bluuebunny/crossref_metadata_2025 huggingface dataset:
Perfusion–diffusion compartmental models describe cerebral helium kinetics at high and low cerebral blood flows in sheep
Authors: Doolette David J. , Upton Richard N. , Grant Cliff
Published: January 2005

This study evaluated the relative importance of perfusion and diffusion mechanisms in compartmental models of blood:tissue helium exchange in the brain. Helium has different physiochemical properties from previously studied gases, and is a common diluent gas in underwater diving where decompression schedules are based on theoretical models of inert gas kinetics. Helium kinetics across the cerebrum were determined during and after 15 min of helium inhalation, at separate low and high steady states of cerebral blood flow in seven sheep under isoflurane anaesthesia. Helium concentrations in arterial and sagittal sinus venous blood were determined using gas chromatographic analysis, and sagittal sinus blood flow was monitored continuously. Parameters and model selection criteria of various perfusion‐limited or perfusion–diffusion compartmental models of the brain were estimated by simultaneous fitting of the models to the sagittal sinus helium concentrations for both blood flow states. Purely perfusion‐limited models fitted the data poorly. Models that allowed a diffusion‐limited exchange of helium between a perfusion‐limited tissue compartment and an unperfused deep compartment provided better overall fit of the data and credible parameter estimates. Fit to the data was also improved by allowing countercurrent diffusion shunt of helium between arterial and venous blood. These results suggest a role of diffusion in blood:tissue helium equilibration in brain.
Deletion of the NR2A subunit prevents developmental changes of NMDA‐mEPSCs in cultured mouse cerebellar granule neurones
Authors: Fu Zhanyan , Logan Stephen M. , Vicini Stefano
Published: January 2005

We investigated the role N‐methyl‐d‐aspartate (NMDA) receptor subunits play in shaping excitatory synaptic currents in cultures of cerebellar granule cells (CGCs) from NR2A knockout (NR2A−/−) and wild‐type (+/+) mice. Cultures were maintained in a condition that facilitates the occurrence of functional synapses, allowing us to record NMDA‐miniature excitatory postsynaptic currents (mEPSCs) in addition to NMDA receptor‐mediated whole‐cell currents at three ages in vitro. Whole‐cell NMDA current density decreased with development in both strains though currents from NR2A−/− neurones demonstrated greater sensitivity to CP101 606, an NR2B subunit specific blocker. Sensitivity to Mg2+ blockade decreased with age in vitro in +/+ but not in NR2A−/− CGCs. Immunocytochemistry revealed that dendrites and somas displayed distinct NR1 and NR2A subunit clusters which became increasingly colocalized in +/+ neurones. Qualitatively the overall NR2B subunit staining pattern was similar in +/+ and NR2A−/− neurones throughout development, suggesting that the NR2B subunit distribution is not mediated by the NR2A subunit. In addition, staining with markers for excitatory synapses showed that expression of NR2A subunit (but not NR2B) increases at both synaptic and extrasynaptic sites in +/+ neurones during development. In parallel, NMDA‐mEPSCs were faster in +/+ compared with NR2A−/− neurones at all time points studied, suggesting that the NR2A subunit begins to replace NR2B‐rich NMDA receptors even at early stages of development. Many NR2A−/− neurones were devoid of NMDA‐mEPSCs at the later time point, and transfection of the NR2A subunit in these neurones restored fast decay and the occurrence of NMDA‐mEPSCs. Taken together, our results indicate that the NR2A subunit is mainly responsible for the developmental changes observed in the maturation of excitatory synapses.
Interactions between long latency afferent inhibition and interhemispheric inhibitions in the human motor cortex
Authors: Kukaswadia Sadiya , Wagle‐Shukla Aparna , Morgante Francesca , Gunraj Carolyn , Chen Robert
Published: January 2005

Various inhibitory pathways exist in the human brain which are crucial in modulating motor cortex output and they can be investigated non‐invasively using transcranial magnetic stimulation. Interhemispheric inhibition (IHI) is one form of cortical inhibition. It can be elicited by stimulation of the opposite motor cortex at interstimulus intervals (ISIs) of 10 ms (IHI10) or 40 ms (IHI40) and inhibitions at these intervals are probably mediated by different mechanisms. Peripheral sensory stimulation can also inhibit the motor cortex. Median nerve stimulation produces long latency afferent inhibition (LAI) at ISI 200 ms. LAI inhibits another form of cortical inhibition known as long interval intracortical inhibition (LICI) and a study that examined the interaction between IHI10 and LICI hypothesized that they are mediated by an overlapping population of inhibitory neurones. We tested this hypothesis by examining the interaction between IHI10, IHI40 and LAI. With increasing test MEP amplitude LAI, IHI10 and IHI40 all decreased. There was no correlation between the strength of LAI, IHI10 and IHI40. In the presence of LAI, IHI10 was slightly but significantly reduced compared to IHI10 alone. There was no correlation between the reduction in IHI10 in the presence of LAI and the strength of LAI or IHI10. In the presence of LAI, IHI40 was significantly reduced compared to IHI40 alone. LAI produced a greater decrease in IHI40 than in IHI10. The decrease in IHI40 in the presence of LAI strongly correlated with the strength of LAI but not with the strength of IHI40. Reducing the strength of LAI, IHI10 and IHI40 still resulted in similar interaction between IHI10 and LAI but markedly decreased the effect of LAI on IHI40. We conclude that LAI and IHI10 do not directly inhibit each other but LAI probably inhibits IHI40. LICI is more likely to be related to IHI40 than to IHI10.
Inhibition of cellular responses to insulin in a rat liver cell line. A role for PKC in insulin resistance
Authors: Puljak Livia , Pagliassotti Michael J. , Wei Yuren , Qadri Ishtiaq , Parameswara Vinay , Esser Victoria , Fitz J. Gregory , Kilic Gordan
Published: January 2005

