Cloning and characterization of a gene encoding an immunoglobulin-binding receptor on the cell surface of some members of the family Trypanosomatidae

Several members of the Trypanosomatidae family, when freshly isolated from their mammalian hosts, have immunoglobulins adsorbed to their cell surfaces. However, a significant portion of these antibody molecules is not parasite specific, i.e., the immunoglobulins are bound to the parasite's cell surface molecules via noncognitive interactions. It has been proposed that this noncognitive adsorption of immunoglobulins to the parasite is mediated by an Fc-like receptor present in several members of the Trypanosomatidae family. However, the molecular identification of this receptor has never been defined. Here, we describe the cloning of a gene encoding a protein that might represent this molecule. The gene, named Lmsp1, was cloned by screening a Leishmania major cDNA expression library using a rabbit antiserum. Lmsp1 is present in both Leishmania and Trypanosoma and is expressed in all developmental stages of these parasites. The predicted protein has a molecular mass of 16.6 kDa and contains an RGD sequence starting at residue 104 and three cysteine residues at positions 55, 74, and 116. The purified recombinant protein strongly binds to normal immunoglobulins of various animal species (humans, rabbits, sheep, goats, guinea pigs, donkeys, rats, and mice) and the binding to human immunoglobulins appears to be immunoglobulin G (IgG) and IgM isotype specific. Moreover, Lmsp1 binds to both purified Fc and Fab fragments of IgG from both humans and rabbits. The mapping of the Lmsp1 epitopes that bind human IgG revealed that different sequences of the molecule bind to Fc or Fab. In addition, fluorescence-activated cell sorter analyses with a specific rabbit anti-Lmsp1 antiserum showed that Lmsp1 is associated with the parasite's cell surface. Finally, inhibition experiments point to an active role of this molecule in the immunoglobulin-mediated attachment and penetration of Trypanosoma cruzi in its macrophage host cells, thus suggesting that Lmsp1 is a putative Trypanosomatidae immunoglobulin receptor.     

Genetic association between the phospholipase A2 gene and unipolar affective disorder: a multicentre case-control study

The co-segregation in one pedigree of bipolar affective disorder with Darier's disease whose gene is on chromosome 12q23-q24.1, and findings from linkage and association studies with the neighbouring gene of phospholipase A2 (PLA2) indicate that PLA2 may be considered as a candidate gene for affective disorders. All relevant genetic association studies, however, were conducted on bipolar patients. In the present study, the possible association between the PLA2 gene and unipolar affective disorder was examined on 321 unipolar patients and 604 controls (all personally interviewed), recruited from six countries (Belgium, Bulgaria, Croatia, Germany, Greece, and Italy) participating in the European Collaborative Project on Affective Disorders. After controlling for population group and gender, one of the eight alleles of the investigated marker (allele 7) was found to be more frequent among unipolar patients with more than three major depressive episodes than among controls (P<0.01); genotypic association was also observed, under the dominant model of genetic transmission (P<0.02). In addition, presence of allele 7 was correlated with a higher frequency of depressive episodes (P<0.02). These findings suggest that structural variations at the PLA2 gene or the chromosomal region around it may confer susceptibility for unipolar affective disorder.     

The cellular mechanism of thalamic ponto-geniculo-occipital waves

The cellular mechanisms underlying the genesis of thalamic ponto-geniculo-occipital waves were studied in reserpinized cats under urethane anaesthesia. Simultaneous field potential and intracellular recordings were performed in the lateral geniculate nucleus after acute lesions of retinal and visual cortical inputs. In most relay cells, reserpine-induced ponto-geniculo-occipital waves were associated with a transient depolarization that was often interrupted by a unitary inhibitory postsynaptic potential. The depolarization grew in size with membrane hyperpolarization and was accompanied by an increase in membrane conductance. The inhibitory postsynaptic potential is likely to have resulted from the activation of intrageniculate interneurons since perigeniculate cells were always inhibited during the occurrence of ponto-geniculo-occipital waves. Under reserpine, thalamic ponto-geniculo-occipital waves could also be triggered by peribrachial or auditory stimulation. These evoked ponto-geniculo-occipital waves were associated with intracellular events identical to those occurring spontaneously after reserpine administration. In addition, thalamic spindle oscillations were readily blocked by the occurrence of spontaneous or evoked ponto-geniculo-occipital waves. On the basis of the present results and those already published in the literature, the conclusion is reached that lateral geniculate ponto-geniculo-occipital waves result from a nicotinic activation of relay cells and from a parallel muscarinic inhibition of perigeniculate cells by peribrachial afferents. The functional significance of the ponto-geniculo-occipital activity is discussed on the basis of the antagonistic action of these signals on thalamic oscillations. It is proposed that these signals are the central correlates of orienting reactions elicited by sensory stimuli during waking (the so-called eye movement potentials) and by internally generated drives during paradoxical sleep.     

