Search PubMed⌕ Search

Biomedical subjects

J R David

Publications and source records attributed to J R David.

At least 91 records · Page 5Linked to original sources
PubMed1991

Leishmania (Viannia) braziliensis: comparative pathology of golden hamsters infected with isolates from cutaneous and mucosal lesions of patients residing in Tres Bracos, Bahia, Brazil.

The histopathology of primary forepaw and metastatic lymph node, spleen, and liver lesions produced in golden hamsters infected with cutaneous leishmaniasis (CL) strains (LTB 111 and LTB558) and mucocutaneous leishmaniasis (MCL) strains (LTB12 and LTB201) of Leishmania (Viannia) braziliensis isolated from patients residing in Tres Bracos, Bahia, Brazil is described. No pathological features providing clear differentiation of the CL and MCL strains were found. Although amastigotes were plentiful early in the development of primary forepaw lesions, they were either absent or could not be identified with certainty in sections of late stage lesions. Similarly, amastigotes were not found in histologic lesions at metastatic sites; however, leishmanial DNA was detected in both early and late stage forepaw lesions and metastatic lesions using Leishmania kinetoplast DNA and the gene coding for gp63 as hybridization probes. The DNA recovered from metastatic lesions was extracted from formalin-fixed paraffin-embedded tissues that had been stored at room temperature for prolonged periods.

Animals↗
PubMed1991

Phlebotomine sandfly (Diptera: Psychodidae) fauna survey in an American cutaneous leishmaniasis (ACL) focus in Baturité, Ceará State, northeast Brazil.

From October until July 1991, CDC miniature light traps were set up and man and animal-landing and biting catches were made in 100 different catching zones, in different habitats, throughout the ACL focus of the Serra de Baturité. Female Lutzomyia whitmani and Lu. wellcomei appeared to be highly anthropophilic and were the most prevalent species in man-landing catches in peridomestic sites. Most Lu. migonei were attracted to animals, especially mules. Seasonal fluctuations and habitat preference were noted for the principal populations present.

Animals↗
PubMed1990

Active mariner transposable elements are widespread in natural populations of Drosophila simulans.

The occurrence of active, or autonomous, mariner elements was investigated by crossing white-peach mutant Drosophila simulans females with wild-type males from various geographic origins. From a total of 194 experimental crosses only 17 failed to produce progeny with eye mosaicism (MOS, i.e. pigmented spots in otherwise white-peach eyes). Therefore, active mariner elements inducing somatic excision of the copy inserted at the white locus are abundant in all populations sampled. In the experimental crosses the frequency of mosaic offspring ranged from 0 to 100%, showing that the phenotypic expression is highly variable. The MOS phenotype, measured by the number of spots on the eyes, is quite variable within the progeny of single crosses. Although a difference was observed in the average MOS score (percentage of mosaic flies) between northern and southern populations of France, there was no indication of long range variation between geographic populations. Neither was there a systematic difference between recently collected populations and samples kept several years as isofemale lines.

Animals↗
PubMed1990

A cloned ATP:guanidino kinase in the trematode Schistosoma mansoni has a novel duplicated structure.

Creatine kinase (CK) is part of a conserved family of ATP:guanidino phosphotransferases whose members play important roles in intracellular energy flow. Previously characterized members of this family are approximately 80-kDa dimers of two related 40-kDa subunits. We have cloned a gene from the parasitic trematode Schistosoma mansoni which has substantial amino acid sequence similarities to CK. Like the genes for vertebrate CKs, this gene is developmentally regulated; mRNA levels are high in the infective cercarial stage but rapidly decrease upon transformation to the parasitic schistosomulum stage. In contrast to members of the guanidino phosphotransferase family characterized previously, however, the schistosome gene appears to be a direct fusion of two CK-like domains that encode a single 74-kDa polypeptide. Correlative evidence from enzyme assays of crude parasite homogenates suggests that the cloned gene is a creatine kinase. This represents the first molecular cloning of an invertebrate ATP:guanidino phosphotransferase.