The initial response of liver cells to insulin is mediated through exocytosis of Cl− channel‐containing vesicles and a subsequent opening of plasma membrane Cl− channels. Intracellular accumulation of fatty acids leads to profound defects in metabolism, and is closely associated with insulin resistance. It is not known whether the activity of Cl− channels is altered in insulin resistance and by which mechanisms. We studied the effects of fatty acid accumulation on Cl− channel opening in a model liver cell line. Overnight treatment with amiodarone increased the fat content by ∼2‐fold, and the rates of gluconeogenesis by ∼5‐fold. The ability of insulin to suppress gluconeogenesis was markedly reduced indicating that amiodarone treatment induces insulin resistance. Western blot analysis showed that these cells express the same number of insulin receptors as control cells. However, insulin failed to activate exocytosis and Cl− channel opening. These inhibitory effects were mimicked in control cells by exposures to arachidonic acid (15 μm). Further studies demonstrated that fatty acids stimulate the PKC activity, and inhibition of PKC partially restored exocytosis and Cl− channel opening in insulin‐resistant cells. Accordingly, activation of PKC with PMA in control cells potently inhibited the insulin responses. These results suggest that stimulation of PKC activity in insulin resistance contributes to the inhibition of cellular responses to insulin in liver cells.
Safety of the Blood Supply in Latin America
Authors: Schmunis Gabriel A. , Cruz Jose R.
Published: January 2005

Appropriate selection of donors, use of sensitive screening tests, and the application of a mandatory quality assurance system are essential to maintain the safety of the blood supply. Laws, decrees, norms, and/or regulations covering most of these aspects of blood transfusion exist in 16 of the 17 countries in Latin America that are the subject of this review. In 17 countries, there is an information system that, although still incomplete (there are no official reports on adverse events and incidents), allows us to establish progress made on the status of the blood supply since 1993. Most advances originated in increased screening coverage for infectious diseases and better quality assurance. However, in 2001 to 2002, tainted blood may have caused infections in 12 of the 17 countries; no country reached the number of donors considered adequate, i.e., 5% of the population, to avoid blood shortages, or decreased significantly the number of blood banks, although larger blood banks are more efficient and take advantage of economies of scale. In those years, paid donors still existed in four countries and replacement donors made up >75% of the blood donors in another eight countries. In addition, countries did not report the number of voluntary donors who were repeat donors, i.e., the healthiest category. In spite of progress made, more improvements are needed.
Mechanical Transmission of Human Protozoan Parasites by Insects
Authors: Graczyk Thaddeus K. , Knight Ronald , Tamang Leena
Published: January 2005

The filthy breeding habits, feeding mechanisms, and indiscriminate travel between filth and food make some groups of synanthropic insects such as nonbiting flies and cockroaches efficient vectors of human enteric protozoan parasites. Twenty-one species of filth flies have been listed by regulatory agencies concerned with sanitation and public health as causative agents of gastrointestinal diseases based on synanthropy, endophily, communicative behavior, and strong attraction to filth and human food. Outbreaks and cases of food-borne diarrheal diseases in urban and rural areas are closely related to the seasonal increase in abundance of filth flies, and enforced fly control is closely related to reductions in the occurrence of such diseases. Mechanical transmission of human parasites by nonbiting flies and epidemiological involvement of other synanthropic insects in human food-borne diseases have not received adequate scientific attention.
Combination Treatment of Invasive Fungal Infections
Authors: Mukherjee Pranab K. , Sheehan Daniel J. , Hitchcock Christopher A. , Ghannoum Mahmoud A.
Published: January 2005

The persistence of high morbidity and mortality from systemic fungal infections despite the availability of novel antifungals points to the need for effective treatment strategies. Treatment of invasive fungal infections is often hampered by drug toxicity, tolerability, and specificity issues, and added complications often arise due to the lack of diagnostic tests and to treatment complexities. Combination therapy has been suggested as a possible approach to improve treatment outcome. In this article, we undertake a historical review of studies of combination therapy and also focus on recent studies involving newly approved antifungal agents. The limitations surrounding antifungal combinations include nonuniform interpretation criteria, inability to predict the likelihood of clinical success, strain variability, and variations in pharmacodynamic/pharmacokinetic properties of antifungals used in combination. The issue of antagonism between polyenes and azoles is beginning to be addressed, but data regarding other drug combinations are not adequate for us to draw definite conclusions. However, recent data have identified potentially useful combinations. Standardization of assay methods and adoption of common interpretive criteria are essential to avoid discrepancies between different in vitro studies. Larger clinical trials are needed to assess whether combination therapy improves survival and treatment outcome in the most seriously debilitated patients afflicted with life-threatening fungal infections.
Preventing Varicella-Zoster Disease
Authors: Hambleton Sophie , Gershon Anne A.
Published: January 2005

