bluuebunny/crossref_metadata_2025 huggingface dataset:
Sphingolipid C-9 Methyltransferases Are Important for Growth and Virulence but Not for Sensitivity to Antifungal Plant Defensins inFusarium graminearum
Authors: Ramamoorthy Vellaisamy , Cahoon Edgar B. , Thokala Mercy , Kaur Jagdeep , Li Jia , Shah Dilip M.
Published: November 2008

The C-9-methylated glucosylceramides (GlcCers) are sphingolipids unique to fungi. They play important roles in fungal growth and pathogenesis, and they act as receptors for some antifungal plant defensins. We have identified two genes, FgMT1and FgMT2, that each encode a putative sphingolipid C-9 methyltransferase (C-9-MT) in the fungal pathogenFusarium graminearumand complement aPichia pastorisC-9-MT-null mutant. The ΔFgmt1mutant produced C-9-methylated GlcCer like the wild-type strain, PH-1, whereas the ΔFgmt2mutant produced 65 to 75% nonmethylated and 25 to 35% methylated GlcCer. No ΔFgmt1ΔFgmt2double-knockout mutant producing only nonmethylated GlcCer could be recovered, suggesting that perhaps C-9-MTs are essential in this pathogen. This is in contrast to the nonessential nature of this enzyme in the unicellular fungusP. pastoris. The ΔFgmt2mutant exhibited severe growth defects and produced abnormal conidia, while the ΔFgmt1mutant grew like the wild-type strain, PH-1, under the conditions tested. The ΔFgmt2mutant also exhibited drastically reduced disease symptoms in wheat and much-delayed disease symptoms inArabidopsis thaliana. Surprisingly, the ΔFgmt2mutant was less virulent on different host plants tested than the previously characterized ΔFggcs1mutant, which lacks GlcCer synthase activity and produces no GlcCer at all. Moreover, the ΔFgmt1and ΔFgmt2mutants, as well as theP. pastorisstrain in which the C-9-MT gene was deleted, retained sensitivity to the antifungal plant defensins MsDef1 and RsAFP2, indicating that the C-9 methyl group is not a critical structural feature of the GlcCer receptor required for the antifungal action of plant defensins.
Transcriptional Profiling Identifies a Role for BrlA in the Response to Nitrogen Depletion and for StuA in the Regulation of Secondary Metabolite Clusters in
Aspergillus fumigatus
Authors: Twumasi-Boateng Kwame , Yu Yan , Chen Dan , Gravelat Fabrice N. , Nierman William C. , Sheppard Donald C.
Published: November 2008

Conidiation (asexual sporulation) is a key developmental process in filamentous fungi. We examined the gene regulatory roles of the
Aspergillus fumigatus
developmental transcription factors StuAp and BrlAp during conidiation. Conidiation was completely abrogated in an
A. fumigatus
Δ
brlA
mutant and was severely impaired in a Δ
stuA
mutant. We determined the full genome conidiation transcriptomes of wild-type and Δ
brlA
and Δ
stuA
mutant
A. fumigatus
and found that BrlAp and StuAp governed overlapping but distinct transcriptional programs. Six secondary metabolite biosynthetic clusters were found to be regulated by StuAp, while only one cluster exhibited BrlAp-dependent expression. The Δ
brlA
mutant, but not the Δ
stuA
mutant, had impaired downregulation of genes encoding ribosomal proteins under nitrogen-limiting, but not carbon-limiting, conditions. Interestingly, inhibition of the target of rapamycin (TOR) pathway also caused downregulation of ribosomal protein genes in both the wild-type strain and the Δ
brlA
mutant. Downregulation of these genes by TOR inhibition was associated with conidiation in the wild-type strain but not in the Δ
brlA
mutant. Therefore, BrlAp-mediated repression of ribosomal protein gene expression is not downstream of the TOR pathway. Furthermore, inhibition of ribosomal protein gene expression is not sufficient to induce conidiation in the absence of BrlAp.
Evidence of a Reduced and Modified Mitochondrial Protein Import Apparatus in Microsporidian Mitosomes
Authors: Waller Ross F. , Jabbour Carole , Chan Nickie C. , Celik Nermin , Likić Vladimir A. , Mulhern Terrence D. , Lithgow Trevor
Published: November 2008

Microsporidia are a group of highly adapted obligate intracellular parasites that are now recognized as close relatives of fungi. Their adaptation to parasitism has resulted in broad and severe reduction at (i) a genomic level by extensive gene loss, gene compaction, and gene shortening; (ii) a biochemical level with the loss of much basic metabolism; and (iii) a cellular level, resulting in lost or cryptic organelles. Consistent with this trend, the mitochondrion is severely reduced, lacking ATP synthesis and other typical functions and apparently containing only a fraction of the proteins of canonical mitochondria. We have investigated the mitochondrial protein import apparatus of this reduced organelle in the microsporidian
Encephalitozoon cuniculi
and find evidence of reduced and modified machinery. Notably, a putative outer membrane receptor, Tom70, is reduced in length but maintains a conserved structure chiefly consisting of tetratricopeptide repeats. When expressed in
Saccharomyces cerevisiae
, EcTom70 inserts with the correct topology into the outer membrane of mitochondria but is unable to complement the growth defects of Tom70-deficient yeast. We have scanned genomic data using hidden Markov models for other homologues of import machinery proteins and find evidence of severe reduction of this system.
Glucose- and Glucokinase-ControlledmalGene Expression inEscherichia coli
Authors: Lengsfeld Christina , Schönert Stefan , Dippel Renate , Boos Winfried
Published: November 2008

