bluuebunny/crossref_metadata_2025 huggingface dataset:
Conditional targeting of E-cadherin in skin: Insights into hyperproliferative and degenerative responses
Authors: Tinkle Christopher L. , Lechler Terry , Pasolli H. Amalia , Fuchs Elaine
Published: January 2004

Loss of E-cadherin has been associated with human cancers, and yet in the early mouse embryo and the lactating mammary gland, the E-cadherin null state results in tissue dysfunction and cell death. Here we targeted loss of E-cadherin in skin epithelium. The epidermal basal layer responded by elevating P-cadherin, enabling these cells to maintain adherens junctions. Suprabasal layers upregulated desmosomal cadherins, but without classical cadherins, terminal differentiation was impaired. Progressive hyperplasia developed with age, a possible consequence of proliferative maintenance in basal cells coupled with defects in terminal differentiation. In contrast, hair follicles lost integrity of the inner root sheath and hair cuticle without apparent elevation of cadherins. These findings suggest that, if no compensatory mechanisms exist, E-cadherin loss may be incompatible with epithelial tissue survival, whereas partial compensation can result in alterations in differentiation and proliferation.
Response of C
3
and C
4
plants to middle-Holocene climatic variation near the prairie–forest ecotone of Minnesota
Authors: Nelson David M. , Hu Feng Sheng , Tian Jian , Stefanova Ivanka , Brown Thomas A.
Published: January 2004

Paleorecords of the middle Holocene (MH) from the North American mid-continent can offer insights into ecological responses to pervasive drought that may accompany future climatic warming. We analyzed MH sediments from West Olaf Lake (WOL) and Steel Lake (SL) in Minnesota to examine the effects of warm/dry climatic conditions on prairie–woodland ecosystems. Mineral composition and carbonate δ
18
O were used to determine climatic variations, whereas pollen assemblages, charcoal δ
13
C, and charcoal accumulation rates were used to reconstruct vegetation composition, C
3
and C
4
plant abundance, and fire. The ratio of aragonite/calcite at WOL and δ
18
O at SL suggest that pronounced droughts occurred during the MH but that drought severity decreased with time. From charcoal δ
13
C data we estimated that the MH abundance of C
4
plants averaged 50% at WOL and 43% at SL. At WOL C
4
abundance was negatively correlated with aragonite/calcite, suggesting that severe moisture deficits suppressed C
4
plants in favor of weedy C
3
plants (e.g.,
Ambrosia
). As climate ameliorated C
4
abundance increased (from ≈33 to 66%) at the expense of weedy species, enhancing fuel availability and fire occurrence. In contrast, farther east at SL where climate was cooler and wetter, C
4
abundance showed no correlation with δ
18
O-inferred aridity. Woody C
3
plants (e.g.,
Quercus
) were more abundant, biomass flammability was lower, and fires were less important at SL than at WOL. Our results suggest that C
4
plants are adapted to warm/dry climatic conditions, but not to extreme droughts, and that the fire regime is controlled by biomass–climate interactions.
JNK-mediated induction of cyclooxygenase 2 is required for neurodegeneration in a mouse model of Parkinson's disease
Authors: Hunot Stéphane , Vila Miquel , Teismann Peter , Davis Roger J. , Hirsch Etienne C. , Przedborski Serge , Rakic Pasko , Flavell Richard A.
Published: January 2004

Parkinson's disease (PD) is a neurodegenerative disorder characterized by loss of dopamine-containing neurons, but the molecular pathways underlying its pathogenesis remain uncertain. Here, we show that by eliminating c-Jun N-terminal kinases (JNKs) we can prevent neurodegeneration and improve motor function in an animal model of PD. First, we found that c-Jun is activated in dopaminergic neurons from PD patients and in the 1-methyl-4-phenyl-1,2,4,6-tetrahydropyridine (MPTP) mouse model of PD. Examination of various JNK-deficient mice shows that both JNK2 and JNK3, but not JNK1, are required for MPTP-induced c-Jun activation and dopaminergic cell demise. Furthermore, we have identified cyclooxygenase (COX) 2 as a molecular target of JNK activation and demonstrated that COX-2 is indispensable for MPTP-induced dopaminergic cell death. Our data revealed that JNK2- and JNK3-induced COX-2 may be a principle pathway responsible for neurodegeneration in PD.
Increased lactate/pyruvate ratio augments blood flow in physiologically activated human brain
Authors: Mintun Mark A. , Vlassenko Andrei G. , Rundle Melissa M. , Raichle Marcus E.
Published: January 2004

The factors regulating cerebral blood flow (CBF) changes in physiological activation remain the subject of great interest and debate. Recent experimental studies suggest that an increase in cytosolic NADH mediates increased blood flow in the working brain. Lactate injection should elevate NADH levels by increasing the lactate/pyruvate ratio, which is in near equilibrium with the NADH/NAD
+
ratio. We studied CBF responses to bolus lactate injection at rest and in visual stimulation by using positron-emission tomography in seven healthy volunteers. Bolus lactate injection augmented the CBF response to visual stimulation by 38–53% in regions of the visual cortex but had no effect on the resting CBF or the whole-brain CBF. These lactate-induced CBF increases correlated with elevations in plasma lactate/pyruvate ratios and in plasma lactate levels but not with plasma pyruvate levels. Our observations support the hypothesis that an increase in the NADH/NAD
+
ratio activates signaling pathways to selectively increase CBF in the physiologically stimulated brain regions.
NADH augments blood flow in physiologically activated retina and visual cortex
Authors: Ido Yasuo , Chang Katherine , Williamson Joseph R.
Published: January 2004

