Trilobites Calmoniidae de l'Ordovicien supérieur du Maroc et les origines de la Province Malvino-Cafre

A re-examination of the trilobite Baniaspis globosa Destombes (Phacopina) from the Ashgill of the Anti-Atlas (Morocco) shows that it has several derived characters which allow us to classify it in the family Calmoniidae. Calmoniids were characteristic members of the Malvino-Kaffric province during the Lower Devonian. Hence we regard the origins of this palaeogeographic province as located on the northern Gondwanan margin as early as Ashgill, or even Caradoc, times. We agree with those authors who have suggested that the trilobite associations present in the Anti-Atlas, the Montagne Noire (France) and Bohemia during the earlier Ordovician argue against the existence of a 'proto-Tethys' ocean.     

Regeneration of leaf mesophyll protoplasts of tomato cultivars (L. esculentum): factors important for efficient protoplast culture and plant regeneration

Conditions were established for efficient plant regeneration from four freshmarket cultivars of Lycopersicon esculentum. In order to increase the yield of viable protoplasts which are able to sustain cell divisions, the donor plants are preconditioned by incubation at 25°C in the dark for 18 hours, followed by a cold treatment at 4°C in the dark for the last 6 hours, prior to protoplast isolation. Browning of the dividing cell colonies can be prevented by culturing protoplasts in 100 l droplets of low-melting agarose, surrounded by liquid medium. Alternatively, protoplasts can be cultured in liquid medium. In both procedures the plating efficiencies and percentage of shoot regeneration are increased, only when dilutions were performed with auxin-free culture medium. Shoot regeneration is obtained by using a two step procedure: initiation of greening of microcalli on a medium containing 0.2 M mannitol and 7.3 mM sucrose, which is followed by shoot development on a mannitol-free medium containing 0.5 M sucrose. In this way, plants can be regenerated within 3 months from the hybrid cultivars Bellina, Abunda, Sonatine and also from the true seedline Moneymaker. The latter one showed the highest regeneration frequency (30%).Abbreviations BAP 6-Benzylamino purine - 2,4-D 2,4-dichlorophenoxy acetic acid - IAA indole acetic acid - MES 2-(N-morpholino)- ethane sulfonic acid - NAA naphthalene acetic acid - PE plating efficiency     

Isolation and Characterization of a Copy Mutant of the Bacteriocinogenic Plasmid Clo DF13

After nitrosoguanidine mutagenesis, strain Escherichia coli P678-54, bacteriocinogenic for Clo DF13, yielded a mutant strain that showed an enhanced bacteriocin production. The results from conjugation experiments indicated that the mutation, responsible for the enhanced bacteriocin production, is located on the Clo DF13 plasmid. The following properties of strains harboring the mutant Clo DF13 plasmid could be observed. (i) The bacteriocin production in these strains can be further enhanced at least fourfold by mitomycin C. (ii) The fraction of spontaneously induced cells, as revealed by lacunae experiments, in cultures of these strains is about nine times higher than in cultures of wild-type Clo DF13-harboring strains. (iii) Chromosomeless minicells from strain P678-54 harboring the mutant Clo DF13 plasmid synthesize about six times more deoxyribonucleic acid, ribonucleic acid, and protein as compared to wild-type Clo DF13-harboring minicells. (iv) Analysis of this mutant Clo DF13-specific ribonucleic acid and protein on polyacrylamide gels revealed mainly the same ribonucleic acid and polypeptide species as synthesized by the wild-type Clo DF13 minicells, but in larger amounts (Kool et al., 1974). (v) Segregation experiments, using a strain with temperature-sensitive polymerase I, show that mutant Clo DF13-harboring cells contain an average of 70 Clo DF13 copies per cell, whereas wild-type Clo DF13-harboring cells contain only about 10 Clo DF13 copies per cell. The data presented in this paper indicate that the mutation on the Clo DF13 plasmid leads to an altered control of Clo DF13 replication and results in an enhanced number of Clo DF13 copies per cell. As a secondary effect, this enhanced number of Clo DF13 copies enhances the probability of "spontaneous" induction per cell. Since the mutation is plasmid specific and affects the number of plasmid copies produced, one can conclude that the Clo DF13 plasmid is not dependent solely on chromosomal information, but that at least plasmid base sequences are involved in Clo DF13 plasmid replication.     

