bluuebunny/crossref_metadata_2025_split huggingface dataset:
A novel Myb‐related protein involved in transcriptional activation of encystation genes in Giardia lamblia
Authors: Sun Chin‐Hung , Palm Daniel , McArthur Andrew G. , Svärd Staffan G. , Gillin Frances D. 
Published: March 2003

Summary Giardia lamblia
is an important human intestinal parasite that survives outside of the host by differentiation of trophozoites into infectious cysts. Transcriptional regulation is key for encystation gene expression, but the mechanisms are unknown.
Giardia
genome database searches identified a
myb
‐like gene (
gmyb2
) whose expression increased during encystation. Epitope‐tagged gMyb2 localized to both nuclei. DNA binding and mutation analysis showed that gMyb2 binds specifically to C(T/A)ACAG, a c‐Myb‐like target sequence in the promoters of encystation‐induced genes encoding gMyb2, three cyst wall proteins and G6PI‐B, a key enzyme in cyst wall polysaccharide biosynthesis. gMyb2 binding sites were not found in the upstream regions of 31 other giardial genes. Deletion of the putative gMyb2 binding site greatly reduced encystation‐specific promoter activity of
g6pi‐b
. Fusion of gMyb2 binding sites to the constitutive
ran
promoter or
g6pi‐b promoter deletion lacking the gMyb2 binding site in‐duced encystation‐specific expression. gMyb2 may play an important role in transcriptional regulation of encystation genes, and may help co‐ordinate synthesis of cyst wall proteins and polysaccharide. gMyb2 is the first giardial transcription factor to be functionally identified and the first that is associated with upregulation of encystation genes. This work provides a model for study of differential gene regulation in early diverging eukaryotic organisms.
CesT is a bivalent enteropathogenicEscherichia colichaperone required for translocation of both Tir and Map
Authors: Creasey Elizabeth A. , Delahay Robin M. , Bishop Alexandra A. , Shaw Robert K. , Kenny Brendan , Knutton Stuart , Frankel Gad 
Published: March 2003

SummaryMap is an enteropathogenicEscherichia coli(EPEC) protein that is translocated into eukaryotic cells by a type III secretion system. Although not required for the induction of attaching and effacing (A/E) lesion formation characteristic of EPEC infection, translocated Map is suggested to disrupt mitochondrial membrane potential, which may impact upon subsequent functions of the organelle such as control of cell death. Before secretion, many effector proteins are maintained in the bacterial cytosol by association with a specific chaperone. In EPEC, chaperones have been identified for the effector proteins translocated intimin receptor (Tir) and EspF, and for the translocator proteins EspB and EspD. In this study, we present evidence that the Tir‐specific chaperone, CesT, also performs a chaperone function for Map. Using a combination of biochemical approaches, we demonstrate specific interaction between CesT and Map. Similar to other chaperone–effector pairings, binding is apparent at the amino‐terminus of Map and is indicated to proceed by a similar mechanism to CesT:Tir interaction. Map secretion from acesTmutant strain (SE884) is shown to be reduced and, importantly, its translocation from this strain after infection of HEp‐2 cells is almost totally abrogated. Although other chaperones are reported to have a bivalent binding specificity, CesT is the first member of its family that chaperones more than one protein for translocation.
Amiodarone induces a caffeine‐inhibited, MID1‐depedent rise in free cytoplasmic calcium in Saccharomyces cerevisiae
Authors: Courchesne William E. , Ozturk Sedide 
Published: March 2003

SummaryCalcium signalling is involved in myriad cellular processes such as mating morphogenesis. Mating in yeast induces changes in cell morphology with a concomitant increase in calcium uptake that is dependent on the MID1 and CCH1 genes. Mid1p and Cch1p are believed to function in a capacitive calcium entry (CCE)‐like process. Amiodarone alters mammalian calcium channel activity but, despite its clinical importance, its molecular mechanisms are not clearly defined. We have shown previously that amiodarone has fungicidal activity against a broad array of fungi. We show here that amiodarone causes a dramatic increase in cytoplasmic calcium ([Ca2+]cyt) in Saccharomyces cerevisiae. The majority of this increase is dependent on extracellular Ca2+ nonetheless, a significant increase in [Ca2+]cyt is still induced by amiodarone when no uptake of extracellular Ca2+ can occur. The influx of extracellular Ca2+ may be a direct effect of amiodarone on a membrane transporter or may be by a CCE mechanism. Uptake of the extracellular Ca2+ is inhibited by caffeine and reduced in strains deleted for the mid1 gene, but not in cells deleted for cch1. Our data are the first demonstrating control of yeast calcium channels by amiodarone and caffeine.
DNA gyrase requirements distinguish the alternate pathways of Mu transposition
Authors: Sokolsky Tanya D. , Baker Tania A. 
Published: March 2003

