bluuebunny/crossref_metadata_2025 huggingface dataset:
Pathogen adaptation under imperfect vaccination: implications for pertussis
Authors: van Boven Michiel , Mooi Frits R , Schellekens Joop F.P , de Melker Hester E , Kretzschmar Mirjam
Published: July 2005

Mass vaccination campaigns have drastically reduced the burden of infectious diseases. Unfortunately, in recent years several infectious diseases have re-emerged. Pertussis poses a well-known example. Inspired by pertussis, we study, by means of an epidemic model, the population and evolutionary dynamics of a pathogen population under the pressure of vaccination. A distinction is made between infection in immunologically naive individuals (primary infection) and infection in individuals whose immune system has been primed by vaccination or infection (secondary infection). The results show that (i) vaccination with an imperfect vaccine may not succeed in reducing the infection pressure if the transmissibility of secondary infections is higher than that of primary infections; (ii) pathogen strains that are able to evade the immunity induced by vaccination can only spread if escape mutants incur no or only a modest fitness cost and (iii) the direction of evolution depends crucially on the distribution of the different types of susceptibles in the population. We discuss the implications of these results for the design and use of vaccines that provide temporary immunity.
Using the quantitative genetic threshold model for inferences between and within species
Authors: Felsenstein Joseph
Published: July 2005

Sewall Wright's threshold model has been used in modelling discrete traits that may have a continuous trait underlying them, but it has proven difficult to make efficient statistical inferences with it. The availability of Markov chain Monte Carlo (MCMC) methods makes possible likelihood and Bayesian inference using this model. This paper discusses prospects for the use of the threshold model in morphological systematics to model the evolution of discrete all-or-none traits. There the threshold model has the advantage over 0/1 Markov process models in that it not only accommodates polymorphism within species, but can also allow for correlated evolution of traits with far fewer parameters that need to be inferred. The MCMC importance sampling methods needed to evaluate likelihood ratios for the threshold model are introduced and described in some detail.
CreA influences the metabolic fluxes of Aspergillus nidulans during growth on glucose and xylose
Authors: David Helga , Krogh Astrid Mørkeberg , Roca Christophe , Åkesson Mats , Nielsen Jens
Published: July 2005

The physiological phenotype of Aspergillus nidulans was investigated for different genetic and environmental conditions of glucose repression through the quantification of in vivo fluxes in the central carbon metabolism using 13C-metabolic-flux analysis. The particular focus was the role of the carbon repressor CreA, which is the major regulatory protein mediating carbon repression in many fungal species, in the primary metabolism of A. nidulans. Batch cultivations were performed with a reference strain and a deletion mutant strain (creAΔ4) using [1-13C]glucose as carbon source. The mutant strain was also grown on a mixture of [1-13C]glucose and unlabelled xylose. Fractional enrichment data were measured by gas chromatography-mass spectrometry. A model describing the central metabolism of A. nidulans was used in combination with fractional enrichment data, and measurements of extracellular rates and biomass composition for the estimation of the in vivo metabolic fluxes. The creA-mutant strain showed a lower maximum specific growth rate than the reference strain when grown on glucose (0·11 and 0·25 h−1, respectively), whereas the specific growth rate of the mutant strain grown on the glucose/xylose mixture was identical to that on glucose (0·11 h−1). Different patterns and increased levels of extracellular polyols were observed both upon deletion of the creA gene and upon addition of xylose to the growth medium of the mutant strain. Concerning metabolic fluxes, the major change observed in the flux distribution of A. nidulans upon deletion of the creA gene was a 20 % decrease in the flux through the oxidative part of the pentose-phosphate pathway. Addition of xylose to the growth medium of the mutant resulted in an increase of about 40 % in the activity of the oxidative part of the pentose-phosphate pathway, as well as decreases in the fluxes through the Embden–Meyerhof–Parnas pathway and the tricarboxylic acid cycle (in the range of 20–30 %). The derepression of key pathways leads to alterations in the demands for cofactors, thereby imposing changes in the central metabolism due to the coupling of the many different reactions via the redox and energy metabolism of the cells.
Bap-dependent biofilm formation by pathogenic species of Staphylococcus: evidence of horizontal gene transfer?
Authors: Tormo M. Ángeles , Knecht Erwin , Götz Friedrich , Lasa Iñigo , Penadés José R.
Published: July 2005

The biofilm-associated protein (Bap) is a surface protein implicated in biofilm formation by Staphylococcus aureus isolated from chronic mastitis infections. The bap gene is carried in a putative composite transposon inserted in SaPIbov2, a mobile staphylococcal pathogenicity island. In this study, bap orthologue genes from several staphylococcal species, including Staphylococcus epidermidis, Staphylococcus chromogenes, Staphylococcus xylosus, Staphylococcus simulans and Staphylococcus hyicus, were identified, cloned and sequenced. Sequence analysis comparison of the bap gene from these species revealed a very high sequence similarity, suggesting the horizontal gene transfer of SaPIbov2 amongst them. However, sequence analyses of the flanking region revealed that the bap gene of these species was not contained in the SaPIbov2 pathogenicity island. Although they did not contain the icaADBC operon, all the coagulase-negative staphylococcal isolates harbouring bap were strong biofilm producers. Disruption of the bap gene in S. epidermidis abolished its capacity to form a biofilm, whereas heterologous complementation of a biofilm-negative strain of S. aureus with the Bap protein from S. epidermidis bestowed the capacity to form a biofilm on a polystyrene surface. Altogether, these results demonstrate that Bap orthologues from coagulase-negative staphylococci induce an alternative mechanism of biofilm formation that is independent of the PIA/PNAG exopolysaccharide.
Acd, a peptidoglycan hydrolase of Clostridium difficile with N-acetylglucosaminidase activity
Authors: Dhalluin Anne , Bourgeois Ingrid , Pestel-Caron Martine , Camiade Emilie , Raux Gregory , Courtin Pascal , Chapot-Chartier Marie-Pierre , Pons Jean-Louis
Published: July 2005