Variety and complexity of chromosome 17 translocations in neuroblastoma

In neuroblastoma, the most frequent genetic alteration is gain of chromosome arm 17q, which arises from unbalanced translocations. To document these genetic events more precisely, we performed an extensive study of chromosome 17 breakpoints in 27 neuroblastoma cell lines by using a combination of fluorescence in situ hybridization mapping with BAC/PAC clones and allele analysis with polymorphic markers. All cases exhibited one or more unbalanced chromosome 17 translocations, and 15 distinct breakpoint regions could be mapped. This high variability indicates that gene fusion or disruption events are extremely unlikely to account for the underlying oncogenic role of these translocations. However, breakpoints were not randomly distributed, most of them mapping to the proximal part of 17q. As a result of translocations, all cell lines but one exhibited gain of the 53.5 Mb-->qter fragment, bordered proximally by the clone CTC-462L7. The most telomeric breakpoint, flanked by the clone RP11-443M10, defined the 70.9 Mb-->qter fragment as a region of additional gain. In addition to chromosome gains, loss of heterozygosity for the short arm of chromosome 17 was observed in close to half the cases. It was either related to a chromosome 17 monosomy or to a uniparental isodisomy. Finally, in cases with a single normal chromosome 17, we show that the parental origin of the translocated chromosome 17 can be either distinct or identical to that of the normal chromosome. Similarly, multiple translocations within the same cell line can either involve the same or different chromosome 17 homologues, indicating the likely absence of parental origin bias in the generation of these alterations.     

Characterization of the poliovirus 147S particle: new insights into poliovirus uncoating

A Sabin 1 strain poliovirus (PV) mutant, S1(2Y-1I), carrying a Tyr at amino acid position VP2(142) and an Ile at position VP1(160), can establish persistent infections in HEp-2c cells. This mutant forms atypical 147S particles upon interaction at 0 degrees C with either cells expressing PV receptor (PVR) CD155, or PVR-IgG2a, a chimeric molecule consisting of an extracellular moiety of PVR and the hinge and Fc portion of a mouse IgG2a. Upon interaction with PVR at 37 degrees C, S1(2Y-1I), similar to the parental strain, forms both 135S A particles and 80S empty capsids. At 0 degrees C, surprisingly, at a concentration equal to or greater than 5 nM, PVR-IgG2a induced both the extrusion of VP4 from the capsid of S1(2Y-1I) and the formation of 80S particles. The same transitions were observed at 0 degrees C with the parental strain Sabin 1 at 40 nM PVR-IgG2a. Thus, the formation of 80S particles and VP4 extrusion, considered as one of the steps of PV uncoating, can be temperature-independent at high PVR concentration. This implies that structural changes of the PV capsid occurred following adsorption at low temperature.     

Presence and characterization of extraintestinal pathogenic Escherichia coli virulence genes in F165-positive E. coli strains isolated from diseased calves and pigs

