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Publications and source records attributed to P Leblond.
We report a case of neuroblastoma diagnosed after adrenal haemorrhage following a minor trauma in a thirteen-month-old boy. Minor trauma is not commonly described as a cause of AH in the literature. Therefore when no accepted cause for AH can be found in a young child below the age of 5 years, it is important to look for a neuroblastoma and discuss the necessity of surgical exploration.
BACKGROUND: Acute pyelonephritis can induce parenchymal scarring. The aim of this study was to evaluate the usefulness of procalcitonin (PCT) to predict renal involvement in febrile children with urinary tract infection (UTI). METHODS: In a prospective study serum PCT was measured and compared with others commonly used inflammatory markers in children admitted to the emergency unit with acute pyelonephritis. Renal parenchymal involvement was assessed by a (99 m)Tc-labeled dimercaptosuccinic acid (DMSA) renal scar performed in the first 3 days after the admission. RESULTS: Among 42 enrolled patients, 19 (45%) had acute renal involvement (Group A) ; 23 (55%) (Group B) had normal DMSA scan (n = 16), or old scarring (n = 4) or various anomalies related to uropathy (n = 3). In group A, the mean PCT level was significantly higher than in the group B (5.4 ng/ml, vs 0.4 ng /ml, p < 10(-5)). In these 2 groups, mean C reactive protein (CRP) levels were 99.1 mg/l and 44.6 mg/l respectively (p < 0.001). For a level of serum PCT > or = 0.5 ng/ml, the sensitivity and specificity to predict the renal involvement were 100% and 87% respectively; for a level> or= 20 mg/l CRP had a sensitivity of 94% but a specificity of 30%. CONCLUSION: Serum PCT levels were significantly increased in febrile children with UTI when acute renal parenchymal involvement was present. PCT seems a better marker than CRP for the prediction of patients at risk of renal lesions.
UNLABELLED: We report a case of idiopathic hypereosinophilic syndrome in a young child with favorable outcome after treatment with alpha-interferon. CASE REPORT: A 5-month-old boy presented with major eosinophilia (187 G/l) associated with splenomegaly. There was no evidence for parasitic or allergic disease. Acute leukemia was suspected but bone marrow smear and medullary caryotype were not compatible. Idiopathic hypereosinophilic syndrome was thus diagnosed. Corticotherapy was started and failed. Finally, complete remission was obtained with alpha-interferon treatment. CONCLUSION: Idiopathic hypereosinophilic syndrome is uncommon in children. Significant complications like cardiac dysfunction or hematologic malignancies can occur. Treatment has to be quickly started, in order to reduce eosinophilia. Haematological and echocardiographic follow-up are required.
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In Streptomyces, a genomic instability results from frequent recombination events which occur at the ends of the linear chromosomal DNA. These events are believed to be responsible for the variability observed in these regions among Streptomyces species and strains. In order to identify functions able to control this type of genome plasticity, mutators as well as mutants produced at different stages of development have been characterized in S. ambofaciens. Their characterization suggests the existence of a relationship between genomic instability and colony development.
In Streptomyces ambofaciens a genetic instability generates a high degree of polymorphism consisting of four main phenotypes: pigmented colonies (Pig(+) qualified as WT phenotype), pigment-defective colonies, pigmented colonies with pigment-defective sector and pigmented colonies with pigment-defective papillae. Molecular analysis of Pig(col)(-) and Pig(sec)(-) (pigment-defective mutant derived from a colony and a sector, respectively) produced by genetic instability and isolated in five Pig(+) subclones progenies revealed a new aspect of polymorphism in S. ambofaciens ATCC23877. Frequencies of Pig(col)(-) and Pig(sec)(-) mutants deleted at the chromosome ends varied from one WT progeny to another. Two main types of deleted mutants were observed: deleted for one or both chromosomal extremities. The relative proportion of these two categories differed according to the WT progeny. These results argue for heterogeneity of the WT clones, i.e., Pig(+) colonies, originated from S. ambofaciens ATCC23877.
Genome rearrangements are responsible for the variability observed at the ends of the chromosome among Streptomyces species. The characterization of mutators, which are stimulated for genome plasticity, and of mutants produced at different stages of development support the idea that genome instability is developmentally modulated.
