bluuebunny/crossref_metadata_2025_split huggingface dataset:
Epidemiology, Molecular Mycology, and Environmental Sources ofFusariumInfection in Patients with Cancer
Authors: Raad Issam , Tarrand Jeffrey , Hanna Hend , Albitar Maher , Janssen Erle , Boktour Maha , Bodey Gerald , Mardani Masoud , Hachem Ray , Kontoyiannis Dimitrios , Whimbey Estella , Rolston Kenneth 
Published: February 2006

Objective:To investigate the epidemiology and environmental sources of Fusarium infections in patients with cancer.Design:Retrospective case-control study conducted following surveillance environmental cultures and DNA analysis of isolated organisms.Setting:A tertiary-care, university cancer center.Methods:In 1996 and 1997, environmental cultures were performed on air samples and water systems. A retrospective chart review was performed for 70 patients with cancer identified with fusariosis between 1987 and 1997. Patients with fusariosis were compared with 49 uninfected control patients who occupied hospital rooms with positive environmental cultures for Fusarium. With the use of random amplification of polymorphic DNA organisms isolated from infected patients were compared with environmental organisms.Results:Most of the patients with Fusarium (40, 57%) were infected on or within 3 days of admission, indicating community rather than nosocomial acquisition. Patients were comparable in terms of underlying immunocompromised status to 49 uninfected control patients. However, the duration from admission to infection in the patients with fusariosis tended to be shorter than the duration from admission to discharge in the exposed control patients (P= .06). Water cultured from the hospital tanks and from sinks and water fountains was negative for Fusarium. With the use of polymerase chain reaction, environmental isolates did not match clinical ones. Quantitative air sampling showed that the quantitative outdoor Fusarium levels were eightfold higher than the indoor levels. During the rainy summer season, outdoor air concentrations of Fusarium were at their highest, coinciding with the peak incidence of fusariosis at our center.Conclusion:The most likely source of fusariosis was the external environment rather than nosocomial sources, such as water.
Molecular Epidemiology of Methicillin-ResistantStaphylococcus aureusin Nursing Homes: A Cross-Sectional Study
Authors: Hoefnagels-Schuermans Annette , Niclaes Luc , Buntinx Frank , Suetens Carl , Jans Beatrice , Verhaegen Jan , Eldere Johan Van 
Published: February 2006

AbstractA cross-sectional study of methicillin-resistantStaphylococcus aureuscarriage in 2,857 nursing home residents showed an overall prevalence of 4.9%. The three clones identified by genetic analysis were identical to those in the acute care facilities; only their relative prevalence differed. Clone 2 took epidemic proportions in five of these nursing homes.
Bacterial nucleoid dynamics: oxidative stress response in Staphylococcus aureus
Authors: Morikawa Kazuya , Ohniwa Ryosuke L. , Kim Joongbaek , Maruyama Atsushi , Ohta Toshiko , Takeyasu Kunio 
Published: February 2006

A single‐molecule‐imaging technique, atomic force microscopy (AFM) was applied to the analyses of the genome architecture of Staphylococcus aureus. The staphylococcal cells on a cover glass were subjected to a mild lysis procedure that had maintained the fundamental structural units in Escherichia coli. The nucleoids were found to consist of fibrous structures with diameters of 80 and 40 nm. This feature was shared with the E. coli nucleoid. However, whereas the E. coli nucleoid dynamically changed its structure to a highly compacted one towards the stationary phase, the S. aureus nucleoid never underwent such a tight compaction under a normal growth condition. Bioinformatic analysis suggested that this was attributable to the lack of IHF that regulate the expression of a nucleoid protein, Dps, required for nucleoid compaction in E. coli. On the other hand, under oxidative conditions, MrgA (a staphylococcal Dps homolog) was over‐expressed and a drastic compaction of the nucleoid was detected. A knock‐out mutant of the gene encoding the transcription factor (perR) constitutively expressed mrgA, and its nucleoid was compacted without the oxidative stresses. The regulatory mechanisms of Dps/MrgA expression and their biological significance were postulated in relation to the nucleoid compaction.
5′‐Adenosinephosphosulphate reductase (CysH) protects Mycobacterium tuberculosis against free radicals during chronic infection phase in mice
Authors: Senaratne Ryan H. , De Silva A. Dharshan , Williams Spencer J. , Mougous Joseph D. , Reader J. Rachel , Zhang Tianjiao , Chan Stephen , Sidders Ben , Lee Dong H. , Chan John , Bertozzi Carolyn R. , Riley Lee W. 
Published: February 2006

