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PubMed1991

[Synthesis of partial structure of complex types of N-glycoproteins].

Comparable syntheses of beta-D-GlcpNAc-(1----2)-[beta-D-GlcpNAc-(1----6)]-alpha-D-Manp-(1- ---6)-beta-D-ManpO(CH2)8CO2Me and beta-D-GlcpNAc-(1----2)-alpha-D-Manp-(1----3)-beta-D-ManpO(C H2)8CO2Me with the glycosyl halide and imidate methods were investigated. 3,4,6-Tri-O-acetyl-2-deoxy-(2,2,2-trichloroethoxycarbonylamino)-al pha-D-glucopyranosyl bromide or trichloroacetimidate are suitable glycosyl donors for beta-D-glycoside coupling with secondary hydroxyl groups.

Carbohydrate Sequence↗
PubMed1990

Mucinous cystic neoplasm of the pancreas. Estimation of grade of malignancy with imaging techniques and its surgical implications.

The results of diagnostic imaging procedures, macroscopic and microscopic findings and clinical follow up data of 20 mucinous cystic neoplasms of the pancreas were retrospectively reviewed to determine the grade of malignancy and its surgical implications. The largest mean diameter was 8.9 cm for 10 malignant cases, 5.0 cm for two premalignant cases, and 3.1 cm for eight benign tumours. Ultrasonography or computed tomography or both, corresponded well with macroscopy. The 10 malignant and two premalignant lesions had intracystic mural nodules or extracystic solid components, while the eight benign specimens had neither nodules nor solid portions. Structural complexity seen on ultrasonography or computed tomography, which reflected the irregularity in size and shape of the cysts, internal septa, walls, and solid components, was severe in the 10 malignant and two borderline tumours and mild or moderate in the eight benign lesions. Angiography showed that five of the nine malignant tumours were hypervascular, while the two premalignant and four benign lesions were all avascular. Five of 10 patients with malignant tumours died of local recurrence or remote hematogenous metastases, and one with malignant disease was still alive with liver metastases at the time of writing. We propose that a careful preoperative estimate of the malignant potential of such cysts should be made based on the size of the tumour, the presence of mural nodules and solid areas, and the structural complexity on ultrasonography or computed tomography, as well as the amount of vascularity seen on angiography. Attention should be paid at follow up to the presence of local recurrence and haematogenous metastases in cases of malignant disease.

Adenocarcinoma, Mucinous↗
PubMed1991

Candida albicans mycelial wall structure: supramolecular complexes released by zymolyase, chitinase and beta-mercaptoethanol.

Different techniques released from the wall of Candida albicans mycelial cells high molecular weight mannoprotein materials with different levels of complexity. SDS solubilized among others one protein of 180 kDa which reacted with a monoclonal antibody (MAb) specific of a O-glycosylated protein secreted by regenerating mycelial protoplasts [Elorza et al. (1989) Biochem Biophys Res Commun 162:1118-1125]. Zymolyase, chitinase and beta-mercaptoethanol, released different types of high molecular highly polydisperse mannoprotein materials (greater than 180 kDa) that also reacted with the same MAb. These materials had N-glycosidically linked sugar chains, in addition to the O-glycosidically bonded sugars, as their molecular masses were significantly reduced by Endo H digestion. Besides, the specific materials released by either zymolyase or chitinase seemed to be the same throughout the process of germ tube formation. Transmission electron microscopy of thin sections of cells and walls showed that mannoproteins and chitin are evenly distributed throughout the entire cell wall structure.

Blotting, Western↗
PubMedDate not supplied

[DNA interaction with low molecular ligands of different structure. II. Complexes of DNA with actinomine and its analogs].