The mechanism(s) that increase retinal and visual cortex blood flows in response to visual stimulation are poorly understood. We tested the hypothesis that increased transfer of electrons and protons from glucose to cytosolic free NAD
+
, reducing it to NADH, evoked by increased energy metabolism, fuels redox-signaling pathways that augment flow. The near-equilibrium between free cytosolic NADH/NAD
+
and lactate/pyruvate ratios established by lactate dehydrogenase predicts that transfer of additional electrons and protons from injected lactate to NAD
+
will augment the elevated blood flows in stimulated retina and cortex, whereas transfer of electrons and protons from NADH to injected pyruvate will attenuate the elevated flows. These predictions were tested and confirmed in rats. Increased flows evoked by stimulation also were prevented by inhibition of nitric oxide synthase. These findings support an important role for cytosolic free NADH in fueling a signaling cascade that increases
•
NO production, which augments blood flow in photostimulated retina and visual cortex.
Analysis of C5a-mediated chemotaxis by lentiviral delivery of small interfering RNA
Authors: Hwang Jong-Ik , Fraser Iain D. C. , Choi Sangdun , Qin Xiao-Feng , Simon Melvin I.
Published: January 2004

Immune cells respond to chemotactic signals by means of G protein-coupled receptors. Attempts to elucidate the function of specific G protein family members in these responses is complicated by redundancy among the different G protein isoforms. We have used lentiviral-based RNA interference to eliminate expression of specific G protein subunits selectively in J774A.1 mouse macrophages. The chemotactic response to the complement factors C5a and C3a is ablated in cells lacking Gβ2but is unaffected in cells lacking Gβ1, Gαi2, or Gαi3. Similarly, the C5a-mediated calcium response of single cells is either absent or significantly delayed and weakened by Gβ2knockdown. Assessment of Akt1 phosphorylation levels in response to C5a shows rapid and sustained phosphorylation in both wild-type cells and cells lacking Gβ1. Cells lacking Gβ2retain the rapid response but cannot sustain phospho-Akt1 levels. The phenotype of cells lacking Gβ2can be reversed by overexpression of either human Gβ2or mouse Gβ1. These data demonstrate the usefulness of lentiviral-based RNA interference in the systematic analysis of a signaling pathway, and they suggest that in J774A.1 cells, Gβ2-derived Gβγ is the most effective mediator of chemotaxis to C5a.
Functional expression in frog oocytes of human ρ1 receptors produced inSaccharomyces cerevisiae
Authors: Martínez-Martínez Alejandro , Reyes-Ruiz Jorge Mauricio , Martínez-Torres Ataúlfo , Miledi Ricardo
Published: January 2004

The yeastSaccharomyces cerevisiaewas engineered to express the ρ1 subunit of the human γ-aminobutyric acid ρ1 (GABAρ1) receptor. RNA that was isolated from several transformed yeast strains produced fully functional GABA receptors inXenopusoocytes. The GABA currents elicited in the oocytes were fast, nondesensitizing chloride currents; and the order of agonist potency was GABA > β-alanine > glycine. Moreover, the receptors were resistant to bicuculline, strongly antagonized by (1,2,5,6 tetrahydropyridine-4-yl)methylphosphinic acid, and modulated by zinc and lanthanum. Thus, the GABA receptors expressed by the yeast mRNA retained all of the principal characteristics of receptors expressed by cRNA or native retina mRNAs. Western blot assays showed immunoreactivity in yeast plasma membrane preparations, and a ρ1-GFP fusion gene showed mostly intracellular distribution with a faint fluorescence toward the plasma membrane.In situimmunodetection of ρ1 in yeast demonstrated that some receptors reach the plasma membrane. Furthermore, microtransplantation of yeast plasma membranes to frog oocytes resulted in the incorporation of a small number of functional yeast ρ1 receptors into the oocyte plasma membrane. These results show that yeast may be useful to produce complete functional ionotropic receptors suitable for structural analysis.
Association of β-catenin with the α-subunit of neuronal large-conductance Ca
2+
-activated K+ channels
Authors: Lesage F. , Hibino H. , Hudspeth A. J.
Published: January 2004

The association of Ca
2+
-activated K
+
channels with voltage-gated Ca
2+
channels at the presynaptic active zones of hair cells, photoreceptors, and neurons contributes to rapid repolarization of the membrane after excitation. Ca
2+
channels have been shown to bind to a large set of synaptic proteins, but the proteins interacting with Ca
2+
-activated K
+
channels remain unknown. Here, we report that the large-conductance Ca
2+
-activated K
+
channel of the chicken's cochlear hair cell interacts with β-catenin. Yeast two-hybrid assays identified the S10 region of the K
+
channel's α-subunit and the ninth armadillo repeat and carboxyl terminus of β-catenin as necessary for the interaction. An antiserum directed against the α-subunit specifically coprecipitated β-catenin from brain synaptic proteins. β-Catenin is known to associate with the synaptic protein Lin7/Velis/MALS, whose interaction partner Lin2/CASK also binds voltage-gated Ca
2+
channels. β-Catenin may therefore provide a physical link between the two types of channels at the presynaptic active zone.
RF2b, a rice bZIP transcription activator, interacts with RF2a and is involved in symptom development of rice tungro disease
Authors: Dai Shunhong , Zhang Zhihong , Chen Shouyi , Beachy Roger N.
Published: January 2004

