bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heterogeneity of fiber and sarcomere length in the human masseter muscle
Authors: van Eijden Theo M. G. J. , Raadsheer Maarten C. 
Published: May 2005

AbstractThis study deals with regional differences in the architectural design of the human masseter muscle. For a number of defined muscle regions the three‐dimensional corrdinates of origin and insertion points, and the lengths of the muscle fibers and the sarcomeres were determined in the closed jaw position. Measurements were made from cadavers and the data were used as input for a model predicting sarcomere length at other mandibular positions. At a closed jaw average muscle fiber length of the muscle regions ranged between 19.0–30.3 mm. The fibers appeared to be considerably longer (35%) anteriorly than posteriorly in the muscle, and deeply situated fibers were on average 5% shorter than superficially situated ones. Average sarcomere length of the regions ranged between 2.27–2.55 μm, indicating that at a closed jaw position sarcomeres are at suboptimum length and have different positions on the length‐tension curve. In the deep layer of the muscle sarcomeres were significantly shorter (6%) than in the superficial layer. Within the superficial layer sarcomere lengths did not differ significantly, but in the deep layer sarcomeres were shorter (8%) posteriorly than anteriorly in the muscle. The model shows that jaw displacement had a different effect on sarcomere length in the muscle regions. When the jaw was rotated about a transverse axis (open/close rotation) sarcomere excursions were relatively small in the posterior muscle regions and large in the anterior regions. The reverse was true when the jaw was rotated contralaterally about a vertical axis. It is concluded that, due to heterogeneity in fiber and sarcomere lengths, the distribution of maximal isometric tension across the muscle at full effort is not uniform.
Spatial distribution of “tissue‐specific” antigens in the developing human heart and skeletal muscle III. An immunohistochemical analysis of the distribution of the neural tissue antigen G1N2 in the embryonic heart; implications for the development of the atrioventricular conduction system
Authors: Wessels A. , Vermeulen J. L. M. , Verbeek F. J. , Virágh S. Z. , Kálmán F. , Lamers W. H. , Moorman A. F. M. 
Published: May 2005

AbstractA monoclonal antibody raised against an extract from the Ganglion Nodosum of the chick and designated GIN2 proves to bind specifically to a subpopulation of cardiomyocytes in the embryonic human heart. In the youngest stage examined (Carnegie stage 14, i. e., 4 1/2 weeks of development) these GIN2‐expressing cells are localized in the myocardium that surrounds the foramen between the embryonic left and right ventricle. In the lesser curvature of the cardiac loop this “primary” ring occupies the lower part of the wall of the atrioventricular canal. During subsequent development, GIN2‐expressing cells continue to identify the entrance to the right ventricle, but the shape of the ring changes as a result of the tissue remodelling that underlies cardiac septation. During the initial phases of this process the staining remains recognizable as a continuous band of cells in the myocardium that surrounds the developing right portion of the atrioventricular canal, subendocardially in the developing interventricular septum and around the junction of the embryonic left ventricle with the subaortic portion of the outflow tract. During the later stages of cardiac septation, the latter part of the ring discontinues to express GIN2, while upon the completion of septation, no GIN2‐expressing cardiomyocytes can be detected anymore. The topographic distribution pattern of GIN suggests that the definitive ventricular conduction system derives from a ring of cells that initially surrounds the “primary” interventricular foramen. The results indicate that the atrioventricular bundle and bundle branches develop from GIN2‐expressing myocytes in the interventricular septum, while the “compact” atrioventricular node develops at the junction of the band of GIN2‐positive cells in the right atrioventricular junction (the right atrioventricular ring bundle) and the (“pentrating”) atrioventricular bundle. A “dead‐end tract” represents remnants of conductive tissue in the anterior part of the top of the interventricular septum. The location of the various components of the avian conduction system is topographically homologous with that of the GIN2‐ring in the human embryonic heart, indicating a phylogentically conserved origin of the conduction system in vertebrates.
Anti‐vimentin monocional antibody recognizes a cell with dendritic appearance in the chicken's bursa of fabricius
Authors: Olah Imre , Kendall Cynthia , Glick Bruce 
Published: May 2005