DNA-complexes with actinomine and its analogues containing omega-dialkylaminoalkyl groups at 1,9 positions of the phenoxazone moiety were studied by technique of spectrophotometry, viscometry and flow birefringence. In the process of spectrophotometry titration two groups of spectra corresponding to different DNA--ligand ratio in a complex were observed. According to the experimental data the investigated compounds are bounded to DNA by means of intercalation and external binding. There within a region of low degrees of binding the intercalation type of the ligand--DNA interaction prevails. In virtue of the spectrophotometry data the intercalation binding share was calculated. The intrinsic viscosity of a complex increases in the case of ligand intercalation and does not change as it joins to the DNA double-helix from outside. Optical anisotropy of DNA molecule increases linearly irrespective of the way of ligand binding. Data on the flow birefringence permits to conclude that under external binding the angle between the normal to the ligand chromophore plane and the axis of DNA double-helix is about zero. During ligand intercalation the equilibrium rigidity of DNA molecules increases.

Chemical Phenomena↗
PubMed1995

Modal and temporal analysis of head mathematical models.

The basic hypotheses used during these investigations were based on the vibration analysis of the head, which demonstrated that the head is not a solid nondeformable body, but a complex structure including deformable elements. Laboratoire des Systemes Biomecanique (LSBM) has recently proposed three mathematical models: a lumped model, a finite element model of the head in its sagittal plane, and a three-dimensional finite element model. These models were validated by their modal behavior and enabled the lesion mechanisms to be distinguished as a function of the spectral characteristics of the shock. The objective of this study is to complete these modal results by temporal analysis of the models by calculating the evolution of the intracranian mechanical parameters under shock conditions. To describe the head's dynamic behavior in the temporal domain, constant energy shocks of variable duration were simulated to evaluate their influence on different quantities as the intracerebral stresses in terms of compression, tensile, and shearing stresses, the relative brain-skull displacement, and the skull deformation. The importance of modal behavior of the head is illustrated by analyzing its temporal response to variable duration impacts, thus exciting very different frequencies. For a triangular shock, the critical duration times are between 10 and 15 x 10(-3) s, which correspond to impacts that excite the first resonance frequency of the head. Taking modal behavior into consideration in developing the finite element model leads to a harmonization of the calculated intracerebral stresses, even for short duration shocks. So, when the head is considered as a complex structure made up of several deformable elements, risk limitation is conditioned by an impact energy reduction for frequencies close to the natural frequencies of the structure. In the time field, the objective will be to avoid a number of impact shapes and durations. Therefore, the aim will not be to dampen the impact at any cost, but to damper it in an "intelligent" manner. In the future, this will allow the reduction of an injury mechanism-related risk, without increasing the risk of an injury generated by another mechanism.

Biomechanical Phenomena↗
PubMed1986

The sucrase-isomaltase complex: primary structure, membrane-orientation, and evolution of a stalked, intrinsic brush border protein.

The complete primary structure (1827 amino acids) of rabbit intestinal pro-sucrase-isomaltase (pro-SI) was deduced from the sequence of a nearly full-length cDNA. Pro-SI is anchored in the membrane by a single 20 amino acid segment spanning the bilayer only once. The amino-terminal, cytoplasmic domain consists of 12 amino acids and is not preceded by a cleaved leader sequence. This suggests a dual role for the membrane-spanning segment as an uncleaved signal for membrane insertion. This is followed by a 22 residue serine/threonine-rich, probably glycosylated, stretch, presumably forming the stalk on which the globular, catalytic domains are directed into the intestinal lumen. Following this is a high degree of homology between the isomaltase and sucrase portions (41% amino acid identity), indicating that pro-SI evolved by partial gene duplication.

Amino Acid Sequence↗
PubMed1996

Affinity and structure of complexes of tropomyosin and caldesmon domains.

