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B Pichon

Publications and source records attributed to B Pichon.

At least 19 recordsLinked to original sources
PubMed2006

Pathogens and host DNA in Ixodes ricinus nymphal ticks from a German forest.

Unfed nymphs of Ixodes ricinus were collected from vegetation in a forest on the outskirts of Berlin, Germany and were analyzed for host and pathogen DNA. Pathogens were detected in 47% of the ticks. Borrelia afzelii was the commonest pathogen detected, followed by Rickettsia helvetica. Other pathogens included B. valaisiana, B. garinii, B. burgdorferi sensu stricto, Anaplasma phagocytophilum, and a relapsing fever-like Borrelia. Most of the host DNA detected was of rodent origin and was associated with infection by B. afzelii, R. helvetica, and A. phagocytophilum. Bird DNA was associated with B. valaisiana and B. garinii, and ruminant DNA with A. phagocytophilum. B. afzelii was also found in two ticks that contained bird DNA.

Anaplasma phagocytophilum↗
PubMed2006

A bioinformatics pipeline for high-throughput microbial multilocus sequence typing (MLST) analyses.

Multilocus sequence typing (MLST) analysis for semi-routine applications is hindered by the downstream, manually intensive steps of processing the raw sequence data files. This report describes the development of an MLST pipeline that automates DNA sequence editing and analysis in order to significantly reduce the time required for processing data. Validation using a pneumococcal dataset revealed complete agreement between the results generated by manual and automated workflows. The MLST pipeline was developed for both double-strand and single-strand sequencing.

Bacteria↗
PubMed2005

Hosts and pathogen detection for immature stages of Ixodes ricinus (Acari: Ixodidae) in North-Central Spain.

To determine hosts of the immature stages of a southern population of Ixodes ricinus, we trapped rodents and birds in an area of north-central Spain in May-June and August-September of 1998 and 1999. The most frequently trapped rodents were Apodemus sylvaticus (230 specimens) and Clethrionomys glareolus (99), with a larval infestation prevalence of 49% and 81%, respectively (in spring) and 21% and 41% (in summer). C. glareolus was always more heavily parasitized by larvae (mean numbers 19.8 in spring, 3.4 in summer) than A. sylvaticus (6.1 and 1.2, respectively). No nymphs were collected from the rodents. The larval distribution pattern differed considerably between rodent host species but not according to the season of the year. The most commonly trapped birds were members of the Turdidae, which had infestation incidences of about 70% (larvae) and 10% (nymphs) in spring and 20-15% in summer. We also used molecular methods for the identification of reservoir hosts of the larval ticks and of the pathogens they contained, from nymphs collected in the same site in June of 2002 and 2003. The study showed that most of the ticks had fed on birds and few on rodents and ruminants. Pathogens detected in these ticks included Babesia microti, Borrelia garinii, B. valaisiana and B. afzelii. Borrelia afzelii was detected in a tick that had apparently fed on a wild boar.

Animals↗
PubMed2000

A method for the large-scale cloning of nuclear proteins and nuclear targeting sequences on a functional basis.

We describe here a selection strategy allowing the cloning of sequences that contain a functional nuclear targeting signal. Our method relies on the use of green fluorescent protein fusion proteins to identify nuclear targeting sequences. Transfected cells expressing nuclear protein fusions were isolated on the basis of their nuclear fluorescence using flow cytometry and the transfected DNAs were recovered after bacterial transformation with total DNA from pools of sorted cells. Starting from a cDNA expression library, in which only 1% of the expressed proteins were nuclear, we obtained a 70-fold enrichment in nuclear protein-encoding clones after a single round of selection. Among the 63 clones that have been partially sequenced to date, 25 (40%) corresponded to known nuclear proteins and 13 (20%) to previously uncharacterized sequences. Despite their ability to target the green fluorescent protein marker to the cell nucleus, about half of the cloned sequences did not encode canonical basic or bipartite nuclear localization signals. The method can thus be applied to the large-scale cloning of functional nuclear targeting sequences, which opens the way to a wide investigation of nuclear import mechanisms and to the identification of previously unknown nuclear proteins.

