Establishing and characterising a new cell line from Calliphora vicina (diptera: calliphoridae) fly embryonic tissues

Insect cell lines represent a promising and expanding field as they have several research applications including biotechnology, virology, immunity, toxicology, cell signalling mechanisms and evolution. They constitute a powerful tool having a direct impact on human and veterinary medicine and agriculture. Although more than 1000 cell lines have currently been established from various insect species, Calliphora vicina-derived fly cell lines are lacking. This study was aimed at establishing a new C. vicina embryonic tissue-derived cell line. Adult flies were collected and embryonated eggs were mechanically homogenised and seeded in four types of culture media (L15, Grace's insect medium, Grace's/L15 and DMEM). Cell growth and morphological characteristics were recorded and cytogenetic and molecular patterns were determined. The CV-062020-PPB cell line was established and was shown to have optimal growth in Grace's/L15 medium. CV-062020-PPB cell monolayers that had been sub-cultured over 16 times consisted of firmly adhering cells having different morphologies; a fibroblast-like shape dominated and the karyotype had a 12-chromosome diploid number. RAPD-PCR analysis of the CV-062020-PPB cell line revealed a high similarity index and strong intraspecific relationship with C. vicina adult flies and a weaker relationship with the Lutzomyia longipalpis-derived cell line (Lulo). The CV-062020-PPB cell line constitutes the first cell line obtained from C. vicina embryonic tissues and represents an important basic and applied research tool.

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A new C. vicina embryonic tissue-derived cell line is here reported.

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Fibroblast-like cells were predominant.

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The cell-line karyotype was 2n = 12 diploid chromosomes.

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The DNA profile enabled discriminating its molecular identity.

Axenic interspecies and intraclonal hybrid formation in Leishmania: Successful crossings between visceral and cutaneous strains

Diseases caused by trypanosomatids are serious public health concerns in low-income endemic countries. Leishmaniasis is presented in two main clinical forms, visceral leishmaniasis-caused by L. infantum and L. donovani-and cutaneous leishmaniasis-caused by many species, including L. major, L. tropica and L. braziliensis. As for certain other trypanosomatids, sexual reproduction has been confirmed in these parasites, and formation of hybrids can contribute to virulence, drug resistance or adaptation to the host immune system. In the present work, the capability of intraclonal and interspecies genetic exchange has been investigated using three parental strains: L. donovani, L. tropica and L. major, which have been engineered to express different fluorescent proteins and antibiotic resistance markers in order to facilitate the phenotypic selection of hybrid parasites after mating events. Stationary and exponential-phase promastigotes of each species were used, in in vitro experiments, some of them containing LULO cells (an embryonic cell line derived from Lutzomyia longipalpis). Several intraclonal hybrids were obtained with L. tropica as crossing progenitor, but not with L. donovani or L. major. In interspecies crossings, three L. donovani x L. major hybrids and two L. donovani x L. tropica hybrids were isolated, thereby demonstrating the feasibility to obtain in vitro hybrids of parental lines causing different tropism of leishmaniasis. Ploidy analysis revealed an increase in DNA content in all hybrids compared to the parental strains, and nuclear analysis showed that interspecies hybrids are complete hybrids, i.e. each of them showing at least one chromosomal set from each parental. Regarding kDNA inheritance, discrepancies were observed between maxi and minicircle heritage. Finally, phenotypic studies showed either intermediate phenotypes in terms of growth profiles, or a decreased in vitro infection capacity compared to the parental cells. To the best of our knowledge, this is the first time that in vitro interspecies outcrossing has been demonstrated between Leishmania species with different tropism, thus contributing to shed light on the mechanisms underlying sexual reproduction in these parasites.

Characterising four Sarconesiopsis magellanica (Diptera: Calliphoridae) larval fat body-derived antimicrobial peptides

BACKGROUND

The inappropriate use of antibiotics has led to the accelerated growth of resistance to antibiotics. The search for new therapeutic strategies (i.e., antimicrobial peptides-AMPs) has thus become a pressing need.

OBJECTIVE

Characterising and evaluating Sarconesiopsis magellanica larval fat body-derived AMPs.

METHODS

Fat body extracts were analysed by reversed-phase high-performance liquid chromatography (RP-HPLC); mass spectrometry was used for characterising the primary structure of the AMPs so found. ProtParam (Expasy) was used for analysing the AMPs' physico-chemical properties. Synthetic AMPs' antibacterial activity was evaluated.

