Biomedical subjects

J R David

Publications and source records attributed to J R David.

At least 73 records · Page 4Linked to original sources

PubMed1994

Genetics of a nonoptimal behavior: oviposition preference of Drosophila mauritiana for a toxic resource.

Among three sibling species of the D. melanogaster subgroup, two are generalists (D. simulans and D. mauritiana), while the third, D. sechellia, specializes on a single toxic resource, the fruit of Morinda citrifolia. D. sechellia, resistant to the toxics, prefers to oviposit on morinda; D. simulans, which is very sensitive, is strongly repelled. D. mauritiana exhibits an aberrant behavior since it prefers to lay its eggs on morinda, where its embryos are killed. Oviposition behavior, studied in parental species, F1 hybrids, and backcrosses, was mostly an additive genetical trait. Further investigations were made with D. mauritiana and D. simulans carrying recessive markers. The X and second chromosomes had no effect, while a clear effect was found for chromosome 3. Since the toxicity of morinda is due to middle-length fatty acids, the behavior of the three species toward various acids was investigated. We found that D. sechellia exhibited a general oviposition preference for acids, while D. simulans was repelled by acids with at least four carbons. Surprisingly D. mauritiana exhibited behavior quite similar to that of D. simulans. Preference for morinda in D. sechellia and D. mauritiana could be mediated by different chemicals.

Animals↗

PubMed1994

Horizontal transmission versus ancient origin: mariner in the witness box.

The transposable element mariner has been found in many species of Drosophilidae, several groups of Arthropods, and more recently in Platyhelminthes as well as in a phytopathogenic fungus. In the family Drosophilidae, the distribution of mariner among species shows many gaps, and its geographical distribution among endemic species is restricted to Asia and Africa. Among mariner elements in species within and outside the Drosophilidae, the similarities in nucleotide sequence and the amino acid sequence of the putative transposase reveal many phylogenetic inconsistencies compared with the conventional phylogeny of the host species. This paper discusses the contrasting hypotheses of horizontal transfer versus ancestral origin proposed to explain these results.

Africa↗

PubMed1994

The mariner transposable element in the Drosophilidae family.

The distribution of the mariner transposable element among Drosophilidae species was investigated using three different techniques, i.e. squash blots, Southern blots and PCR amplification, using two sets of primers (one corresponding to the Inverted Terminal Repeats and the other to two conserved regions of the putative transposase). Our results and those of others show that the distribution of mariner is not uniform and does not follow the phylogeny of the host species. An analysis of geographical distribution, based on endemic species, shows that mariner is mainly present in Asia and Africa. At least two hypotheses may be proposed to explain the specific and geographical distributions of this element. Firstly, they may be the results of several horizontal transmissions between Drosophila species and/or between Drosophila species and one or several donor species outside the Drosophilidae family. Secondly, these particular distributions may correspond to the evolution of the mariner element from an ancestral copy which was present in the ancestor of the Drosophilidae family.

Animals↗

PubMed1994

The identity of Leishmania isolated from sand flies and vertebrate hosts in a major focus of cutaneous leishmaniasis in Baturite, northeastern Brazil.

During a field investigation carried out in Baturite, Brazil from 1989 to 1991, sand flies, sympatric rodents, domestic dogs and humans were surveyed for leishmaniasis. Twenty strains of Leishmania were isolated by in vitro culture from Lutzomyia whitmani, three strains were obtained from Rattus rattus, two strains from dogs, and five strains from humans. The isolates were characterized by isoenzyme electrophoresis by hybridization with kinetoplast DNA-specific probes. All the samples were identified as L. (Viannia) braziliensis. The importance of these results in the dynamics of the Leishmania infection in this focus is discussed.

Animals↗

PubMed1994

Cutaneous leishmaniasis in Ceara state in northeastern Brazil: incrimination of Lutzomyia whitmani (Diptera: Psychodidae) as a vector of Leishmania braziliensis in baturite municipality.

Baturite is an important endemic zone of American cutaneous leishmaniasis in the state of Ceara, where an entomologic survey has been carried out to obtain information about transmission of the disease. From October 1989 through August 1991, natural infections with flagellates were detected in 34 of 3,000 Lutzomyia whitmani, five of 1,667 Lu. migonei, three of 5,278 Lu. wellcomei, one of 646 Lu. shannoni, and one of 21 Lu. evandroi. Thirty-five infections were peripylarian (i.e., behind the pylorus in the sand fly gut with a tendency to invade the midgut anterior to the pylorus). Fifteen infections (14 from Lu. whitmani and one from Lu. migonei) have been characterized as Leishmania (Viannia) braziliensis by isoenzyme electrophoresis, incriminating this species as a vector of the parasite in this area. Other possible vectors include Lu. wellcomei, Lu. migonei, and Lu. shannoni. Transmission appears to occur in peridomestic sites, especially around animal enclosures. Most cases of cutaneous leishmaniasis were recorded between September and December in Baturite during the period of study.

