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Biomedical subjects

G Riba

Publications and source records attributed to G Riba.

12 recordsLinked to original sources

Genetically modified plants: the stakes.

Generically modified plants (GMP) are massively used on the American continent in Australia and in China, since they represent an unquestionable potential for progress. New attributes are therefore devoted to the human and animal diet, to the facilitating of culture management, to the reducing of the chemical fertilizer and pesticide usage, and to the conquest of new cultural spaces. Considering itself to be flawed by a too hasty plunge into the market, concomitant with sagging evaluations of other innovations, Europe is confronted by a strong societal debate which blocks GMP cultures and orientates the research towards an evaluation of the environmental and public health risks and an evaluation of their economical and sociological impacts. The authors encourage this societal debate in order to arbitrate the presence of transgenes in conventional productions and products, to define the accepted rules of responsibility, to decide what is not acceptable, and to involve the more upstream actors and operators of the innovation process, all that keeping in mind the agronomical, ecological and economical repercussions of their decisions.

Animals↗

Molecular analysis of hypervirulent somatic hybrids of the entomopathogenic fungi Beauveria bassiana and Beauveria sulfurescens.

Protoplast fusion of diauxotrophic mutants of a Beauveria bassiana entomopathogenic strain (Bb28) and a Beauveria sulfurescens toxinogenic strain (Bs2) produced hybrids which were significantly different from the parents in pathogenicity. Some of the hybrids were hypervirulent and killed insects more quickly than the Bb28 strain, probably because these hybrids had acquired the toxic activity of the Bs2 strain. By using six nuclear genes and a telomeric fingerprint probe, the molecular structures of the hybrids were studied. The results demonstrated the occurrence of parasexual events. Hybrids appeared to be diploid or aneuploid, with portions of the genome being heterozygous. A mitochondrial molecular marker indicated homoplasmy of the hybrids and inheritance of mitochondria from strain Bs2 or Bb28. The pathogenicities and the ploidies of the hybrids remained stable after passage through the host insect, showing that somatic hybridization provides an attractive method for the genetic improvement of biocontrol efficiency in the genus Beauveria.

Aneuploidy↗

Isolation of the transposable element hupfer from the entomopathogenic fungus Beauveria bassiana by insertion mutagenesis of the nitrate reductase structural gene.

A transposable element has been isolated from the entomopathogenic fungus Beauveria bassiana by trapping it in the nitrate reductase structural gene, which has been cloned from this species. The element had inserted in the first exon of the nia gene and appeared to have duplicated the sequence TA at the site of insertion. It was 3336 bp long with 30-bp imperfect, inverted, terminal repeats. The element, called hupfer, contained an open reading frame encoding a 321-amino acid protein similar to the IS630- or mariner-Tcl-like transposases, and a residual sequence of about 2 kb which was not significantly similar to any published sequence. There are fewer than five copies of this transposable element present per genome in the fungus.

Amino Acid Sequence↗

28s rDNA group-I introns: a powerful tool for identifying strains of Beauveria brongniartii.

The nuclear ribosomal DNA of the entomopathogenic fungus Beauveria brongniartii is polymorphic in terms of both restriction site and length. Insertions of 350-450 bp long, identified as group-I introns, were detected in the 28s rDNA. A panel of 47 strains of B. brongniartii, two B. bassiana and one Metarhizium anisopliae of various geographical and biological origins were found to contain 14 variant forms of intron differing in size and restriction pattern, at four different positions. Twelve types of ribosomal large subunit were defined on the basis of variant distribution and compared with strain clustering based on internal transcribed spacers analysis. There was a correlation between the characteristic introns and isolates collected from the sugar cane pest Hoplochelus marginalis. Primers for polymerase chain reaction amplification were chosen from these variants, and used to develop a specific method for detecting strains pathogenic towards Hoplochelus.

Animals↗

[The evolutionary principles of inguinal hernioplasty through our personal experience].

Inguinal hernia is a multi-factorial pathologic condition. A constitutional weakness of transversalis fascia, probably genetically transmitted, represents a fundamental cause. Hernioplasty has evolved year by year from the "Bassini" to the "tension-free" techniques with Marlex or Prolene prosthesis, on the rational base of no tension on constitutionally weak structures. The data reported confirmed the absolute validity of "tension-free" hernioplasty.

