Marina Vianna Braga

Neolignans from plants in northeastern Brazil (Lauraceae) with activity against Trypanosoma cruzi

Trypanosoma cruzi is the ethiological agent for Chagas disease in Latin America. This study aimed to test the trypanocidal effect of licarin A and burchellin isolated from plants in northeastern Brazil. These neolignans were tested on T. cruzi and on peritoneal macrophages, to evaluate drug toxicity. Epimastigote growth was inhibited in 45% with licarin A and 20% with burchellin with an IC(50)/96 h of 462.7 microM and 756 microM, respectively. Epimastigotes treated with licarin A presented swollen mitochondria and disorganized mitochondrial cristae, kDNA and Golgi complex. When treated with burchellin, they presented enormous autophagosomes and chromatin disorganization. Licarin A and burchellin were able to induce trypomastigote death with IC(50)/24 h of 960 microM and 520 microM, respectively. Although licarin A presented an IC(50) for trypomastigotes higher than for epimastigotes, both substances acted as therapeutic trypanocidal agents, because they were able to kill parasites without affecting macrophages. Due to our results, burchellin and licarin A need to be further analysed to observe if they may be used as alternative blood additive prophylaxis against Chagas disease, since it has been established that blood transfusion is an important mechanism in the transmission process.

Life Cycle and Reproductive Patterns of Triatoma rubrofasciata (De Geer, 1773) (Hemiptera: Reduviidae), under Laboratory Conditions

The life cycle and reproductive patterns of Triatoma rubrofasciata were studied along with laboratory conditions for the establishment of a prolific colony. The insects were divided into four groups: two of them were maintained at room temperature (20.5 degrees C to 33 degrees C and 85% +/- 5% of relative humidity), the other two in a climatic chamber (CC) (temperature: 29 degrees C, humidity: 80% +/- 5%). The groups were fed weekly or fortnightly on Swiss mice. The females from the group kept in the CC and fed weekly had longer life span, as well as a higher number of eggs, fertile eggs and hatchings; the group kept in the CC and fed fortnightly had a shorter life span for the 1st, 2nd and 3rd instars and a lower mortality rate for all instars. It was concluded that a constant high temperature (CC at 29 degrees C) is the most suitable condition for the maintenance of a colony of T. rubrofasciata regardless of the interval between repasts.

Cuticular hydrocarbons as a tool for the identification of insect species: puparial cases from Sarcophagidae.

The external surface of all insects is covered by a species-specific complex mixture of highly stable, very long chain cuticular hydrocarbons (CHCs). Gas chromatography coupled to mass spectrometry was used to identify CHCs from four species of Sarcophagidae, Peckia (Peckia) chrysostoma, Peckia (Pattonella) intermutans, Sarcophaga (Liopygia) ruficornis and Sarcodexia lambens. The identified CHCs were mostly a mixture of n-alkanes, monomethylalkanes and dimethylalkanes with linear chain lengths varying from 23 to 33 carbons. Only two alkenes were found in all four species. S. lambens had a composition of CHCs with linear chain lengths varying from C23 to C33, while the other three species linear chain lengths from 24 to 31 carbons. n-Heptacosane, n-nonacosane and 3-methylnonacosane, n-triacontane and n-hentriacontane occurred in all four species. The results show that these hydrocarbon profiles may be used for the taxonomic differentiation of insect species and are a useful additional tool for taxonomic classification, especially when only parts of the insect specimen are available.

Feeding and Defecation Patterns of Nymphs of Triatoma rubrofasciata (De Geer, 1773) (Hemiptera: Reduviidae), and its Potential Role as Vector for Trypanosoma cruzi