The virulence genotype profile and presence of a pathogenicity island(s) (PAI) were studied in 18 strains of F165-positive Escherichia coli originally isolated from diseased calves or piglets. On the basis of their adhesion phenotypes and genotypes, these extraintestinal pathogenic strains were classified into three groups. The F165 fimbrial complex consists of at least two serologically and genetically distinct fimbriae: F165(1) and F165(2). F165(1) is encoded by the foo operon (pap-like), and F165(2) is encoded by fot (sfa related). Strains in group 1 were foo and fot positive, strains in group 2 were foo and afa positive, and strains in group 3 were foo positive only. The strains were tested for the presence of virulence genes found mainly in extraintestinal pathogenic E. coli (ExPEC) strains. Although all the strains were positive for the papA variant encoding F11 fimbriae incD, traT, and papC, the prevalence of virulence genes commonly found in PAIs associated with ExPEC strains was highly variable, with strains of group 2 harboring most of the virulence genes tested. papG allele III was detected in all strains in group 1 and in one strain in group 3. All other strains were negative for the known alleles encoding PapG adhesins. The association of virulence genes with tRNA genes was characterized in these strains by using pulsed-field gel electrophoresis and DNA hybridization. The insertion site of the foo operon was found at the pheU tRNA locus in 16 of the 18 strains and at the selC tRNA locus in the other 2 strains. Furthermore, 8 of the 18 strains harbored a high-pathogenicity island which was inserted in either the asnT or the asnV/U tRNA locus. These results suggest the presence of one or more PAIs in septicemic strains from animals and the association of the foo operon with at least one of these islands. F165-positive strains share certain virulence traits with ExPEC, and most of them are pathogenic in piglets, as tested in experimental infections.     

Specificities and functions of the recA and pps1 intein genes of Mycobacterium tuberculosis and application for diagnosis of tuberculosis

The worldwide recrudescence of tuberculosis and the widespread appearance of antibiotic resistance have strengthened the need for rapid and specific diagnostic tools. The prevailing microbiological identification of Mycobacterium tuberculosis, the causative agent of tuberculosis, which implies the use of in vitro cultures and acid-fast staining microscopy, is time-consuming. Detection of M. tuberculosis directly in clinical samples through PCR amplification of mycobacterium-specific genes, designed to shorten diagnostic delay, demonstrated reliability and high sensitivity. However, the quality of the diagnosis depends on the specificity of the target sequence for M. tuberculosis complex strains. In the present study, we demonstrated the specificity of recA and pps1 inteins for this complex and thus the feasibility of using intein-coding sequences as a new target for PCR diagnosis. Indeed, the recA and pps1 genes of 36 clinical isolates of M. tuberculosis and 10 field strains of M. bovis were found to be interrupted by an intein sequence at the RecA-a and Pps1-b sites, respectively, while a large number of nontuberculous mycobacterial species failed to demonstrate these insertions. Besides, the MtuPps1, which was cloned and expressed in Escherichia coli, was shown to possess an endonuclease activity. The intein cleaves the 40-bp sequence spanning the intein insertion site Pps1-b in the inteinless pps1 gene. In addition to the PCR amplification of recA and pps1 intein genes as a tool for diagnosis, the specific endonuclease activity could represent a new molecular approach to identify M. tuberculosis.     

Bilateral cataract and high serum ferritin: a new dominant genetic disorder?

This paper reports the cosegregation in a three generation pedigree of dominantly inherited cataract with an abnormally high level of serum ferritin. In this family, circulating L ferritin was raised in all subjects affected by cataract independently of iron overload. We suggest that a disorder of ferritin metabolism could be a new genetic disorder leading to lens opacity. Cataract-hyperferritaemia syndrome could also be a new contiguous gene syndrome involving the L ferritin gene and the gene coding for the lens membrane protein (MP19), which both map to the same region of chromosome 19q.     

Hydroxytelechelic polybutadiene, 12. Polymerization reactions between hydroxytelechelic polybutadiene with hexamethylene diisocyanate or 4,4′-methylenedi(phenyl isocyanate). Kinetics of polymerization in toluene and in the bulk

Addition polymerization of hydroxytelechelic polybutadiene (HTPB) with hexamethylene diisocyanate (HMDI) with a mole ratio NCO/OH = 0,8 in dilute solution of toluene as well as in bulk follows apparent 3rd order kinetics. The polymerization rates are twice as sensitive to temperature as in toluene, an effect which is attributed to intra- and/or intermolecular (OH, OH) auto-association. The three alcoholic functions in HTPB are catalyzed equally by dibutyltin dilaurate. Even with high excess of NCO, free alcoholic functions were found in the product. They were determined quantitatively in moulded polyurethane sheets from HTPB + HMDI and HTPB + 4,4′-methylenedi(phenyl isocyanate) which should be partially crosslinked: