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PubMedDate not supplied

[Structure of nuclear pre-mRNA. X. New type double-helical structures in the pre-mRNA].

High molecular weight nuclear pre-messenger RNA (pre-mRNA or RNA) isolated from Ehrlich ascites carcinoma cells contains besides moderately long (100--200 base base pairs) snap-back double-stranded structures, also longer double-stranded structure containing at least 300-800 base pairs. Very long double-stranded sequences are not able to snap-back after RNA melting. While the moderately long double-stranded RNS (dsRNA) is renatured at Cot 1/2 approximately or equal to 5 X 10(-4), the very long dsRNA shows a higher complexity (Cot 1/2 approximately or equal to 2 X 10(-2). They also hybridize to a less reiterated class of DNA than moderately long dsRNA. Two classes of dsRNA are represented by different sequences as followed from cross-renaturation experiments. Very long dsRNA forms stable hybrids with 20% of total poly(A)+mRNA of cytoplasm. The properties of different classes of ds structures present in nuclear pre-mRNA are compared and their possible nature is discussed. The presence of very long dsRNA may reflect either the symmetric transcription of structural genes, or the transcription from thos DNA sequences which are complementary to each other but located in different parts of the genome.

Animals↗
PubMed1979

The chemical structure and the crystalline structures of Bombyx mori silk fibroin.

Some recent data (i.e. published in the last ten years) on the chemical and crystalline structures of B. mori silk are reviewed. The main emphasis is put on the crystallizable portion of silk fibroin, including its chemical constitution and its molecular conformation (at the crystallographic unit-cell level) in the two crystalline modifications : the beta pleated sheet and the silk I structures. The structural aspects are based on a discussion of X-ray and electron diffraction data, and on conformational energy analyses of a model (Ala-Gly)n polypeptide of silk fibroin.

Amino Acid Sequence↗
PubMed1978

The structure of carbohydrate chains of blood-group substance. Isolation and elucidation of the structure of higher oligosaccharides from blood-group substance H.

Twenty individual higher reduced oligosaccharides, having from seven to eleven monosaccharide units, were isolated after sodium borohydride degradation of blood-group substance H from pig stomach linings. Anion-exchange high-pressure liquid chromatography appears to be a very convenient and effective method for this kind of higher oligosaccharide mixtures separation. The oligosaccharide structures were determined by means of periodate oxidation, methylation analysis, partial acid and enzymic hydrolysis. It has been found that all the oligosaccharides investigated can be divided into four series. The oligosaccharides belonging to each series have the common oligosaccharide fragment to which terminal L-fucose and/or N-acetyl-D-glucosamine residues are attached. Comparison of all the oligosaccharide structures, including tri, penta and hexasaccharides described earlier, shows that the lower oligosaccharides represent the structural element of the higher oligosaccharides.

ABO Blood-Group System↗
PubMed1978

Study of structural analysis: comparing differential diagnoses based on psychiatric evaluation, the MMPI, and structural analysis of the Hand Test and Rorschach.

Experimental investigation of Structural Analysis compared diagnoses of 30 psychiatric inpatients derived independently from psychiatric evaluations, MMPI analyses, and Structural Analysis interpretation of Hand Test and Rorschach data. Results yielded positive preliminary implications for the use of Structural Analysis in psychodiagnostics.

Adolescent↗
PubMed1977

[Structure and configuration of human tendons. II. Development of tendon structure during ontogenesis].

In infants born in the 24th--30th weeks of the gravidity the praenatal development and the process of the organization of the tendinous structure have been examined by the authors. By means of photo- and polarization microscopic examinations it was found that the tendon of the flexor hand muscles (M. flexor carpi radialis, M. flexor digitorum comm.) shows mature tendinous structure earlier, than the tendons of the flexor muscles of the lower extremity (M. semitendinosus femoris, M. triceps surae). The tendons of the extensor muscles of the lower extremity (M. quadriceps femoris, M. tibialis ant.) are underdeveloped and inordinate in the foetal life--their structure develops only during the postnatal life.

Hand↗
PubMedDate not supplied

[Contribution of individual structural components to stabilization of the secondary structure of double-helical polynucleotides].

Contributions of individual structural components of the double-helical polynucleotide to the stabilization of its secondary structure have been studied. The energy of intramolecular interactions was calculated by the method of atom-atom potentials. Sections of the energy function were constructed according to the parameters determining mutual location of base pairs with the optimal conformation of ribose-phosphate backbone in the points close to A- and B-forms of DNA. A complicated nature of the contribution of different structural components of the polynucleotide to its stabilization was revealed by means of different parameters. Relationships between the change of conformational parameters corresponding to optimal values of energy for A- and B-families of nucleic acids were found.