A gene encoding a putative peptidoglycan hydrolase was identified by sequence similarity searching in the Clostridium difficile 630 genome sequence, and the corresponding protein, named Acd (autolysin of C. difficile) was expressed in Escherichia coli. The deduced amino acid sequence of Acd shows a modular structure with two main domains: an N-terminal domain exhibiting repeated sequences and a C-terminal catalytic domain. The C-terminal domain exhibits sequence similarity with the glucosaminidase domains of Staphylococcus aureus Atl and Bacillus subtilis LytD autolysins. Purified recombinant Acd produced in E. coli was confirmed to be a cell-wall hydrolase with lytic activity on the peptidoglycan of several Gram-positive bacteria, including C. difficile. The hydrolytic specificity of Acd was studied by RP-HPLC analysis and MALDI-TOF MS using B. subtilis cell-wall extracts. Muropeptides generated by Acd hydrolysis demonstrated that Acd hydrolyses peptidoglycan bonds between N-acetylglucosamine and N-acetylmuramic acid, confirming that Acd is an N-acetylglucosaminidase. The transcription of the acd gene increased during vegetative cellular growth of C. difficile 630. The sequence of the acd gene appears highly conserved in C. difficile strains. Regarding deduced amino acid sequences, the C-terminal domain with enzymic function appears to be the most conserved of the two main domains. Acd is the first known autolysin involved in peptidoglycan hydrolysis of C. difficile.
Glutathione-dependent extracellular ferric reductase activities in dimorphic zoopathogenic fungi
Authors: Zarnowski Robert , Woods Jon P.
Published: July 2005

In this study, extracellular glutathione-dependent ferric reductase (GSH-FeR) activities in different dimorphic zoopathogenic fungal species were characterized. Supernatants from Blastomyces dermatitidis, Histoplasma capsulatum, Paracoccidioides brasiliensis and Sporothrix schenckii strains grown in their yeast form were able to reduce iron enzymically with glutathione as a cofactor. Some variations in the level of reduction were noted amongst the strains. This activity was stable in acidic, neutral and slightly alkaline environments and was inhibited when trivalent aluminium and gallium ions were present. Using zymography, single bands of GSH-FeRs with apparent molecular masses varying from 430 to 460 kDa were identified in all strains. The same molecular mass range was determined by size exclusion chromatography. These data demonstrate that dimorphic zoopathogenic fungi produce and secrete a family of similar GSH-FeRs that may be involved in the acquisition and utilization of iron. Siderophore production by these and other fungi has sometimes been considered to provide a full explanation of iron acquisition in these organisms. Our work reveals an additional common mechanism that may be biologically and pathogenically important. Furthermore, while some characteristics of these enzymes such as extracellular location, cofactor utilization and large size are not individually unique, when considered together and shared across a range of fungi, they represent an important novel physiological feature.
Overproduction, purification and characterization of FtmPT1, a brevianamide F prenyltransferase from Aspergillus fumigatus
Authors: Grundmann Alexander , Li Shu-Ming
Published: July 2005

A putative prenyltransferase gene,ftmPT1, was identified in the genome sequence ofAspergillus fumigatus.ftmPT1was cloned and expressed inEscherichia coli, and the protein FtmPT1 was purified to near homogeneity and characterized biochemically. This enzyme was found to catalyse the prenylation ofcyclo-l-trp-l-Pro (brevianamide F) at the C-2 position of the indole nucleus. FtmPT1 is a soluble monomeric protein, which does not contain the usual prenyl diphosphate binding site (N/D)DXXD found in most prenyltransferases, and which does not require divalent metal ions for its enzymic activity.Kmvalues for brevianamide F and dimethylallyl diphosphate were determined as 55 and 74 μM, respectively. The turnover number was 5·57 s−1. FtmPT1 showed a high substrate specificity towards dimethylallyl diphosphate, but accepted different tryptophan-containing cyclic dipeptides. Together with dimethylallyltryptophan synthase of ergot alkaloid biosynthesis, FtmPT1 belongs to a new group of prenyltransferases with aromatic substrates.
Two functional FAS-I type fatty acid synthases in Corynebacterium glutamicum
Authors: Radmacher Eva , Alderwick Luke J. , Besra Gurdyal S. , Brown Alistair K. , Gibson Kevin J. C. , Sahm Hermann , Eggeling Lothar
Published: July 2005

