bluuebunny/crossref_metadata_2025 huggingface dataset:
Low coronary driving pressure early in the course of myocardial infarction is associated with subendocardial remodelling and left ventricular dysfunction
Authors: Koike Marcia Kiyomi , De Carvalho Frimm Clovis , Cúri Mariana
Published: June 2007

Subendocardial remodelling of the left ventricular (LV) non‐infarcted myocardium has been poorly investigated. Previously, we have demonstrated that low coronary driving pressure (CDP) early postinfarction was associated with the subsequent development of remote subendocardial fibrosis. The present study aimed at examining the role of CDP in LV remodelling and function following infarction. Haemodynamics were performed in Wistar rats immediately after myocardial infarction (MI group) or sham surgery (SH group) and at days 1, 3, 7 and 28. Heart tissue sections were stained with HE, Sirius red and immunostained for α‐actin. Two distinct LV regions remote to infarction were examined: subendocardium (SE) and interstitium (INT). Myocyte necrosis, leucocyte infiltration, myofibroblasts and collagen volume fraction were determined. Compared with SH, MI showed lower CDP and LV systolic and diastolic dysfunction. Necrosis was evident in SE at day 1. Inflammation and fibroplasia predominated in SE as far as day 7. Fibrosis was restricted to SE from day 3 on. Inflammation occurred in INT at days 1 and 3, but at a lower grade than in SE. CDP correlated inversely with SE necrosis (r = −0.65, P = 0.003, at day 1), inflammation (r = −0.76, P < 0.001, at day 1), fibroplasia (r = −0.47, P = 0.04, at day 7) and fibrosis (r = −0.83, P < 0.001, at day 28). Low CDP produced progressive LV expansion. Necrosis at day 1, inflammation at days 3 and 7, and fibroplasia at day 7 correlated inversely with LV function. CDP is a key factor to SE integrity and affects LV remodelling and function following infarction.
Functional convergence in regulation of net CO2 flux in heterogeneous tundra landscapes in Alaska and Sweden
Authors: SHAVER G. R. , STREET L. E. , RASTETTER E. B. , VAN WIJK M. T. , WILLIAMS M.
Published: June 2007

Arctic landscapes are characterized by extreme vegetation patchiness, often with sharply defined borders between very different vegetation types. This patchiness makes it difficult to predict landscape‐level C balance and its change in response to environment.

Here we develop a model of net CO2 flux by arctic landscapes that is independent of vegetation composition, using instead a measure of leaf area derived from NDVI (normalized‐difference vegetation index).

Using the light response of CO2 flux (net ecosystem exchange, NEE) measured in a wide range of vegetation in arctic Alaska and Sweden, we exercise the model using various data subsets for parameter estimation and tests of predictions.

Overall, the model consistently explains ~80% of the variance in NEE knowing only the estimated leaf area index (LAI), photosynthetically active photon flux density (PPFD) and air temperature.

Model parameters derived from measurements made in one site or vegetation type can be used to predict NEE in other sites or vegetation types with acceptable accuracy and precision. Further improvements in model prediction may come from incorporating an estimate of moss area in addition to LAI, and from using vegetation‐specific estimates of LAI.

The success of this model at predicting NEE independent of any information on species composition indicates a high level of convergence in canopy structure and function in the arctic landscape.
Costs and benefits of fruiting to future reproduction in two dormancy‐prone orchids
Authors: SHEFFERSON RICHARD P. , SIMMS ELLEN L.
Published: June 2007

Reproduction is expected to occur at a cost to survival, growth or future reproduction. However, trade‐offs in long‐lived, clonal herbs have proven difficult to assess, particularly when they are prone to adult dormancy.

We assessed the costs of fruiting in a study of two species of lady's slipper orchid,Cypripedium candidumandC. parviflorum, growing sympatrically in a wet meadow in north‐eastern Illinois, USA, from 2000 to 2005.

First, we characterized flowering and fruiting in both populations. We found some differences between species, with 68.6 ± 5.7% (mean ± SE) and 43.5 ± 1.4% of sprouting plants flowering, while 33.6 ± 10.0% and 33.5 ± 8.1% of flowering plants fruited inC. candidumandC. parviflorum, respectively.

Next, we tested the survival, sprouting and flowering response to current fruiting using multistate mark–recapture statistics. The best‐fit model posited no cost of fruiting. However, according to a model parsimonious with the best‐fit model, fruiting may have resulted in a small cost to survival visible primarily in small‐sized individuals ofC. parviflorum(decrease from 0.846 in non‐fruiting but flowering plants to 0.824 in fruiting plants). In all cases, fruiting resulted in an increased probability of future flowering, suggesting that reproduction may have a higher priority in resource allocation than survival.

Finally, we tested the effects of fruiting on future fruiting using logistic regression for two years in which fruiting was particularly high, but detected no change in the probability of fruiting after fruiting.

Fruiting may increase in response to internal cues, perhaps related to nutrient uptake or storage, in addition to the obvious effects of pollination. The result may be that plants with greater access to nutrients or with greater stored reserves are more likely to flower each season. We suggest a need for further research exploring the internal mechanisms governing fruiting response in long‐lived, clonal herbs.
Biological Flora of the British Isles: Cirsium dissectum (L.) Hill (Cirsium tuberosum (L.) All. subsp. anglicum (Lam.) Bonnier; Cnicus pratensis (Huds.) Willd., non Lam.; Cirsium anglicum (Lam.) DC.)
Authors: DE VERE NATASHA
Published: June 2007

This account reviews information on all aspects of the biology of Cirsium dissectum (L.) Hill that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history and conservation.