MalT is the central transcriptional activator of allmalgenes inEscherichia coli. Its activity is controlled by the inducer maltotriose. It can be inhibited by the interaction with certain proteins, and its expression can be controlled. We report here a novel aspect ofmalgene regulation: the effect of cytoplasmic glucose and glucokinase (Glk) on the activity and the expression of MalT. Amylomaltase (MalQ) is essential for the metabolism of maltose. It forms maltodextrins and glucose from maltose or maltodextrins. We found that glucose above a concentration of 0.1 mM blocked the activity of the enzyme.malQmutants when grown in the absence of maltodextrins are endogenously induced by maltotriose that is derived from the degradation of glycogen. Therefore, the fact thatglk malQ+mutants showed elevatedmalgene expression finds its explanation in the reduced ability to remove glucose from MalQ-catalyzed maltodextrin formation and is caused by a metabolically induced MalQ−phenotype. However, even in mutants lacking glycogen, Glk controls endogenous induction. We found that overexpressed Glk due to its structural similarity with Mlc, the repressor ofmalT, binds to the glucose transporter (PtsG), releasing Mlc and thus increasingmalTrepression. In addition, even in mutants lacking Mlc (and glycogen), the overexpression ofglkleads to a reduction inmalgene expression. We interpret this repression by a direct interaction of Glk with MalT concomitant with MalT inhibition. This repression was dependent on the presence of either maltodextrin phosphorylase or amylomaltase and led to the inactivation of MalT.
Response ofPorphyromonas gingivalisto Heme Limitation in Continuous Culture
Authors: Dashper Stuart G. , Ang Ching-Seng , Veith Paul D. , Mitchell Helen L. , Lo Alvin W. H. , Seers Christine A. , Walsh Katrina A. , Slakeski Nada , Chen Dina , Lissel J. Patricia , Butler Catherine A. , O'Brien-Simpson Neil M. , Barr Ian G. , Reynolds Eric C.
Published: November 2008

Porphyromonas gingivalisis an anaerobic, asaccharolytic, gram-negative bacterium that has essential requirements for both iron and protoporphyrin IX, which it preferentially obtains as heme. A combination of large-scale quantitative proteomic analysis using stable isotope labeling strategies and mass spectrometry, together with transcriptomic analysis using custom-made DNA microarrays, was used to identify changes inP. gingivalisW50 protein and transcript abundances on changing from heme-excess to heme-limited continuous culture. This approach identified 160 genes and 70 proteins that were differentially regulated by heme availability, with broad agreement between the transcriptomic and proteomic data. A change in abundance of the enzymes of the aspartate and glutamate catabolic pathways was observed with heme limitation, which was reflected in organic acid end product levels of the culture fluid. These results demonstrate a shift from an energy-efficient anaerobic respiration to a less efficient process upon heme limitation. Heme limitation also resulted in an increase in abundance of a protein, PG1374, which we have demonstrated, by insertional inactivation, to have a role in epithelial cell invasion. The greater abundance of a number of transcripts/proteins linked to invasion of host cells, the oxidative stress response, iron/heme transport, and virulence of the bacterium indicates that there is a broad response ofP. gingivalisto heme availability.
Insertion and Deletion Events That Define the PathogenMycobacterium aviumsubsp.paratuberculosis
Authors: Alexander David C. , Turenne Christine Y. , Behr Marcel A.
Published: November 2008

Mycobacterium aviumcomprises genetically related yet phenotypically distinct subspecies. Consistent with their common origin, whole-genome sequence comparisons have revealed extensive synteny amongM. aviumorganisms. However, the sequenced strains also display numerous regions of heterogeneity that likely contribute to the diversity of the individual subspecies. Starting from a phylogenetic framework derived by multilocus sequence analysis, we examined the distribution of 25 large sequence polymorphisms across a panel of genetically definedM. aviumstrains. This distribution was most variable amongM. aviumsubsp.hominissuisisolates. In contrast,M. aviumsubsp.paratuberculosisstrains exhibited a characteristic profile, with all isolates containing a set of genomic insertions absent from otherM. aviumstrains. The emergence of the pathogen from its putativeM. aviumsubsp.hominissuisancestor entailed the acquisition of approximately 125 kb of novel genetic material, followed by a second phase, characterized by reductive genomics. One genomic deletion is common to all isolates while additional deletions distinguish two major lineages ofM. aviumsubsp.paratuberculosis. For the average strain, these losses total at least 38 kb (sheep lineage) to 90 kb (cattle lineage). This biphasic pattern of evolution, characterized by chromosomal gene acquisition with subsequent gene loss, describes the emergence ofM. aviumsubsp.paratuberculosisand may serve as a general model for the origin of pathogenic mycobacteria.
Identification and Characterization of NocR as a Positive Transcriptional Regulator of the β-Lactam Nocardicin A inNocardia uniformis
Authors: Davidsen Jeanne M. , Townsend Craig A.
Published: November 2008