The interaction of caldesmon domains with tropomyosin has been studied using x-ray crystallography and an optical biosensor. Only whole caldesmon and the carboxyl-terminal domain of caldesmon (CaD-4, chicken gizzard residues 597-756) bound to tropomyosin with greater than millimolar affinity at 100 and 150 microM salt. Under these conditions the affinities of whole caldesmon and CaD-4 were both in the micromolar range. Data from the x-ray studies showed that whole caldesmon bound to tropomyosin in several places, with the region of tightest interaction being at tropomyosin residues 70-100 and/or 230-260. Studies with CaD-4 revealed that this region corresponded to the strong binding site seen with whole caldesmon. Weaker association of other regions of caldesmon to tropomyosin residues 180-210 and 5-50 was also observed. The results suggest that the carboxyl-terminus of caldesmon binds tightly to tropomyosin and that other regions of caldesmon may interact with tropomyosin tightly only when they are held close to tropomyosin by the carboxyl-terminal domain. Four models are presented to show the possible interactions of caldesmon with tropomyosin.

Animals↗
PubMed1991

Characterization of the memory gene dunce of Drosophila melanogaster.

The dunce (dnc) gene of Drosophila melanogaster encodes cAMP phosphodiesterase (PDEase) and is required for learning/memory and female fertility. The gene is structurally complex, demonstrated in part by Northern blotting experiments which detected multiple RNAs ranging in size from 4.2 to 9.6 kb (1 kb = 10(3) bases or base-pairs). To characterize these RNAs and to understand their sequence heterogeneity, we isolated and analyzed 29 new and independent cDNA clones representing the dnc RNAs. Restriction mapping, hybridization analysis and sequence determination of these cDNA clones and the corresponding genomic exons resolved these into six different classes. Exons defined by the cDNA clones are distributed over more than 148 kb of genomic DNA, with some exons being used alternatively among the RNAs. The RNAs are transcribed from at least three initiation sites: two of these were mapped by parallel S1-nuclease and primer extension experiments. In addition, some of the heterogeneity is generated by using varying lengths of a 3'-untranslated trailer sequence. Altogether, the results indicate that the size and sequence heterogeneity of dnc transcripts results from transcription initiation at multiple sites, alternative splicing, and processes which generate different 3' ends. The existence of multiple protein products is suggested by the alternative use of exons which code for portions of the open reading frame. The protein variation potentially includes N-terminal differences coded for by transcript-specific 5' exons and internal differences arising from the optional inclusion of a 39 base-pair exon and from the alternative use of two 3' splice sites separated by six base-pairs. Expression of a cDNA clone in yeast containing a large portion of the open reading frame produced cAMP PDEase activity identical in properties to the Drosophila enzyme affected by the dnc mutation. The results suggest that the remarkable structural complexity of dnc may reflect an intricate control of the spatial and/or temporal expression of various isoforms of cAMP PDEase.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1984

HLA-A2 antigen phosphorylation in vitro by cyclic AMP-dependent protein kinase. Sites of phosphorylation and segmentation in class i major histocompatibility complex gene structure.

The heavy chain of the HLA-A2 antigen is phosphorylated by cyclic AMP-dependent protein kinase at two serine residues of the intracellular region. Limited proteolysis was performed on purified [32P]HLA-A2 antigens in order to define the sites of phosphorylation. Both of the phosphorylated serine residues are located in the carboxyl terminus of the heavy chain; one is encoded by exon 5, while the other is encoded by exon 6. The phosphoserine encoded by exon 5 is part of the conserved sequence Arg-Arg-Lys-Ser-Ser. This protein sequence contains the proper arrangement of amino acids for recognition and phosphorylation by the catalytic subunit of cyclic AMP-dependent protein kinase. In the murine class I antigens (H-2), exon 5 encodes a similar sequence of basic residues followed by one intervening residue and a threonine rather than a serine residue in the last amino acid position. A composite figure is presented that compares the carboxyl-terminal sequences of human and murine class I antigens and illustrates the known sites of phosphorylation recognized by various kinases. Each site of phosphorylation in the carboxyl terminus is contained within a conserved protein sequence encoded by one of the three exons. A separation and preservation of unique sites of phosphorylation could explain why there is segmentation in the genomic arrangement of class I molecules.