SummaryA major obstacle to tuberculosis (TB) control is the problem of chronic TB infection (CTBI). Here we report that 5′‐adenosinephosphosulphate reductase (CysH), an enzyme essential for the production of reduced‐sulphur‐containing metabolites, is critical for Mycobacterium tuberculosis (Mtb) survival in chronic infection phase in mice. Disruption of cysH rendered Mtb auxotrophic for cysteine and methionine, and attenuated virulence in BALB/c and C57BL/6 immunocompetent mice. The mutant and wild‐type Mtb replicated similarly during the acute phase of infection, but the mutant showed reduced viability during the persistent phase of the infection. The cysH mutant caused disease and death after 4–7 weeks of infection in four different groups of mice – Rag1–/–, NOS2–/–, gp91phox–/– NOS2–/– and gp91phox–/– mice given aminoguanidine [to suppress the effects of nitric oxide synthase 2 (NOS2)]– indicating minimal metabolic effect on the cysH mutant survival in these mice. The cysH mutant was also susceptible to peroxynitrite and hydrogen peroxide in vitro. These results show that CysH is important for Mtb protection during the chronic infection phase, and that resistance to nitrosative and oxidative stress may be the mechanism of this protection. Thus, this metabolic gene of an intracellular pathogen could have a secondary role in protection against the host immune response. Finally the lack of an endogenous human orthologue of cysH and its possible role in defence against adaptive immunity renders CysH an attractive enzyme for further studies as a target for therapeutics active against CTBI.
Poly(A)‐polymerase I links transcription with mRNA degradation via σS proteolysis
Authors: Santos Jorge M. , Freire Patrick , Mesquita Francisco S. , Mika Franziska , Hengge Regine , Arraiano Cecília M. 
Published: February 2006

SummaryBacteria rapidly adapt to changes in growth conditions through control of transcription and specific mRNA degradation. Interplay of both mechanisms must exist in order to achieve fine‐tuned regulation of gene expression. Transcription of the Escherichia coli bolA gene is mediated by the RpoS/σS transcription factor in response to environmental signals. In this report it is shown that the mechanisms of bolA1p mRNA transcription and degradation are tightly connected at the onset of stationary phase and in response to sudden carbon starvation. In stationary phase, bolA1p mRNA levels were reduced 2.5‐fold in a poly(A)‐polymerase I (PAPI) mutant, explained by the significant threefold reduction in σS protein levels in the same strain. Furthermore, fusions with the rpoS gene, analysis of the stability of σS and the levels of RssB indicate that the absence of PAPI enhances RssB‐mediated σS proteolysis specifically in starved cells. The fact that PAPI induces higher cellular levels of a global regulator is a novel finding of wide biological significance. PAPI could work as a linker between transcription and mRNA degradation with the ultimate goal of adapting and surviving to growth‐limiting conditions.
Drastic reduction in the virulence of Streptococcus pneumoniae expressing type 2 capsular polysaccharide but lacking choline residues in the cell wall
Authors: Kharat Arun S. , Tomasz Alexander 
Published: February 2006

SummaryThe role of capsular polysaccharides and several virulence‐related proteins in the pathogenic potential of Streptococcus pneumoniae has been studied extensively. Much less information is available about the role of the pneumococcal cell wall in virulence. In this communication we describe an experimental system that has allowed us to test – in a global way – the role of choline, a structural component of the pneumococcal cell wall, in virulence. We constructed double mutants of S. pneumoniae which have lost the auxotrophic requirement for choline and which were also blocked from utilizing choline from the growth medium. Such a double mutant expressing type 2 capsule but completely lacking choline residues from its cell wall grew well both in vitro and also in the blood of infected mice, but showed striking reduction of virulence approaching that of a capsule‐free strain in several models of pneumococcal disease including the capacity to attach and invade a human nasopharyngeal cell line; nasal colonization and intraperitoneal and intravenous inoculation in the mouse. The findings allow one to separate the choline requirement of S. pneumoniae into two sharply defined classes: the need for choline in growth and replication which can be effectively bypassed and the need for choline in pneumococcal virulence that appears to be irreplaceable. The double mutant should be a useful experimental tool to dissect the mechanism of choline requirement in various stages of pneumococcal virulence.
The role of replication initiation control in promoting survival of replication fork damage
Authors: Sutera Vincent A. , Lovett Susan T. 
Published: February 2006

