Distribution et activités des alcaloïdes défensifs des Coccinellidae

From a survey of 30 species and varieties of ladybugs the presence of alkaloids appears to be correlated with the existence of aposematic colour and not with being carnivorous or phytophagous. The alkaloids described until now all belong to the Coccinellini and are closely related, but other types of bases have been detected in some genera. The observed distributions are in agreement with the modern taxonomy of the family.Ladybug alkaloids constitute an effective defence against ants, Myrmica rubra, and quails, Coturnix coturnix, but all the beetles containing alkaloids do not possess the same degree of protection. Individual quail react differently towards moderately protected species.The bioassay used for the first isolation of coccinelin is described. The repulsive activities of aqueous solutions of coccinellin and convergin towards ants have been compared.     

Les vertébrés dévoniens de l'Iran central I: Dipneustes

The dipnoan dental plates discovered in the Frasnian of the Kerman region (Central Iran) are referred to the genera Rhinodipterus, ? Dipterus and ? Chirodipterus. The new taxon Iranorhynchus seyedemamii n. g., n. sp. is erected for a peculiar lower jaw with an elongate, spatula-shaped symphysial region, and with all the ventral and lateral dermal bones fused into a continuous exoskeleton. Furthermore, this lower jaw possesses a well-developed system of symphysial tubuli which is related to the bottle-shaped cavities of the exoskeleton (pore-canal system). A snout fragment from a large dipnoan is provisionnally referred to a rhynchodipterid.     

Action de l'ecdystérone sur l'apolysis et l'ecdysis de divers crustacés isopodes

Ecdysterone acts differently according to the period of the moulting cycle when it is applied. In period C it induces apolysis, while at the beginning of apolysis it delays ecdysis. Experiments show that the exoskeleton cannot be rejected in the presence of ecdysterone. The possibility of stopping exuviation or ecdysis with ecdysterone seems to prove that this phenomenon is controlled by a particular factor called the factor of exuviation or the ecdysis factor. Ecdysterone would control only the release of this specific factor but would not prevent its action.     

Activité cytokinine de dérivés acylés,alkylés,acyl-alkylés de l'adénine et d'isost`eres azotés de la γ,γ-diméthylallyladénine

The cytokinin activities of various 6-acylaminopurines, 6-alkylaminopurines, 6-acylamino-9-benzyl-purines as well as a series of isosteric-nitrogen derivatives of N⁶-(γ, γ-dimethylallyl)adenine (I⁶Ade) have been tested using the tobacco pith and the pea bud bioassays. The interactions between active, slightly active and inactive compounds have been studied with the last assay. Acylation decreases the biological activity; e.g., N⁶-benzoyl and N⁶-furoyladenines are less active than Na⁶-benzyladenine and kinetin. Substitution at the 9-position reduces (tobacco-pith assay) or suppresses (pea-bud assay) the phytohormonal activity of otherwise active 6-acylaminopurines. In isosteric derivatives, maximum activity occurs when the side chain has the same length as in 1⁶Ade. After the analysis of interactions between more or less active compounds, it is suggested that the differences in cytokinin activity could be related to unequal affinities for a hypothetical receptor site.     

Relation métabolique entre l'arginine et l'acide γ-aminobutyrique dans le fruit de Castanea sativa: étude préliminaire de l'arginase

Analysis of the free amino acid pool in the chestnut fruit (Castanea sativa) shows that it is high in γ-aminobutyric acid. A metabolic connection between arginine and γ-aminobutyric acid is evident. Three enzymatic activities are involved: L-arginine ureohydrolase, L-ornithine 2-oxo-acid aminotransferase and L-glutamate carboxylyase.     

Stabilité de l'espèce et évolution: La théorie de l'équilibre intermittent («Punctuated equilibrium)

Paleontologists' traditional conceptions on evolution do not seem to be in perfect accord with these of biologists. The gradual phyletism is compatible neither with E. Mayr's model of the Founder, nor with the actual stability of most of the paleontological species. The punctuated equilibrium model proposed by N. Eldredge & S.J. Gould offers a solution which integrates both paleontological observations and the data of modern biology.     

