Insect growth regulator activity of Cestrum parqui saponins: an interaction with cholesterol metabolism.

Cestrum parqui is an ornamental shrub known for its insecticidal activity against some insect pests; this activity comes from the crude saponic extract of the leaves of this plant, the saponins cause insect growth regulator symptoms (development and moulting perturbation). In this work we try to demonstrate the hypothesis that saponins interact with ecdysone (moulting hormone) synthesis mechanisms by reducing diet cholesterol absorption (cholesterol forms the skeleton of ecdysone and of other ecdysteroids). To show the cholesterol/saponin interaction we used a stored product pest insect (Tribolium confuisurn), the larva of this insect are affected by saponins added in their diet, but the addition of cholesterol permits to reduce significatively this insecticidal propriety. Using Spodoptera littoralis larva model the tentative to detect a cholesterol rate reduction on the level of hemolymph is also unsuccessful. All these experiments shows that this type of reaction can't occur in the diet or in the digestive system but probably in insect cells. It is clear that Cestrurn parqui saponins affect the cholesterol metabolism but the exactly mechanism is still unknown. More investigations are necessary to develop this hypothesis and to envisage the use of Cestrum saponins as insect growth regulator bioinsecticide.

[The effect of food containing Cestrum paquii (Solanaceae) extract on various damaging Lepidoptera]. / L'impact de l'alimentation contenant du broyât de Cestrum paquii (Solanacées) sur des lépidoptères dommageables.

The repulsive activity of Cestrum parquii on the feeding behaviour of Pieris brassicae L. and Spodoptera littoralis Boisduval was studied. Antifeedant effect was observed at regular intervals during a week. Meal uptake was stopped after the first day, showing a strongly antifeedant effect of C. parquii extract on these two species. The impact of C. parquii with different concentrations of dry extract (2, 4, 8, 16, 32%) delayed the larval growth of Spodoptera littoralis Boisduval compared to untreated insects. Abnormal metamorphosis was observed with concentrations of 8 and 16% leading to death and abnormal morphogenesis. The antifeedant activity of C. parquii was also observed in S. littoralis and measured by the evolution of food uptake and the weight of larva. Effect seemed to be proportional to extract concentration in the diet. High concentration (32%) stopped growth in the earlier instar.

[Immunological similarities between two cerebral substances from Schistocerca gregaria and two neurohormones from Locusta migratoria]. / Similitudes immunologiques entre les substances cérébrales de Schistocerca gregaria et deux neurohormones de Locusta migratoria.

Two neurohormones produced by two distinctive neurosecretory median cells (A1, B) of the protocerebum have been characterized in Locusta migratoria; on with a multiple functions one called neuroparsin and one stimulating the ovarian maturation called lom OMP. Using the specific immunoserum of these two neurohormones in Schistocerca gregaria, we could demonstrate the occurring of molecules related to the neuroparsin and lom OMP of Locusta. Through histology studies of the brain and corpora cardiaca complex, the immunoserum revealed the presence of the two types of these neurosecretory cells suggesting the occurring in Locusta as well as Schistocerca of the same cells releasing molecules immunologically apparented to neuroparsin and lom OMP. The results were confirmed by electrophoretic separation of corpora cardiaca extract under unreduced conditions followed by a transfer on immobilon membrane.

[Salivary glands of Myzus persicae (Homoptera, Aphididae): structure and secretory rhythm]. / Les glandes salivaires de Myzus persicae (Homoptera, Aphididae): structure et rythme secrétoire.

The salivary glands of Myzus persicae (Homoptera, Aphididae): structure and secretory rythm. Studying the structure of the salivary glands of Myzus persicae, a particular mode of working of these organs were observed. The glands seem to function in an alternative manner. This aspect is discussed with regards to the nutritional biting of the bug.

[Characterization of vitellogenins and vitellines in Ceratatitis capitata (Diptera, Trypetidae): electrophoretic and immunoelectrophoretic study]. / Caractérisation des vitellogenines et des vitellines chez Ceratitis capitata (Diptera, Trypetidae): etude électrophorétique et immuno-électrophorétique.

Electrophoretic study of haemolymphatic proteins in Ceratitis capitata has allowed to establish a proteic sexual dimorphism in this insect. This consists in a proteic fraction which is specific to the male and which appears at the imaginal ecdysis and stays during all the imaginal stage and in 3 other fractions which are characteristic to the female. Immuno electrophoretic study showed that these female proteins could be considered as vitellogenins. The nature and the mode of incorporation of those proteins in the oocyte are discussed.

