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A della Torre

Publications and source records attributed to A della Torre.

33 records · Page 2Linked to original sources
PubMed1997

Molecular identification of sympatric chromosomal forms of Anopheles gambiae and further evidence of their reproductive isolation.

Three chromosomal forms of Anopheles gambiae s.s., designated as Bamako, Mopti and Savanna, were studied for diagnostic PCR assays based on the analysis of the X-linked ribosomal DNA (rDNA). The study was performed on a 1.3 kb fragment containing part of the 28S coding region and part of the intergenic spacer region. The amplified material was cut with fourteen restriction enzymes to detect Restriction Fragment Length Polymorphisms (RFLPs). The enzymes Tru9I and HhaI produced patterns of DNA bands which differentiated Mopti from Savanna and Bamako; moreover, a distinct 'hybrid' pattern was recognized in the F1 female progeny from the cross of Mopti with either one of the other two chromosomal forms. The diagnostic significance of the PCR-RFLP assay was verified on 203 karyotyped females from field samples collected in two villages in Mali and one village in Burkina Faso. Agreement was observed between the chromosomal and the molecular identifications. No 'hybrid' molecular patterns were detected even among carriers of rare heterokaryotypes hypothetically produced by crosses between Mopti and Savanna. The results confirm previous observations indicating barriers to gene flow within An. gambiae s.s. and supporting the specific status of the taxonomic units proposed on cytogenetic ground.

Animals↗
PubMed1997

Selective introgression of paracentric inversions between two sibling species of the Anopheles gambiae complex.

The Anopheles gambiae complex includes the major vectors of malaria in sub-Saharan Africa where > 80% of all world-wide cases occur. These mosquitoes are characterized by chromosomal inversions associated to the speciation process and to intraspecific ecological and behavioral flexibility. It has been postulated that introgressive hybridization has selectively transferred inversions on the second chromosome between A. gambiae and A. arabiensis, the two most important vectors of malaria. Here we directly test this hypothesis with laboratory experiments in which hybrid populations were established and the fate of chromosomal inversions were followed. Consistent with the hypothesis, "foreign" X chromosomes were eliminated within two generations, while some "foreign" second chromosomes persisted for the duration of the experiments and, judging from the excess of heterozygotes established stable heterotic polymorphisms. Only those second chromosome inversions found naturally in the species could be introgressed.

Animals↗
PubMed1997

Advances in the identification of Dirofilaria repens and Dirofilaria immitis by a PCR-based approach.

The differential epidemiology of D. repens and D. immitis is still poorly understood due to the lack of a diagnostic method which would make possible the routine identification of these parasites as developing larvae either in the vector or in unsuitable hosts, including man. The PCR-based method here described allows: i) the unambiguous identification of mature and immature adult worms in bioptic material, of microfilariae in blood samples and of developing larvae in mosquito vectors; ii) the analysis of samples stored either dry or in various preservation media, with the exception of formalin. The high specificity and sensitivity of the diagnosis improve the perspectives for comparative epidemiological investigations on D. repens and D. immitis in areas where the two nematodes are sympatric.

Animals↗
PubMed1996

Identification and characterization of differentially expressed cDNAs of the vector mosquito, Anopheles gambiae.

The isolation and study of Anopheles gambiae genes that are differentially expressed in development, notably in tissues associated with the maturation and transmission of the malaria parasite, is important for the elucidation of basic molecular mechanisms underlying vector-parasite interactions. We have used the differential display technique to screen for mRNAs specifically expressed in adult males, females, and midgut tissues of blood-fed and unfed females. We also screened for mRNAs specifically induced upon bacterial infection of larval stage mosquitoes. We have characterized 19 distinct cDNAs, most of which show developmentally regulated expression specificity during the mosquito life cycle. The most interesting are six new sequences that are midgut-specific in the adult, three of which are also modulated by blood-feeding. The gut-specific sequences encode a maltase, a V-ATPase subunit, a GTP binding protein, two different lectins, and a nontrypsin serine protease. The latter sequence is also induced in larvae subjected to bacterial challenge. With the exception of a mitochondrial DNA fragment, the other 18 sequences constitute expressed genomic sequence tags, 4 of which have been mapped cytogenetically.

Amino Acid Sequence↗
PubMed1996

Integrated genetic map of Anopheles gambiae: use of RAPD polymorphisms for genetic, cytogenetic and STS landmarks.

