bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification and characterization of a Cryptococcus neoformans ATP binding cassette (ABC) transporter‐encoding gene, CnAFR1, involved in the resistance to fluconazole
Authors: Posteraro Brunella , Sanguinetti Maurizio , Sanglard Dominique , La Sorda Marilena , Boccia Stefania , Romano Lucio , Morace Giulia , Fadda Giovanni 
Published: March 2003

SummaryResistance to fluconazole is a possible event during prolonged suppressive drug therapy for cryptococ‐cal meningitis, the most frequently encountered life‐threatening manifestation of cryptococcosis. The knowledge of this resistance at the molecular level is important for management of cryptococcosis. In order to identify genes involved in azole resistance in Cryptococcus neoformans, a cDNA subtraction library technique was chosen as a strategy. First, a fluconazole‐resistant mutant BPY22.17 was obtained from a susceptible clinical isolate BPY22 by in vitro exposure to the drug. Then, a subtractive hybridization procedure was used to compare gene expression between the obtained strains. We identified a cDNA overexpressed in the fluconazole‐resistant strain BPY22.17 that was used as a probe to isolate the entire gene in a C. neoformans genomic library. Sequence analysis of this gene identified an ATP Binding Cassette (ABC) transporter‐encoding gene called C. neoformans AntiFungal Resistance 1 (CnAFR1). Disruption of CnAFR1 gene in the resistant isolate (BPY22.17) resulted in an enhanced susceptibility of the knock‐out mutant cnafr1 against fluconazole, whereas reintroduction of the gene in cnafr1 resulted in restoration of the resistance phenotype, thus confirming that CnAFR1 is involved in fluconazole resistance of C. neoformans. Our findings therefore reveal that an active drug efflux mechanism can be involved in the development of azole resistance in this important human pathogen.
Penicillin‐binding proteins in Streptococcus agalactiae: a novel mechanism for evasion of immune clearance
Authors: Jones Amanda L. , Needham Rachel H. V. , Clancy Anne , Knoll Katherine M. , Rubens Craig E. 
Published: March 2003

SummaryGroup B streptococci (GBS) remain the most significant bacterial pathogen causing neonatal sepsis, pneumonia and meningitis in the USA despite CDC‐recommended chemoprophylaxis strategies for preventing infection. To cause infection pathogens such as GBS must evade recognition and clearance by the host's immune system. Strategies for avoidance of opsonization and phagocytic killing include elaboration of antiopsonophagocytic capsules and surface proteins. During screening for mutants of GBS that were attenuated for virulence in a neonatal rat sepsis model, we identified a mutant with a transposon insertion in the ponA gene. ponA encodes an extra‐cytoplasmic penicillin‐binding protein PBP1a, a newly identified virulence trait for GBS that promotes resistance to phagocytic killing independent of capsular polysaccharide. Complementation analysis in vivo and in vitro confirmed that the altered phenotypes observed in the mutant were due to the transposon insertion in ponA. Deletion of PBP1a does not affect C3 deposition on GBS suggesting that mechanism by which PBP1a protects GBS from phagocytic killing is distinct from the antiopsonic activity of capsular polysaccharide. This is the first report describing expression of an antiphagocytic surface protein by GBS and represents a novel mechanism for evasion of immune recognition and clearance that may explain the decreased virulence observed in Gram‐positive bacterial species for penicillin‐binding protein mutants.
The essential role of the invariant GGQ motif in the function and stability in vivo of bacterial release factors RF1 and RF2
Authors: Mora Liliana , Heurgué‐Hamard Valérie , Champ Stéphanie , Ehrenberg Måns , Kisselev Lev L. , Buckingham Richard H. 
Published: March 2003

