bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploration off surface‐textures in congenitally blind infants
Authors: Schellingerhout R , Smitsman A W , van Galen G P
Published: March 2007

The haptic exploratory procedures that eight congenitally blind infants aged 8–24 months used to explore a gradient surface texture were investigated. Exploration of the gradient texture was examined over five sessions with 2 weeks between sessions, followed after 1 week by a sixth session, in which exploration of the gradient texture was compared to exploration of two other textures. Results showed that the infants have a wide range of exploratory strategies available and that the older infants can use these strategies in a specific manner. Results are discussed with reference to current ideas about the exploratory possibilities of congenitally blind infants. Use of texture in the stimulation of exploration of blind infants is discussed.
Selective eaters: a retrospective case note study
Authors: Timimi S , Douglas J , Tsiftsopoulou K
Published: March 2007

The literature on children who present with selective eating is limited to single case studies. This study aims to provide a descriptive clinical profile for these children. Case notes of 33 patients between 4 and 14 years of age, seen in two clinics over a 4‐year‐period were studied. Over two‐thirds of the cases were boys. A significant minority had poor growth or weight gain. The children suffered from anxiety, obsessive compulsive symptoms, both food and non‐food related and often had social and school difficulties. Mealtimes caused immense anxiety for family members and frequent mealtime battles was reported by the parents of the younger selective eaters, whereas parents of older children seemed to have given up trying to change their child's eating habits. A history of depression In at least one parent was found in a third of the parental couples.
ADMA is independently related to flow‐mediated vasodilation in subjects at low cardiovascular risk
Authors: Ardigo D. , Stüehlinger M. , Franzini L. , Valtueña S. , Piatti P. M. , Pachinger O. , Reaven G. M. , Zavaroni I.
Published: March 2007

Background  Increased plasma concentrations of asymmetric dimethylarginine (ADMA) contribute to impair endothelial function in patients with established cardiovascular disease (CVD) and/or individuals with clinical syndromes known to increase CVD. However, the impact of ADMA on endothelial function in apparently healthy individuals has not been determined.

Materials and methods  To address this issue, we measured endothelial‐dependent vasodilatation in response to forearm ischaemia (flow‐mediated vasodilatation, FMD) in 111 non‐smoking, healthy volunteers with low CVD risk by the Framingham risk equation. Measurements were also made of multiple anthropometric, metabolic, and dynamic variables related to FMD. l‐arginine and its methylated derivates (ADMA and SDMA) were quantified by high‐liquid pressure chromatography.

Results  After adjustment by gender, lower values for FMD were significantly associated with increases in plasma ADMA concentrations (anova linear trend by FMD tertiles, P < 0·05) as well as in brachial artery diameter (partial r = −0·352, P = 0·001), body mass index (−0·337, P = 0·001), fasting insulin (−0·368, P < 0·001) and high‐sensitivity C‐reactive protein (−0·283, P = 0·007) plasma concentrations, and with decreased HDL cholesterol (0·233, P = 0·026). Multiple linear regression analysis indicated that the only statistically significant predictors of FMD were brachial artery diameter (P < 0·001), ADMA (P < 0·05) and fasting plasma insulin (P < 0·001) concentrations.

Conclusions  In conclusion, a significant relationship between increases in plasma ADMA concentration and lower values of FMD is not limited to patients with clinical syndromes related to CVD, but can also be seen in healthy subjects at low global CVD risk.
Sources of variation in winter basal metabolic rate in the great tit
Authors: BROGGI J. , HOHTOLA E. , KOIVULA K. , ORELL M. , THOMSON R. L. , NILSSON J.‐Å.
Published: March 2007

Basal metabolic rate (BMR) is the most widely used standard measurement of the cost of living. Despite the acknowledged phenotypic flexibility of BMR, little is known about the patterns of variation in wild animal populations.

We studied the sources of variation in BMR of great titParus major(L.) among individuals from two wild populations: Oulu (northern Finland) and Lund (southern Sweden) during six consecutive years.

By means of a multivariate approach, we found year, locality, date, previous week average minimum temperature, age, body mass, and the interaction between locality and year were the factors retained in the final model, together explaining 71·1% of the total variation in BMR.

Birds from Oulu (n = 168) had a higher BMR than Lund birds (n = 156), and their BMR varied more between years than that of Lund birds. The two populations reacted in the same way to the other sources of variation examined.

Great tits from both populations showed a positive relationship between BMR and body mass and a negative relationship between BMR and date, previous week average minimum temperature and age.

