bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis and sorting of live cells according to secreted molecules, relocated to a cell-surface affinity matrix.
Authors: Manz R , Assenmacher M , Pflüger E , Miltenyi S , Radbruch A
Published: May 2006

We have developed a technology for analysis and sorting of live cells according to secreted molecules. An artificial affinity matrix, specific for the secreted product of interest, is created on the cell surface, and the cells are allowed to secrete for a defined time period. The secreted molecules bind to the affinity matrix on the secreting cell and are subsequently labeled with specific fluorescent or magnetic staining reagents for cytometric analysis and cell sorting. Crossfeeding of the secreted products to other cells is prevented by decreasing the permeability of the incubation medium. This approach will have a wide range of applications in biotechnology and biomedical research. Here, we describe analysis and sorting of hybridoma cells, according to secreted antibodies, and of activated T lymphocytes, according to secreted cytokines.
The N terminus of phosducin is involved in binding of beta gamma subunits of G protein.
Authors: Xu J , Wu D , Slepak V Z , Simon M I
Published: May 2006

Phosducin is a soluble phosphoprotein found in retinal photoreceptor cells and in the pineal gland. It binds to the beta gamma subunits of guanine nucleotide-binding proteins (G proteins) (G beta gamma) and may regulate G-protein function. In this study, the ability of specific regions of phosducin to bind G beta gamma was characterized. A series of deletion mutants were made in bovine phosducin. They were tested in cotransfection assays for their ability to inhibit G beta gamma-mediated phospholipase C beta 2 isoform activation. Overexpression of the N-terminal half of phosducin showed inhibition, whereas overexpression of the C-terminal half did not. The first 63 amino acid residues were required for inhibition. A tryptophan-to-valine substitution at residue 29, which is part of a well conserved 11-amino acid sequence, severely impaired phosducin inhibitory function. Glutathione S-transferase-phosducin fusion proteins were expressed in Escherichia coli to study phosducin-G beta gamma interaction in vitro. The N-terminal 63-amino acid fragment was able to bind to G beta gamma. In contrast, the C-terminal half failed to bind to G beta gamma. The substitution mutants showed little or no binding. Furthermore, direct measurements of interaction between G beta gamma and fragments of phosducin, using surface plasmon resonance technology, confirmed the assignment of binding activity to the 63-amino acid fragment and the importance of the tryptophan residue.
The origin recognition complex interacts with a bipartite DNA binding site within yeast replicators.
Authors: Rao H , Stillman B
Published: May 2006

Replicators are genetically defined elements within chromosomes that determine the location of origins of DNA replication. In the yeast Saccharomyces cerevisiae, the ARS1 replicator contains multiple functional DNA elements: an essential A element and three important B elements--B1, B2, and B3. Functionally similar A, B1, and B2 elements are also present in the ARS307 replicator. The B3 element binds a replication and transcription enhancer protein Abf1p, whereas the A element is required for binding the origin recognition complex (ORC). The function of the B1 and B2 elements remains to be defined. We have used a gel-based DNA binding assay to study the interaction between replicators and the putative initiator protein ORC. In addition to the established requirements for ATP and the A element for ORC-DNA interaction, the new data demonstrate that sequences in the B1 element are also important for ORC-DNA association. This conclusion is supported by DNase I footprint analyses and demonstrates that ORC binds to a bipartitite recognition element within the DNA. Furthermore, mutation of nucleotides in the B1 element suggests that this element has other functions in the initiation of DNA replication besides participating in the ORC-DNA interaction.
Xanthophyll cycle-dependent quenching of photosystem II chlorophyll a fluorescence: formation of a quenching complex with a short fluorescence lifetime.
Authors: Gilmore A M , Hazlett T L , Govindjee
Published: May 2006

Excess light triggers protective nonradiative dissipation of excitation energy in photosystem II through the formation of a trans-thylakoid pH gradient that in turn stimulates formation of zeaxanthin and antheraxanthin. These xanthophylls when combined with protonation of antenna pigment-protein complexes may increase nonradiative dissipation and, thus, quench chlorophyll a fluorescence. Here we measured, in parallel, the chlorophyll a fluorescence lifetime and intensity to understand the mechanism of this process. Increasing the xanthophyll concentration in the presence of a pH gradient (quenched conditions) decreases the fractional intensity of a fluorescence lifetime component centered at approximately 2 ns and increases a component at approximately 0.4 ns. Uncoupling the pH gradient (unquenched conditions) eliminates the 0.4-ns component. Changes in the xanthophyll concentration do not significantly affect the fluorescence lifetimes in either the quenched or unquenched sample conditions. However, there are differences in fluorescence lifetimes between the quenched and unquenched states that are due to pH-related, but nonxanthophyll-related, processes. Quenching of the maximal fluorescence intensity correlates with both the xanthophyll concentration and the fractional intensity of the 0.4-ns component. The unchanged fluorescence lifetimes and the proportional quenching of the maximal and dark-level fluorescence intensities indicate that the xanthophylls act on antenna, not reaction center processes. Further, the fluorescence quenching is interpreted as the combined effect of the pH gradient and xanthophyll concentration, resulting in the formation of a quenching complex with a short (approximately 0.4 ns) fluorescence lifetime.
Bumblebee preference for symmetrical flowers.
Authors: Møller A P
Published: May 2006