SummaryDam methylase mutants were recovered in a screen for mutants sensitive to UV irradiation or mild inhibition of replication elongation. Dam's role in tolerance of DNA damage is to provide binding sites for SeqA, because seqA mutants showed similar sensitivity that was genetically epistatic to dam. The sensitivity of seqA mutants to UV irradiation and to the replication inhibitors hydroxyurea (HU) and azidothymidine (AZT) was suppressed by alleles of dnaA that reduce the efficiency of replication initiation. These results suggest that for survival of replication fork damage, SeqA's repression of replication initiation is more important than its effects on nucleoid organization. Convergence of forks upon DNA damage is a likely explanation for seqA mutant sensitivity, because its poor survival of UV was suppressed by reducing secondary initiation through minimal medium growth. Surprisingly, growth in minimal medium reduced the ability of seqA+ strains to form colonies in the presence of low levels of AZT. Double dnaA seqA mutants exhibited plating efficiencies much superior to wild‐type strains during chronic low‐level AZT exposure in minimal medium. This suggests that mild inhibition of replication fork progression may actively restrain initiation such that seqA+ strains fail to recover initiation capacity after sustained conditions of replication arrest.
Freeze/thaw‐induced embolism depends on nadir temperature: the heterogeneous hydration hypothesis
Authors: BALL M. C. , CANNY M. J. , HUANG C. X. , EGERTON J. J. G. , WOLFE J. 
Published: February 2006

ABSTRACTFreeze/thaw‐induced embolism was studied in leaves of field‐grown snow gum (Eucalyptus pauciflora) subject to frequent morning frosts. Juvenile trees were grown in buried pots, brought to the laboratory at different stages of acclimation and subjected to simulated frost‐freezes (at 2 °C h−1) to nadir temperatures of −3 or − 6 °C, which snow gums commonly experience. Frost‐frozen and subsequently thawed leaves were cryo‐fixed to preserve the distribution of water and were then examined by cryo‐scanning electron microscopy. No embolisms were found in leaves frozen to −3 °C and thawed. In contrast, 34% of vessels were embolized in thawed leaves that had been frozen to −6 °C. This difference was seen also in the extent of extracellular ice blocks in the mid‐vein expansion zones in leaves frozen to −3 and −6 °C, which occupied 3 and 14% of the mid‐vein area, respectively. While the proportion of embolism depended on nadir temperature, it was independent of season (and hence of acclimation state). From the observation that increased embolism at lower nadir temperature was related to the freeze‐induced redistribution of water, we hypothesize that the dehydration of cell walls and cells caused by the redistribution exerts sufficient tension on xylem water to induce cavitation on thawing.
Interactions between the effects of atmospheric CO2 content and P nutrition on photosynthesis in white lupin (Lupinus albus L.)
Authors: CAMPBELL CATHERINE D. , SAGE ROWAN F. 
Published: February 2006

ABSTRACTPhosphorus (P) is a major factor limiting the response of carbon acquisition of plants and ecosystems to increasing atmospheric CO2 content. An important consideration, however, is the effect of P deficiency at the low atmospheric CO2 content common in recent geological history, because plants adapted to these conditions may also be limited in their ability to respond to further increases in CO2 content. To ascertain the effects of low P on various components of photosynthesis, white lupin (Lupinus albus L.) was grown hydroponically at 200, 400 and 750 µmol mol−1 CO2, under sufficient and deficient P supply (250 and 0.69 µm P, respectively). Increasing growth CO2 content increased photosynthesis only under sufficient growth P. Ribulose 1,5‐biphosphate carboxylase/oxygenase (Rubisco) content and activation state were not reduced to the same degree as the net CO2 assimilation rate (A), and the in vivo rate of electron transport was sufficient to support photosynthesis in all cases. The rate of triose phosphate use did not appear limiting either, because all the treatments continued to respond positively to a drop in oxygen levels. We conclude that, at ambient and elevated CO2 content, photosynthesis in low‐P plants appears limited by the rate of ribulose biphosphate (RuBP) regeneration, probably through inhibition of the Calvin cycle. This failure of P‐deficient plants to respond to rising CO2 content above 200 µmol mol−1 indicates that P status already imposes a widespread restriction in plant responses to increases in CO2 content from the pre‐industrial level to current values.
Clinical guidelines to diagnose smear‐negative pulmonary tuberculosis in Pakistan, a country with low‐HIV prevalence
Authors: Siddiqi Kamran , Walley J. , Khan M. A. , Shah K. , Safdar N. 
Published: February 2006