Animals↗
PubMed2000

Tropism of AAV-2 vectors for neurons of the globus pallidus.

A recombinant AAV-2 vector encoding the green fluorescent protein (gfp) under the control of the cytomegalovirus (CMV) promoter was injected into the striatum at varying antero-posterior coordinates. When the virus was delivered to the anterior part of the striatum, transduction efficiency was low and limited to the vicinity of the needle tract. In contrast, after injection into the posterior part of the striatum, in addition to a localized transduced area in the striatum, efficient and widespread transduction was observed at distance from the injection site, in the globus pallidus. In the latter case, labelled cells were also detected in the internal capsule and in the stria terminalis. The number of transduced cells in the striatum increased up to I month and then decreased whereas in the globus pallidus, transduction was maximal as early as 2 weeks post-injection. In the striatum and in the globus pallidus, the labelled cells had a neuron-like morphology. In contrast, in the internal capsule, labelled cells had a glial-like morphology.

Animals↗
PubMed2000

Nuclear targeting of proteins: how many different signals?

The nuclear import of proteins into the cell nucleus involves the recognition of a nuclear localization signal sequence, borne by the protein to be transported, by complex molecules called importins, that will subsequently mediate the crossing over of the nuclear envelope. The most frequently encountered signal sequence is made up of short stretches of basic amino acid residues and is recognized by importins alpha and/or beta. Other signal sequences have been described, and some have been shown to mediate the association with importins other than importin alpha or beta. Recently, approaches have been developed that allow the cloning, on a functional basis, of sequences able to specify the nuclear localization of proteins. A variety of peptidic motifs of limited size which do not contain previously described signal sequences were isolated in such assays. It reveals that the spectrum of sequences that are able to target a protein to the cell nucleus may be wider than currently expected. It will probably also lead to the identification of novel target sequences for importins and will demonstrate the implication of additional members of this family of proteins in nuclear transport.

Amino Acid Sequence↗
PubMed2000

Detection of spirochaetes of Borrelia burgdorferi complexe in the skin of cervids by PCR and culture.

To determine whether deer may play a role in the cycle of the Lyme disease spirochete Borrelia burgdorferi, we sought evidence for the presence of the pathogen in skin of deer and roe deer. Biopsies of 2 mm3 were taken at four different levels from nail to tarsus. A total of 50 animals (200 biopsies) were shot in the Lyme disease foci of Rambouillet during the hunting season 1995-1996 and 1996-1997, from the beginning of November to the end of February. Borrelia burgdorferi s.l. DNA was detected by PCR in 18 biopsies from 14 animals (28%). Borrelia burgdorferi s.str. was predominant (50%), followed by B. garinii (30%) and B. afzelii (10%). Multiple infections were detected in four animals: same species at different levels or two different species from the same biopsy or from different biopsies from the same foot. A total of 125 biopsies were cultivated on BSKH medium. Cultures at 160 days revealed immobile spiralled forms in 10 cultures. One, from a deer killed at the end of December, was confirmed by PCR as B. burgdorferi s.str. These results, frequency of detection of spirochetes by PCR in the skin, multiple infections and alive spirochetes in biopsies taken out side the season of activity of ticks strongly suggest an affinity of Lyme disease spirochetes for skin of cervids.

Animals↗
PubMed2000

Methodology for sampling questing nymphs of Ixodes ricinus (Acari: Ixodidae), the principal vector of Lyme disease in Europe.