[Prolixase, a fibrinolytic enzyme isolated from Rhodnius prolixus (Heteroptera, Reduviidae): antigenic properties]. / La prolixase, enzyme fibrinolytique isolée à partir de Rhodnius prolixus (Heteroptera, Reduviidae): propriétés antigéniques.

Antigenic properties of prolixase are studied showing that this fibrinolytic enzyme, induces in the rabbit, the formation of precipitating but slightly, hemagglutinating homologous antibodies.

[A new plasminogen activator isolated from the saliva of Rhapactor biparticeps (Heteroptera, Reduviidae): biological and physicochemical properties]. / Un nouvel activateur du plasminogène isolé à partir de la salive de Rhapactor biparticeps (Heteroptera, Reduviidae): Propriétés biologiques et Physicochimiques.

A new plasminogen activator has been isolated from the saliva of Rhapactor biparticeps. This product is 5% of salivary proteins and acts at an optimal pH of 7.8.P.D.F which results from its action on human fibrinogen are similar to those which are obtained with streptokinase. The modalities of action of this plasminogen activator on the fibrinogen are discussed.

[Identification of plasminogen activators in the saliva of Rhapactor biparticeps (Reduviidae)]. / Identification d'activateurs du plasminogène dans la salive de Rhapactor biparticeps (Reduviidae).

Plasminogen activators are identified in the saliva of Rhapactor biparticeps using a particular technique which includes human fibrin in polyacrylamide gel. This technique is described and results are discussed according to classical methods used for fibrinolysis studies.

[Parasitic effect of Opius concolor (Spzl) (Hymenoptera, Braconidae) on an intermediate host Ceratitis capitata Wied (Diptera, Trypetidae)]. / Incidence parasitaire d'Opius concolor (Spzl) (Hymenoptera, Braconidae) sur un hôte de remplacement Ceratitis capitata Wied (Diptera, Trypetidae).

The parasitic incidence of Opius concolor (Hymenoptera, Braconidae) on a replacement host, Ceratitis capitata (Diptera, Trypetidae) was studied using polyacrylamide gel electrophoresis and immunoelectrophoresis methods. A noticeable modification of C. capitata proteins was observed when parasited by O. concolor. But the most important phenomenon is the finding of common antigens between the host and the parasite. These results are discussed with regard to trophic and parasitic behaviour of the parasite.

[Demonstration of plasminogen activators in the saliva of a predatory insect of the family of Reduviidae (Heteroptera)]. / Mise en évidence d'activateurs du plasminogène dans la salive d'un insecte prédateur de la famille des Reduviidae (Heteroptera).

The study of digestive and salivary proteases of Rhapactor biparticeps, has shown that the salivary glands of this insect are rich in proteolytic enzymes, however, the gut has none. The characterisation of these enzymes on different substrates showed that they are only active on fibrinogen and plasmatic proteins which are involved in the coagulation system. Among these fibrinolytic enzymes that has been identified and characterized, are the plasminogen activators. Their unexpected presence in the entomophagic insect is discussed.

Description of new fibrinolytic enzyme, isolated from the haemolymph of Rhodnius prolixus Stal (Heteroptera Reduviidae).

A new fibrinolytic enzyme, isolated from the haemolymph of Rhodnius prolixus Stal (Heteroptera, Reduviidae) has been discovered. This enzyme does not act by activating plasminogen to plasmin. However, the split products obtained with this new enzyme inhibit fibrin formation in normal plasma. This enzyme seems to act specifically on the proteins involved in blood coagulation. Its origin has induced us to name it prolixase.

[Demonstration of an enzyme inhibiting coagulation of blood ingested by the blood-sucking insect, Rhodnius prolixus (Heteroptera, Reduviidae)]. / Mise en évidence d'une enzyme conduisant à l'inhibition de la coagulation du sang ingéré par un insecte hématophage, Rhodnius prolixus (Heteroptera, Reduviidae).

A new fibrinolytic enzyme, "the prolixase", was isolated and purified from the haemolymph of Rhodnius Prolixus. The mode of action of the enzyme was studied and compared to that of extracts from salivary glands and midgut of the insect. It appears that the prolixase is involved in inhibiting the coagulation of the blood ingested by Rhodnius during its blood meal. The mode of action of the enzyme in this phenomenon is discussed.