This study highlights the need to standardize BMR measurements when testing predictions about metabolic rates from individuals of wild populations.
Spectrum of mutations in Albanian patients with haemophilia A: identification of ten novel mutations in the factor VIII gene
Authors: CASTAMAN G. , GIACOMELLI S. H. , GHIOTTO R. , BOSEGGIA C. , POJANI K. , BULO A. , MADEO D. , RODEGHIERO F.
Published: March 2007

Summary.  Genetic analysis was carried out in 37 Albanian patients with haemophilia A. The factor VIII intron 22 inversion was detected only in 2/19 (10.5%) apparently unrelated patients with severe haemophilia A, while the intron 1 inversion was absent. A total of 19 different gene mutations were identified. Ten mutations were novel: four null mutations in severe haemophilia A patients (Gln1090X, Cys1832X, 2374delT, 5676insT) and six missense mutations (five in severe haemophilia A) (Ile76Thr, Leu299Pro, Asp525Glu, Cys692Tyr, His1755Leu and Trp1835Cys). None of these novel mutations occurred at CpG hotspots. These results further emphasize the extreme heterogeneity of the molecular basis of haemophilia A. The low prevalence of intron 22 inversion in Albanian patients with severe haemophilia A should be addressed by further studies.
The role of MSX1 in tooth agenesis in Iranians
Authors: SEIFI MASSOUD , KAZEMI BAHRAM , GOLKAR PARISA
Published: March 2007

Introduction.  MSX1 gene has a critical role in craniofacial development, the aim of this case–control study is to test the hypothesis that MSX1 mutation contributes to congenital tooth agenesis in Iranians.

Materials and methods.  The study group consisted of 20 affected individuals with tooth agenesis of lower second premolars or upper lateral incisors with mean age of 24.6. The control group consisted of 20 unaffected individuals. DNA was extracted from all 40 individuals; the polymerase chain reaction (PCR) for MSX1 was carried out with Phenol: Chloroform: Isoamylalchol (PCI) extraction method. Ban II restriction digest and agarose gel electrophoresis of the 20 affected individuals verified the presence of mutation in all 20 affected individuals. The unaffected controls did not show any mutation. Statistical analysis performed by the chi‐squared method.

Results.  Ban II did not digest PCR product (DNA) in the control group (195 bp band on electrophoresis gel) but digested the affected allele (106 bp and 89 bp bands). There is a statistically significant correlation between tooth agenesis and MSX1 mutation (P < 0.001).

Conclusion.  The results indicated that MSX1 gene mutation contributes to tooth agenesis in Iranian individuals. As the timing of tooth calcification can vary, radiographic finding of congenital tooth agenesis can be confirmed by this molecular method during different dental ages to achieve certainty.
The distribution of purse‐web Atypus spiders (Araneae: Mygalomorphae) in central Europe is constrained by microclimatic continentality and soil compactness
Authors: Řezáč Milan , Řezáčová Veronika , Pekár Stano
Published: March 2007

Aim  Three species of primitive spiders of the genus Atypus occur in European xerothermic habitats, where they live in burrows. The aim of this study is to explain their distribution by investigating environmental variables at sites where they occur in central Europe.

Location  Over 50 sites in central Europe, Czech Republic.

Methods  Data on climatic, edaphic and vegetational parameters were collected from more than 50 sites. Phytocenological data were processed using Ellenberg's indicator values.

Results  Atypus muralis was found to occur almost exclusively in dry grassland (Festucion valesiacae), exposed to a continental microclimate. Atypus affinis usually occurred in dry sparse forests (Genisto germanicae–Quercion) that provide an Atlantic microclimate. Atypus piceus occurred in dry grassland (Bromion erecti) or forest fringes (Geranion sanguinei) characterized by an intermediate microclimate. Atypus piceus and A. muralis were restricted to agglutinate calcareous soils.

Main conclusions  Our results show that Atypus species colonized sites with different continentality in central Europe. These differences correspond to differences among their probable glacial refugia. Atypus muralis and A. piceus occur in habitats with a markedly continental climate, and are restricted to calcareous agglutinate soils that more efficiently buffer temperature and humidity extremes. Habitats of A. muralis and A. piceus are threatened by overgrowth of vegetation after a recent decline in grazing and by the decalcification of the landscape. However, habitats of A. affinis are stable in the present central European climate.
Student dietitians’ attitudes towards research and audit: a comparison with registered dietitians
Authors: Whelan K. , Madden A. M. , Thomas J. E.
Published: March 2007

Background

Student dietitians’ attitudes towards research and audit are important as they are likely to influence their subsequent involvement in such activities once qualified. The aim of this study was to investigate the attitudes of student dietitians towards research and audit and to compare them with those of registered dietitians previously reported.

Methods

A questionnaire survey of final‐year student dietitians’ attitudes towards research and audit was conducted. Students indicated their agreement with 12 statements relating to research and audit and the results were compared with those from an identical survey of registered dietitians.

Results

A total of 110 questionnaires were completed (87% response rate). In general, students had positive attitudes towards research and audit. The majority (91%) agreed that ‘all dietitians should be able to act on research’, whilst only a small minority agreed that research (6%) and audit (4%) was ‘not part of a dietitian's role’. In general, students had more positive attitudes towards research, and less positive attitudes towards audit, than dietitians from a previously published survey.

Discussion

Final year student dietitians have positive attitudes towards research and audit. These should be nurtured throughout the early years of their career in order to maximize on their research potential.
Changes in diet quality score, macro‐ and micronutrients intake following a nutrition education intervention in postmenopausal women
Authors: Manios Y. , Moschonis G. , Katsaroli I. , Grammatikaki E. , Tanagra S.
Published: March 2007

Introduction

The aim of the current study was to assess the effectiveness of a nutrition education programme on post‐menopausal women using self‐reported nutrient intake data as well as a qualitative data obtained by the Healthy Eating Index (HEI).

