACT complexes but tetrahedral form of Zn-ACT complex. The thermal degradation of these complexes is confirmed by their mass spectral fragmentation. These data confirmed the proposed structural and general formulae of these complexes.

Amoxicillin↗

PubMed1999

Gonadoblastoma with proliferation resembling Sertoli cell tumor.

A gonadoblastoma containing a proliferation of the sex cord element resembling a Sertoli cell tumor was found in the dysgenetic gonad of a 19-year-old Japanese phenotypic woman whose karyotype was 46 XY. The tumor was a solid mass 9 cm in maximal dimension composed of gonadoblastoma, dysgerminoma, and a proliferative sex cord element resembling a Sertoli cell tumor. Transitions between the gonadoblastoma nests and the sertoliform element were observed. These findings suggest that the sex cord element of gonadoblastoma can progress to an independent sex cord tumor.

Adult↗

PubMed2000

Cell cycle regulation of the tobacco ribonucleotide reductase small subunit gene is mediated by E2F-like elements.

Ribonucleotide reductase (RNR) is a key enzyme involved in the DNA synthesis pathway. The RNR-encoded genes are cell cycle regulated and specifically expressed in S phase. The promoter of the RNR2 gene encoding for the small subunit was isolated from tobacco. Both in vivo and in vitro studies of the DNA-protein interactions in synchronized BY2 tobacco cells showed that two E2F-like motifs were involved in multiple specific complexes, some of which displayed cell cycle-regulated binding activities. Moreover, these two elements could specifically interact with a purified tobacco E2F protein. Involvement of the E2F elements in regulating the RNR2 promoter was checked by functional analyses in synchronized transgenic BY2 cells transformed with various RNR2 promoter constructs fused to the luciferase reporter gene. The two E2F elements were involved in upregulation of the promoter at the G1/S transition and mutation of both elements prevented any significant induction of the RNR promoter. In addition, one of the E2F elements sharing homology with the animal E2F/cell cycle-dependent element motif behaved like a repressor when outside of the S phase. These data provide evidence that E2F elements play a crucial role in cell cycle regulation of gene transcription in plants.

Base Sequence↗

PubMed1999

Evolution of the HOXB6 intergenic region: motif conservation at the lateral plate mesoderm (LPM) enhancer element.

This study reports the results of a comparative sequencing study in higher primates, focusing on the intergenic region located between HOXB6 and HOXB7. We have examined an 832 bp. region, encompassing a putative Lateral Plate Mesoderm (LPM) enhancer element in a variety of anthropoid apes. The interspecific comparisons reveal extensive substitutions occurring within this region, with a marked bias in favor of C-->T transitions within the enhancer element. The pattern of these substitutions suggests that the LPM enhancer region is subject to specific sequence and compositional constraints that are only revealed through comparative sequencing. These constraints produce an enhancer signature, the CpG microisland, which may be useful in identifying additional regulatory elements located within the HOX complexes. J. Exp. Zool. (Mol. Dev. Evol.) 285:170-176, 1999.

Animals↗

PubMed1996

Mixed tumour of the vagina.

A 33-year-old Japanese woman presented with a polypoid 2.5 x 2.5 x 1.9 cm mass located in the posterior wall of the lower vagina. Microscopically, the tumour was composed of benign epithelial and stromal-type elements. Predominant epithelial elements were mucinous glands with squamous metaplasia and islands of mature squamous epithelium. The stromal-type cells showed reticular or short fascicular patterns with a transition to the epithelial elements. There was no dual epithelial-myoepithelial combination in the glands as seen in so-called mixed tumours (pleomorphic adenomas) of the salivary gland. Immunohistochemically, the epithelial elements were strongly positive for cytokeratin, PKK1 and epithelial membrane antigen, while the stromal-type cells co-expressed PKK1 and vimentin. Staining for S-100 protein, muscle actin, alpha-smooth muscle actin, desmin, and CD34 was uniformly negative in the tumour cells. The DNA pattern was diploid. The patient is alive and well without recurrence for 50 months after excision. These results indicate that an epithelial cell proliferation, probably of the remnant vestibular gland, plays a major role in the development of mixed tumours of the vagina.

