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G Dimopoulos

Publications and source records attributed to G Dimopoulos.

At least 19 recordsLinked to original sources
PubMed2004

The repeatability of corticomotor threshold measurements.

Threshold (Th) is a neurophysiological parameter frequently used in TMS studies. The present study was designed to investigate the repeatability of the Th measurements by reexamining healthy subjects over various time points. Overall, 82 subjects (median age: 19 years, range: 12-65) entered the study. Following a baseline examination, there were six retest sessions: S0 (n = 8 hemispheres reexamined, mean interval x = 19 min), S1 (n = 34 hemispheres reexamined, mean interval x = 4 days), S2 (n = 32 hemispheres, x = 29 days), S3 (n = 30 hemispheres, x = 106 days), S4 (n = 30 hemispheres, x = 183 days) and S5 (n = 30 hemispheres, x = 1867 days). Stimulation was performed with a figure of eight coil and Th was defined at 1% steps. At baseline, controls had an MT of 41.1 +/- 8. Mean difference of MT from baseline was 0.62 on S0 (95% confidence interval (CI) of the difference: -1.04 to +2.29), 0.13 on S1 (95% CI: -1.2 to +1.5), -0.03 on S2 (95% CI: -1.1 to +1.06), -2.07 on S3 (95% CI: -4.33 to +0.19), 0.15 on S4 (95% CI: -0.98 to +1.28) and 0.87 on S5 (95% CI: -0.49 to +2.23). None of these differences were statistically significant (repeated measures ANOVA, P > 0.05). The upper limit of MT difference that an individual subject might have with a probability of 95% (measurement error) was 8. The repeatability of the method was found to be independent from the age of the subjects, the magnitude of threshold or the test-retest interval. The topography of corticomotor threshold was also investigated. Minimal threshold values were obtained from a restricted area of scalp sites that always included the fixed stimulation point of the current protocol. Therefore, using a fixed stimulation point is an adequate technique for measuring threshold. In conclusion, threshold is a stable parameter on an individual and group basis. These data quantify the repeatability of the method and may prove useful in the interpretation of findings during longitudinal studies.

Adolescent↗
PubMed2004

Potential risk factors for infection with Candida spp. in critically ill patients.

The incidence, risk factors and prognostic factors for candidal infection were determined in a prospective study of 280 infected patients. Thirty-one (11%) patients were infected with Candida spp., sub-divided into 18 (58%) with C. albicans, and 13 (42%) with non-albicans spp. (six C. glabrata, three C. parapsilosis, and one each of C. krusei, C. tropicalis, C. guilliermondii and C. lusitaniae). Infection with Candida spp. was always associated with concurrent bacterial infection. By univariate logistic regression analysis, the degree of morbidity and the duration of mechanical ventilation were independent predictive factors for death, but infection with Candida spp., was not. Factors associated with Candida spp. infection were the degree of morbidity, intensive care unit length of stay, alterations of immune response, and the number of medical devices involved. By multivariate logistic regression analysis, the only independent risk factor for candidal infection was intensive care unit length of stay.

Adult↗
PubMed2003

Disseminated aspergillosis in intensive care unit patients: an autopsy study.

Disseminated aspergillosis is an uncommon but frequently fatal disease in critically ill populations. With studies suggesting that the incidence of this disease is increasing, and with relatively few epidemiological data available in this population, we evaluated cases of disseminated aspergillosis identified at autopsy over a one-year period on a 31-bed mixed medico-surgical intensive care unit (ICU) of an academic university hospital. In 1999, there were 489 deaths out of 2984 ICU admissions, and 222 autopsies were performed. Post-mortem examination demonstrated disseminated aspergillosis involving non-contiguous organs in 6 (2.7%) autopsies and, of these, five patients (2.3% of total) had had chronic obstructive pulmonary disease (COPD) and had been treated with corticosteroids and mechanical ventilation for pulmonary infection. One patient also had granulocytopenia. In each patient, sputum and bronchoalveolar lavage (BAL) cultures had been positive for Aspergillus fumigatus after ICU admission but this was considered as colonization and the patients were given fluconazole for suspected candidal infection. In conclusion, COPD patients treated with corticosteroids and presenting with pulmonary infection should be considered at risk for disseminated aspergillosis. The rapidly fatal outcome after ICU admission suggests that colonization with Aspergillus can occur before ICU admission.

Adrenal Cortex Hormones↗
PubMed2002

Cloning and molecular characterization of two mosquito iron regulatory proteins.