Amino Acid Sequence↗
PubMed1990

A serum factor that suppresses the cytotoxic function of cytokine-stimulated human eosinophils.

A human subject (NR) was identified whose eosinophils and neutrophils failed to respond to TNF in vitro in 29 of 33 experiments, using several biological assays. There was a response rate to TNF of 100% among 37 control subjects whose leukocytes were tested in parallel. NR serum contained an activity that inhibited the cytotoxic function of TNF- and GM-CSF-stimulated normal human eosinophils. A similar activity was detected in 4 of 122 control sera and in sera of two subjects with hypereosinophilia. This activity (ECI) had an apparent molecular weight of 80,000-100,000 and was sensitive to heating at 80 degrees C or to trypsin treatment. HPLC sizing chromatography increased the titer of ECI by a factor of 50 to 2,000 in experiments using NR serum or other sera with detectable inhibitory activity. In seven experiments using sera with no inhibitory activity, HPLC generated ECI of the same apparent molecular weight. The effect of HPLC on ECI activity required the separation of serum components and did not result from exposure to HPLC system components or other sample processing methods. This suggests that ECI in serum can be stabilized in an inactive or partially active form and that HPLC removes the stabilizing component. ECI suppressed TNF-stimulated eosinophil cytotoxic function when added to cultures up to 4 h after exposure of eosinophils to cytokine. However, ECI did not protect L929 cells from the toxic effects of TNF. Thus, ECI did not act by preventing the initial interaction of TNF with eosinophils or by interfering with the binding of TNF to its receptor on L929 cells. The results suggest that ECI is a component of a feedback mechanism that suppresses functions of cytokine-activated eosinophils in inflammation.

Animals↗
PubMed1989

Human eosinophil cytotoxicity-enhancing factor. Purification, physical characteristics, and partial amino acid sequence of an active polypeptide.

Medium conditioned by PMA/LPS-stimulated U937 cells was processed for the purification of an eosinophil cytotoxicity-enhancing factor (ECEF) by the following sequence: 1) phenyl-Sepharose chromatography; 2) DEAE-cartridge chromatography; 3) preparative SDS-gel electrophoresis; and 4) reversed-phase HPLC. This resulted in the isolation of a 10 kDa polypeptide with ECEF activity. Purified material from 21 different preparations enhanced eosinophil killing of antibody-coated Schistosoma mansoni schistosomula by a mean of 206% (increase from 13.2 +/- 7.9% to 40.4 +/- 20.2% of targets killed, p less than 0.0001). Activity was maximal at a concentration of 20 ng ECEF polypeptide/ml and half-maximal between 0.8 and 4 ng/ml. Antibody specific for the 10 kDa polypeptide precipitated ECEF activity from a crude preparation and, by Western blot analysis, reacted only with a 10 kDa species in that preparation. The following N-terminal amino acid sequence was determined for the purified polypeptide: Val-Lys-Gln-Ile-Glu-Ser-Lys-Thr-Ala-Phe-Gln-Lys-Ala-Leu- -Ala- Gly- -Lys-Leu.... Computer search showed that this sequence is unrelated to other known protein sequences. Thus, the ECEF polypeptide is a newly defined monokine, with the ability to enhance eosinophil cytotoxic function in vitro. This monokine may be an important regulator of eosinophil function in inflammation in vivo.

Amino Acid Sequence↗
PubMed1989

Activation of eosinophils in cancer patients treated with IL-2 and IL-2-generated lymphokine-activated killer cells.