Randomly amplified polymorphic DNA (RAPD) markers have been integrated in the genetic and cytogenetic maps of the malaria vector mosquito, Anopheles gambiae. Fifteen of these markers were mapped by recombination, relative to microsatellite markers that had been mapped previously. Thirty-four gel-purified RAPD bands were cloned and sequenced, generating sequence tagged sites (STSs) that can be used as entry points to the A. gambiae genome. Thirty one of these STSs were localized on nurse cell polytene chromosomes through their unique hybridization signal in in situ hybridization experiments. Five STSs map close to the breakpoints of polymorphic inversions, which are notable features of the Anopheles genome. The usefulness and limitations of this integrated mosquito map are discussed.

Animals↗
PubMed1996

Physical map of the malaria vector Anopheles gambiae.

Random cDNA clones, cosmid clones and RAPD polymorphic fragments have been localized by in situ hybridization to the ovarian nurse cell polytene chromosomes of the malaria vector Anopheles gambiae. We thus established 85 molecular markers for 110 sites within the whole A. gambiae polytene chromosome complement. The cDNA clones analyzed were isolated at random, and their exact localizations were determined by in situ hybridization. For 15 of the cDNA clones, a partial nucleotide sequence has been obtained; for nine of them sequence searches in the GenBank database revealed high degrees of similarity with published sequences. The cosmid clones analyzed were obtained as the result of screening with a few of the aforementioned cDNA clones of particular interest, or taken from a small set of randomly isolated cosmid clones. The RAPD clones are polymorphic fragments, potentially diagnostic for the various chromosomal forms of A. gambiae that are currently being analyzed.

Animals↗
PubMed1995

Constitutive and blood meal-induced trypsin genes in Anopheles gambiae.

Trypsin genes in Anopheles gambiae are arranged as a tightly clustered gene family consisting of seven related coding sequences, devoid of introns. The two blood meal-inducible members of this family, Antryp1 and Antryp2, were shown to play a crucial role in the breakdown of the blood meal constituents. The role of Antryp3,4,5,6, and Antryp7 in the process of blood meal digestion remains to be elucidated. We have examined the localization and the expression patterns of these trypsins as well as the functional interactions in blood meal digestion between trypsins and other gut-specific proteases. Northern blot and RT-PCR analysis indicated that the genes Antryp3,4,5,6, and Antryp7 are all constitutively expressed in unfed female mosquitoes. Soon after blood feeding the mRNA of these trypsin genes became undetectable and appeared again at the end of the gonotrophic cycle. The blood meal-inducible trypsin Antryp1 was also constitutively expressed at low level in the gut of adult female mosquitoes. This trypsin was the only member of this gene family to be expressed in the gut of male and female pupae. By using antisera that specifically recognized recombinant Antryp4 we were able to show that the corresponding protein in Anopheles is synthesized and stored in the gut epithelium of unfed females as zymogen. Secretion and activation of this trypsin was shown to occur in the midgut lumen immediately after fluid ingestion and independently of the protein content of the meal. Recombinant trypsins expressed in Escherichia coli, with the exception of Antryp5 and Antryp6, were able to activate in vitro recombinant A. gambiae chymotrypsinogen, thus suggesting that blood meal ingestion is able to trigger a cascade of events leading to the activation of several proteases.

Amino Acid Sequence↗
PubMed1995

Development of Dirofilaria and Setaria nematodes in Aedes albopictus.

The development of Dirofilaria repens, D immitis and Setaria labiatopapillosa up to L3 stage was documented in a laboratory colony of Aedes albopictus originating from specimens collected in Civitavecchia (Central Italy). The susceptibility of Ae albopictus and its plastic trophic habits, strongly suggest that this mosquito may contribute to the spreading of these nematodes in the country. It is particularly emphasized the danger for human health of an increased probability of transmission of Dirofilaria in urban areas.

Aedes↗
PubMed1994

Polymorphisms detected by random PCR distinguish between different chromosomal forms of Anopheles gambiae.

We have applied PCR amplification using random primers to distinguish between incipient species of the malaria vector Anopheles gambiae. Individuals belonging to three chromosomally characterized West African forms of this mosquito, which are important epidemiologically as they differ in vectorial capacity, were sampled both from laboratory stocks and from wild populations collected in three localities. The techniques used allowed for the unambiguous classification of the mosquitoes, providing a tool for rapid and efficient diagnosis, which previously relied on cytological examination of polytene chromosomes.

Africa, Western↗
PubMed1993

Members of a trypsin gene family in Anopheles gambiae are induced in the gut by blood meal.