Iron regulatory proteins (IRPs) control the synthesis of various proteins at the translational level by binding to iron responsive elements (IREs) in the mRNAs. Iron, infection, and stress can alter IRP/IRE binding activity. Insect messenger RNAs for ferritin and succinate dehydrogenase subunit b have IREs that are active translational control sites. We have cloned and sequenced cDNAs encoding proteins from the IRP1 family for the mosquitoes, Aedes aegypti and Anopheles gambiae. Both deduced amino acid sequences show substantial similarity to human IRP1 and Drosophila IRP1A and IRP1B, and all of the residues thought to be involved in aconitase activity and iron-sulfur cluster formation are conserved. Recombinant A. aegypti IRP1 binds to transcripts of the IREs of mosquito or human ferritin subunit mRNAs. No significant change in A. gambiae IRP1 messenger RNA could be detected during the various developmental stages of the life cycle, following iron loading by blood feeding, or after bacterial or parasitic infections. These data suggest that there is no change in gene transcription. Furthermore, bacterial challenge of A. gambiae cells did not change IRP1 protein levels. In contrast, IRP1 binding activity for the IRE was elevated following immune induction. These data show that changes in IRP1/IRE binding activity occur as part of the insect immune response.

Aedes↗
PubMed2001

Gambicin: a novel immune responsive antimicrobial peptide from the malaria vector Anopheles gambiae.

A novel mosquito antimicrobial peptide, gambicin, and the corresponding gene were isolated in parallel through differential display-PCR, an expressed sequence tag (EST) project, and characterization of an antimicrobial activity in a mosquito cell line by reverse-phase chromatography. The 616-bp gambicin ORF encodes an 81-residue protein that is processed and secreted as a 61-aa mature peptide containing eight cysteines engaged in four disulfide bridges. Gambicin lacks sequence homology with other known proteins. Like other Anopheles gambiae antimicrobial peptide genes, gambicin is induced by natural or experimental infection in the midgut, fatbody, and hemocyte-like cell lines. Within the midgut, gambicin is predominantly expressed in the anterior part. Both local and systemic gambicin expression is induced during early and late stages of natural malaria infection. In vitro experiments showed that the 6.8-kDa mature peptide can kill both Gram-positive and Gram-negative bacteria, has a morphogenic effect on a filamentous fungus, and is marginally lethal to Plasmodium berghei ookinetes. An oxidized form of gambicin isolated from the cell line medium was more active against bacteria than the nonoxidized form from the same medium.

Amino Acid Sequence↗
PubMed2001

P25 and P28 proteins of the malaria ookinete surface have multiple and partially redundant functions.

The ookinete surface proteins (P25 and P28) are proven antimalarial transmission-blocking vaccine targets, yet their biological functions are unknown. By using single (Sko) and double gene knock-out (Dko) Plasmodium berghei parasites, we show that P25 and P28 share multiple functions during ookinete/oocyst development. In the midgut of mosquitoes, the formation of ookinetes lacking both proteins (Dko parasites) is significantly inhibited due to decreased protection against lethal factors, including protease attack. In addition, Dko ookinetes have a much reduced capacity to traverse the midgut epithelium and to transform into the oocyst stage. P25 and P28 are partially redundant in these functions, since the efficiency of ookinete/oocyst development is only mildly compromised in parasites lacking either P25 or P28 (Sko parasites) compared with that of Dko parasites. The fact that Sko parasites are efficiently transmitted by the mosquito is a compelling reason for including both target antigens in transmission-blocking vaccines.

Animals↗
PubMed2001

Innate immune defense against malaria infection in the mosquito.

Anopheles gambiae, the most important vector of malaria, employs its innate immune system in the fight against Plasmodium. This can affect the propagative capacity of Plasmodium in the vector and, in some cases, leads to total refractoriness to the parasite. The components operating in the mosquito's innate immune system and their potential relevance to antimalarial responses are being systematically dissected.

Animals↗
PubMed2000

Anopheles gambiae pilot gene discovery project: identification of mosquito innate immunity genes from expressed sequence tags generated from immune-competent cell lines.

Together with AIDS and tuberculosis, malaria is at the top of the list of devastating infectious diseases. However, molecular genetic studies of its major vector, Anopheles gambiae, are still quite limited. We have conducted a pilot gene discovery project to accelerate progress in the molecular analysis of vector biology, with emphasis on the mosquito's antimalarial immune defense. A total of 5,925 expressed sequence tags were determined from normalized cDNA libraries derived from immune-responsive hemocyte-like cell lines. The 3,242 expressed sequence tag-containing cDNA clones were grouped into 2,380 clone clusters, potentially representing unique genes. Of these, 1,118 showed similarities to known genes from other organisms, but only 27 were identical to previously known mosquito genes. We identified 38 candidate genes, based on sequence similarity, that may be implicated in immune reactions including antimalarial defense; 19 of these were shown experimentally to be inducible by bacterial challenge, lending support to their proposed involvement in mosquito immunity.

Animals↗
PubMed2000

Cloning and analysis of a cecropin gene from the malaria vector mosquito, Anopheles gambiae.