To assess the Lyme borreliosis vector population density we set up a methodology for sampling the Ixodes ricinus L. population host questing on the vegetation. We focused on the collection of the nymphal stage, which is the principal stage of disease transmission to humans. This study was carried out in Rambouillet forest (Yvelines, France) where seven study areas were demarcated. These areas are maximally homogeneous for plant species using a finer scale than the phytosociological classification as defined by the method of landscape diagnostics. Out of 23 collections performed from March 1997 to May 1998, 2,906 I. ricinus nymphs were collected. The sampling technique chosen was the cloth lure technique. The technical parameters were studied and fixed (cloth type, cloth size, sample size, researcher position). It appeared that toweling was the best cloth type to optimize the number of ticks collected; the position of the researcher had no effect on tick samples. To satisfy the criteria for correct sampling, we studied representativity, randomness, and nonselectivity of our methodology. The spatial distribution of nymphs in a homogeneous area was close to random and thus very few subsamples were needed to obtain a relative density which was representative. No significant differences were found between random samples and following transect samples; and nonselectivity was totally satisfied because we only worked on questing nymphs. We grouped the samples that presented no significant differences to attribute a density index, which varied from 0 to 5. This methodology, applied with the same parameters, offers potential for producing comparable results from studies in different geographical areas and at different times of the years.

Animals↗
PubMed1999

Critical residues of the homeodomain involved in contacting DNA bases also specify the nuclear accumulation of thyroid transcription factor-1.

The N-terminal end of thyroid transcription factor-1 (TTF-1) homeodomain is composed of a stretch of five basic amino-acids that is conserved in both POU- and NK2-class homeodomains and constitutes a functional nuclear localization signal. By analyzing the cellular distribution of fusion proteins, composed of a jellyfish green fluorescent variant and different parts of TTF-1, we show here that the presence of this basic sequence is not sufficient by itself to confer complete nuclear accumulation. By mutagenesis, we identified a second region located in the center of the DNA recognition helix of the homeodomain that is also able to specify a predominantly nuclear localization of the chimeric proteins, independently of the presence of the basic NLS. The destruction, by mutagenesis, of both the basic stretch and the motif in the DNA recognition helix led to the total loss of nuclear accumulation, indicating that complete nuclear accumulation of TTF-1 results from the concerted action of these two proteic signals. Both of the regions of the homeodomain that are involved in nuclear targeting also encompass critical amino-acids responsible for DNA binding site recognition, as evidenced by the loss of DNA binding activity in vitro upon mutagenesis. Specifically, residues in the central part of the DNA recognition helix are involved in contacting bases in the major groove of DNA and are the most conserved in homeodomain proteins, suggesting that this part of the homeodomain could play a general role in the nuclear localization of members of this family of proteins.

Animals↗
PubMed1999

A canonical nerve growth factor-induced gene-B response element appears not to be involved in the cyclic adenosine monophosphate-dependent expression of differentiation in thyrocytes.

The expression of transcriptionally active nerve growth factor-induced gene-B (NGFI-B) is rapidly induced in thyroid follicular cells in response to cAMP stimulation. As the transcription of thyrocyte-specific genes is controlled by the cAMP cascade, we have investigated a possible involvement of NGFI-B in this control. Recombinant adenoviruses driving the expression of either the intact NGFI-B protein or a truncated form of it that lacks the capacity to transactivate a NBRE-dependent promoter, were used to infect dog thyrocytes maintained in primary culture. Northern blot analysis of total RNA from infected cells revealed that the expression of NGFI-B was not sufficient to induce a significant accumulation of specific transcripts (thyroglobulin, thyroperoxidase, sodium-iodide symporter) in unstimulated thyrocytes. The overproduction of the transcriptionally inactive form of NGFI-B in thyrocytes maintained in the presence of forskolin after infection did not impair the accumulation of the thyroid-specific transcripts. These data show that NGFI-B does not control the expression of differentiation in thyrocytes by acting through a canonical NBRE. As a consequence, we must consider that either the expression of NGFI-B in cAMP-stimulated thyrocytes is not critically linked to the expression of differentiation or that NGFI-B is implicated in a regulatory mechanism which differs from its known action at the level of a NBRE.

Adenoviridae↗
PubMed1999

Protein kinase activity in Helicobacter pylori.

Based on the predictive analysis of the cellular protein content from the complete genome sequence of Helicobacter pylori, discrepant results were previously reported concerning the occurrence of a protein kinase in this bacterium. To solve this ambiguity, we have directly assayed cellular extracts for their capacity of phosphorylating endogenous proteins. At least eight different proteins, ranging from 24 to 200 kDa, were found to be phosphorylated to a varying extent. Individual measurement of their phosphoamino acid composition showed that they all were modified at serine residues. These data indicate that H. pylori does contain a protein-serine kinase activity.

Adenosine Triphosphate↗
PubMed1999

Density of deer in relation to the prevalence of Borrelia burgdorferi s.l. in Ixodes ricinus nymphs in Rambouillet forest, France.

The Rambouillet Forest, a Lyme disease-endemic area near Paris, France, was surveyed from September 1994 to October 1995 to determine the risk periods and zones for humans. Firstly, during the period of Ixodes ricinus activity, abundance of nymphs is greater in spring than in autumn. Secondly, we observed significant variation in nymphal abundance between zones according to the density of cervids. The polymerase chain reaction (PCR) was used to detect DNA of Borrelia burgdorferi sensu lato in 461 unfed nymphs. DNA was detected in 38 nymphs (8.2%). By genospecific PCR based on the OspA gene, we detected the three pathogenic spirochetes with occurrences of 10.3, 31.1 and 58.6 for B. burgdorferi s.s., Borrelia garinii and Borrelia afzelii, respectively, indicating that B. afzelii is probably the main Borrelia species in the Rambouillet Forest. Finally, 11.5% of positive nymphs exhibited a double infection. Infection rates of I. ricinus nymphs by B. burgdorferi s.l. were not significantly different throughout the year for a given area, indicating that the risk periods of acquiring Lyme disease are mainly linked to nymph activity and correspond to spring and autumn. Likewise infection rates of nymphs were not significantly different between zones with a high density of deer (more than 100 animals per 100 ha) and zones with lower deer density (less than 20 animals per 100 ha). In addition to the role of deer as an amplifier of tick populations, these data indicate that zones with a high density of cervids should be considered as higher risk areas.

Animals↗
PubMed1998

Activation by thyroid stimulating hormone of nerve growth factor-induced gene-B expression in thyrocytes in culture: relation with proliferation and specific gene expression.

Nerve growth factor-induced gene-B (NGFI-B) is an immediate early gene first found as a part of the PC12 cell response to NGF (Milbrandt, J., Science 238 (1987) 797-799). We have previously reported that NGFI-B mRNA is strongly upregulated by thyroid-stimulating hormone (TSH) in dog thyrocytes in culture (Pichon et al., Endocrinology 137 (1996) 4691-4698). In this study, we have analyzed the regulation of NGFI-B mRNA expression by a variety of agents acting on thyrocytes proliferation and/or differentiation. We show that: (1) the induction of NGFI-B mRNA is stronger after stimulation of the cAMP cascade, but it is not restricted to this signaling pathway; (2) the powerful mitogens for thyroid cells EGF and HGF have little or no effect on NGFI-B mRNA induction; (3) NGFI-B mRNA is induced by anisomycin at a subinhibitory concentration for protein synthesis, and is superinduced by the combination of TSH and anisomycin; this treatment decreases the TSH-induced proliferation levels, but does not inhibit the induction of some differentiation markers; and (4) both in dog and in pig thyrocytes, NGFI-B mRNA induction is observed after a variety of treatments stimulating differentiation, but without proliferative effects. Our results therefore suggest that NGFI-B mRNA induction might not be related to TSH-induced thyrocyte proliferation, but could participate in the differentiation program triggered by TSH.

Animals↗
PubMed1998

TTF-2 does not appear to be a key mediator of the effect of cyclic AMP on thyroglobulin gene transcription in primary cultured dog thyrocytes.