The lipid-rich Corynebacterianeae, to which Corynebacterium glutamicum and Mycobacterium species belong, produce both fatty acids and mycolic acids. Compared with most other bacteria, C. glutamicum possesses two fatty acid synthases, encoded by fasA (8907 kb; FAS-IA) and fasB (8988 kb; FAS-IB). Here, it was shown by mutational analyses that fasA is essential but fasB is not. However, in a fasA background, the fasB mutation results in a slightly reduced growth yield, l-glutamate production is increased, and comparative lipid analysis suggests that in vivo FAS-IB is active primarily to supply palmitate. Transcript quantifications revealed that the fasB transcript contributes 32 % to both fas transcripts during growth on glucose, affirmative for fasB expression, and that fasB is subordinate to fasA. The fasA transcript is downregulated by 8·3-fold during growth on acetate as compared with glucose. The lipid analyses also demonstrate that cells grown on propionate produce a number of uneven fatty acids (e.g. 15 : 0, 17 : 0, 17 : 1), which are not present in cells grown on glucose or acetate, suggesting that fatty acid synthase in vivo may also use propionyl-CoA as the priming unit in fatty acid synthesis. The fatty acid auxotrophic fasAB double mutant was used to determine the suggested incorporation of fatty acids into mycolic acids. Supplementation of this mutant with uniformly labelled [13C]oleate and analysis of isolated mycolic acids confirmed that mature mycolic acids in the mutant consist exclusively of two fused [13C]oleate molecules. In addition to an altered phospholipid profile, the fasB mutant also exhibits differences in its mycolic acid profile. Taken together, the results show that although FAS-IA is the most relevant fatty acid synthase of C. glutamicum and FAS-IB is supplementary, both synthases are necessary to produce the characteristic lipid environment of this organism.
A surface-exposed DraD protein of uropathogenic Escherichia coli bearing Dr fimbriae may be expressed and secreted independently from DraC usher and DraE adhesin
Authors: Zalewska Beata , Piątek Rafał , Bury Katarzyna , Samet Alfred , Nowicki Bogdan , Nowicki Stella , Kur Józef
Published: July 2005

The dra gene cluster, expressed by uropathogenic Escherichia coli strains, determines bacterial attachment and invasion. The Dr fimbrial structures formed at the bacterial cell surface are composed of DraE subunits. The Dr fimbriae-coding cluster contains six open reading frames – draA, draB, draC, draD, draP and draE – among which the draE gene encodes the structural fimbrial subunit DraE. Very little is known about E. coli surface expression of the draD gene product. The expression of DraD and its role in the biogenesis of Dr fimbriae were determined by constructing mutants in the dra operon and by immunoblot and immunofluorescence experiments. In this study, DraD was found to be a surface-exposed protein. The expression of DraD was independent of the DraC usher and DraE fimbrial subunits. Polymerization of DraE fimbrial subunits into fimbrial structures did not require expression of the DraD protein.
Ontogenetic changes of circulating erythroid cells and haemoglobin components in Esox lucius
Authors: Lancioni H. , Lucentini L. , Panara F.
Published: July 2005

Using light microscopy the morphology, the mitotic index and levels of erythroid cell types were detected from 48 h pike Esox lucius embryos before hatching to adult specimens. At the same developmental stages, the haemoglobins and globin chains expressed were electrophoretically characterized. The erythroid cells of the primitive generation were the most abundant from 48 h before hatching until 15–20 days after hatching, then their number decreased and only rare cells remained in the 3 month‐old juvenile specimens. These cells divided and differentiated in the blood and were substituted by the definitive erythrocyte series. As in other vertebrates, the immature cells of the two generations differed in morphological properties and in the synthetized haemoglobin. The circulating erythroid cells of the definitive population cell lineage were, at all differentiation stages, smaller than those of the primitive generation. The definitive erythrocytes appeared in blood smears of 7 days post‐hatching larvae, they increased rapidly and at 20 days they represented the predominant red blood cell population in the circulation of young pike. Electrophoretic analysis of haemolysates obtained from different developmental stages indicated the presence of distinct embryonic, larval and adult haemoglobins. The embryonic haemoglobins differed from those of the older larva and juvenile specimens and were detectable within the first week of post‐hatching development when only primitive erythrocytes were present in the blood.
Assessing mortality changes from size‐frequency curves
Authors: Ostrovsky I.
Published: July 2005

The relationship between the instantaneous mortality rate (Z) and the instantaneous change in length‐frequency distribution of organisms per unit of animal size (μL) takes the following form: Z = μLk(L∞ − L) + k, where k and L∞ are coefficients of the von Bertalanffy equation, and L is organism size (length). Z and μL change coherently when they are measured for a specific size or age class. Therefore, observations of μL can provide information on the relative changes in mortality. This is useful when no precise information about animal growth is available and growth curve is assumed to be invariable. This method was tested on a heavily exploited population of St Peter's fish (mango tilapia)Sarotherodon galilaeus in Lake Kinneret, Israel, where large fluctuations in the size structure of the catch have occurred over the past few years. Analysis of the changes in the length‐frequency distributions showed that the changes in μL over multiple years estimated for fully exploited fish reflected the respective changes in Z.
Non‐destructive ageing in Notolabrus tetricus using dorsal spines with an emphasis on the benefits for protected, endangered and fished species
Authors: Metcalf S. J. , Swearer S. E.
Published: July 2005

Age estimates from clipped dorsal spines were compared to otoliths and scales in the blue throat wrasse Notolabrus tetricus. Dorsal spines provided accurate, non‐destructive ageing and are recommended in favour of destructive methods for conservation purposes.
Otolith elemental fingerprints of juvenile Pacific swordfish Xiphias gladius
Authors: Humphreys R. L. , Campana S. E. , DeMartini E. E.
Published: July 2005

