The influence of temperature and humidity on abundance and richness of Calliphoridae (Diptera)

The blowfly species are important components in necrophagous communities of the Neotropics. Besides being involved in the degradation of animal organic matter, they may serve as vectors for pathogens and parasites, and also cause primary and secondary myiasis. The occurrence pattern of these species is well defined, yet it is still not very clear which of these environmental factors determine the structure of the assemblies. This paper was developed to evaluate the influence of mean temperature and relative humidity variation in the abundance and richness of blowflies in the Brazilian southernmost state, Rio Grande do Sul, where temperature variation is well marked throughout the year. To evaluate this objective, WOT (Wind Oriented Trap) were installed with beef liver as bait in three environments for 10 consecutive days in each month between July 2003 and June 2004. A total of 13,860 flies were collected distributed among 16 species with a higher frequency of Lucilia eximia (Wiedemann, 1819) and Chrysomya albiceps (Wiedemann, 1819). The mean temperature and relative humidity influence the richness of blowflies, with greater richness and abundance in late spring and early summer, whereas abundance was only influenced by temperature. Each species responded differently with respect to these variables, where L. eximia is not influenced by any of the two abiotic factors, despite the high abundance presented. This paper presents the results of the sensitivity for the presence or absence of species of Calliphoridae and on the variation of the abundance of these species under regime temperature changes and relative humidity with implications for public health and animal management.

Cephalopoda as prey of juvenile Southern elephant seals at Isla 25 de Mayo/King George, South Shetland Islands

The aim of the present study was to enhance the knowledge of the feeding habits of the juvenile component of the population of Southern elephant seals [Mirounga leonina (Linnaeus, 1758)] from Isla 25 de Mayo, South Shetland Islands, age class whose diet information is scarce. A total of 60 individuals were stomach lavaged in the spring - summer seasons of three consecutive years (2003, 2004 and 2005) of which 53.3 % (n = 32) presented food remnants. The Antarctic glacial squid Psychroteuthis glacialis Thiele, 1921 was the dominant prey taxon in terms of frequency of occurrence (68.7%), numerical abundance (60.1%) and biomass (51.5%), contributing 84.1% to the total relative importance index. Other squid prey species of importance were Slosarczykovia circumantartica Lipinski, 2001 in terms of occurrence (37.5%) and numerical abundance (14%) and Moroteuthis knipovitchi Filippova, 1972 in terms of biomass (16%). All identified cephalopod prey taxa are distributed south of the Antarctic Polar Front, except for the squid Martialia hyadesi Rochebrune & Mabille, 1889 which has a circumpolar distribution associated to the Polar Frontal Zone. No significant differences in the sizes of P. glacialis preyed upon by elephant seals were found between sexes and years. However, significant interannual differences were found in the taxonomical composition of their diet. This would be associated with temporal changes in food availability at the foraging areas of seals, which in turn may have been influenced by changes in oceanographic conditions as a result of the El Niño Southern Oscillation (ENSO) phenomenon that occurred during part of the study period. Furthermore, a differential response of males and females to this temporal variation was observed, with the former being also associated to a predation on octopods. This would suggest a sexual segregation in foraging habits of this species from the early stages of its life cycle.

Diel vertical migration of predators (planktivorous fish larvae) and prey (zooplankton) in a tropical lagoon