Amino Acid Sequence↗
PubMedDate not supplied

Imaging of complex NMR spectra.

The Point Spread Function (PSF) in NMR imaging is the result of both the line broadening due to magnet field inhomogeneity and the intrinsic spectrum of the nucleus at resonance. In the case of proton imaging, the line broadening dominates the small chemical shifts and the spectral lines are not resolved. This is not generally the case with other nuclei having strong chemical shifts and the PSF then has a complex structure. During imaging, the complex PSF is convolved with the spatial distribution of the nucleus at resonance and this leads to halo artifacts which are dependent on the imaging technique employed. The images due to the ensemble of spectral lines can be separated in principle by deconvolution of the data with the PSF before reconstruction. In the special case where the complex PSF is spatially independent, it can be obtained from the Free Induction Decay (FID) data produced in the absence of a spatially encoding gradient field. This technique has been successfully applied to in-vivo imaging of exogenous perfluorocarbon material.

Animals↗
PubMed1992

Drug binding to higher ordered DNA structures: netropsin complexation with a nucleic acid triple helix.

We have used a combination of spectroscopic and calorimetric techniques to characterize how netropsin, a ligand that binds in the minor groove of DNA, influences the properties of a DNA triple helix. Specifically, our data allow us to reach the following conclusions: (i) netropsin binds to the triplex without displacing the major-groove-bound third strand; (ii) netropsin binding to the triplex exhibits a lower saturation binding density (7.0 base triplets per netropsin bound) than netropsin binding to the corresponding duplex (5.5 base pairs per netropsin bound); (iii) the netropsin-free and the netropsin-bound triplexes each melt in two well-resolved transitions, initial conversion of the triplex to the duplex state followed by duplex melting to the component single-stranded states; (iv) netropsin remains bound to DNA as the triplex melts to the duplex state; (v) netropsin binding thermally destabilizes the triplex in equilibrium with duplex equilibrium dramatically, while thermally stabilizing the duplex to single-strand equilibrium; (vi) netropsin binding to the triplex is enthalpically 4 times more favorable (more exothermic) than netropsin binding to the corresponding duplex; (vii) netropsin binding to the triplex decreases the cooperativity of the triplex----duplex melting event. These results demonstrate that occupancy of the minor groove of a triplex by a ligand such as netropsin can exert a profound impact on the properties of the host triplex, particularly with regard to the equilibrium in which the third strand is expelled from the major groove. Thus, our results reveal considerable major groove/minor groove crosstalk. Such knowledge may prove of practical importance by providing an approach for modulating the affinity and specificity of major-groove-binding third strands in triplex-forming protocols designed to target specific duplex domains. Fundamentally, our results provide insights into the crosstalk that can result when ligands bind to the two major receptor sites of duplex DNA--namely, the major and minor grooves.

Calorimetry, Differential Scanning↗
PubMed1983

Solution conformation of asparagine-linked oligosaccharides: alpha(1-6)-linked moiety.

The solution conformation is presented for representatives of each of the major classes of asparaginyl oligosaccharides. In this report the conformation of the alpha(1-6)-linked moiety is described. The conformational properties of these glycopeptides were determined by high-resolution 1H nuclear magnetic resonance in conjunction with potential energy calculations. The NMR parameters that were used in this analysis were chemical shifts and nuclear Overhauser enhancements. Potential energy calculations were used to evaluate the preferred conformers available for the different linkages in glycopeptides and to draw conclusions and to draw conclusions about the behavior in solution of these molecules. For all classes, identical conformations were found for the 6-arm except for the torsional angle, omega, about the C5-C6 bond of the alpha 1-6 linkage. For high mannose and hybrid structures omega was found to be -60 degrees, for bisected biantennary complex structures omega was 180 degrees, and for complex biantennary structures averaging between -60 degrees and 180 degrees occurs.

Asparagine↗
PubMed1997

T-cell receptor structure and TCR complexes.

