bluuebunny/crossref_metadata_2025 huggingface dataset:
A change-in-hand mechanism for S100 signalling
Authors: Smith Steven P , Shaw Gary S
Published: April 2011

S100 proteins are a group of small dimeric calcium-binding proteins making up a large subclass of the EF-hand family of calcium-binding proteins. Members of this family of proteins have been proposed to act as intracellular calcium modulatory proteins in a fashion analogous to that of the EF-hand sensor proteins troponin-C and calmodulin. Recently, NMR spectroscopy has provided the three-dimensional structures of the S100 family members S100A6 and S100B in both the apo- and calcium-bound forms. These structures have allowed for the identification of a novel calcium-induced conformational change termed the change-in-hand mechanism. Helix III of the C-terminal calcium-binding loop changes its helix-helix interactions (or handness) with the remainder of the molecule primarily owing to the reorientation of the backbone in an effort to coordinate the calcium ion. This reorientation of helix III exposes several residues in the C-terminus and linker regions of S100B resulting in the formation of a hydrophobic patch surrounded be a number of acidic residues. This site is the proposed region for protein-protein recognition.Key words: S100, calcium-binding protein, EF-hand, conformational change.
NMR studies of DNA duplexes containing alpha-anomeric nucleotides and polarity reversals
Authors: Aramini James M , Germann Markus W
Published: April 2011

We present a summary of our research to date on a family of self-complementary DNA decamers containing single alpha-anomeric nucleotides flanked by 3'-3' and 5'-5' phosphodiester linkages from the perspective of the salient NMR techniques employed to shed light on the structural and dynamic properties of these sequences. Research into this class of synthetic alpha-/ beta-oligonucleotides containing mixed strand disposition may have medical relevance given their recently documented efficacy as antisense therapeutics.Key words: nucleic acid NMR, alpha anomeric, polarity reversals.
Expression, purification, and characterization of the carboxyl-terminal region of the Na+/H+ exchanger
Authors: Gebreselassie Daniel , Rajarathnam Krishna , Fliegel Larry
Published: April 2011

The Na+/H+ exchanger is a pH regulatory protein that is responsible for removal of excess intracellular protons in exchange for extracellular Na+. It is a plasma membrane protein with a large cytoplasmic carboxyl terminal domain that regulates activity of the membrane domain. We overexpressed and purified the cytoplasmic domain that was produced in Escherichia coli. This region (516-815 amino acids) was under control of the tac promoter from the plasmid pGEX-KG and was fused with glutathione S-transferase. Upon induction, the fusion protein was principally found in inclusion bodies. Purified inclusion bodies were solubilized and fractionated using preparative SDS polyacrylamide gel electrophoresis. To obtain free Na+/H+ exchanger protein the fusion protein was dialyzed against cleavage buffer and cleaved at the thrombin cleavage site between glutathione S-transferase and the Na+/H+ exchanger domain. Free Na+/H+ exchanger protein was obtained by rerunning the sample on preparative gel electrophoresis. The final yield of the purified protein was 2.15 mg protein/L of cell culture. After exhaustive dialysis the secondary structure of the purified protein was assessed using circular dichroism spectroscopy. The results indicated that the protein was 35% alpha-helix, 17% beta-turn, and 48% random coil. They suggest that the cytoplasmic domain is structured and some regions may be compact in nature.Key words: Na+/H+ exchanger, pH regulation, membrane protein, circular dichroism.
Differential inhibition of AE1 and AE2 anion exchangers by oxonol dyes and by novel polyaminosterol analogs of the shark antibiotic squalamine
Authors: Alper Seth L , Chernova Marina N , Williams Jon , Zasloff Michael , Law Foon-Yee , Knauf Philip A
Published: April 2011

Oxonol and polyaminosterol drugs were examined as inhibitors of recombinant mouse AE1 and AE2 anion exchangers expressed in Xenopus laevis oocytes and were compared as inhibitors of AE1-mediated anion flux in red cells and in HL-60 cells that express AE2. The oxonols WW-781, diBA(5)C4, and diBA(3)C4 inhibited HL-60 cell Cl-/Cl- exchange with IC50 values from 1 to 7 µM, 100-1000 times less potent than their IC50 values for red cell Cl-/anion exchange. In Xenopus oocytes, diBA(5)C4 inhibited AE1-mediated Cl- efflux several hundred times more potently than that mediated by AE2. Several novel squalamine-related polyaminosterols were also evaluated as anion exchange inhibitors. In contrast to diBA(5)C4, polyaminosterol 1361 inhibited oocyte-expressed AE2 8-fold more potently than AE1 (IC50 0.6 versus 5.2 µM). The 3-fold less potent desulfo-analog, 1360, showed similar preference for AE2. It was found that 1361 also partially inhibited Cl- efflux from red cells, whereas neither polyaminosterol inhibited Cl efflux from HL60 cells. Thus, the oxonol diBA(5)C4 is >100-fold more potent as an inhibitor of AE1 than of AE2, whereas the polyaminosterols 1360 and 1361 are 8-fold more potent as inhibitors of AE2 than of AE1. Assay conditions and cell type influenced IC50 values for both classes of compounds.Key words: band 3, oxonols, squalamine, Xenopus laevis oocytes, HL-60 cells.
Cell lineages in the embryonic kidney: their inductive interactions and signalling molecules
Authors: Sariola Hannu , Sainio Kirsi
Published: April 2011