ABSTRACT Based on the hypothesis that diel vertical migration (DVM) is a mechanism of predator avoidance, the objective of the present study was to test for the occurrence of DVM in planktivorous fish larvae of Hypophthalmus edentatus (Spix, 1829) (Siluriformes, Pimelodidae) and Plagioscion squamosissimus (Heckel, 1840) (Perciformes, Sciaenidae), and zooplankton (rotifers, cladocerans and copepods) in an isolated tropical lagoon in the floodplain of the Upper Paraná River, Brazil (region of Parque Nacional de Ilha Grande). We investigated spatial overlap between predators (planktivorous fish larvae) and prey (zooplankton), and tested which physical and chemical variables of the water are related to the DVM of the studied communities. We performed nocturnal (8:00 pm and 4:00 am) and diurnal sampling (8:00 am and 4:00 pm) in the limnetic region of the lagoon for six consecutive months, from October 2010 to March 2011, which comprises the reproductive period of the fish species analyzed. During the day the larvae tried to remain aggregated in the bottom of the lagoon, whereas at night they tried to disperse in the water column. Especially for cladocerans, the diel vertical migration is an important behavior to avoid predation larvae of H. edentatus and P. squamosissimus once decreased spatial overlap between secured and its potential predators, which corroborates the hypothesis that DVM is a mechanism of predator avoidance. Although significant correlations were observed between the abiotic factors and WMD of microcrustaceans at certain times of day, the effect of predation of fish larvae on zooplankton showed more important in this environment, because the small depth and isolation not allow great variation of abiotic factors seasonally and between strata the lagoon.

Assessing the performance of macroinvertebrate metrics in the Challhuaco-Ñireco System (Northern Patagonia, Argentina)

ABSTRACT Seven sites were examined in the Challhuaco-Ñireco system, located in the reserve of the Nahuel Huapi National Park, however part of the catchment is urbanized, being San Carlos de Bariloche (150,000 inhabitants) placed in the lower part of the basin. Physico-chemical variables were measured and benthic macroinvertebrates were collected during three consecutive years at seven sites from the headwater to the river outlet. Sites near the source of the river were characterised by Plecoptera, Ephemeroptera, Trichoptera and Diptera, whereas sites close to the river mouth were dominated by Diptera, Oligochaeta and Mollusca. Regarding functional feeding groups, collector-gatherers were dominant at all sites and this pattern was consistent among years. Ordination Analysis (RDA) revealed that species assemblages distribution responded to the climatic and topographic gradient (temperature and elevation), but also were associated with variables related to human impact (conductivity, nitrate and phosphate contents). Species assemblages at headwaters were mostly represented by sensitive insects, whereas tolerant taxa such as Tubificidae, Lumbriculidae, Chironomidae and crustacean Aegla sp. were dominant at urbanised sites. Regarding macroinvertebrate metrics employed, total richness, EPT taxa, Shannon diversity index and Biotic Monitoring Patagonian Stream index resulted fairly consistent and evidenced different levels of disturbances at the stream, meaning that this measures are suitable for evaluation of the status of Patagonian mountain streams.

Estudos sôbre o pneumococo: 4a. nota - Influência do pH do meio sôbre a formação da cápsula pelo pneumococo

One of the features of pneumococcus which has deserved the attention of investigators is the capsule. Since Pasteur, Chamberland and Roux (1881) several functions have been ascribed to it as well as peculiar properties. In the present paper, we take into consideration one only aspect of this problem; it is the relationship which there possibly may be between acidity of the culture medium and the power of capsule formation by pneumococcus. As it is known, this germ requires for its development 7.8 as an optimum pH, but maintains its biological activities down to 5.6. These variations do not take place without large alterations, particularly of the capsule, not only from the morphological but also from the chemical viewpoint. The diameter of the mucous envelopment of the pneumococcus decreases in proportion to the increase of acidity down to its complete extinction. This fact has been regarded by investigators as a biological feature inhe¬ring to the germ itself and as proceeding of self-defense. In an acid medium the existing capsule is destroyed and the germ does not produce it again; consequently, acidity inhibits the formation of the capsule. We tried to check how this phenomenon comes to pass and to elucidated it. As we know, the fundamental compound of the pneumococcus capsule is mucin. In the first place, we experimented the action of acidity on same in the following manner: Mucin extracted from bovine submaxillary gland is precipitated by HC1 at a determined concentration degree; the mucin dissolves again and precipi¬tates in function of this concentration. This property of mucin (solubility in acid medium) modifies a little the interpretation of the mechanism of disappearance of the capsule from the said germ in the culture medium. Indeed: The acidification of the medium consecutive to the growth of pneumococcus reduces the dimensions of the capsule until causing its com¬plete disappearance; but on transferring this strain to new optimum cultiva¬ting conditions the capsule appears again exhuberantly, at times as anteriorly, although with biased virulence. Linking these two facts we draw the following conclusions: Pneumo¬coccus does not lose its capacity of capsule formation in an acid medium; but mucin, whilst being produced, is entirely dissolved in this medium by the aid of acidity; we venture to state that, in spite of medium acidity, the capacity of capsule production is a constant feature of pneumococcus and that the disappearance of the capsule does not depend on the pneumococcus in itself when it produces smooth colonies, but on the chemical properties of mucin, mainly on its solubility in acid medium.