SummaryRelease factors RF1 and RF2 are required in bacteria for the cleavage of peptidyl‐tRNA. A single sequence motif, GGQ, is conserved in all eubacterial, archaebacterial and eukaryotic release factors and may mimic the CCA end of tRNA, although the position of the motif in the crystal structures of human eRF1 and Escherichia coli RF2 is strikingly different. Mutations have been introduced at each of the three conserved positions. Changing the Gln residue to Ala or Glu allowed the factors to retain about 22% of tetrapeptide release activity in vitro, but these mutants could not complement thermosensitive RF mutants in vivo. None of several mutants with altered Gly residues retained activity in vivo or in vitro. Many GGQ mutants were poorly expressed and are presumably unstable; many were also toxic to the cell. The toxic mutant factors or their degradation products may bind to ribosomes inhibiting the action of the normal factor. These data are consistent with a common role for the GGQ motif in bacterial and eukaryotic release factors, despite strong divergence in primary, secondary and tertiary structure, but are difficult to reconcile with the hypothesis that the amide nitrogen of the Gln plays a vital role in peptidyl‐tRNA hydrolysis.
The dnaAcos allele of Escherichia coli: hyperactive initiation is caused by substitution of A184V and Y271H, resulting in defective ATP binding and aberrant DNA replication control
Authors: Simmons Lyle A. , Kaguni Jon M. 
Published: March 2003

SummaryChromosomal DNA replication is regulated at the level of commitment to this biochemical pathway. In Escherichia coli, DnaA protein appears to regulate this process. A mutant form, DnaAcos, carrying four amino acid substitutions, is apparently defective in responding to regulatory signals, because it induces hyperactive initiation from the bacterial replication origin (oriC). In this report, the phenotype of hyperactive initiation is shown to be the result of two specific amino acid substitutions. One (A184V) immediately adjacent to a Walker A box (P loop motif) causes a defect in ATP binding (Carr and Kaguni, 1996, Mol Microbiol 20: 1307–1318). The second amino acid substitution (Y271H) appears to stabilize the activity of the mutant protein carrying the A184V substitution. The mutant protein carrying both amino acid substitutions (A184V + Y271H) is defective in modulating the frequency of initiation from oriC, as demonstrated by marker frequency analysis of oriC and a locus near the replication terminus. These results indicate that a defect in ATP binding results in aberrant control of DNA replication.
Microarray expression profiling: capturing a genome‐wide portrait of the transcriptome
Authors: Conway Tyrrell , K. Gary , Schoolnik  
Published: March 2003

SummaryThe bacterial transcriptome is a dynamic entity that reflects the organism's immediate, ongoing and genome‐wide response to its environment. Microarray expression profiling provides a comprehensive portrait of the transcriptional world enabling us to view the organism as a ‘system’ that is more than the sum of its parts. The vigilance of microorganisms to environmental change, the alacrity of the transcriptional response, the short half‐life of bacterial mRNA and the genome‐scale nature of the investigation collectively explain the power of this method. These same features pose the most significant experimental design and execution issues which, unless surmounted, predictably generate a distorted image of the transcriptome. Conversely, the expression profile of a properly conceived and conducted microarray experiment can be used for hypothesis testing: disclosure of the metabolic and biosynthetic pathways that underlie adaptation of the organism to chang‐ing conditions of growth; the identification of co‐ordinately regulated genes; the regulatory circuits and signal transduction systems that mediate the adaptive response; and temporal features of developmental programmes. The study of bacterial pathogenesis by microarray expression profiling poses special challenges and opportunities. Although the technical hurdles are many, obtaining expression profiles of an organism growing in tissue will probably reveal strategies for growth and survival in the host's microenvironment. Identifying these colonization strategies and their cognate expression patterns involves a ‘deconstruction’ process that combines bioinformatics analysis and in vitro DNA array experimentation.
The modular structure of Escherichia coli threonyl‐tRNA synthetase as both an enzyme and a regulator of gene expression
Authors: Caillet Joël , Nogueira Teresa , Masquida Benoît , Winter Flore , Graffe Monique , Dock‐Brégeon Anne‐Catherine , Torres‐Larios Alfredo , Sankaranarayanan Rajan , Westhof Eric , Ehresmann Bernard , Ehresmann Chantal , Romby Pascale , Springer Mathias 
Published: March 2003

