LIPOSOME-INCORPORATED SANTOLINA INSULARIS ESSENTIAL OIL: PREPARATION,CHARACTERIZATION AND IN VITRO ANTIVIRAL ACTIVITY

The effect of liposomal inclusion on the stability and in vitro antiherpetic activity of Santolina insularis essential oil was investigated. In order to study the influence of vesicle structure on the liposome properties, multilamellar and unilamellar vesicles were prepared by the film method and sonication, respectively. Vesicles were obtained from hydrogenated soya phosphatydilcholine and cholesterol. Formulations were examined for their stability for over one year monitoring the drug leakage from vesicles and the average size distribution. The stability of the incorporated oil was verified by studying its quali-quantitative composition. The antiviral activity was studied against Herpes simplex virus type 1 (HSV-1) by plaque reduction and yield reduction assays. Results showed that Santolina insularis essential oil can be incorporated in high amounts in the prepared liposomes, which successfully prevented its degradation. Moreover, stability studies pointed out that vesicle dispersions were stable for at least one year and neither oil leakage nor vesicle size alteration occurred during this period. Antiviral activity assays demonstrated that Santolina insularis essential oil is effective in inactivating HSV-1 and that the activity is principally due to direct virucidal effects. Free essential oil proved to be more effective than liposomal oil and a different activity was discovered which related to the vesicular structure. The ED₅₀ values, significantly lower when cells were pre-incubated with the essential oil before the virus adsorption, indicate an intracellular mechanism in the antiviral activity of Santolina insularis. Moreover, liposomal Santolina essential oil is non toxic in the range of the concentration tested.     

Seasonal variation of the chemical constituents of the essential oil of Santolina etrusca from Italy

The seasonal variation of the essential oil, in terms of both yield and composition, of a population of Santolina etrusca (Asteraceae) is reported in detail for different aerial parts, including sterile branches, fertile branches, and capitula. The yields generally increased from November to June, and then decreased in August and September. The main constituents of the sterile branches were 1,8-cineole and viridiflorol. The oil from fertile branches was characterized by myrcene as principal compound, whereas the essential oil obtained from the capitula contained germacrene D as the main constituent. Several compounds, as identified by GC and GC/MS, were found to prevail during the cold season.     

Morphological and ultrastructural characterization of the alimentary canal in larvae of Streltzoviella insularis (Staudinger) (Lepidoptera: Cossidae)

Streltzoviella insularis (Staudinger) is an important tree‐boring pest, that primarily damages Sophora japonica (Linnaeus) and Ginkgo biloba (Linnaeus), as well as other common species, at great economic cost to the urban landscape construction industry in China. In the present study, the alimentary canal morphology of S. insularis was observed using light microscopy, and its ultrastructure was investigated by scanning and transmission electron microscopy. The foregut of S. insularis can be divided into the pharynx, esophagus, crop, proventriculus, and cardiac valve. The well‐developed crop forms the longest section of the foregut. It is able to store large amounts of food and is lined with a monolayer of epithelial cells. Many sclerotized microspines occur on the surface of the anterior intima and there are dense spines on the posterior intima of the proventriculus. Epithelial cells of the midgut include columnar cells, goblet cells, and regenerative cells, but endocrine cells are absent. The hindgut consists of the pyloric valve, ileum, and rectum. There is no clear distinction between the ileum and colon. The intima surface of the pyloric valve carries many microspines, whereas the intestinal wall of the rectum is thin with well‐developed rectal pads. The rectal epithelial cells form a squamous monolayer. A cryptonephric excretory system is located in the hindgut. There are six spiral Malpighian tubules, in which a cellular layer on a basement membrane encloses a lumen. These results will provide the basis for further studies of the structure and function in S. insularis larvae.     