SummaryThe MuA transposase mediates transposition of bacteriophage Mu through two distinct mechanisms. The first integration event following infection occurs through a non‐replicative mechanism. In contrast, during lytic growth, multiple rounds of replicative transposition amplify the phage genome. We have examined the influence of gyrase and DNA supercoiling on these two transposition pathways using both a gyrase‐inhibiting drug and several distinct gyrase mutants. These experiments reveal that gyrase activity is not essential for integration; both lysogens and recombination intermediates are detected when gyrase is inhibited during Mu infection. In contrast, gyrase inhibition causes severe defects in replicative transposition. In two of the mutants, as well as in drug‐treated cells, replicative transposition is almost completely blocked. Experiments probing for formation of MuA–DNA complexes in vivo reveal that this block occurs very early, during assembly of the transposase complex required for the catalytic steps of recombination. The findings establish that DNA structure‐based signals are used differently for integrative and replicative transposition. We propose that transposase assembly, the committed step for recombination, has evolved to depend on different DNA /architectural signals to control the reaction outcome during these two distinct phases of the phage life cycle.
Glycolipid depletion in antimicrobial therapy
Authors: Svensson Majlis , Frendeus Björn , Butters Terry , Platt Frances , Dwek Raymond , Svanborg Catharina 
Published: March 2003

SummaryMucosal pathogens target sites of infection through specific adherence to host glycoconjugate receptors. As a consequence, depletion of such receptors from the cell surface may be expected to inhibit attachment, impair bacterial colonization and reduce the activation of mucosal inflammation. We have used the glucose analogue and glycosphingolipid (GSL) biosynthesis inhibitor N‐butyldeoxynojirimycin (NB‐DNJ) to deplete human uroepithelial cells and the murine urinary tract mucosa of receptors for P‐fimbriated Escherichia coli. NB‐DNJ blocks the ceramide‐specific glucosyltransferase, which catalyses the formation of glucosyl ceramide (GlcCer), the precursor for GSLs. The inhibitor was shown to decrease the GSL content in a dose‐dependent way, and depletion markedly inhibited P‐fimbriated bacterial attachment in vitro. NB‐DNJ‐fed C3H/HeN mice were depleted of GSLs in vivo and showed reduced susceptibility to experimental urinary tract infection with P‐fimbriated E. coli. The mucosal inflammatory response was impaired, as shown by reduced chemokine secretion and lower neutrophil recruitment, and the bacteria colonized the urinary tract less efficiently than in normal mice. These results confirmed the role of P fimbriae‐mediated adherence for colonization and inflammation and point to an interesting alternative to antibiotic treatment for urinary tract infection.
The dual roles of AlgG in C‐5‐epimerization and secretion of alginate polymers in Pseudomonas aeruginosa
Authors: Jain Sumita , Franklin Michael J. , Ertesvåg Helga , Valla Svein , Ohman Dennis E. 
Published: March 2003

Summary Pseudomonas aeruginosa
strains causing chronic pulmonary infections in cystic fibrosis patients produce high levels of alginate, an exopolysaccharide that confers a mucoid phenotype. Alginate is a linear polymer of
d
‐mannuronate (M) and variable amounts of its C‐5‐epimer,
l
‐guluronate (G). AlgG is a periplasmic C‐5‐epimerase that converts poly
d
‐mannuronate to the mixed M+G sequence of alginate. To understand better the role and mechanism of AlgG activity, a mutant was constructed in the mucoid strain FRD1 with a defined non‐polar deletion of
algG
. Instead of producing poly mannuronate, the
algG
deletion mutant secreted dialysable uronic acids, as does a mutant lacking the periplasmic protein AlgK. High levels of unsaturated ends and the nuclear magnetic resonance spectroscopy pattern revealed that the small, secreted uronic acids were the products of extensive polymer digestion by AlgL, a periplasmic alginate lyase co‐expressed with AlgG and AlgK. Thus, AlgG is bifunctional with (i) epimerase activity and (ii) a role in protecting alginate from degradation by AlgL during transport through the periplasm. AlgK appears to share the second role. AlgG and AlgK may be part of a periplasmic protein complex, or scaffold, that guides alginate polymers to the outer membrane secretin (AlgE). To characterize the epimerase activity of AlgG further, the
algG4
allele of poly mannuronate‐producing FRD462 was shown to encode a protein lacking only the epimerase function. The sequence of
algG4 has a Ser‐272 to Asn substitution in a serine–threonine‐rich and conserved region of AlgG, which revealed a critical residue for C‐5‐epimerase activity.
SeqA‐mediated stimulation of a promoter activity by facilitating functions of a transcription activator
Authors: Słomińska Monika , Konopa Grażyna , Ostrowska Justyna , Kędzierska Barbara , Grzegorz Węgrzyn  , Węgrzyn Alicja 
Published: March 2003