Fluctuating asymmetry, which represents small random deviations from otherwise bilateral symmetry, is a measure of the phenotypic quality of individuals indicating the ability of controlled development under given environmental and genetic conditions. I tested whether floral symmetry reliably reflects phenotypic quality measured in terms of pollinator rewards and whether pollinators respond to floral symmetry in a series of observations and experiments on Epilobium angustifolium (Onagraceae). Lower petal asymmetry was negatively related to mean lower petal length, whereas asymmetry in leaf width was positively related to mean leaf width. Flowers visited by bumblebees were larger and more symmetrical than the nearest neighboring flower. This relationship between pollinator preference for large and symmetrical flowers was demonstrated to be causal in experiments in which the lower petals were manipulated symmetrically or asymmetrically. Nectar production was larger in symmetrical flowers, and this may explain the bumblebee preference for flower symmetry. Floral symmetry therefore reliably reflects nectar production and hence enhances pollen transport. Extensive embryo abortion has been documented in E. angustifolium and other outcrossing plant species. Floral fluctuating asymmetry, which reflects general developmental homeostasis, may explain such developmental selection in these plants.
Conserved nucleoprotein structure at the ends of vertebrate and invertebrate chromosomes.
Authors: Lejnine S , Makarov V L , Langmore J P
Published: May 2006

Eukaryotic chromosomes terminate with telomeres, nucleoprotein structures that are essential for chromosome stability. Vertebrate telomeres consist of terminal DNA tracts of sequence (TTAGGG)n, which in rat are predominantly organized into nucleosomes regularly spaced by 157 bp. To test the hypothesis that telomeres of other animals have nucleosomes, we compared telomeres from eight vertebrate tissues and cell cultures, as well as two tissues from an invertebrate. All telomeres have substantial tracts of (TTAGGG)n comprising 0.01-0.2% of the genome. All telomeres are long (20-100 kb), except for those of sea urchin, human, and some chicken chromosomes, which are 3-10 kb in length. All of the animal telomeres contained nucleosome arrays, consistent with the original hypothesis. The telomere repeat lengths vary from 151 to 205 bp, seemingly uncorrelated with telomere size, regularity of nucleosome spacing, species, or state of differentiation but surprisingly correlated with the repeat of bulk chromatin within the same cells. The telomere nucleosomes were consistently approximately 40 bp smaller than bulk nucleosomes. Thus, animal telomeres have highly conserved sequences and unusually short nucleosomes with cell-specific structure.
Rapid alteration of thalamocortical axon morphology follows peripheral damage in the neonatal rat.
Authors: Catalano S M , Robertson R T , Killackey H P
Published: May 2006

The effect of day of birth (postnatal day 0; P0) infraorbital nerve section on the morphology of individual thalamocortical axons in rat somatosensory cortex was examined on P3. Thalamic fibers were labeled in fixed brains with the carbocyanine dye 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate, and individual photo-converted thalamocortical fibers were reconstructed. In normal animals on P3, axon arbor terminal formation within layer IV has commenced and terminal arbor width is comparable to that of a cortical "barrel." After infraorbital nerve section, the average width of thalamocortical terminal arbors is significantly greater than is the average arbor width of normal rats of the same age; however, neither the number of branches per terminal arbor nor total arbor length differs between groups. These observations suggest that the role of the periphery in guiding terminal arbor formation is exerted both very rapidly and at the level of the single thalamic axon. Further, these results indicate a close association between individual axon terminal arbor morphology and pattern formation in the rat somatosensory cortex.
Ca(2+)-inhibitable adenylyl cyclase modulates pulmonary artery endothelial cell cAMP content and barrier function.
Authors: Stevens T , Nakahashi Y , Cornfield D N , McMurtry I F , Cooper D M , Rodman D M
Published: May 2006

Maintenance by the endothelium of a semi-permeable barrier is critically important in the exchange of oxygen and carbon dioxide in the lung. Intracellular free Ca2+ ([Ca2+]i) and cAMP are principal determinants of endothelial cell barrier function through their mutually opposing actions on endothelial retraction. However, details of the mechanisms of this antagonism are lacking. The recent discovery that certain adenylyl cyclases (EC 4.6.1.1) could be acutely inhibited by Ca2+ in the intracellular concentration range provided one possible mechanism whereby elevated [Ca2+]i could decrease cAMP content. This possibility was explored in pulmonary artery endothelial cells. The results indicate that a type VI Ca(2+)-inhibitable adenylyl cyclase exists in pulmonary artery endothelial cells and is modulated by physiological changes in [Ca2+]i. Furthermore, the results suggest the inverse relationship between [Ca2+]i and cAMP that is established by Ca(2+)-inhibitable adenylyl cyclase plays a critical role in modulating pulmonary artery endothelial cell permeability. These data provide evidence that susceptibility to inhibition of adenylyl cyclase by Ca2+ can be exploited in modulating a central physiological process.
gp130 and c-Kit signalings synergize for ex vivo expansion of human primitive hemopoietic progenitor cells.
Authors: Sui X , Tsuji K , Tanaka R , Tajima S , Muraoka K , Ebihara Y , Ikebuchi K , Yasukawa K , Taga T , Kishimoto T
Published: May 2006