A rapid method for testing in vivo the susceptibility of different strains of Trypanosoma cruzi to active chemotherapeutic agents

A method is described which permits to determine in vivo an in a short period of time (4-6 hours) the sensitivity of T. cruzo strains to known active chemotherapeutic agents. By using resistant- and sensitive T. cruzi stains a fairly good correlation was observed between the results obtained with this rapid method (which detects activity against the circulating blood forms) and those obtained with long-term schedules which involve drug adminstration for at least 20 consecutive days and a prolonged period of assessment. This method may be used to characterize susceptibility to active drugs used clinically, provide infomation on the specific action against circulating trypomastigotes and screen active compounds. Differences in the natural susceptibility of Trypanosoma cruzi strains to active drugs have been already reported using different criteria, mostly demanding long-term study of the animal (Hauschka, 1949; Bock, Gonnert & Haberkorn, 1969; Brener, Costa & Chiari, 1976; Andrade & Figueira, 1977; Schlemper, 1982). In this paper we report a method which detects in 4-6 hours the effect of drugs on bloodstream forms in mice with established T. cruzi infections. The results obtained with this method show a fairly good correlation with those obtained by prolonged treatment schedules used to assess the action of drugs in experimental Chagas' disease and may be used to study the sensitivity of T. cruzi strains to active drugs.

Bionomia de mosquitos (Diptera: Culicidae) em áreas da Mata Atlântica no município de Itaguaí, estado do Rio de janeiro, Brasil: I. Frequência intra, peri e extradomiciliar

Along 24 consecutive months, from January 1984 to December 1986, mosquito captures were performed in a rural area of said municipality. Aiming to evaluate the comparative frequency of the mosquito species inside houses and in the immediate vicinity and far from houses, the captures were made in two types of domiciles - one permanently and the other only sporadically inhabited - as well as in surrounding woods. Variations in temperature, relative humidity and rainfall were locally recorded. A tendency for domiciliation became evident by the presence of Aedes scapularis in the human domiciles, mainly in those permantely inhabited. Culex quinquefasciatus showed to be adapted to live with humans also in rural areas, in which, in some instances, insecticides had to be used to keep in under control. Such observations, mainly in terms of Ae. scapularis, reinforce the possibility of those mosquitoes, under favourable conditions, becoming carries of arboviroses to humans in rural environments.

Toxoplasma gondii: a rapid method for the isolation of pure tachyzoites: preliminary characterization of its genome

A rapid and simple technique for the purification of Toxoplasma gondii tachyzoites was developed. Highly purified parasites were obtained from the peritoneal exudates of infected mice by means of two consecutive discontinous sucrose gradients run at low speed (10,000xg, 30 min). Parasites obtained by this method conserved its biological activity. Hybridizations tudies with DNA from healthy mice and from purified tachyzoites preparations demonstrated that Toxoplasma gondii tachyzoites DNA could be obtained with better than 90 per cents purity. Preliminary studies with DNA endonucleases showed the presence in the tachyzoites genome of highly repetitives sequences.