SummaryIn addition to its role in tRNA aminoacylation, Escherichia coli threonyl‐tRNA synthetase is a regulatory protein which binds a site, called the operator, located in the leader of its own mRNA and inhibits translational initiation by competing with ribosome binding. This work shows that the two essential steps of regulation, operator recognition and inhibition of ribosome binding, are performed by different domains of the protein. The catalytic and the C‐terminal domain of the protein are involved in binding the two anticodon arm‐like structures in the operator whereas the N‐terminal domain of the enzyme is responsible for the competition with the ribosome. This is the first demonstration of a modular structure for a translational repressor and is reminiscent of that of transcriptional regulators. The mimicry between the operator and tRNA, suspected on the basis of previous experiments, is further supported by the fact that identical regions of the synthetase recognize both the operator and the tRNA anticodon arm. Based on these results, and recent structural data, we have constructed a computer‐derived molecular model for the operator‐threonyl‐tRNA synthetase complex, which sheds light on several essential aspects of the regulatory mechanism.
Electrical behaviour of interleukin‐1 beta (IL‐1β) and prostaglandin‐E2 (PGE2) on colonic myenteric neurones
Authors: Kelles A. , Janssens J. , Tack J. 
Published: March 2003

Abstract
Intracellular recordings were used to examine the effects on electrical and synaptic behaviour of interleukin (IL)‐1β and prostaglandin E2(PGE2) on myenteric neurones of the guinea‐pig colon. Application of IL‐1β and PGE2resulted in a concentration‐dependent slow depolarization with enhanced spike discharge in, respectively, 45% (21/47) and 83% (33/41) of the impaled colonic neurones. Administration of IL‐1β in three neurones (6%) elicited a hyperpolarization. Responses remained during tetrodotoxin application, indicative of a direct effect of both substances on the impaled neurones. The effects of IL‐1β remained in the presence of indomethacine, a prostaglandin synthase inhibitor. Responses were seen in both nitric oxide synthase‐ and choline acetyl transferase‐immunoreactive neurones. IL‐1β evoked a 26% reduction of the fast excitatory postsynaptic potential. These results indicate that the application of IL‐1β and PGE2evoke direct excitatory actions on a subset of myenteric neurones. For IL‐1β, direct inhibition and presynaptic inhibition of the fast excitatory postsynaptic potential has also been found. In the distal colon, responses to IL‐1β are not mediated through PGE2pathways.
Small intestinal transections decrease the occurrence of tapeworm‐induced myoelectric patterns in the rat
Authors: Dwinell K. L. , Bass P. , Zou F. , Oaks J. A. 
Published: March 2003

Abstract
Luminal infection by the noninvasive tapeworm, H. diminuta, alters rat small intestinal myoelectric activity. The significance of continuity between small intestinal enteric nervous system (ENS) and that of both the stomach/pylorus and colon/caecum regarding the induction of tapeworm‐altered myoelectric patterns was evaluated. A total of 32 rats were implanted with four serosal electrodes placed at sites in the duodenum through the mid‐jejunum. Sixteen of the 32 rats underwent intestinal transections and anastomoses at both the duodenum and ileum. After recording myoelectrical activity of both normal and transected intestines, eight rats from each group (normal and transected) were infected with H.diminuta. Phase III frequency, duration of the migrating myoelectric complex (MMC), slow wave frequency, percentage of slow waves associated with spike potentials and the occurrence of the the two tapeworm‐initiated myoelectric patterns, repetitive bursts of action potentials (RBAP) and sustained spike potentials (SSP), were measured. In infected rats, the frequency of the RBAP and SSP electric patterns were significantly reduced by the double transection. Intestinal transection did not affect the other changes caused by infection, such as decreased MMC phase III frequency and percentage of slow waves associated with spike potentials. In conclusion, a small intestinal ENS in continuity with other segments of the GI tract is required to generate maximal numbers of tapeworm‐induced SSP and RBAP myoelectric activity in the small intestine of the rat.
Ageing of substantia nigra in humans:  cell loss may be compensated by hypertrophy
Authors: Cabello C. R. , Thune J. J. , Pakkenberg H. , Pakkenberg B. 
Published: March 2003