Adenoma, Pleomorphic↗

PubMed2026

Comparative analysis of conserved non-coding elements identifies gene regulatory networks rewired during the water-to-land transition in vertebrates.

The conquest of land by vertebrates has been a pivotal moment in evolutionary history. Adapting to the new habitats necessitated numerous changes in vertebrate anatomy and physiology, creating an enduring imprint on the developmental gene regulatory networks (GRNs) of tetrapods. The increase of high-quality genomic resources over the past decade has made it possible to study the genomic legacy of the water-to-land transition. While much attention has been given to the highly conserved non-coding elements (CNEs) of the genome that share high levels of similarity across evolutionarily diverged clades, recent evidence suggests that perhaps comparable attention should be given to "missing" CNE-s, conserved sequence patches present in extant stem gnathostomes and actinopterygian fishes that have become undetectable in tetrapods during the adaptation to terrestrial life, whether through true sequence loss or divergence beyond alignability. These sequences could help us reveal the relaxation of certain developmental constraints, related to the aquatic lifestyle, that made reaching new adaptive peaks in the developmental landscape possible. In this paper, we search for such CNEs and characterize them in comparison with pan-Gnathostome CNEs, using the zebrafish (Danio rerio) genome as a reference. Our results suggest that the rewiring of developmental networks related to pigmentation and muscle structure formation has left the largest genomic imprint. We also find that components of canonical Wnt and Hedgehog signalling, are enriched among CNEs retained in fish.

cis-regulatory evolution↗

PubMed1996

Computational evolution of a model polymer that folds to a specified target conformation.

A method is described for folding polymers to specific target conformations. The approach uses a fast but approximate dynamics algorithm, coupled with a genetic algorithm that is used to evolve the large number of free parameters needed. The dynamics algorithm uses a state transition matrix approach. At each time step, the distances between pairs of atoms are adjusted by shifting them from Dij to Dij + Sij where Sij is an element of the state transition matrix S. Atom pairs that are attractive have Sij < 0 and pairs that are repulsive have S ij > 0. The atomic movement is carried out by gradient minimizing the molecular mechanics energy of the molecule subject to harmonic distance constraints. The method is applied to a simple test case, a 19 atom 2-D polymer. The paper also show that the S matrices can correctly fold a limited variety of initial conformations that differ from the one used during the evolution phase.

Algorithms↗

PubMed1997

A fundamental step-transition in retinal function at low light intensities.

There appears to be a fundamental step-transition in retinal function at low light intensities, close to the scotopic-mesopic transition. This step-transition is observed for elements of the retinal dark-light switch, which has been described in the chicken retina. Over the same range of light intensities, there is a step-transition in photoreceptor retinomotor movements and in the coupling of horizontal and All amacrine cells, which suggests a switch in retinal circuitry from rod-processing to cone-processing regimes. A similar step-transition in pineal function suggests that the retinal step-transition signals to the central circadian systems. Finally, this step-transition may also inhibit eye growth, and thus be responsible for the reported diurnal rhythm in eye growth. Disturbances to this step-transition may be the initial cause of disordered eye growth in the form-deprivation myopia paradigm.

Adaptation, Ocular↗

PubMed2001

X-ray magneto-optics in lanthanides.

Magneto-optical methods in the visible light regime generally lack element specificity, which has become a considerable shortcoming in research on advanced heteromagnetic systems. Using circularly polarized soft x rays tuned to a 4d-4f core-level transition of a lanthanide element, the specularly reflected x-ray intensity changes proportionally to the magnetization of this element and, e.g., hystereses are easily measured element specifically. In contrast to the case of visible light, temperature dependent 4d-4f magneto-optical signals are not influenced by the thermal lattice expansion.

Journal Article↗

PubMed2006

The brain differentiates human and non-human grammars: functional localization and structural connectivity.