The first signalling genes acting in the inductive interactions in the kidney have now been identified. Differentiation of the permanent kidney or the metanephros is critically dependent on inductive signalling between the nephrogenic mesenchyme and ureteric bud epithelium. Further inductive interactions occur between developing nephrons, interstitial stroma, endothelial cells and neurones. Glial-cell-line-derived neurotrophic factor is a signal for the ureteric bud initiation and branching, and Wnt4 is an autocrine epithelializing signal at the pretubular stage of nephron formation. The signals for renal angiogenesis and innervation are less well defined, but seem to include vascular endothelial growth factor and neurotrophins, at least. The ureteric-bud-derived signal for induction of the nephrogenic mesenchyme (to bring the cells to the condensate stage) is not yet known, but fibroblast growth factor 2 is a good candidate. None of the signalling genes identified from the embryonic kidney is specific to the organ, which raises some general questions. How do the organs develop from similar rudiments to various patterns with different cell types and functions? Does the information for organ-specific differentiation pathways retain in the epithelial or mesenchymal compartment? The present, rather fragmentary molecular data would favour the view that similar molecules acting in different combinations and developmental sequences, rather than few organ-specific master genes, could be responsible for the divergence of patterning.Key words: inductive tissue interaction, metanephros, apoptosis, signalling molecule, cell lineage, morphogenesis.
Mouse gene trap approach: identification of novel genes and characterization of their biological functions
Authors: Kitajima Kenji , Takeuchi Takashi
Published: April 2011

The mouse gene trap strategy is an insertional mutagenesis involving an exogenous DNA, termed the trap vector, as a mutagen that produces a mutation in the mouse genome and a sequence tag to facilitate the isolation of the mutated genes. The trap vector consists of a reporter gene whose expression mimics that of the endogenous genes mutated and a selection marker that sorts cells bearing the inserted vector. Gene trap is a powerful method for identifying genes important in biological phenomena. Moreover, the method produces mutant organisms whose phenotypes provide invaluable information about the biological functions of the genes responsible for these phenotypes. Indeed, a number of genes essential for mouse embryogenesis have been identified by the gene trap method. Here, we describe the principle, results, and perspectives for applications of gene trap approach to the study of cell differentiation and lineage commitment.Key words: gene trap, embryogenesis, jumonji.
Segregation of the embryonic vascular and hemopoietic systems
Authors: Eichmann Anne , Corbel Catherine , Le Douarin Nicole M
Published: April 2011

The origin of endothelial cells and their subsequent assembly into the primary vascular system have been mostly analyzed in the avian embryo. Following the discovery of specific growth factors and their cognate receptors, the molecular mechanisms underlying these processes have been unraveled in both birds and mammals. In particular, experimental studies of the angiogenic vascular endothelial growth factor (VEGF) and its receptors, carried out in both vertebrate classes, have provided significant insight into the developmental biology of endothelial cells. The VEGF receptor VEGFR2 is the earliest marker known to be expressed by endothelial precursor cells of avian and mouse embryos. Based on the localization of VEGFR2+cells in the avian embryo and on clonal culture experiments, two types of endothelial precursor cells can be distinguished from gastrulation stages onward: posterior mesodermal VEGFR2+hemangioblasts, which have the capacity to differentiate into endothelial and hemopoietic cells, and anterior VEGFR2+angioblasts, which can only give rise to endothelial cells.Key words: hemangioblast, endothelial cell, hemopoietic cell, embryo.
MyoD and Myf-5 define the specification of musculature of distinct embryonic origin
Authors: Kablar Boris , Asakura Atsushi , Krastel Kirsten , Ying Chuyan , May Linda L , Goldhamer David J , Rudnicki Michael A
Published: April 2011

Mounting evidence supports the notion that Myf-5 and MyoD play unique roles in the development of epaxial (originating in the dorso-medial half of the somite, e.g. back muscles) and hypaxial (originating in the ventro-lateral half of the somite, e.g. limb and body wall muscles) musculature. To further understand how Myf-5 and MyoD genes co-operate during skeletal muscle specification, we examined and compared the expression pattern of MyoD-lacZ (258/-2.5lacZ and MD6.0-lacZ) transgenes in wild-type, Myf-5, and MyoD mutant embryos. We found that the delayed onset of muscle differentiation in the branchial arches, tongue, limbs, and diaphragm of MyoD-/-embryos was a consequence of a reduced ability of myogenic precursor cells to progress through their normal developmental program and not because of a defect in migration of muscle progenitor cells into these regions. We also found that myogenic precursor cells for back, intercostal, and abdominal wall musculature in Myf-5-/-embryos failed to undergo normal translocation or differentiation. By contrast, the myogenic precursors of intercostal and abdominal wall musculature in MyoD-/-embryos underwent normal translocation but failed to undergo timely differentiation. In conclusion, these observations strongly support the hypothesis that Myf-5 plays a unique role in the development of muscles arising after translocation of epithelial dermamyotome cells along the medial edge of the somite to the subjacent myotome (e.g., back or epaxial muscle) and that MyoD plays a unique role in the development of muscles arising from migratory precursor cells (e.g., limb and branchial arch muscles, tongue, and diaphragm). In addition, the expression pattern of MyoD-lacZ transgenes in the intercostal and abdominal wall muscles of Myf-5-/-and MyoD-/-embryos suggests that appropriate development of these muscles is dependent on both genes and, therefore, these muscles have a dual embryonic origin (epaxial and hypaxial).Key words: epaxial and hypaxial muscle, Myf-5, MyoD, mouse development, somite.
TheCdx-1andCdx-2homeobox genes in the intestine
Authors: Freund Jean-Noël , Domon-Dell Claire , Kedinger Michèle , Duluc Isabelle
Published: April 2011