gp130, a signal-transducing receptor component of interleukin 6 (IL-6), associates with an IL-6 and IL-6 receptor (IL-6) complex and transduces signals. To examine the role of gp130 signaling in the expansion of human hemopoietic progenitor cells, we tested the effects of a recombinant soluble human IL-6 receptor (sIL-6R) and/or IL-6 in combination with other cytokines on purified human umbilical cord blood CD34+ cells, using methylcellulose clonal assay and suspension culture in the presence or absence of serum. A combination of sIL-6R and IL-6 (sIL-6R/IL-6), but not sIL-6R or IL-6 alone, was found to dramatically stimulate expansion of hemopoietic progenitor cells as well as CD34+ cells in the presence of stem cell factor. Significant generation of multipotential hemopoietic progenitors over a period of 3 weeks in suspension culture and efficient formation of colonies, especially multilineage and blast cell colonies, in methylcellulose assay supplemented with a combination of sIL-6R/IL-6 together with stem cell factor were observed in serum-containing and serum-free culture. Addition of anti-gp130 monoclonal antibodies or anti-IL-6R monoclonal antibodies to the above cultures dose-dependently inhibited the expansion of progenitor cells in suspension culture and also completely blocked the formation of multilineage colonies in methylcellulose culture. These findings demonstrated that the significant expansion of human primitive hemopoietic progenitors could be achieved with the gp130 and c-Kit signalings initiated by the sIL-6R/IL-6 complex in the presence of stem cell factor and suggested the possible application of this method for ex vivo expansion of CD34+ cells for bone marrow transplantation.
The neural substrates underlying word generation: a bilingual functional-imaging study.
Authors: Klein D , Milner B , Zatorre R J , Meyer E , Evans A C
Published: May 2006

We used positron emission tomography to investigate word generation in subjects whose first language was English but who were also proficient in French. These subjects performed three types of lexical search: rhyme generation based on phonological cues, synonym generation requiring a semantic search, and translation involving access to a semantic representation in the other language. Two control tasks required word repetition in each language. We investigated whether phonological and semantic word-generation activate similar regions and whether the same neural substrates subserve the second language as subserve the first. A series of cerebral blood flow increases, corresponding to Brodmann's areas 47, 46, 45, and 8, were observed in the left frontal cortex when the baseline repetition task was subtracted from each of the respective generation tasks. The results suggest that common neural substrates are involved in within- and across-language searches and that the left inferior frontal region is activated irrespective of whether the search is guided by phonological or semantic cues.
Repression by SSN6-TUP1 is directed by MIG1, a repressor/activator protein.
Authors: Treitel M A , Carlson M
Published: May 2006

The SSN6-TUP1 protein complex represses transcription of diversely regulated genes in the yeast Saccharomyces cerevisiae. Here we present evidence that MIG1, a zinc-finger protein in the EGR1/Zif268 family, recruits SSN6-TUP1 to glucose-repressed promoters. DNA-bound LexA-MIG1 represses transcription of a target gene in glucose-grown cells, and repression requires SSN6 and TUP1. We also show that MIG1 and SSN6 fusion proteins interact in the two-hybrid system. Unexpectedly, we found that LexA-MIG1 activates transcription strongly in an ssn6 mutant and weakly in a tup1 mutant. Finally, LexA-MIG1 does not repress transcription in glucose-deprived cells, and MIG1 is differentially phosphorylated in response to glucose availability. We suggest a role for phosphorylation in regulating repression.
Loss of the catalytic subunit of the DNA-dependent protein kinase in DNA double-strand-break-repair mutant mammalian cells.
Authors: Peterson S R , Kurimasa A , Oshimura M , Dynan W S , Bradbury E M , Chen D J
Published: May 2006

The DNA-dependent protein kinase (DNA-PK) consists of three polypeptide components: Ku-70, Ku-80, and an approximately 350-kDa catalytic subunit (p350). The gene encoding the Ku-80 subunit is identical to the x-ray-sensitive group 5 complementing gene XRCC5. Expression of the Ku-80 cDNA rescues both DNA double-strand break (DSB) repair and V(D)J recombination in group 5 mutant cells. The involvement of Ku-80 in these processes suggests that the underlying defect in these mutant cells may be disruption of the DNA-PK holoenzyme. In this report we show that the p350 kinase subunit is deleted in cells derived from the severe combined immunodeficiency mouse and in the Chinese hamster ovary cell line V-3, both of which are defective in DSB repair and V(D)J recombination. A centromeric fragment of human chromosome 8 that complements the scid defect also restores p350 protein expression and rescues in vitro DNA-PK activity. These data suggest the scid gene may encode the p350 protein or regulate its expression and are consistent with a model whereby DNA-PK is a critical component of the DSB-repair pathway.
Inhibitory effect of 9-(2-phosphonylmethoxyethyl)adenine on visna virus infection in lambs: a model for in vivo testing of candidate anti-human immunodeficiency virus drugs.
Authors: Thormar H , Georgsson G , Pálsson P A , Balzarini J , Naesens L , Torsteinsdóttir S , De Clercq E
Published: May 2006

The acyclic nucleoside phosphonate analog 9-(2-phosphonylmethoxyethyl)adenine (PMEA) was recently found to be effective as an inhibitor of visna virus replication and cytopathic effect in sheep choroid plexus cultures. To study whether PMEA also affects visna virus infection in sheep, two groups of four lambs each were inoculated intracerebrally with 10(6.3) TCID50 of visna virus strain KV1772 and treated subcutaneously three times a week with PMEA at 10 and 25 mg/kg, respectively. The treatment was begun on the day of virus inoculation and continued for 6 weeks. A group of four lambs were infected in the same way but were not treated. The lambs were bled weekly or biweekly and the leukocytes were tested for virus. At 7 weeks after infection, the animals were sacrificed, and cerebrospinal fluid (CSF) and samples of tissue from various areas of the brain and from lungs, spleen, and lymph nodes were collected for isolation of virus and for histopathologic examination. The PMEA treatment had a striking effect on visna virus infection, which was similar for both doses of the drug. Thus, the frequency of virus isolations was much lower in PMEA-treated than in untreated lambs. The difference was particularly pronounced in the blood, CSF, and brain tissue. Furthermore, CSF cell counts were much lower and inflammatory lesions in the brain were much less severe in the treated lambs than in the untreated controls. The results indicate that PMEA inhibits the propagation and spread of visna virus in infected lambs and prevents brain lesions, at least during early infection. The drug caused no noticeable side effects during the 6 weeks of treatment.
Promotion of purine nucleotide binding to thymidylate synthase by a potent folate analogue inhibitor, 1843U89.
Authors: Weichsel A , Montfort W R , Cieśla J , Maley F
Published: May 2006