DNA↗
PubMed1976

Structure and structure-function relationships in glycoprotein hormones.

Relationships between the sequences of thyrotropin (thyroid-stimulating hormone, TSH), lutropin (luteinizing hormone, LH), human choriogonadotropin (chorionic gonadotropin, hCG) and follitropin (follicle-stimulating hormone, FSH) are now well established. Each beta-subunit contains six disulphide bonds and considerable homology is seen when all four linear sequences are aligned with half-cystine residues in juxtaposition. Major questions about the tertiary structures of the subunits and their interactions to form active hormone remain. Determination of the disulphide bridges in both alpha- and beta-subunits has not yielded to usual methods and conflicting data about the alpha-subunit have been reported. Partial reduction of the beta-subunits of LH and TSH with subsequent labelling of the cysteines formed has shown that a single bond is first reduced. This bond is between positions 93 and 100 in LH-beta and the corresponding positions 88-95 in TSH-beta. Thus, as would be expected from the fact that interhormone hybrids can be made with the common alpha-subunits, the chemical data, though still limited, indicate similar tertiary structures for the different beta-subunits. To investigate whether other useful intermediates can be obtained after partial reduction, we have studied reduction and derivative formation in various conditions. Intact LH is more resistant to reduction than either its alpha- or beta-subunit but no intermediates have been observed which are not present after partial reduction of individual subunits. Preliminary experiments on the reoxidation of fully reduced alpha-subunit show that the reoxidized material will recombine with native beta-subunits to yield biologically active TSH or LH. Studies from this and other laboratories on chemical modifications of several amino acid residues of glycoprotein hormones and their subunits are also summarized.

Amino Acid Sequence↗
PubMed1977

Quantitative structure-activity relationships in centrally acting imidazolidines structurally related to clonidine.

The central hypotensive action of clonidine and 26 structurally related derivatives was quantified by means of an ED30 obtained from dose-response curves following intravenous administration to anesthetized, normotensive rats. Multiple regression analyses of the biological data yielded correlation equations comprising a relationship between hypotensive activity and molecular structure. In the equations the pharmacokinetics together with the actual engagement of the central alpha-adrenoceptor are accounted for. More detailed characteristics of this central alpha-adrenoceptor emerged from correlation studies in which new ED30 values, associated with brain concentrations, were employed. The use of this biological parameter at the alpha-adrenoceptor level allowed the presentation of a hypothetical working model for the mechanism of interaction between this receptive site and clonidine-like imidazolidines.

Animals↗
PubMed1978

The fine structure of the ventricular surface of the area postrema of the cat, with particular reference to supraependymal structures.

The ependymal surface of the feline area postrema (AP) has been examined with the scanning and transmission electron microscopes. Particular attention was paid to the distribution and structure of supraependymal (SE) cells which have not been described before on this organ. A population of SE cells was found consistently on the cat AP; they were grouped most frequently toward the caudal aspect of the organ. Their structure bears a great resemblance to that of macrophages, containing: (1) many small apical vacuoles, (2) numerous lysosomes, and (3) phagosome-like bodies. Arrays of microvillous tufts and also singly-occurring microvilli are features of the unciliated ependymal surface of the organ. Tufts are often found in very close proximity to superficial blood vessels which are characteristically surrounded by large perivascular spaces.

Animals↗
PubMed1978

Membrane structural specialization of the toad urinary bladder revealed by the freeze-fracture technique. III. Location, structure and vasopressin dependence of intramembrane particle arrays.

Examination of the toad urinary bladder by freeze-fracture electron microscopy reveals intramembrane particle arrays at a number of membrane sites. An array in which particles are aggregated into closely apposed parallel rows is found in the granular cell luminal membrane of dehydrated toads fixed in situ. These aggregates are structurally indistinguishable from those previously associated with vasopressin exposure in vitro. Aggregates are not found in granular cell luminal membrane in the case of hydrated toads fixed in situ. However, structurally similar arrays are found at low frequency in the membrane of cytoplasmic vacuoles in granular cells and in the plasma membrane of basal cells in both hydrated and dehydrated toads. Aggregates are also present at these sites in control and vasopressin-treated bladders from in vitro experiments. Particle arrays characteristic of gap junctions, desmosomes and hemidesmosomes also occur in the plasma membrane of basal cells. In addition, distinctive square arrays of particles exist in the plasma membrane of the bladder's mesothelium. Although a variety of intramembrane particle arrays exist in the toad urinary bladder, only the occurrence of organized particle aggregates in the luminal membrane of granular cells appears to be associated with vasopressin exposure.