Nocardicin A is a monocyclic β-lactam isolated from the actinomyceteNocardia uniformis, which shows moderate activity against a broad spectrum of gram-negative bacteria. Within the biosynthetic gene cluster of nocardicin A,nocRencodes a 583-amino-acid protein with high similarity to a class of transcriptional regulators known asstreptomycesantibioticregulatoryproteins. Insertional inactivation of this gene resulted in a mutant showing morphology and growth characteristics similar to the wild type, but one that did not produce detectable levels of nocardicin A or the early precursorp-hydroxybenzoyl formate. Similar disruptions ofnocD,nocE, andnocOyielded mutants that maintained production of nocardicin A at levels similar to the wild-type strain. Intranscomplementation of thenocR::aprmutant partially restored the wild-type phenotype. Transcriptional analysis of thenocR::aprmutant using reverse transcription-PCR found an absence of mRNA transcripts for the early-stage nocardicin A biosynthetic genes. In addition, transcription of the genes responsible for the biosynthesis of the nonproteinogenicp-hydroxyphenylglycine (pHPG) precursor was attenuated on thenocRdisruption mutant. NocR was heterologously expressed and purified fromEscherichia colias an N-terminal maltose binding protein-tagged fusion protein. DNA binding assays demonstrated that NocR is a DNA binding protein, targeting the 126-bp intergenic region betweennocFandnocA. Within this intergenic region is the likely binding motif, a direct hexameric repeat, TGATAA, with a 5-bp spacer. These experiments establish NocR as a positive transcriptional regulator of the nocardicin A biosynthetic pathway, coordinating the initial steps of nocardicin A biosynthesis to the production of its pHPG precursor.
Imaging of the retinal nerve fibre layer for glaucoma
Authors: Townsend K A , Wollstein G , Schuman J S
Published: November 2008

Background:

Glaucoma is a group of diseases characterised by retinal ganglion cell dysfunction and death. Detection of glaucoma and its progression are based on identification of abnormalities or changes in the optic nerve head (ONH) or the retinal nerve fibre layer (RNFL), either functional or structural. This review will focus on the identification of structural abnormalities in the RNFL associated with glaucoma.

Discussion:

A variety of new techniques have been created and developed to move beyond photography, which generally requires subjective interpretation, to quantitative retinal imaging to measure RNFL loss. Scanning laser polarimetry uses polarised light to measure the RNFL birefringence to estimate tissue thickness. Optical coherence tomography (OCT) uses low-coherence light to create high-resolution tomographic images of the retina from backscattered light in order to measure the tissue thickness of the retinal layers and intraretinal structures. Segmentation algorithms are used to measure the thickness of the retinal nerve fibre layer directly from the OCT images. In addition to these clinically available technologies, new techniques are in the research stages. Polarisation-sensitive OCT has been developed that combines the strengths of scanning laser polarimetry with those of OCT. Ultra-fast techniques for OCT have been created for research devices. The continued utilisation of imaging devices into the clinic is refining glaucoma assessment. In the past 20 years glaucoma has gone from a disease diagnosed and followed using highly subjective techniques to one measured quantitatively and increasingly objectively.
Vibrio vulnificus: an unusual mode of acquisition and novel use of rapid susceptibility testing: Figure 1
Authors: Partridge D G , Townsend R , Larkin S , Parsons H K
Published: November 2008

Infection withVibrio vulnificusis uncommon in Europe but is associated with necrotising wound infections and life-threatening septicaemia. This case is one of infection most likely to have been acquired from a thermal pool in Turkey without preceding exposure to seawater or shellfish. The report also describes how early management was optimised using gradient diffusion antibiotic strips to provide rapid susceptibility data.
Incidence of acute pesticide poisonings in Nicaragua: a public health concern
Authors: Corriols M , Marín J , Berroteran J , Lozano L M , Lundberg I
Published: November 2008

Objectives:

To estimate the cumulative incidence rate of acute pesticide poisoning in the year 2000 among Nicaraguan subjects over 15 years of age.

Methods:

Data on pesticide exposure and health effects were assessed in a nationally representative survey. Based on self-reported cases, we estimated the 1-year incidence rate and the number of expected cases of acute pesticide poisonings in Nicaragua.

Results:

Among the 3169 survey respondents, we identified 72 persons who self-reported one episode of acute pesticide poisoning in 2000. Of these, 65 cases (90%) were related to occupational exposure, five (7%) to domestic exposure and two (3%) to intentional exposure. The cumulative incidence rate/100 individuals of pesticide poisonings in Nicaragua in 2000 was 2.3 (95% CI 1.7 to 2.8). This corresponds to 66 113 cases (95% CI 51 017 to 81 210). The highest rate was found among males in rural areas, particularly among farmers and agricultural workers.

Conclusion:

This study demonstrates an extremely high risk of acute pesticide poisoning in Nicaragua. Considering this, comprehensive measures should be implemented to reduce adverse health effects.
Biochemical Genetic Stock Identification of Chum Salmon (Oncorhynchus keta) in Southern British Columbia
Authors: Beacham Terry D. , Withler Ruth E. , Gould Allan P.
Published: November 2008

We used electrophoresis to examine genetic variability of 33 chum salmon (Oncorhynchus keta) stocks in southern British Columbia and used differences in genotypic frequencies among these stocks for estimating stock compositions in a weekly fishery in upper Johnstone Strait. Seven polymorphic loci were used for stock identification. Chum salmon from the Fraser River, Bute and Toba inlets, Vancouver Island, and the southern Mainland had significantly different allelic frequencies, but there was also significant heterogeneity in allelic frequencies at some loci within each region. Allelic frequencies were generally stable over a 2-yr period in nine stocks for which consecutive annual sampling was conducted. There was no significant two-locus linkage disequilibrium for the chum salmon stocks surveyed. Cluster analysis indicated that Fraser River and Bute and Toba Inlet stocks were distinctive, but Vancouver Island and Mainland stocks were not. The timing and relative abundance of Fraser River chum salmon in upper Johnstone Strait as estimated by electrophoretic analysis was confirmed by an in-river test fishery in the Fraser River.
Diet and Digestion Rates of Slimy Sculpin, Cottus cognatus, in an Alaskan Arctic Lake
Authors: Hershey Anne E. , McDonald Michael E.
Published: November 2008