The past years have witnessed an increasing number of reports relative to homeobox genes in endoderm-derived tissues. In this review, we focus on the caudal-related Cdx-1 and Cdx-2 homeobox genes to give an overview of the in vivo, in vitro, and ex vivo approaches that emphasize their primary role in intestinal development and in the control of intestinal cell proliferation, differentiation, and identity. The participation of these genes in colon tumorigenesis and their identification as important actors of the oncogenic process are also discussed.Key words: caudal, epithelial cell proliferation and differentiation, cancer.
Effects of cyclosporin A on contractile activity and cytoskeleton in chick embryo cardiomyocytes
Authors: Kolcz Jacek , Drukala Justyna , Jurkiewicz Anna , Pfitzner Roman , Garlicki Miroslaw , Czyz Jaroslaw , Korohoda Wlodzimierz
Published: April 2011

The effects of cyclosporin A (CsA), a clinically used immunosupressive drug, on contractile activity of chick cardiomyocytes grown as small aggregates or explants suspended on a network of elastic glass fibres or cultured in a monolayer were analysed in vitro with computer-aided image cytometry methods. At therapeutic concentrations (200-1500 ng/mL), CsA induced changes in the frequency and amplitude of the beating activity of cardiomyocytes 15 min after application. Longer treatment of cardiomyocytes, for 20-24 h, additionally induced changes in their shape and cytoskeleton organization (F-actin and alpha-actinin distribution). These results indicate that CsA is able to affect directly the contractile activity, morphology, and cytoskeleton architecture of heart cells.Key words: heart, cardiomyocytes, contractibility, cyclosporin A, cytoskeleton, image analysis.
Growth factor synergism and antagonism in early neural crest development
Authors: Sieber-Blum Maya
Published: April 2011

This review article focuses on data that reveal the importance of synergistic and antagonistic effects in growth factor action during the early phases of neural crest development. Growth factors act in concert in different cell lineages and in several aspects of neural crest cell development, including survival, proliferation, and differentiation. Stem cell factor (SCF) is a survival factor for the neural crest stem cell. Its action is neutralized by neurotrophins, such as nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) through apoptotic cell death. In contrast, SCF alone does not support the survival of melanogenic cells (pigment cell precursors). They require the additional presence of a neurotrophin (NGF, BDNF, or NT-3). Fibroblast growth factor-2 (FGF-2) is an important promoter of proliferation in neuronal progenitor cells. In neural crest cells, fibroblast growth factor treatment alone does not lead to cell expansion but also requires the presence of a neurotrophin. The proliferative stimulus of the fibroblast growth factor - neurotrophin combination is antagonized by transforming growth factor beta-1 (TGFbeta-1). Moreover, TGFbeta-1 promotes the concomitant expression of neuronal markers from two cell lineages, sympathetic neurons and primary sensory neurons, indicating that it acts on a pluripotent neuronal progenitor cell. Moreover, the combination of FGF-2 and NT3, but not other neurotrophins, promotes expression or activation of one of the earliest markers expressed by presumptive sympathetic neuroblasts, the norepinephrine transporter. Taken together, these data emphasize the importance of the concerted action of growth factors in neural crest development at different levels and in several cell lineages. The underlying mechanisms involve growth-factor-induced dependence of the cells on other factors and susceptibility to growth-factor-mediated apoptosis.Key words: neural crest, melanocyte, stem cell factor, neurotrophin-3, transforming growth factor-beta1, apoptosis, norepinephrine transporter.
Expression of β1 integrins in glomerular tissue of Streptozotocin-induced diabetic rats
Authors: Regoli Mari , Bendayan Moïse
Published: April 2011

Based upon the importance of integrins as receptors for extracellular matrix components as well as transducers of extracellular signals, and since major alterations take place in the renal extracellular matrix during diabetes, it is important to study the role played by integrins in the development of the diabetic glomerulosclerosis. Expression of the β1subunit by renal glomerular cells was evaluated by biochemical and morphological means in short- and long-term diabetic rats. Western blots of isolated rat renal glomeruli demonstrated that the expression of β1increases along with age as well as with the hyperglycaemic state. These changes were significant as early as 6 weeks of hyperglycaemia. This was further demonstrated by immunocytochemistry, which revealed the presence of the β1subunit at the level of the plasma membranes of endothelial, epithelial, and mesangial cells. Quantitation of the immunolabelings confirmed the increased expression of β1under diabetic conditions. Further to this, expression of the focal adhesion kinase (FAK) was evaluated by immunoblotting showing little increase in diabetic conditions. On the other hand, testing the tyrosine phosphorylation of FAK, revealed significant increases in diabetes. To recover the fraction of FAK associated with the β1subunit, immunoprecipitation of isolated glomeruli homogenates was carried out with the anti- β1antibody. This demonstrated that the amounts of FAK co-precipitated with β1, as well as its tyrosine-phosphorylation, are in fact reduced in diabetic conditions. Since the changes reported were observed at time points prior to any morphological alteration of the renal extracellular matrix, it appears that modifications in integrins and in their intracellular relays constitute early events that precede the onset of the diabetic nephropathy and must then be associated with the hyperglycaemic condition.Key words: integrins, focal adhesion kinase, tyrosine phosphorylation, renal tissue, diabetes.
Stabilities of uncomplemented and complemented M15 β-galactosidase (Escherichiacoli) and the relationship to α-complementation
Authors: Gallagher Clare N , Huber Reuben E
Published: April 2011