The trace element composition of young‐of‐the‐year (YOY) juvenile swordfish Xiphias gladius sagittal otoliths were analysed as a preliminary test of the value of otolith elemental fingerprints for determining swordfish nursery ground origins in the central Pacific Ocean. A suite of five elements (Mg, Zn, Sr, Ba and Pb) was assayed with isotope dilution ICP‐MS; all elemental concentrations were roughly comparable to otoliths of other marine fishes. Multivariate analyses of elemental fingerprints based on Ba and Sr revealed differences between sample sites, and the magnitude of the differences increased with latitudinal separation. With more comprehensive sampling of nursery grounds, it should be possible to identify origin of nursery ground for adult swordfish by analysing the YOY juvenile portion of the sagittal otolith.
Micromanipulation of single cells from tissue imprints is an alternative to laser‐assisted microdissection
Authors: Brauns Tilmann C. , Goos Manfred
Published: July 2005

Abstract:  The characterization and analysis of single cells by molecular biological methods such as the polymerase chain reaction (PCR) is of increasing interest in biomedical research. Different techniques have been developed to obtain single cells from solid tissue. Currently, the most frequently used technique is laser‐assisted microdissection (LAM). However, LAM of tissues cannot exclude contamination of the targeted cells by underlying cell fragments. Moreover, this technique can only be performed if a laser microscope is available. Thus, we developed a method to obtain single cells of fresh solid tissue by the simple technique of tissue imprints. After immunostaining of the imprints, single cells were transferred to a reaction tube using a 27‐gauge needle guided by a mechanical micromanipulator. Consequently, we used these cells in a single cell PCR.
Minocycline hyperpigmentation isolated to the subcutaneous fat
Authors: Rahman Zakia , Lazova Rossitza , Antaya Richard J.
Published: July 2005

We present a 15‐year‐old girl with bilateral lower extremity discoloration of one‐year duration while taking minocycline for acne vulgaris. The clinical characteristics best supported type II minocycline hyperpigmentation, but the histology revealed that the pigmentation was solely limited to the subcutaneous adipose tissue, completely sparing the dermis. Special stain for iron was negative. This is the first case to our knowledge with pigment exclusively located in the subcutaneous fat and with the unusual finding of a negative stain for iron.
Paired immunoglobulin‐like receptors and their MHC class I recognition
Authors: Takai Toshiyuki
Published: July 2005

The immunoglobulin‐like receptors provide positive and negative regulation of immune cells upon recognition of various ligands, thus enabling those cells to respond properly to extrinsic stimuli. Murine paired immunoglobulin‐like receptor (PIR)‐A and PIR‐B, a typical receptor pair of the immunoglobulin‐like receptor family, are expressed on a wide range of cells in the immune system, such as B cells, mast cells, macrophages and dendritic cells, mostly in a pair‐wise fashion. The PIR‐A requires the homodimeric Fc receptor common γ chain for its efficient cell‐surface expression and for the delivery of an activation signal. In contrast, PIR‐B inhibits receptor‐mediated activation signals in vitro upon engagement with other activating‐type receptors, such as the antigen receptor on B cells and the high‐affinity Fc receptor for immunoglobulin E on mast cells. Recent identification of major histocompatibility complex (MHC) class I molecules as the physiological ligands for PIR has enabled us to attribute various immunological phenotypes observed in PIR‐B‐deficient mice to the consequences of the absence of a balanced interaction between PIR and MHC class I molecules expressed ubiquitously. Thus, PIR‐A and PIR‐B constitute a novel and physiologically important MHC class I recognition system.
Toll‐like receptors‐2, ‐3 and ‐4 expression patterns on human colon and their regulation by mucosal‐associated bacteria
Authors: Furrie Elizabeth , Macfarlane Sandra , Thomson George , Macfarlane George T. ,   Microbiology & Gut Biology Group, Tayside Tissue & Tumour Bank
Published: July 2005

The colonic epithelium provides an interface between the host and micro‐organisms colonising the gastrointestinal tract. Molecular recognition of bacteria is facilitated through Toll‐like receptors (TLR). The colonic epithelium expresses relatively high levels of mRNA for TLR3 and less for TLR2 and ‐4. Little is known of the expression patterns and mode of induction of expression for these pattern recognition receptors in human colon. The aim of this study was to investigate their localization in the gut and induction of expression in epithelial cell lines by mucosal bacteria. TLR2 and ‐4 were expressed only in crypt epithelial cells, expression was lost as the cells matured and moved towards the gut lumen. In contrast, TLR3 was only produced in mature epithelial cells. HT29 and CACO‐2 had different levels of expression for TLR1–4. Co‐culture of HT29 cells with different mucosal isolates showed that they were highly responsive to bacterial challenge, with up‐regulation of mRNA for TLR1–4. In contrast, CACO‐2 cells were refractive to bacterial challenge, showing little difference in mRNA levels. TLR3 was induced in HT29 only by Gram‐positive commensals with up‐regulation of both mRNA and protein and an enhancement of the antiviral immune response. This pattern of expression allows induction of responsiveness to bacteria only by the crypt epithelium so that tolerance to commensal organisms can be maintained. In contrast, mature columnar epithelium is able to respond to viral pathogens, which are not part of the normal gut commensal microbiota.
Necrotizing activity of five Botrytis cinerea endopolygalacturonases produced in Pichia pastoris
Authors: Kars Ilona , Krooshof Geja H. , Wagemakers Lia , Joosten Rob , Benen Jacques A.E. , Van Kan Jan A.L.
Published: July 2005