In arctic Toolik Lake, slimy sculpin (Cottus cognatus) rely on a diet of larval chironomids (Diptera: Chironomidae). Dry weight of sculpin gut contents was not correlated with fish wet weight. This finding, combined with age and growth data, suggested that sculpin may be food limited in Toolik Lake, particularly as they approach reproductive size. Since three taxonomically distinct chironomids were digested at similar rates, one chironomid species was used as a marker to measure gut passage. Gut passage rate as a function of temperature fits an inverse quadratic model slightly better than a negative exponential model. Sculpins took approximately 1 d to digest food at typical summer temperatures (8–16 °C), but approximately 2 d at a typical winter temperature (4 °C). Since winter is three times longer than summer, winter feeding by sculpins may have greater impact on chironomid density than summer feeding. If sculpin are important in the diet of other Toolik Lake fishes, they may serve as an important trophic link between benthic and pelagic production.
Background Levels of Dissolved/Dispersed Petroleum Residues in the Gulf of St. Lawrence, 1970–79
Authors: Levy E. M.
Published: November 2008

A 10-yr program of monitoring the incidence and distribution of dissolved/dispersed petroleum residues in the Gulf of St. Lawrence confirmed that the major source is the Atlantic water that enters through Cabot Strait and demonstrated that a substantial decline in the background levels occurred during the mid-1970's. The present level, about 0.4 μg/L, is similar to those of other unpolluted areas off the east coast of Canada and in the Arctic where it appears that the input from atmospheric deposition exceeds those from accidental spills, deliberate discharges, and other point sources.
Bacterioplankton, Phytoplankton, and Zooplankton Communities in a British Columbia Coastal Lake Before and After Nutrient Reduction
Authors: Hardy F. Joan , Shortreed Ken S. , Stockner John G.
Published: November 2008

Inorganic nitrogen and phosphorus were applied weekly during the growing season from 1980 to 1982 and twice weekly in 1983 to Hobiton Lake, a warm monomictic coastal lake in British Columbia. The lake was not fertilized in 1984. Average numbers of bacteria during the growing season decreased from a high of 1.53 × 106∙mL−1 in the fertilized condition to 0.84 × 106∙mL−1 in the unfertilized condition. Chlorophyll a concentrations decreased from a maximum seasonal average of 2.69 μg∙L−1 (1981) to 1.30 μg∙L−1 (1984), and algal numbers decreased from 5.83 × 104∙mL−1 (1983) to 2.29 × 104∙mL−1 (1984). Although the numbers of phytoplankton in each size fraction (picoplankton, nanoplankton, or microplankton) decreased in the unfertilized condition, the greatest change was an almost fourfold decrease in picoplankton, which consisted of 90% cyanobacteria (primarily Synechococcus spp.). Abundance of the large diatoms Rhizosolenia spp. and Melosira spp. increased in 1984, resulting in an increase in average seasonal algal volume. Average densities of medium (0.15–0.84 mm) and large (0.85–1.5 mm) zooplankton were greatest in 1982, while rotifers and small zooplankton (0.10–0.14 mm) were most dense in 1984 following nutrient reduction. The lake had relatively high concentrations of planktivorous juvenile sockeye salmon (Oncorhynchus nerka) that appeared to minimize any direct effect of nutrient additions on zooplankton densities.
Woody Debris as a Source of Fine Particulate Organic Matter in Coniferous Forest Stream Ecosystems
Authors: Ward G. Milton , Aumen Nicholas G.
Published: November 2008

The potential contribution of woody debris to fine particulate organic matter pools (0.45 μm ≤ FROM < 1 mm) was investigated in a coniferous forest stream ecosystem in western Oregon. The amount of wetted surface area of both large (>10 cm) and fine woody debris (1–10 cm) was 0.018 and 0.069 m2∙m−2 stream bed, respectively, during summer base flow. These values increase to 0.062 and 0.195 m2∙m−2 stream bed during winter flows. Studies of vertical distribution indicated that most fine wood is concentrated within 0.3 m of the stream bottom, while large wood is more evenly distributed up to 0.7 m. Lignin concentrations of large wood, soil, and FROM were very similar. Examination of FPOM samples with scanning electron microscopy revealed an abundance of wood-derived particles. Erosion rates of wood surfaces ranged between 0.5 and 11 mm∙yr−1 depending on decay state of the log. Using conservative estimates of processing rates, woody debris could be a source for approximately 90 g∙m−2∙yr−1 of FPOM, but with slightly a less conservative estimate, wood processing could easily generate several times the FPOM that is contributed by leaf and needle litter.
POISSON BRACKET IN CLASSICAL FIELD THEORY AS A DERIVED BRACKET
Authors: POL'SHIN S. A.
Published: November 2008

We construct a Leibniz bracket on the space Ω• (Jk (π)) of all differential forms over the finite-dimensional jet bundle Jk (π). As an example, we write Maxwell equations with sources in the covariant finite-dimensional hamiltonian form.
GRAVITATIONAL WAVES ABOUT CURVED BACKGROUNDS: A CONSISTENCY ANALYSIS IN DE SITTER SPACETIME
Authors: BINI DONATO , CAPOZZIELLO SALVATORE , ESPOSITO GIAMPIERO
Published: November 2008