AbstractThe bursa of Fabricius was studied by immunohistochemical method using anti‐vimentin monoclonal antibody (clone 3B4). This monoclonal antibody indentified a vimentin positive cell in the medulla of the bursal follicle. During the first 2 weeks of life the vimentin positive cells located along the corticomedullary border and later became prominent in the medulla with the exception of a narrow zone adjacent to the corticomedullary border. After hatching the accumulation of vimentin‐type intermediate filaments on one side of the nucleus endowed the vimentin positive cells with a polarized appearance. This “cap‐like” vimentin positive area of the cytoplasm determined the position of the major cell process. Within the medulla the Ia positive secretory dendritic cells contained secretory granules in one of the cell processes. The distribution, shape, and polarized appearance of the vimentin positive cells were identical with that of the secretory dendritic cells. Therefore, the anti‐vimentin monoclonal antibody proved to be useful for identification of the bursal secretory dendritic cells. During rapid bursal growth the number of secretory dendritic cells increased, possibly, by proliferation of vimentin negative secretory dendritic cell precursors located along the corticomedullary border.
Glucocorticoid effects on rabbit fetal lung maturation in vivo: An ultrastructural morphometric study
Authors: Snyder Jeanne M. , Rodgers Helen F. , O'Brien Jean A. , Mahli Nancy , Magliato Susan A. , Durham Paul L. 
Published: May 2005

AbstractMaternal administration of glucocorticoids is known to stimulate fetal lung maturation. In the present study, we used microscopy and stereology to evaluate the morphological effects of maternal glucocorticoid treatment on rabbit fetal lung tissue. Betamethasone was administered to pregnant rabbits on days 25 and 26 of gestation at a dose of 0.2 mg/kg body weight. The animal were sacrificed on day 27 of gestation. Glucocorticoid treatment significantly increased the presumptive airspace in the fetal lung tissue but did not alter the relative proportion of epithelium, connective tissue, or vasculature in the tissue. In addition, glucocorticoid treatment significantly increased the proportion of type II cells in the prealveolar epithelium, increased the rate of phosphatidylcholine synthesis, and increased the content of the major surfactant‐associated protein, SP‐A, in the fetal lung tissue. We could detect no effect of betamethasone on lamellar body crosssectional area, numerical density, or volume density within fetal lung type II cells. Glucocorticoid treatment of the pregnant doe caused a decrease in the volume density of intracellular glycogen and an increase in the volume density of mitochondria in fetal lung type II cells. Betamethasone treatment did not alter the distance between fetal lung epithelial cells and subadjacent connective tissué cells. However, glucocorticoid treatment increased the number of connective tissue foot processes that pierced the epithelial basal lamina. Thus, glucocorticoid treatment of the pregnant doe results in structural changes in the fetal lung tissue, an acceleration of some aspects of type II cell defferentiation, and a concomitant increase in epithelial‐mesenchymal interactions.
Sex determination in humans
Authors: Schafer Alan J. , Goodfellow Peter N. 
Published: May 2005

AbstractIn mammals, the Y chromosome induces testis formation and thus male sexual development; in the absence of a Y chromosome, gonads differentiate into ovaries and female development ensues. Molecular genetic studies have identified the Y‐located testis determining gene SRY as well as autosomal and X‐linked genes necessary for gonadal development. The phenotypes resulting from mutation of these genes, together with their patterns of expression, provide the basis for establishing a hierachy of genes and their interactions in the mammalian sex determination pathway.
Mitochondrial genetics and human disease
Authors: Grossman Lawrence I. , Shoubridge Eric A. 
Published: May 2005

AbstractMitochondria contain a molecular genetic system to express the 13 protein components of the electron transport system encoded in the mitochondrial genome (mtDNA). Defects in the function of this system result in some diaseases, many of which are multisystem disorders, prominently involving highly aerobic, postmitotic tissues. These defects can be caused by large‐scale rearrangements of mtDNA, by point mutations, or by nuclear gene mutations resulting in abnormalities in mtDNA. Although any of these mutations would be expected to produce a similar clinical phenotype by compromising oxidative phosphorylation, the surprising and puzzling result is that different clinical phenotypes are generally associated with specific mtDNA mutations. Moreover, the same mutation can produce a distinct clinical phenotype in different individuals or pedigrees. MtDNA rearrangements are also found in aged individuals, but at a subclinical level, suggesting that normal and pathological processes can differ by the effect of genetic or environmental factors on the error rate of mtDNA replication.
Protein conformation in bacterial spinae
Authors: Coombs R. W. , Verpoorte J. A. , Easterbrook K. B. 
Published: May 2005