Five Botrytis cinerea endopolygalacturonase enzymes (BcPGs) were individually expressed in Pichia pastoris, purified to homogeneity and biochemically characterized. While the pH optima of the five enzymes were similar (approximately pH 4.5) the maximum activity of individual enzymes differed significantly. For hydrolysis of polygalacturonic acid (PGA), the Vmax,app ranged from 10 to 900 U mg−1, while the Km,app ranged from 0.16 to 0.6 mg ml−1. Although all BcPGs are true endopolygalacturonases, they apparently have different modes of action. PGA hydrolysis by BcPG1, BcPG2 and BcPG4 leads to the transient accumulation of oligomers with DP < 7, whereas PGA hydrolysis by BcPG3 and BcPG6 leads to the immediate accumulation of monomers and dimers. The necrotizing activity (NA) of all BcPGs was tested separately in tomato, broad bean and Arabidopsis thaliana. They showed different NAs on these plants. BcPG1 and BcPG2 possessed the strongest NA as tissue collapse was observed within 10 min after infiltration of broad bean leaves. The amino acid (aa) D192A substitution in the active site of BcPG2 not only abolished enzyme activity but also the NA, indicating that the NA is dependent on enzyme activity. Furthermore, deletion of the Bcpg2 gene in B. cinerea resulted in a strong reduction in virulence on tomato and broad bean. Primary lesion formation was delayed by approximately 24 h and the lesion expansion rate was reduced by 50–85%. These data indicate that BcPG2 is an important virulence factor for B. cinerea.
Virus‐induced gene silencing in tomato fruit
Authors: Fu Da‐Qi , Zhu Ben‐Zhong , Zhu Hong‐Liang , Jiang Wei‐Bo , Luo Yun‐Bo
Published: July 2005

Virus‐induced gene silencing (VIGS) is a powerful tool for the study of gene function in plants. Here we report that either by syringe‐infiltrating the tobacco rattle virus (TRV)‐vector into the surface, stem or carpopodium of a tomato fruit attached to the plant or by vacuum‐infiltrating into a tomato fruit detached from the plant, TRV can efficiently spread and replicate in the tomato fruit. Although VIGS can be performed in tomato fruit by all of the means mentioned above, the most effective method is to inject the TRV‐vector into the carpopodium of young fruit attached to the plant about 10 days after pollination. Several reporter genes related to ethylene responses and fruit ripening, includingLeCTR1andLeEILsgenes, were also successfully silenced by this method during fruit development. In addition, we found that the silencing of theLeEIN2gene results in the suppression of tomato fruit ripening. The results of our study indicate that the application of VIGS techniques by the described methods can be successfully applied to tomato fruit and is a valuable tool for studying functions of the relevant genes during fruit developing.
ROSINA (RSI), a novel protein with DNA‐binding capacity, acts during floral organ development in Antirrhinum majus
Authors: Roccaro Mario , Li Yubin , Masiero Simona , Saedler Heinz , Sommer Hans
Published: July 2005

Petal and stamen identity of the Antirrhinum majus flower is under the genetic control of the floral homeotic gene DEFICIENS (DEF). To isolate factors involved in the regulation of DEF gene activity, a promoter segment of this B‐function gene, containing cis‐acting regulatory elements, was used to identify the novel trans‐acting factor ROSINA (RSI). RSI does not show an extended similarity with any gene product present in the database. Rather RSI constitutes a protein that contains domains similar to known proteins from organisms of different phyla. The capacity of RSI to bind a sequence element of the DEF promoter, its spatial and temporal expression pattern together with the phenotype of RSI‐RNAi interference plants as well as RSI over‐expression in Arabidopsis thaliana suggest that RSI is a putative regulator of DEF gene activity in A. majus.
Confocal microscopy of whole ovules for analysis of reproductive development: the elongate1 mutant affects meiosis II
Authors: Barrell Philippa J. , Grossniklaus Ueli
Published: July 2005

Analysis of female meiosis (megasporogenesis) and embryo sac development (megagametogenesis) in angiosperms is technically challenging because the cells are enclosed within the nucellus and ovule tissues of the female flower. This is in contrast to male sporogenesis and gametogenesis where development can readily be observed through the easily dissectable developing anthers. Observation of embryo sac development is a particular problem in crassinucellate ovules such as those of maize. To overcome the problems in observing reproductive development, we developed a simple Feulgen staining procedure optimized for use with confocal microscopy to observe reproductive progression in the crassinucellate ovules of maize. The procedure greatly facilitates the observation of nuclei and cell structures of all stages of megasporogenesis and embryo sac development. The high resolution obtained using the technique enabled us to readily visualize chromosomes from individual cells within ovule tissue samples of maize. A propidium iodide staining technique was also used and compared with the Feulgen‐based technique. Static cytometry of relative DNA content of individual nuclei was possible using Imaris software on both Feulgen and propidium iodide‐stained samples. The techniques also proved successful for the observation of Arabidopsis and Hieracium aurantiacum female gametophyte and seed development, demonstrating the general applicability of the techniques. Using both staining methods, we analysed the maize meiotic mutant elongate1, which produces functional diploid instead of haploid embryo sacs. The precise defect in meiosis from which diploid embryo sacs arise in elongate1 has not previously been reported. We used confocal microscopy followed by static cytometry using Imaris software to show that the defect by which diploid embryo sacs arise in the maize mutant elongate1 is the absence of meiosis II with one of the dyad cells directly initiating megagametogenesis.
The role of abiotic conditions in shaping the long‐term patterns of a high‐elevation Argentine ant invasion
Authors: Krushelnycky Paul D. , Joe Stephanie M. , Medeiros Arthur C. , Daehler Curtis C. , Loope Lloyd L.
Published: July 2005