Animals↗

PubMed1994

American cutaneous leishmaniasis: in situ characterization of the cellular immune response with time.

The cellular nature of the infiltrate in the skin of patients with American cutaneous leishmaniasis was characterized by immunohistochemistry. The study population consisted of patients in Ceara, Brazil, an area where Leishmania braziliensis is endemic. Biopsies were taken from lesions present for 0.5-4 months duration and sections were stained with antibodies to T cells, T cell subsets, B cells, and macrophage markers to quantitate these cell types. The T cells accounted for 37.0 +/- 7.6% (mean +/- SD) of the infiltrate. The average percentages of CD4- and CD8-positive T cells were similar to each other, 20.4 +/- 9.0% and 19.9 +/- 6.7%, respectively. Interleukin-2 receptor-positive cells and B cells were infrequent, 3.7 +/- 3.0% and 2.3 +/- 3.1%, respectively. When the relationship between the age of the lesion at biopsy and the cellular phenotype was examined, it was noted that the percentage of positive cells remained fixed for all cell types except for that of gamma delta cells, which decreased with time. It is likely that gamma delta T cells are important in the early phase of the immune response to L. braziliensis and may, in general, be important in the early immune response of granulomatous diseases.

Adolescent↗

PubMed1993

Adaptation to alcoholic fermentation in Drosophila: a parallel selection imposed by environmental ethanol and acetic acid.

Besides ethanol, acetic acid is produced in naturally fermenting sweet resources and is a significant environmental stress for fruit-breeding Drosophila populations and species. Although not related to the presence of an active alcohol dehydrogenase, adult acetic acid tolerance was found to correlate with ethanol tolerance when sensitive (Afrotropical) and resistant (European) natural populations of Drosophila melanogaster were compared. The same correlation was found when comparing various Drosophila species. Tolerance to acetic acid also correlated with the tolerance to longer aliphatic acids of three, four, or five carbons but did not correlate with the tolerance to inorganic acids (i.e., hydrochloric and sulfuric acids). These observations suggest that acetic acid is detoxified by the conversion of acetate into acetyl-CoA, a metabolic step also involved in ethanol detoxification. Future investigations on the adaptation of Drosophila to fermenting resources should consider selective effects of both ethanol and acetic acid.

Acclimatization↗

PubMed1993

Recombinant migration inhibitory factor induces nitric oxide synthase in murine macrophages.

A recombinant form of migration inhibitory factor (MIF) obtained from COS-1 cells transfected with a cDNA library from a human T cell hybridoma is able to activate, in a dose-dependent manner, murine macrophages to express nitric oxide (NO) synthase and to produce high levels of NO in vitro. The time course of the induction of NO synthase is similar to that produced by the IFN-gamma. Enzyme activity peaks at 24 h and is undetectable by 72 h. MIF can synergize with IFN-gamma in the induction of NO synthesis, and the induction of NO synthase by both MIF and IFN-gamma is sensitive to inhibition by dexamethasone. However, unlike IFN-gamma-induced NO generation, MIF is sufficient for the induction of the enzyme, does not synergize with LPS, and is highly sensitive to inhibition by transforming growth factor.

Amino Acid Oxidoreductases↗

PubMed1993

MIF as a GST.

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Journal Article↗

PubMed1993

Studies on the control of visceral leishmaniasis: validation of the Falcon assay screening test--enzyme-linked immunosorbent assay (FAST-ELISA) for field diagnosis of canine visceral leishmaniasis.

The Falcon assay screening test-enzyme-linked immunosorbent assay (FAST-ELISA), the latest version of the enzyme-linked immunosorbent assay, uses antigen-coated beads. A 96-well plate can be run in 20 min without electricity or expensive equipment. We compared the FAST-ELISA, a standard ELISA, and an indirect immunofluorescent assay (IFA) for evaluation of canine leishmaniasis under field conditions using samples from 161 dogs from our longitudinal study in the endemic area of Jacobina, Bahia, Brazil. Organisms were isolated by culture (NN medium) or by inoculation of hamsters with samples from 59 of the dogs. When plasma were tested, we found a sensitivity of 88% and a specificity of 90% using the FAST-ELISA with a spectrophotometer. Using the same plasma samples, the IFA had a sensitivity of 75% and a specificity of 93%. The standard ELISA had a sensitivity of 90% and a specificity of 85%. When whole blood was tested with the FAST-ELISA, we found a sensitivity of 85%. There was no significant difference between visual and spectrophotometric results with plasma or whole blood. The FAST-ELISA system provides a sensitive, specific, and field-adaptable test for canine visceral leishmaniasis, which can be evaluated quickly without the use of a microscope or spectrophotometer.