Gravitational waves are considered as metric perturbations about a curved background metric, rather than the flat Minkowski metric since several situations of physical interest can be discussed by this generalization. In this case, when the de Donder gauge is imposed, its preservation under infinitesimal spacetime diffeomorphisms is guaranteed if and only if the associated covector is ruled by a second-order hyperbolic operator which is the classical counterpart of the ghost operator in quantum gravity. In such a wave equation, the Ricci term has opposite sign with respect to the wave equation for Maxwell theory in the Lorenz gauge. We are, nevertheless, able to relate the solutions of the two problems, and the algorithm is applied to the case when the curved background geometry is the de Sitter spacetime. Such vector wave equations are studied in two different ways: (i) an integral representation, (ii) through a solution by factorization of the hyperbolic equation. The latter method is extended to the wave equation of metric perturbations in the de Sitter spacetime. This approach is a step towards a general discussion of gravitational waves in the de Sitter spacetime and might assume relevance in cosmology in order to study the stochastic background emerging from inflation.
Cannabinoid-1 (CB1) receptors regulate colonic propulsion by acting at motor neurons within the ascending motor pathways in mouse colon
Authors: Sibaev Andrei , Yüce Birol , Kemmer Markus , Van Nassauw Luc , Broedl Ulli , Allescher Hans D. , Göke Burkhard , Timmermans Jean-Pierre , Storr Martin
Published: November 2008

Cannabinoid-1 (CB1) receptors on myenteric neurons are involved in the regulation of intestinal motility. Our aim was to investigate CB1receptor involvement in ascending neurotransmission in mouse colon and to characterize the involved structures by functional and morphological means. Presence of the CB1receptor was investigated by RT-PCR, and immunohistochemistry was used for colabeling studies. Myenteric reflex responses were initiated by electrical stimulation (ES) at different distances, and junction potentials (JP) were recorded from circular smooth muscle cells by intracellular recording in an unpartitioned and a partitioned recording chamber. In vivo colonic propulsion was tested in wild-type and CB1−/−mice. Immunostaining with the cytoskeletal marker peripherin showed CB1immunoreactivity both on Dogiel type I and type II neurons. Further neurochemical characterization revealed CB1on choline acetyltransferase-, calretinin-, and 5-HT-immunopositive myenteric neurons, but nitrergic neurons appeared immunonegative for CB1immunostaining. Solitary spindle-shaped CB1-immunoreactive cells in between smooth muscle cells lacked specific markers for interstitial cells of Cajal or glial cells. ES elicited neuronally mediated excitatory JP (EJP) and inhibitory JP. Gradual increases in distance resulted in a wave-like EJP with EJP amplitudes being maximal at the location of stimulating electrode 6 and a maximal EJP projection distance of ∼18 mm. The CB1receptor agonist WIN 55,212-2 reduced the amplitude of EJP and was responsible for shortening the oral spreading of the excitatory impulse. In a partitioned chamber, WIN 55,212-2 reduced EJP at the separated oral sites, proving that CB1activation inhibits interneuron-mediated neurotransmission. These effects were absent in the presence of the CB1antagonist SR141716A, which, when given alone, had no effect. WIN 55,212-2 inhibited colonic propulsion in wild-type mice but not in SR141716A-pretreated wild-type or CB1−/−mice. Activation of the CB1receptor modulates excitatory cholinergic neurotransmission in mouse colon by reducing amplitude and spatial spreading of the ascending electrophysiological impulses. This effect on electrophysiological spreading involves CB1-mediated effects on motor neurons and ascending interneurons and is likely to underlie the here reported in vivo reduction in colonic propulsion.
Sex differences in limb vasoconstriction responses to increases in transmural pressures
Authors: Lott Mary E. J. , Hogeman Cindy , Herr Michael , Bhagat Monica , Sinoway Lawrence I.
Published: November 2008

Women compared with men are more likely to have orthostatic intolerance. The purpose of this study was to examine whether sex affects limb vasoconstrictor response to increases in transmural pressure. Brachial and femoral mean blood velocity (MBV) and diameter (Doppler Ultrasound) were measured in 10 women and 10 men as transmural pressure was altered by applying local suction (−25, −50, −75, and −100 mmHg) via pressurized-limb tanks for 1 min to a single arm and leg. With the abrupt application of forearm suction (−75 and −100 mmHg), women compared with men had a greater initial rise in MBV (peak), followed by a quicker dynamic rate of velocity reduction. In the leg, women had a tendency for higher peak MBV but had similar dynamic velocity reductions compared with men. After 60 s of suction, women compared with men had attenuated reductions in brachial flow and conductance (−8.05 ± 1.71 vs. −16.25 ± 1.71 ml/min; −0.12 ± 0.03 vs. −0.20 ± 0.03 ml·min−1·mmHg−1; main effect, P < 0.05), as well as attenuated femoral flow and conductance to sustained leg negative pressure at −100 mmHg ( P < 0.05). When the data were expressed as percent change, women compared with men continued to have attenuated brachial flow responses (−24 ± 2 vs. −36 ± 2%, main effect, P < 0.05), with a trend toward attenuation at the highest leg pressure (−25 ± 11 vs. −46 ± 4%; P = 0.08). These sex differences remained after normalizing the flow responses by limb volume (percent change). Our findings suggest that young women compared with men have attenuated brachial and femoral vasoconstrictor responses to increases in transmural pressure, which may have implications for the greater incidence of orthostatic intolerance in women.
Antiatherosclerotic effect of farnesoid X receptor
Authors: Mencarelli Andrea , Renga Barbara , Distrutti Eleonora , Fiorucci Stefano
Published: November 2008