Analysis of long‐term patterns of invasion can reveal the importance of abiotic factors in influencing invasion dynamics, and can help predict future patterns of spread. In the case of the invasive Argentine ant (Linepithema humile), most prior studies have investigated this species’ limitations in hot and dry climates. However, spatial and temporal patterns of spread involving two ant populations over the course of 30 years at a high elevation site in Hawaii suggest that cold and wet conditions have influenced both the ant's distribution and its rate of invasion. In Haleakala National Park on Maui, we found that a population invading at lower elevation is limited by increasing rainfall and presumably by associated decreasing temperatures. A second, higher elevation population has spread outward in all directions, but rates of spread in different directions appear to have been strongly influenced by differences in elevation and temperature. Patterns of foraging activity were strongly tied to soil temperatures, supporting the hypothesis that variation in temperature can influence rates of spread. Based on past patterns of spread, we predicted a total potential range that covers nearly 50% of the park and 75% of the park's subalpine habitats. We compared this rough estimate with point predictions derived from a degree‐day model for Argentine ant colony reproduction, and found that the two independent predictions match closely when soil temperatures are used in the model. The cold, wet conditions that have influenced Argentine ant invasion at this site are likely to be influential at other locations in this species’ current and future worldwide distribution.
Increased resistance to generalist herbivores in invasive populations of the California poppy (Eschscholzia californica)
Authors: Leger Elizabeth A. , Forister Matthew L.
Published: July 2005

Escape from enemies in the native range is often assumed to contribute to the successful invasion of exotic species. Following optimal defence theory, which assumes a trade‐off between herbivore resistance and plant growth, some have predicted that the success of invasive species could be the result of the evolution of lower resistance to herbivores and increased allocation of resources to growth and reproduction. Lack of evidence for ubiquitous costs of producing plant toxins, and the recognition that invasive species may escape specialist, but not generalist enemies, has led to a new prediction: invasive species may escape ecological trade‐offs associated with specialist herbivores, and evolve increased, rather than decreased, production of defensive compounds that are effective at deterring generalist herbivores in the introduced range. We tested the performance of two generalist lepidopteran herbivores, Trichoplusia ni and Orgyia vetusta, when raised on diets of native and invasive populations of the California poppy, Eschscholzia californica. Pupae of T. ni were significantly larger when reared on native populations. Similarly, caterpillars of O. vetusta performed significantly better when raised on native populations, indicating that invasive populations of the California poppy are more resistant to herbivores than native populations. The chance of successful establishment of some non‐indigenous plant species may be increased by retaining resistance to generalist herbivores, and in some cases, invasive species may be able to escape ecological trade‐offs in their new range and evolve, as we observed, even greater resistance to generalist herbivores than native plants.
Determinants for the successful establishment of exotic ants in New Zealand
Authors: Lester Philip J.
Published: July 2005

Biological invasions can dramatically alter ecosystems. An ability to predict the establishment success for exotic species is important for biosecurity and conservation purposes. I examine the exotic New Zealand ant fauna for characteristics that predict or determine an exotic species’ ability to establish. Quarantine records show interceptions of 66 ant species: 17 of which have established, 43 have failed to establish, whereas nests of another six are periodically observed but have failed to establish permanently (called ‘ephemeral’ establishment). Mean temperature at the highest latitude and interception variables were the only factors significantly different between established, failed or ephemeral groups. Aspects of life history, such as competitive behaviour and morphology, were not different between groups. However, in a stepwise discriminant analysis, small size was a key factor influencing establishment success. Interception rate and climate were also secondarily important. The resulting classification table predicted establishment success with 71% accuracy. Because not all exotic species are represented in quarantine records, a further discriminant model is described without interception data. Though with less accuracy (65%) than the full model, it still correctly predicted the success or failure of four species not used in the previous analysis. Techniques for improving the prediction accuracy are discussed. Predicting which species will establish in a new area appears an achievable goal, which will be a valuable tool for conservation biology.
Visualizing environmental correlates of species geographical range limits
Authors: Bauer John T. , Peterson A. Townsend
Published: July 2005

Although many studies have treated aspects of species geographical distributions and numerous approaches exist for understanding overall ecological correlates of distributions, software tools for exploring environmental correlates of distributional limits are relatively few. We focused on the challenge of understanding spatial correlates of distributional limits, and developed an extension to arcview that provides a simple, univariate test and visualization for such explorations. The ‘Boundary U‐test’ seeks out environmental variables that show steep gradients associated with user‐defined boundaries across geography. We illustrate the tool and its applications with an example of the likely historical distribution of Mexican wolf (Canis lupus).
An independent confirmation of a quantitative trait locus for milk yield and composition traits on bovine chromosome 26
Authors: Jiang Z. , De S. , Garcia M.D. , Griffin K.B. , Wu X.‐L. , Xiao Q. , Michal J.J. , Sharma B.S. , Jansen G.B.
Published: July 2005