The phloem-specific promoter of rice tungro bacilliform virus (RTBV) is regulated in part by sequence-specific DNA-binding proteins that bind to Box II, an essential
cis
element. Previous studies demonstrated that the bZIP protein RF2a is involved in transcriptional regulation of the RTBV promoter. Here we report the identification and functional characterization of a second bZIP protein, RF2b. RF2b, identified by its interaction with RF2a, binds to Box II in
in vitro
assays as a homodimer and as RF2a/RF2b heterodimers. Like RF2a, RF2b activates the RTBV promoter in transient assays and in transgenic tobacco plants. Both RF2a and RF2b are predominantly expressed in vascular tissues. However, RF2a and RF2b have different DNA-binding affinities to Box II, show distinctive expression patterns in different rice organs, and exhibit different patterns of subcellular localization. Furthermore, transgenic rice plants with reduced levels of RF2b exhibit a disease-like phenotype. We propose that the regulation of phloem-specific expression of the RTBV promoter and potentially the control of RTBV replication are mainly achieved via interactions of the Box II
cis
element with multiple host factors, including RF2a and RF2b. We also propose that quenching/titration of these and perhaps other transcription factors by RTBV is involved in the development of the symptoms of rice tungro disease.
Binding of mouse VL30 retrotransposon RNA to PSF protein induces genes repressed by PSF: Effects on steroidogenesis and oncogenesis
Authors: Song Xu , Sui Aiwei , Garen Alan
Published: January 2004

We describe a mechanism of gene regulation involving formation of a complex between PSF protein and mouse VL30 (mVL30) retrotransposon RNA. PSF represses transcription of the insulin-like growth factor 1 (IGF1)-inducible gene P450scc by binding to an insulin-like growth factor response element (IGFRE) motif in the gene. The complex with mVL30 RNA releases PSF, allowing transcription to proceed. Retrovirally mediated transmission of mVL30 RNA to human tumor cells induced several genes, including oncogenes, which also are induced by IGF1, and promoted metastasis. In mice, steroid synthesis is activated in steroidogenic cells by pituitary hormones, which concomitantly induce transcription of mVL30 RNA in the cells. We showed that steroid synthesis could also be activated in mouse steroidogenic adrenal cells by transfection with cDNA encoding either mVL30 RNA tracts that form a complex with PSF or a small interfering RNA (siRNA) that degrades PSF transcripts. These results suggest that mVL30 RNA regulates steroidogenesis, and possibly other physiological processes of mice, by complex formation with PSF. Retrotransposons such as mVL30 apparently evolved not only as “junk” DNA but also as transcriptionally active noncoding DNA that acquired physiological and pathological functions.
Regulation of synaptojanin 1 by cyclin-dependent kinase 5 at synapses
Authors: Lee Sang Yoon , Wenk Markus R. , Kim Yong , Nairn Angus C. , De Camilli Pietro
Published: January 2004

Synaptojanin 1 is a polyphosphoinositide phosphatase concentrated in presynaptic nerve terminals, where it dephosphorylates a pool of phosphatidylinositol 4,5-bisphosphate implicated in synaptic vesicle recycling. Like other proteins with a role in endocytosis, synaptojanin 1 undergoes constitutive phosphorylation in resting synapses and stimulation-dependent dephosphorylation by calcineurin. Here, we show that cyclin-dependent kinase 5 (Cdk5) phosphorylates synaptojanin 1 and regulates its function bothin vitroand in intact synaptosomes. Cdk5 phosphorylation inhibited the inositol 5-phosphatase activity of synaptojanin 1, whereas dephosphorylation by calcineurin stimulated such activity. The activity of synaptojanin 1 was also stimulated by its interaction with endophilin 1, its major binding partner at the synapse. Notably, Cdk5 phosphorylated serine 1144, which is adjacent to the endophilin binding site. Mutation of serine 1144 to aspartic acid to mimic phosphorylation by Cdk5 inhibited the interaction of synaptojanin 1 with endophilin 1. These results suggest that Cdk5 and calcineurin may have an antagonistic role in the regulation of synaptojanin 1 recruitment and activity, and therefore in the regulation of phosphatidylinositol 4,5-bisphosphate turnover at synapses.
Soot climate forcing via snow and ice albedos
Authors: Hansen James , Nazarenko Larissa
Published: January 2004

Plausible estimates for the effect of soot on snow and ice albedos (1.5% in the Arctic and 3% in Northern Hemisphere land areas) yield a climate forcing of +0.3 W/m2in the Northern Hemisphere. The “efficacy” of this forcing is ∼2, i.e., for a given forcing it is twice as effective as CO2in altering global surface air temperature. This indirect soot forcing may have contributed to global warming of the past century, including the trend toward early springs in the Northern Hemisphere, thinning Arctic sea ice, and melting land ice and permafrost. If, as we suggest, melting ice and sea level rise define the level of dangerous anthropogenic interference with the climate system, then reducing soot emissions, thus restoring snow albedos to pristine high values, would have the double benefit of reducing global warming and raising the global temperature level at which dangerous anthropogenic interference occurs. However, soot contributions to climate change do not alter the conclusion that anthropogenic greenhouse gases have been the main cause of recent global warming and will be the predominant climate forcing in the future.
Defective lysosomal targeting of activated fibroblast growth factor receptor 3 in achondroplasia
Authors: Cho Jay Y. , Guo Changsheng , Torello Monica , Lunstrum Gregory P. , Iwata Tomoko , Deng Chuxia , Horton William A.
Published: January 2004

Mutations of fibroblast growth factor receptor 3 (FGFR3) are responsible for achondroplasia (ACH) and related dwarfing conditions in humans. The pathogenesis involves constitutive activation of FGFR3, which inhibits proliferation and differentiation of growth plate chondrocytes. Here we report that activating mutations in FGFR3 increase the stability of the receptor. Our results suggest that the mutations disrupt c-Cbl-mediated ubiquitination that serves as a targeting signal for lysosomal degradation and termination of receptor signaling. The defect allows diversion of actively signaling receptors from lysosomes to a recycling pathway where their survival is prolonged, and, as a result, their signaling capacity is increased. The lysosomal targeting defect is additive to other mechanisms proposed to explain the pathogenesis of ACH.
Availability of specific reductases controls the temporal activity of the cytochrome P450 complement of
Streptomyces coelicolor
A3(2)
Authors: Lei Li , Waterman Michael R. , Fulco Armand J. , Kelly Steven L. , Lamb David C.
Published: January 2004

The annotated genome of
Streptomyces coelicolor
A3(2) revealed 18 cytosolic cytochromes P450 (CYPs) with six ferredoxin (fdx) proteins and two soluble ferredoxin reductases (fpr), their putative electron transport proteins. mRNA expression was observed for all 18 CYPs throughout growth and secondary metabolism, from 3 h after spore germination, and all CYP proteins examined also were present. Expression of members of the fdx complement was detected from the same time point, yet both fpr were detected only at 12 h. Six-hour exposure to dimethylbenzanthracene and benzo[
a
]pyrene xenobiotics resulted in the absence of some CYP mRNAs and expression of a specific fpr, FR2. This finding and the expression pattern during growth suggested that CYP activity may be regulated by availability of specific reductases. To test this proposal, we expressed in
Escherichia coli
and purified to homogeneity five CYPs: CYP105D5 (involved in xenobiotic metabolism) and CYP154A1, CYP154C1, CYP158A1, and CYP158A2 (putatively involved in secondary metabolism). Also the two soluble fpr (FR2 and FR3) proposed to shuttle electrons by means of fdx were purified, and specific interactions were observed so that FR2 preferentially reduced CYP105D5 (>90% reduction) compared with the other CYPs (>20% reduction), whereas FR3 preferentially reduced the other CYPs (>85% reduction) compared with CYP105D5 (>10%). Furthermore FR2 was shown to efficiently bind CYP105D5 and drive benzo[
a
]pyrene hydroxylation in contrast to FR3. These data show that control of CYP activity in
S. coelicolor
A3(2) involves specific interactions with fpr and their availability during the life cycle and, after xenobiotic exposure, represents a unique mechanism for regulating CYP function.
The origin of vibrational mode couplings in various secondary structural motifs of polypeptides
Authors: Moran Andrew , Mukamel Shaul
Published: January 2004

Electrostatic (through-space) and covalent (through-bond) contributions to couplings involving the C

O and C—N vibrational stretching modes of the amide group in the α-helix and the parallel and antiparallel β-sheet structures of alanine polypeptides are analyzed. Coupling constants computed at the density functional theory level are compared with the transition dipole coupling model and the complete electrostatic interaction between transition densities. We find that the transition densities of C

O modes are localized, and the electrostatic mechanism then holds. In contrast, the C—N mode transition densities are delocalized, and covalent contributions to the coupling are significant.
Bacillus subtilisRecU protein cleaves Holliday junctions and anneals single-stranded DNA
Authors: Ayora Silvia , Carrasco Begoña , Doncel Ernesto , Lurz Rudi , Alonso Juan C.
Published: January 2004

Bacillus subtilisRecU protein is involved in homologous recombination, DNA repair, and chromosome segregation. Purified RecU binds preferentially to three- and four-strand junctions when compared to single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) (≈10- and ≈40-fold lower efficiency, respectively). RecU cleaves mobile four-way junctions but fails to cleave a linear dsDNA with a putative cognate site, a finding consistent with a similar genetic defect observed for genes classified within the ε epistatic group (namelyruvA,recD, andrecU). In the presence of Mg2+, RecU also anneals a circular ssDNA and a homologous linear dsDNA with a ssDNA tail and a linear ssDNA and a homologous supercoiled dsDNA substrate. These results suggest that RecU, which cleaves recombination intermediates with high specificity, might also help in their assembly.
Protein topology determines binding mechanism
Authors: Levy Yaakov , Wolynes Peter G. , Onuchic José N.
Published: January 2004

Protein recognition and binding, which result in either transient or long-lived complexes, play a fundamental role in many biological functions, but sometimes also result in pathologic aggregates. We use a simplified simulation model to survey a range of systems where two highly flexible protein chains form a homodimer. In all cases, this model, which corresponds to a perfectly funneled energy landscape for folding and binding, reproduces the macroscopic experimental observations on whether folding and binding are coupled in one step or whether intermediates occur. Owing to the minimal frustration principle, we find that, as in the case of protein folding, the native topology is the major factor that governs the choice of binding mechanism. Even when the monomer is stable on its own, binding sometimes occurs fastest through unfolded intermediates, thus showing the speedup envisioned in the fly-casting scenario for molecular recognition.
Transcriptional signature of histone deacetylase inhibition in multiple myeloma: Biological and clinical implications
Authors: Mitsiades Constantine S. , Mitsiades Nicholas S. , McMullan Ciaran J. , Poulaki Vassiliki , Shringarpure Reshma , Hideshima Teru , Akiyama Masaharu , Chauhan Dharminder , Munshi Nikhil , Gu Xuesong , Bailey Charles , Joseph Marie , Libermann Towia A. , Richon Victoria M. , Marks Paul A. , Anderson Kenneth C.
Published: January 2004