Animals↗
PubMed1979

Subunits of RNA polymerase in function and structure. 7. Structure of premature core enzyme.

The structure of premature core enzyme, an obligatory intermediate in both in vivo and in vitro assembly of Escherichia coli DNA-dependent RNA polymerase, was compared with that of native core enzyme. Though this assembled but inactive form of core enzyme harbors the gross conformation similar to that of native enzyme, minor and presumably local differences exist, which were identified by near-ultraviolet circular dichroism spectra, tritium-hydrogen exchange rate, protease sensitivity, intersubunit cross-linking rate by bifunctional reagents, sedimentation behavior, and elution profile from phosphocellulose. Taken together these results indicate that the core enzyme subunits are loosely associated in the premature core. The temperature-dependent maturation is required for the core subunits to be tightly associated, leading to the formation of structurally stable and functionally active RNA polymerase.

Circular Dichroism↗
PubMed1979

Structure and metabolism of sulphated glycosaminoglycans in cultures of human fibroblasts. Structural characteristics of co-polymeric galactosaminoglycans in sequential extracts of fibroblasts during pulse-chase experiments.

1. Human embryonic lung and skin fibroblasts were allowed to incorporate 32SO42- or 35SO42- and D-[1-3H]glucosamine. After removal of the medium the monolayer was subjected to sequential extractions by using EDTA, brief trypsin digestion, extraction with dithiothreitol ofllowed by freeze--thawing and extraction with trichloroacetic acid. The heparan sulphate and galactosaminoglycan contents of the various extracts were estimated after deaminative cleavage of the former component. Heparan sulphate was the major component of the trypsin digest, whereas galactosaminoglycans were the dominant component of other fractions. 2. Galactosaminoglycans of the various fractions were subjected to chemical (periodate oxidation/alkaline elimination) and enzymic (chondroitinase-AC and -ABC, as well as testicular hyaluronidase) degradations. Galactosaminoglycans from the insoluble cell fraction and the dithiothreitol extract contained larger amounts of L-iduronic acid than did those of other fractions. 3. Pulse-chase experiments were performed with and without replating of the cells at the start of the chase period. Radioactive glycans were isolated from the various extracts during the chase period. The half-lives of glycans of the insoluble cell fraction and the dithioreitol extract were shorter (5--8h) than were those of the trypsin digest and the EDTA extract (22h and 11h respectively). After replating of the cells in chase medium, radioactive cell-associated glycans were secreted from the cells and could be recovered in the trypsin digest, the EDTA extract and the medium. Furthermore, 35S/3H ratios of glycans from all these fractions decreased during the chase period. The following conclusions were reached. The insoluble cell fraction contains the synthesis pool and some structural material, whereas the soluble cell fraction is the storage and degradation pool. The dithiothreitol extract appears to contain the immediate precursors of secreted material. The trypsin-released glycans comprise structural components as well as material destined for pinocytosis or secretion into the medium. The EDTA extract is considered to consist of glycans en route to the medium. 4. The two presumptive precursor pools were preferentially depleted of L-iduronic acid-rich galactosaminoglycans during the chase. Glycans recovered from the trypsin digest, the EDTA extract and the medium during the chase contained larger amounts of periodate-resistant uronic acid residues (D-glucuronic acid and/or L-iduronic acid O-sulphate) than did their precursors. It is proposed that polymer-level modifications of secreted glycans are partly responsible for the results.

Cells, Cultured↗
PubMed1979

Structural studies on the murine Ia alloantigens. V. Evidence that the structural gene for the I-E/C beta polypeptide is encoded within the I-A subregion.

The E/C alpha- and beta-subunits of intra-I-region recombinants were analyzed for primary structural variation by comparative tryptic peptide mapping. The E/C alpha-polypeptides from B10.A, B10.A (3R) and B10.A (5R) showed complete coincident elution of peptides; the E/C beta-chains from B10.A and 3R (or 5R) were approximately 40% different. This suggests that the structural gene for the E/C beta-polypeptide is within the I-A subregion.

Amino Acid Sequence↗
PubMed1979

Fine-structure mapping of the acetamidase structural gene and its controlling region in Aspergillus nidulans.