Several reports have demonstrated that bovine chromosome 26 (BTA26) harbours significant or suggestive quantitative trait loci (QTL) for milk production and composition traits in dairy cattle. Our previous study showed that a C/T substitution in the bovine TCF7L2 gene on BTA26 was significantly linked to QTL for protein yield (PY) in a Canadian dairy cattle population. Actually, this polymorphism was one of the markers derived from a genome‐wide screening of QTL for milk PY using an amplified fragment length polymorphism technique combined with a DNA pooling strategy. In the present study, 990 Holstein bulls with complete genotype and phenotype data from 14 sire families were analysed to confirm, if the QTL effects exist in other populations. Statistical analysis revealed that this marker was significantly associated with PY, protein percentage, milk yield and fat yield (FY) (p < 0.001) in the US Holstein population. These results indicate that this QTL region has a pleiotrophic effect on different milk traits and is portable in different populations.
Case of non‐involuting congenital haemangioma
Authors: Matulich Jacqueline , Wood Glenda , Sugo Ella
Published: July 2005

A 4‐year‐old boy presented with a congenital vascular tumour behind his right ear. It had remained unchanged since birth and was asymptomatic. The parents sought a diagnosis and treatment. Doppler ultrasonography demonstrated a fast‐flow, lobulated vascular mass. Histology showed features of a non‐involuting congenital haemangioma. Glucose transporter‐1 staining was negative. The tumour was surgically excised without complication and has not recurred.
Lichen striatus in a pregnant woman
Authors: Brennand Sarah , Khan Sant , Chong Alvin H
Published: July 2005

We report a case of lichen striatus in a 37‐year‐old woman in the third trimester of pregnancy. She presented at 35 weeks of pregnancy with a 6‐week history of a pruritic rash on the left side of her abdomen. Examination revealed an erythematous papular eruption arranged in a linear fashion from the umbilicus to the left mid back. Histological examination demonstrated lichenoid perivascular and periadnexal inflammatory infiltrate and the presence of colloid bodies. The eruption resolved prior to delivery with the application of mometasone furoate 0.1% ointment.
Abdominal wall ulceration and mucinosis secondary to recombinant human interferon‐β‐1b
Authors: Wells Jillian , Kossard Steven , McGrath Michael
Published: July 2005

A 46‐year‐old woman developed painful ulcers over her lower abdomen in the form of reticulate erythema after injecting interferon β‐1b subcutaneously for multiple sclerosis. Skin biopsy revealed multiple superficial thrombosed vessels with focal epidermal necrosis as well as prominent interstitial mucinosis. Treatment with low‐molecular‐weight heparin followed by a heparinoid resulted in slow healing of the ulcers but also allowed the subcutaneous interferon injections to be continued.
The ketogenic diet in refractory childhood epilepsy
Authors: Mackay Mark T , Bicknell‐Royle Jillian , Nation Judy , Humphrey Maureen , Harvey A Simon
Published: July 2005

Objective: To report the efficacy and tolerability of the ketogenic diet (KD) in refractory paediatric epilepsy.

Methods: Twenty‐six consecutive children were treated with the classical KD from 1996 to 2001. The epilepsy syndromes included symptomatic generalized epilepsy (15), idiopathic generalized epilepsy (4), symptomatic partial epilepsy (1) and unclassified epilepsy (6). One child was lost to follow up.

Results: Median age at initiation of the KD was 6.1 years. Median duration of the treatment was 9 months. Twelve children (48%) were treated for >12 months; one still remains on the KD. Four children (16%) became seizure‐free. Five children (20%) had 50–99% reduction in seizures, seven (28%) had <50% reduction in seizures and eight (36%) had no improvement. Age, seizure‐type and aetiology did not predict response. The medications were decreased in 33% of the children. The KD was discontinued in 64% of the children because of poor efficacy and in 12% because of side‐effects. Problems during initiation of the KD included asymptomatic hypoglycaemia (24%) and vomiting (12%). Later complications included poor growth (20%), hyperlipidaemia (16%), hypercalcuria (8%), hypocarnitaemia (8%), constipation (8%), pancreatitis (4%) and decreased bone density (4%). There were no deaths. A 3‐month trial of the KD costs $A3879. The first 12 months cost $A7275 with a cost of $A4528 each year, thereafter.