Materials and methods

Seventy‐five women (55–65 years old) were randomized to a dietary intervention group (IG: n = 39), attending regular nutrition education sessions for 5 months and to a control group (CG: n = 36). The intervention scheme was based on a combined application of the Health Belief Model and the Social Cognitive Theory, aiming to increase nutritional knowledge and self‐efficacy of the subjects to adopt and maintain healthy dietary choices. Changes in self‐reported macro‐ and micronutrients’ intake as well as in the HEI total score and in its ten components were obtained.

Results

The IG subjects reported increasing their milk (P < 0.001) and total fat (P = 0.01) HEI scores, decreasing total fat intake (P = 0.050) and increasing calcium and vitamin D intakes (P < 0.001 respectively) to a higher extent compared with the changes reported by the CG.

Conclusion

The current nutrition education programme appears to have induced favourable changes for the IG in micronutrients’ intake primarily related to bone health and in total fat intake. These changes were reflected in the individual HEI indices but not in total HEI score.
Automatic thresholding of three‐dimensional microvascular structures from confocal microscopy images
Authors: SMITH CYNTHIA M. , COLE SMITH J. , WILLIAMS STUART K. , RODRIGUEZ JEFFREY J. , HOYING JAMES B.
Published: March 2007

We have combined confocal microscopy, image processing, and optimization techniques to obtain automated, accurate volumetric measurements of microvasculature. Initially, we made tissue phantoms containing 15‐μm FocalCheck™ microspheres suspended in type I collagen. Using these phantoms we obtained a stack of confocal images and examined the accuracy of various thresholding schemes. Thresholding algorithms from the literature that utilize a unimodal histogram, a bimodal histogram, or an intensity and edge‐based algorithm all significantly overestimated the volume of foreground structures in the image stack. Instead, we developed a heuristic technique to automatically determine good‐quality threshold values based on the depth, intensity, and (optionally) gradient of each voxel. This method analyzed intensity and gradient threshold methods for each individual image stack, taking into account the intensity attenuation that is seen in deeper images of the stack. Finally, we generated a microvascular construct comprised of rat fat microvessel fragments embedded in collagen I gels and obtained stacks of confocal images. Using our new thresholding scheme we were able to obtain automatic volume measurements of growing microvessel fragments.
A simple method for evaluation of tongue position
Authors: TSUIKI S. , HANDA S. , OHYAMA K.
Published: March 2007

summary  Neck extension because of contraction of cervical extensor muscles often brings about a lower‐positioned tongue secondary to jaw opening in patients with congenital myopathy (CM). We hypothesized that neck extension in control subjects would reproduce the lower position of the tongue similar to that found in a CM patient. A simple method was formulated to evaluate the tongue position in terms of tongue pressure on the maxillary molar. A pair of pressure sensors was attached to the buccal and lingual surfaces of the upper molar for both the CM patient and four control subjects. Changes in the buccal and tongue pressures were recorded at the neck extension position for the CM patient and during both the natural head position and neck extension for the control subjects. There was a remarkable difference between buccal and tongue pressures in the neck extension position in the CM patient: tongue pressure was not detected at all, indicating there was no contact between tongue and upper molar. The buccal and tongue pressures were approximately equal in the natural head position in the control subjects. However, both buccal and tongue pressures were reduced during neck extension in the control subjects, with a greater decrease in the tongue pressure than the buccal pressure. These findings suggest that neck extension in a control subject reproduces the lower position of the tongue observed in CM patients. We propose that the pressure sensor enables evaluation of the tongue position, but further investigation is required.
Maxillofacial rehabilitation after rhinectomy using two different treatment options: clinical reports
Authors: CIOCCA L. , MAREMONTI P. , BIANCHI B. , SCOTTI R.
Published: March 2007

summary  The aim of these clinical reports was to describe two different approaches to prosthetic rehabilitation after facial disfigurement because of a total rhinectomy. A man with a total rhinectomy was scheduled for craniofacial implants in the nasal residual defect. Three oral implants were used instead of craniofacial ones. A conventional framework was designed to connect the prosthesis to the implant abutments in the anterior nasal floor, and a custom‐made ball attachment was positioned in the glabella abutment. A woman with a free rectum abdomis flap covering the defect of the middle face was scheduled for a nasal prosthesis. A titanium framework with a novel connection between the eyeglasses and the prosthesis was manufactured. The two clinical reports presented in this article illustrate favourable clinical treatment outcomes in the rehabilitation of disfigurement.
Faunistic study of sandflies in Greece
Authors: IVOVIĆ V. , PATAKAKIS M. , TSELENTIS Y. , CHANIOTIS B.
Published: March 2007

Abstract A faunistic study of phlebotomine sandflies was carried out on the mainland and on four islands in Greece between 1999 and 2004. Sandflies were collected in 18 areas, and the population structure was observed and recorded. A total of 10 species were identified; their distribution is presented here. Of these, the species Phlebotomus neglectus Tonnoir and P. perfiliewi Parrot (Diptera: Psychodidae), epidemiologically the most important vectors of leishmaniases and sandfly fever in Greece, were shown to be present in the main endemic foci of the country.
Less is more: restricted application of insecticide to cattle to improve the cost and efficacy of tsetse control
Authors: TORR S. J. , MAUDLIN I. , VALE G. A.
Published: March 2007