Follow-Up Studies↗

Genetic Nature, Stability, and Improved Virulence of Hybrids from Protoplast Fusion in Beauveria

Genetic improvement of two different strains of the entomopathogenic fungus Beauveria bassiana for more effective control of Ostrinia nubilalis and Leptinotarsa decemlineata was obtained by crosses with the insecticidal toxin-producing strain Beauveria sulfurescens. Protoplast fusion between diauxotrophic mutants resulted in the recovery of some stable prototrophic fusion products. The low levels of virulence of the wild type strain B. bassiana 28 isolated originally from L. decemlineata were enhanced both on L. decemlineata and O. nubilalis for one of the hybrids obtained (FP 8) from the cross B. bassiana 28xB. sulfurescens 2. Fusion product 25 obtained from the cross between B. sulfurescens and the highly pathogenic strain B. bassiana 147 showed a three-day reduction in the LT50 towards O. nubilalis. Southern blot hybridization with nine probe-enzyme combinations were conducted on genomic DNAs from the original wild strains, parental mutant strains, and fusion products. Additive banding patterns or unique banding pattern of either parental strain was observed in five hybrids, indicating their status as recombinant and/or partially diploid. Combination of RFLP markers indicative of both parental genomes was never observed with fusion product FP 25. The stability of the virulence following passage through insect-host and stability of molecular structure for the fusion products FP 8 and FP 25 suggest that asexual genetic recombination by protoplast fusion may provide an attractive method for the genetic improvement of biocontrol efficiency in entomopathogenic fungi.

Journal Article↗

Use of solid state fermentation to produce Beauveria bassiana for the biological control of European corn borer.

The production process of a new bioinsecticide against european corn borer is described. The entomopathogenic fungus, Beauveria bassiana, is cultivated by Solid State Fermentation (SSF). The culture support chosen, clay microgranules, humidified with optimal nutritive solution, is incubated in optimal conditions during 48 hours, then dried for 5 days. The bioinsecticide can be directly used after harvesting, without formulation. This process is original for several reasons : - The granulometry (500 microm) and the bulk density (0.6) of the microgranules are compatible with the mechanical standard application of pesticides on corn. - The bioinsecticide could be produced in a pilot reactor of 1600 1 capacity, on 0.5m-thick-layer.- The biomass bound to microgranules conserves its efficiency after storage for 12 months at 4 degrees C, unlike pure cells. - Like the chemical insecticides usually used, this bioproduct has a field efficiency of 80%. Moreover, the efficiency of the product persists during 3 weeks.

Journal Article↗

rRNA sequence comparison of Beauveria bassiana, Tolypocladium cylindrosporum, and Tolypocladium extinguens.

Five strains of Tolypocladium cylindrosporum, one strain of Tolypocladium extinguens, and nine strains of Beauveria bassiana were analyzed using a rapid rRNA sequencing technique. The sequences of two highly variable domains (D1 and D2) located at the 5' end of the 28S-like rRNA molecule were determined. The phylogenetic tree computed from the absolute number of nucleotide differences shows the separation between the genus Beauveria and the genus Tolypocladium and points out that T. cylindrosporum and T. extinguens probably do not belong to the same genus.

Base Sequence↗

Infection of Aedes albopictus by Tolypocladium cylindrosporum.

The infection process of Tolypocladium cylindrosporum in Aedes albopictus is discussed. The integument is a common site of infection. Spores of T. cylindrosporum are able to adhere to the exoskeleton and penetrate it. During its early stages of development the fungus is always surrounded by a thick bacterial muff. However these bacteria did not invade the host, and no bacterial cell was observed on the intact cuticle. Conidia filtered by larvae rapidly filled the gut and most of them were hydrolyzed in the midgut. Even if germination occurred at a low level in the digestive tract, the peritrophic membrane and the mesenteral cells were not penetrated by fungus.

Aedes↗

Comparative studies of Metarhizium anisopliae and Tolypocladium cylindrosporum as pathogens of mosquito larvae.

Mosquito fungal pathogens, Metarhizium anisopliae and Tolypocladium cylindrosporum, were compared with regard to virulence against the larvae of Aedes aegypti, Anopheles stephensi and Culex pipiens. Culex pipiens larvae were much more susceptible to M. anisopliae conidia than An. stephensi or Ae. aegypti. But Ae. aegypti and Cx. pipiens larvae were equally susceptible to T. cylindrosporum propagules which weakly attack An. stephensi. Using a high concentration conidial suspension (10(7) sp/ml) of M. anisopliae no. 139, Ae. aegypti larvae were killed immediately within 1.1 days, before intrahemocoelian invasion; but at lower concentrations (10(6) and 10(5) sp/ml), typical mycosis occurred. However, T. cylindrosporum no. 3 blastospores were much more pathogenic to Ae. aegypti larvae than conidia. Conidial suspension of 10(7) spores/ml killed 68% fourth-instar larvae, relative to the 96% invaded by blastospores under the same conditions. Presoaked conidia virulence appeared still intermediate between conidia and blastospores. At low temperatures, 15 degrees C, virulence of M. anisopliae highly decreased, while at the same temperature, T. cylindrosporum blastospores were still virulent.

Animals↗