Cirsium dissectum (meadow thistle) is a perennial, rhizomatous herb found in moist, nutrient poor grasslands and heathlands in north‐west Europe. It is readily distinguishable from other Cirsium species in the British Isles but has been considered a subspecies of C. tuberosum, along with C. filipendulum, in some other areas of Europe.

It is susceptible to being out‐competed by species that are able to increase biomass more rapidly. At more productive sites, greater nutrient availability increases the proportion of rosettes that flower, as well as rosette turnover. Seeds germinate readily under a range of conditions in the growth room and greenhouse but seedlings are very rarely found in the field. An examination of its population dynamics reveals that clonal propagation is the dominant form of reproduction, with the low number of seedlings primarily caused by very low establishment rates in vegetation stands.

Cirsium dissectum is relatively tolerant of drought and shade even though it is found in moist grasslands. At very low pH it suffers from ammonium and aluminium toxicity. As it has suffered habitat loss through drainage and succession, C. dissectum has declined in the British Isles and it is now endangered in Germany and the Netherlands.
The general transition metal (Tro) and Zn2+(Znu) transporters inTreponema pallidum: analysis of metal specificities and expression profiles
Authors: Desrosiers Daniel C. , Sun Yong Cheng , Zaidi Akbar A. , Eggers Christian H. , Cox David L. , Radolf Justin D.
Published: June 2007

Acquisition of transition metals is central to the struggle between a bacterial pathogen and its mammalian host. Previous studies demonstrated thatTreponema pallidumencodes a cluster‐9 (C9) ABC transporter (troABCD) whose solute‐binding protein component (TroA) ligands Zn2+and Mn2+with essentially equal affinities. Bioinformatic analysis revealed thatT. pallidumencodes an additional C9 transporter (tp0034–36) orthologous to Zn2+‐uptake (Znu) systems in other bacteria; the binding protein component, ZnuA, contains a His‐rich tract characteristic of C9 Zn2+‐binding proteins. Metal analysis and metal‐reconstitution studies demonstrated that ZnuA is a Zn2+‐binding protein; parallel studies confirmed that TroA binds Zn2+, Mn2+and Fe. Circular dichroism showed that ZnuA, but not TroA, undergoes conformational changes in the presence of Zn2+. Using isothermal titration calorimetry (ITC), we demonstrated that TroA binds Zn2+and Mn2+with affinities approximately 100‐fold greater than those previously reported. ITC analysis revealed that ZnuA contains multiple Zn2+‐binding sites, two of which are high‐affinity and presumed to be located within the binding pocket and His‐rich loop. Quantitative reverse transcription polymerase chain reaction oftroandznutranscripts combined with immunoblot analysis of TroA and ZnuA confirmed that both transporters are simultaneously expressed inT. pallidumand that TroA is expressed at much greater levels than ZnuA. Collectively, our findings indicate thatT. pallidumprocures transition metalsviathe concerted utilization of its general metal (Tro) and Zn2+(Znu) transporters. Sequestration of periplasmic Zn2+by ZnuA may free up TroA binding capacity for the importation of Fe and Mn2+.
The ammonium‐inactivated cyanobacterial glutamine synthetase I is reactivated in vivo by a mechanism involving proteolytic removal of its inactivating factors
Authors: Galmozzi Carla V. , Fernández‐Avila M. Jesús , Reyes José C. , Florencio Francisco J. , Muro‐Pastor M. Isabel
Published: June 2007

The Synechocystis sp. PCC 6803 glutamine synthetase type I (GS) activity is controlled by a process that involves protein–protein interaction with two inactivating factors (IF7 and IF17). Following addition of ammonium, the genes encoding these proteins, gifA and gifB, respectively, are derrepressed, leading to the synthesis of IF7 and IF17 and consequently GS is inactivated. Upon ammonium removal, the GS activity rapidly returns to the initial level within 20 min. In this study, we analyse the mechanism underlying GS reactivation and find that this process involves IF7 and IF17 degradation. We show that the presence of ammonium as nitrogen source enhances IF17 but not IF7 stability independently of gif gene transcription. Studies with Synechocystis crude extracts under different conditions revealed that IF7 and IF17 display different stabilities in vitro. We found that IF7 is degraded in vitro by the activity of metalloproteases. Furthermore, the involvement of soluble processing metallopeptidases in IF7 degradation has also been demonstrated in vivo, by analysing Synechocystis mutant strains devoid of genes of the prp family. Finally, using a Synechocystis strain lacking GS type I, we establish the crucial role of the target protein GS for in vivo IF7 and IF17 stability.
FrzZ, a dual CheY‐like response regulator, functions as an output for the Frz chemosensory pathway of Myxococcus xanthus
Authors: Inclán Yuki F. , Vlamakis Hera C. , Zusman David R.
Published: June 2007