AbstractStudies were carried out in Zimbabwe of the responses of tsetse to cattle treated with deltamethrin applied to the parts of the body where most tsetse were shown to land. Large proportions ofGlossina pallidipesAusten (Diptera: Glossinidae) landed on the belly (∼ 25%) and legs (∼ 70%), particularly the front legs (∼ 50%). Substantial proportions ofGlossina morsitans morsitansWestwood landed on the legs (∼ 50%) and belly (25%), with the remainder landing on the torso, particularly the flanks (∼ 15%). Studies were made of the knockdown rate of wild, femaleG. pallidipesexposed to cattle treated with a 1% pour‐on or 0.005% suspension concentrate of deltamethrin applied to the (a) whole body, (b) belly and legs, (c) legs, (d) front legs, (e) middle and lower front legs, or (f) lower front legs. The restricted treatments used 20%, 10%, 5%, 2% or 1% of the active ingredient applied in the whole‐body treatments. There was a marked seasonal effect on the performance of all treatments. With the whole‐body treatment, the persistence period (knockdown > 50%) ranged from ∼ 10 days during the hot, wet season (mean daily temperature > 30 °C) to ∼ 20 days during the cool, dry season (< 22 °C). Restricting the application of insecticide reduced the seasonal persistence periods to ∼ 10–15 days if only the legs and belly were treated, ∼ 5–15 days if only the legs were treated and < 5 days for the more restricted treatments. The restricted application did not affect the landing distribution of tsetse or the duration of landing bouts (mean = 30 s). The results suggest that more cost‐effective control of tsetse could be achieved by applying insecticide to the belly and legs of cattle at 2‐week intervals, rather than using the current practice of treating the whole body of each animal at monthly intervals. This would cut the cost of insecticide by 40%, improve efficacy by 27% and reduce the threats to non‐target organisms and the enzootic stability of tick‐borne diseases.
Development of an odour‐baited target for female New World screwworm, Cochliomyia hominivorax: studies with host baits and synthetic wound fluids
Authors: CORK A. , HALL M. J. R.
Published: March 2007

Abstract Field studies were conducted in Mexico to investigate the possibility of replacing sentinel animals as baits for female New World screwworm Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae) with a synthetic odour‐bait composed of compounds identified from wounds infested with the larvae of C. hominivorax. Studies using sheep held in stanchions surrounded by an incomplete ring of electrified nets showed that both male and female C. hominivorax were attracted to an unwounded animal (ratio of male : female flies caught 1.11 : 1.00), although they were not observed to land. By contrast, catches associated with unwounded sheep with larval wound fluid applied to shaven shoulders suggested that female C. hominivorax were attracted to (male : female ratio of electrified nets catch 0.14 : 1.00) and landed on the wound fluid but male flies did not respond (male : female ratio alighting on fluid 0.05 : 1.00). In related studies the attractiveness of synthetic blends of 25 electrophysiologically active compounds identified in fluids associated with wounds infested with the larvae of C. hominivorax were tested. The acidic components of the wound fluids were found to attract and elicit a landing response from both male and female flies, whereas the non‐acidic components alone caught only low numbers of flies. However, the numbers of male and female flies that were attracted to and landed on a synthetic bait could be increased significantly by increasing the proportion of non‐acid to acid components in the lure. In some replicates the most effective blend caught a number of C. hominivorax comparable to that caught by a standard synthetic attractant, Swormlure‐4, although, unlike with Swormlure‐4, the catch was predominately composed of female flies. It is uncertain whether Swormlure‐4 contains compounds that elicit a landing response from male C. hominivorax or whether the synthetic and natural wound odours contain compounds that inhibit a landing response from male C. hominivorax. Further work is required to simplify the blend of compounds needed to attract female flies and to better understand the role of the compounds that elicit behavioural responses from both male and female C. hominivorax before a synthetic substitute can be fully developed to replace sentinel animals.
Using COI barcodes to identify forensically and medically important blowflies
Authors: NELSON L. A. , WALLMAN J. F. , DOWTON M.
Published: March 2007

Abstract The utility of cytochrome oxidase I (COI) DNA barcodes for the identification of nine species of forensically important blowflies of the genus Chrysomya (Diptera: Calliphoridae), from Australia, was tested. A 658‐bp fragment of the COI gene was sequenced from 56 specimens, representing all nine Chrysomya species and three calliphorid outgroups. Nucleotide sequence divergences were calculated using the Kimura‐two‐parameter distance model and a neighbour‐joining (NJ) analysis was performed to provide a graphic display of the patterns of divergence among the species. All species were resolved as reciprocally monophyletic on the NJ tree. Mean intraspecific and interspecific sequence divergences were 0.097% (range 0–0.612%, standard error [SE] = 0.119%) and 6.499% (range 0.458–9.254%, SE = 1.864%), respectively. In one case, a specimen that was identified morphologically was recovered with its sister species on the NJ tree. The hybrid status of this specimen was established by sequence analysis of the second ribosomal internal transcribed spacer (ITS2). In another instance, this nuclear region was used to verify four cases of specimen misidentification that had been highlighted by the COI analysis. The COI barcode sequence was found to be suitable for the identification of Chrysomya species from the east coast of Australia.
Insecticide resistance in the malarial mosquito Anopheles arabiensis and association with the kdr mutation
Authors: MATAMBO T. S. , ABDALLA H. , BROOKE B. D. , KOEKEMOER L. L. , MNZAVA A. , HUNT R. H. , COETZEE M.
Published: March 2007