SummaryIt was demonstrated recently that the SeqA protein, a main negative regulator of Escherichia coli chromosome replication initiation, is also a specific transcription factor. SeqA specifically activates the bacteriophage λpR promoter while revealing no significant effect on the activity of another λ promoter, pL. Here, we demonstrate that lysogenization by bacteriophage λ is impaired in E. coli seqA mutants. Genetic analysis demonstrated that CII‐mediated activation of the phage pI and paQ promoters, which are required for efficient lysogenization, is less efficient in the absence of seqA function. This was confirmed in in vitro transcription assays. Interestingly, SeqA stimulated CII‐dependent transcription from pI and paQ when it was added to the reaction mixture before CII, although having little effect if added after a preincubation of CII with the DNA template. This SeqA‐mediated stimulation was absolutely dependent on DNA methylation, as no effects of this protein were observed when using unmethylated DNA templates. Also, no effects of SeqA on transcription from pI and paQ were observed in the absence of CII. Binding of SeqA to templates containing the tested promoters occurs at GATC sequences located downstream of promoters, as revealed by electron microscopic studies. In contrast to pI and paQ, the activity of the third CII‐dependent promoter, pE, devoid of neighbouring downstream GATC sequences, was not affected by SeqA both in vivo and in vitro. We conclude that SeqA stimulates transcription from pI and paQ promoters in co‐operation with CII by facilitating functions of this transcription activator, most probably by allowing more efficient binding of CII to the promoter region.
Membrane localization of the ToxR winged‐helix domain is required for TcpP‐mediated virulence gene activation in Vibrio cholerae
Authors: Crawford J. Adam , Krukonis Eric S. , DiRita Victor J. 
Published: March 2003

SummaryToxR is a bitopic membrane protein that controls virulence gene expression in Vibrio cholerae. Its cytoplasmic domain is homologous to the winged helix–turn–helix (‘winged helix’) DNA‐binding/transcription activation domain found in a variety of prokaryotic and eukaryotic regulators, whereas its periplasmic domain is of ill‐defined function. Several genes in V. cholerae are regulated by ToxR, but by apparently different mechanisms. Whereas ToxR directly controls the transcription of genes encoding two outer membrane proteins, OmpU and OmpT, it co‐operates with a second membrane‐localized transcription factor called TcpP to activate transcription of the gene encoding ToxT, which regulates transcription of cholera toxin (ctxAB) and the toxin‐co‐regulated pilus (tcp). To determine the requirements for gene activation by ToxR, different domains of the protein were analysed for their ability to control expression of toxT, ompU and ompT. Soluble forms of the cytoplasmic winged‐helix domain regulated ompU and ompT gene expression properly but did not activate toxT transcription. Membrane localization of the winged helix was sufficient for both omp gene regulation and TcpP‐dependent toxT transcription, irrespective of the type of periplasmic domain or even the presence of a periplasmic domain. These results suggest that (i) the major function for membrane localization of ToxR is for its winged‐helix domain to co‐operate with TcpP to activate transcription; (ii) the periplasmic domain of ToxR is not required for TcpP‐dependent activation of toxT transcription; and (iii) membrane localization is not a strict requirement for DNA binding and transcription activation by ToxR.
Video‐based spatio‐temporal maps for analysis of gastric motility in vitro: effects of vagal stimulation in guinea‐pigs
Authors: Berthoud H‐R. , Hennig G. , Campbell M. , Volaufova J. , Costa M. 
Published: March 2003