A folate analogue, 1843U89 (U89), with potential as a chemotherapeutic agent due to its potent and specific inhibition of thymidylate synthase (TS; EC 2.1.1.45), greatly enhances not only the binding of 5-fluoro-2'-deoxyuridine 5'-monophosphate (FdUMP) and dUMP to Escherichia coli TS but also that of dGMP, GMP, dIMP, and IMP. Guanine nucleotide binding was first detected by CD analysis, which revealed a unique spectrum for the TS-dGMP-U89 ternary complex. The quantitative binding of dGMP relative to GMP, FdUMP, and dUMP was determined in the presence and absence of U89 by ultrafiltration analysis, which revealed that although the binding of GMP and dGMP could not be detected in the absence of U89 both were bound in its presence. The Kd for dGMP was about the same as that for dUMP and FdUMP, with binding of the latter two nucleotides being increased by two orders of magnitude by U89. An explanation for the binding of dGMP was provided by x-ray diffraction studies that revealed an extensive stacking interaction between the guanine of dGMP and the benzoquinazoline ring of U89 and hydrogen bonds similar to those involved in dUMP binding. In addition, binding energy was provided through a water molecule that formed hydrogen bonds to both N7 of dGMP and the hydroxyl of Tyr-94. Accommodation of the larger dGMP molecule was accomplished through a distortion of the active site and a shift of the deoxyribose moiety to a new position. These rearrangements also enabled the binding of GMP to occur by creating a pocket for the ribose 2' hydroxyl group, overcoming the normal TS discrimination against nucleotides containing the 2' hydroxyl.
Degradation of sigma 32, the heat shock regulator in Escherichia coli, is governed by HflB.
Authors: Herman C , Thévenet D , D'Ari R , Bouloc P
Published: May 2006

The heat shock response in Escherichia coli is governed by the concentration of the highly unstable sigma factor sigma 32. The essential protein HflB (FtsH), known to control proteolysis of the phage lambda cII protein, also governs sigma 32 degradation: an HflB-depleted strain accumulated sigma 32 and induced the heat shock response, and the half-life of sigma 32 increased by a factor up to 12 in mutants with reduced HflB function and decreased by a factor of 1.8 in a strain overexpressing HflB. The hflB gene is in the ftsJ-hflB operon, one promoter of which is positively regulated by heat shock and sigma 32. The lambda cIII protein, which stabilizes sigma 32 and lambda cII, appears to inhibit the HflB-governed protease. The E. coli HflB protein controls the stability of two master regulators, lambda cII and sigma 32, responsible for the lysis-lysogeny decision of phage lambda and the heat shock response of the host.
Xce haplotypes show modified methylation in a region of the active X chromosome lying 3' to Xist.
Authors: Courtier B , Heard E , Avner P
Published: May 2006

During early mammalian embryogenesis, one of the two X chromosomes in somatic cells of the female becomes inactivated through a process that is thought to depend on a unique initiator region, the X-chromosome inactivation center (Xic). The recently characterized Xist sequence (X-inactive-specific transcript) is thought to be a possible candidate for Xic. In mice a further genetic element, the X chromosome-controlling element (Xce), is also known to influence the choice of which of the two X chromosomes is inactivated. We report that a region of the mouse X chromosome lying 15 kb distal to Xist contains several sites that show hypermethylation specifically associated with the active X chromosome. Analysis of this region in various Xce strains has revealed a correlation between the strength of the Xce allele carried and the methylation status of this region. We propose that such a region could be involved in the initial stages of the inactivation process and in particular in the choice of which of the two X chromosomes present in a female cell will be inactivated.
Constitutive activation of phototransduction by K296E opsin is not a cause of photoreceptor degeneration.
Authors: Li T , Franson W K , Gordon J W , Berson E L , Dryja T P
Published: May 2006

The missense mutation Lys-296-->Glu (K296E) in the rhodopsin gene produces an opsin with no chromophore binding site and therefore is not activated by light. Nevertheless, the mutant opsin constitutively activates transducin in vitro and causes photoreceptor degeneration in vivo, possibly by continuously activating the phototransduction cascade, analogous to constant exposure to environmental light. We studied the K296E mutation in eight lines of transgenic mice. Each line developed photoreceptor degeneration with the rate of degeneration increasing monotonically as the ratio of mutant:wild-type opsin mRNA increased. At no time in the course of degeneration was there endogenous light adaptation in the retina as measured by the electroretinogram. The mutant opsin was found to be invariably phosphorylated and stably bound to arrestin. Light-independent activation of transducin was demonstrated only after the removal of arrestin and dephosphorylation of K296E opsin. Thus, K296E opsin in vivo does not activate the phototransduction cascade because it is shut off by photoreceptor inactivation mechanisms. Our data show that the K296E mutation does not cause photoreceptor degeneration by continuous activation of phototransduction.
Types of evolutionary stability and the problem of cooperation.
Authors: Bendor J , Swistak P
Published: May 2006