Myxococcus xanthus utilizes two distinct motility systems for movement (gliding) on solid surfaces: adventurous motility (A‐motility) and social motility (S‐motility). Both systems are regulated by the Frz signal transduction pathway, which controls cell reversals required for directed motility and fruiting body formation. The Frz chemosensory system, unlike the Escherichia coli chemotaxis system, contains proteins with multiple response regulator domains: FrzE, a CheA–CheY hybrid protein, and FrzZ, a CheY–CheY hybrid protein. Previously, the CheY domain of FrzE was hypothesized to act as the response regulator output of the Frz system. In this study, using a genetic suppressor screen, we identified FrzZ and showed FrzZ is epistatic to FrzE, demonstrating that FrzZ is the principal output component of the pathway. We constructed M. xanthus point mutations in the phosphoaccepting aspartate residues of FrzZ and demonstrated the respective roles of these residues in group and single cell motility. We also performed in vitro assays and showed rapid phosphotransfer between the CheA domain of FrzE and each of the CheY domains of FrzZ. These experiments showed that FrzZ plays a direct role as an output of the Frz chemosensory pathway and that both CheY domains of FrzZ are functional.
Genomic analysis of protein–DNA interactions in bacteria: insights into transcription and chromosome organization
Authors: Wade Joseph T. , Struhl Kevin , Busby Stephen J. W. , Grainger David C.
Published: June 2007

Chromatin immunoprecipitation (ChIP) is a powerful method to measure protein–DNA interactions in vivo, and it can be applied on a genomic scale with microarray technology (ChIP‐chip). ChIP‐chip has been used extensively to map DNA–protein interactions across eukaryotic chromosomes. Here we review recent applications of ChIP‐chip to the study of bacteria, which provide important and unexpected insights into transcription and chromosome organization.
The (1,3)β‐d‐glucan synthase subunit Bgs1p is responsible for the fission yeast primary septum formation
Authors: Cortés Juan Carlos G. , Konomi Mami , Martins Ivone M. , Muñoz Javier , Moreno M. Belén , Osumi Masako , Durán Angel , Ribas Juan Carlos
Published: June 2007

Cytokinesis is a crucial event in the cell cycle of all living cells. In fungal cells, it requires co‐ordinated contraction of an actomyosin ring and synthesis of both plasmatic membrane and a septum structure that will constitute the new cell wall end. Schizosaccharomyces pombe contains four essential putative (1,3)β‐d‐glucan synthase catalytic subunits, Bgs1p to Bgs4p. Here we examined the function of Bgs1p in septation by studying the lethal phenotypes of bgs1+ shut‐off and bgs1Δ cells and demonstrated that Bgs1p is responsible and essential for linear (1,3)β‐d‐glucan and primary septum formation. bgs1+ shut‐off generates a more than 300‐fold Bgs1p reduction, but the septa still present large amounts of disorganized linear (1,3)β‐d‐glucan and partial primary septa. Conversely, both structures are absent in bgs1Δ cells, where there is no Bgs1p. The septum analysis of bgs1+‐repressed cells indicates that linear (1,3)β‐d‐glucan is necessary but not sufficient for primary septum formation. Linear (1,3)β‐d‐glucan is the polysaccharide that specifically interacts with the fluorochrome Calcofluor white in fission yeast. We also show that in the absence of Bgs1p abnormal septa are formed, but the cells cannot separate and eventually die.
Effective killing of the human pathogen Candida albicans by a specific inhibitor of non‐essential mitotic kinesin Kip1p
Authors: Chua Penelope R. , Roof David M. , Lee Yan , Sakowicz Roman , Clarke David , Pierce Dan , Stephens Thoryn , Hamilton Matthew , Morgan Brad , Morgans David , Nakai Takashi , Tomasi Adam , Maxon Mary E.
Published: June 2007

Kinesins from the bipolar (Kinesin‐5) family are conserved in eukaryotic organisms and play critical roles during the earliest stages of mitosis to mediate spindle pole body separation and formation of a bipolar mitotic spindle. To date, genes encoding bipolar kinesins have been reported to be essential in all organisms studied. We report the characterization of CaKip1p, the sole member of this family in the human pathogenic yeast Candida albicans. C. albicans Kip1p appears to localize to the mitotic spindle and loss of CaKip1p function interferes with normal progression through mitosis. Inducible excision of CaKIP1 revealed phenotypes unique to C. albicans, including viable homozygous Cakip1 mutants and an aberrant spindle morphology in which multiple spindle poles accumulate in close proximity to each other. Expression of the C. albicans Kip1 motor domain in Escherichia coli produced a protein with microtubule‐stimulated ATPase activity that was inhibited by an aminobenzothiazole (ABT) compound in an ATP‐competitive fashion. This inhibition results in ‘rigor‐like’, tight association with microtubules in vitro. Upon treatment of C. albicans cells with the ABT compound, cells were killed, and terminal phenotype analysis revealed an aberrant spindle morphology similar to that induced by loss of the CaKIP1 gene. The ABT compound discovered is the first example of a fungal spindle inhibitor targeted to a mitotic kinesin. Our results also show that the non‐essential nature and implementation of the bipolar motor in C. albicans differs from that seen in other organisms, and suggest that inhibitors of a non‐essential mitotic kinesin may offer promise as cidal agents for antifungal drug discovery.
RecA‐mediated excision repair: a novel mechanism for repairing DNA lesions at sites of arrested DNA synthesis
Authors: Bichara Marc , Pinet Isabelle , Lambert Iain B. , Fuchs Robert P. P.
Published: June 2007