M15 β-galactosidase (Escherichia coli) is a mutant form of β-galactosidase having residues 11-41 deleted. It is an inactive dimer but can be complemented to the active tetrameric form by the addition of a peptide containing the deleted residues. The activities of uncomplemented and complemented M15 β-galactosidases decreased starting at 42°C-uncomplemented over a narrow temperature range, complemented over a broad range. This is because uncomplemented protein is a simple dimer while complemented is a mix of interacting oligomers at high temperatures. The effects of added components on stability and α-complementation are best explained by binding effects on equilibria between native forms and forms susceptible to inactivation. Mg2+ stabilized complemented protein but destabilized uncomplemented protein (10× less Mg2+ was needed for complemented protein). α-Complementation increased somewhat at low Mg2+ but decreased at high Mg2+. These effects can be explained by differential Mg2+ binding to the native and susceptible forms. The enhancement of both stability and α-complementation by Na+ can be explained by preferential binding of Na+ to the native forms of both the uncomplemented and complemented proteins. Low 2-mercaptoethanol concentrations stabilized uncomplemented M15 β-galactosidase, but high concentrations destabilized it. All concentrations destabilized complemented M15 β-galactosidase. α-Complementation was enhanced by 2-mercaptoethanol. Thus, there is a correlation between stability of the uncomplemented protein and α-complementation at low 2-mercaptoethanol owing to interactions with native forms. The lack of correlation at higher 2-mercaptoethanol probably results from precipitation by 2-mercaptoethanol. In contrast to irreversible thermal inactivation, differences in reversible stability in urea were small. This suggests that quaternary structure and Mg2+ and Na+ sites are lost at low urea concentrations and are unimportant at the urea concentrations that result in reversible denaturation. Key words: β-galactosidase, α-complementation, stability.
A 40-kDa NF1-like protein, not YY1, binds to the rat p53 promoter for transactivation in various rat organs
Authors: Lee Minhyung , Song Haisun , Yu Sunhee , Lee Kyunghee , Park Jong-sang
Published: April 2011

Two recognition motifs of a 40-kDa NF1-like protein were previously identified in the rat p53 promoter. One is located between -296 and -312 (NF1-like element 1) and the other between -195 and -219 (NF1-like element 2). The latter one was also identified as a NF1/YY1 recognition motif in the human p53 promoter. NF1 or YY1 binds to the motif and regulates the expression of the human p53 gene in a tissue-specific manner. In this study, we investigated the binding protein for NF1-like element 2 in various rat tissues. Unlike the human p53 transcription, an NF1-like protein, not YY1, bound to the motif in every tested tissue: thymus, kidney, and spleen. In vitro transcription assay also confirmed that the NF1-like protein regulated the p53 transcription in rat spleen, although the human p53 transcription was regulated by YY1 in that organ. The molecular mass of the binding protein was determined to be 40 kDa, which was the same as that of the NF1-like protein identified in liver. Therefore, the 40-kDa NF1-like protein may be a universal transcription regulator for the rat p53 gene.Key words: NF1-like protein, p53, promoter, transcription regulation, YY1.
Biology of the fragile X mental retardation protein, an RNA-binding protein
Authors: Khandjian Edouard W
Published: April 2011

The fragile X syndrome, an X-linked disease, is the most frequent cause of inherited mental retardation. The syndrome results from the absence of expression of the FMR1 gene (fragile mental retardation 1) owing to the expansion of a CGG trinucleotide repeat located in the 5prime untranslated region of the gene and the subsequent methylation of its CpG island. The FMR1 gene product (FMRP) is a cytoplasmic protein that contains two KH domains and one RGG box, characteristics of RNA-binding proteins. FMRP is associated with mRNP complexes containing poly(A)+mRNA within actively translating polyribosomes and contains nuclear localization and export signals making it a putative transporter (chaperone) of mRNA from the nucleus to the cytoplasm. FMRP is the archetype of a novel family of cytoplasmic RNA-binding proteins that includes FXR1P and FXR2P. Both of these proteins are very similar in overall structure to FMRP and are also associated with cytoplasmic mRNPs. Members of the FMR family are widely expressed in mouse and human tissues, albeit at various levels, and seem to play a subtle choreography of expression. FMRP is most abundant in neurons and is absent in muscle. FXR1P is strongly expressed in muscle and low levels are detected in neurons. The complex expression patterns of the FMR1 gene family in different cells and tissues suggest that independent, however similar, functions for each of the three FMR-related proteins might be expected in the selection and metabolism of tissue-specific classes of mRNA. The molecular mechanisms altered in cells lacking FMRP still remain to be elucidated as well as the putative role(s) of FXR1P and FXR2P as compensatory molecules.Key words: RNA-binding proteins, polyribosomes, messenger ribonucleoprotein, messenger ribonucleoparticles, nucleocytoplasmic trafficking, mental retardation.
Assessing the function of the Ro ribonucleoprotein complex usingCaenorhabditis elegansas a biological tool
Authors: Labbé Jean-Claude , Hekimi Siegfried , Rokeach Luis A
Published: April 2011