The evolutionary stability of cooperation is a problem of fundamental importance for the biological and social sciences. Different claims have been made about this issue: whereas Axelrod and Hamilton's [Axelrod, R. & Hamilton, W. (1981) Science 211, 1390-1398] widely recognized conclusion is that cooperative rules such as "tit for tat" are evolutionarily stable strategies in the iterated prisoner's dilemma (IPD), Boyd and Lorberbaum [Boyd, R. & Lorberbaum, J. (1987) Nature (London) 327, 58-59] have claimed that no pure strategy is evolutionarily stable in this game. Here we explain why these claims are not contradictory by showing in what sense strategies in the IPD can and cannot be stable and by creating a conceptual framework that yields the type of evolutionary stability attainable in the IPD and in repeated games in general. Having established the relevant concept of stability, we report theorems on some basic properties of strategies that are stable in this sense. We first show that the IPD has "too many" such strategies, so that being stable does not discriminate among behavioral rules. Stable strategies differ, however, on a property that is crucial for their evolutionary survival--the size of the invasion they can resist. This property can be interpreted as a strategy's evolutionary robustness. Conditionally cooperative strategies such as tit for tat are the most robust. Cooperative behavior supported by these strategies is the most robust evolutionary equilibrium: the easiest to attain, and the hardest to disrupt.
Prevention of autoimmune demyelination in non-human primates by a cAMP-specific phosphodiesterase inhibitor.
Authors: Genain C P , Roberts T , Davis R L , Nguyen M H , Uccelli A , Faulds D , Li Y , Hedgpeth J , Hauser S L
Published: May 2006

Experimental allergic encephalomyelitis (EAE) is an autoimmune disease of the central nervous system that serves as a model for the human disease multiple sclerosis. We evaluated rolipram, a type IV phosphodiesterase inhibitor, for its efficacy in preventing EAE in the common marmoset Callithrix jacchus. In a blinded experimental design, clinical signs of EAE developed within 17 days of immunization with human white matter in two placebo-treated animals but in none of three monkeys that received rolipram (10 mg/kg s.c. every other day) beginning 1 week after immunization. In controls, signs of EAE were associated with development of cerebrospinal fluid pleocytosis and cerebral MRI abnormalities. In the treatment group, there was sustained protection from clinical EAE, transient cerebrospinal fluid pleocytosis in only one of three animals, no MRI abnormality, and marked reduction in histopathologic findings. Rolipram-treated and control animals equally developed circulating antibodies to myelin basic protein. Thus, inhibition of type IV phosphodiesterase, initiated after sensitization to central nervous system antigens, protected against autoimmune demyelinating disease.
Inactivation of ethanol-inducible cytochrome P450 and other microsomal P450 isozymes by trans-4-hydroxy-2-nonenal, a major product of membrane lipid peroxidation.
Authors: Bestervelt L L , Vaz A D , Coon M J
Published: May 2006

Of the microsomal P450 cytochromes, the ethanol-inducible isoform, P450 2E1, is believed to be predominant in leading to oxidative damage, including the generation of radical species that contribute to lipid peroxidation, and in the reductive beta-scission of lipid hydroperoxides to give hydrocarbons and aldehydes. In the present study, the sensitivity of a series of P450s to trans-4-hydroxy-2-nonenal (HNE), a known toxic product of membrane lipid peroxidation, was determined. After incubation of a purified cytochrome with HNE, the other components of the reconstituted system (NADPH-cytochrome P450 reductase, phosphatidylcholine, and NADPH) were added, and the rate of oxygenation of 1-phenylethanol to yield acetophenone was assayed. Inactivation occurs in a time-dependent and HNE concentration-dependent manner, with P450s 2E1 and 1A1 being the most sensitive, followed by isoforms 1A2, 3A6, and 2B4. At an HNE concentration of 0.24 microM, which was close to the micromolar concentration of the enzyme, four of the isoforms were significantly inhibited, but not P450 2B4. In other experiments, the reductase was shown to be only relatively weakly inactivated by HNE. P450s 2E1 and 2B4 in microsomal membranes from animals induced with acetone or phenobarbital, respectively, are as readily inhibited as the purified forms. Evidence was obtained that the P450 heme is apparently not altered and the sulfur ligand is not displaced, that substrate protects against HNE, and that the inactivation is reversed upon dialysis. Higher levels of reductase or substrate do not restore the activity of inhibited P450 in the catalytic assay. Our results suggest that the observed inhibition of the various P450s is of sufficient magnitude to cause significant changes in the metabolism of foreign compounds such as drugs and chemical carcinogens by the P450 oxygenase system at HNE concentrations that occur in biological membranes. In view of the known activities of P450 2E1 in generating lipid hydroperoxides and in their beta-scission, its inhibition by this product of membrane peroxidation may provide a negative regulatory function.
Pericellular mobilization of the tissue-destructive cysteine proteinases, cathepsins B, L, and S, by human monocyte-derived macrophages.
Authors: Reddy V Y , Zhang Q Y , Weiss S J
Published: May 2006