In Escherichia coli, bulky DNA lesions are repaired primarily by nucleotide excision repair (NER). Unrepaired lesions encountered by DNA polymerase at the replication fork create a blockage which may be relieved through RecF‐dependent recombination. We have designed an assay to monitor the different mechanisms through which a DNA polymerase blocked by a single AAF lesion may be rescued by homologous double‐stranded DNA sequences. Monomodified single‐stranded plasmids exhibit low survival in non‐SOS induced E. coli cells; we show here that the presence of a homologous sequence enhances the survival of the damaged plasmid more than 10‐fold in a RecA‐dependent way. Remarkably, in an NER proficient strain, 80% of the surviving colonies result from the UvrA‐dependent repair of the AAF lesion in a mechanism absolutely requiring RecA and RecF activity, while the remaining 20% of the surviving colonies result from homologous recombination mechanisms. These results uncover a novel mechanism – RecA‐mediated excision repair – in which RecA‐dependent pairing of the mono‐modified single‐stranded template with a complementary sequence allows its repair by the UvrABC excinuclease.
The central nervous system in mucosal vaccination of rhesus macaques with simian immunodeficiency virus Δnef
Authors: Georgsson G. , Stahl‐Hennig C. , Tenner‐Racz K. , Überla K. , Stoiber H. , Uguccioni M. , Dierich M. , Ignatius R. , Steinman R. M. , Racz P.
Published: June 2007

We studied the central nervous system (CNS) of rhesus macaques during series of vaccination experiments in which attenuated simian immunodeficiency virus (SIV), SIVmac239Δnef,was applied to the tonsils and the animals were later challenged with pathogenic SIVmac251 or SHIV/89.6P via tonsils or rectum. The pathologic lesions were graded on a scale of 0–5. The lesions were in general very mild, with a score of 0.5, except for one case, in which the animal had progressed to simian AIDS (SAIDS) and had severe lesions of grade 4. Except for the SAIDS case, the most common lesions were meningitis, ependymitis, inflammation of choroid plexus, and astrocytosis. Invasion of the challenge virus, SIVmac251, and pathologic lesions were detected 4 days post infection. The main features of the pathological lesions were similar during short‐term follow‐up (4 days to 2 weeks) and long‐term follow‐up (23 to 56 weeks) after challenge. No significant difference was found between unvaccinated controls infected with the challenge viruses and vaccinated and challenged animals. The pathological lesions in the one SAIDS case consisted of extensive lesions of the white matter in connection with confluent ependymitis, indicating an invasion through the choroid plexus. The lesions were characterized by a myriad of multinucleated giant cells of macrophage origin, which showed, together with individual macrophages, strong labelling for viral RNA and proteins. Productive infection of astrocytes was a very rare finding. In three cases infected via tonsils with SIVmac239Δnefwithout challenge, we detected expression of Nef‐derived peptides, indicating a selective pressure for Nef functions in the CNS.
The analysis of recurrence risk as an epidemiological tool
Authors: Wilcox Allen J.
Published: June 2007

Recurrence risk provides information on the heterogeneity of risk in the population, and thus is useful for aetiological studies. While recurrence risk is observable in many areas of epidemiology, it is particularly accessible in the study of perinatal events. High recurrence rates of pregnancy problems suggest genetic causes, but can also reflect the presence of persistent environmental causes. Specific patterns of recurrence risk can provide further clues about the relative importance of genetic vs. environmental factors, for example through comparisons of recurring pregnancy problems in women who change their male partner and women who keep the same partner. Interpretation of recurrence risk is subject to confusion from bias and confounding, and some examples are discussed. In addition to providing information on causality, recurrence risk offers a means for more efficient design of aetiological studies.
Intergenerational exchange and perinatal risks: a note on interpretation of generational recurrence risks
Authors: Lie Rolv T.
Published: June 2007

Population‐based data that cover reproductive health outcomes across two complete generations have recently become available in the Nordic countries. Such data enable estimation of recurrence risks from one generation to the next of different conditions such as birth defects or pre‐eclampsia. Risks related to a singleton pregnancy involve the contribution of three individuals: the mother, the father and the fetus. A paternal contribution is mainly through the father’s contribution of half of the alleles of the fetus. A maternal contribution may occur in three fundamentally different ways. First, the mother provides half of the genomic alleles to the fetus, with contribution of paternal alleles completing the whole genome. Second, the mother provides the fetal environment and possible susceptibility to complications during pregnancy which she may have inherited from her mother. Finally, she provides the fetal mitochondria. Because of these different contributions, recurrence from mother to offspring is fundamentally different from recurrence from father to offspring. How recurrence risks reflect and shape the underlying contributions to overall perinatal risk is illustrated through a review of published data from Norway on gestational age, pre‐eclampsia and birth defects.
Partner change, birth interval and risk of pre‐eclampsia: a paradoxical triangle
Authors: Zhang Jun
Published: June 2007

Immunology has been hypothesised to play a critical role in the development of pre‐eclampsia. A number of epidemiological studies have shown that multiparous women who changed partner had an increased risk of pre‐eclampsia in the following pregnancy compared with multiparous women with the same partner. However, partner change is often associated with a long birth interval. Two recent papers using data from the same birth registry reported that, after controlling for birth interval, partner change was associated with a reduced risk of pre‐eclampsia. Based on a causal diagram, the author argues conceptually that birth interval is not a confounder but more likely to be a collider. Controlling for or stratifying birth interval in the association between partner change and risk of pre‐eclampsia could be inappropriate and may have produced a spurious association.
Partner change and perinatal outcomes: a systematic review
Authors: Zhang Jun , Patel Geeta
Published: June 2007