Varicella-zoster virus (VZV), the cause of chickenpox and shingles, is a pathogen in retreat following the introduction of mass vaccination in the United States in 1995. The live attenuated Oka vaccine, which is safe and immunogenic, gives good protection against both varicella and zoster in the short to medium term. It has undoubtedly been highly effective to date in reducing all forms of varicella, especially severe disease. However, the huge pool of latent wild-type virus in the population represents a continuing threat. Both the biology and the epidemiology of VZV disease suggest that new vaccination strategies will be required over time.
Whole cells ofBacillus subtilisAF 1 proved more effective than cell-free and chitinase-based formulations in biological control of citrus fruit rot and groundnut rust
Authors: Manjula K , Kishore G Krishna , Podile A R
Published: January 2005

In foliar and postharvest biocontrol systems, the use of active metabolites produced by antagonistic microorganisms is advantageous compared with the use of living microorganisms. Chitinases, a major group of hydrolytic enzymes produced by biocontrol agents, are involved in the lysis of cell walls of pathogenic fungi. In the present study, an attempt was made to test the partially purified β-1,4-N-acetylglucosaminidase (NAGase) of a biocontrol strain Bacillus subtilis AF 1 for control of rust in groundnut (caused by Puccinia arachidis) and soft rot in lemons (caused by Aspergillus niger). Four proteins of molecular mass 67, 40, 37, and 32 kDa were isolated from the culture filtrates of AF 1 by affinity chromatography, of which the 67-kDa protein has detectable chitinolytic ability. This protein (NAGase) effectively inhibited the in vitro growth of A. niger in microtitre plates. In the presence of NAGase, germination of urediniospores of P. arachidis was reduced by 96% compared with the control. In a detached leaf bioassay, NAGase reduced the rust lesion frequency by >60%. NAGase significantly reduced the incidence of soft rot in harvested lemon fruits. However, fresh cells and (or) alginate formulation of AF 1 were more effective than NAGase in control of both of the test plant – pathogen systems.Key words: chitinase, peanut rust, lemon fruit rot, biocontrol.
Comparison of methods for the concentration ofCryptosporidiumoocysts andGiardiacysts from raw waters
Authors: Ferguson Christobel , Kaucner Christine , Krogh Martin , Deere Daniel , Warnecke Malcolm
Published: January 2005

This study compared the recovery of Cryptosporidium oocysts and Giardia cysts ((oo)cysts) from raw waters using 4 different concentrationelution methods: flatbed membranes, FiltaMaxTMfoam, EnvirochekTMHV capsules, and Hemoflow ultrafilters. The recovery efficiency of the combined immunomagnetic separation and staining steps was also determined. Analysis of variance of arcsine-transformed data demonstrated that recovery of Cryptosporidium oocysts by 2 of the methods was statistically equivalent (flatbed filtration 26.7% and Hemoflow 28.3%), with FiltaMaxTMand EnvirochekTMHV recoveries significantly lower (18.9% and 18.4%). Recovery of Giardia cysts was significantly higher using flatbed membrane filtration (42.2%) compared with the other 3 methods (EnvirochekTMHV 29.3%, FiltaMaxTM29.0%, and Hemoflow 20.9%). All methods were generally acceptable and are suitable for laboratory use; 2 of the methods are also suitable for field use (FiltaMaxTMand EnvirochekTMHV). In conclusion, with recoveries generally being statistically equivalent or similar, practical considerations become important in determining which filters to use for particular circumstances. The results indicate that while low-turbidity or "finished" waters can be processed with consistently high recovery efficiencies, recoveries from raw water samples differ significantly with variations in raw water quality. The use of an internal control with each raw water sample is therefore highly recommended.Key words: catchments, EnvirochekTMHV, Hemoflow, FiltaMaxTM, flatbed filtration.
Experimental evidence for plasmid-bornenor-nirgenes inSinorhizobium melilotiJJ1c10
Authors: Chan Yiu-Kwok , McCormick Wayne A
Published: January 2005

In denitrification, nir and nor genes are respectively required for the sequential dissimilatory reduction of nitrite and nitric oxide to form nitrous oxide. Their location on the pSymA megaplasmid of Sinorhizobium meliloti was confirmed by Southern hybridization of its clones with specific structural gene probes for nirK and norCB. A 20-kb region of pSymA containing the nor-nir genes was delineated by nucleotide sequence analysis. These genes were linked to the nap genes encoding periplasmic proteins involved in nitrate reduction. The nor-nir-nap segment is situated within 30 kb downstream from the nos genes encoding nitrous oxide reduction, with a fix cluster intervening between nir and nos. Most of these predicted nor-nir and accessory gene products are highly homologous with those of related proteobacterial denitrifiers. Functional tests of Tn5 mutants confirmed the requirement of the nirV product and 1 unidentified protein for nitrite reduction as well as the norB-D products and another unidentified protein for nitric oxide reduction. Overall comparative analysis of the derived amino acid sequences of the S. meliloti gene products suggested a close relationship between this symbiotic N2fixer and the free-living non-N2-fixing denitrifier Pseudomonas G-179, despite differences in their genetic organization. This relationship may be due to lateral gene transfer of denitrification genes from a common donor followed by rearrangement and recombination of these genes.Key words: denitrification genes, nitric oxide reductase, nitrite reductase, Rhizobiaceae, Sinorhizobium meliloti.
Strategy to select and assess antagonistic bacteria for biological control ofRhizoctonia solaniKühn
Authors: Faltin Franziska , Lottmann Jana , Grosch Rita , Berg Gabriele
Published: January 2005