Human macrophages are believed to damage host tissues in chronic inflammatory disease states, but these cells have been reported to express only modest degradative activity in vitro. However, while examining the ability of human monocytes to degrade the extracellular matrix component elastin, we identified culture conditions under which the cells matured into a macrophage population that displayed a degradative phenotype hundreds of times more destructive than that previously ascribed to any other cell population. The monocyte-derived macrophages synthesized elastinolytic matrix metalloproteinases (i.e., gelatinase B and matrilysin) as well as cysteine proteinases (i.e., cathepsins B, L, and S), but only the cathepsins were detected in the extracellular milieu as fully processed, mature enzymes by either vital fluorescence or active-site labeling. Consistent with these observations, macrophage-mediated elastinolytic activity was not affected by matrix metalloproteinase inhibitors but could be almost completely abrogated by inhibiting cathepsins L and S. These data demonstrate that human macrophages mobilize cysteine proteinases to arm themselves with a powerful effector mechanism that can participate in the pathophysiologic remodeling of the extracellular matrix.
Prenatal monocular enucleation induces a selective loss of low-spatial-frequency cortical responses to the remaining eye.
Authors: Bisti S , Trimarchi C , Turlejski K
Published: May 2006

During early development, interactions between the two eyes are critical in the formation of eye-specific domains within the lateral geniculate nucleus and the visual cortex. When monocular enucleation is done early in prenatal life, it induces remarkable anatomical and functional reorganizations of the visual pathways. Behavioral data have shown a loss in sensitivity to low-spatial-frequency gratings in cats. To correlate the behavioral observations with a possible change in the analysis of contrast at the level of primary visual areas we recorded visual evoked potentials at the 17/18 border in two cats enucleated prenatally (gestational age at enucleation, 39-42 days), three neonatal, two control animals, and one animal with a surgical removal of Y-ganglion fibers. Our results show a strong attenuation in the amplitude of response at all contrast values for gratings of low spatial frequency in prenatally enucleated cats, whereas neonatally enucleated and control animals present responses of comparable amplitude. We conclude that the behavioral results reflect the reduced sensitivity for low frequencies of visual cortical neurons. In addition, we define a critical period for the development of the contrast-sensitivity function that seems to be limited to the prenatal gestation period. We suggest that the prenatal interruption of binocular interactions leads to a functional elimination of the Y-ganglion system.
A Xenopus distal-less gene in transgenic mice: conserved regulation in distal limb epidermis and other sites of epithelial-mesenchymal interaction.
Authors: Morasso M I , Mahon K A , Sargent T D
Published: May 2006

In this paper, we show the conserved regulation of the homeodomain gene Distal-less-3 (Dlx-3) by analyzing the expression of a promoter from the Xenopus ortholog, Xdll-2, in transgenic mice. A 470-bp frog regulatory sequence confers appropriate expression on a lacZ reporter gene in the ectodermal component of structures derived from epithelial-mesenchymal interactions. Remarkably, this includes structures absent in Xenopus, such as the hair follicle and mammary gland, suggesting that conserved regulatory elements can be used to control the formation of structures peculiar to individual species. In addition, expression of Dlx-3 in developing limbs is highest at the most distal portion. This pattern is duplicated by the Xenopus promoter, indicating that this DNA may include sequences responsive to conserved proximodistal patterning signals in the vertebrate limb.
An intimate collaboration between peroxisomes and lipid bodies
Authors: Binns Derk , Januszewski Tom , Chen Yue , Hill Justin , Markin Vladislav S. , Zhao Yingming , Gilpin Christopher , Chapman Kent D. , Anderson Richard G.W. , Goodman Joel M.
Published: May 2006

Although peroxisomes oxidize lipids, the metabolism of lipid bodies and peroxisomes is thought to be largely uncoupled from one another. In this study, using oleic acid–cultured Saccharomyces cerevisiae as a model system, we provide evidence that lipid bodies and peroxisomes have a close physiological relationship. Peroxisomes adhere stably to lipid bodies, and they can even extend processes into lipid body cores. Biochemical experiments and proteomic analysis of the purified lipid bodies suggest that these processes are limited to enzymes of fatty acid β oxidation. Peroxisomes that are unable to oxidize fatty acids promote novel structures within lipid bodies (“gnarls”), which may be organized arrays of accumulated free fatty acids. However, gnarls are suppressed, and fatty acids are not accumulated in the absence of peroxisomal membranes. Our results suggest that the extensive physical contact between peroxisomes and lipid bodies promotes the coupling of lipolysis within lipid bodies with peroxisomal fatty acid oxidation.
Tetrathiobacter mimigardefordensis sp. nov., isolated from compost, a betaproteobacterium capable of utilizing the organic disulfide 3,3′-dithiodipropionic acid
Authors: Wübbeler Jan Hendrik , Lütke-Eversloh Tina , Van Trappen Stefanie , Vandamme Peter , Steinbüchel Alexander
Published: May 2006

In this study, a novel betaproteobacterium, strain DPN7T, was isolated under mesophilic conditions from compost because of its capacity to utilize the organic disulfide 3,3′-dithiodipropionic acid. Analysis of the 16S rRNA gene sequence of strain DPN7T revealed 98.5 % similarity to that of Tetrathiobacter kashmirensis LMG 22695T. Values for sequence similarity to members of the genera Alcaligenes, Castellaniella and Taylorella, the nearest neighbours of the genus Tetrathiobacter, were about 95 % or less. The DNA G+C content of strain DPN7T was 55.1 mol%. The level of DNA–DNA hybridization between strain DPN7T and T. kashmirensis LMG 22695T was 41 %, whereas it was much lower between strain DPN7T and Alcaligenes faecalis LMG 1229T (7 %) or Castellaniella defragrans LMG 18538T (5 %). This genotypic divergence was supported by differences in biochemical and chemotaxonomic characteristics. For this reason, and because of the differences in the protein and fatty acid profiles, strain DPN7T should be classified within a novel species of Tetrathiobacter, for which the name Tetrathiobacter mimigardefordensis sp. nov. is proposed. The type strain is strain DPN7T (=DSM 17166T=LMG 22922T).
Dispensable genes and foreign DNA in Streptococcus mutans
Authors: Waterhouse Janet C. , Russell Roy R. B.
Published: May 2006