Epoxidation and hydration of prenyl pyrophosphates by plant extracts

Cell-free extracts of Tanacetum vulgare, Artemisia annua, and Santolina chamaecyparissus contain seasonally-dependent enzyme systems that convert IPP4, DMAPP, GPP and NPP into water-soluble products in up to 96% yield. 3-Methyl-3,4-oxidobutan-1-ol; 3-methylbutan-1,3,4-triol; 3,7-dimethyl-6,7-oxido-octa-trans-2-en-1-ol; and 3,7-dimethylocta-trans,trans-2,5-dien-1,7-diol were major products when IPP and GPP respectively were substrates and several other terpene epoxides and their ring-opened products were tentatively identified. 2-CEPA blocked formation of diols from the epoxides. The occurrence of these enzymes accounts for some hitherto puzzling observations that have arisen in studies of monoterpene biosynthesis both in vivo and in vitro.     

Phylogeography of the Bothrops jararaca complex (Serpentes: Viperidae): past fragmentation and island colonization in the Brazilian Atlantic Forest

The Brazilian Atlantic Forest is one of the world's major biodiversity hotspots and is threatened by a severe habitat loss. Yet little is known about the processes that originated its remarkable richness of endemic species. Here we present results of a large-scale survey of the genetic variation at the mitochondrial cytochrome b gene of the pitviper, jararaca lancehead (Bothrops jararaca), and two closely related insular species (Bothrops insularis and Bothrops alcatraz), endemic of this region. Phylogenetic and network analyses revealed the existence of two well-supported clades, exhibiting a southern and a northern distribution. The divergence time of these two phylogroups was estimated at 3.8 million years ago, in the Pliocene, a period of intense climatic changes and frequent fragmentation of the tropical rainforest. Our data also suggest that the two groups underwent a large size expansion between 50,000 and 100,000 years ago. However, the southern group showed a more marked signal of population size fluctuation than the northern group, corroborating evidences that southern forests may have suffered a more pronounced reduction in area in the late Pleistocene. The insular species B. alcatraz and B. insularis presented very low diversity, each one sharing haplotypes with mainland individuals placed in different subclades. Despite their marked morphological and behavioural uniqueness, these two insular species seem to have originated very recently and most likely from distinct costal B. jararaca populations, possibly associated with late Pleistocene or Holocene sea level fluctuations.     

Intra-specific differences in cognition: bumblebee queens learn better than workers

Species’ cognitive traits are shaped by their ecology, and even within a species, cognition can reflect the behavioural requirements of individuals with different roles. Social insects have a number of discrete roles (castes) within a colony and thus offer a useful system to determine how ecological requirements shape cognition. Bumblebee queens are a critical point in the lifecycle of their colony, since its future success is reliant on a single individual''s ability to learn about floral stimuli while finding a suitable nest site; thus, one might expect particularly adept learning capabilities at this stage. I compared wild Bombus vosnesenskii queens and workers on their ability to learn a colour association and found that queens performed better than workers. In addition, queens of another species, B. insularis, a cuckoo species with a different lifecycle but similar requirements at this stage, performed equally well as the non-parasitic queens. To control for differences in foraging experience, I then repeated this comparison with laboratory-based B. impatiens and found that unmated queens performed better than workers. These results add to the body of work on how ecology shapes cognition and opens the door to further research in comparative cognition using wild bees.     

Lethal and sublethal effects of the naturally derived insecticide spinosad on parasitoids of Spodoptera frugiperda (Lepidoptera: Noctuidae)