SummaryObjectives  To develop and validate clinical guidelines for diagnosis of smear‐negative pulmonary tuberculosis (TB) in developing countries with low‐HIV prevalence.Methods  We developed diagnostic guidelines for smear‐negative TB. Clinical diagnoses based on these guidelines were compared with sputum culture, chest X‐rays and reports of an expert panel.Results  The guidelines achieved a sensitivity of 0.59 [confidence interval (CI) 0.46–0.66] and a specificity of 0.86 (CI 0.84–0.88) in diagnosing smear‐negative TB. A total of 6.8% of patients who initially improved after a course of antibiotics were later confirmed to have TB. Clinicians detected an abnormal chest X‐ray in 92% (CI 88–96%) and radiological signs of pulmonary TB in 98% (CI 94–100%) of cases.Conclusions  Our experience highlights a number of dilemmas faced in developing, testing and implementing diagnostic guidelines in poorly resourced conditions. Using radiological criteria for TB and appropriate training can help in improving the diagnostic skills of primary care clinicians working in low‐HIV settings with access to X‐ray facilities. But a significant number of apparently smear‐negative TB cases may in fact be smear positive and TB programmes should focus on improving the quality of direct acid‐fast bacilli microscopy. The value of an antibiotic trial is questionable due to the relatively large number of false negatives generated by this approach.
The spectrum of hypoxaemia in children admitted to hospital in The Gambia, West Africa
Authors: Junge Sonja , Palmer Ayo , Greenwood Brian M. , Kim Mulholland E. , Weber Martin W. 
Published: February 2006

SummaryObjective  Hypoxia predicts mortality in children with acute lower respiratory infections (ALRIs). We investigated the prevalence and predictive value of hypoxia in ALRI and other acute infectious diseases.Methods  We studied the spectrum of hypoxaemia in 4047 children admitted to a tertiary hospital in The Gambia. Oxygen saturation was measured shortly after admission. Severe hypoxaemia was defined as an oxygen saturation below 90%.Results  5.8% of all admissions had severe hypoxaemia. Prevalence of hypoxaemia varied between disease groups: it was 11.7% in ALRI cases, 16.5% in neonates; 2.9% in malaria cases overall but 6.5% in cerebral malaria patients; and 2.7% in children with meningitis. Hypoxaemia predicted a poor outcome; the odds ratio for death among paediatric admissions overall was 7.45 [95% confidence intervals (CI) 5.40–10.29]. Surprisingly, it was lowest for children with ALRI [OR 3.53 (95% CI 1.13–10.59)], and higher for those with malaria 9.90 [95% CI 4.39–22.35].Conclusion  Hypoxaemia is common among Gambian children admitted to hospital and it is often associated with a poor outcome. A similar situation is likely in many other developing countries. Thus, equipment for measuring oxygen saturation, and facilities and equipment for effective oxygen delivery need to be made available in developing countries.
Fatigue crack growth under variable amplitude loading Part I: experimental investigations
Authors: SANDER M. , RICHARD H. A. 
Published: February 2006

ABSTRACTDuring use, a component or a structure is exposed to variable amplitude loading, which influences the lifetime. Within the scope of this work, systematic investigations of different loading situations are carried out by means of experimental studies (part I) as well as analytical and numerical studies (part II). The experimental investigations show that overloads lead to retardation effects, which are influenced by several factors, e.g. the overload ratio, baseline‐level loading, number of overloads or the fraction of mixed mode. In a high–low–high block loading, both retarded and accelerated crack growth can be obtained, which is also influenced, e.g. by the block loading ratio and the length of the block. Moreover, experimental studies have been performed with load spectra, like FELIX/28, CARLOS vertical and WISPER. They have been applied in original form as well as in counted and reconstructed sequences.
Habitat preferences of the Andean bear (Tremarctos ornatus) in the Bolivian Andes
Authors: Ríos‐Uzeda B. , Gómez H. , Wallace R. B. 
Published: February 2006