Cycles embryonnaires et sécrétion de la cuticule chez l'embryon de blatte, Blabera craniifer

Cuticle deposition has been studied with the electron microscope in cockroach embryos (Blabera craniifer) during normal incubation in situ and in culture in vitro, in the absence or presence of inokosterone (a phytoecdysone).Two cuticles are deposited successively during embryonic life, respectively between stages 11 and 17, and stage 21 and 24 hr after hatching. The occurrence of two embryonic cycles is thus demonstrated, the first ending at stage 17 without exuviation since there is no old cuticle to be shed, the second one at hatching.In embryos explanted at stage 17 and cultured in vitro, the formation of cuticle 2 occurred at the same rate as in situ. The addition of inokosterone (50 μg/ml) to the medium resulted in the early onset of cuticle deposition (in 3 days as compared with 15 days in situ) in legs previously cut at the base of the tarsus. Cuticle 2 was completed within 9 days after explantation (as compared with about 20 days elapsing in the normal embryo between stage 17 and the completion of cuticle 2). Unsectioned appendages were insensitive to the hormone.Regeneration of sectioned legs, which occurred normally n vitro in non-treated embryos, was completely inhibited in the presence of inokosterone, presumably because the hormone caused early immobilization of cells through accelerated cuticle formation.Results suggest that embryonic cycles are controlled by the same hormonal mechanism as larval cycles.     

Action de l'antimycine a sur l'activité succinoxydase des mitochondries du tubercule de Pomme de Terre,et comportement des cytochromes de type b

A kinetic study of the effect of antimycin A on succinate oxidase from plant mitochondria produced sigmoidal curves for the reduction of cytochromes b₅₆₀ and b₅₈₅ and for the inhibition of succinate oxidase. In the stationary state the interaction of the various components of the respiratory chain (flavins, ubiquinone, cytochromes…) occurs in a sequential mode which allows the application of simple equations utilizing rate constants and cytochrome concentrations. In these equations, it is assumed that there exists an excess of ubiquinone relative to other components of the respiratory chain as suggested by Kröger & Klingenberg (1970) and that the reoxidation of b cytochromes is fast. The inhibition by antimycin A, characterized by non-linear inhibition curves for succin-oxidase and inhibitor fixation in complex III on a component other than cytochrome c₁, is interpreted in terms of this model. This hypothesis presupposes the existence of an F factor between cytochrome b₅₆₀ and cytochrome c₁ as suggested by other authors. Utilizing these equations, theoretical curves for the inhibition of the reduction of cytochrome b₅₆₀ have been constructed and the results agree with the experimental data. The kinetic behavior of cytochrome b₅₆₆ during the induction of anaerobiosis suggests that it is not directly involved in the electron transfer chain but rather is either in thermodynamic equilibrium with cytochrome b₅₆₀ or in a shunt between cytochrome b₅₆₀ and factor F. From the experimental data, an equation is derived for the inhibition of the reduction of cytochrome b₅₆₆ by antimycin A. The actual effects of ATP and mClCCP on succinoxidase agree well with those predicted by the model.     

Les constituants flavonoïdes de Cephalanthus spathelliferus

We have isolated from Cephalanthus spathelliferus (Rubiaceae) five compounds: umbelliferone, skimmin, 7,4′-dimethylkaempferol,7,4′-dimethylaromadendrin and its 5-glucoside. The latter two are new compounds.     

La sculpture et l'infrastructure du sporoderme de Ginkgo biloba comparées à celles des enveloppes polliniques des cyccadales

The Ginkgo biloba sporoderm, when examined with transmission and scanning electron microscopes, shows a sculpture and a texture which are very different from those observed in cycads.The ornamental units are “rugules” which are evenly disperesed over the pollen grain surface except on the germinal zones which is decorated with “verrucoïde” components mixed with a few ridges. (2) The exine is composed of a tripartite sexine, the middle zone of which is full of irregular pits, and of a thick and strongly lamellated nexine.     