Laboratory studies were performed on the lethal and sublethal effects of spinosad on three important species of parasitoids attacking Spodoptera frugiperda (J.E. Smith) in Mexico. Reproduction of the braconid Chelonus insularis (Cresson), on treated egg masses was completely eliminated at 200 parts per million (ppm) and reduced by ∼70% at 20 ppm compared to the controls. Adult C. insularis did not avoid contact with residues on maize (200 ppm), but suffered a 7-day reduction in longevity after contact with residues. Initial toxicity of spinosad applied to a natural host of S. frugiperda was concentration dependent and resulted in 23 to 100% mortality of the eulophid Euplectrus plathypenae Howard at 25 to 200 ppm, respectively. The survival of Eu. plathypenae was initially reduced, especially in males, following contact with field weathered residues on maize (200 ppm). However, survival of both sexes rapidly returned to control values on foliage sampled after rainfall. A similar effect was observed in the mortality response of female Eu. plathypenae exposed to residues on sorghum. The ichneumonid Eiphosoma vitticolle Cresson did not avoid reproduction in S. frugiperda larvae that were externally contaminated with 200 ppm spinosad, although all spinosad-treated hosts died before the parasitoid progeny could develop. We use these results to predict the impact of spinosad applications on the foraging and reproduction of these parasitoids in the field. Such predictions require validation by field studies.     

Opposite effects of cooling on twitch contractions of skeletal muscle isolated from tropical toads (Leptodactylidae) and northern frogs (Ranidae)

Cooling increases the twitch force of frog skeletal muscle (Rana temporaria; Rana pipiens), but decreases the twitch force of tropical toad muscle (Leptodactylus insularis). Action potentials and intramembranous charge movement in frog and toad fibers were slowed identically by cooling. Cooling increased the integral of twitch Ca²⁺ detected by aequorin in frog fibers (1.4-fold), while also decreasing the peak and slowing the rate of decay. Conversely, cooling decreased the integral (0.6-fold) and the peak of twitch Ca²⁺ in toad fibers, without affecting the rate of decay. The difference in entire Ca²⁺ transients may account for cold-induced twitch potentiation in frogs and twitch paralysis in toads. In sustained contractions of toad fibers, cooling markedly decreased maximum force caused by: (i) tetanic stimulation, (ii) two-microelectrode voltage clamp steps, (iii) high [K⁺], or (iv) caffeine. Maximum force in sustained contractions was decreased moderately by cooling frog fibers. Rapid rewarming and simultaneous removal of high [K⁺] or caffeine during a sustained contraction, caused toad muscle force to rise towards the value corresponding to the warm temperature. This did not occur after removing high [K⁺] or caffeine from toad fibers kept in the cold. Transmission electron micrographs showed no relevant structural differences. Parvalbumins are thought to promote relaxation of frog muscle in the cold. The unique parvalbumin isoforms in toad muscle apparently lack this property. Accepted: 27 August 1998     

Population genetic structure of two primary parasitoids of Spodoptera frugiperda (Lepidoptera), Chelonus insularis and Campoletis sonorensis (Hymenoptera): to what extent is the host plant important?

Plant chemistry can strongly influence interactions between herbivores and their natural enemies, either by providing volatile compounds that serve as foraging cues for parasitoids or predators, or by affecting the quality of herbivores as hosts or prey. Through these effects plants may influence parasitoid population genetic structure. We tested for a possible specialization on specific crop plants in Chelonus insularis and Campoletis sonorensis, two primary parasitoids of the fall armyworm, Spodoptera frugiperda. Throughout Mexico, S. frugiperda larvae were collected from their main host plants, maize and sorghum and parasitoids that emerged from the larvae were used for subsequent comparison by molecular analysis. Genetic variation at eight and 11 microsatellites were respectively assayed for C. insularis and C. sonorensis to examine isolation by distance, host plant and regional effects. Kinship analyses were also performed to assess female migration among host‐plants. The analyses showed considerable within population variation and revealed a significant regional effect. No effect of host plant on population structure of either of the two parasitoid species was found. Isolation by distance was observed at the individual level, but not at the population level. Kinship analyses revealed significantly more genetically related—or kin—individuals on the same plant species than on different plant species, suggesting that locally, mothers preferentially stay on the same plant species. Although the standard population genetics parameters showed no effect of plant species on population structure, the kinship analyses revealed that mothers exhibit plant species fidelity, which may speed up divergence if adaptation were to occur.