The Ro ribonucleoprotein complex (Ro RNP) was initially described as an autoimmune target in human diseases such as systemic lupus erythematosus and Sjögren's syndrome. In Xenopus and human cells, its general structure is composed of one major protein of 60 kDa, Ro60, that binds to one of four small RNA molecules, designated Y RNAs. Although no function has been assigned to the Ro RNP, Ro60 has been shown to bind mutant 5S ribosomal RNA (rRNA) molecules in Xenopus oocytes, suggesting a role for Ro60 in 5S rRNA biogenesis. Ro60 has also been shown to participate in the regulation of the translational fate of the L4 ribosomal protein mRNA by interacting with the 5prime untranslated region, again suggesting its possible implication in ribosome biogenesis. To identify the function of Ro RNP, we have taken a genetic approach in the nematode Caenorhabditis elegans. As such, we characterized the gene encoding the protein ROP-1, the homologue of the human Ro60 protein. Here, we review the phenotypic analysis of C. elegans rop-1(-) mutants and integrate these results into a model for the function of the Ro RNP particle.Key words: Caenorhabditis elegans, Ro ribonucleoprotein complex, ROP-1, small RNAs, quality control.
An allele of the yeast RPB7 gene, encoding an essential subunit of RNA polymerase II, reduces cellular resistance to the antitumor drug bleomycin
Authors: He Chuan Hua , Ramotar Dindial
Published: April 2011

Bleomycin is an antitumor drug that kills cells by introducing lesions in DNA. Thus, normal cells exposed to bleomycin must rely on efficient DNA repair mechanisms to survive. In the yeast Saccharomyces cerevisiae, the transcriptional activator Imp2 is required to fend off the toxic effects of bleomycin. However, it remains unclear whether Imp2 controls the expression of a protein that either repairs bleomycin-induced DNA lesions, or detoxifies the drug, and or both. To gain further insight into the mechanisms by which yeast cells mount a response towards bleomycin, we began to sequentially characterize the genetic defect in a collection of bleomycin-sensitive mutants that were previously isolated by mini-Tn3 transposon mutagenesis. A rescue plasmid designed to integrate at the site of the mini-Tn3 insertion was used to identify the defective gene in one of the mutant strains, HCY53, which was not allelic to IMP2. We showed that in strain HCY53, the mini-Tn3 was inserted at the distal end of an essential gene RPB7, which encodes one of the two subunits, Rpb4-Rbp7, that forms a subcomplex with RNA polymerase II. Since rpb7 null mutants are nonviable, it would appear that the rpb7::mini-Tn3 allele produces a protein that retains partial biological function thus permitting cell viability, but which is unable to provide bleomycin resistance to strain HCY53. The defective phenotype of strain HCY53 could be corrected by a plasmid bearing the entire RPB7 gene. Two dimensional gel analysis revealed that the expression of several proteins were diminished or absent in the rpb7::mini-Tn3 mutant when challenged with bleomycin. These results are in accord with our previous report that bleomycin resistance in yeast is controlled at the transcriptional level.Key words: yeast, oxidants, bleomycin, transcription, DNA damage.
Molecular cloning and expression of rat antisecretory factor and its intracellular localization
Authors: Tateishi Kayoko , Misumi Yoshio , Ikehara Yukio , Miyasaka Kyoko , Funakoshi Akihiro
Published: April 2011

Antisecretory factor (AF) was identified as a pituitary protein that inhibits the intestinal fluid secretion induced by cholera toxin. One aim of this study was to elucidate whether AF is also synthesized in the intestine or if AF produced in the pituitary is transported to the intestinal tract for its function there. cDNA clones encoding a protein proposed to be AF were isolated from rat pituitary gland and intestinal mucosa cDNA libraries. The nucleotide sequences of clones isolated from the rat pituitary gland and intestinal mucosa were identical. The deduced amino acid sequence was highly homologous to the sequence for subunit 5a of the human 26S protease that exists abundantly in the cytosol and nucleus. The production of AF in the intestine was confirmed by Northern blot and immunoblot analyses. Immunocytochemical observations of cells transfected with the rat AF cDNA showed that the AF protein was localized in the cytoplasm. These findings suggest that the protein proposed to be AF may be a cytoplasmic protein, it exists in the intestine rather than being transported from the pituitary gland, and it may function in intestinal cells.Key words: rat antisecretory factor, 26S protease, S5a, cytoplasmic protein.
Analysis of transcription factors binding to the human 7SL RNA gene promoter
Authors: Müller Jürgen , Benecke Bernd-Joachim
Published: April 2011

Transcription of the human 7SL RNA gene by RNA polymerase III depends on the concerted action of transcription factors binding to the gene-internal and gene-external parts of its promoter. Here, we investigated which transcription factors interact with the human 7SL RNA gene promoter and which are required for transcription of the human 7SL RNA gene. A-box/B-box elements were previously identified in 5S RNA, tRNA, and virus associated RNA genes and are recognized by transcription factor IIIC (TFIIIC). The gene-internal promoter region of the human 7SL RNA gene shows only limited similarity to those elements. Nevertheless, competition experiments and the use of highly enriched factor preparations demonstrate that TFIIIC is required for human 7SL transcription. The gene-external part of the promoter includes an authentic cAMP-responsive element previously identified in various RNA polymerase II promoters. Here we demonstrate that members of the activating transcription factor/cyclic AMP-responsive element binding protein (ATF/CREB) transcription factor family bind specifically to this element in vitro. However, the human 7SL RNA gene is not regulated by cAMP in vivo. Furthermore, in vitro transcription of the gene does not depend on ATF/CREB transcription factors. It rather appears that a transcription factor with DNA-binding characteristics like ATF/CREB proteins but otherwise different properties is required for human 7SL RNA transcription.Key words: 7SL RNA, ATF, CRE, TFIIIC, RNA polymerase III.
Differential transmission of G1 cell cycle arrest and mating signals bySaccharomyces cerevisiaeSte5 mutants in the pheromone pathway
Authors: Choi You-Jeong , Kim Sun-Hong , Park Ki-Sook , Choi Kang-Yell
Published: April 2011