TTF-2 is a thyroid-specific winged-helix transcription factor which has been proposed to play a key role in the hormonal control of thyroglobulin and thyroperoxidase genes transcription in FRTL-5 cells. We have analyzed TTF-2 DNA-binding activity in primary cultures of dog thyrocytes maintained in control condition or in the presence of the cAMP agonist forskolin. Binding of 35S-labelled nuclear proteins to the TTF-2 recognition sequence identified the presence of two molecular species of 41.5 and 42.5 kDa. TTF-2 DNA-binding activity was clearly detectable in nuclear extracts from unstimulated cells and appeared increased in forskolin-treated cells. Thus, the presence of TTF-2 DNA-binding activity does not correlate with the cAMP-dependent activity of thyroglobulin and thyroperoxidase genes in this cell system. In addition, the mutation of the TTF-2 binding site in the thyroglobulin promoter resulted in a very reduced but still clearly cAMP-dependent promoter activity when assayed by transient expression in the same cells. These results do not support a dominant role for TTF-2 in the cAMP-dependent control of thyroglobulin gene transcription in primary cultured thyrocytes.

Animals↗
PubMed1998

[Lyme borreliosis, emergent disease linked with the environment].

After a short historical presentation of the discovery of the pathogen and its vector, the authors present the current data on bacterial and acarologic taxonomy. Then they describe their results to assess the mechanisms of circulation of the bacteria in the forests of Ile-de-France, particularly in the forest of Rambouillet. The combined study of abundance and infection frequency of the vectors, small mammals and cervids leads to the characterization of periods and areas of higher risk. The risk periods correlate with high density of I. ricinus nymphs. The risk areas correspond to those of high density of cervids. The role of reservoir of small mammals is confirmed, to the one of large mammals, so debated, is clearly demonstrated.

Environmental Health↗
PubMed1996

Expression of a transactivation-deficient form of thyroid transcription factor I decreases the activity of co-transfected thyroglobulin and thyroperoxidase promoters.

Thyroid transcription factor I (TTF-1) plays a critical role in thyroid organogenesis and in the control of expression of several thyroid-specific genes, like those coding for thyroglobulin and thyroperoxidase. We have expressed the isolated DNA-binding homeodomain of TTF-1 in cultured thyroid cells by transient transfection. A specific reduction in the activity of co-transfected thyroglobulin and thyroperoxidase promoters was observed in the presence of the isolated TTF-1 homeodomain, as compared to their activity measured in the presence of a mutated homeodomain unable to bind DNA. The activity of the SV40 early promoter, used as a control, was only marginally affected in these experiments. The transactivation-deficient form of TTF-1 described here may thus be used for investigating other cellular processes that are dependent on TTF-1 transcriptional activity.

Cell Line↗
PubMed1996

Effect of chronic cold exposure on Na-dependent D-glucose transport along small intestine in ducklings.

In conditions of chronic cold exposure, ducklings develop a nonshivering thermogenesis that requires a high energy expenditure. Therefore, energy supply becomes essential to cold-acclimated ducklings, which increase their intake of carbohydrate-rich food. The aim of this work was to investigate the effect of cold acclimation on the activity of the intestinal brush-border Na(+)-D-glucose cotransport, which is the first major step controlling glucose entrance into an organism. Cotransport activity was determined by measuring D-glucose uptake in brush-border membrane vesicles isolated from different parts of the small intestine of thermoneutral control (25 degrees C) or cold-acclimated (4 degrees C) ducklings (Cairina moschata). Two D-glucose transport sites were described in ducklings: a high-affinity/low-capacity site and a low-affinity/high-capacity site. The former was mainly located in the ileum and the latter in the duodenum. These two transport sites were altered differently by cold exposure. Major alterations occur in the ileum where 1) a reduction in the Michaelis-Menten constant and maximal transport rate of the high-affinity site was observed, and 2) the occurrence of low-affinity site activity was noted in cold-acclimated ducklings, although it was not detected in the thermoneutral control group. Cold effect on the high-affinity site could be related to the changes in the ileal brush-border membrane vesicle lipids, whereas cold effect on the low-affinity site could be due, at least in part, to the higher glycosyl content found in this segment. The small intestine appears then able to react to cold exposure by increasing both its mucosa mass in proximal segments and D-glucose uptake capacity in ileum to respond to the higher energy demand induced by thermoregulatory requirements.

Acclimatization↗