AbstractThe far uv circular dichroism (CD) and infrared spectra of bacterial spinae are reported. Estimates of the protein secondary structure were obtained by three‐component curve‐fitting methods supplemented by rank and factor analysis of CD data matrices. Native spinae were shown to contain approximately 88% antiparallel β‐sheet, 7% α‐helix, and 5% unordered structure based on estimates using poly(L‐lysine). Basis CD spectra derived from globular proteins were shown to give unreliable estimates.
Sequence dependence of the circular dichroism of synthetic double‐stranded RNAs
Authors: Gray Donald M. , Liu Jung‐Jen , Ratliff Robert L. , Allen Fritz S. 
Published: May 2005

AbstractWe have synthesized and studied the CD spectra of five new double‐stranded RNA polymers: poly[r(A‐G)·r(C‐U)], poly[r(A‐U‐C)·r(G‐A‐U)], poly[r(A‐C‐U)·r(A‐G‐U)], poly[r(A‐A‐C)·r(G‐U‐U)], and poly[r(A‐C‐C)·r(G‐G‐U)]. Together with previously published spectra of seven other RNA sequences, the spectra of these new sequences provide a library sufficient to approximate the spectra of all other RNA sequences by first‐neighbor formulas and, in addition, give four spectra with which we may test the validity of first‐neighbor approximations. (1) We find that the spectra of RNA sequence isomers are very different, but that the spectra essentially do obey first‐neighbor relationships. (2) We have derived tentative first‐neighbor assignments of negative bands at about 295 and 210 nm in the CD spectra. (3) A test of spectral independence shows that among the 12 polymer spectra there are at least seven significant independent spectral shapes, one less than the eight needed to give the most accurate spectral analysis of an unknown RNA sequence for its first‐neighbor frequencies. (4) Spectra are calculated for RNAs of random base composition, approximating natural RNAs having complex sequences. (5) A T‐matrix of spectral components assigned to the first‐neighbor base pairs is derived from 10 of the spectra. This matrix allows an estimation of the CD spectrum of any other known RNA sequence or an analysis of the spectrum of an unknown sequence for its distribution of first‐neighbor base‐pair frequencies. (6) Test analyses of two of the synthetic polymers and of two natural RNAs set a probable limit on the accuracy of first‐neighbor frequency determinations using this T‐matrix. (7) Finally, we summarize in an appendix the melting temperatures for all the RNA and corresponding DNA sequences; it appears that the Tm values of both DNAs and RNAs approximately obey first‐neighbor relationships.
Spectroscopic studies of random chain and α‐helical polypeptides in hexafluoroisopropanol
Authors: Parrish Joseph R. , Blout Elkan R. 
Published: May 2005

AbstractThe infrared, ultraviolet, circular dichroism, and optical rotatory dispersion spectra of five synthetic polypeptides dissolved in hexafluoroisopropanol are reported. This solvent is useful because it dissolves most proteins and non‐ionic polypeptides and also is transparent in spectral regions critical for polypeptide conformational diagnoses. Poly‐γ‐morpholinylethyl‐L‐glutamamide has random chain type spectra in this solvent, whereas the spectra of poly‐γ‐methyl‐L‐glutamate, poly‐L‐methionine, poly‐ε, N‐Carbo‐benzoxy‐L‐lysine, and poly‐L‐homoserine indicate that these four polypeptides are α‐helical. Small but significant variability between the different α‐helical polypeptides is seen in their circular dichroism spectra and optical rotatory dispersions. An argument is presented that these differences may be due to slight geometry differences between different α‐helices.
Light scattering of bovine serum albumin solutions: Extension of the hard particle model to allow for electrostatic repulsion
Authors: Minton Allen P. , Edelhoch H. 
Published: May 2005