AbstractHabitat preferences of the Andean bear Tremarctos ornatus were studied within two adjacent protected areas in the north‐western Bolivian Andes. Standard transects measuring habitat variables and bear sign frequency were used spanning seven different vegetation types. Andean bears were present at 28 of 33 sampled sites and actively preferred high‐elevation elfin forest and upper montane humid forests, and used high‐elevation humid ‘páramo’ grasslands and middle montane humid forests according to their availability. Bears were absent from dry montane and Andean foothill forests and relative abundance was low in lower montane humid forests. Elevation and basal area of food items were the variables most closely related to the relative abundance.
Do juvenile gape‐limited predators compensate for their small size when feeding?
Authors: Vincent S. E. , Vincent P.‐D. , Irschick D. J. , Rossell J. M. 
Published: February 2006

AbstractWhen juvenile and adult animals occur syntopically, juveniles are at a distinct performance disadvantage due to their absolutely small size. Yet, optimal foraging theory predicts that juvenile predators should feed efficiently in order to compete with adults for food, and to minimize their exposure to predators. Previous authors have suggested that one way for juvenile animals to accomplish these ecological tasks is by increasing their overall feeding performance relative to adults (compensation hypothesis). Nonetheless, only a handful of studies have tested whether juvenile animals have increased feeding performance (e.g. decreased ingestion and/or handling times relative to body size) compared with adults. We tested this hypothesis by examining the ontogeny of head dimensions and feeding performance (ingestion time and number of mandibular protractions) on fish prey for broad‐banded water snakesNerodia fasciata. Individuals were fed fish scaled in a 1:1 ratio to their head width. All head dimensions scaled with significant negative allometry versus body size, and thus smaller snakes had relatively larger heads for their body size compared with larger snakes. By contrast, most head variables (except head volume) exhibited positive allometry versus head length, demonstrating that larger snakes had larger head dimensions relative to head size compared with smaller snakes. In the performance trials, smaller snakes had worse feeding performances when feeding on similarly sized fish prey (relative to their head width) compared with larger snakes. Therefore, these data show that smaller water snakes do not compensate for their size through increased feeding performance.
Reproductive photoresponsiveness in Aethomys ineptus and A. namaquensis (Rodentia: Muridae) from southern Africa
Authors: Muteka S. P. , Chimimba C. T. , Bennett N. C. 
Published: February 2006

AbstractMale Tete veld rats Aethomys ineptus and Namaqua rock mice A. namaquensis were independently subjected to a long photoperiod of 16L:8D and a short photoperiod of 8L:16D for 3 months in order to assess the effect of photoperiod on testicular function. Testicular parameters examined included testicular mass relative to body mass, testicular volume, seminiferous tubule diameters and changes in circulating plasma testosterone concentration. On a long day (LD) length, both species exhibited significantly higher testicular mass relative to body mass and testicular volume, and larger seminiferous tubule diameters. Circulating plasma testosterone concentrations in A. ineptus were not significantly different between the two photoperiodic treatments, but A. namaquensis showed significantly higher testosterone concentration in males on a LD length than on a short day (SD) length. This suggests that both A. ineptus and A. namaquensis are photoperiodically responsive to LDs.
Foraging behaviour and dispersion of eastern grey kangaroos (Macropus giganteus) in an ideal free framework
Authors: Maguire G. , Ramp D. , Coulson G. 
Published: February 2006

AbstractIdeal free distribution (IFD) theory predicts that animals in competitive situations should distribute themselves among available habitat patches according to the density of conspecifics and its regulatory effect on resources. To investigate the applicability of IFD models to free‐ranging herbivores, we quantified the dispersion and foraging behaviour of eastern grey kangaroos Macropus giganteus among habitat patches of differing suitability, within and outside a reservoir catchment in southern Victoria, Australia. Kangaroo densities within the catchment had a regulatory effect on resource density, while surrounding farmland maintained a higher standing crop despite higher densities of competitors. This difference was slight in autumn, however, when the system was apparently close to equilibrium. Gross bite rates of individuals foraging in farmland were lower than for individuals foraging within the catchment, and vigilance behaviour occurred more frequently in farmland habitat than any other, decreasing time devoted to feeding. Interference competition occurred in only 1.9% of focal samples, although competitive differences based on phenotype were observed. Although resource gains by individual kangaroos are likely to be influenced by other factors, including resource dynamics, predation risk and phenotypic differences, IFD theory provides a valuable analytical framework for this herbivore foraging system.