Activity of the artemether in experimental schistosomiasis mansoni

The action of the ether artemisinin (artemether) on Shistosoma mansoni in mice and the hansters experimentally infected with the LE strain was studied. In mice, the drugs showed high schistosomicidal activity using a single intramuscular dose of 100 mg/Kg/day. By the oral route, this dose showed a low activity. Mice treated with a single intramuscular dose of 200 mg/Kg/day, and examined 15 days after treatment, presented 100% alteration of the oogram; when examined 45 days after treatment, the oogram was normal. With doses of 100 mg/Kg/day, i.m., during 3 or 5 consecutive days, the death rate of mice was very high. Morphologic analysis of the worms collected by perfusion of mice treated with a single dose of 100 mg/Kg/day, i.m., detected a marked decrease in the length of male and female forms, degenerative alterations in the parenchyma and in the reproductive system of the females, with reduction of vitellinic material and in ovary volume; the intestinal contents presented a marked despigmentation. In the male worms signifcant alteration was not apparent by optical microscopy.

Intestinal protein absorption in malnourished mice with acute schistosomiasis mansoni

Intestinal protein absorption was studied in undernourished albino Swiss mice with acute schistosomiasis mansoni. Undernutrition was induced by feeding mice with the Regional Basic Diet (RBD) ingested by human populations in Northeast Brazil, an experimental model previously developed in our laboratory. Weaning mice were infected with 40 cercariae and compared to undernourished non-infected mice and/or to infected mice fed a balanced control diet. Apparent and True Protein Absorption Coefficients were determined by nitrogen balance during five consecutive days ending at the 63rd day of the trial (acute phase of murine schistosomiasis). Fecal metabolic nitrogen (FMN) was determined after administration of a non-protein diet and was also calculated through linear regression. Our results showed a reduced protein absorption in non-infected RBD-fed mice as compared to mice fed a casein control diet. Infection with Schistosoma mansoni had apparently no effect on intestinal protein absorption in well-nourished mice. However, infection seemed to interfere with protein absorption in under-nourished animals, since the lowest absorption ratios have been detected among RBD-fed infected mice. A brief discussion is made on the advantages of using the method of linear regression for the determination of FMN.

Schistosomicidal activity of alkylaminooctanethiosulfuric acids

The schistosomicidal activity of a new series of alkylaminooctanethiosulfuric acids was studied in white Swiss mice infected with the L.E. strain of Schistosoma mansoni (Belo Horizonte, MG, Brazil). In a preliminary screening of six compounds, two derivatives - 2-[(1-methylpropyl)amino]-1-octanethiosulfuric acid and 2-[(1-methylethyl)-amino]-1-octanethiosulfuric acid - given orally in doses of 300 mg/kg/day for five consecutive days, caused interruption of the oviposition and the hepatic shift of more than 90 of the worms. Both compounds caused a significant reduction in worm burden and, interestingly, the female schistosomes were more susceptible. With the therapeutic schedule of two doses of 800 mg/kg over a 20 day interval, the death of almost all the females and about 50 of the males was observed. Female worms recovered from treated mice showed scattered vitteline glands. Results of in vitro experiments against different developmental stages of the parasite revealed the induction of paralysis and damage to the tegument membrane. The drugs presented no toxic effects on the animals.

Immature stages of mosquitoes (Diptera: Culicidae) Collected during the autumn-winter period in Cordoba Province, Argentina

Eggs, immature mosquito collections were made at Cosquin, La Calera ( Chaco phytogeographic region), Villa Allende and Villa del Rosario (Espinal phytogeographic region) during April/September of two consecutive years 1989, 1990. Specific immature habitats in each locality were identified and sampled monthly. Eggs and/or immatures of Aedes albifasciatus, Ae. fluviatilis, Anopheles albitarsis, culex acharistus, Cx. apicinus, Cx. bidens, Cx. coronator, Cx. chidesteri, Cx. dolosus, Cx. maxi, Cx. quinquefasciatus, Cx. saltanensis, Psorophora ciliata and Uranotaenia lowii were collected. Three species (Cx. acharistus, Cx. dolosus and Cx. quinquefasciatus) were collected during the sampling period for all developmental stages. This suggests that immature of these species do not overwinter but continue to develop throughout the cold autumn and winter seasons.