A range of properties, including the ability to utilize various sugars, bind macromolecules and produce mutacins, are known to vary in their occurrence in different strains ofStreptococcus mutans. In addition, insertion-sequence elements show a limited distribution and sequencing of the genome ofS. mutansUA159 has revealed the presence of putative genomic islands of atypical base composition indicative of foreign DNA. PCR primers flanking regions suspected of having inserted DNA were designed on the basis of the genome sequence ofS. mutansUA159 and used to explore variation in a collection of 39 strains isolated in various parts of the world over the last 40 years. Extensive differences between strains were detected, and similar insertion/deletion events appear to be present in the genomes of strains with very different origins. In two instances, insertion of foreign DNA appears to have displaced originalS. mutansgenes. Together with previous results on the occurrence of deletions in genes associated with sugar metabolism, the results indicate thatS. mutanshas a core genome and a dispensable genome, and that dispensable genes have become widely distributed through horizontal transfer.
A plasmid-cured Chlamydia muridarum strain displays altered plaque morphology and reduced infectivity in cell culture
Authors: O'Connell Catherine M. , Nicks Kristy M.
Published: May 2006

A highly conserved cryptic plasmid is present inChlamydia trachomatisyet naturally occurring plasmid-deficient isolates are very rare. This paper describes the isolation and characterization of a plasmid-deficient strain ofC. muridarum, using novobiocin as a curing agent. Plasmid-deficient derivatives ofC. muridarumstrain Nigg were generated at high efficiencies (4–30 %). Phenotypic characterization revealed that the cured derivative was unable to accumulate glycogen within intracytoplasmic inclusions. In addition, this strain formed small plaques at a reduced efficiency compared to the wild-type parent.
TWELVE CASES OF ACUTE ESOPHAGEAL MUCOSAL LESION
Authors: Tsumura Takehiko , Maruo Takanori , Tsuji Kentaro , Osaki Yukio , Tomono Naomi
Published: May 2006

Background and Aims:  The incidence of erosive esophagitis in emergent endoscopy for upper gastrointestinal bleeding is not rare but the clinical and endoscopic findings have not been fully investigated. The aim of the present study was to clarify features of acute esophagitis cases showing acute onset and severe endoscopic findings.

Methods:  We defined severe esophagitis that endoscopically showed circumferential diffuse mucosal lesion involving at least the entire lower third of the esophagus as acute esophageal mucosal lesion and investigated the clinical and endoscopic characteristics.

Results:  We experienced six cases of black or dark esophagitis and six cases of non‐black esophagitis. Both groups showed common clinical features. Patients were predominantly males older than middle age. The presenting symptoms were upper gastrointestinal bleeding such as coffee‐ground‐like vomit, hematemesis or tarry stool. Seven cases had a history of taking non‐steroidal anti‐inflammatory drugs. Endoscopically, both types of case showed diffuse circumferential erosion in the lower esophagus, which continuously extended, and worsened towards the esophagogastric junction. All had esophageal sliding hernia and five cases had duodenal mucosal lesion. All cases rapidly improved with a proton pump inhibitor except one case.

Conclusion:  Black and non‐black esophagitis was considered to belong to the same disease entity, acute esophageal mucosal lesion, which should be recognized as a differential diagnosis on emergency endoscopy for upper gastrointestinal bleeding.
NF‐κB Activation Pathway is Essential for the Chemokine Expression in Intestinal Epithelial Cells Stimulated with Clostridium difficile Toxin A
Authors: Kim J. M. , Lee J. Y. , Yoon Y. M. , Oh Y.‐K. , Youn J. , Kim Y.‐J.
Published: May 2006

Intestinal epithelial cells are known to upregulate the expression of several chemokines in response to stimulation with bacterial toxin. However, the cellular mechanisms of Clostridium difficile toxin A‐induced mucosal inflammation have not yet been fully elucidated. In this study, we investigated whether nuclear factor‐kappa B (NF‐κB) could regulate chemokine expression in intestinal epithelial cells. Toxin A increased the levels of NF‐κB complexes containing p65/p50 heterodimers and p65/p65 homodimers. Concurrently, toxin A decreased the levels of IκBα. Toxin A stimulation also increased the signals of phosphorylated IκB kinase (IKK)α/β and NF‐κB‐inducing kinase (NIK). In the toxin A‐stimulated HT‐29 cells, the suppression of IKK or NIK inhibited the upregulation of downstream target genes of NF‐κB such as IL‐8 and monocyte‐chemotactic protein (MCP)‐1 and similarly, inhibition of NF‐κB also downregulated the expression of IL‐8, growth‐related oncogene‐α, and MCP‐1. These results suggest that NF‐κB signalling events may be involved in the inflammatory responses to toxin A produced by toxigenic C. difficile.
Effects of melatonin on the oxidant/antioxidant status and lung histopathology in rabbits exposed to cigarette smoke
Authors: UNLU Mehmet , FIDAN Fatma , SEZER Murat , TETIK Levent , SAHIN Onder , ESME Hidir , KOKEN Tulay , SERTESER Mustafa
Published: May 2006

Objectives and background:  To evaluate the effects of cigarette smoking on the histopathology and the oxidant/antioxidant status of the lungs and to test the potential antioxidant benefits of melatonin on these induced changes.