Streptomyces ambofaciens is prone to genetic instability involving genomic rearrangements at the extremities of the chromosomal DNA. An amplified DNA sequence (ADS205), including an open reading frame (orfPS), is responsible for the reversible loss of spiramycin production in the mutant strain NSA205 (ADS205(+) Spi-). The product of orfPS is homologous to polyketide synthase systems (PKSs) involved in the biosynthesis of erythromycin and rapamycin and is overexpressed in strain NSA205 compared with the parental strain RP181110. As PKSs and fatty acid synthase systems have the same precursors, we tested the possibility that overexpression of orfPS also affects lipid metabolism in strain NSA205. This report focuses on comparative analysis of lipids in strain RP181110, the mutant strain NSA205, and a derivative, NSA228 (ADS205(-) Spi+). NSA205 showed a dramatically depressed lipid content consisting predominantly of phospholipids and triacylglycerols. This lipid content was globally restored in strain NSA228, which had lost ADS205. Furthermore, strains RP181110 and NSA205 presented similar phospholipid and triacylglycerol compositions. No abnormal fatty acids were detected in NSA205.
The chromosomal DNA of the bacteria Streptomyces ambofaciens DSM40697 is an 8-Mb linear molecule that ends in terminal inverted repeats (TIRs) of 210 kb. The sequences of the TIRs are highly variable between the different linear replicons of Streptomyces (plasmids or chromosomes). Two spontaneous mutant strains harboring TIRs of 480 and 850 kb were isolated. The TIR polymorphism seen is a result of the deletion of one chromosomal end and its replacement by 480 or 850 kb of sequence identical to the end of the undeleted chromosomal arm. Analysis of the wild-type sequences involved in these rearrangements revealed that a recombination event took place between the two copies of a duplicated DNA sequence. Each copy was mapped to one chromosomal arm, outside of the TIR, and encoded a putative alternative sigma factor. The two ORFs, designated hasR and hasL, were found to be 99% similar at the nucleotide level. The sequence of the chimeric regions generated by the recombination showed that the chromosomal structure of the mutant strains resulted from homologous recombination events between the two copies. We suggest that this mechanism of chromosomal arm replacement contributes to the rapid evolutionary diversification of the sequences of the TIR in Streptomyces.
Pulsed-field gel electrophoresis (PFGE) proved to be a powerful approach to study bacterial genomics. The genome structure and genetic polymorphism of Gram-positive bacteria from the high G+C (Streptomyces) and low G+C (Streptococcus) groups have been studied. PFGE allowed the estimation of the size of their genome at about 8 Mbp and 1.8 Mbp, respectively, and to get an insight into their chromosome geometry. Thus, physical mapping of the genome of wild-type Streptomyces ambofaciens strains revealed the linearity of the 8 Mbp chromosomal DNA and its typical invertron structure, while the 1.8 Mbp chromosome of Streptococcus thermophilus was shown to be circular. These findings disproved the long-standing idea of universality of bacterial chromosome circularity. In addition, strains belonging to the species S. ambofaciens and S. thermophilus allowed us to characterize the genetic polymorphism at the intraspecific level. Within the S. thermophilus species, comparison of the physical maps showed a relative conservation of gene order as well as restriction sites along the chromosome. In contrast, variable loci were characterized that revealed localized genome rearrangements. The most spectacular of these corresponded to horizontal gene transfer events of sequences. In S. ambofaciens, the physical maps of three isolates pointed to the conservation of the genetic organization. However, a strong polymorphism was observed in the terminal regions of the linear chromosomal DNA. Previous PFGE studies in S. ambofaciens gave proof of a high structural instability of a limited region of the chromosome called unstable region (i.e., DNA rearrangements such as deletions and amplifications). These intraclonal rearrangements create an impressive intraspecific polymorphism of genome size and shape (linear or circular). In both organisms, the DNA rearrangements are restricted to particular regions of the chromosome.
From a cosmid clone of Streptomyces ambofaciens containing the dnaA and gyrAB genes, a 2.7-kb self-replicating DNA fragment containing the chromosome replication origin oriC was isolated. This cosmid was previously maped physically to a region near the middle of the 8-Mb linear chromosomal DNA. A pulsed-field gel electrophoresis time-course analysis revealed that sequences flanking oriC were overrepresented relative to the rest of the chromosomal DNA during rapid growth, indicating that this origin is active. In addition, the terminal regions of the chromosomal DNA showed a slight overrepresentation at the onset of stationary phase.
The recA gene was isolated from Streptomyces ambofaciens DSM40697. Its nucleotide sequence predicted a protein of 372 residues. Two recA mutants, NSAR1001 and NSAR57, obtained by gene disruption encoded a RecA protein lacking respectively 30 and at least 62 amino acids from the C-terminal end. NSAR1001 showed a wild-type sensitivity to UV light and oxolinic acid. In contrast, NSAR57 was highly sensitive to these agents and the loss of the inserted DNA restored the wild-type phenotype. Western blot analysis using antiserum to Escherichia coli RecA showed that overproduction of RecA was correlated with overtranscription of recA in an S. ambofaciens amplified mutant derived from genetic instability.