A screening strategy was developed to assess the potential of plant-associated bacteria to control diseases caused by Rhizoctonia solani Kühn. About 434 already characterized antagonistic bacterial strains isolated from diverse plant species and microenvironments were evaluated for biocontrol and plant growth promotion by a hierarchical combination of assays. Analyzing in vitro antagonism towards different Rhizoctonia isolates resulted in a selection of 20 potential biocontrol agents. The strains were characterized by their antagonistic mechanisms in vitro as well as their production of the plant growth hormone indole-3-acetic acid. The plant growth promoting effect by antagonistic bacteria was determined using a microtiter plate assay on the basis of lettuce seedlings. Lettuce and sugar beet as host plant were included in the biocontrol experiments in which the antagonistic effect of 17 bacterial isolates could be confirmed in vivo. Sequencing of the 16S rDNA gene and (or) fatty acid methyl ester gas chromatography was used to identify the antagonistic isolates. Molecular fingerprints of isolates obtained by BOX – polymerase chain reaction were compared to avoid further investigation with genetically very similar strains and to obtain unique molecular fingerprints for quality control and patent licensing. According to our strategy, an assessment scheme was developed and four interesting biological control agents, Pseudomonas reactans B3, Pseudomonas fluorescens B1, Serratia plymuthica B4, and Serratia odorifera B6, were found. While S. plymuthica B4 was the best candidate to biologically control Rhizoctonia in lettuce, P. reactans B3 was the best candidate to suppress the pathogen in sugar beet.Key words: biocontrol, Rhizoctonia solani, lettuce, sugar beet, antagonistic bacteria.
Co-induction of methyltransferase Rv0560c by naphthoquinones and fibric acids suggests attenuation of isoprenoid quinone action inMycobacterium tuberculosis
Authors: Garbe Thomas R
Published: January 2005

The superoxide generator menadione was previously demonstrated as an inducer of growth stage dependent protein patterns in Mycobacterium tuberculosis. The present study refines this observation by characterizing a novel 27-kDa protein that had not been observed in previous studies relying on younger cultures. A very similar response, based on two-dimensional gel electrophoretic analyses, was induced by the closely related naphthoquinone plumbagin. The 27-kDa protein was also induced by the pro-oxidant peroxisome proliferator gemfibrozil and to a lesser extent by the structurally related compounds fenofibrate and clofibrate. N-terminal sequence data of proteolytic fragments from the 27-kDa protein demonstrated its identity with protein Rv0560c, previously demonstrated to be inducible by salicylate, which also possesses peroxisome proliferating properties. Protein Rv0560c bears three conserved motifs characteristic of S-adenosylmethionine-dependent methyltransferases. Further sequence similarities suggest a function in the bio syn thesis of isoprenoid compounds, e.g., tocopherol, ubiquinone, and sterols. Such involvement is supported by the recognized yet unexplained widespread interference of menadione, salicylate, and fibrates with the isoprenoid quinones ubiquinone, menaquinone, and vitamin K. Induction of Rv0560c by fibrates, salicylate, and naphthoquinones is thus suggested to be caused by action on the plasma membrane, reminiscent of cytochrome P450BM-3 induction by fibrates in Bacillus megaterium, which catalyzes the hydroxylation of fatty acids and thus modulates membrane properties.Key words: peroxisome proliferators, membrane derangement, menaquinone antagonism, respiratory inhibition.
Three unlinked gene clusters are involved in clavam metabolite biosynthesis in Streptomyces clavuligerus
Authors: Tahlan Kapil , Park Hyeon Ung , Jensen Susan E
Published: January 2005

In Streptomyces clavuligerus, three groups of genes are known to be involved in the biosynthesis of the clavam metabolites. Since antibiotic biosynthetic genes are invariably clustered on the chromosome in prokaryotes, chromosome walking was undertaken in an attempt to show that the three groups of clavam genes would resolve into a single super-cluster when analyzed at larger scale. However, no evidence of linkage between the three groups was obtained. Furthermore, Southern analysis of macro-restriction fragments of genomic DNA separated by pulsed-field gel electrophoresis also indicated that the three groups of genes are not linked. Despite the structural and biosynthetic relatedness of the clavam metabolites, our results suggest that the genes involved in their production lie in three unlinked gene clusters. We believe that this represents the first instance in bacteria of genes involved in the biosynthesis of a single family of antibiotics sharing a common biosynthetic pathway and yet residing in three separate locations on the chromosome.Key words: Streptomyces, clavulanic acid, clavams, paralogues, gene clusters.
Pandemic strains of O3:K6Vibrio parahaemolyticusin the aquatic environment of Bangladesh
Authors: Islam M Sirajul , Tasmin Rizwana , Khan Sirajul Islam , Bakht Habibul Bari Mahmud , Mahmood Zahid Hayat , Rahman M Ziaur , Bhuiyan Nurul Amin , Nishibuchi Mitsuaki , Nair G Balakrish , Sack R Bradley , Huq Anwar , Colwell Rita R , Sack David A
Published: January 2005

A total of 1500 environmental strains of Vibrio parahaemolyticus, isolated from the aquatic environment of Bangladesh, were screened for the presence of a major V. parahaemolyticus virulence factor, the thermostable direct haemolysin (tdh) gene, by the colony blot hybridization method using a digoxigenin-labeled tdh gene probe. Of 1500 strains, 5 carried the tdh sequence, which was further confirmed by PCR using primers specific for the tdh gene. Examination by PCR confirmed that the 5 strains were V. parahamolyticus and lacked the thermostable direct haemolysin-related haemolysin (trh) gene, the alternative major virulence gene known to be absent in pandemic strains. All 5 strains gave positive Kanagawa phenomenon reaction with characteristic β-haemolysis on Wagatsuma agar medium. Southern blot analysis of the HindIII-digested chromosomal DNA demonstrated, in all 5 strains, the presence of 2 tdh genes common to strains positive for Kanagawa phenomenon. However, the 5 strains were found to belong to 3 different serotypes (O3:K29, O4:K37, and O3:K6). The 2 with pandemic serotype O3:K6 gave positive results in group-specific PCR and ORF8 PCR assays, characteristics unique to the pandemic clone. Clonal variations among the 5 isolates were analyzed by comparing RAPD and ribotyping patterns. Results showed different patterns for the 3 serotypes, but the pattern was identical among the O3:K6 strains. This is the first report on the isolation of pandemic O3:K6 strains of V. parahaemolyticus from the aquatic environment of Bangladesh.Key words: pandemic strains, Vibrio parahaemolyticus, aquatic environment.
Settleability and kinetics of a nitrifying sludge in a sequencing batch reactor
Authors: Texier A -C , Gomez J
Published: January 2005

A physiological study of a nitrifying sludge was carried out in a sequencing batch reactor (SBR). Pseudo steady-state nitrification conditions were obtained with an ammonium removal efficiency of 99% ± 1% and 98% ± 2% conversion of NH4+-N to NO3–-N. The rate of biomass production was negligible (1.3 ± 0.1 mg microbial protein-N·L–1·d–1). The sludge presented good settling properties with sludge volume index values lower than 20 mL·g–1and an exopolymeric protein/carbohydrate ratio of 0.53 ± 0.34. Kinetic results indicated that the nitrifying behavior of the sludge changed with the number of cycles. After 22 cycles, a decrease in the specific rate of NO3–-N production coupled with an increase in the NO2–-N accumulation were observed. These results showed that the activity of the nitrite oxidizing bacteria decreased at a longer operation time. Ammonia oxidizing bacteria were found to exhibit the best stability. After 4 months of operation, the specific rates of NH4+-N consumption and NO3–-N production were 1.72 NH4+-N per microbial protein-N per hour (g·g–1·h–1) and 0.54 NO3–-N per microbial protein-N per hour (g·g–1·h–1), respectively.Key words: nitrification, sequencing batch reactor, kinetics, settleability, exopolymeric substances.
Nature of the genome of the saprophytic spirochete Spirochaeta aurantia and its ribosomal RNA operons
Authors: McLaughlin Richard , Secko David M , Paul Catherine J , Kropinski Andrew M
Published: January 2005

Using restriction endonucleases DraI, AseI, and I-CeuI in conjunction with pulsed-field gel electrophoresis, we have shown that Spirochaeta aurantia M1 possesses a circular 3.98-Mb genome. This is the second largest spirochete chromosome yet analyzed. The observation that the latter enzyme cuts in 3 places suggests the presence of 3 copies of the large subunit (23S) rRNA gene (rrl), which was confirmed by Southern hybridizations. The complete sequence of 2 of the ribosomal RNA operons was determined, revealing that their structure resembled that of the typical member of the bacterial superkingdom: rrs (16S; 1561 bp), tRNA, rrl (23S; 2972 bp), and rrf (5S; 110 bp). The S. aurantia rrs–rrl intergenic regions, as with Treponema denticola, contain genes specifying a 73-nt tRNAAla (anticodon TGC) and a 77-nt tRNAIle (anticodon GAT).Key words: spirochete, pulsed-field gel electrophoresis, ribosomal RNA, operon, Spirochaeta aurantia.
Fate of Bacillus thuringiensis strains in different insect larvae
Authors: Suzuki Marise Tanaka , Lereclus Didier , Arantes Olivia M. Nagy
Published: January 2005

In favorable conditions Bacillus thuringiensis spores germinate and vegetative cells multiply, whereas in unfavorable conditions Bacillus thuringiensis sporulates and produces insecticidal crystal proteins. The development of B. thuringiensis strains was investigated in the larvae of insects belonging to the orders Lepidoptera and Diptera. Bacillus thuringiensis strains able to kill the insects did not always multiply in cadavers. Strains with no specificity to kill the insect sometimes multiplied when the insects were killed mechanically. These results indicate that some insect larvae represent an environment that favors the germination of B. thuringiensis spores and the multiplication of vegetative cells; however, there was no correlation between the toxin specificity and the specificity of the host.Key words: Bacillus thuringiensis, Cry protein, insect pathogen, bacterial growth.
Use of 1,4-naphthoquinones for control ofErwinia carotovora
Authors: Medina Luis F.C , Stefani Valter , Brandelli Adriano
Published: January 2005