The human language faculty has been claimed to be grounded in the ability to process hierarchically structured sequences. This human ability goes beyond the capacity to process sequences with simple transitional probabilities of adjacent elements observable in non-human primates. Here we show that the processing of these two sequence types is supported by different areas in the human brain. Processing of local transitions is subserved by the left frontal operculum, a region that is phylogenetically older than Broca's area, which specifically holds responsible the computation of hierarchical dependencies. Tractography data revealing differential structural connectivity signatures for these two brain areas provide additional evidence for a segregation of two areas in the left inferior frontal cortex.

Adult↗

PubMed1998

[Repositioning social work with the elderly? Effect of competitive elements and new guidance models on the profile of a profession].

The article discusses changes in the context within which the social professions are exercised. The chances for a refinancing of social work and indeed its very locations change in line with the transition to new steering elements in the social body and the new implementation of competitive elements in the realm of public law. With the economising of the social sphere social work is questioned under economic aspects. Simultaneously it gains normative significance. This is true with regard to standards for the quality of services and institutions, and further in the context of the discussion concerning the revitalisation of local social policy for the elderly. Precisely the economising of the social sphere raises the question whether the municipalities may be excused from their responsibility to form, preserve and support the obligations of social work with the elderly. This article denies this.

Aged↗

PubMed1999

A P element has induced intron formation in Drosophila.

We report evidence supporting the hypothesis that some introns could be originated from transposable elements. In the Drosophila montium species subgroup, we recently described a novel example of domestication by the host genome of a P transposable element. The element is a unique truncated P sequence transcribed into a polyadenylated RNA encoding a putative 66-kDa transposition repressor-like protein. Here, we analyze the genomic modifications associated with this transition of a transposable element into a stationary gene that is useful for the host. Study of the transcription modalities of this neogene reveals that the new transcriptional unit harbors a de novo synthesis of a new exon and a new intron upstream of the original P sequence initiation site. The new exon was constructed from the genomic flanking sequence of the P sequence, whereas the first half of the new intron is composed of genomic flanking sequence and the second half is composed of P sequence. This domestication event has involved the capture of a new promoter. An investigation of a large number of species belonging to the melanogaster species group revealed that this P element domestication is restricted to the species of the montium subgroup and that the new exon-intron structure is present in at least three other species. From sequence data, we hypothesize that cryptic acceptor and donor splicing sites present on the P element and flanking sequences have been under selective constraints which have led to the emergence of a new intron.

Animals↗

PubMed2000

Valence state mapping of cobalt and manganese using near-edge fine structures

The properties of transition metal oxides are related to the presence of elements with mixed valences. The spectroscopy analysis of the valence states is feasible experimentally, but a spatial mapping of valence states of transition metal elements is a challenge to existing microscopy techniques. In this paper, with the use of valence state information provided by the white lines and near-edge fine structures observed using the electron energy-loss spectroscopy (EELS) in a transmission electron microscope (TEM), a novel experimental approach is demonstrated to map the valence state distributions of Mn and Co using the ratio of white lines in the energy-filtered TEM. The valence state map is almost independent of specimen thickness in the thickness range adequate for quantitative EELS microanalysis. An optimum spatial resolution of approximately 2 nm has been achieved for a two-phase Co oxides.

Journal Article↗

PubMed2002

Thermodynamics and folding kinetics analysis of the SH3 domain form discrete molecular dynamics.

We perform a detailed analysis of the thermodynamics and folding kinetics of the SH3 domain fold with discrete molecular dynamic simulations. We propose a protein model that reproduces some of the experimentally observed thermodynamic and folding kinetic properties of proteins. Specifically, we use our model to study the transition state ensemble of the SH3 fold family of proteins, a set of unstable conformations that fold to the protein native state with probability 1/2. We analyze the participation of each secondary structure element formed at the transition state ensemble. We also identify the folding nucleus of the SH3 fold and test extensively its importance for folding kinetics. We predict that a set of amino acid contacts between the RT-loop and the distal hairpin are the critical folding nucleus of the SH3 fold and propose a hypothesis that explains this result.

Amino Acid Sequence↗