Conclusions: The KD is an effective treatment for some children with refractory epilepsy, being generally well tolerated and rarely associated with side‐effects. Response is not necessarily predicted by age, syndrome or aetiology. A prospective study of the KD is presently underway.
Neonatal nasal obstruction and a single maxillary central incisor
Authors: Levison John , Neas Katherine , Wilson Meredith , Cooper Peter , Wojtulewicz Julian
Published: July 2005

Abstract:  We present two neonates with nasal obstruction because of anterior choanal stenosis (congenital nasal pyriform aperture stenosis). An associated single maxillary central incisor was also shown on computed tomography imaging in the neonatal period. These midline anomalies are recognized minimal manifestations (microforms) of holoprosencephaly. We describe their neonatal investigation, multidisciplinary management and clinical course.
Case of live birth in a non‐communicating rudimentary horn pregnancy
Authors: Shin Jin Woo , Kim Hai Joong
Published: July 2005

Pregnancy in the rudimentary horn is an extremely rare condition. This report describes an unusual pregnancy in the rudimentary horn, which was misdiagnosed as a bicornuate uterine pregnancy on early obstetric sonogram. The pregnancy was successfully delivered using cesarean section, with both neonatal and maternal survival.
Linking litter calcium, earthworms and soil properties: a common garden test with 14 tree species
Authors: Reich Peter B. , Oleksyn Jacek , Modrzynski Jerzy , Mrozinski Pawel , Hobbie Sarah E. , Eissenstat David M. , Chorover Jon , Chadwick Oliver A. , Hale Cynthia M. , Tjoelker Mark G.
Published: July 2005

Tree species can influence biogeochemistry through variation in the quantity and chemistry of their litter, and associated impacts on the soil heterotrophic community. However, the role that different plant traits play in these processes is not well understood, nor is it clear whether species effects on soils largely reflect a gymnosperm vs. angiosperm contrast. Using a replicated, long‐term monoculture plot experiment, we examined variation in soils among 14 gymnosperm and angiosperm tree species 30 years after plot establishment, and assessed the role of litter chemistryvis‐à‐vissuch variation. Differences in litter calcium concentrations among tree species resulted in profound changes in soil acidity and fertility that were similar within and among tree groups. Tree species rich in calcium were associated with increased native earthworm abundance and diversity, as well as increased soil pH, exchangeable calcium, per cent base saturation and forest floor turnover rate.
Allee effects in biological invasions
Authors: Taylor Caz M. , Hastings Alan
Published: July 2005

Understanding the dynamics of small populations is obviously important for declining or rare species but is also particularly important for invading species. The Allee effect, where fitness is reduced when conspecific density is low, can dramatically affect the dynamics of biological invasions. Here, we summarize the literature of Allee effects in biological invasions, revealing an extensive theory of the consequences of the Allee effect in invading species and some empirical support for the theory. Allee effects cause longer lag times, slower spread and decreased establishment likelihood of invasive species. Expected spatial ranges, distributions and patterns of species may be altered when an Allee effect is present. We examine how the theory can and has been used to detect Allee effects in invasive species and we discuss how the presence of an Allee effect and its successful or unsuccessful detection may affect management of invasives. The Allee effect has been shown to change optimal control decisions, costs of control and the estimation of the risk posed by potentially invasive species. Numerous ways in which the Allee effect can influence the efficacy of biological control are discussed.
Aerobic methane oxidation and methanotroph community composition during seasonal stratification in Mono Lake, California (USA)
Authors: Carini Stephen , Bano Nasreen , LeCleir Gary , Joye Samantha B.
Published: July 2005

Patterns of aerobic methane (CH4) oxidation and associated methanotroph community composition were investigated during the development of seasonal stratification in Mono Lake, California (USA). CH4 oxidation rates were measured using a tritiated CH4 radiotracer technique. Fluorescence in situ hybridization (FISH), denaturing gradient gel electrophoresis (DGGE) and sequence analysis were used to characterize methanotroph community composition. A temporally shifting zone of elevated CH4 oxidation (59–123 nM day−1) was consistently associated with a suboxycline, microaerophilic zone that migrated upwards in the water column as stratification progressed. FISH analysis revealed stable numbers of type I (4.1–9.3 × 105 cells ml−1) and type II (1.4–3.4 × 105 cells ml−1) methanotrophs over depth and over time. Denaturing gradient gel electrophoresis and sequence analysis indicated slight shifts in methanotroph community composition despite stable absolute cell numbers. Variable CH4 oxidation rates in the presence of a relatively stable methanotroph population suggested that zones of high CH4 oxidation resulted from an increase in activity of a subset of the existing methanotroph population. These results challenge existing paradigms suggesting that zones of elevated CH4 oxidation activity result from the accumulation of methanotrophic biomass and illustrate that type II methanotrophs may be an important component of the methanotroph population in saline and/or alkaline pelagic environments.
Island size and bacterial diversity in an archipelago of engineering machines
Authors: Van Der Gast Christopher J. , Lilley Andrew K. , Ager Duane , Thompson Ian P.
Published: July 2005

There is an increasing realization that progress in bacterial ecology can be further advanced by applying theories and models developed in ecology. Consequently, there is a significant need to assess the applicability of such tools, developed specifically for macroorganisms, for investigating the underlying issues that determine bacterial diversity and community assemblage. In this study, we employed the island biogeography species–area model, originally conceived to assess colonization of islands by macroorganisms, to assess bacterial communities colonizing metal‐cutting fluids from machines of increasing sump tank size, taking these to be analogous to islands of variable size. This system was selected because it is well studied and compared with other natural bacterial communities has a relatively low (manageable) diversity. Our findings show that island biogeography theory holds for the bacterial communities studied, in that smaller sump tanks contained lower and putatively less stable diversity, and larger sumps had greater diversity and were temporally stable. It was found that the calculated power law indices (i.e. z‐values) were similar for all sample sets, and strikingly, typical of those observed in classical ecology. This was not expected as bacteria have significant distinguishing features such as huge population sizes, rapid asexual reproduction and small body size that facilitate dispersal, and are particularly resistant to extinction.