The antimicrobial effect of 5 naphthoquinones was tested against the phytopathogenic bacteria Erwinia carotovora. Disk diffusion tests and determination of minimal inhibitory concentrations (MIC) indicate that the compound naphthazarin (NTZ) has the best antibacterial activity among the naphthoquinones tested. Studies on the mode of action indicate the effect of NTZ was bactericidal at 10 µg/mL. When cultivation was done in the presence of sodium ascorbate, the restoration of E. carotovora growth was observed with 3 µg/mL NTZ, but not when a 10 µg/mL dose was used. The incubation of NTZ with bacterial suspension of E. carotovora resulted in important changes in the absorption spectra of this naphthoquinone, indicating that a redox reaction takes place. These results may suggest that NTZ induces an increase of reactive oxygen species that are toxic to the cell. The compound NTZ was also effective in preventing E. carotovora growth on potato tubers, inhibiting the soft rot development at a concentration of 2 mg/mL.Key words: antimicrobial, naphthazarin, phytopathogen, potato, 5,8-dihydroxy-1,4-naphthoquinone.
Survival of enterococci and Tn916-like conjugative transposons in soil
Authors: Andrews Jr. Robert E , Johnson Wesley S , Guard Abby R , Marvin Jonathan D
Published: January 2005

The persistence of Enterococcus faecalis, fecal enterococci from swine waste, and Tn916-like elements was determined following inoculation into autoclaved and native soil microcosms. When cells of E. faecalis CG110 (Tn916) were inoculated into native microcosms, enterococcal viability in the soil decreased approximately 5 orders of magnitude (4.8 × 105CFU/g soil to < 10 CFU/g) after 5 weeks. In autoclaved microcosms, the viability of E. faecalis decreased by only 20% in 5 weeks. In contrast, the content of Tn916, based on PCR of DNA extracts from soil microcosms, decreased by about 20% in both native and autoclaved microcosms. Similar results were obtained when the source of fecal enterococci and Tn916-like elements was swine waste. Because the concentration of Tn916-independent E. faecalis DNA (the D-alanine D-alanine ligase gene), based on PCR, decreased to nearly undetectable levels (at least 3 orders of magnitude) after 5 weeks in the native microcosms, the evidence suggests Tn916 stability in the soil results from en masse transfer of the transposon to the normal soil microflora and not survival of E. faecalis DNA in the soil system. Results from denaturing gradient gel electrophoresis suggest that multiple forms of Tn916 occur in swine waste, but only forms most like Tn916 exhibit stability in the soil.Key words: Tn916, Enterococcus faecalis, soil, antibiotic resistance, conjugation, transposon.
Autumn diet of harbour seals (Phoca vitulina) at Prins Karls Forland, Svalbard, assessed via scat and fatty-acid analyses
Authors: Andersen Signe M , Lydersen Christian , Grahl-Nielsen Otto , Kovacs Kit M
Published: January 2005

This study used hard-part analyses from scats (n = 117) and stomachs (n = 3) to investigate the diet of high Arctic harbour seals (Phoca vitulina L., 1758) living on Prins Karls Forland, Svalbard, in early autumn. Additionally, it compared the results of fatty-acid analyses of the seals' blubber versus that of potential prey with the findings of the more traditional diet assessment method. Svalbard harbour seals appear to be opportunistic, polyphagous feeders similar to the situation in other parts of their range. Members of the cod-family, and secondarily the sculpin-family, dominated the diet of harbour seals on Svalbard. Small fish comprised most of the diet of the harbour seals; invertebrates appeared to be insignificant. Atlantic cod (Gadus morhua L., 1758) was the most important species in the diet in terms of biomass, whereas polar cod (Boreogadus saida (Lepechin, 1774)) was the most frequently consumed prey. Our comparison between hard-part diet analyses and fatty acids is far from definitive, but it indicates a general influence of the diet on the fatty-acid composition of the inner blubber layer. However, it also suggests systematic selective processes in the incorporation of fatty acids into the blubber. Observed differences between the fatty-acid composition of the different blubber layers and possible differences between sex and age classes warrant further investigation.
Dominance-related foraging in female domesticated canaries under laboratory conditions
Authors: Parisot M , Nagle L , Vallet E , Kreutzer M
Published: January 2005

Many experiments have tested the foraging behaviours of birds relative to their social status. However, results are still not completely clear about the relationship between foraging behaviour and social status in birds. Some studies have shown that dominants use subordinates as food finders, while others show the opposite. Whether dominants search by themselves or wait to exploit the findings of a subordinate is still an unanswered question. For testing these alternative hypotheses, we carried out a laboratory experiment that used female common domesticated canaries, Serinus canaria (L., 1758). We used strict female flocks to avoid any bias based on pair bonds. We looked at the foraging behaviours of females relative to their social status using a foraging board. Our results showed that dominant females behaved as their own food finder. They began searching in the first position and had greater re-search behaviours, which allowed them to find seeds more rapidly than subordinates. Our study showed that foraging behaviour of dominants may be independent of the activities of subordinates. Our results also showed that there was no difference between the number of attacks received by dominants and subordinates when they were on the foraging board, which suggests that subordinates accessed the foraging board less frequently to avoid competition with dominants. We also suggest that environmental conditions may be one explanation for the differences observed among the different studies.
Courtship song in Drosophila melanogaster: a differential effect on male–female locomotor activity
Authors: Kowalski Solange , Aubin Thierry , Martin Jean-René
Published: January 2005

