Équilibres conformationnels de glucides au niveau de liaisons σ SP-SP: Partie V. Dérivés 2,3,-O-isopropylidène de pyranosides hybrides sp en C-4. Comparaison avec leurs analogues saturés

The conformation in solution of derivatives of methyl hexopyranosides has been studied by n.m.r. The esters of methyl 2,3-O-isopropylidene-α-D-manno- and -talopyranosides as well as their 4-deoxy-4-C-methyl analog having a manno configuration exist mainly in a flattened (^4,0F) chair conformation (⁴C₁). The presence in the talo epimer of the 4-deoxy-4-C-methyl analog of the bulky methyl group on the endo side of the bicyclic system results in a skew form (³S₁). The methyl 4-deoxy-2,3-O-isopropylidene-4-C-methylene-α-D-lyxo-hexopyranosides monosubstituted at C-4′ adopt, in solution, a conformation close to ³S₁, whichever their configuration (cis or trans) at the double bond, as indicated by their allylic coupling constants.     

我国微茎类吸虫研究:ⅩⅢ.微茎类吸虫成虫结构特征排序

对我国52种微茎类吸虫的18项成虫形态学特征进行主成分分析,结果表明:卵巢位置、子宫延伸位置等7项性状对第一主成分贡献较大,提示描述器官位置的指标是重要的分类依据。52个虫种在前三个主成分上的排序图显示应将其划分成4个亚科。     

Inositol (1,4,5)trisphosphate-promoted Ca2+ release from microsomal fractions of rat liver

Crude mitochondrial fractions containing a substantial amount of microsomes accumulate Ca2+ in the presence of ATP, ruthenium red and oligomycin. A proportion of this accumulated Ca2+ is released by the addition of low concentrations (ca. 1 microM) of inositol (1,4,5) trisphosphate . Under some conditions the release is transient, and evidence is presented which suggests that this is due to inhomogeneity in the vesicle population. (1,4,5)inositol trisphosphate -induced Ca2+ release can also be demonstrated, under appropriate experimental conditions, in a more purified microsomal fraction essentially free of mitochondria.     

Distribution of repeated DNA families in the human genome

By means of restriction enzymes analysis and molecular hybridization, the distribution of repeated DNA families has been studied in the different DNA components into which the human genome can be fractionated by density gradient techniques. Three classes of DNA molecules have been analyzed: i) an homogeneous DNA component (satellite-like sequences; Q = 1.696 g/cm3, 3% of total DNA, AT repeated), ii) AT rich (Q = 1.698 g/cm3, 30% of total DNA, AT main-band) and GC rich (Q = 1.708 g/cm3, 6% of total DNA, GC main-band) DNA components. By this approach we have observed that Sau3A digestion of GC main-band gives rise to two bands of 75bp and 150bp, absent or under-represented in both AT rich DNA components. A preliminary characterization of these DNA fragments suggests that they contain one or more families of repeated sequences which fail to hybridize to EcoRI, HindIII and AluI families of repeats. In addition, we have observed that EcoRI sequences (alpha-RI DNA) are under-represented in GC main-band and show the same clustered organization in both AT rich DNA components.     

Les ammonites boréales des formationsnéocomiennes du Sud-Est français (province subméditerranéenne)

The boreal Ammonites (and the more or lessphylogenetically related ones) of the southeast France (Tethyan Realm) are described and figured. 24 forms are refered to, or compared with, previously identified species. 3 are left under open nomenclature, and 7 are new ones. Two new subgenus: Julianites (Paquiericeras) and Lemurostephanus (Olcostephanus) are also introduced.Their biostratigraphic position in the Frenchzonal scheme is detailed. Their contribution to the establishment of correlation between the Boreal and Tethyan provinces is stressed.The most interesting feature is the identification of a Prodichotomites horizon just below the Verrucosum zone, allowing comparison of the definition of the Lower-Upper Valanginian boundary in these two paleobiogeographic realms.     