FINDINGS

Four new AMPs were obtained and called sarconesin III, IV, V and VI. Sarconesin III had an α-helix structure and sarconesins IV, V and VI had linear formations. Oligomer prediction highlighted peptide-peptide interactions, suggesting that sarconesins III, V and VI could form self-aggregations when in contact with the microbial membrane. AMPs synthesised from their native molecules' sequences had potent activity against Gram-positive bacteria and, to a lesser extent, against Gram-negative and drug-resistant bacteria. Sarconesin VI was the most efficient AMP. None of the four synthetic AMPs had a cytotoxic effect.

MAIN CONCLUSIONS

S. magellanica larval fat body-derived antimicrobial peptides are an important source of AMPs and could be used in different antimicrobial therapies and overcoming bacterial resistance.

Sarconesin II, a New Antimicrobial Peptide Isolated from Sarconesiopsis magellanica Excretions and Secretions

Antibiotic resistance is at dangerous levels and increasing worldwide. The search for new antimicrobial drugs to counteract this problem is a priority for health institutions and organizations, both globally and in individual countries. Sarconesiopsis magellanica blowfly larval excretions and secretions (ES) are an important source for isolating antimicrobial peptides (AMPs). This study aims to identify and characterize a new S. magellanica AMP. RP-HPLC was used to fractionate ES, using C18 columns, and their antimicrobial activity was evaluated. The peptide sequence of the fraction collected at 43.7 min was determined by mass spectrometry (MS). Fluorescence and electronic microscopy were used to evaluate the mechanism of action. Toxicity was tested on HeLa cells and human erythrocytes; physicochemical properties were evaluated. The molecule in the ES was characterized as sarconesin II and it showed activity against Gram-negative (Escherichia coli MG1655, Pseudomonas aeruginosa ATCC 27853, P. aeruginosa PA14) and Gram-positive (Staphylococcus aureus ATCC 29213, Micrococcus luteus A270) bacteria. The lowest minimum inhibitory concentration obtained was 1.9 μM for M. luteus A270; the AMP had no toxicity in any cells tested here and its action in bacterial membrane and DNA was confirmed. Sarconesin II was documented as a conserved domain of the ATP synthase protein belonging to the Fli-1 superfamily. The data reported here indicated that peptides could be alternative therapeutic candidates for use in infections against Gram-negative and Gram-positive bacteria and eventually as a new resource of compounds for combating multidrug-resistant bacteria.

Sarconesin: Sarconesiopsis magellanica Blowfly Larval Excretions and Secretions With Antibacterial Properties

Larval therapy (LT) is an alternative treatment for healing chronic wounds; its action is based on debridement, the removal of bacteria, and stimulating granulation tissue. The most important mechanism when using LT for combating infection depends on larval excretions and secretions (ES). Larvae are protected against infection by a spectrum of antimicrobial peptides (AMPs); special interest in AMPs has also risen regarding understanding their role in wound healing since they degrade necrotic tissue and kill different bacteria during LT. Sarconesiopsis magellanica (Diptera: Calliphoridae) is a promising medically-important necrophagous fly. This article reports a small AMP being isolated from S. magellanica ES products for the first time; these products were obtained from third-instar larvae taken from a previously-established colony. ES were fractionated by RP-HPLC using C18 columns for the first analysis; the products were then lyophilised and their antimicrobial activity was characterized by incubation with different bacterial strains. These fractions' primary sequences were determined by mass spectrometry and de novo sequencing; five AMPs were obtained, the Sarconesin fraction was characterized and antibacterial activity was tested in different concentrations with minimum inhibitory concentrations starting at 1.2 μM. Potent inhibitory activity was shown against Gram-negative (Escherichia coli D31, E. coli DH5α, Salmonella enterica ATCC 13314, Pseudomonas aeruginosa 27853) and Gram-positive (Staphylococcus aureus ATCC 29213, S. epidermidis ATCC 12228, Micrococcus luteus A270) bacteria. Sarconesin has a significant similarity with Rho-family GTPases which are important in organelle development, cytoskeletal dynamics, cell movement, and wound repair. The data reported here indicated that Sarconesin could be an alternative candidate for use in therapeutics against Gram-negative and Gram-positive bacterial infections. Our study describes one peptide responsible for antibacterial activity when LT is being used. The results shown here support carrying out further experiments aimed at validating S. magellanica AMPs as novel resources for combating antibacterial resistance.