Saccharomyces cerevisiae Ste5 is a scaffold protein that recruits many pheromone signaling molecules to sequester the pheromone pathway from other homologous mitogen-activated protein kinase pathways. G1 cell cycle arrest and mating are two different physiological consequences of pheromone signal transduction and Ste5 is required for both processes. However, the roles of Ste5 in G1 arrest and mating are not fully understood. To understand the roles of Ste5 better, we isolated 150 G1 cell cycle arrest defective STE5 mutants by chemical mutagenesis of the gene. Here, we found that two G1 cell cycle arrest defective STE5 mutants (ste5MD248Vand ste5delta-776) retained mating capacity. When overproduced in a wild-type strain, several ste5 mutants also showed different dominant phenotypes for G1 arrest and mating. Isolation and characterization of the mutants suggested separable roles of Ste5 in G1 arrest and mating of S. cerevisiae. In addition, the roles of Asp-248 and Tyr-421, which are important for pheromone signal transduction were further characterized by site-directed mutagenesis studies.Key words: Ste5, Saccharomyces cerevisiae, signal transduction, mating, G1 cell cycle arrest.
Structure, modelling, and molecular dynamics studies of the inhibition of protein tyrosine phosphatase 1B by sulfotyrosine peptides
Authors: Glover Nicholas R , Tracey Alan S
Published: April 2011

The protein tyrosine phosphatases comprise a class of enzymes that are crucial for the regulation of a number of cellular processes. Because of this, they are attracting increasing attention, not only as legitimate therapeutic targets, but also because of their relationship to many fundamental cellular processes. Certain sulfotyrosine peptides derived from casein are known to be good inhibitors of the protein tyrosine phosphatase, PTP1B. In this study, NMR transfer nuclear Overhauser effect studies have been used to ascertain the bound-state conformation adopted by the 12-amino acid residue casein-derived peptide, CAS200 (NANEEE(sY)SIGSA) and N-terminal truncated forms of this peptide, CAS203 and CAS205. Each of the peptides were found to bind in an extended beta-strand conformation. Extensive molecular modelling and molecular dynamics simulations of the PTP1B/peptide complexes, in a fully hydrated model, allowed a detailed description of the potential sources of the binding interactions to be developed. In agreement with the NMR studies, the modelling provided a picture of binding of CAS200 in which only the central (E203- I208) residues contributed significantly to the binding while the 3 N-terminal and 3 C-terminal residues were quite fluxional. Critical cationic surface residues, lying near to, but outside the active site pocket were the source of strong stabilizing forces that complemented the stabilizing interactions of the active site pocket. Electrostatic, hydrophobic, and hydrogen bonding interactions, in a residue specific manner, were all found to make significant contributions to the binding of these inhibitors.Key words: protein tyrosine phosphatase, PTP1B, casein peptide, inhibitor, NMR structure, molecular modelling, molecular dynamics.
Roles of protein tyrosine phosphatases in cell migration and adhesion
Authors: Angers-Loustau Alexandre , Côté Jean-François , Tremblay Michel L
Published: April 2011

Signal transduction pathways are often seen as cascades of kinases, whereas phosphatases are relinquished to the housekeeping function of resetting the individual elements to a resting state. However, critical biological processes such as cellular migration require a coordinated and constant remodeling of the actin cytoskeleton as well as a rapid turnover of the cell-substratum linkages that necessitate the concomitant action of antagonistic enzymes. Tyrosine phosphorylation was long known to be involved in adhesion and de-adhesion mediated via the integrin receptors. As the roles of tyrosine kinases such as focal adhesion kinase, c-Src, and Csk in this pathway are being extensively studied, increasing evidence is emerging about the importance of protein tyrosine phosphatases (PTP). In this review we discuss examples of PTPs that were recently shown to play a role in cell adhesion and migration and their mechanism of action.Key words: protein tyrosine phosphatases (PTP), migration, adhesion, FAK, p130Cas, Src.
Long chain arginine esters: A new class of cationic detergents for preparation of hydrophobic ion-paired complexes
Authors: Claffey David J , Meyer Jeffrey D , Beauvais Robert , Brandt Tessa , Shefter Eli , Kroll David J , Ruth James A , Manning Mark C
Published: April 2011

The ability of stoichiometric amounts (based on charged groups) of ionic detergents to bind to oppositely charged ionic compounds has been recently reviewed. These hydrophobic ion-paired (HIP) complexes display altered solubility properties. Most of the work to date on HIP compelxes has focused on basic drugs and anionic detergents. It would be extremely useful to extend this approach to acidic compounds, including DNA and RNA. However, most cationic detergents are relatively toxic. It is hypothesized that detergents constructed from naturally occurring or well tolerated components, coupled by labile linkages, will be less toxic and still able to form strong HIP complexes. This study describes the synthesis and characterization of long chain alkyl esters of arginine. This class of cationic detergents, which have not been reported previously, are less cytotoxic than alkyltrimethylammonium detergents, possibly making them more acceptable in drug delivery applications. These arginine esters exhibit detergent-like properties. For example, the dodecyl ester of arginine has a critical micelle concentration of 0.07 mM, while being approximately 5-10 fold less toxic than tetradecyltrimethylammonium bromide. The arginine dodecyl ester forms stable HIP complexes with plasmid DNA. The complex is sufficiently stable to allow some modest level of transfection with Cos-7 cells in a time- and concentration-dependent fashion. This work demonstrates that arginine-based cationic detergents are effective ion-pairing agents, appear to be less toxic than alkyltrimethylammonium compounds, and form stable complexes with DNA.
Association of DNAse sensitive chromatin domains with the nuclear periphery in 3T3 cells in vitro
Authors: Chan Jonathan KL , Park Paul C , Boni Umberto De
Published: April 2011