Abstract A colony of Anopheles arabiensis Patton (Diptera: Culicidae) from the Sennar region of Sudan was selected for resistance to dichlorodiphenyltrichloroethane (DDT). Adults from the F‐16 generation of the resistant strain were exposed to all four classes of insecticides approved for use in malaria vector control and showed high levels of resistance to them all (24‐h mortalities: malathion, 16.7%; bendiocarb, 33.3%; DDT, 12.1%; dieldrin, 0%; deltamethrin, 24.0%; permethrin, 0%). Comparisons between the unselected base colony and the DDT‐resistant strain showed elevated glutathione‐S‐transferase (P < 0.05) in both sexes and elevated esterases (P < 0.05) in males only. The Leu‐Phe mutation in the sodium channel gene was detected by polymerase chain reaction and sequencing, but showed no correlation with the resistant phenotype. These results do not provide any explanation as to why this colony exhibits such widespread resistance and further studies are needed to determine the precise mechanisms involved. The implications for malaria vector control in central Sudan are serious and resistance management (e.g. through the rotational use of different classes of insecticides) is recommended.
Discriminative feeding behaviour of Anopheles gambiae s.s. on endemic plants in western Kenya
Authors: MANDA H. , GOUAGNA L. C. , NYANDAT E. , KABIRU E. W. , JACKSON R. R. , FOSTER W. A. , GITHURE J. I. , BEIER J. C. , HASSANALI A.
Published: March 2007

Abstract Anopheles gambiae Giles s.s. (Diptera: Culicidae) is known to feed on plant sugars, but this is the first experimental study to consider whether it discriminates between plant species. Thirteen perennial plant species were selected on the basis of their local availability within the vicinity of human dwellings and larval habitats of An. gambiae s.s. in western Kenya. Groups of 100 or 200 mosquitoes were released into cages either with a cutting of one plant type at a time (single‐plant assay) or with cuttings of all 13 plants simultaneously (choice assay), respectively, and left overnight. In the choice assay, direct observations of the percentages of mosquitoes perching or feeding on each plant were recorded over four 1‐h periods each night. For both types of assay, mosquitoes were recaptured and the percentage that had fed on plants was assessed by testing them individually for the presence of fructose. To identify which plants the choice‐assay mosquitoes had fed on, gas chromatography (GC) profiles of samples of mosquito homogenates were compared with GC profiles of extracts from relevant parts of each plant. Four of the plants that were observed to have been fed on most frequently in the choice assay (Parthenium hysterophorus L., Tecoma stans L., Ricinus communis L., and Senna didymobotrya Fresen) were also shown to have been ingested most often by mosquitoes in both types of assay, suggesting that An. gambiae is differentially responsive to this range of plants, regardless of whether the plants were presented singly or mixed together. Significantly more females than males fed on plants, with the exception of P. hysterophorus L., one of the plants most frequently fed on. For most plant species (ten of 13), GC profiles indicated that An. gambiae obtained sugars primarily from flowers. The exceptions were P. hysterophorus L., Lantana camara L. and R. communis L., on which An. gambiae fed more often from leaves and stems than from flowers.
Mechanisms of population differentiation in seabirds
Authors: FRIESEN V. L. , BURG T. M. , McCOY K. D.
Published: March 2007

Despite recent advances in population genetic theory and empirical research, the extent of genetic differentiation among natural populations of animals remains difficult to predict. We reviewed studies of geographic variation in mitochondrial DNA in seabirds to test the importance of various factors in generating population genetic and phylogeographic structure. The extent of population genetic and phylogeographic structure varies extensively among species. Species fragmented by land or ice invariably exhibit population genetic structure and most also have phylogeographic structure. However, many populations (26 of 37) display genetic structure in the absence of land, suggesting that other barriers to gene flow exist. In these populations, the extent of genetic structure is best explained by nonbreeding distribution: almost all species with two or more population‐specific nonbreeding areas (or seasons) have phylogeographic structure, and all species that are resident at or near breeding colonies year‐round have population genetic structure. Geographic distance between colonies and foraging range appeared to have a weak influence on the extent of population genetic structure, but little evidence was found for an effect of colony dispersion or population bottlenecks. In two species (Galapagos petrel,Pterodroma phaeopygia, and Xantus's murrelet,Synthliboramphus hypoleucus), population genetic structure, and even phylogeographic structure, exist in the absence of any recognizable physical or nonphysical barrier, suggesting that other selective or behavioural processes such as philopatry may limit gene flow. Retained ancestral variation may be masking barriers to dispersal in some species, especially at high latitudes. Allopatric speciation undoubtedly occurs in this group, but reproductive isolation also appears to have evolved through founder‐induced speciation, and there is strong evidence that parapatric and sympatric speciation occur. While many questions remain unanswered, results of the present review should aid conservation efforts by enabling managers to predict the extent of population differentiation in species that have not yet been studied using molecular markers, and, thus, enable the identification of management units and evolutionary significant units for conservation.
Mutational bias suggests that replication termination occurs near the dif site, not at Ter sites
Authors: Hendrickson Heather , Lawrence Jeffrey G.
Published: March 2007