Of 16 patients, a total of 13 who received IL-2 and autologous IL-2-generated lymphokine-activated killer LAK cells developed eosinophilia late during the course of treatment. To understand the direct or indirect effects of IL-2 on eosinophils, the physical and functional characteristics of the late-treatment eosinophils were compared to those of early-treatment and control eosinophils. Late-treatment eosinophils differed from early-treatment and control eosinophils in the following respects: they had somewhat reduced density, hypersegmented nuclei, eosinophil cationic protein converted from the storage form to the secretory form, and a greater than 200% increased ability to kill larvae of Schistosoma mansoni by an antibody-dependent mechanism (cytotoxic function). In vitro, IL-2 (1000 U/ml in medium as used to culture LAK cells) did not affect the cytotoxic function of eosinophils from cancer patients or from control subjects. However, LAK cell-conditioned medium enhanced the cytotoxic function of eosinophils from early-treatment cancer patients and from normal subjects by greater than 150%. Thus, eosinophils late in the course of IL-2/LAK cell treatment undergo physical changes and become functionally activated. The involvement of IL-2 in these changes is probably indirect, as an inducer of factors that enhance eosinophil function.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1989

Plasmodium falciparum: DNA probe diagnosis of malaria in Kenya.

We previously reported isolation of DNA probe which specifically recognizes Plasmodium falciparum and developed a simple method for its use. The sensitivity and specificity of this DNA probe method have now been extensively field tested in comparison with those of conventional microscopic examination of blood films in two separate studies in Malindi, Kenya, involving a total of 1179 patients. In the second study, which used improved techniques, sensitivity of the DNA probe was 89% when compared to microscopy. We conclude that the DNA probe method compares favorably with conventional microscopy in detecting parasite densities as low as 25 parasites per microliter of blood. A significant advantage of the DNA probe method is that it utilizes a standardized procedure which can simultaneously and reproducibly analyze a large number of samples without opportunity for significant reader bias.

Adult↗
PubMed1989

Latitudinal variation of Adh gene frequencies in Drosophila melanogaster: a Mediterranean instability.

The relationship between allelic frequencies at the Adh locus and latitude of origin was studied using selected published data from various parts of the world and original observations. An overall increase of Adh-F with increasing latitude was observed but the relationship is not linear. Tropical populations are generally similar, having a low frequency of the F allele (average 15 per cent) and a smooth increase with latitude (one per cent for one degree). Between 30 and 42 degrees latitude, populations living in a Mediterranean climate in various parts of the world (Mediterranean countries, Australia's east coast and North America's west coast) are also similar, with a much higher average frequency of F (70 per cent), a steeper slope (two per cent) and a broader range of variability for a given latitude. In a restricted area (near Cordoba in southern Spain) numerous wild collected samples also showed a large variability, sometimes over a very short distance. Allelic frequencies in Mediterranean countries are thus quite unstable and it is proposed that this phenomenon be called a "Mediterranean instability". Further north, numerous samples from France were characterized by an even higher frequency of F (95 per cent) and a greater homogeneity over a broad geographic area. These observations are discussed and the need for more field studies is emphasized.

Africa↗
PubMed1989

Geographical polymorphism of amylase in Drosophila ananassae and its relatives.

Strains of Drosophila ananassae from various places in the Tropics were investigated for their electrophoretical amylase pattern. Eleven isoamylases were found in adult flies. African populations were much more polymorphic than those from the Far East, and showed multibanded phenotypes, suggesting a multiplication of the Amy structural gene, with at least four copies per haploid genome in certain populations. Nine other species of the D. ananassae subgroup had weak amylase activity and only one or two variants were found in each species. D. monieri and D. varians are closely related to D. ananassae and showed a single band, similar to the isoamylase 3 of D. ananassae, which suggests that this might be an ancestral allele.

Africa↗
PubMed1989

Molecular cloning of a cDNA encoding a human macrophage migration inhibitory factor.