Histone deacetylases (HDACs) affect cell growth at the transcriptional level by regulating the acetylation status of nucleosomal histones. HDAC inhibition induces differentiation and/or apoptosis in transformed cells. We recently showed that HDAC inhibitors, such as suberoylanilide hydroxamic acid (SAHA), potently induce apoptosis of human multiple myeloma (MM) cells. In this study, we focused on MM as a model to study the transcriptional profile of HDAC inhibitor treatment on tumor cells and to address their pathophysiological implications with confirmatory mechanistic and functional assays. We found that MM cells are irreversibly committed to cell death within few hours of incubation with SAHA. The molecular profile of MM cells before their commitment to SAHA-induced cell death is hallmarked by a constellation of antiproliferative and/or proapoptotic molecular events, including down-regulation of transcripts for members of the insulin-like growth factor (IGF)/IGF-1 receptor (IGF-1R) and IL-6 receptor (IL-6R) signaling cascades, antiapoptotic molecules (e.g., caspase inhibitors), oncogenic kinases, DNA synthesis/repair enzymes, and transcription factors (e.g., XBP-1, E2F-1) implicated in MM pathophysiology. Importantly, SAHA treatment suppresses the activity of the proteasome and expression of its subunits, and enhances MM cell sensitivity to proteasome inhibition by bortezomib (PS-341). SAHA also enhances the anti-MM activity of other proapoptotic agents, including dexamethasone, cytotoxic chemotherapy, and thalidomide analogs. These findings highlight the pleiotropic antitumor effects of HDAC inhibition, and provide the framework for future clinical applications of SAHA to improve patient outcome in MM.
Directed evolution of mammalian paraoxonases PON1 and PON3 for bacterial expression and catalytic specialization
Authors: Aharoni Amir , Gaidukov Leonid , Yagur Shai , Toker Lilly , Silman Israel , Tawfik Dan S.
Published: January 2004

Serum paraoxonases (PONs) are a group of enzymes that play a key role in organophosphate (OP) detoxification and in prevention of atherosclerosis. However, their structure and mechanism of action are poorly understood. PONs seem like jacks-of-all-trades, acting on a very wide range of substrates, most of which are of no physiological relevance. Family shuffling and screening lead to the first PON variants that express in a soluble and active form in
Escherichia coli
. We describe variants with kinetic parameters similar to those reported for PONs purified from sera and others that show dramatically increased activities. In particular, we have evolved PON1 variants with OP-hydrolyzing activities 40-fold higher than wild type and a specificity switch of >2,000-fold, producing PONs specialized for OP rather than ester hydrolysis. Analysis of the newly evolved variants provides insights into the evolutionary relationships between different family members.
Single-molecule studies highlight conformational heterogeneity in the early folding steps of a large ribozyme
Authors: Xie Zheng , Srividya Narayanan , Sosnick Tobin R. , Pan Tao , Scherer Norbert F.
Published: January 2004

The equilibrium folding of the catalytic domain of
Bacillus subtilis
RNase P RNA is investigated by single-molecule fluorescence resonance energy transfer (FRET). Previous ensemble studies of this 255-nucleotide ribozyme described the equilibrium folding with two transitions, U-to-I
eq
-to-N, and focused on the I
eq
-to-N transition. The present study focuses on the U-to-I
eq
transition. Comparative ensemble measurements of the ribozyme construct labeled with fluorescein at the 5′ end and Cy3 at the 3′ end show that modifications required for labeling do not interfere with folding and help to define the Mg
2+
concentration range for the U-to-I
eq
transition. Histogram analysis of the Mg
2+
-dependent single-molecule FRET efficiency reveals two previously undetermined folding intermediates. The single-molecule FRET trajectories exhibit non-two-state and nonergodic behaviors at intermediate Mg
2+
concentrations on the time scale of seconds. The trajectories at intermediate Mg
2+
concentrations are classified into five classes based on three FRET levels and their dynamics of interconversion within the measured time range. This heterogeneity, together with the observation of “nonsudden jump” FRET transitions, indicates that the early folding steps of this ribozyme involve a series of intermediates with different degrees of kinetic isolation and that folding occurs under kinetic control and involves many “local” conformational switches. A free energy contour is constructed to illustrate the complex folding surface.
Efficacy of mosquito nets treated with insecticide mixtures or mosaics against insecticide resistant Anopheles gambiae and Culex quinquefasciatus (Diptera: Culicidae) in Côte d'Ivoire
Authors: Hougard J.-M. , Corbel V. , N'Guessan R. , Darriet F. , Chandre F. , Akogbéto M. , Baldet T. , Guillet P. , Carnevale P. , Traoré-Lamizana M.
Published: January 2004