Epidemiological studies suggest that partner change may affect perinatal outcomes in subsequent pregnancies. We conducted a systematic review on the association between paternity change and perinatal outcomes. We searched the literature in MEDLINE using keywords ‘paternity’, ‘partner’, ‘pre‐eclampsia’, ‘preterm birth’, ‘low birth weight’, and ‘birth defects’ from 1966 to 2005. We identified 19 studies that examined the association between partner change and specific perinatal outcomes: 12 on pre‐eclampsia or hypertension in pregnancy, three on birth defects, three on preterm birth, and two on low birthweight.

Partner change was consistently associated with an increased risk of pre‐eclampsia or hypertension in pregnancy in 11 of 12 studies (the unadjusted relative risk [RR] ranging from 1.2 to 8.3). However, after controlling for birth interval as a confounder in multivariate analysis, two studies using the same birth registry data showed a modestly reduced risk in relation to partner change (RR = 0.84 and 0.73, respectively), while two studies found a slightly increased risk (both RR = 1.3). Retrospective cohort studies presented inconsistent findings on the association between partner change and risk of preterm birth and low birthweight. Finally, three population‐based cohort studies demonstrated that partner change significantly reduced the recurrence of the same or similar birth defects in subsequent births (RRs ranging from 0.1 to 0.76). We conclude that partner change reduces the risk of recurrent same birth defects. However, epidemiological evidence on the effect of partner change on pre‐eclampsia, preterm birth and low birthweight is inconclusive. Whether birth interval should be controlled for in the association between partner change and pre‐eclampsia warrants caution.
Measuring the accuracy and completeness of linking certificates for deliveries to the same woman
Authors: Adams Melissa M. , Kirby Russell S.
Published: June 2007

No standards exist for reporting the accuracy and completeness of pregnancy histories created by linking the birth and fetal death certificates for all the deliveries occurring to one woman. To link certificates, analysts use deterministic and/or probabilistic approaches. Errors in linkage occur randomly and non‐randomly. Any type of error can cause incorrect estimation of the magnitude of relationships. Methods for assessing linkage correctness are proposed. Analysts can detect errors in linkage by comparing the linkage results with the pregnancy history reported by the mother. The analyst interviews a random sample of women, ascertaining the dates and outcomes (stillbirth or live birth) for their births and, if the linkage used certificates from one state, the state where they occurred. For each woman, he/she then assesses the accuracy and completeness of this linkage by comparing it with her reported pregnancy history. An alternative approach is to chronologically sequence each woman's births. The parity for the most recent birth shows the number of babies born to the same woman and should equal the number of births that the analyst linked. In the absence of maternally reported pregnancy histories, an analyst can use data on the certificates to assess linkage correctness. Although this will show whether the correct number of births have been linked, it provides no information concerning the accuracy of linkages. It may be, however, the most universally applicable way of reporting the completeness of the linkage of deliveries.
Stage‐specific immune responses in human Necator americanus infection
Authors: GEIGER S. M. , CALDAS I. R. , MC GLONE B. E. , CAMPI‐AZEVEDO A. C. , DE OLIVEIRA L. M. , BROOKER S. , DIEMERT D. , CORRÊA‐OLIVEIRA R. , BETHONY J. M.
Published: June 2007

We describe how hookworms interact with their human hosts by comparing lymphocyte phenotyping, proliferative responses, and cytokine and chemokine secretion patterns in adults who are either mono‐infected with Necator americanus or egg‐negative controls resident in an area of high transmission in Brazil. Cellular immune responses against crude hookworm antigen extracts from different developmental stages were evaluated simultaneously. Principal component analysis (PCA) was used to reduce the standardized immune responses. Random effects multivariate regression was then used to investigate whether principal components (PC) differ between the two groups once potential confounders and effect modifiers have been accounted for. Although hookworm patients had reduced percentages of T and B cells, they had higher levels of activated CD4+ T and CD19+ B cells. This state of ‘immune activation’ coincided with lower proliferative responses, especially to third‐stage larval antigen. Cytokine levels in mono‐infected adults were also lower and characterized by a mixed Th1/Th2‐type profile. Excretory/secretory antigen from adult worms was a potent modulator of the immune response, resulting in diminished TNF‐α and IL‐10 secretion in peripheral blood mononuclear cells (PBMC) from hookworm infected patients. We propose that the longevity of hookworms in their human hosts results from a stage‐specific, down‐modulation of the immune response.
The role of the secretory immune response in the infection by Entamoeba histolytica
Authors: Carrero J. C. , Cervantes‐Rebolledo C. , Aguilar‐Díaz H. , Díaz‐Gallardo M. Y. , Laclette J. P. , Morales‐Montor J.
Published: June 2007