Evaluating the Biological Cycle and Reproductive and Population Parameters of Calliphora vicina (Diptera: Calliphoridae) Reared on Three Different Diets

This work was aimed at evaluating Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae) life cycle, life tables, and reproductive and population parameters. This species is a necrophagous, synanthropic, cosmopolitan fly with broad distribution in the Neotropical region. Six successive generations from adult specimens collected in Bogotá, Colombia, were analyzed in laboratory conditions. The fly's life cycle was evaluated, using a natural diet of pig's liver (L) and two artificial diets-milk powder and egg (ME) and powdered liver (PL). The species' longest life cycle duration (in days), from egg to pupa, was obtained with the ME diet (24.6 ± 6.7) whereas the lowest value was recorded with the L diet (18.8  ±  3.6). Female adult forms achieved high longevity values, this being highest in ME (102.8  ±  3.6). The most efficient diets (L and ME) led to the following average reproductive and population values: 226.2 and 465.4 net reproductive rate (Ro), 22.2 and 47.1 cohort generation time (Tc), 0.24 and 0.13 intrinsic population growth rate (r_m), and 1.27 and 1.13 finite rate of increase (λ). The set of results (in terms of relatively high average values concerning the biological characteristics analyzed) showed the species' adaptability to the environmental and nutritional conditions established in a laboratory setting, thereby enabling their colonization.

The effects of Sarconesiopsis magellanica larvae (Diptera: Calliphoridae) excretions and secretions on fibroblasts

Sarconesiopsis magellanica is a necrophagous blowfly which is relevant in both forensic and medical sciences. Previous studies regarding this species have led to understanding life-cycle, population and reproduction parameters, as well as identifying and characterising proteolytic enzymes derived from larval excretions and secretions (ES). As other studies have shown that ES proteolytic activity plays a significant role in wound healing and fibroblasts play a relevant role in granulation tissue formation during such healing, the present study was aimed at analysing the biological effect of S. magellanica larval ES on fibroblasts. ES were obtained from third-instar larvae and added to fibroblast cells at three concentrations (10, 5 and 1 μg/mL) to evaluate their behaviour. MTT assays were used for analysing cell proliferation and viability, whilst cell adhesion was measured by optical density with 10% SDS. Fibroblast migration and morphology was recorded by microscopic observation. ES did not affect fibroblast viability and induced an increase in cell proliferation; cell adhesion became reduced, whilst cell migration through extracellular matrix increased. ES also induced a decreased cell surface and morphological alterations. Changes in all the above-mentioned parameters were reduced when ES were incubated at 60 °C, probably due to protease denaturation. These results suggested that the proteases contained in S. magellanica larval ES contributed towards granulation tissue formation, increased cell migration and promoted cell proliferation. All these data support carrying out further experiments aimed at validating S. magellanica usefulness in larval therapy.

Analysis of the genetic variability and structure of Ochlerotatus taeniorhynchus (Diptera: Culicidae) populations from the Colombian Atlantic coast on the basis of random amplified polymorphic DNA markers

Ochlerotatus taeniorhynchus (Diptera: Culicidae) is a mosquito, which is an efficient vector of the virus causing epidemic-epizootic Venezuelan equine encephalitis in Colombia. This study used 9 random amplified polymorphic DNA (RAPD) markers to analyze the mosquito's genetic variability and genetic structure of 122 specimens in 7 populations from the Colombian Atlantic coast. Assuming that all loci were in Hardy-Weinberg equilibrium, diversity statistics and analyses were performed. The average number of amplified fragments for each primer was 8.3, and the size of these fragments ranged from 350 to 3600 bp. The expected average heterozygosity was 0.358 ± 0.103. The genetic heterogeneity among the populations studied was small (GST = 0.05 ± 0.01); meanwhile, the gene flow estimates (Nm = 7.32 ± 1.35) were high. In an identical way, the Nei's genetic distances obtained yielded very small values amongst the populations that were studied in this Colombian region. Furthermore, a spatial autocorrelation analysis with Moran's I index revealed a very weak, or inexistent, spatial genetic structure among these populations. The comparison of these results with those performed for other markers (isoenzymes and microsatellites) in populations of this same mosquito from the Colombian Atlantic coast was discussed. The results of our RAPD analysis showed scarce genetic differentiation among the mosquito populations on the Colombian Atlantic coast, which was probably determined by high gene flow levels.