AbstractThe light scattering of bovine serum albumin (BSA) has been measured at protein concentration up to 90 g/L and at pH values between 4.4 and 7.6. The dependence of scattering on both protein concentration and pH may be quantitatively accounted for by a simple extension of the hard‐sphere model for protein solutions [Ross, P. D. & Minton, A. P. (1977) J. Mol. Biol. 112, 437–452] allowing for electrostatic repulsions between molecules. According to the extended model, the radius of the effective hard spherical particle representing BSA varies with the net electrical charge of the BSA molecule in a manner which may be calculated from electrostatic theory.
Kinetics of formation of fibrin oligomers. II. Size distributions of ligated oligomers
Authors: Bale Marsha D. , Janmey Paul A. , Ferry John D. 
Published: May 2005

AbstractHuman fibrinogen was treated with thrombin in the presence of fibrinoligase (Factor XIIIa) and calcium ion at pH 8.5, ionic strength 0.45, and the ensuing polymerization was interrupted at various time intervals (t) both before and after the clotting time (tc) by solubilization with a solution of sodium dodecylsulfate and urea. Aliquots of the solubilized protein were subjected to gel electrophoresis on polyacrylamide gels after disulfide reduction by dithiothreitol and on agarose gels without reduction. The degree of γ‐γ ligation was determined from the former and the size distribution of ligated oligomers, for degree of polymerization x from 1 to 10, from the latter. In some experiments, thrombin was inhibited, after partial polymerization, by p‐nitrophenyl‐p′‐guanidinobenzoate. From these, it was concluded that for thrombin concentration ⩽0.013 units/mL and fibrinoligase ⩾30 mg/L, oligomer assembly is rapid compared with peptide A release and ligation is rapid compared with assembly. Under these conditions, the theory of the first paper of this series describes rather well the time dependences of the degree of γ‐γ ligation, the weight fractions of monomer and small oligomers, and the number‐ and weight‐average degrees of polymerization after solubilization of the staggered overlapped assemblies, each of which splits to give two strands of end‐to‐end ligated oligomers. The theory assumes that the second A peptide is released by thrombin more rapidly than the first by a factor q, which, from the experimental data, is determined to be 16. The subsequent assembly into staggered overlapped oligomers follows the statistics of linear polycondesation taking into account the presence of both difunctional and monofunctional combining units. For higher thrombin or lower fibrinoligase concentrations, ligation fails to keep pace with oligomer assembly, and the size distributions after solubilization show a higher proportion of very small and a lower proportion of larger ligated oligomers, owing to separation of the staggered overlapped assemblies into smaller fragments.
Lysinium, argininum, glutamate, and aspartate ions in water solution
Authors: Ranghino Graziella , Clementi Enrico , Romano Silvano 
Published: May 2005

AbstractSCF‐LCAO‐MO ab initio calculations were carried out for the interaction between a charged amino acid and a water molecule. The results obtained were fitted by an analytical potential function of the atom–atom type, and the corresponding potential surfaces were examined by means of orientationally optimized isoenergy contour maps. Monte Carlo simulations were also carried out on a few selected solute–water clusters at T = 300 K, in order to obtain insight into the solvation structure.
Interaction of poly(X) with poly(U): Alkali metal ion specificity suggests a four‐stranded helix
Authors: Roy Kunal B. , Frazier J. , Miles H. Todd 
Published: May 2005

AbstractInteraction of poly(X) with poly(U) to form a regular, ordered structure has been investigated by uv, CD, and ir spectroscopy. The XU complex exhibits a marked dependence of Tm on the nature of the alkali metal ion present in solution. Stability of the complex is surprisingly high and increases with ionization of X residues at N3. The ir evidence shows the U residues are present as the diketo form and X residues as the 6‐keto‐2‐enolate anion and indicates that the X and U carbonyl groups are vibrationally coupled. A mixing curve exhibits a single minimum, at 1:1, but we conclude that the actual combining ratio is twice this value and that the formula of the complex is X2U2. We propose a model based on a four‐standard helix with size‐specific alkali metal complexing to X and U carbonyl oxygens in the axial channel of the helix. This model and previously suggested two‐stranded structures are evaluated in terms of the physical and chemical properties of the complex.
Secondary structure of polypeptide hormones of the anterior lobe of the pituitary gland
Authors: Makarov A. A. , Esipova N. G. , Lobachov V. M. , Grishkovsky B. A. , Pankov Yu. A. 
Published: May 2005