In a stereological study of the human substantia nigra (SN), the total number of melanin‐positive and melanin‐negative neurones from 28 male subjects aged 19–92 years was estimated using a uniform sampling design and optical disectors. There was a significant decrease in the total number of melanin‐positive neurones as a function of age (r2=0.18, residual‐CV=0.35, 2P=0.032). Using the rotator method, the size distribution of the melanin‐positive neurones was estimated and showed a significant difference in mean cell volume of melanin‐positive neurones between the seven youngest (21 077 µm3) and the seven oldest individuals (32 011 µm3), 2P=0.022. Using a combination of the total number of melanin‐positive neurones and their size distribution, the total perikaryon volume of melanin‐positive neurones could be estimated and showed no decrease with increasing age (r2=0.01, residual‐CV=0.41, 2P=0.62).Age‐related decline in dopamine‐transporter neurones within the SN might explain the occurrence of extrapyramidal symptoms in many elderly individuals. Although age‐related cell hypertrophy is usually considered to be an indication of cell degeneration or necrosis, this might not always be the case. The fact that motor symptoms, although present in many of the elderly, are of a limited nature despite the high percentage of lost neurones could be due to a compensatory increase in the cell body of dopamine‐producing SN neurones. Thus, the total amount of cell substance capable of producing the essential transmitters might not be reduced to a critically low level as a result of ageing.
OLIG‐1 and 2 gene expression and oligodendroglial tumours
Authors: Hoang‐Xuan K. , Aguirre‐Cruz L. , Mokhtari K. , Marie Y. , Sanson M. 
Published: March 2003

OLIG 1/2 genes encode basic helix‐loop‐helix transcription factors that play a critical role in motor neurone and oligodendrocyte fate specification during development. Two recent studies in which OLIG transcripts were detected by in situ hybridization have reported a high expression of the OLIG genes in oligodendrogliomas. This suggests that the detection of these lineage markers could become an adjunct to the classic morphological diagnosis of these tumours. There are problems in the diagnosis of oligodendroglioma. To date, all other known oligodendrocyte lineage markers have failed to label specifically neoplastic oligodendrocytes. Deletions on chromosome 1p and 19q are much more frequent in oligodendrogliomas than in astrocytomas but these molecular alterations are not constant. For the future, when routinely available, immunohistochemical techniques using anti‐OLIG antibodies on paraffin embedded tissues will allow a systematic study of a large series of tumours so that we will know the specificity and sensitivity of this investigation in diagnosis.At another level, it is possible that expression of OLIG in neoplastic oligodendrocyte might participate in the oncogenesis of oligodendrogliomas. Initial work suggests that this is probably not the case. However further in vitro and in vivo studies analysing the functional consequence of OLIG overexpression in terms of proliferation and tumour progression are needed.
Abnormal endothelial tight junctions in active lesions and normal‐appearing white matter in multiple sclerosis
Authors: McQuaid S. , Plumb J. , Mirakhur M. , Kirk J. 
Published: March 2003

Introduction:  Increased blood–brain barrier permeability is a feature of new and expanding inflammatory lesions in multiple sclerosis (MS). The pathological mechanism for this increased permeability has not been demonstrated.Materials and methods:  Frozen sections from neuropathologically characterized active plaques and normal‐appearing white matter (NAWM) areas in 13 cases of MS were graded according to the relative abundance of oil‐red O (ORO)‐positive cells. Using single and double immunofluorescence and confocal scanning laser microscopy, the tight junction (TJ)‐associated proteins ZO‐1 and occludin were examined in relation to endothelial integrity (Ulex), blood–brain barrier (BBB) leakage (fibrinogen), lymphocytic infiltration and macrophage/microglial activation (HLA‐DR). Blood vessels (10–50 per section) were systematically scanned to acquire image data sets for offline analysis.Results:  TJ abnormalities (i.e. beading, interruption or absence of fluorescence, separation or opening of junctions) were frequent (affecting 40% of vessels) in ORO‐positive active plaques, but less frequent in NAWM (<15%) and in normal (2%) and neurological controls (<6%). ‘Open’ junctions were seen both in active ORO‐positive lesions and in inflamed blood vessels in NAWM.Conclusions:  These results suggest that disrupted TJs, arising during the acute inflammatory phase of MS, could be responsible for much of the BBB leakage seen in enhancing MRI lesions in vivo.
A new technique, which clearly distinguishes fibre types in fixed muscle tissue
Authors: Behan W. M. H. , Cossar D. W. , Madden H. A. , McKay I. C. 
Published: March 2003