The farnesoid X receptor (FXR) is a member of the nuclear receptor superfamily that functions as an endogenous sensor for bile acids and regulates cholesterol and fatty acid metabolism. The effect of FXR activation on aortic plaque formation was assessed by feeding apolipoprotein E-deficient (ApoE−/−) mice with the synthetic FXR ligand INT-747, a cheno-deoxycholic acid derivative, at doses of 3 and 10 mg·kg−1·day−1, or with rosiglitazone, a peroxisome proliferator-activated receptor-γ ligand, at the dose of 10 mg·kg−1·day−1 for 12 wk. Administration of INT-747 reduced formation of aortic plaque area by 95% ( P < 0.01), and a similar antiplaque activity was exerted by administration of rosiglitazone. INT-747 administration to ApoE−/− mice reduced aortic expression of IL-1β, IL-6, and CD11b mRNA, while it upregulated the expression of FXR and its target gene, the small heterodimer partner (SHP). FXR activation reduced the liver expression of sterol regulatory element binding protein 1c, resulting in reduced triglyceride and cholesterol content in the liver and amelioration of hyperlipidemia. FXR expression, mRNA and protein, was detected in human macrophages and macrophage cell lines. FXR activation by natural and synthetic ligands in these cell types attenuated IL-1β, IL-6, and TNF-α gene induction in response to Toll-like receptor 4 activation by LPS. Using spleen monocytes from wild-type and FXR−/− mice, we demonstrated that FXR gene ablation exacerbates IL-6 and TNF-α generation by LPS-stimulated macrophages. FXR was also able to reduce cholesterol uptake on macrophages by regulation of CD36 and ABCA1 expression. We found that FXR and SHP are expressed in the aorta and macrophages and that FXR ligands might have utility in prevention and treatment of atherosclerotic lesions.
cAMP Receptor Protein from Escherichia coli as a Model of Signal Transduction in Proteins – A Review
Authors: Fic E. , Bonarek P. , Gorecki A. , Kedracka-Krok S. , Mikolajczak J. , Polit A. , Tworzydlo M. , Dziedzicka-Wasylewska M. , Wasylewski Z.
Published: November 2008

In Escherichia coli, cyclic AMP receptor protein (CRP) is known to regulate the transcription of about 100 genes. The signal to activate CRP is the binding of cyclic AMP. It has been suggested that binding of cAMP to CRP leads to a long-distance signal transduction from the N-terminal cAMP-binding domain to the C-terminal domain of the protein, which is responsible for interaction with specific sequences of DNA. The signal transduction plays a crucial role in the activation of the protein. The most sophisticated spectroscopic techniques, other techniques frequently used in structural biochemistry, and site-directed mutagenesis have been used to investigate the details of cAMP-mediated allosteric control over CRP conformation and activity as a transcription factor. The aim of this review is to summarize recent works and developments pertaining to cAMP-dependent CRP signal transduction in E. coli.
N-Terminal Domain-Deleted Mu Transposase Exhibits Increased Transposition Activity with Low Target Site Preference in Modified Buffers
Authors: Kim Yun Cheol , Morrison Sherie L.
Published: November 2008

Background: Transposition using MuA and the Mu-transposon is frequently used for insertional and deletional mutagenesis and to introduce primer sequences into DNA of unknown sequence. However, mutagenesis studies are often limited by the number of transposition events taking place within a small target sequence. Although the intrinsic target site preference of MuA is low, it nevertheless may limit the recovery of desired events. Methods: In the current study, we have compared the transposition activity of wild-type, C-terminally deleted, N-terminally deleted and both C- and N-terminally deleted MuA. Results: We found that N-terminally deleted MuA was most active with an about sevenfold increase in transposition efficiency compared to wild-type. In addition, we identified a novel reaction condition in which the transposition activity of N-terminally deleted MuA was increased about 45-fold. Conclusion: The use of the N-terminally deleted MuA with the newly established condition enhanced the relative transposition activity about 280-fold compared to that of wild-type MuA with the conventional buffer. In addition, the optimized buffer decreased the target site preference of N-terminally deleted MuA resulting in a more even distribution of integration events throughout the target gene.
Effect of Mechanical Stimulation on Osteoblast- and Osteoclast-Like Cells in vitro
Authors: Kadow-Romacker A. , Hoffmann J.E. , Duda G. , Wildemann B. , Schmidmaier G.
Published: November 2008

Bone-forming osteoblasts and bone-resorbing osteoclasts play an important role during maintenance, adaptation and healing of bone, and both cell types are influenced by physical activity. The aim of the present study was to investigate the effect of a narrow mechanical stimulation window on osteoblast- and osteoclast-like cells. Primary human cells were cultured on a bone-like structure (dentine) and three-point bending with approximately 1,100 microstrain was applied to the dentine at varying frequencies (0.1 and 0.3 Hz) and duration (1, 3 and 5 min daily over 5 days) resulting in different patterns of mechanical stimulation of osteoblast- and osteoclast-like cells. The longest stimulation (5 min at 0.1 Hz) induced a significant increase in osteoblast alkaline phosphatase activity and a significant decrease in osteoprotegerin (OPG) production, and resulted in a significant increase in the soluble receptor activator of NF-κB ligand (sRANKL)/OPG ratio towards sRANKL in comparison to the unstimulated osteoblast-like cells. All stimulations caused a significant decrease in collagen type 1 synthesis. Stimulation for 1 min at 0.3 Hz decreased the fusion and resorption activity of the osteoclast-like cells. These results demonstrate a direct effect of mechanical stimuli on osteoblast-like cells as well as on osteoclast formation and activity in vitro. The change in the sRANKL/OPG ratio towards the stimulation of osteoclastogenesis stresses the necessity to investigate the effect of the same stimulation parameter on the co-culture of both cell types.
Low Oxygen Expansion Improves Subsequent Chondrogenesis of Ovine Bone-Marrow-Derived Mesenchymal Stem Cells in Collagen Type I Hydrogel
Authors: Zscharnack M. , Poesel C. , Galle J. , Bader A.
Published: November 2008