A cDNA encoding a human macrophage migration inhibitory factor (MIF) was isolated, through functional expression cloning in COS-1 cells, from a cDNA library prepared from a lectin-stimulated T-cell hybridoma, T-CEMB. The 115-amino acid polypeptide encoded by the MIF cDNA (p7-1) was effectively released from the transfected COS-1 cells and yielded readily detectable MIF activity in the culture supernatant despite the apparent lack of a classical protein secretory sequence. Insertional mutational analysis and elution of MIF activity from polyacrylamide gel slices demonstrated that the Mr 12,000 protein with MIF activity released by the COS-1 cells is encoded by p7-1. The p7-1 cDNA hybridized with a 700-base mRNA expressed by Con-A-stimulated lymphocytes but not unstimulated lymphocytes. The availability of the MIF cDNA clone and recombinant MIF will facilitate the analysis of the role of this lymphokine in cell-mediated immunity, immunoregulation, and inflammation.

Amino Acid Sequence↗
PubMed1989

Short-range genetic structure of Drosophila melanogaster populations in an Afrotropical urban area and its significance.

Alcohol dehydrogenase (Adh) (alcohol:NAD+ oxidoreductase, EC 1.1.1.1) gene frequencies and ethanol tolerance in Drosophila melanogaster are known to exhibit long-range latitudinal variations on different continents; this has led to the argument that the clines are adaptive. Accordingly, tropical populations are characterized both by a low frequency of Adh-F and by a low ethanol tolerance. In the urban area of Brazzaville (Congo) under an equatorial African climate, an original genetic structure of local populations has been found: Adh-F frequency varies from 3% to 90% when countryside and brewery populations are compared. This variation is accompanied by an increase of ethanol tolerance (from 6% to 13% alcohol). Such differences, which have remained stable for the past 3 years, were observed between collection sites less than 1 km apart. Two other enzyme loci exhibited a correlated variation with Adh-F--i.e., an increase of the S allele of glycerol-3-phosphate dehydrogenase (NAD+) (sn-glycerol-3-phosphate:NAD+ 2-oxidoreductase, EC 1.1.1.8) and of the F allele of glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate:NADP+ 1-oxidoreductase, EC 1.1.1.49). Such observations suggest very strong selective pressures exerted by environmental ethanol that oppose the gene flow due to adult dispersal between contiguous habitats. A functional relationship between the polymorphisms of the three enzyme loci seems likely, and a metabolic interaction involving NAD and NADP cofactors is proposed.

Alleles↗
PubMed1988

Identification and characterization of a non-interferon antileishmanial macrophage activating factor (antileishmanial MAF).

A non-interferon lymphokine elaborated from PHA and Con A-stimulated human T-cell hybridoma, T-CEMA, has been found to activate monocyte-derived macrophages for the intracellular killing of L. donovani (antileishmanial MAF). This T-cell hybridoma derived antileishmanial MAF which has an apparent mw of 65,000 and pI of 5.3-5.6, contains neither antiviral activity nor colony stimulating activity. Furthermore, antileishmanial MAF is not neutralized by anti-MIF, anti-IFN-gamma or anti-GM-CSF antibodies.

Animals↗
PubMed1988

Mitochondrial DNA variability in Drosophila simulans: quasi absence of polymorphism within each of the three cytoplasmic races.

Nucleotide variability of mtDNA extracted from 144 isofemale lines collected in the whole range of D. simulans was analysed with 10-15 restriction enzymes and 73 lines were studied using one or a few enzymes. All clones were distributed into 3 mitochondrial genomes, siI, siII and siIII. These types are allopatric and can define geographic races. Mixed populations occur only in Madagascar and Réunion, where siII and siIII are found together. Among 40 sites detected with 10 enzymes, the variability of the coding region is extremely low, with one or no polymorphic restriction sites depending on the type. The control A + T-rich region is more variable in length and in restriction sites, and allows subtypes to be designated. Several lines were heteroplasmic for the length of the genome. These results are relevant to the evolutionary history of the species, its recent worldwide extension and to probable founder effects at the origin of each of the three types.

Animals↗