DNAse sensitive chromatin, putative transcriptionally competent sequences, exists either as pan-nuclear speckles in cells with nuclei which exhibit a flat geometry, or as a shell apposed to the nuclear envelope in cells with spheroidal nuclei. To test the hypothesis that DNAse sensitive chromatin is similarly associated with the nuclear periphery in cell types with a very flat geometry such as 3T3 fibroblasts, cells were subjected to hypotonic expansion to change their nuclei from a flat ellipsoid to a spheriod. This was based on the assumption that such a spatial association is not resolvable due to the interdigitation at the nuclear midplane of DNAse sensitive chromatin associated with the upper and lower nuclear surfaces. In situ nick translation was used to visualize the distribution of DNAse sensitive chromatin as a function of nuclear geometry. Both unexpanded and expanded cells exhibit DNAse sensitive chromatin as a dome at the apical side of the nucleus, i.e., that aspect of the cell facing the culture medium. The results argue for a polarized association of DNAse sensitive chromatin with the nuclear envelope and indicate that the nuclear periphery may function as a compartment for the spatial coupling of transcription and nucleo-cytoplasmic transport.

Key words: nuclear organization, DNAse sensitive chromatin, hypotonic expansion, 3T3 cells.
γ-RAYS PRODUCED BY SLOW NEUTRON CAPTURE IN BERYLLIUM, CARBON, AND NITROGEN
Authors: Kinsey B. B. , Bartholomew G. A. , Walker W. H.
Published: April 2011

The γ-rays produced by slow neutron capture in beryllium, carbon, and nitrogen have been investigated with a pair spectrometer. Only one γ-ray was observed to follow capture in beryllium and in carbon; nine were observed from nitrogen. The neutron binding energies computed from the energies of these radiations are: Be10, 6.797 ± 0.008 Mev.; C13, 4.948 ± 0.008 Mev.; N15, 10.823 ± 0.012 Mev. The nitrogen γ-rays can be fitted into a term scheme containing the previously known excited states of N15, obtained from the study of (d, p) reactions, together with one excited state at 9.16 Mev., hitherto unreported. A comparison of the intensities of the nitrogen and beryllium radiations shows that the radiative capture cross section of nitrogen is at most 160 millibarns.
THEORY OF MULTIPOLE RADIATIONS
Authors: Wallace P. R.
Published: April 2011

We develop a systematic analysis of the radiation from a given oscillating system of charges and currents, without any approximations. Using a simple vector identity, the vector potential is separated into irrotational and solenoidal parts. The field may be expressed in terms of the latter alone. A similar vector identity involving the operator L = r × grad (the rotation operator) permits the separation of the field into parts in which the radial components of the electric and magnetic field, respectively, vanish. The energy flux, energy density, and angular momentum density may in each case be expressed in terms of the angular operators L, L2. Expansion in the eigenfunctions of these operators, the spherical harmonics, corresponds to the separation into electric and magnetic multipoles of all orders. Introduction of "tensor spherical harmonics" enables us to exhibit these radiations in terms of natural multipoles (derivatives of 1/r). All calculations are carried out without restriction as to size of radiating system relative to wave length, in the induction as well as the radiation region.
ELECTROMAGNETIC ENERGY DENSITY AND FLUX
Authors: Hines C. O.
Published: April 2011

Although Poynting's theorem receives general acceptance in the treatment of electromagnetic energy, an alternative theorem, Macdonald's, has equal claim to validity at the present state of our knowledge. In a comparison of many results derived from the two, Macdonald's theorem exhibits sufficient superiority to warrant its consideration more generally in electromagnetics.
CLAUSIUS-MOSOTTI EQUATION FOR CERTAIN TYPES OF ANISOTROPIC CRYSTALS
Authors: Neugebauer H. E. J.
Published: April 2011

The Clausius-Mosotti equation is derived for crystals whose particles are anisotropic and arranged in any lattice provided that all the particles are of the same type and provided that the principal axes of their tensors of polarizability are parallel to each other. The formulas are of special interest for artificial dielectrics used as lens material for microwave frequencies. They explain experimental results.
ON THE NUSSELT MODULUS AS A FUNCTION OF FRICTION FACTOR, REYNOLDS AND PRANDTL MODULI, FOR HEAT TRANSFER TO A FLUID FLOWING TURBULENTLY THROUGH A TUBE OF CIRCULAR SECTION
Authors: Marris A. W.
Published: April 2011

Theoretical expressions for the Nusselt modulus and radial temperature distribution in terms of Reynolds number, Prandtl number, the ratio k of the eddy diffusivities for heat and momentum, and the friction factor are developed for the case of heat transfer from a tube of circular section to a fluid flowing turbulently through it. The results, appropriate to fluids with Prandtl numbers greater than 1/2k, are derived on the assumption of the constancy of fluid properties and require a linear longitudinal temperature gradient in the tube itself. They enable the effect of the insulating "laminar" and "buffer" layers adjacent to the tube wall to be demonstrated at various Prandtl numbers and are appropriate for correlation with experiment for the investigation of the constancy or otherwise of the ratio of the eddy diffusivities for heat and momentum implicit in the momentum transfer analogy.A similar result is worked out on the vorticity transfer analogy for the particular case of Prandtl number equal to 1/k′ and is found to be invalid for such a configuration. Here k′ is the ratio of the eddy diffusivities for heat and vorticity.
AN IONIZATION MANOMETER AND CONTROL UNIT FOR EXTREMELY LOW PRESSURES
Authors: Redhead P. A. , McNarry L. R.
Published: April 2011