Recent progress in the understanding of the chromosomal rearrangements in Streptomyces has allowed us to envisage the possible involvement of genetic instability in the evolution of the chromosomal structure. The characterization of recombinational events in the terminal parts of the S ambofaciens chromosome, as well as the observation by other groups that linear plasmids and chromosomes are able to interact, would provide an explanation for the very high levels of polymorphism seen in the terminal inverted repeats of different strains of Streptomyces.
The chromosomal structures of mutant strains of Streptomyces ambofaciens which have arisen from genetic instability were investigated by using pulsed-field gel electrophoresis and probing with sequences cloned from the unstable region which maps near the ends of the linear chromosomal DNA. The chromosomal structures of seven mutant strains harboring large deletions were classified into three types. (i) Deletions internal to one chromosomal arm were characterized in two of the mutant strains. In these strains, a linear chromosomal structure was retained, as were parts of the terminal inverted repeats sequences (TIRs) and the proteins bound to them. (ii) Four of the mutants presented a deletion including all sequences from the TIRs. A junction fragment homologous to sequences originating from internal region of both arms was characterized. Consequently, the chromosomal DNA of these strains was deduced to be circularized. Furthermore, chromosomal stability was assessed in the progeny of these circular DNA mutants. Additional deletion events were detected in 11 mutants among the 13 strains isolated, demonstrating that circular chromosomes do not correspond to a stabilization of the chromosome structure and that the occurrence of deletion could be independent of the presence of chromosomal ends. (iii) A mutant with DNA amplification was shown to have a linear chromosome with a deletion of all sequences between the amplified region and the end of the chromosome. The other chromosomal arm remained unaffected by deletion and associated with protein.
Streptomyces ambofaciens DSM40697 possess six rRNA gene clusters which can be distinguished by probing BfrI-digested total DNA with the PCR-amplified l6S-23S ribosomal genet internal transcribed spacer. The six rrn loci of S. ambofaciens were cloned as recombinant cosmids and located on the AseI-Dŕal physical map of the linear chromosomal DNA. For five of the six ribosomal gene sets, the transcriptional orientation was determined relative to the physical map and was shown to be divergent away from an oriC-like locus.
Physical maps of the chromosomes of three strains of Streptomyces ambofaciens were constructed by ordering Asel fragments generated from the genomic DNA as a single linear chromosome of about 8 Mb. The physical maps of the three strains were very similar. For strain DSM40697, a Dral map was obtained by positioning the Dral sites relative to the Asel map. Eighteen genetic markers as well as the deletable and amplifiable region were assigned to the Asel and Dral fragments in this strain. The resulting genetic map resembled that of Streptomyces coelicolor A3(2). The two terminal Asel fragments exhibited retarded pulsed-field gel electrophoresis mobility, demonstrating that proteins are covalently bound at this position. A restriction map of this region was made using four additional endonucleases. Repeated sequences present at both ends of the chromosome were mapped as long terminal inverted repeats stretching over 210 kb. This corresponds to the longest terminal inverted repeats so far characterized. The deletable region of S. ambofaciens was localized at the chromosomal extremities.
The high level of genetic instability in Streptomyces ambofaciens is related to large scale DNA rearrangements (deletions and DNA amplifications) which occur within a 2 Mb chromosomal region. The genome of several Streptomyces species is linear and the unstable region is present at the chromosomal extremities. This has raised the questions of the role of the unstable region (which is dispensable under laboratory conditions), the functions of the genes present in this area, and the relationships between instability and chromosomal linearity. The unstable region of Streptomyces and the replication termini of several other microorganisms, including Escherichia coli, share numerous common traits. This suggests that the unstable region of Streptomyces includes the replication terminus, and that chromosomal instability is related to the termination process.
Genetic instability in Streptomyces species often involves large deletions sometimes accompanied by DNA amplification. Two such systems in Streptomyces lividans 66 involve the production of mutants sensitive to chloramphenicol and the production of mutants resistant to the galactose analogue 2-deoxygalactose, respectively. Overlapping cosmids were isolated that span the ca. 1 Mb region between the two amplifiable regions. The structure of the region was confirmed by restriction mapping using the rarely cutting enzymes AseI, BfrI and DraI and pulsed-field gel electrophoresis. The region contains a non-clonable gap flanked by inverted repeats; the structure is consistent with the presence of a physical gap, i.e. a linear chromosome.