Un biofacies à Trilobites Homalonotidae dans I'Ordovicien de la marge nord-gondwanienne: implications paléobiologiques et paléogéographiques

During the Llandeilo, the sandy lithological units which develop locally in the Armorican Massif, Spain and Morocco, are all characterized by similar trilobite associations in which endobenthic homalonotids. well adapted to shallow water and sandy substrate, are predominant. During the Llandeilo, on the northern Gondwanan margin, the wide geographical distribution of most of the trilobites, controlled by environmental factors, shows that the existence of a 'Proto-Tethys' ocean is unlikely. □ North Gondwana, Trilobita, Homalonotidae, Ordovician, Llandeilo. palaeoenvironment.     

Cloning of Petunia hybrida chloroplast DNA sequences capable of autonomous replication in yeast

Summary Sequences from Petunia hybrida chloroplast DNA which have the property to promote autonomous replication in Saccharomyces cerevisiae were cloned in vector YIp5. Seven cloned chloroplast DNA fragments are localized at one of two different sites on the chloroplast genome. One site, arsA was mapped on a 1.8 Kb fragment at position 27.0–28.8 Kb on the P. hybrida chloroplast genome. The plasmids containing this arsA are stable both in yeast and E. coli. The other site, arsB, was shown to be very unstable and is located either in the small single copy region close to the inverted repeat or just in the inverted repeat. The functioning of these sequences as a possible origin of replication in vivo is discussed.     

Isolation and characterization of a novel reassortant between avian Ty-1 and simian RRV rotaviruses.

A reassortant, TyRh, was isolated after coinfection of MA104 cells with avian Ty-1 and simian RRV rotaviruses. Hybridization and serological studies showed that the reassortant's 4th gene, which encodes Vp4, was derived from the simian RRV rotavirus parent, whereas the remaining 10 genes were derived from the avian Ty-1 rotavirus parent.     

Suction blister fluid as potential body fluid for biomarker proteins

Early diagnosis is important for effective disease management. Measurement of biomarkers present at the local level of the skin could be advantageous in facilitating the diagnostic process. The analysis of the proteome of suction blister fluid, representative for the interstitial fluid of the skin, is therefore a desirable first step in the search for potential biomarkers involved in biological pathways of particular diseases. Here, we describe a global analysis of the suction blister fluid proteome as potential body fluid for biomarker proteins. The suction blister fluid proteome was compared with a serum proteome analyzed using identical protocols. By using stringent criteria allowing less than 1% false positive identifications, we were able to detect, using identical experimental conditions and amount of starting material, 401 proteins in suction blister fluid and 240 proteins in serum. As a major result of our analysis we construct a prejudiced list of 34 proteins, relatively highly and uniquely detected in suction blister fluid as compared to serum, with established and putative characteristics as biomarkers. We conclude that suction blister fluid might potentially serve as a good alternative biomarker body fluid for diseases that involve the skin.     

Asymmetric recognition of DNA local distortion. Structure-based functional studies of eukaryotic Msh2-Msh6

Crystal structures of bacterial MutS homodimers bound to mismatched DNA reveal asymmetric interactions of the two subunits with DNA. A phenylalanine and glutamate of one subunit make mismatched base-specific interactions, and residues of both subunits contact the DNA backbone surrounding the mismatched base, but asymmetrically. A number of amino acids in MutS that contact the DNA are conserved in the eukaryotic Msh2-Msh6 heterodimer. We report here that yeast strains with amino acids substituted for residues inferred to interact with the DNA backbone or mismatched base have elevated spontaneous mutation rates consistent with defective mismatch repair. Purified Msh2-Msh6 with substitutions in the conserved Phe(337) and Glu(339) in Msh6 thought to stack or hydrogen bond, respectively, with the mismatched base do have reduced DNA binding affinity but normal ATPase activity. Moreover, wild-type Msh2-Msh6 binds with lower affinity to mismatches with thymine replaced by difluorotoluene, which lacks the ability to hydrogen bond. The results suggest that yeast Msh2-Msh6 interacts asymmetrically with the DNA through base-specific stacking and hydrogen bonding interactions and backbone contacts. The importance of these contacts decreases with increasing distance from the mismatch, implying that interactions at and near the mismatch are important for binding in a kinked DNA conformation.