Parasites of the genus Plasmodium are transmitted to mammalian hosts by anopheline mosquitoes. Within the insect vector, parasite growth and development are potentially limited by antimicrobial defence molecules. Here, we describe the isolation of cDNA and genomic clones encoding a cecropin antibacterial peptide from the malaria vector mosquito Anopheles gambiae. The locus was mapped to polytene division 1C of the X chromosome. Cecropin RNA was induced by infection with bacteria and Plasmodium. RNA levels varied in different body parts of the adult mosquito. During development, cecropin expression was limited to the early pupal stage. The peptide was purified from both adult mosquitoes and cell culture supernatants. Anopheles gambiae synthetic cecropins displayed activity against Gram-negative and Gram-positive bacteria, filamentous fungi and yeasts.

Amino Acid Sequence↗
PubMed1999

CTRP is essential for mosquito infection by malaria ookinetes.

The malaria parasite suffers severe population losses as it passes through its mosquito vector. Contributing factors are the essential but highly constrained developmental transitions that the parasite undergoes in the mosquito midgut, combined with the invasion of the midgut epithelium by the malaria ookinete (recently described as a principal elicitor of the innate immune response in the Plasmodium-infected insect). Little is known about the molecular organization of these midgut-stage parasites and their critical interactions with the blood meal and the mosquito vector. Elucidation of these molecules and interactions will open up new avenues for chemotherapeutic and immunological attack of parasite development. Here, using the rodent malaria parasite Plasmodium berghei, we identify and characterize the first microneme protein of the ookinete: circumsporozoite- and TRAP-related protein (CTRP). We show that transgenic parasites in which the CTRP gene is disrupted form ookinetes that have reduced motility, fail to invade the midgut epithelium, do not trigger the mosquito immune response, and do not develop further into oocysts. Thus, CTRP is the first molecule shown to be essential for ookinete infectivity and, consequently, mosquito transmission of malaria.

Animals↗
PubMed1999

A cell surface mucin specifically expressed in the midgut of the malaria mosquito Anopheles gambiae.

An invertebrate intestinal mucin gene, AgMuc1, was isolated from the malaria vector mosquito Anopheles gambiae. The predicted 122-residue protein consists of a central core of seven repeating TTTTVAP motifs flanked by hydrophobic N- and C-terminal domains. This structure is similar to that of mucins that coat the protozoan parasite Trypanosoma cruzi. Northern blot analysis indicated that the gene is expressed exclusively in the midgut of adult mosquitoes. A length polymorphism and in situ hybridization were used to genetically and cytogenetically map AgMuc1 to division 7A of the right arm of the second chromosome. The subcellular localization of the encoded protein in tissue culture cells was examined by using a baculovirus vector to express AgMuc1 protein tagged with the green fluorescent protein (GFP). The results indicated that this protein is found at the cell surface and that both hydrophobic domains are required for cell surface targeting. We propose that AgMuc1 is an abundant mucin-like protein that lines the surface of the midgut microvilli, potentially protecting the intestinal epithelium from the proteinase-rich environment of the gut lumen. An intriguing possibility is that, as an abundant surface protein, AgMuc1 may also interact with the malaria parasite during its invasion of the mosquito midgut.

Amino Acid Sequence↗
PubMed1999

A hemocyte-like cell line established from the malaria vector Anopheles gambiae expresses six prophenoloxidase genes.

Cell lines from the malaria vector Anopheles gambiae have been established as a tool for the study of the mosquito innate immune system in vitro. Here, we describe the first continuous insect cell line that produces prophenoloxidase (PPO). This cell line (4a-3B) expresses constitutively six PPO genes, three of which are novel (PPO4, PPO5, and PPO6). The PPO genes show distinct temporal expression profiles in the intact mosquito, spanning stages from the embryo to the adult in an overlapping manner. Transient induction of larva-specific PPO genes in blood-fed adult females suggests that the developmental hormone 20-hydroxyecdysone may be involved in PPO gene regulation. Indeed, exposure of 4a-3B cells to 20-hydroxyecdysone in culture results in induction of those PPO genes that are mainly expressed in early developmental stages, and repression of PPO5, which is preferentially expressed at the adult stage. The cell line shows bacteria-induced immune transcripts that encode defensin and Gram-negative bacteria-binding protein, but no induction of PPO transcripts. This cell line most likely derives from a hemocyte lineage, and represents an appropriate in vitro model for the study of the humoral and cellular immune defenses of A. gambiae.

Amino Acid Sequence↗
PubMed1999

Trapping cDNAs encoding secreted proteins from the salivary glands of the malaria vector Anopheles gambiae.