In bacteria, Ter sites bound to Tus/Rtp proteins halt replication forks moving only in one direction, providing a convenient mechanism to terminate them once the chromosome had been replicated. Considering the importance of replication termination and its position as a checkpoint in cell division, the accumulated knowledge on these systems has not dispelled fundamental questions regarding its role in cell biology: why are there so many copies of Ter, why are they distributed over such a large portion of the chromosome, why is the tus gene not conserved among bacteria, and why do tus mutants lack measurable phenotypes? Here we examine bacterial genomes using bioinformatics techniques to identify the region(s) where DNA polymerase III‐mediated replication has historically been terminated. We find that in both Escherichia coli and Bacillus subtilis, changes in mutational bias patterns indicate that replication termination most likely occurs at or near the dif site. More importantly, there is no evidence from mutational bias signatures that replication forks originating at oriC have terminated at Ter sites. We propose that Ter sites participate in halting replication forks originating from DNA repair events, and not those originating at the chromosomal origin of replication.
Corynebacterium diphtheriae employs specific minor pilins to target human pharyngeal epithelial cells
Authors: Mandlik Anjali , Swierczynski Arlene , Das Asis , Ton‐That Hung
Published: March 2007

Adherence to host tissues mediated by pili is pivotal in the establishment of infection by many bacterial pathogens. Corynebacterium diphtheriae assembles on its surface three distinct pilus structures. The function and the mechanism of how various pili mediate adherence, however, have remained poorly understood. Here we show that the SpaA‐type pilus is sufficient for the specific adherence of corynebacteria to human pharyngeal epithelial cells. The deletion of the spaA gene, which encodes the major pilin forming the pilus shaft, abolishes pilus assembly but not adherence to pharyngeal cells. In contrast, adherence is greatly diminished when either minor pilin SpaB or SpaC is absent. Antibodies directed against either SpaB or SpaC block bacterial adherence. Consistent with a direct role of the minor pilins, latex beads coated with SpaB or SpaC protein bind specifically to pharyngeal cells. Therefore, tissue tropism of corynebacteria for pharyngeal cells is governed by specific minor pilins. Importantly, immunoelectron microscopy and immunofluorescence studies reveal clusters of minor pilins that are anchored to cell surface in the absence of a pilus shaft. Thus, the minor pilins may also be cell wall anchored in addition to their incorporation into pilus structures that could facilitate tight binding to host cells during bacterial infection.
FtsK controls metastable recombination provoked by an extra Ter site in the Escherichia coli chromosome terminus
Authors: Louarn Jean‐Michel , Quentin Yves
Published: March 2007

The FtsK protein is required for septum formation in Escherichia coli and as a DNA translocase for chromosome processing while the septum closes. Its domain of action on the chromosome overlaps the replication terminus region, which lies between replication pause sites TerA and TerC. An extra Ter site, PsrA*, has been inserted at a position common to the FtsK and terminus domains. It is well tolerated, although it compels replication forks travelling clockwise from oriC to stall and await arrival of counter‐clockwise forks. Elevated recombination has been detected at the stalled fork. Analysis of PsrA*‐induced homologous recombination by an excision test revealed unique features. (i) rates of excision near PsrA* may fluctuate widely from clone to clone, a phenomenon we term whimsicality, (ii) excision rates are nevertheless conserved for many generations, a phenomenon we term memorization; their metastability at the clone level is explainable by frequent shifting between three cellular states – high, medium and low probability of excision, (iii) PsrA*‐induced excision is RecBC‐independent and is strongly counteracted by FtsK, which in addition is involved in its whimsicality and (iv) whimsicality disappears as the distance from the pause site increases. Action of FtsK at a replication fork was unexpected because the factor was thought to act on the chromosome only at septation, i.e. after replication is completed. Idiosyncrasy of PsrA*‐induced recombination is discussed with respect to possible intermingling of replication, repair and post‐replication steps of bacterial chromosome processing during the cell cycle.
Looking through the eyes of fungi: molecular genetics of photoreception
Authors: Herrera‐Estrella Alfredo , Horwitz Benjamin A.
Published: March 2007