The courtship song of male Drosophila melanogaster Meigen, 1830 is involved in species recognition and sexual stimulation. This signal is usually addressed to the female to reduce her locomotor activity, thereby facilitating copulation. However, no accurate quantification of her locomotion has been made. To examine the effect of courtship song on locomotor behaviour of both sexes, we used a video-tracking system that allowed for the quantification of two indicators of activity level: distance moved and movement duration. First, we showed that the broadcast of the courtship song alone produced no effect on female locomotion. Females reduced their locomotor activity only when acoustical stimulation was placed in a natural courtship context (i.e., in the presence of a male). This suggests that the sum of visual, tactile, acoustic, and chemical stimuli provided by the male may act together to trigger female receptivity. Second, our playback experiments showed a strong stimulating effect of courtship song (particularly of the pulse component) on the locomotor activity of isolated males, suggesting that this signal probably plays a role in male stimulation. Courtship song has an opposite effect on male/female locomotor activity in D. melanogaster.
Detrimental effects of larval blow flies (Protocalliphora azurea) on nestlings and breeding success of Tree Sparrows (Passer montanus)
Authors: Puchala Peter
Published: January 2005

The effect of bloodsucking parasitic larvae of the blow fly Protocalliphora azurea (Fallén, 1817) (Diptera) on Tree Sparrow, Passer montanus (L., 1758), breeding success was studied in populations breeding in nest boxes in southwestern Slovakia. Out of 52 examined nests only seven broods (13%) were unparasitized. The mean number of larvae per parasitized nest was 22.6 and the total number of parasites per nest ranged from 1 to 80. Large numbers of blow fly larvae and pupae significantly influenced nestling survival and fledging success. In broods with parasite load per chick higher than nine, at least one nestling died. To record the effects of parasites on the body size of nestlings of different ages, nestlings were measured on days 5, 10, and 13 post hatch. First and second broods were analysed separately. A significant negative effect of parasite load per nestling on the body mass, wing length, tarsal length, and tail length of nestlings was found in the second broods only in the 10- and 13-day-old chicks. Tree Sparrow parents did not prolong nestling provisioning time per nestling, as there was no negative relationship between parasite load per nestling and feeding period. Contradictory to most previous studies of the genus Protocalliphora, the present study suggests that these parasites have an important negative impact on the breeding success of the studied Tree Sparrow populations.
Growth models and longevity of freshwater pearl mussels (Margaritifera margaritifera) in Spain
Authors: Miguel E San , Monserrat S , Fernández C , Amaro R , Hermida M , Ondina P , Altaba C R
Published: January 2005

Growth rates of populations of the freshwater pearl mussel, Margaritifera margaritifera (L., 1758), in northwestern Spain were analysed based on measurements of annual annuli and using two nonlinear functions for length-at-age data sets: von Bertalanffy's growth model and a hyperbolic function. These populations reach the smallest maximum shell length (90.5 mm) and have the shortest life-span (35 years) and the highest growth rate (k in von Bertalanffy's model >0.1·year–1, on average) known for this species. The two models were similar in performance and were well fitted (around 99%) to shell-length-at-age data, although the hyperbolic function appears to be applicable only from 6 years of age. The growth rate (either k or k' from the hyperbolic function) showed a large and significant variation across populations, both among and within drainages.
Season variation in nutrient composition of Alaskan walleye pollock
Authors: Kitts David D , Huynh Minh Dieu , Hu Chun , Trites Andrew W
Published: January 2005

A popular hypothesis for the noted steady decline in the population of Steller sea lions, Eumetopias jubatus (Schreber, 1776), in the regions from Prince William Sound through the Aleutian Islands relates to their nutritional status. Sea lion diets appear to have shifted from primarily small schooling fatty fishes to low-fat fish such as walleye pollock, Theragra chalcogramma (Pallas, 1814). We examined the seasonal changes in proximate nutrients of pollock collected in the Bering Sea. Mean energy density (dry mass) of pollock peaked in October then declined and remained low throughout winter. Energy recovery occurred in the summer months with strong recovery observed in female fish caught in July. Contrary to whole fish carcass energy contents, both total protein and moisture contents were at their highest levels in winter (January) when total crude lipid content was at its lowest (p < 0.05). This trend gradually declined to its lowest levels in the fall when lipid content was high. The decline in total lipids during winter seasons appeared to parallel gonad development during the prespawning period. Sex differences in energy densities were not found. Proximate analysis data for moisture, protein, ash, and lipid content also did not show any significant variation between males and females. Protein digestibility of pollock was higher (p < 0.05) in the summer than in the spring, but not different for winter or fall. We concluded that the nutrient content of walleye pollock may have some impact on the Steller sea lions that feed on them, particularly the energetic value that appears to be low during important feeding periods for this marine mammal.
Climate change and the initiation of spring breeding by deer mice in the Kananaskis Valley, 1985–2003
Authors: Millar John S , Herdman Emily J
Published: January 2005

Deer mice (Peromyscus maniculatus (Wagner, 1845)) in the Kananaskis Valley were monitored from 1985 to 2003 by livetrapping, and first parturition dates were compared among years and examined in relation to spring weather. On average, first litters were conceived on 2 May, well after the winter snowpack melted (19 March) and just before average temperatures reached 0 °C (8 May). First parturitions took place on 26 May, when average temperatures were above freezing. The average temperature at the time of conceptions (late April – early May) declined by approximately 2 °C, and the date that the average temperatures reached 0 °C was 11 days later, between 1985 and 2003, with potential effects for summer phenology. Spring temperatures, but not snowfall, were related to the El Niño Southern Oscillation index. The initiation of breeding by deer mice was variable among years, but was not related to snowfall or temperature and did not change, on average, between 1985 and 2003. The decrease in spring temperatures had no noticeable effects on breeding success. We conclude that photoperiod may be a primary cue for the initiation of spring breeding and that food resources over winter may explain the among-year variation in the initiation of breeding.
Experiments on egg discrimination in two North American corvids: further evidence for retention of egg ejection
Authors: Underwood Todd J , Sealy Spencer G , McLaren Celia M
Published: January 2005