The signal sequence trap method was used to isolate cDNAs corresponding to proteins containing secretory leader peptides and whose genes are expressed specifically in the salivary glands of the malaria vector Anopheles gambiae. Fifteen unique cDNA fragments, ranging in size from 150 to 550 bp, were isolated and sequenced in a first round of immunoscreening in COS-7 cells. All but one of the cDNAs contained putative signal sequences at their 5' ends, suggesting that they were likely to encode secreted or transmembrane proteins. Expression analysis by reverse transcription-PCR showed that at least six cDNA fragments were expressed specifically in the salivary glands. Fragments showing a high degree of similarity to D7 and apyrase, two salivary gland-specific genes previously found in Aedes aegypti, were identified. Of interest, three different D7-related cDNAs that are likely to represent a new gene family were found in An. gambiae. Moreover, three salivary gland-specific cDNA fragments that do not show similarity to known proteins in the databases were identified, and the corresponding full length cDNAs were cloned and sequenced. RNA in situ hybridization to whole female salivary glands showed patterns of expression that overlap only in part those observed in the culicine mosquito A. aegypti.

Amino Acid Sequence↗
PubMed1999

How does Anopheles gambiae kill malaria parasites?

The malaria parasite's lifecycle in the mosquito vector Anopheles gambiae involves several translocations within and between tissues during which large parasite losses have been documented. Interestingly, during the critical transition stages of midgut invasion and relocation of sporozoites from the oocysts to the salivary glands the mosquito innate immune system is activated. These defense reactions could, at least partially, be responsible for the parasite killing in the mosquito. This important question is now being approached by the dissection of the mosquito innate immune system as well as genetic and genomic studies.

Animals↗
PubMed1999

Salivary gland-specific gene expression in the malaria vector Anopheles gambiae.

Molecular studies on the tissue-specific gene expression in the salivary glands of Anopheles gambiae may provide useful tools for the development of new strategies for the control of the most efficient malaria vector in the sub-Saharan Africa. We summarize here the results of a recent investigation focused on the isolation of secreted factors and putative receptors from the salivary glands of An. gambiae. Using the Signal Sequence Trap technique we have identified the first cDNAs specifically expressed in the An. gambiae salivary glands. Among these, four are exclusively expressed in female glands and encode factors presumably involved in blood-feeding, whereas two other cDNAs seem to be expressed both in male and in female glands and are likely implicated in sugar-feeding. Homologues of genes previously identified in the yellow fever mosquito Aedes aegypti, like the apyrase and D7, as well as novel salivary gland-specific cDNAs, were identified. The isolation and characterization of promoter sequences from the corresponding genes may prove useful for the expression of anti parasitic agents in the salivary glands of transgenic mosquitoes.

Amino Acid Sequence↗
PubMed1998

Malaria infection of the mosquito Anopheles gambiae activates immune-responsive genes during critical transition stages of the parasite life cycle.

Six gene markers have been used to map the progress of the innate immune response of the mosquito vector, Anopheles gambiae, upon infection by the malaria parasite, Plasmodium berghei. In addition to four previously reported genes, the set of markers included NOS (a nitric oxide synthase gene fragment) and ICHIT (a gene encoding two putative chitin-binding domains separated by a polythreonine-rich mucin region). In the midgut, a robust response occurs at 24 h post-infection, at a time when malaria ookinetes traverse the midgut epithelium, but subsides at later phases of malaria development. In contrast, the salivary glands show no significant response at 24 h, but are activated in a prolonged late phase when sporozoites are released from the midgut into the haemolymph and invade the glands, between 10 and 25 days after blood feeding. Furthermore, the abdomen of the mosquito minus the midgut shows significant activation of immune markers, with complex kinetics that are distinct from those of both midgut and salivary glands. The parasite evidently elicits immune responses in multiple tissues of the mosquito, two of which are epithelia that the parasite must traverse to complete its development. The mechanisms of these responses and their significance for malaria transmission are discussed.

Amino Acid Sequence↗
PubMed1997

Plasmodium activates the innate immune response of Anopheles gambiae mosquitoes.

Innate immune-related gene expression in the major disease vector mosquito Anopheles gambiae has been analyzed following infection by the malaria parasite, Plasmodium berghei. Substantially increased levels of mRNAs encoding the antibacterial peptide defensin and a putative Gram-negative bacteria-binding protein (GNBP) are observed 20-30 h after ingestion of an infected blood-meal, at a time which indicates that this induction is a response to parasite invasion of the midgut epithelium. The induction is dependent upon the ingestion of infective, sexual-stage parasites, and is not due to opportunistic co-penetration of resident gut micro-organisms into the hemocoel. The response is activated following infection both locally (in the midgut) and systemically (in remaining tissues, presumably fat body and/or hemocytes). The observation that Plasmodium can trigger a molecularly defined immune response in the vector constitutes an important advance in our understanding of parasite-vector interactions that are potentially involved in malaria transmission, and extends knowledge of the innate immune system of insects to encompass responses to protozoan parasites.

Acute-Phase Proteins↗