Serine proteases are among the enzymes that play a crucial role during the digestion of the blood meal in the gut of mosquitoes. The identification of the corresponding genes would have important implications for the control of mosquitoes and mosquito-borne diseases. Analysis of the genomic organization of these genes may lead to the isolation of a gut-specific, inducible promoter for the expression of anti-parasitic agents in transgenic mosquitoes. Moreover, specific inhibitors could be designed on the basis of the structural properties of the enzymes. We report here on the identification of a trypsin gene family in Anopheles gambiae, the mosquito vector of malaria in Africa. Mosquito trypsin-related sequences were amplified by PCR using as template cDNA derived from RNA of blood fed mosquitoes. Cloning of the PCR product revealed two distinct sequences. Corresponding full-length cDNA clones were obtained and sequenced. Antryp1 and Antryp2 code for proteins of 274 and 277 amino acids respectively, showing 75% homology at the amino acid level. The deduced amino acid sequences clearly identify them as trypsins. Five additional trypsin sequences were found in overlapping genomic clones. The genes identified are tightly clustered within 11 kb and sequencing indicates that no introns are present. Northern and PCR analysis indicated that the transcription of both Antryp1 and Antryp2 is induced by blood feeding. Moreover, the Antryp1 protein was detected among the proteins of a midgut lysate of blood fed mosquitoes using antisera against recombinant Antryp1. In addition, the recombinant polypeptides derived from Antryp1 and Antryp2 expressed in Escherichia coli showed a strong proteolytic activity against different sets of blood proteins. We conclude that the products of Antryp1 and Antryp2 play an important role in the breakdown of the proteins during the digestion of the blood meal in the mosquito gut.

Amino Acid Sequence↗
PubMed1993

[Effect of metallic copper on the larva of Aedes albopictus: 1st laboratory data].

Laboratory experiments were carried out to test the larvicidal properties of metallic copper against Ae albopictus, a species which has spread in Italy during the last 3 years. The results show the strongest lethal effect on 1st stage larvae and support the use of copper as a simple, cheap and environmentally safe agent to control larval breeding of Ae albopictus in peridomestic containers.

Aedes↗
PubMed1993

Temporal and spatial expression of serine protease genes in Anopheles gambiae.

Serine proteases play a crucial role during the digestion of the blood meal in the mosquito gut. The isolation and the analysis of the genomic organisation of the corresponding genes may lead to the characterization of gut-specific, inducible promoters, suitable for the expression of anti-parasitic agents in the gut of transgenic mosquitoes. We report here on the identification of a trypsin and a chymotrypsin gene family of Anopheles gambiae. Following a blood meal, the transcription of all members of the two identified gene clusters, seven trypsin genes (Antryp1-7) and two chymotrypsin genes (Anchym1-2), is induced. Recombinant Antryp1 and Antryp2, expressed in E. coli, were both active in vitro against blood proteins. Moreover, mouse sera raised against Antryp1, Anchym1 and Anchym2 recognized the corresponding proteases among the proteins of a lysate prepared from dissected guts of An. gambiae mosquitoes.

Animals↗
PubMed1992

[Extension of the area of Aedes albopictus in Italy. 1st report of the species in central Italy].

A new infestation by Aedes albopictus was discovered in Civitavecchia, Central Italy, in October 1992. This follows previous records of the species in North Italy, where the first infestation was observed in 1990 in the city of Genoa. The present finding clearly indicates the capacity of Aedes albopictus to spread all over Italy and to become a permanent pest in Southern Europe. In spite of the expected embryonic diapause in October, larval breeding was observed in a fifteen-liter glass jar with a narrow neck, left outdoor.

Aedes↗
PubMed1991

Low-resolution genome map of the malaria mosquito Anopheles gambiae.

We have microdissected divisions of the Anopheles gambiae polytene chromosomes, digested the DNAs with a restriction enzyme, and PCR-amplified the DNA fragments to generate a set of pooled probes, each corresponding to approximately 2% of the mosquito genome. These divisional probes were shown to have high complexity. Except for those derived from near the centromeres, they hybridize specifically with their chromosomal sites of origin. Thus, they can be used to map cloned DNAs by a dot blot procedure, which is much more convenient than in situ hybridization to polytene chromosomes. We discuss additional potential uses of these probes, such as easier isolation of molecular markers and genes, including those that cross-hybridize with clones available from other insects. It is expected that the probes will substantially accelerate molecular genetic analysis of this most important malaria vector.

Animals↗