Influence de la teneur en oxygène sur la sensibilité de certains stades juvéniles deSitophilus oryzae etS. granarius au dioxyde de carbone

Résumé Certains stades juvéniles de charançons des céréales du genreSitophilus ont été soumis à un séjour prolongé dans des compositions gazeuses modifiées par le dioxyde de carbone (CO₂).Les auteurs se sont placés dans des conditions de teneur en CO₂ constante (50%), associée à des teneurs en oxygène comprises entre 4 et 20%, pour étudier les conditions d'une synergie entre l'effet spécifique du CO₂ et la présence d'une forte teneur résiduelle en oxygène. Les effets ont été observés sur les stades juvéniles les plus évolués (larves et nymphes) des espècesS. oryzae (L.) etS. granarius (L.), (Coleoptera: Curculionidae).L'accroissement de la vitesse de mortalité chezS. oryzae est significative avec l'augmentation de la pression partielle d'oxygène. Cet effet de synergie provoqué par l'oxygène n'est pas significatif avecS. granarius, bien qu'il existe aussi avec cette espèce une tendance à l'amélioration de l'efficacité insecticide à court terme avec les mélanges à forte teneur résiduelle en oxygène.Il en est déduit des hypothèses sur les effets des mélanges gazeux à composition modifiée par le CO₂ au niveau de la physiologie générale de ces insectes, qui est très difficile à appréhender directement à cause du mode de développement des stades juvéniles des charançons (formes cachées dans le grain).     

Les Rhynchonelles du Bathonien du domaineprovencal: Liaison entre l'installation des peuplements et les modalités de la transgression bathonienne dans les Alpes-Maritimes

In the Maritime Alps, the Middle and Upper Bathoniancorresponds to a transgressive episode on the Provençal platform. The advancement of the marine invasion is very noticeable between Grasse and Antibes. The sediment shows the existence of a shallow marine environment in which benthic organisms were predominant.The deposits are at first varied: marly layers withbivalves (burrowers for the most part) and calcareous layers with monospecific populations of brachiopods (Burmirhynchia mediterranea nov. sp. in a calm environment, and B. turgidaBuckman in a more turbulent environment).The deposits then become uniform and show theexistence of very shallows environments: B. decorata kiliani nov. subsp. is the only representative of macrofauna in the micritic limestones that can be attributed to the Upper Bathonian.The Rhynchonellids, as on the other Bathonian carbonateplatforms of Western Europe, seem to be the only organisms likely to stay alive and proliferate in the specific environments in which entirely carbonate sediments are deposited in shallow water. Due to their relationships to those existing in other platforms, the species described in this article permit the clarification of biostratigraphic correlations.     

Le prétendu rhinocéros de Nouvelle Calédonie est un marsupial (Zygomaturus diahotensis nov. sp.): Solution d'une énigmeet conséquences paléogéographiques

The first mammalian remain ever found in NewCaledonia is an upper tooth found by golddiggers in the Plio-Pleistocene terrace from the Diahot river. This tooth, given to the Muséum national d'Histoire naturelle (Paris) in 1876, was determined as a rhinoceros tooth and then completely forgotten. Its detailed study shows that it belongs to Zygomaturus, a large marsupial diprotodontid genus whose story is rather complicated. The Diahot tooth represents a new species of Zygomaturus, Z. diahotensis nov. sp., close to Z. trilobus from the Australian Pleistocene. That kinship suggests a Plio-Pleistocene land connection between Australia and New Caledonia, whereas till now New Caledonia was supposed to be separated from Australia since the end of the Cretaceous, because of the total absence of indigenous mammals, fossil or recent, in New Caledonia. The latest geological studies in the East Pacific do not contradict our hypothesis.     

Genetic analysis of transpositions in the lac region of Escherichia coli

The lac region of Escherichia coli, carried on an F′ lacproB episome, was used as a target for the transposition of several transposable elements. Tn9 shows a preferential integration (by a factor of 50) into a region extending from the end of the Z gene through the Y gene. Throughout the remainder of the lacI, Z and Y genes one other short region, located in the middle of the I gene, is favored for integration. Within these favored regions many different integration points are evident. Inspection of the DNA sequence for the I and Y genes, and parts of the Z gene, shows a strong correlation between A + T richness and regions of preferential integration. Tn5 insertions follow a similar pattern, although with less preference; whereas Tn10 insertions (provided by T. J. Foster), also favor the Y gene and the end of Z, but are distributed among fewer integration points. Most of the Tn3 insertions into the episome are accompanied by a nearby or adjacent deletion.