Present development concerning antimalarial activity of phospholipid metabolism inhibitors with special reference to in vivo activity

The systematic screening of more than 250 molecules against Plasmodium falciparum in vitro has previously shown that interfering with phospholipid metabolism is lethal to the malaria parasite. These compounds act by impairing choline transport in infected erythrocytes, resulting in phosphatidylcholine de novo biosynthesis inhibition. A thorough study was carried out with the leader compound G25, whose in vitro IC50 is 0.6 nM. It was very specific to mature parasites (trophozoïtes) as determined in vitro with P. falciparum and in vivo with P. chabaudi -infected mice. This specificity corresponds to the most intense phase of phospholipid biosynthesis activity during the parasite cycle, thus corroborating the mechanism of action. The in vivo antimalarial activity (ED50) against P. chabaudi was 0.03 mg/kg, and a similar sensitivity was obtained with P. vinckei petteri, when the drug was intraperitoneally administered in a 4 day suppressive test. In contrast, P. berghei was revealed as less sensitive (3- to 20-fold, depending on the P. berghei-strain). This difference in activity could result either from the degree of synchronism of every strain, their invasion preference for mature or immature red blood cells or from an intrinsically lower sensitivity of the P. berghei strain to G25. Irrespective of the mode of administration, G25 had the same therapeutic index (lethal dose 50 (LD50)/ED50) but the dose to obtain antimalarial activity after oral treatment was 100-fold higher than after intraperitoneal (or subcutaneous) administration. This must be related to the low intestinal absorption of these kind of compounds. G25 succeeded to completely inhibiting parasitemia as high as 11.2% without any decrease in its therapeutic index when administered subcutaneously twice a day for at least 8 consecutive days to P. chabaudi -infected-rodent model. Transition to human preclinical investigations now requires a synthesis of molecules which would permit oral absorption.

Phenotypes of lung mononuclear phagocytes in HIV seronegative tuberculosis patients: evidence for new recruitment and cell activation

Mycobacterium tuberculosis preferentially resides in mononuclear phagocytes. The mechanisms by which mononuclear phagocytes keep M. tuberculosis in check or by which the microbe evades control to cause disease remain poorly understood. As an initial effort to delineate these mechanisms, we examined by immunostaining the phenotype of mononuclear phagocytes obtained from lungs of patients with active tuberculosis. From August 1994 to March 1995, consecutive patients who had an abnormal chest X-ray, no demostrable acid-fast bacilli in sputum specimens and required a diagnostic bronchoalveolar lavage (BAL) were enrolled. Of the 39 patients enrolled, 21 had microbiologically diagnosed tuberculosis. Thirteen of the 21 tuberculosis patients were either HIV seronegative (n = 12) or had no risk factor for HIV and constituted the tuberculosis group. For comparison, M. tuberculosis negative patients who had BAL samples taken during this time (n = 9) or normal healthy volunteers (n = 3) served as control group. Compared to the control group, the tuberculosis group had significantly higher proportion of cells expressing markers of young monocytes (UCHM1) and RFD7, a marker for phagocytic cells, and increased expression of HLA-DR, a marker of cell activation. In addition, tuberculosis group had significantly higher proportion of cells expressing dendritic cell marker (RFD1) and epithelioid cell marker (RFD9). These data suggest that despite recruitment of monocytes probably from the peripheral blood and local cell activation, host defense of the resident lung cells is insufficient to control M. tuberculosis.

Winter biology of Culex pipiens quinquefasciatus say, (Diptera: Culicidae) from Córdoba, Argentina

Adult cohorts and immature stages were kept under field conditions during the autumn and winter of three consecutive years. Survival, oviposition and development time from egg to adult were considered. The adult cohorts were studied under three experimental conditions: unfed cohorts, cohorts fed with sugar solution ansd cohorts fed with both sugar solution and blood (chicken). Female longevity showed significant differences among the three treatments. Females of unfed cohorts lived up to three weeks; females fed with sugar solution survived until six weeks, while those fed both with sugar and blood lived at most fourteen weeks; after the blood intake eggs were laid. In the immature stages, the highest relative mortality rates occurred during the egg and larval stages. Total pre-adult mortality varied between 59.09 and 89.71%. The developmental duration from egg to adult was between 43-62 days; there were no differences among results obtained for the three years.