Xanthonolignoids from Kielmeyera and Caraipa species—13C NMR spectroscopy of xanthones

Kielcorin and the cadensins A and B, isolated respectively from Kielmeyera coriacea and Caraipa densiflora (Guttiferae), were shown to be xanthonolignoids. The structure of (5S,6S)-6(or 5)-hydroxymethyl-5(or 6)-(4″-hydroxy-3″-methoxyphenyl)-2,3:3′,4′-(2′-methoxyxanthono)-1,4-dioxane was proposed for kielcorin by analysis of high resolution MS and PMR spectra. The carbon shifts of xanthone were assigned and used in the ¹³C NMR spectral confirmation of the proposed structure.     

Influence du corps gras sur l'évolution de l'ovaire nymphal de Tenebrio molitor, étude en culture in vitro

In Tenebrio molitor, the fat body contains several factors able to control the evolution of the pupal ovary in vitro. One or several factors soluble in ether inhibit the initiation of oöcyte growth. One or several factors insoluble in ether stimulate the course of this growth, folicle organization, and the appearance of the transitory zone. The inhibitory action of the fat body is greatest towards the middle of the pharate adult stage. The stimulatory action of this organ is maximum at the beginning of pupal life and during the approach of adult ecdysis.     

Anticorps anti-spermatozoïdes: techniques de dépistage et interprétation des résultats

Since the first publication on the detection of sperm-agglutinating antibodies in infertile men, multiple assays have been described. The most useful tests are able to detect antibodies bound to the sperm membrane of motile spermatozoa. The immunobeads test (IBT) is considered to be the most advantageous in terms of its sensitivity, the low incidence of false-positive results, and its ability to localize antibodies of different immunoglobulin classes on the sperm surface. The IBT assay can be used in parallel with the mixed antiglobulin reaction (MAR), to detect sperm-associated antibodies in the ejaculates of infertile men, the most rational way to test for antisperm antibodies (ASA) in males. In view of the high level of agreement between the two assays, MAR, the easier of the two, may be used as a first step in the detection of these antibodies. A positive MAR must be confirmed by IBT, as this assay is more specific for the detection of IgA antibodies. The clinical significance of sperm-associated antibodies is usually established according to the proportion of motile spermatozoa coated with immunobeads, its class and its localization on the sperm surface. However, binding of immunobeads does not provide any information about the antigens against which the antibodies are directed. As the functional effects of sperm-associated antibodies may vary as a function of their antigenic specificities, other assays, using purified fertilization related antigens, are necessary to establish, for each individual, the specific impact of the antibodies on the fertilization process. The indirect IBT assay has recently become the most widely used test to detect the various classes of ASA in serum and cervical mucus of infertile women and in the serum and seminal fluid of infertile men, in combination with the direct assay described above. However, in most laboratories, it is performed with only one dilution of the biological fluid tested, usually a low dilution, so that antibody levels of no significance for fertility could be detected. This may explain a recente debate (Human Reprod, 1999) on the significance of ASA as a cause of infertility. At present, and in the absence of standardized assays able to identify the antigens involved in each individual immune reaction, antibody assays, as detected by the IBT assay, in the serum and/or genital secretions of infertile subjects might provide useful clinical guidance.     

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.     

Rôle des organes pulsatiles thoraciques et du cœur pendant l'émergence et l'expansion des ailes des lépidoptères

Electrograms of the thoracic pulsatile organs and of the heart during emergence and expansion of the wings have been made. The mesotergal and metatergal organs function in a similar way: active periods are interrupted by short periods of rest, but the two organs contract with different but apparently independent rhythms. During emergence and expansion, the rate of contraction of the pulsatile organs increases twofold, and the resting periods disappear during the entire period of expansion of the wings. When the wings are removed or cut short, the activity of the pulsatile organs is inhibited.     

Alcaloïdes de Zanthoxylum decaryi: la decarine,nouvel alcaloide dérivé de la benzophénanthridine

Four alkaloids have been isolated from the stem bark of Zatithoxylum decaryi. Three are known, dictamnine skimmianine, 4-methoxy-1- methyl-2-quinolone. The fourth decarine is new; its structure has been established as 9-methoxy-10-hydroxy-2,3-methylenedioxybenzophenanthridine.¹