Intestinal infection with the protozoan parasite Entamoeba histolytica elicits a local immune response with rising of specific secretory IgA (sIgA) antibodies detectable in several compartments associated to mucosa. Anti‐amoebic sIgA antibodies have been reported in faeces, saliva, bile and breast milk from dysenteric patients and research trying to elucidate their role in protection has recently intensified. IgA antibodies inhibit the in vitro adherence of E. histolytica trophozoites to epithelial cell monolayers by recognizing several membrane antigens, including the galactose‐binding lectin (Gal‐lectin), main surface molecule involved in adherence, and the serine and cystein‐rich proteins, all of them potential vaccine candidates. In fact, the presence of sIgA anti‐Gal lectin in faeces of patients recovered from amoebic liver abscess (ALA) was associated with immunity to E. dispar. Moreover, the combined nasal and intraperitoneal vaccination of C3H/HeJ mice with native and recombinant Gal‐lectin protected mice against an intracecal challenge with virulent E. histolytica trophozoites, protection that seemed to be associated with the induction of specific intestinal sIgA antibodies. Therefore, the stimulation of intestinal secretory response by mucosal delivery of amoebic antigens has been positioned as a promising strategy for inducing protection against human amoebiasis.
Toxoplasma gondii infection induces apoptosis in noninfected macrophages: role of nitric oxide and other soluble factors
Authors: NISHIKAWA Y. , KAWASE O. , VIELEMEYER O. , SUZUKI H. , JOINER K. A. , XUAN X. , NAGASAWA H.
Published: June 2007

Apoptosis has been found to help in the defence against pathogens. Infection with the obligate intracellular parasite Toxoplasma gondii is known to trigger host‐cell apoptosis. When using a T. gondii‐infected macrophage cell line, J774A.1, treatment with IFN‐γ significantly enhanced apoptosis in noninfected bystander cells while parasitized cells became relatively resistant. Infection and IFN‐γ treatment activated the expression of inducible nitric oxide synthase (iNOS), and the production of nitric oxide (NO) and treatment of cells with an iNOS inhibitor, NG‐monomethlyl‐l‐arginine acetate (l‐NMMA) reduced the apoptosis frequency. However, the reversal was only partial suggesting that not only NO, but also other, as of yet, unknown factors are induced. Finally, we studied the effect in vivo by infecting mice with either a virulent or an avirulent strain. Challenge with the virulent strain lead to a higher parasite burden, induced host‐cell apoptosis in peritoneal cells, and produced higher levels of IFN‐γ and NO. Moreover, treatment of mice with a NO synthase inhibitor, aminoguanidine, partially inhibited the host‐cell apoptosis induced by the parasite infection. Altogether, our findings indicate that apoptosis in bystander host cells is due to the secretion of NO and other soluble factors released by parasite‐infected cells.
Description and applications of a rapid and sensitive non‐radioactive microplate‐based assay for maximum and initial activity of D‐ribulose‐1,5‐bisphosphate carboxylase/oxygenase
Authors: SULPICE RONAN , TSCHOEP HENDRIK , VON KORFF MARIA , BÜSSIS DIRK , USADEL BJÖRN , HÖHNE MELANIE , WITUCKA‐WALL HANNA , ALTMANN THOMAS , STITT MARK , GIBON YVES
Published: June 2007

D‐ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) catalyses the first step in photosynthetic carbon assimilation and represents the largest sink for nitrogen in plants. Improvement of its kinetic properties or the efficiency with which it is used in planta would benefit photosynthesis, nitrogen and water use efficiency, and yield. This paper presents a new non‐radioactive microplate‐based assay, which determines the product [3‐phosphoglycerate (3‐PGA)] in an enzymic cycle between glycerol‐3‐phosphate dehydrogenase and glycerol‐3‐phosphate oxidase. High sensitivity permits use of highly diluted extracts, and a short reaction time to avoid problems due to fall‐off. Throughput was several hundreds of samples per person per day. Sensitivity and convenience compared favourably with radioisotopic assays, which were previously used to assay Rubisco. Its use is illustrated in three applications. (1) Maximal and initial activities and the Km for ribulose‐1,5‐bisphosphate were determined in raw extracts of leaves from several species. Similar values were obtained from those in the literature. (2) Diurnal changes were compared in rosettes of wild‐type (WT) Arabidopsis and the starchless pgm mutant. Despite these dramatic differences in carbon metabolism, Rubisco activity and activation were similar in both genotypes. (3) A preliminary association mapping study was performed with 118 Arabidopsis accessions, using 183 markers that probably cover ∼3–8% of the total genome. At a P‐value < 0.005, two, two and no quantitative trait loci (QTL) were found for Rubisco maximal activity, initial activity and activation state, respectively. Inspection of the genomic regions that span these markers revealed these QTL involved genes not previously implicated in the regulation of Rubisco expression or activity.
The temperature response of C3and C4photosynthesis
Authors: SAGE ROWAN F. , KUBIEN DAVID S.
Published: June 2007