Only pyrethroid insecticides have so far been recommended for the treatment of mosquito nets for malaria control. Increasing resistance of malaria vectors to pyrethroids threatens to reduce the potency of this important method of vector control. Among the strategies proposed for resistance management is to use a pyrethroid and a non-pyrethroid insecticide in combination on the same mosquito net, either separately or as a mixture. Mixtures are particularly promising if there is potentiation between the two insecticides as this would make it possible to lower the dosage of each, as has been demonstrated under laboratory conditions for a mixture of bifenthrin (pyrethroid) and carbosulfan (carbamate). The effect of these types of treatment were compared in experimental huts on wild populations of Anopheles gambiae Giles and the nuisance mosquito Culex quinquefasciatus Say, both of which are multi-resistant. Four treatments were evaluated in experimental huts over six months: the recommended dosage of 50 mg m−2 bifenthrin, 300 mg m−2 carbosulfan, a mosaic of 300 mg m−2 carbosulfan on the ceiling and 50 mg m−2 bifenthrin on the sides, and a mixture of 6.25 mg m−2 carbosulfan and 25 mg m−2 bifenthrin. The mixture and mosaic treatments did not differ significantly in effectiveness from carbosulfan and bifenthrin alone against anophelines in terms of deterrency, induced exophily, blood feeding inhibition and overall mortality, but were more effective than in earlier tests with deltamethrin. These results are considered encouraging, as the combination of different classes of insecticides might be a potential tool for resistance management. The mixture might have an advantage in terms of lower cost and toxicity.
Distribution, host range, and climatic constraints on Centistes gasseni (Hymenoptera: Braconidae), a South American parasitoid of cucumber beetles, Diabrotica spp. (Coleoptera: Chrysomelidae)
Authors: Walsh G. Cabrera , Athanas M.M. , Salles L.A.B. , Schroder R.F.W.
Published: January 2004

The genus Diabrotica includes a large number of pest species, including some of the most important crop pests of the Americas. The parasitoid Centistes gasseni Shaw is the first braconid to be described parasitizing Diabrotica in South America, and high natural infestations are reported. Field and experimental observations on the host range, distribution and biology of this parasitoid are described. Centistes gasseni was collected in southern Brazil, eastern Paraguay and northeastern Argentina, in a region comprising humid lowlands and highlands, and cool temperate to warm subtropical climates, with regular rainfall in excess of 1300 mm. Three Diabrotica species, D. limitata (Sahlberg), D. speciosa (Germar) and D. viridula (Fabricius) were found to host the parasitoid, with mean percent parasitism of 5.4, 2.0 and 1.0%, respectively. Diabrotica speciosa and D. viridula are the two most important pest Diabrotica species in South America. Laboratory experiments with field-collected beetles and parasitoid cocoons indicated that C. gasseni overwinters in adult host beetles, remaining dormant in its live host below developmental temperatures. A potential distribution of C. gasseni in North America is proposed based on its known climatic range and the distribution of the main pest species of adult overwintering North American Diabrotica.
Basic biology and small-scale rearing ofCelatoria compressa(Diptera: Tachinidae), a parasitoid ofDiabrotica virgifera virgifera(Coleoptera: Chrysomelidae)
Authors: Zhang F. , Toepfer S. , Kuhlmann U.
Published: January 2004

The tachinidCelatoria compressaWulp has been evaluated as a candidate biological control agent for the western corn rootworm,Diabrotica virgifera virgiferaLeConte, in Europe, where it is an invasive alien pest of maize. Special emphasis has been placed on understanding aspects of the parasitoid basic biology and on developing a rearing technique for a small-scale production ofC. compressapuparia. The age ofC. compressaadults was found to be the most crucial factor in achieving mating. Only newly emerged, 1-h-old females, mated successfully with 2- to 5-day-old males, achieving a success rate of 74%. After mating, a prelarviposition period of 4 days occurred. The 5-day-oldC. compressafemales inserted their eggs containing fully-developed first instars directly into adults ofD. v. virgifera. Total larval and pupal developmental time, including a pre-larviposition period of 4 days, was 29 days under quarantine laboratory conditions (25°C daytime, 15°C at night, L:D 14:10, 50% ± 10% r.h). Females ofC. compressawere capable of producing on average 30 puparia throughout a female’s mean larviposition period of 15 days. A large number of host attacks byC. compressawere unsuccessful, resulting in a mean larviposition success rate of 24% per female. Parasitoid females appear to have difficulties inserting the egg through the intersegmental sutures or membranes around leg openings of the host adults. Although the small-scale rearing technique ofC. compressapresented is both time and labour intensive,C. compressahas been reared successfully for at least 20 successive generations without shifting the 1 male: 1 female sex ratio using a non-diapause strain ofD. v. virgifera.
A morphological study of the Anopheles punctulatus group (Diptera: Culicidae) in the Solomon Islands, with a description of Anopheles (Cellia) irenicus Schmidt, sp.n.
Authors: Schmidt E.R. , Foley D.H. , Bugoro H. , Bryan J.H.
Published: January 2004

A description of Anopheles (Cellia) irenicus Schmidt, sp.n. (formerly A. farauti No. 7) is provided. This species is one of six recorded from the Solomon Islands within the A. punctulatus group, which contains the major vectors of the causative agents of malaria and lymphatic filariasis in the southwest Pacific. Morphological markers are described for adult females, fourth-instar larvae and pupae that identify most specimens of A. irenicus. Keys are presented to distinguish members of the A. punctulatus group in the Solomon Islands.
Intraguild predation among ladybeetles and a green lacewing: do the larval spines of Curinus coeruleus(Coleoptera: Coccinellidae) serve a defensive function?
Authors: Michaud J.P. , Grant A.K.
Published: January 2004