The first crystal structures of intact T-cell receptors (TCRs) and their complexes with MHC peptide antigens (pMHC) were reported during the past year, along with those of a single-chain TCR Fv fragment and a beta-chain complexed with two different bacterial superantigens. These structures have shown the similarities and differences in the architecture of the antigen-binding regions of TCRs and antibodies, and how the TCR interacts with pMHC ligands as well as with superantigens.

Animals↗
PubMed1979

Complex factorial structure of Ellis' Irrational Beliefs.

Previous research with a newly developed children's scale for measuring Ellis' constructs with regard to irrational beliefs showed that while the scale clearly reflected theoretically predicted developmental trends, the internal consistency reliability of the overall 11-item scale was relatively low (.56). This low internal consistency suggested that the 11 items were in fact heterogeneous and were not measuring a single, univocal, construct. An exploratory factor analysis was performed on the responses of 788 fifth-through thirteenth-grade students. Results of the Alpha factor and analysis clearly indicate that the scale is multifaceted, i.e., comprised of four orthogonal, interpretable factors. Estimates of internal consistency reliabilities for the separate factors, when corrected for length, revealed that each of the new factors was more reliable than the full scale score in this sample. Potential revisions of the scale, as well as cautions for its use in clinical applications on its present form are discussed.

Adolescent↗
PubMed1994

The cuticle of the nematode Caenorhabditis elegans: a complex collagen structure.

The cuticle of the nematode Caenorhabditis elegans forms the barrier between the animal and its environment. In addition to being a protective layer, it is an exoskeleton which is important in maintaining and defining the normal shape of the nematode. The cuticle is an extracellular matrix consisting predominantly of small collagen-like proteins that are extensively crosslinked. Although it also contains other protein and non-protein compounds that undoubtedly play a significant part in its function, the specific role of collagen in cuticle structure and morphology is considered here. The C. elegans genome contains between 50 and 150 collagen genes, most of which are believed to encode cuticular collagens. Mutations that result in cuticular defects and grossly altered body form have been identified in more than 40 genes. Six of these genes are now known to encode cuticular collagens, a finding that confirms the importance of this group of structural proteins to the formation of the cuticle and the role of the cuticle as an exoskeleton in shaping the worm. It is likely that many more of the genes identified by mutations giving altered body form, will be collagen genes. Mutations in the cuticular collagen genes provide a powerful tool for investigating the mechanisms by which this group of proteins interact to form the nematode cuticle.

Amino Acid Sequence↗
PubMed1981

Volume discrimination learning in golden hamsters: effects of the structure of complex rearing cages.

Golden hamsters (Mesocricetus auratus) were reared from birth to adulthood in a spatially diversified situation (EG); their performances were compared with those of other hamsters housed in standard laboratory cages (SG). The task was to discriminate between 2 cubic volumes of different sizes followed by various test situations designed to define the respective parts played by the 3 spatial dimensions during perception. The results show that surfaces of volumes were mainly taken into account by EG subjects whereas width, alone, was used by the SG animals.

Animals↗
PubMed1976

Fine structure of complex ocelli of a cubomedusan, Tamoya bursaria Haeckel.

The retina of the distal and proximal lens-bearing complex ocelli are composed of pigmented sensory cells and long pigmented cells. A ciliary sheath from each sensory cell, together with the processes of long pigmented cells, extends through the vitreous layer as far as the capsule that envelops the lens. Each ciliary sheath has several ballon-like swellings and the ciliary microtubules, arranged in the 9+2 pattern in the proximal part, are markedly disorganized distally in the swollen parts, out of which extends most of the microvilli in the vitreous layer. It is suggested that some of the microvilli may originate in vesicles that are constricted off from the surface of the pigmented sensory cells. Closely packed microvilli run in parallel in short bundles. In addition to characteristic junctions between sensory cells, junctions that are presumably synaptic and, of a new type in coelenterates, are observed between sensory cells and nerve endings.

Animals↗