Proteolytic activity regarding Sarconesiopsis magellanica (Diptera: Calliphoridae) larval excretions and secretions

Sarconesiopsis magellanica (Diptera: Calliphoridae) is a medically important necrophagous fly which is used for establishing the post-mortem interval. Diptera maggots release proteolytic enzymes contained in larval excretion and secretion (ES) products playing a key role in digestion. Special interest in proteolytic enzymes has also been aroused regarding understanding their role in wound healing since they degrade necrotic tissue during larval therapy. This study was thus aimed at identifying and characterising S. magellanica proteolytic enzyme ES products for the first time. These products were obtained from first-, second- and third-instar larvae taken from a previously-established colony. ES proteins were separated by SDS-PAGE and their proteolytic activity was characterised by zymograms and inhibition assays involving BAPNA (Nα-benzoyl-dl-Arg-p-nitroanilide) and SAPNA substrates, using synthetic inhibitors. The protein profile ranged from ∼69kDa to ∼23kDa; several of them coincided with the Lucilia sericata ES protein profile. Serine-protease hydrolysis activity (measured by zymogram) was confirmed when a ∼25kDa band disappeared upon ES incubation with PMSF inhibitor at pH 7.8. Analysis of larval ES proteolytic activity on BAPNA and SAPNA substrates (determined by using TLCK and TPCK specific inhibitors) suggested a greater amount of trypsin-like protease. These results support the need for further experiments aimed at validating S. magellanica use in larval therapy.

Sarconesiopsis magellanica (Diptera: Calliphoridae) life-cycle, reproductive and population parameters using different diets under laboratory conditions

Sarconesiopsis magellanica is a forensically relevant necrophagous blowfly that can aid in determining the post-mortem interval (PMI) as it is the first to colonise decomposing corpses. The blowfly has been reported in several South-American countries including Colombia, in high-altitude regions ranging from 1200 to 3100 m above sea level. The present study reports this blowfly's life cycle and an analysis of its reproductive and population parameters under laboratory conditions for the first time. Six successive generations of flies were produced with an average of 65.38% adults emerging with respect to the total number of puparia. The shortest life cycle from egg to adult emergence was found in individuals fed on a lyophilised liver (LL) diet, while the longest one was found in individuals fed with an egg-powdered milk (E-PM) diet; intermediate values were found when the pig liver (PL) diet was tested. The greatest adult longevity was achieved when the PL diet was used, the LL diet giving the shortest. The population parameters based on the horizontal life table were: net reproductive rate (Ro)=447.752±9.9, mean generational time (Tc)=18.18±0.38, natural population increase rate (r(m))=0.145 and finite population increase rate (λ)=1.398. This blowfly colony represents a valuable asset for both basic and applied studies. Members of the S. magellanica colony so established were used for analysing the life-cycle, reproductive and population parameters, and further medical and forensic application studies are currently underway.

Establishment and characterization of an embryonic cell line from Sarconesiopsis magellanica

Sarconesiopsis magellanica (Le Guillou) (Diptera: Calliphoridae) is a necrophagous fly that is important in both human and veterinary medicines. This insect has been registered in Colombia as a biological indicator in estimating post-mortem interval. Insect cell cultures are an important biotechnological tool for basic and applied studies, and cell cultures derived from S. magellanica embryonic tissues are described in this study. S. magellanica embryonated eggs were taken for tissue explants. These were seeded in L-15, Grace/L-15, Eagle MEM, MM, VP12, MM/VP12, and Schneider culture media. The morphological, cytogenetic, biochemical, and molecular characteristics of the cell cultures were examined. Cell growth was achieved in the L15, Grace/L15, and Schneider culture media, and the confluent monolayers were obtained 8, 10, and 19 days after the embryonated eggs were explanted. However, the Schneider medium was the most efficient to develop the subcultures, and 21 passages have been maintained. The cell morphology of the primary cell cultures was initially heterogeneous, but in the confluent monolayer and in the subcultures there was greater cell morphology uniformity, fibroblastoid types being predominant. Cultured cells had a chromosomal number of 12, and the karyotypic complement consisted of five pairs of somatic chromosomes and one sexual pair. The cell culture isozyme patterns of S. magellanica coincided with adult samples from the same species. The molecular analysis, using RAPD-PCR, demonstrated the authentication of the cell cultures of this fly and their differentiation from other cultures derived from two sand flies species. This cell line is a new in vitro model that will be used in biomedical and biotechnological studies.