Background/Objective: A crucial factor when investigating cartilage tissue engineering using mesenchymal stem cells (MSCs) is their application in large-animal models and preclinical trials. However, in vitro studies using cells of these model organisms must proceed. Considering that oxygen tension is an important parameter for stem cell culture, we investigated the effect of low oxygen tension during the expansion of ovine MSCs on colony-forming unit-fibroblast (CFU-F) formation, senescence and subsequent chondrogenesis in pellet culture and a collagen I hydrogel which is in clinical use for matrix-associated autologous chondrocyte transplantation (MACT). Materials and Methods: Ovine MSCs were isolated from bone marrow aspirates and cultured at 5 and 20% O2 in monolayer. CFU-F formation was detected by Giemsa staining. Senescence was analyzed by detection of senescence-associated β-galactosidase and flow cytometry. Chondrogenic differentiation was carried out in pellet and collagen I hydrogel culture and assessed by gene expression, immunohistochemistry and measurement of sulfated glycosaminoglycans (sGAG). Results: MSCs expanded at 5% O2 revealed a 2-fold higher CFU-F potential and diminished senescence compared to those expanded at 20% O2. Most notably, our results show enhanced chondrogenic differentiation in both pellet culture and the MACT-approved collagen I hydrogel. Conclusion: The findings demonstrate that physiologically low oxygen tension during monolayer expansion of ovine MSCs is advantageous in order to improve cartilage tissue engineering in a sheep model. The ovine system is shown to represent an appropriate basis for large-animal studies and preclinical trials on MSC-based cartilage repair.
Risk and Protective Factors for Depressive Symptoms in Urban African American Adolescents
Authors: Tandon Darius S. , Solomon Barry S.
Published: November 2008

There is limited understanding of risk and protective factors associated with depression among African American adolescents living in impoverished, urban settings. A cross-sectional study was conducted to identify a range of risk and protective factors associated with depressive symptoms among low-income urban African American adolescents. The sample ( n = 467) comprised African American adolescents from three high-poverty urban neighborhoods in Baltimore, Maryland. A self-administered read aloud survey completed by adolescents assessed depressive symptoms as well as various individual- and environmental-level risk and protective factors. Multivariate analyses indicated that female gender, living with an adult with a substance abuse problem, greater exposure to physical violence, and greater peer delinquency were associated with higher depressive symptoms. Greater home assets and self-awareness were associated with lower depressive symptoms. Future interventions to prevent and treat depression among urban African American adolescents should focus on minimizing their risk factors while enhancing those factors found to be protective.
Strategies to Manage Gastrointestinal Symptoms Complicating Enteral Feeding
Authors: Barrett Jacqueline S. , Shepherd Susan J. , Gibson Peter R.
Published: November 2008

Diarrhea and abdominal distension are common complications associated with enteral feeding. Often the cause is unknown, the enteral formula is blamed and changes to the mode of delivery or formula are instituted. However, the evidence base for many strategies used is limited. Altering the osmolality and temperature of the formula and/or the rate of infusion are commonly practiced but evidence for their benefit is largely anecdotal. Preventing microbial contamination of the feed is important and clear guidelines exist to achieve this. The formulation itself can be modified. While the addition of fiber is well supported theoretically, outcome data are less convincing. Avoidance of osmotically active, poorly absorbed short‐chain carbohydrates in the formula (often used as the major carbohydrate source) is a new tactic to minimize diarrhea. It has compelling theoretical support, but requires further investigation. A methodical clinical approach to gastrointestinal complications of enteral feeding is warranted and an algorithm for management is proposed.
Moderating and Mediating Roles of Nurses' Beliefs
Authors: Abdrbo Amany A. , Hudak Christine A. , Anthony Mary K. , Douglas Sara L.
Published: November 2008

Health care is rapidly increasing the types of information systems (IS) that are used to manage patient care. The extent to which nurses move to a paperless system will be contingent on their beliefs about IS. The study explores the moderating and mediating effects of nurses' beliefs about IS use on the relationship between IS use and perceived benefits and satisfaction. A descriptive, correlational, cross-sectional design is used, and a random sample of 201 staff nurses working in hospitals was surveyed via a mail questionnaire. Nurses' beliefs have mediating effects on the relationship between nurses' IS use and their perceptions of IS benefits and satisfaction. The results can guide nurse administrators to improve nurses' perceptions about IS by using such methods as providing a training program to increase nurses' computer self-efficacy. Enhancing nurses' use of IS and their perceptions of IS benefits can ultimately improve patient safety and outcomes.
Psychomotor and cognitive effects of a single oral dose of talnetant (SB223412) in healthy volunteers compared with placebo or haloperidol
Authors: Liem-Moolenaar M. , Gray FA , de Visser SJ , Franson KL , Schoemaker RC , Schmitt JAJ , Cohen AF , van Gerven JMA
Published: November 2008