We review the current understanding of the temperature responses of C3and C4photosynthesis across thermal ranges that do not harm the photosynthetic apparatus. In C3species, photosynthesis is classically considered to be limited by the capacities of ribulose 1·5‐bisphosphate carboxylase/oxygenase (Rubisco), ribulose bisphosphate (RuBP) regeneration orPiregeneration. Using both theoretical and empirical evidence, we describe the temperature response of instantaneous net CO2assimilation rate (A) in terms of these limitations, and evaluate possible limitations onAat elevated temperatures arising from heat‐induced lability of Rubisco activase. In C3plants, Rubisco capacity is the predominant limitation onAacross a wide range of temperatures at low CO2(<300 µbar), while at elevated CO2, the limitation shifts toPiregeneration capacity at suboptimal temperatures, and either electron transport capacity or Rubisco activase capacity at supraoptimal temperatures. In C4plants, Rubisco capacity limitsAbelow 20 °C in chilling‐tolerant species, but the control overAat elevated temperature remains uncertain. Acclimation of C3photosynthesis to suboptimal growth temperature is commonly associated with a disproportional enhancement of thePiregeneration capacity. Above the thermal optimum, acclimation ofAto increasing growth temperature is associated with increased electron transport capacity and/or greater heat stability of Rubisco activase. In many C4species from warm habitats, acclimation to cooler growth conditions increases levels of Rubisco and C4cycle enzymes which then enhanceAbelow the thermal optimum. By contrast, few C4species adapted to cooler habitats increase Rubisco content during acclimation to reduced growth temperature; as a result,Achanges little at suboptimal temperatures. Global change is likely to cause a widespread shift in patterns of photosynthetic limitation in higher plants. Limitations in electron transport and Rubisco activase capacity should be more common in the warmer, high CO2conditions expected by the end of the century.
Quantitative trait loci associated with isolate specific and isolate nonspecific partial resistance to Phoma macdonaldii in sunflower
Authors: Darvishzadeh R. , Kiani S. Poormohammad , Dechamp‐Guillaume G. , Gentzbittel L. , Sarrafi A.
Published: June 2007

Black stem, caused by Phoma macdonaldii, is one of the most important diseases of sunflower in the world. Quantitative trait loci (QTLs) implicated in partial resistance to two single pycnidiospore isolates of P. macdonaldii (MP8 and MP10) were investigated using 99 recombinant inbred lines (RILs) from the cross between sunflower parental lines PAC2 and RHA266. The experimental design was a randomized complete block with three replications. High genetic variability and transgressive segregation were observed among RILs for partial resistance to P. macdonaldii isolates. QTL‐mapping was performed using a recently developed high‐density SSR/AFLP sunflower linkage map. A total of 10 QTLs were detected for black stem resistance. The phenotypic variance explained by each QTL (R2) was moderate, ranging from 6 to 20%. Four QTLs were common between two isolates on linkage group 5 and 15 whereas the others were specific for each isolate. Regarding isolate‐specific and isolate‐nonspecific QTLs detected for partial resistance, it is evident that both genetic effects control partial resistance to the disease isolates. This confirms the need to consider different isolates in the black stem resistance breeding programmes. The four SSR markers HA3700, SSU25, ORS1097 and ORS523_1 encompassing the QTLs for partial resistance to black stem isolates could be good candidates for marker assisted selection.
Efficient, long‐lasting resistance against the soft rot bacterium Pectobacterium carotovorum in calla lily provided by the plant activator methyl jasmonate
Authors: Luzzatto T. , Yishay M. , Lipsky A. , Ion A. , Belausov E. , Yedidia I.
Published: June 2007

The potential of three externally applied chemical plant activators, Bion, BABA and methyl jasmonate, known to act only through the plant defence system and not on the pathogen directly, to induce resistance against wild‐type Pectobacterium carotovorum was examined in white‐flowered calla lily (Zantedeschia aethiopica). Following a 24‐h induction period, plants were challenge‐inoculated with P. carotovorum, originally isolated from calla lily or potato plants, previously transformed using a gfp broad‐host‐range promoter‐probe vector. After another 24 h, Bion treatment (10 µg mL−1, as a drench) reduced disease symptoms more than sixfold and bacterial proliferation by four orders of magnitude. BABA treatment (5–10 µg mL−1, also as a drench) reduced the rate of infection by 75–85%. However, the protection afforded by both inducers did not persist. Also, at higher concentrations both displayed a phytotoxic effect. By contrast, methyl jasmonate (10 mm, applied as a leaf spray) completely inhibited P. carotovorum development in calla lily leaves and afforded a long‐lasting effect. It is suggested that the defence response of calla lily against P. carotovorum involves the SA‐signalling pathway in the short term, but the jasmonate/ethylene‐signalling pathway is required for durable protection.
Detection of lethal yellowing phytoplasma in embryos from coconut palms infected with Cape St Paul wilt disease in Ghana
Authors: Nipah J. O. , Jones P. , Dickinson M. J.
Published: June 2007

This study investigated the potential of seed transmission of Cape St. Paul wilt disease (CSPWD) in coconuts. PCR amplification was used to assess the distribution of phytoplasmas in parts of West African Tall (WAT) palms infected with CSPWD. Employing phytoplasma universal primer pair P1/P7 in standard PCR, or followed with a nested PCR using CSPWD–specific primer pair G813f/AwkaSR, phytoplasma infection was detected in the trunks, peduncles, spikelets, male and female flowers of four infected WAT coconut palms. Through nested PCR, phytoplasma was also detected in four of 19 embryo DNA samples extracted individually from fruits harvested from three of the four infected palms and was confirmed as CSPWD by cloning and sequencing. Subsequently, CSPWD phytoplasma was again detected in five of 33 embryos from nine infected palms, and in one of eight fruits from two symptomless palms. Fruits from infected palms recorded higher percentage germinations in two field nurseries (average of 71·0%) compared to fruits from healthy palms (average of 57·6%), and matured fruits that had dropped from infected palms showed the same levels of germination as those harvested directly from the palms. This indicates that infected fruits retain the ability to germinate whether harvested or dropped. No phytoplasmas were detected in any of the resulting seedlings and plantlets obtained through embryo in‐vitro culture. Therefore, although phytoplasma DNA can be detected in embryos, there is as yet no evidence that the pathogen is seed transmitted through to the seedling to cause disease in progeny palms.
Occurrence and development of Colletotrichum acutatum on symptomless blueberry bushes
Authors: Yoshida S. , Tsukiboshi T. , Shinohara H. , Koitabashi M. , Tsushima S.
Published: June 2007