Participation of heparin binding proteins from the surface of Leishmania (Viannia) braziliensis promastigotes in the adhesion of parasites to Lutzomyia longipalpis cells (Lulo) in vitro

Background

Leishmania (V.) braziliensis is a causative agent of cutaneous leishmaniasis in Brazil. During the parasite life cycle, the promastigotes adhere to the gut of sandflies, to avoid being eliminated with the dejection. The Lulo cell line, derived from Lutzomyia longipalpis (Diptera: Psychodidae), is a suitable in vitro study model to understand the features of parasite adhesion. Here, we analyze the role of glycosaminoglycans (GAGs) from Lulo cells and proteins from the parasites in this event.

Methods

Flagellar (F_f) and membrane (M_f) fractions from promastigotes were obtained by differential centrifugation and the purity of fractions confirmed by western blot assays, using specific antibodies for cellular compartments. Heparin-binding proteins (HBP) were isolated from both fractions using a HiTrap-Heparin column. In addition, binding of promastigotes to Lulo cells or to a heparin-coated surface was assessed by inhibition assays or surface plasmon resonance (SPR) analysis.

Results

The success of promastigotes subcellular fractionation led to the obtainment of F_f and M_f proteins, both of which presented two main protein bands (65.0 and 55.0kDa) with affinity to heparin. The contribution of HBPs in the adherence of promastigotes to Lulo cells was assessed through competition assays, using HS or the purified HBPs fractions. All tested samples presented a measurable inhibition rate when compared to control adhesion rate (17 ± 2.0% of culture cells with adhered parasites): 30% (for HS 20μg/ml) and 16% (for HS 10μg/ml); HBP M_f (35.2% for 10μg/ml and 25.4% for 20μg/ml) and HBP F_f (10.0% for 10μg/ml and 31.4% for 20μg/ml). Additionally, to verify the presence of sulfated GAGs in Lulo cells surface and intracellular compartment, metabolic labeling with radioactive sulfate was performed, indicating the presence of an HS and chondroitin sulfate in both cell sections. The SPR analysis performed further confirmed the presence of GAGs ligands on L. (V.) braziliensis promastigote surfaces.

Conclusions

The data presented here point to evidences that HBPs present on the surface of L. (V.) braziliensis promastigotes participate in adhesion of these parasites to Lulo cells through HS participation.

Synanthropy of Calliphoridae and Sarcophagidae (Diptera) in Bogotá, Colombia

Calliphoridae and Sarcophagidae have medical and forensic importance. Species of these families are the first insects colonizing corpses and are, therefore, useful in establishing postmortem interval and as indicators in corpse transfer. The synanthropic index (SI) measures the relation of dipteran species with human settlements. Our main objective was to determine the synanthropic index of these families during the rainy and dry seasons in Bogotá. Captures were carried out using traps with baits (beef liver) in three zones (urban, rural, and forest areas). In the family Calliphoridae, the most abundant species were Calliphora vicina (Robineau-Desvoidy) with a sinanthropy index (SI) of +83.1, followed by Lucilia sericata (Meigen) (SI = +92.2) and Compsomyiops verena (Walker) (SI = +42.0). Calliphora nigribasis (Macquart) was not associated with human settlements, while Sarconesiopsis magellanica (Le Guillou) was present in the three zones and considered hemisynanthropic (SI = +19.0). Roraimomusca roraima (Townsend) was reported for the first time in Bogotá and was a non-synanthropic species (SI = -36.0). On the other hand, in Sarcophagidae, three species were collected: Ravinia rufipes (Twonsend), Ravinia colombiana (Lopes), and Boettcheria sp1, which were abundant in the rural and forest zones, the first having a dual characterization as synanthropic and hemisynanthropic, while the other two were hemisynanthropic. Our data showed differences in the association of Calliphoridae species with the three environments, whereas Sarcophagidae were distributed in locations with a lower human impact.