Aims:  A method of distinguishing between type 1 and 2 skeletal muscle fibres in wax‐embedded tissue is needed. The ATPase method is the basis for fibre identification on frozen tissue and a new method should not give significantly different results. Isoforms of myosin and myofibrillar ATPase are known to correlate.Materials and methods:  We devised an immunohistochemical double‐labelling (IHC) protocol using monoclonal antibodies to fast and slow myosin. We compared results in the two methods by morphometric analysis of frozen muscle and then applied the method to paraffin‐embedded tissue.Results:  On frozen sections there were no significant differences (P = 0.57) in the percentages of type 1 (46% IHC method vs. 48% ATPase) or type 2 fibres (54% vs. 52%) and 2a and 2b subtypes were distinguished easily. Cross‐sectional area (in µm2), diameter (µm) and form factor were all similar. Various diagnostic samples of wax embedded tissue were then examined. These gave excellent results with clear colour contrast: type 1 fibres, black and type 2 fibres, red (see examples).Conclusion:  An IHC method based on the fast and slow isoforms of myosin gives similar results to the ATPase method while providing an important advantage in its applicability to wax‐embedded muscle.
Dural haemorrhage in non‐traumatic infant deaths: does it explain the bleeding in ‘shaken baby syndrome’?
Authors: Geddes J. F. , Tasker R. C. , Hackshaw A. K. , Nickols C. D. , Adams G. G. W. , Whitwell H. L. , Scheimberg I. 
Published: March 2003

J. F. Geddes, R. C. Tasker, A. K. Hackshaw, C. D. Nickols, G. G. W. Adams, H. L. Whitwell and I. Scheimberg (2003) Neuropathology and Applied Neurobiology 29, 14–22

Dural haemorrhage in non‐traumatic infant deaths: does it explain the bleeding in ‘shaken baby syndrome’?A histological review of dura mater taken from a post‐mortem series of 50 paediatric cases aged up to 5 months revealed fresh bleeding in the dura in 36/50, the bleeding ranging from small perivascular haemorrhages to extensive haemorrhage which had ruptured onto the surface of the dura. Severe hypoxia had been documented clinically in 27 of the 36 cases (75%). In a similar review of three infants presenting with classical ‘shaken baby syndrome’, intradural haemorrhage was also found, in addition to subdural bleeding, and we believe that our findings may have relevance to the pathogenesis of some infantile subdural haemorrhage. Recent work has shown that, in a proportion of infants with fatal head injury, there is little traumatic brain damage and that the significant finding is craniocervical injury, which causes respiratory abnormalities, severe global hypoxia and brain swelling, with raised intracranial pressure. We propose that, in such infants, a combination of severe hypoxia, brain swelling and raised central venous pressure causes blood to leak from intracranial veins into the subdural space, and that the cause of the subdural bleeding in some cases of infant head injury is therefore not traumatic rupture of bridging veins, but a phenomenon of immaturity. Hypoxia with brain swelling would also account for retinal haemorrhages, and so provide a unified hypothesis for the clinical and neuropathological findings in cases of infant head injury, without impact or considerable force being necessary.
Stress and preterm delivery: a conceptual framework
Authors: Hogue Carol J.R. , Hoffman Susie , Hatch Maureen C. 
Published: March 2003

Numerous epidemiological studies of various kinds of stress and preterm delivery have produced either negative or weakly positive results. Those inconclusive findings could be either because of the absence of an association or because of recognised methodological problems that may have masked an association. The biological plausibility of the stress hypothesis provides one rationale for continuing stress research, using better study designs. To further this agenda, we propose an epidemiological model, based on the classic ‘host, environment, agent’ triangle of epidemiological causality. The host is the individual woman, more or less susceptible to stressor‐induced pathology. The environment includes the social and cultural conditions that are ongoing stressors as well as social and cultural modifiers of stress e.g. those factors that may influence how a particular stressor is experienced or what the physical response to it may be. The agent is the immediate emotional or physical stressor requiring her response. We draw from recent literature, published principally since 1990, to illustrate this model.This epidemiological model posits that whether the individual is overwhelmed by stressors depends not only on the strength of the agents but also upon host susceptibility to stress, as well as the background level of acute, environmental and contextual stressors, and the moderating influence of host, environmental and contextual resources for handling stress. Future research needs to be based on stress hypotheses that include all sides of the triangle, data collection instruments that adequately capture relevant stressors and stress responses, and analytical techniques capable of handling complex, multilevel relationships.