Filamentous fungi respond to a variety of environmental signals. One of them is light, providing critical information about orientation, or impending stress. Cells of filamentous fungi appear to sense blue light through a unique transcription factor that has a flavin chromophore and activates its targets in a light‐dependent manner, the white collar (WC) complex. Fungal photophysiology, though, predicted a greater complexity of responses to the whole visible spectrum. The rapidly growing fungal genome database provides candidates to explain how fungi see not only blue, but also near‐UV, green and red light. At the same time, there are surprises in the genomes, including photoreceptors for which there are no obvious photoresponses. Linking these genes and their functions will help understand how a list of only a few biological chromophores accounts for such a diversity of responses. At the same time, deeper mechanistic understanding of how the WC complex functions will lead to fundamental insights at the point where the environment impinges, in this case in the form of photons, on the transcriptional machinery of the cell.
Out on a limb: how the Caulobacter stalk can boost the study of bacterial cell shape
Authors: Wagner Jennifer K. , Brun Yves V.
Published: March 2007

Understanding the mechanisms underlying the establishment of different bacterial cell shapes and the advantage that a particular shape imparts is one of the most fascinating and challenging areas of study in microbiology. One remarkable example of bacterial morphogenesis is the elaboration of long, tubular extensions of the cell envelope of certain aquatic bacteria. These appendages (also called prosthecae or stalks) possess features that make them particularly amenable models for experiments designed to uncover general principles of cell morphogenesis and of cell shape function. Recent evidence supports the hypothesis that stalk synthesis in Caulobacter crescentus is a specialized form of cell elongation that confers to the cell substantial advantages in nutrient uptake. Further insights into the mechanisms and function of stalk synthesis will require a multidisciplinary systems biology approach using principles and methodologies from ecology and evolutionary biology to biophysics and mathematical modelling.
Identification of an ospC operator critical for immune evasion of Borrelia burgdorferi
Authors: Xu Qilong , McShan Kristy , Liang Fang Ting
Published: March 2007

Timely expression of the outer surface protein C (OspC) is crucial for the pathogenic strategy of the Lyme disease spirochete Borrelia burgdorferi. The pathogen abundantly expresses OspC during initial infection when the antigen is required, but downregulates when its presence poses a threat to the spirochetes once the anti‐OspC humoral response has developed. Here, we show that a large palindromic sequence immediately upstream of the ospC promoter is essential for the repression of ospC expression during murine infection and for the ability of B. burgdorferi to evade specific OspC humoral immunity. Deletion of the sequence completely diminished the ability of B. burgdorferi to avoid clearance by transferred OspC antibody in SCID mice. B. burgdorferi lacking the regulatory element was able to initiate infection but unable to persist in immunocompetent mice. Taken together, the regulatory element immediately upstream of the ospC promoter serves as an operator that may interact with an unidentified repressor(s) to negatively regulate ospC expression and is essential for the immune evasion of B. burgdorferi.
Mutational bias suggests that replication termination occurs near the dif site, not at Ter sites: what's the Dif?
Authors: Higgins N. Patrick
Published: March 2007

In this issue of Molecular Microbiology, Hendrickson and Lawrence analyse the sequence of bacterial genomes to map the historical traffic pattern of chromosome replication. Their surprising conclusion is that most forks terminate at the dif site rather than at the Tus/Ter sites where most investigators have concluded termination occurs most frequently. What make this analysis novel are the methods and the revisionist hypotheses for how and why forks might stop at dif.
Antibiotic‐mediated recombination: ciprofloxacin stimulates SOS‐independent recombination of divergent sequences in Escherichia coli
Authors: López Elena , Elez Marina , Matic Ivan , Blázquez Jesús
Published: March 2007

The widespread use and abuse of antibiotics as therapeutic agents has produced a major challenge for bacteria, leading to the selection and spread of antibiotic resistant variants. However, antibiotics do not seem to be mere selectors of these variants. Here we show that the fluoroquinolone antibiotic ciprofloxacin, an inhibitor of type II DNA topoisomerases, stimulates intrachromosomal recombination of DNA sequences. The stimulation of recombination between divergent sequences occurs via either the RecBCD or RecFOR pathways and is, surprisingly, independent of SOS induction. Additionally, this stimulation also occurs in a hyperrecombinogenic mismatch repair mutS mutant. It is worth noting that ciprofloxacin also stimulates the conjugational recombination of an antibiotic resistance gene. Finally, we demonstrate that Escherichia coli is able to recover from treatments with recombination‐stimulating concentrations of the antibiotic. Thus, fluoroquinolones can increase genetic variation by the stimulation of the recombinogenic capability of treated bacteria (via an SOS‐independent mechanism) and consequently may favour the acquisition, evolution and spread of antibiotic resistance determinants.
A novel self‐capping mechanism controls aggregation of periplasmic chaperone Caf1M
Authors: Zavialov Anton V. , Knight Stefan D.
Published: March 2007