Central Nervous System (CNS) effects of talnetant, an NK-3 antagonist in development for schizophrenia, were compared to those of haloperidol and placebo. The study was randomised, double-blind, three-way crossover of talnetant 200 mg, haloperidol 3 mg or placebo. Twelve healthy males participated and EEG, saccadic and smooth pursuit eye movements, adaptive tracking, body sway, finger tapping, hormones, visual analogue scales (VAS) for alertness, mood and calmness and psychedelic effects, left/right distraction task, Tower of London and Visual and Verbal Learning Task were assessed. Haloperidol showed (difference to placebo; 95% CI; p-value) decreases in EEG α power (−0.87μV; −1.51/−0.22; p = 0.0110), saccadic inaccuracy (2.0%; 0.5/3.6; p = 0.0133), smooth pursuit eye movements (−7.5%; −12.0/−3.0; p = 0.0026), adaptive tracking (−3.5%; −5.4/−1.7; p = 0.0009), alertness (−6.8 mm; −11.1/−2.4; p = 0.0039), negative mood (−4.6 mm; −8.6/−0.6; p = 0.0266), the ability to control thoughts (1.2 mm; 0.2/2.3; p = 0.0214), and an increase of serum prolactin (ratio 4.1; 3.0/5.6; p < 0.0001). Talnetant showed decreased alpha power (−0.69 μV; −1.34/−0.04; p = 0.0390), improved adaptive tracking (1.9%; 0.1/3.7; p = 0.0370) and reduced calmness on VAS Bond and Lader (−4.5 mm; −8.0/−1.0; p = 0.0151). Haloperidol effects were predominantly CNS-depressant, while those of talnetant were slightly stimulatory. The results suggest that talnetant penetrates the brain, but it remains to be established whether this dose is sufficient and whether the observed effect profile is class-specific for NK3-antagonists.
The effects of sibutramine on the microstructure of eating behaviour and energy expenditure in obese women
Authors: Halford JCG , Boyland EJ , Cooper SJ , Dovey TM , Huda MSB , Dourish CT , Dawson GR , Wilding JPH
Published: November 2008

Given the suggestion that many potential anti-obesity drugs may enhance within-meal satiation, few studies have directly measured the effects of any drug on the microstructure of human eating behaviour. The effects of 7 days dosing with sibutramine 10 mg and 15 mg a day on appetite and energy balance were determined in 30 obese women (BMI 34.6 ± 3.3 kg/m2, age 46.0 ± 12.9 years) using a Universal Eating Monitor (UEM) and indirect calorimetry, in a double-blind, placebo-controlled crossover study. At day 7, sibutramine 10 mg and 15 mg reduced food intake by 16.6% and 22.3%, respectively (p < 0.001), compared with placebo. Sibutramine reduced eating rate compared with placebo rather than meal length (10 mg p < 0.05; 15 mg p < 0.001). In addition, sibutramine 10 mg significantly reduced hunger later in the meal (p < 0.05) and sibutramine 15 mg increased fullness early in the meal (p < 0.01), both of which are consistent with enhanced within-meal satiation. Sibutramine had little effect on resting metabolic rate, although 15 mg did significantly reduce respiratory quotient at several time points during the test day. These results provide novel evidence that decreased consumption of a test meal induced by sibutramine is primarily because of reduced eating rate, enhancing the deceleration in cumulative food intake within a meal associated with the development of satiety. Changes in within-meal appetite ratings appear particularly sensitive to drug-induced enhancement of satiation, and may provide key indices for assessing the therapeutic potential of novel anti-obesity drugs.
Effects of quetiapine, risperidone, 9-hydroxyrisperidone and ziprasidone on the survival of human neuronal and immune cells in vitro
Authors: Schmidt AJ , Krieg JC , Clement HW , Hemmeter UM , Schulz E. , Vedder H. , Heiser P.
Published: November 2008

Because there are reports on cytotoxic and cytoprotective effects of antipsychotics, the aim of the present study was to evaluate the impacts of different concentrations (1.6—50 μg/mL) of atypical antipsychotics on the survival of human neuronal (neuroblastoma SH-SY5Y) and immune (monocytic U-937) cells and on energy metabolism (ATP level after the incubation with antipsychotics in the concentration of 25 μg/mL). Statistical analysis showed that incubation for 24 h with the antipsychotics quetiapine, risperidone, 9-hydroxyrisperidone and ziprasidone led to a significantly enhanced cell survival in both cell lines in the lower concentrations. Higher concentrations exerted in part cytotoxic effects with the exception of quetiapine, but therapeutically relevant concentrations of the drugs were not cytotoxic in our experiments. Measurement of ATP contents in the neuronal cell line showed significantly increased levels after a 24-h treatment with 25 μg/mL risperidone and 9-hydroxyrisperidone. The other substances produced no effects. Our results show that the antipsychotic substances under investigation exert concentration-dependent effects on cell survival in both cell lines examined.
Ethanol-like effects of thiopental and ketamine in healthy humans
Authors: Dickerson D. , Pittman B. , Ralevski E. , Perrino A. , Limoncelli D. , Edgecombe J. , Acampora G. , Krystal JH , Petrakis I.
Published: November 2008

The γ-aminobutyric acid-A (GABAA) and N-methyl-D-aspartate (NMDA) receptors mediate aspects of the behavioural effects of alcohol. Prior studies reported drugs that block NMDA receptors or facilitate GABAAreceptor function produce ethanol-like effects in humans. The purpose of this study was to compare the ethanol-related effects of two pharmacological agents with known NMDA and GABAAreceptor activity. As part of an ongoing, larger study, 28 subjects (age, 21—30) with no personal or family histories of alcoholism were administered subanesthetic doses of the GABAAreceptor agonist thiopental, the NMDA receptor antagonist, ketamine and placebo on three separate test days. Various ethanol-related measures were administered. At doses of thiopental and ketamine that produced similar levels of sedation and cognitive effects, both agents produced significant ethanol-like effects and subjective intoxication. However, the intensity of the ethanol-like effects of ketamine was greater than that of thiopental. In addition, ketamine produced alterations in perception that were not produced by thiopental. These data provide further support for a model where GABAAreceptor facilitation may contribute significantly to ethanol effects associated with social drinking, whereas NMDA receptor antagonism may contribute to relatively greater extent to features of ethanol ‘intoxication’.