AbstractThe specific secondary structure of a number of polypeptide hormones of the pituitary gland anterior lobe and their fragments were studied by CD in the peptide bond absorption region and by ir spectroscopy. The state of objects was examined in solvents of different polarity over a wide temperature range as well as in the solid state at different relative humidities. The predominant conformational state of a number of hormones in aqueous solution is shown to represent a left‐handed helix of the poly(L‐proline) II type. The reversible melting process of the left‐handed helical conformation when heated in an aqueous solution appears to be noncooperative. Lowering the temperature stabilizes the left‐handed structure. The transition mode of the left‐handed form to the α‐, and the β‐forms on changing the solvent conditions was also studied. Contributions of peptide chromophores and of the aromatic amino acid side‐group chromophores with CD bands in the region under study were determined by analysis of CD spectra. The data obtained allow correlating the conformation of separate fragments in the hormone chain with functional activity.
Cyclic peptides revisited
Authors: Madison Vincent 
Published: May 2005

AbstractA multistep computational scheme was used to deduce possible conformations for a cyclic antagonist analog of somatostatin that has been reported by Coy and coworkers. An algebraic algorithm was used to find dihedral angles that give cyclic structures, the energy was computed for these structures, the lower‐energy structures were classified into conformational families, the energy was minimized for the lowest‐energy member of each family, and finally, the structures from energy minimization were reclassified. Analysis revealed seven distinct conformational families that contain reverse turns. The families differ in the position of the turns in the primary sequence; frame‐shifted turns are observed at each possible position.
Sequence‐Dependence of secondary structure formation: Conformational studies of host–guest peptides in α‐helix and β‐structure supporting media
Authors: Mutter M. , Maser F. , Altmann K.‐H. , Toniolo C. , Bonora G. M. 
Published: May 2005

AbstractA newly designed host–guest approach is introduced as a experimental tool to explore the relationship between the sequence of peptides and their secondary structure. From the CD spectra of the host–guest peptides studied, a tentative scale for the α‐helix potential in 2,2,2‐trifluorethanol of guest amino acids is delineated. The conformational preferences are also examined in β‐structure supporting media (solid state, CH2Cl2, CH3OH, H2O) using ir‐absorption and CD techniques. Scales for the β‐forming tendency of guest amino acid residues in the different media are delineated. It is shown that the preferred conformation of the host–guest peptides is a function of the medium, the chain length, and the protecting groups. Given the fact that conformational effects are important in peptide synthesis, the tentative scales may serve as a guideline to predict secondary structures of side‐chain‐protected or ‐deprotected peptides in a given solvent, complementing the well‐known empirical conformational prediction parameters.
Molecular recognition. I. Automatic identification of topographic surface features
Authors: Lee Richard H. , Rose George D. 
Published: May 2005

AbstractThe phenomenon of molecular recognition depends strongly on surface complementarity between associating molecular units, analogous to the assembly of a three‐dimensional jigsaw puzzle. The driving force for association is solvent entropy, which increases when protrusions of the irregular surface of one subunit fit snugly into invaginations of the other, squeezing out intervening water. To model this process, an algorithm is presented that automatically finds the prominent topographic surface features of rigid α‐helices in proteins of known structure. When the algorithm was applied to two interacting helices from flavodoxin, only a small number of such features were found, and they accounted for the observed complementarity. Using this algorithm, molecular docking can be reduced to a tractable problem by a docking strategy based on exhaustive trial of combinations of surface features.
β‐Turn structure and intramolecular interaction of tetrapeptides containing Asp and Lys
Authors: Ishii H. , Fukunishi Y. , Inoue Y. , Chûjô R. 
Published: May 2005

AbstractNmr and CD studies of terminally protected tetrapeptides were carried out in aqueous and DMSO solutions to investigate the formation and stabilization of the β‐turn structure. Boc‐Gly‐Lys‐Asp‐Gly‐OMe and Boc‐Asp‐Lys‐Asp‐Gly‐OMe appear to have a tendency to adopt a β‐turn structure in aqueous solution from the CD spectra and temperature‐dependence studies of the amide proton chemical shifts. The side‐chain conformation of the Asp residue depends greatly on its ionization state but was not affected by the deprotonation of the neighboring Lys side chain. There is evidence for an intramolecular interaction between the Asp and Lys side chains of Boc‐Gly‐Lys‐Asp‐Gly‐OMe. Such an interaction can contribute to the stabilization of the β‐turn structure.