A Bayard-Alpert type ionization manometer for the measurement of pressures as low as 10−10 mm. of mereury is described, and methods for increasing the sensitivity are discussed. The control unit is direct reading in pressure to 10−10 mm. and has provision for degassing the electrodes.
HIGH RESOLUTION RAMAN SPECTROSCOPY OF GASES: I. EXPERIMENTAL METHODS
Authors: Stoicheff B. P.
Published: April 2011

An apparatus for obtaining intense Raman spectra of gases excited by the Hg 4358 line is described. It consists of a mirror-type Raman tube irradiated by two high-current mercury lamps, completely enclosed in a reflector of magnesium oxide. The lamps are externally water-cooled along their entire length and emit sharp lines of high intensity.Rotational Raman spectra of gases at a pressure of 1 atm. have been photographed in the second order of a 21 ft. grating in exposure times of 6 to 24 hr. The Raman lines are sharp and a resolving power of about 100,000 has been achieved. It will be possible to resolve the rotational Raman spectra, and hence to evaluate the rotational constants of molecules having moments of inertia of up to 300 × 10−10 gm. cm.2 Such investigations will be especially useful for non-polar molecules.
AN INVESTIGATION OF THE NUCLEAR RESONANCE ABSORPTION SPECTRUM OF Al27 IN A SINGLE CRYSTAL OF EUCLASE
Authors: Eades R. G.
Published: April 2011

The nuclear magnetic resonance spectrum of Al27 in a single crystal of HBeAlSiO5 (euclase) in an external magnetic field of 7000 gauss is described. The Al27 nuclei are found to occupy two kinds of lattice sites which differ from each other only in the orientation of the principal axes of the electric field gradient tensors whose eigenvalues are all distinct, but identical at both sites. The absolute value of the quadrupole coupling constant for both groups of Al27 nuclei is found to be 5173 ± 10 kc./sec. and the axial asymmetry parameter of the field gradient tensors at both the lattice positions is 0.698 ± 0.009. The two sets of principal axes are reflections of each other in the (010) plane which is consistent with the symmetry of the proposed crystal structure. The theoretical dependence of the spectrum line frequencies on the applied magnetic field is given for one group of Al27 nuclei and for one orientation of the crystal in fields up to 2000 gauss; the feasibility of checking this experimentally is discussed.
LONG DISTANCE V.H.F. FIELDS: III. THE CASE OF TWO ELEVATED LAYERS
Authors: Northover Francis H.
Published: April 2011

The general theory developed in Part I and in the beginning of Part II is applied to derive an equation for the eigenvalues of the propagation for the case of two sharp elevated layers. This equation is very briefly discussed and some special cases noted.
A METHOD OF EXAMINING STRUCTURAL CHANGES OF METALS ON DEFORMATION IN LIQUID HELIUM: EXAMINATION OF INDIUM
Authors: Pearson W. B.
Published: April 2011

A Debye–Scherrer type of X-ray camera is described in which a soft metal can be deformed by extension and photographed in situ in liquid helium. Using this camera we have examined deformed indium at 4.2°K. and find no evidence of a lattice transformation when a tensile strain of ~ 15% is applied. The investigation was undertaken to examine the suggestion of Swenson, stemming from the observation of anomalies in the mechanical properties of indium at low temperatures, that a very slight deformation of indium at 4.2°K. might transform the face-centered tetragonal to a close-packed structure.
INTERNATIONAL COMPARISONS OF THE CANADIAN PRIMARY RADIUM STANDARD
Authors: Michel W. S. , Whyte G. N.
Published: April 2011

The content in milligrams of radium element of the Canadian primary radium standard was measured relative to the certified weight of a primary standard of the United States by an ionization method. The problem of correcting for differences in the attenuation of the gamma radiation in the body of each source is important, since the standards differ greatly in shape; a method of making this correction is described. Other intercomparisons involving the Canadian standard are discussed, and a mean value for the content of the standard is derived from these comparisons. The agreement between this and the certified value is satisfactory.
ENCLOSED QUANTUM MECHANICAL SYSTEMS
Authors: Hull T. E. , Julius R. S.
Published: April 2011

A brief description is given of the eigenvalue problems associated with enclosed quantum mechanical systems and of some attempts to deal with these problems. Another method is developed which leads to a general asymptotic formula for the eigenvalues. This formula yields a simple asymptotic approximation to the eigenvalue in each particular case, once the eigenfunction of the corresponding unrestricted system is known.
STANDARD DEVIATION OF DEAD TIME CORRECTION IN COUNTERS
Authors: Campbell L. Lorne
Published: April 2011

Because of the finite recovery time of counters a correction must be applied to the number of registrations which the counter makes so that a better approximation to the true rate at which events occur may be obtained. It is shown here that, for random events, the standard deviation of the corrected rate is approximately [Formula: see text], where v is the mean rate at which events occur, T is the recovery time of the counter, and t is the duration of the observation. This value of the standard deviation is an asymptotic value which holds for large values of t. As an intermediate result, an asymptotic expression is obtained for the value of the mth moment of the number of registrations in time t. The method used here could also be applied to determine asymptotic expressions for the expected values of other functions of the number of registrations.