Lulo cell line derived from Lutzomyia longipalpis (Diptera: Psychodidae): a novel model to assay Leishmania spp. and vector interaction

Background

Leishmania (Vianna) braziliensis, Leishmania (Leishmania) amazonensis and Leishmania (Leishmania) chagasi are important parasites in the scenario of leishmaniasis in Brazil. During the life cycle of these parasites, the promastigote forms adhere to the midgut epithelial microvillii of phlebotomine insects to avoid being secreted along with digestive products. Lulo cells are a potential model that will help to understand the features of this adhesion phenomenon. Here, we analyze the interaction between Leishmania spp. promastigotes and Lulo cells in vitro, specifically focusing on adhesion events occurring between three Leishmania species and this cell line.

Methods

Confluent monolayers of Lulo cells were incubated with promastigotes and adhesion was assessed using both light microscopy and scanning electron microscopy.

Findings

The results indicate that species from the subgenera Leishmania and Viannia have great potential to adhere to Lulo cells. The highest adherence rate was observed for L. (L.) chagasi after 24 h of incubation with Lulo cells (27.3 ± 1.8% of cells with adhered promastigotes), followed by L. (L.) amazonensis (16.0 ± 0.7%) and L. (V.) braziliensis (3.0 ± 0.7%), both after 48 h. In the ultrastructural analysis, promastigote adherence was also assessed by scanning electron microscopy, showing that, for parasites from both subgenera, adhesion occurs by both the body and the flagellum. The interaction of Lulo cells with Leishmania (L.) chagasi showed the participation of cytoplasmic projections from the former closely associating the parasites with the cells.

Conclusions

We present evidence that Lulo cells can be useful in studies of insect-parasite interactions for Leishmania species.

Experimental infection of Leishmania (L.) chagasi in a cell line derived from Lutzomyia longipalpis (Diptera:Psychodidae)

The present work describes the in vitro infection of a cell line Lulo, derived from Lutzomyia longipalpis embryonic tissue, by Leishmania chagasi promastigotes. This infection process is compared with a parallel one developed using the J774 cell line. The L. chagasi MH/CO/84/CI-044B strain was used for experimental infection in two cell lines. The cells were seeded on glass coverslips in 24-well plates to reach a final number of 2 x 10(5) cells/well. Parasites were added to the adhered Lulo and J774 cells in a 10:1 ratio and were incubated at 28 and 37 masculineC respectively. After 2, 4, 6, 8, and 10 days post-infection, the cells were extensively washed with PBS, fixed with methanol, and stained with Giemsa. The number of internalized parasites was determined by counting at least 400 cultured cells on each coverslip. The results showed continuous interaction between L. chagasi promastigotes with the cell lines. Some ultrastructural characteristics of the amastigote forms were observed using transmission electron microscopy. The highest percentage of infection in Lulo cells was registered on day 6 post-infection (29.6%) and on day 4 in the J774 cells (51%). This work shows similarities and differences in the L. chagasi experimental infection process in the two cell lines. However, Lulo cells emerge as a new model to study the life-cycle of this parasite.

Colonization of Ochlerotatus taeniorhynchus from Riohacha, Colombia

The main objective of the present work was to establish and maintain a colony of Ochlerotatus taeniorhynchus, Riohacha strain, under laboratory conditions and to study its life cycle. The colony's insectary was established from adult male and female mosquitoes collected from peripheral neighborhoods of Riohacha, Colombia. Environmental conditions established in the insectary were 26.5 degrees C average temperature, 80% average relative humidity, and 12 h photoperiodicity. Eight continuous generations were taken into account for maintaining the mosquitoes and analyzing their life cycle. The male mosquito's average life cycle was 26.8 days. The female's cycle was 30.8 days. Analysis of each of the biological stages of development (mean days) produced the following results: egg incubation 4.55 +/- 0.291, larvae 8.28 +/- 0.499, pupae 1.32 +/- 0.215, adult male 12.65 +/- 5.920. and adult female 16.73 +/- 6.034. The Riohacha colony has been maintained for 32 generations in 31 months. Comparison of the Riohacha colony with the previously established Cartagena and Barranquilla colonies showed few differences in the duration of stages of the life cycle between strains.