A large number of amdS mutants altered in acetamide utilization have been used to construct a fine-structure map of the amdS locus. The mutagen diepoxyoctane generated most of the deletion strains used for mapping. A minimum of 14 sites within the amdS gene were found. Biochemical analysis of amdS mutants defined the extent of the probable coding region. A new mutant, amd-205, which did not produce detectable inactive gene product, was found to be inseparable by recombination from the "up-promoter" mutation amdI18 and was located outside of the apparent amdS coding region. The cis-dominant mutation, amdI9, was also located at this end of the gene. This work, therefore, provides evidence for the separation of a eukaryotic gene into controlling and structural regions.

Acetamides↗
PubMed2025

Intertypic Recombination Between Coxsackievirus A16 and Enterovirus A71 Structural and Non-Structural Genes Modulates Virulence and Protection Efficacy.

Background/Objectives: Enterovirus A71 (EV-A71) and coxsackievirus A16 (CVA16) are major causative agents of hand, foot and mouth disease (HFMD), often co-circulating and occasionally undergoing genetic recombination. While natural recombinants often involve genomic regions encoding non-structural proteins, their effects on replication and pathogenesis remain unclear. Methods: To address this, four chimera viruses (Chi-CCE, Chi-ECE, Chi-EEC, and Chi-CEC) were constructed with 5'UTR, capsid P1, and non-structural P2 and P3 genes, from CVA16 (denoted as C) or EV-A71 (denoted as E). These chimeras were tested for replication kinetics and cytopathic effects in rhabdomyosarcoma cells while in vivo virulence and protection efficacy were evaluated using a newborn BALB/c mouse model. Results: All chimeric viruses remained viable and exhibited higher replication than CVA16. In vivo, all chimeric viruses were avirulent except Chi-CCE and CVA16, which showed high virulence and viral titres in the brains and limbs of infected newborn mice. This suggests that 5'UTR and capsid P1 genes of CVA16 are critical genetic determinants of virulence. Notably, only the anti-inflammatory cytokine IL-10 was elevated, suggesting potential immune modulation during infection. Inactivated Chi-CCE immunisation conferred 100% protection against lethal CVA16 or mouse-adapted EV-A71 challenge revealing its potential as a bivalent vaccine candidate. Conclusions: Our study demonstrates that recombination between CVA16 and EV-A71 influences viral virulence and protection efficacy with implications for future development of multivalent vaccines.

coxsackievirus A16↗
PubMed1979

[Rule of antibody structure. Primary structure of a human monoclonal IgAl-immunoglobulin (myeloma protein Tro). VI. Amino acid sequence of the L-chain, lambda-type, subgroup II].

The primary structure of the L-chain of an IgA1-immunoglobulin (Myeloma protein Tro) has been determined by means of cleavage with trypsin and, if necessary, with alpha-chymotrypsin. The tryptic peptides of the variable part were characterized by amino acid analysis, Dansyl-Edman degradation and cleavage with carboxypeptidase; the peptides of the constant part were identified by amino acid analyses and determination of its N- and C-terminal residues. The sequence of the remaining amino acids and the arrangement of the peptides were established in homology to known structures. The protein comprises 216 amino acids. The homology of the variable part clearly characterizes it as belonging to subgroup II of lambda-chains. In positions 27a, b and c, there are the subgroup-specific additional residues and in position 96 is the characteristic deletion. The constant part of the chain is Kern- and Oz- which indicates that it has serine in position 154 and arginine in position 191.

Amino Acid Sequence↗
PubMedDate not supplied

[Spin label study of microviscosity and structural transitions in cell membrane lipids and proteins. I. Heat-induced structural changes in cell nuclei of mouse organs in normal conditions].

With the help of weakly bound spin probes the effect of temperature on structural transitions of protein and lipid components in the nuclei membranes of different organs of intact mice has been studied. Microviscosity of lipids in the membrane is found to differ sharply from proteins. Found by both probes breaks on Arrhenius curve of the correlation time dependence on reverse temperature within the temperature range of 25degreesC--27degreesC and 40degreesC-43degreesC seem to be connected with structural reconstructions of the whole membrane. The results obtained according to the behaviour of probes are identical for the nuclei of different organs.

Animals↗
PubMed1978

[Ultrastructure of Clostridium tetani. I. Structural features of the surface structures of vegetative cells].

Crest-like structures formed by internal layer of cell wall and cytoplasmic membrane were revealed in G1.tetani 471 by electron microscopy with the use of negative contrasting, ultrathin sections and freezing-etching. The transverse section of these crest-like structures was 56.3 nm and they were localized 4 to 6 in one row girdling the protoplast in different directions. Ring-like subunits located in rows with the periodicity of 5.9 nm, perpendicularly to the long axis of the cell, were revealed on the surface of the cell wall.

Cell Wall↗