The anthracnose fungus Colletotrichum acutatum was detected in symptomless blueberry bushes (Vaccinium spp.) in a Japanese blueberry field. Naturally diseased bushes and their apparently healthy neighbours were selected, and C. acutatum was isolated from the symptomless tissues of each bush from February 2000 to January 2002. Analysis of the diseased bushes during the dormant period revealed that the fungus was able to survive on symptomless tissues, such as shoot bark and bud scales. Furthermore, C. acutatum was consistently isolated from symptomless leaves and shoots of several surrounding symptomless bushes. Arbitrarily primed PCR (ap‐PCR) analyses of the fungal isolates obtained from the diseased and symptomless bushes revealed that most C. acutatum isolates were genotypically identical, regardless of their origins. Inoculation tests using leaves of various blueberry cultivars suggested that the presence or absence of symptoms on each bush can not always be explained by differences in cultivar susceptibility, and other factors may be associated with the appearance of symptoms.
Discrimination of Eubazus (Hymenoptera, Braconidae) sibling species using geometric morphometrics analysis of wing venation
Authors: VILLEMANT CLAIRE , SIMBOLOTTI GIUSEPPINA , KENIS MARC
Published: June 2007

Abstract Complexes of sibling and cryptic species are encountered frequently in parasitic Hymenoptera. Geometric morphometrics is a useful tool to detect minimal morphological variations, which often are undetectable by traditional morphological studies and even by classical morphometric approaches. We applied geometric morphometrics to wing venation to assess a complex case of sibling species in the genus Eubazus (Hymenoptera, Braconidae), parasitoids of conifer bark weevils of the genus Pissodes (Coleoptera, Curculionidae). The results and methods were compared with previous taxonomic studies on the same species, involving classical multivariate morphometrics, isoenzyme analyses, cross‐mating experiments and biological observations. Geometric morphometrics confirmed the previous division into four distinct species. However, this approach enabled the four species to be separated simultaneously, with a reliability of 98.6% for well‐classified females and 93.1% for males. A similar result in previous studies was obtained only by combining isoenzyme analyses and several canonical variate analyses, including many morphometric characters. Furthermore, measurements of wing venation were less time‐consuming, more reliable and required less prior knowledge of braconid taxonomy than the measurements needed for the classical morphometrics methods. Geometric morphometrics was used also to test the effect of host species on wing shape. Several female populations of Eubazus semirugosus originating from three different Pissodes spp. were compared. Significant differences were found in wing shape between conspecific Eubazus from different host species. The results are discussed in relation to reproductive isolation and genetic flow between the four species.
Growth mechanism of snowball garnets from the Lukmanier Pass area (Central Alps, Switzerland): a combined μCT/EPMA/EBSD study
Authors: Robyr Martin , Vonlanthen Pierre , Baumgartner Lukas P. , Grobety Bernard
Published: June 2007

For two decades, considerable efforts have been made to explain the formation of snowball garnets by either the rotational or non‐rotational models. On the basis of morphological, chemical and crystallographic evidence, this paper presents new data on snowball garnets showing that the formation of these microstructures can be explained by the combination of the two previously proposed mechanisms operating consecutively during garnet growth. The crystallization sequence of garnet revealed by Mn contouring and the distribution of crystallographic orientations within the spiral indicate that the final stages of garnet growth are controlled by post‐kinematic crystallization. However, some microstructural arguments plead for a rotational contribution during the first stages of growth. In this view, the overall spiral geometry is thought to overestimate the true amount of rotation experienced by the garnets. Results also reveal the existence of complex snowball garnets consisting of several grains formed from distinct nucleation sites.
A possible impact crater for the 1908 Tunguska Event
Authors: Gasperini L. , Alvisi F. , Biasini G. , Bonatti E. , Longo G. , Pipan M. , Ravaioli M. , Serra R.
Published: June 2007

The so‐called ‘Tunguska Event’ refers to a major explosion that occurred on 30 June 1908 in the Tunguska region of Siberia, causing the destruction of over 2000 km2 of taiga, globally detected pressure and seismic waves, and bright luminescence in the night skies of Europe and Central Asia, combined with other unusual phenomena. The ‘Tunguska Event’ may be related to the impact with the Earth of a cosmic body that exploded about 5–10 km above ground, releasing in the atmosphere 10–15 Mton of energy. Fragments of the impacting body have never been found, and its nature (comet or asteroid) is still a matter of debate. We report results from the investigation of Lake Cheko, located ∼8 km NNW of the inferred explosion epicenter. Its funnel‐like bottom morphology and the structure of its sedimentary deposits, revealed by acoustic imagery and direct sampling, all suggest that the lake fills an impact crater. Lake Cheko may have formed due to a secondary impact onto alluvial swampy ground; the size and shape of the crater may have been affected by the nature of the ground and by impact‐related melting and degassing of a permafrost layer.