Life tables and reproductive parameters of Lutzomyia spinicrassa (Diptera: Psychodidae) under laboratory conditions

Lutzomyia spinicrassa is a vector of Leishmania braziliensis in Colombia. This sand fly has a broad geographical distribution in Colombia and Venezuela and it is found mainly in coffee plantations. Baseline biological growth data of L. spinicrassa were obtained under experimental laboratory conditions. The development time from egg to adult ranged from 59 to 121 days, with 12.74 weeks in average. Based on cohorts of 100 females, horizontal life table was constructed. The following predictive parameters were obtained: net rate of reproduction (8.4 females per cohort female), generation time (12.74 weeks), intrinsic rate of population increase (0.17), and finite rate of population increment (1.18). The reproductive value for each class age of the cohort females was calculated. Vertical life tables were elaborated and mortality was described for the generation obtained of the field cohort. In addition, for two successive generations, additive variance and heritability for fecundity were estimated.

A new continuous cell line from the mosquito Psorophora confinnis (Diptera: Culicidae) and its susceptibility to infections with some arboviruses

A new cell line, PC-0199-BR, was established from embryonated eggs of the mosquito Psorophora confinnis. To date (September 2000) it has had 62 continuous passages. This is the first report of a cell line of mosquitoes belonging to the genus Psorophora. Cell growth initially was achieved in the MM/VP12 medium, supplemented with 20% fetal bovine serum; however, the subcultures were later adapted to Grace's medium with 10% fetal bovine serum. Cell morphology in the primary cultures was heterogeneous; but later in the established cell line, the predominant cell type was epithelioid. Cultured cells were predominantly diploid (2n=6); however, chromosome abnormalities were observed in a small proportion of the cells in later passages. C and G band patterns were also determined in the karyotype. The cell line isozyme profiles coincided with pupae and adult samples of the species taken from the same colony. A preliminary arbovirus susceptibility study for the cell line was undertaken. No evidence was observed of contamination of the cell line with bacteria, fungi or mycoplasma.

Brain cell karyotype of the phlebotomine sand fly Lutzomyia shannoni (Dyar) (Diptera: Psychodidae)

The brain cell karyotype of New World sand fly Lutzomyia shannoni was described. This species has four pairs of chromosomes, 2N=8, with one pair of heteromorphic chromosomes.

Establishment and characterization of a new continuous cell line from Lutzomyia longipalpis (Diptera: psychodidae) and its susceptibility to infections with arboviruses and Leishmania chagasi

Embryonic tissue explants of the sand fly Lutzomyia longipalpis (Lutz & Neiva 1912) the main vector of Leishmania chagasi (Cunha and Chagas), were used to obtain a continuous cell line (Lulo). The tissues were seeded in MM/VP12 medium and these were incubated at 28 masculineC. The first subculture was obtained 45 days after explanting and 96 passages have been made to date. Lulo is composed of epithelioid cells, showed a 0.04 generations/hour exponential growth rate and population doubling time at 24.7 h. The cell line isoenzymatic profiles were determined by using PGI, PGM, MPI and 6-PGDH systems, coinciding with patterns obtained from the same species and colony's pupae and adults. The species karyotype characteristics were recognized (2n = 8), in which pair 1 is subtelocentric and pairs 2, 3 and 4 are metacentric. Lulo was free from bacterial, fungal, mycoplasmic and viral infection. Susceptibility to five arbovirus was determined, the same as Lulo interaction with Leishmania promastigotes.

Establishment and characterization of a cell line from the mosquito Anopheles albimanus (Diptera: Culicidae)

A new cell line designated LSB-AA695BB, was established from embryos of the mosquito Anopheles albimanus. The primary culture was initiated in April, 1995, and the first passage was made 48 days later. Serial subcultures of the cells have been carried through 90 passage from Abril 1995 to February 1996. The cells were grown at 28 degrees C in MK/VP12 medium, supplemented with 20% fetal bovine serum: the pH tolerance ranged between 6.8 to 7.0. The cells have also been adapted to MM/VP12 medium under the same pH, temperature and serum concentration. The majority of the cells were a fibroblast-type. Isozyme characterization showed a pattern similar to that of An. albimanus pupae and adults but distinct from Ae. taeniorhynchus and Ae. albopictus (C6/36) mosquito cell lines. The culture was shown to be free of mycoplasma, bacteria and fungi. Microsporidia contamination of transovarial transmission was controlled with 6.0 micrograms/ml of albendazole.