Abstract Our aim was to evaluate topographically specific gastric motility changes induced by graded vagal activation. A recently developed method of constructing spatio‐temporal maps of motility from video movies was adapted to the in vitro perfused guinea‐pig stomach with an intact vagal nerve supply. In the unstimulated preparation, spontaneous activity was low or absent. Bilateral vagal stimulation with frequencies as low as 0.2 Hz triggered weak anally, and in some cases orally, propagating antral contractions at rates of about 5–6 min−1. Upon stimulation with higher frequencies, antral contractions increased significantly in length (starting more proximally) and amplitude, and produced large pressure peaks of up to 25 hPa, with maximal effects at 2–4 Hz. In contrast, the speed of propagation and the interval between peristaltic waves did not change with vagal stimulation at any frequency. Vagal stimulation also produced a significant and frequency‐dependent enlargement of the fundus with a maximal effect at 4 Hz. It is concluded that a very low tonic vagal activity is apparently necessary and sufficient to express basic antral motility, while more sustained vagal activity is necessary for high‐amplitude gastric contractions and significant sustained fundic relaxation. The constant interval between propagating contractions supports the concept that vagal input impinges on intrinsic enteric neural circuits that have a modulatory role in the myogenic mechanism underlying slow‐wave peristalsis, rather than directly on gastric musculature.
Cholecystokinin octapeptide increases rectal sensitivity to pain in healthy subjects
Authors: Sabaté J‐M. , Gorbatchef C. , Flourié B. , Jian R. , Coffin B. 
Published: March 2003

Abstract  Hypersensitivity during rectal distension has been demonstrated in irritable bowel syndrome (IBS). Studies performed in animals and indirect data in humans suggest that cholecystokinin (CCK) could modulate visceral sensations. The aim of this study was to assess the effects of i.v. infused sulphated cholecystokinin octapeptide (CCK‐OP) on rectal sensitivity in response to distension. In eight healthy subjects, rectal sensitivity and compliance were determined during a randomized double‐blind study, with four sessions each separated by 7 days. Sensory thresholds and rectal compliance were assessed during slow‐ramp (40 mL min−1) and rapid‐phasic distensions (40 mL s−1, 5 mmHg stepwise, 1‐min duration), and were compared before and during continuous infusion of either saline or CCK‐OP at 5, or 20 or 40 ng kg−1 h−1. During rapid phasic distension but not during slow ramp distension, CCK‐OP at 40 ng kg−1 h−1 produced a significant decrease in sensory thresholds compared with the basal period. Rectal compliance was not modified by any infusion. At pharmacological doses, CCK‐OP decreases sensory thresholds during rapid phasic distension that may preferentially stimulate serosal mechanoreceptors, but has no effect on mucosal mechanoreceptors stimulated during slow ramp distensions. Modulation of rectal sensitivity by CCK could be implicated in the pathogenesis of the rectal hypersensitivity observed in IBS.
From our own correspondent
Authors: Silverman William A. 
Published: March 2003

Secrecy and rainmaking in medical research There is a culture shift under way. The universities’ central product – knowledge – used to be regarded as a ‘common good,’ but it is in the process of being reappraised as ‘intellectual property’ . . . which must be walled off. This balkanization of knowledge, packaged for sale, will alter our universities and weaken them. Nobel laureate John C. Polanyi1
Perinatal mortality in twins and factors influencing mortality in Japan, 1980–98
Authors: Imaizumi Yoko 
Published: March 2003

SummaryThe perinatal mortality rate (PMR) in twins was analysed using Japanese vital statistics during the period 1980–98. There was a total of 1992 twin perinatal deaths. The PMR in twins significantly decreased from 91 per 1000 births in 1980 to 31 per 1000 in 1998. The PMR was higher in males than females, but the differences between the sexes decreased over time. It was significantly higher in the second‐born than the first‐born of the twins. The fetal death rate was 2.8 times higher in monozygotic than dizygotic twins. The PMR decreased to one‐sixth for the maternal age group ≥40 years, one‐fifth for <20 years, and between one‐third and a half for 20–39 years during the period 1980–98. It was lowest for birthweights (BW) between 2500 g and 2999 g during the entire period; the PMR decreased with gestational age (GA) up to 38–39 weeks and increased thereafter. The effect of BW on the PMR was greater than that of GA except in the shorter GA group. The proportion of twin perinatal deaths with extremely low BW (<1000 g) increased from 50% in 1980 to 68% in 1998. Thus, the declining PMR was unlikely to be due to the improvement in BW in twins. It is likely that it is related to the improved medical management of twins during the perinatal period and the first week of life.
Families with a perinatal death: is there an association between the loss and the birthweight of surviving siblings?
Authors: Melve Kari Klungsøyr , Skjærven Rolv , Øyen Nina 
Published: March 2003