Methodology:  Rabbits were exposed to cigarette smoke in a glass chamber for 1 h daily for 1 month with or without intraperitoneal melatonin injection. A melatonin control group was given intraperitoneal melatonin only. A control group was exposed to clean air only. At the end of 1 month, animals were sacrificed and lung tissues were examined histopathologically. Blood levels of protein sulphydryls, carbonyls, prostaglandin F2α (PGF2α), malondialdehyde (MDA), glutathione peroxidase and superoxide dismutase (SOD) were measured.

Results:  Intraparenchymal vascular congestion and thrombosis, intraparenchymal haemorrhage, respiratory epithelial proliferation, number of macrophages in the alveolar and bronchial lumen, alveolar destruction, emphysematous changes and bronchoalveolar haemorrhage scores were significantly increased in rabbits exposed to cigarette smoke compared with the control group. Protein sulphydryls and SOD levels were significantly decreased; carbonyls, PGF2α and MDA levels were significantly increased in the smoke exposed rabbits. Administration of melatonin to rabbits exposed to cigarette smoke caused a reduction in the bronchoalveolar haemorrhage score and blood carbonyls levels. Other parameters were unaffected by melatonin.

Conclusion:  Exposure to cigarette smoke causes severe histopathological changes and negatively affects the oxidant/antioxidant status in the lungs of rabbits. A low daily dose of melatonin has some protective effects on histopathological changes and oxidant/antioxidant status of the lungs in smoke exposed rabbits.
Anxiolytic‐like effects of the selective metabotropic glutamate receptor 5 antagonist MPEP after its intra‐amygdaloid microinjection in three different non‐conditioned rat models of anxiety
Authors: De La Mora Miguel Pérez , Lara‐García Daniel , Jacobsen Kirsten X. , Vázquez‐García Mariana , Crespo‐Ramírez Minerva , Flores‐Gracia Candy , Escamilla‐Marvan Edgardo , Fuxe Kjell
Published: May 2006

The intercalated islands, clusters of dopamine D1‐rich GABAergic neurons, are interposed between the basolateral and central nuclei of the amygdala, and control the traffic of nerve impulses between these two structures. Metabotropic glutamate receptor 5‐ (mGluR5)‐like immunoreactivity was studied by immunohistochemistry in this part of the amygdala and was found to be mainly restricted to the central and basolateral nuclei and to a lesser extent to the medial paracapsular intercalated islands. The role of the metabotropic glutamate receptor 5 in the modulation of anxiety has been studied in this region by microinjection of small volumes of the mGluR5 antagonist 2‐methyl‐6(phenylethenyl) pyridine (MPEP), with restricted diffusion from its injection site, into the rostral amygdala near the basolateral and central amygdaloid nuclei and the intercalated islands, and the behavior of the animals was evaluated using three non‐conditioned models of anxiety. Anxiolytic‐like effects were observed after MPEP administration in all tests used. In the White and Black Box test, MPEP (2 nmol per side) significantly increased the time spent in the white compartment of the box. In line with these results, MPEP (8 nmol per side) increased the exploration of the open arms of the Elevated Plus‐Maze. Burying behavior latency was increased and burying behavior itself was decreased in the Shock‐Probe Burying test. It is suggested that anxiolytic effects of MPEP may be mediated by blockade of mGluR5 in the basolateral and/or central amygdaloid nuclei, reducing glutamate transmission in the basolateral amygdaloid nuclei and glutamate output from the central amygdala.
Chronic fluoxetine induces region‐specific changes in translation factor eIF4E and eEF2 activity in the rat brain
Authors: Dagestad Grethe , Kuipers Sjoukje D. , Messaoudi Elhoucine , Bramham Clive R.
Published: May 2006

The delayed therapeutic onset observed in response to chronic antidepressant drug treatment is little understood. While current theories emphasize effects on gene transcription, possible effects of antidepressant drugs on translation control pathways have not been explored. We examined the effect of the selective serotonergic reuptake inhibitor fluoxetine on regulation of two major determinants of mRNA translation, eukaryotic initiation factor 4E (eIF4E) and eukaryotic elongation factor 2 (eEF2). Chronic fluoxetine treatment induced hyperphosphorylation of eEF2 (Thr56) in prefrontal cortex, hippocampus and dentate gyrus of rats. By contrast, phosphorylation of eIF4E (Ser209) was observed specifically in the dentate gyrus. Acute fluoxetine treatment had no effect on translational factor activity. These findings suggest that region‐specific regulation of translation contributes to the delayed action of antidepressant drugs such as fluoxetine.
China's Recent Economic Performance and Future Prospects*
Authors: PERKINS Dwight H.
Published: May 2006

Our forecast of China's economic future is based primarily on the supply side growth accounting model. The life cycle model of household saving provides us with the most plausible explanation for a continued high rate of savings and investment. China's labor force will soon stop growing, but migration out of agriculture should have little impact on farm output while providing a steady stream of labor to the modern more productive sectors. There is also room for rapid expansion of human capital. Maintaining high productivity growth will depend primarily on strengthening currently weak institutions, notably the financial sector and, more importantly, the legal system.