Animals↗

PubMed1992

Recombinant human migration inhibitory factor has adjuvant activity.

Recombinant human migration inhibitory factor (MIF), isolated through functional expression cloning in COS-1 cells, up-regulates expression of genes encoding HLA-DR and interleukin 1 beta (IL-1 beta) and elaboration of IL-1 beta by human monocyte-derived macrophages. Administration of soluble bovine serum albumin or human immunodeficiency virus 120-kDa glycoprotein (HIV gp120) to mice in the presence of recombinant MIF together with incomplete Freund's adjuvant induced a strong T-cell proliferative response comparable to that of complete Freund's adjuvant. Recombinant MIF also increased antibody production, especially of IgG1 and IgM, in mice. Taken together, these results indicate that recombinant MIF may be useful as an adjuvant in the development of vaccines.

Adjuvants, Immunologic↗

PubMed1992

Evolution of the transposable element mariner in the Drosophila melanogaster species group.

The population biology and molecular evolution of the transposable element mariner has been studied in the eight species of the melanogaster subgroup of the Drosophila subgenus Sophophora. The element occurs in D. simulans, D. mauritiana, D. sechellia, D. teissieri, and D. yakuba, but is not found in D. melanogaster, D. erecta, or D. orena. Sequence comparisons suggest that the mariner element was present in the ancestor of the species subgroup and was lost in some of the lineages. Most species contain both active and inactive mariner elements. A deletion of most of the 3' end characterizes many elements in D. teissieri, but in other species the inactive elements differ from active ones only by simple nucleotide substitutions or small additions/deletions. Active mariner elements from all species are quite similar in nucleotide sequence, although there are some species-specific differences. Many, but not all, of the inactive elements are also quite closely related. The genome of D. mauritiana contains 20-30 copies of mariner, that of D. simulans 0-10, and that of D. sechellia only two copies (at fixed positions in the genome). The mariner situation in D. sechellia may reflect a reduced effective population size owing to the restricted geographical range of this species and its ecological specialization to the fruit of Morinda citrifolia.

Alleles↗

PubMed1992

Multiple amylase genes in Drosophila ananassae and related species.

The number and organization of amylase genes in Drosophila ananassae were investigated through classical genetic methods and in situ and filter hybridizations. At least four genes may be active in D. ananassae, organized as two independent pairs of closely linked copies on the 2L and 3L chromosomal arms. Several other species of the D. ananassae subgroup were studied and show the same chromosomal locations, suggesting an ancient duplication event. However, the number of Amy copies seems to be higher in the D. ananassae multigene family, and there is a striking intraspecific molecular differentiation.

Amylases↗

PubMed1992

Sequence analysis of active mariner elements in natural populations of Drosophila simulans.

Active and inactive mariner elements from natural and laboratory populations of Drosophila simulans were isolated and sequenced in order to assess their nucleotide variability and to compare them with previously isolated mariner elements from the sibling species Drosophila mauritiana and Drosophila sechellia. The active elements of D. simulans are very similar among themselves (average 99.7% nucleotide identity), suggesting that the level of mariner expression in different natural populations is largely determined by position effects, dosage effects and perhaps other factors. Furthermore, the D. simulans elements exhibit nucleotide identities of 98% or greater when compared with mariner elements from the sibling species. Parsimony analysis of mariner elements places active elements from the three species into separate groups and suggests that D. simulans is the species from which mariner elements in D. mauritiana and D. sechellia are most likely derived. This result strongly suggests that the ancestral form of mariner among these species was an active element. The two inactive mariner elements sequenced from D. simulans are very similar to the inactive peach element from D. mauritiana. The similarity may result from introgression between D. simulans and D. mauritiana or from selective constraints imposed by regulatory effects of inactive elements.

Animals↗

PubMed1991

Human recombinant migration inhibitory factor activates human macrophages to kill Leishmania donovani.