SummaryOur objective was to study birthweight among surviving siblings in families with and without a perinatal loss, and to evaluate whether different causes of death were associated with the results. Data were for 1967–98 from the Norwegian Medical Birth Registry. Births were organised with the mother as the observation unit through the personal identification number, providing sibship files. We analysed 550 930 sibships with at least two singletons, 208 586 sibships with at least three singletons and 45 675 sibships with at least four singleton births. We compared mean birthweight and gestational age between infants in sibships with and without a perinatal loss, total losses and the different causes of death. Surviving siblings in families with a perinatal loss had significantly lower mean birthweights than their counterparts in unaffected families, after adjusting for gestational age, interpregnancy interval, time period and marital status. An exception was found when cause of death was a birth defect, when growth retardation among surviving siblings was not found on average. We conclude that families who have lost an infant because of a birth defect do not appear to have an increased risk of adverse birth outcome associated with growth restriction.
Population‐based outcomes after acute antenatal transfer
Authors: Fenton Alan C. , Ainsworth Sean B. , Sturgiss Stephen N. 
Published: March 2003

SummaryAcute antenatal transfer to specialist centres is an accepted practice but few or no regular data are collected regarding the numbers of transfers performed or subsequent pregnancy outcome. We wished to determine the numbers, and the maternal and fetal outcomes following acute antenatal transfer between consultant obstetric units in the former Northern Region of the UK over a 12‐month period (1 January–31 December 99). This is a geographically defined population in terms of provision of perinatal services. All acute antenatal transfers were notified centrally. Data pertaining to each transfer were collected at the time of transfer. Subsequent maternal and fetal outcomes were determined from patient records and neonatal databases. The regional annual acute antenatal transfer rate was 3.7 per 1000 deliveries. Most were for fetal reasons, although transfer rates varied between hospitals. The decision to transfer was influenced by distance and availability of paediatric staff. Even units that have similar characteristics show considerable variation in their transfer rates. No adverse incidents occurred during transfer and no major changes in maternal management occurred following transfer. Twenty‐four per cent of women remained undelivered following transfer. Women with preterm labour in the absence of ruptured membranes were less likely to deliver than those transferred for other reasons and if they did deliver, their infants were also less likely to need intensive care. We believe audit of acute antenatal transfers should be routinely undertaken. Numbers of transfers might be reduced if delivery and the need for neonatal intensive care could be predicted with greater accuracy. The psychological and financial costs of transfer to women and healthcare providers need to be addressed.
Epidemiological characteristics of retinoblastoma in children attending the Mexican Social Security Institute in Mexico City, 1990–94
Authors: Amozorrutia‐Alegría Víctor , Bravo‐Ortiz Juan Carlos , Vázquez‐Viveros Josefina , Campos‐Campos Laura , Mejía‐Aranguré Manuel , Juárez‐Ocaña Servando , Martínez‐García María del Carmen , Fajardo‐Gutiérrez Arturo 
Published: March 2003

SummaryThe object of this study is to present descriptive epidemiological characteristics of retinoblastoma (Rb) in children aged 0–14 years, seen at the Mexican Social Security Institute hospitals in Mexico City (MC) from 1990 to 1994. This is a retrospective, observational hospital survey. Clinical records of 52 Rb cases were reviewed; 39 were patients who did not reside in MC (non‐residents), and 13 were MC residents. The study period was 1990–94. The male/female ratio (M/F) was 1.6. Average annual incidence (AAI) was estimated by age and sex (rates per 1 000 000). Annual average percentage change (AAPC) in incidence rates was estimated in children from 0 to 14 years. The AAI for MC residents was 3.2; the highest rate being for those <1 year olds (rate of 20.8); AAPC was 6.9% [95% CI –27.5, 57.4]; the highest incidence was for the south‐eastern region of MC residents (rate of 5.9); 13 cases (25%) were diagnosed at stage III or IV, and 11 cases (21.2%) were bilateral. Incidence of Rb is similar to that in developed countries and shows no increasing trend. Patients from communities outside MC are more frequently diagnosed at stages III and IV.