Although Triatoma rubrofasciata is occasion-ally found naturally infected by Trypanosoma cruzi(AR da Silva 1983 Trans R Soc Trop Med Hyg 77 :568-569, RP Brazil et al. 1985 Rev Soc Brasil MedTrop : 257-260) it is not considered an importantvector of Chagas disease. It is normally the vectorof Trypanosoma conorhini which infects Rattusrattus since this insect is in close association withthe rat. It is found mostly in port cities (H Lent & PWygodzinsky 1979 Bull Am Mus Nat Hist 163:125-520) and the knowledge on its biology is stillscarce.Aiming at understanding the role of this spe-cies in the transmission of Chagas disease, the feed-ing and defecation patterns of nymphs of each in-star were observed.The eggs and nymphs were separated from acolony maintained in the Laboratory of Biologyand Control of Vector Insects, Oswaldo Cruz In-stitute. As soon as the hatchings occurred, or 5 to10 days after molting, the nymphs were separatedand fed individually on Swiss mouse. The mousewas immobilized in a nylon mosquito net “sand-wich”, put in a wide glass container, and thenymphs were allowed to search for the food sourcefor a maximum period of 2 hr. The following pa-rameters were observed for all instar nymphs: timespent to begin feeding, duration of feeding, num-ber of interruptions during feeding and number oftimes that the nymphs eliminated a dark excretaand a clear excreta during and soon after feeding.The data were statistically analyzed by the Kruskal-Wallis one-way test and the Chi-square test (SSiegel 1956 Nonparametric Statistics for the Be-havioral Sciences, McGraw-Hill, New York, 350pp).In all instars more than 70% of the nymphsspent less than 10 min to begin feeding after beingplaced in the glass container, although some ofthem, from 1st to 4th, have spent more than 20min. Among these, the major percentage occurredin the 2nd instar (20%) and the lesser in the 1st(7%). All 5th instar nymphs began feeding before20 min after being placed in the container. Withexception of the 3rd instar, approximately 60% ofthe nymphs from 1st, 2nd, and 4th instars and 90%from the 5th instar spent more than 15 min feed-ing. More than 50% of the nymphs from the 1st tothe 4th instar and 35% from 5th instar did not in-terrupt feeding.Comparing the results for all instars shown inTable I, the statistical analysis was significantlydifferent for the duration of feeding (H=20.5,P 0.05 andH=1.3, P>0.05, respectively). However, some dis-crepancies occurred. In the 2nd instar, one nymphspent 54 min to begin feeding and only 17 min tofeed and in the 3rd instar, a nymph spent 39 min tobegin and only 11 min to feed.Table II shows the percentages of nymphs thateliminated the dark and clear excreta during or soonafter feeding. The percentages of defecation dur-ing feeding were very low (maximum of 5% in the5th instar) and defecation soon after feeding on ornear the host were lower than 10% in all instars.However, approximately 90% of the nymphs from1st, 2nd and 3rd instars, 100% from 4th instar and80% from 5th instar eliminated the excreta far fromthe food source, a long time after having finishedfeeding. The nymphs more often eliminated a clearexcreta during or soon after feeding. The statisti-cal tests did not show any difference among theinstars (c

Effect of age on cuticular hydrocarbon profiles in adult Chrysomya putoria (Diptera: Calliphoridae)

A species-specific complex mixture of highly stable cuticular hydrocarbons (CHCs) covers the external surface of all insects. Components can be readily analyzed by gas chromatography coupled to mass spectrometry (GC-MS) to obtain a cuticular hydrocarbon profile, which may be used as an additional tool for the taxonomic differentiation of insect species and also for the determination of the age and sex of adult and immature forms. We used GC-MS to identify and quantify the CHCs of female and male Chrysomya putoria (Wiedemann, 1818) (Diptera: Calliphoridae) from one to five days old. CHCs ranged from C21 to C35 for females and from C21 to C37 in males. Major compounds were the same for both sexes and were 2-MeC28, C29:1, n-C29, 15-,13-MeC29, 2-MeC30, C31:1, n-C31 and 15-,13-MeC31. The relative abundance of each component, however, varied with age. Cluster Analysis using Bray-Curtis measure for abundance showed that cuticular hydrocarbon profiles are a strong and useful tool for the determination of age in adult C. putoria.

Efeitos de níveis de privação alimentar sobre a oogênese de Panstrongylus megistus

The effects of various levels of food deprivation on the oogenesis of P. megistus was studied. Immediately after the imaginal ecdysis, six groups (GI to GVI) of 15 couples each were formed. Each group was fed as follows: GI -- on days 5 and 25; G-II -- on days 5 and 35; GIII -- on days 5 and 45; GIV -- on day 20; GV -- on day 30; GVI -- on day 40 after the imaginal ecdysis. After the established fasting period, all groups were fed fortnightly. Fifteen couples were in the control group (CG), which was fed on the day 5 after the imaginal ecdysis and subsequently fortnightly. GI produced more eggs, matings and fertile eggs. GII had longer life spans, higher fecundity and hatchings. GIII had a shorter life span, low fecundity, fertility and hatchings. GVI presented the least favorable results for all parameters, except for the pre-oviposition period. The CG had the best results in all parameters when compared with all experimental groups.

Cuticular hydrocarbon profiles as a chemotaxonomic tool for three blowfly species (Diptera: Calliphoridae) of forensic interest

ABSTRACT Cuticular hydrocarbons (CHs) contain complex mixtures of components that cover the surface of all insects to restrict water loss, and in many species function in chemical communication. The complex mixtures have been used as a chemotaxonomic tool since the 1970s. The majority of CH components can be identified by gas chromatography-mass spectrometry (GC-MS), allowing hydrocarbon profiles to be used as chemotaxonomic characters, which can differentiate insect species, including cryptic species. The present study used GC-MS for the identification of CHs of males and females of three species of calliphorids: Cochliomyia macellaria (Fabricius), Hemilucilia segmentaria (Fabricius) and Lucilia cuprina (Wiedmann), A comparison of the chromatographic profiles from the three species allows them to be readily separated. Hydrocarbons identified from the three species contain 23 to 37 carbons and include n-alkanes, methyl-branched alkanes and alkenes. The most abundant compound for both sexes of C. macellaria was n-heptacosane, while for H. segmentaria it was 2-methyltriacontane; for L. cuprina, however, the most abundant compound was hentriacontene for females and nonacosene for males. The results obtained in this study are important for the establishment of a database to be used in chemotaxonomy of sanitarily and forensically important insects.