A recombinant form of the first lymphokine to be discovered, migration inhibitory factor (rMIF) was obtained from COS-1 cells transfected with a cDNA library from a human T cell hybridoma (6). rMIF has an amino acid sequence unrelated to that of any known protein. To learn more about the biology of MIF, we tested its ability to effect the survival of Leishmania donovani in macrophages. We found that rMIF activates blood monocyte-derived macrophages in vitro to suppress the growth of and kill these intracellular parasites. The anti-leishmanial effect (ranging from 50 to 77% reduction of parasites) is maximal when macrophages have been incubated with rMIF 48 to 72 h before infection and is similar to that seen with macrophages activated by IFN-gamma. Of interest, whereas the activation of human macrophages by IFN-gamma is inhibited by IL-4 and not enhanced by LPS, the activation by rMIF is enhanced by LPS but is not inhibited by IL-4. The data presented here demonstrate that rMIF is a potent activator of macrophages and is likely to be critical in cell-mediated immune host defenses.

Animals↗

PubMed1991

Host-plant specialization in the Drosophila melanogaster species complex: a physiological, behavioral, and genetical analysis.

Drosophila sechellia, endemic to the Seychelles, breeds in a single resource, Morinda citrifolia, whereas its close sympatric relative, Drosophila simulans, is a cosmopolitan generalist breeding in a great variety of resources. The effects of morinda on various fitness traits of these two species, their F1 hybrids, and reciprocal backcrosses were analyzed. Morinda fruit is highly toxic to Drosophila species, except D. sechellia. The toxicity is expressed in adults, embryos, and larvae. In embryos, early mortality is a maternally inherited trait, depending only on mother's genotype. The tolerance of D. sechellia to morinda is fully dominant in F1 hybrids. Egg production is stimulated by morinda in D. sechellia but inhibited in D. simulans; in hybrids, the inhibition observed in D. simulans is dominant. Morinda is an oviposition attractant for D. sechellia but a repellent for D. simulans; F1 hybrids and backcross individuals exhibit intermediate, approximately additive, behavior. In the field, adult flies of the two species exhibit opposite behavior in that D. sechellia is attracted to morinda and D. simulans is attracted to banana; hybrids have an intermediate behavior. These differences between the species explain why they do not hybridize in nature although living in sympatry. The various traits have different genetic bases: three or four different genes, or groups of genes, differentiate the ecological niches of the two species.

Animals↗

PubMed1991

Insertion sites of the transposable element mariner are fixed in the genome of Drosophila sechellia.

The abundance of the transposable element mariner differs dramatically in the genomes of the closely related species Drosophila simulans, D. mauritiana, D. sechellia, and D. melanogaster. Natural populations of D. simulans and D. mauritiana have 1-10 and 20-30 copies per diploid genome, respectively, and the insertion sites are polymorphic. The element has not been found in D. melanogaster. In this paper we show that D. sechellia, a species endemic to the Seychelles Islands, contains only two mariner elements that are at fixed sites in the genome. One element, inserted in chromosome 2R at 51A1-2, contains three deletions and is missing much of the 3' end. The other element, inserted in chromosome 3L at 64A10-11, is the full length of 1286 bp. Although the sequence of the full-length element is polymorphic in populations of D. sechellia, at least some of the sequences are closely related to elements from D. simulans and D. mauritiana that are known to be active. However, judging from the progeny of crosses between D. sechellia and D. simulans, the biological activity of the full-length D. sechellia element appears to be low, either because of the nucleotide sequence of the element or because of its position in the genome, or both.

Animals↗

PubMed1991

Genetics of morphological differences and hybrid sterility between Drosophila sechellia and its relatives.

We conducted classical genetic analysis of the difference in male genitalia and hybrid sterility between the island-dwelling sibling species Drosophila sechellia and D. mauritiana. At least two loci (one on each autosome) are responsible for the genital difference, with the X chromosome having no significant effect. In contrast, male hybrid sterility is caused by at least four gene loci distributed among all major chromosomes, with those on the X chromosome having the largest effect. We also show that the large difference in ovariole number between D. sechellia and its mainland relative D. simulans is due to at least two gene substitutions, one on each major autosome. The X and the left arm of the second chromosome, however, have no significant effect on the character. This implies that the evolution of reduced ovariole number involved relatively few gene substitutions. These results extend previous findings that morphological differences between Drosophila species are caused by genes distributed among all chromosomes, while hybrid sterility and inviability are due primarily to X-linked genes. Because strong X-effects on male sterility have been found in all three pairwise hybridizations among D. simulans, D. sechellia and D. mauritiana, these effects must have evolved at least twice independently.

Animals↗