In the absence of brood parasitism in North America, black-billed magpies, Pica hudsonia (Sabine, 1822), and yellow-billed magpies, Pica nuttalli (Audubon, 1837), may have retained egg-discrimination behaviour that evolved in Eurasian magpies, Pica pica (L., 1758), in response to parasitism by Old World cuckoos. We further examined this hypothesis by testing the egg-discrimination abilities of black-billed magpies and the American crow, Corvus brachyrhynchos Brehm, 1822, which has no history of brood parasitism. In addition, we tested an alternative hypothesis that black-billed magpies evolved or retained egg discrimination to counter conspecific parasitism by testing their ability to eject foreign conspecific eggs and by using a signal detection model to estimate the level of conspecific parasitism required for ejection to be favoured. Black-billed magpies ejected all non-mimetic eggs and 62% of mimetic eggs. Significantly more mimetic eggs were ejected during the incubation stage than during the laying stage. Magpies ejected significantly more non-mimetic eggs than mimetic eggs overall, but there was no difference in ejection frequency during incubation. American crows ejected 21% of non-mimetic eggs and 8% of mimetic eggs. There was no significant difference in ejection frequency of the two egg types. Black-billed magpies ejected 11% of conspecific eggs and a relatively high level of conspecific parasitism (22%49%) would be required to select for conspecific ejection, which provides little support for conspecific parasitism as a current selection pressure for maintaining egg discrimination. Thus, black-billed magpies appear to have retained egg rejection in the absence of parasitism through speciation from Eurasian magpies.
Wolf homesite attendance patterns
Authors: Potvin Marcel J , Peterson Rolf O , Vucetich John A
Published: January 2005

Adult gray wolves, Canis lupus L., 1758, frequent den and rendezvous sites (homesites) during summer to bring food to pups and to ensure security of the pups. We monitored homesite attendance of several adult wolves from a single pack in Isle Royale National Park, Michigan, for 6 years. Pack size, number of pups, and prey density varied during the period of monitoring. Given the effect of prey density on wolf behavior, we predicted that wolf homesite attendance patterns would vary with prey density. We also examined the effects of varying pack size, social status, and number of pups on homesite attendance. Contrary to our expectations, prey density did not appear to be a significant predictor of homesite attendance statistics such as hours per day at the homesite or length of absence from the homesite. Furthermore, when prey density and social status remained the same, homesite attendance (hours/day) of individual wolves monitored for multiple years varied substantially. Our results show homesite attendance to be highly variable and not well predicted by prey density.
Why is brood reduction in Florida scrub-jays higher in suburban than in wildland habitats?
Authors: Shawkey Matthew D , Bowman Reed , Woolfenden Glen E
Published: January 2005

In a population of Florida scrub-jays, Aphelocoma coerulescens (Bosc, 1795), in a suburban scrub habitat, partial brood loss is much more common (averaging about 30% of nestlings from successful nests) than in a natural habitat (averaging about 5%). We hypothesized that this partial brood loss was attributable to starvation of last-hatched nestlings (i.e., brood reduction), and that large differences in partial brood loss were caused by differences in arthropod food abundance between the two sites. To test these hypotheses, we closely monitored nests in suburban scrub in 1999 and performed arthropod surveys and focal-nest observations in both habitats in 1998 and 1999. In suburban scrub, later hatched nestlings were three times more likely to die before fledging than earlier hatched nestlings, suggesting that brood reduction occurred. In both years, arthropod abundance in the suburban scrub was less than half that of the natural scrub. However, patterns of food delivery by parents were not significantly different between sites, suggesting that lower food abundance does not in itself explain higher partial brood loss in suburban habitat. Differences in the number of helpers, a greater degree of hatching asynchrony or the delivery of lower quality food throughout the nestling period may increase the probability that later hatched nestlings starve in suburban scrub.
Influence of fire, topography, and consumer abundance on seed predation in tallgrass prairie
Authors: Reed Aaron W , Kaufman Glennis A , Kaufman Donald W
Published: January 2005

We assessed seed predation by vertebrates and invertebrates in three fire-frequency treatments (<1 year, 1–4 years, and >4 years since fire) and in three topographic positions (upland, limestone breaks, and lowland) in tallgrass prairie. Two types of seed trays, one for vertebrates and one for invertebrates, were placed in each treatment during each nocturnal and diurnal period. Vertebrates removed significantly more seeds than did invertebrates. Fire frequency and topographic position affected seed removal by both vertebrates and invertebrates. Seed removal by invertebrates was influenced negatively by fire; the greatest seed removal occurred in uplands and lowlands in unburned prairie. Vertebrates removed the most seeds in burned prairie and in lowlands and limestone breaks. Time of day also influenced seed removal by vertebrates, as nocturnal vertebrates (assumed to be rodents) removed more seeds than diurnal vertebrates. Abundance of rodents, however, did not predict accurately seed removal in fire treatments or topographic positions, as rodents removed fewer seeds than expected in prairie that had not been burned in >4 years and in lowlands. This pattern likely was due to the presence of a well-developed plant litter layer in both unburned and lowland habitats, which reduces the likelihood of a rodent locating seeds.