Laboratory experiments examined interspecific interactions between larvae of three coccinellid species, Curinus coeruleus Mulsant (Chilocorinae), Harmonia axyridis Pallas and Olla v-nigrum (Mulsant) (Coccinellinae), and between these and larvae of the green lacewing, Chrysoperla rufilabris (Burmeister). Larvae of C. coeruleus, although defended on their dorsal surface with long spines, had the smallest mandibles, were the slowest-moving, and the least successful in interspecific larval combat. The long spines of third instar C. coeruleusappeared to reduce their palatability as food to H. axyridis and O. v-nigrum larvae in choice tests with dead larvae, but were not an effective defence against these species in Petri dish arenas. Larvae of O. v-nigrum had a smooth dorsal surface, were intermediate in terms of mandible size, but were the fastest moving, a trait that benefited their survival in intraguild combat. Larvae of H. axyridis were intermediate with respect to dorsal spines and speed of movement, but had the largest mandibles. This species was the most effective intraguild combatant among the coccinellids and the only one to successfully compete against C. rufilabris larvae of similar age. The speed, manoeuverability and long mandibles of C. rufilabris enabled them to impale coccinellid larvae at a relatively safe distance. The spines of C. coeruleus larvae impeded laterally oriented attacks by C. rufilabris, but did not provide sustained protection from repeated attacks. Success in these interactions appeared largely a function of offensive weaponry (mandible size and morphology) and speed of movement, although the role of dorsal spines as defensive structures was not ruled out. Rates of larval cannibalism were highest for C. rufilabris and largely mirrored the level of aggression observed in interspecific combat for each species.
Food-plant effects on larval performance do not translate into differences in fitness between populations of Panolis flammea (Lepidoptera: Noctuidae)
Authors: Vanbergen A.J. , Hodgson D.J. , Thurlow M. , Hartley S.E. , Watt A.D.
Published: January 2004

In the UK, Panolis flammea (Denis & Schiffermüller) is a pest of monocultures of non-native lodgepole pine Pinus contorta Douglas, but not of the indigenous host Scots pine P. sylvestrisL. This difference in population dynamics may be due to the adaptation of P. flammea populations to the phenology, chemical composition and natural enemy complement of lodgepole pine. To ascertain if there was local adaptation of P. flammea populations to lodgepole pine, this study tested for improved performance of both larvae and adults on the host plant species from which they were sourced, compared with their performance on the alternative host plant species. No difference was found in the relative mean performance of populations sourced from Scots pine or lodgepole pine plantations, when fed on Scots or lodgepole pine foliage. Larvae grew faster on Scots pine but this difference did not translate into differences in pupal weight, female body weight or fecundity. Indeed, those insects that had fed on lodgepole pine had a longer lifespan than those that had fed on Scots pine, which, if translated into greater probability of mating or higher fecundity, could contribute to the observed outbreak dynamics in the field. The prediction that the observed outbreak dynamics of P. flammea can be explained by the existence of populations locally adapted to lodgepole pine was not supported. These results cast doubt on the use of larval growth parameters as surrogates of fitness in Lepidoptera.
Changes in genotypic composition of Myzus persicae (Hemiptera: Aphididae) on tobacco during the past two decades in Japan
Authors: Shigehara T. , Takada H.
Published: January 2004

Ninety-nine and 476 clones of Myzus persicae (Sulzer) were sampled on tobacco at Kyoto (Shimogamo) (1996–2000) and at 23 other localities (1998–1999) in Japan, respectively. The clones were classified into colour-esterase forms, distinguished by combinations of body colour and electrophoretically detectable esterases, to verify the changes in genotypic composition during the past two decades. Fifteen and 31 colour-esterase forms were found at Kyoto (Shimogamo) and at 23 other localities, respectively. Fourteen (representing c. 95% of the total clones sampled) and 24 (c. 44%) colour-esterase forms, respectively, were different from those found on tobacco during 1978–1985. The frequency of the green form and the very highly insecticide-resistant form increased. More than half of the colour-esterase forms found in the present survey were newly detected. The factors associated with these changes are discussed.
Putting the safety of organic food into perspective
Authors: Magkos Faidon , Arvaniti Fotini , Zampelas Antonis
Published: January 2004

The demand for organic foods is constantly increasing mainly due to consumers' perception that they are healthier and safer than conventional foods. There is a need for information related to food safety to inform consumers of the health benefits and/or hazards of food products of both origins, in order to optimise the impact on health and minimise the risks. Several gaps and limitations in scientific knowledge with regard to food risk evaluation make it difficult to draw generalised conclusions. Still, some organic foods can be expected to contain fewer agrochemical residues and lower levels of nitrate than conventionally grown alternatives. On the other hand, environmental contaminants are equally present in foods of both origins. With regard to other food hazards, such as natural chemicals, microbial pathogens and mycotoxins, no clear conclusions can be drawn, although several interesting points can be highlighted. It is difficult, therefore, to weigh the risks, but what should be made clear to consumers is that ‘organic’ does not equal ‘safe’. If producers adopt proper agricultural practices and consumers maintain hygienic conditions, risks associated with food contaminants can be minimised, regardless of the food's organic or conventional origin.
Health claims on functional foods: the Japanese regulations and an international comparison
Authors: Shimizu Toshio
Published: January 2004