The chaperone Caf1M belongs to a family of ATP‐independent periplasmic chaperones that together with outer membrane ushers assemble and secrete filamentous adhesion organelles in Gram‐negative pathogens. It assists in folding and transport of Caf1 subunits of the F1 capsular antigen of Yersinia pestis, the microbe causing bubonic plague. In the periplasm, Caf1M prevents subunit aggregation by capping the extensive hydrophobic surface of activated Caf1. We found that subunit‐free Caf1M exists predominantly as a tetramer [Kd = (2–30) × 10−14 M3 in the 12–37°C interval]. A 2.9 Å resolution crystal structure of the Caf1M tetramer reveals that each of the four molecules contribute its subunit binding sequences (the A1 and G1 strands) to form an eight‐stranded hetero‐sandwich with a well‐packed phenylalanine‐rich hydrophobic core. Tetramerization protects chaperone molecules against enzymatic proteolysis. Deletions in the subunit binding motifs completely abolish tetramer assembly, suggesting that the hetero‐sandwich is the main structural feature holding the tetramer together. Arresting tetramer assembly by a deletion of the N‐terminal binding motif, while leaving the major subunit binding motif VGVFVQFAI (G1 strand) intact, results in accumulation of unspecific aggregates. Deletions in the VGVFVQFAI motif abolish both tetramer assembly and aggregation, consistent with the predicted high β‐aggregation propensity for this motif. These results suggest that the packing of the aggregation‐prone subunit binding sequences into the hetero‐domain is a novel molecular mechanism preventing unspecific aggregation of the free chaperone.
The quorum‐sensing transcription factor TraR decodes its DNA binding site by direct contacts with DNA bases and by detection of DNA flexibility
Authors: White Catharine E. , Winans Stephen C.
Published: March 2007

TraR of Agrobacterium tumefaciens is a member of the LuxR family of transcriptional regulators, and binds to specific DNA sequences (tra boxes) at target promoters of the tumour‐inducing (Ti) plasmid. Each tra box has a pronounced dyad symmetry, and each subunit of a TraR dimer binds to one half of a tra box via a helix–turn–helix (HTH) DNA binding motif. Structural analysis has suggested that TraR makes extensive sequence‐specific contacts with tra box DNA. In this study, we tested these predictions using synthetic self‐complementary oligonucleotides containing variant tra box sequences. Some predictions made from structural analysis were confirmed, while others were shown to be incorrect. Unexpectedly, these experiments also showed that six nucleotides at the centre of the tra box that make no direct contact with TraR are nevertheless critical for high‐affinity binding and probably act by facilitating a previously described DNA bend. Variant tra boxes were also tested for transcription activity in vivo. Most transcription assays reflected in vitro binding assays. However, alterations of the outermost nucleotides had little effect on TraR binding but blocked transcription, probably by altering an overlapping −35 promoter motif.
Conservation and diversity in the immunity regions of wild phages with the immunity specificity of phage λ
Authors: Degnan Patrick H. , Michalowski Christine B. , Babić Andrea C. , Cordes Matthew H. J. , Little John W.
Published: March 2007

The gene regulatory circuitry of phage λ is among the best‐understood circuits. Much of the circuitry centres around the immunity region, which includes genes for two repressors, CI and Cro, and their cis‐acting sites. Related phages, termed lambdoid phages, have different immunity regions, but similar regulatory circuitry and genome organization to that of λ, and show a mosaic organization, arising by recombination between lambdoid phages. We sequenced the immunity regions of several wild phages with the immunity specificity of λ, both to determine whether natural variation exists in regulation, and to analyse conservation and variability in a region rich in well‐studied regulatory elements. CI, Cro and their cis‐acting sites are almost identical to those in λ, implying that regulatory mechanisms controlled by the immunity region are conserved. A segment adjacent to one of the operator regions is also conserved, and may be a novel regulatory element. In most isolates, different alleles of two regulatory proteins (N and CII) flank the immunity region; possibly the lysis‐lysogeny decision is more variable among isolates. Extensive mosaicism was observed for several elements flanking the immunity region. Very short sequence elements or microhomologies were also identified. Our findings suggest mechanisms by which fine‐scale mosaicism arises.
A novel class of mutations that affect DNA replication in E. coli
Authors: Nordman Jared , Skovgaard Ole , Wright Andrew
Published: March 2007

Over‐initiation of DNA replication in cells containing the cold‐sensitive dnaA(cos) allele has been shown to lead to extensive DNA damage, potentially due to head‐to‐tail replication fork collisions that ultimately lead to replication fork collapse, growth stasis and/or cell death. Based on the assumption that suppressors of the cold‐sensitive phenotype of the cos mutant should include mutations that affect the efficiency and/or regulation of DNA replication, we subjected a dnaA(cos) mutant strain to transposon mutagenesis and selected mutant derivatives that could form colonies at 30°C. Four suppressors of the dnaA(cos)‐mediated cold sensitivity were identified and further characterized. Based on origin to terminus ratios, chromosome content per cell, measured by flow cytometry, and sensitivity to the replication fork inhibitor hydroxyurea, the suppressors fell into two distinct categories: those that directly inhibit over‐initiation of DNA replication and those that act independently of initiation. Mutations that decrease the cellular level of HolC, the χ subunit of DNA polymerase, or loss of ndk (nucleoside diphosphate kinase) function fall into the latter category. We propose that these novel suppressor mutations function by decreasing the efficiency of replication fork movement in vivo, either by decreasing the dynamic exchange of DNA polymerase subunits in the case of HolC, or by altering the balance between DNA replication and deoxynucleoside triphosphate synthesis in the case of ndk. Additionally, our results indicate a direct correlation between over‐initiation and sensitivity to replication fork inhibition by hydroxyurea, supporting a model of increased head‐to‐tail replication fork collisions due to over‐initiation.