The Japanese scientific academic community defined ‘functional food’ early in the 1980s. That is, functional foods are those that have three functions. The primary function is nutrition. The secondary function is a sensory function or sensory satisfaction. The third is the tertiary function, which is physiological. The Japanese Ministry of Health, Labour, and Welfare (MHLW) set up ‘Foods for Specified Health Use’ (FOSHU) in 1991 as a regulatory system to approve the statements made on food labels concerning the effect of the food on the human body. Food products applying for approval by FOSHU are scientifically evaluated in terms of their effectiveness and safety by the Council of Pharmaceutical Affairs and Food Hygiene under the MHLW. The regulatory range of FOSHU was broadened in 2001 to accept the forms of capsules and tablets in addition to those of conventional foods. FOSHU increased the total to about 330 items in January 2003. The MHLW enacted a new regulatory system, ‘Foods with Health Claims’, in April 2001, which consists of the existing FOSHU system and the newly established ‘Foods with Nutrient Function Claims’ (FNFC). Under the FNFC, twelve vitamins (vitamins A, B1, B2, B6, B12, C, E, D, biotin, pantothenic acid, folic acid, and niacin) and two minerals (Ca and Fe) are standardized. Examples of claims regarding these substances are as follows: ‘Calcium is a nutrient which is necessary to form bones and teeth’; ‘Vitamin D is a nutrient which promotes calcium absorption in the gut intestine and aids in the formation of bones.’ The upper and lower levels of the daily consumption of these nutrients are also determined. The labelling of functional foods should always be based on scientific evidence and be in harmony with international standards. The nutrient–function claim was adopted in the guidelines for nutrition claims by the Codex Alimentarius in 1997. The claims of the Japanese FNFC are equivalent to the nutrient function claims standardized by the Codex Alimentarius. The enhanced function claim and the disease risk-reduction claims were proposed by both the Codex Alimentarius and an Economic Union project in 1999. The structure function claim, which is similar to the enhanced function claim, was enacted by the Dietary Supplement Health and Education Act in the USA in 1994. Most of the statements of the Japanese FOSHU system are close to the category of structure/function claims in the USA or the enhanced function claims of the Codex Alimentarius.
Advances in dietary fibre characterisation. 2. Consumption, chemistry, physiology and measurement of resistant starch; implications for health and food labelling
Authors: Champ Martine , Langkilde Anna-Maria , Brouns Fred , Kettlitz Bernd , Bail-Collet Yves Le
Published: January 2004

Resistant starch (RS) is defined as ‘the sum of starch and products of starch degradation not absorbed in the small intestine of healthy individuals’. This basic definition includes different types of starches that (1) are physically inaccessible, usually due to an encapsulation in intact cell walls, or (2) are naturally highly resistant to mammalian α-amylase, or (3) have been modified by hydrothermic treatments then retrograded. Interest in RS has increased significantly during the last two decades, mostly due to its capacity to produce a large amount of butyrate all along the colon. Butyrate has been observed to have a range of effects on cell metabolism, differentiation and cell growth as well as inhibition of a variety of factors that underlie the initiation, progression and growth of colon tumours. The physiological definition of RS, which seems to be nearly consensual, raises a difficulty in proper analytical quantification of RS. A number of methods have, however, been proposed and provide similar values for the RS content in most of the starch types and starchy foods. It seems, however, that some starches, proven to be partly resistant according toin vivoinvestigations on ileostomy subjects, could not be quantified by most of these methods. This may be due to a widespread use of glucoamylase during the first steps of these methods. Accordingly, there is an international debate on health aspects of RS and on how to quantify the RS content of food products. The present review describes aspects of classification of RS, past and current consumption, physiological effects and analytical aspects, and concludes with impacts on food and product labelling.
Chromium and insulin resistance
Authors: Anderson Richard A.
Published: January 2004

Insulin resistance leads to the inability of insulin to control the utilization and storage of glucose. It is associated initially with elevated levels of circulating insulin followed by glucose intolerance which may progress to type 2 diabetes, hyperlipidaemia, hypertension, obesity and cardiovascular diseases. While the causes of these diseases are multifactorial, one nutrient that is associated with all of these abnormalities is Cr. In the presence of Cr, in a biologically active form, much lower levels of insulin are required. Modern diets, which are often high in refined carbohydrates, are not only low in Cr, but lead to enhanced Cr losses. In response to the consumption of refined carbohydrates, there is a rapid rise in blood sugar leading to elevations in insulin that cause a mobilization of Cr. Once mobilized, Cr is not reabsorbed but lost via the urine leading to decreased Cr stores. Several studies involving both human subjects and experimental animals have reported improvements in insulin sensitivity, blood glucose, insulin, lipids, haemoglobin A1c, lean body mass and related variables in response to improved Cr nutrition. However, not all studies have reported beneficial effects associated with improved Cr nutrition. Well–controlled human studies are needed to document an unequivocal effect of Cr on insulin sensitivity in human subjects. Studies need to involve a significant number of subjects with insulin resistance, glucose intolerance or early stages of diabetes, who have not been taking supplements containing Cr for at least 4 months, and involve at least 400 to 600 μg supplemental Cr daily or more. Studies should be at least 4 months to document sustained effects of supplemental Cr on insulin resistance and related variables. Cr is a nutrient and not a therapeutic agent and therefore will only be of benefit to those whose problems are due to suboptimal intake of Cr.