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L Nigro

Publications and source records attributed to L Nigro.

At least 37 records · Page 2Linked to original sources
PubMed1996

A molecular phylogeny for the Drosophila melanogaster subgroup and the problem of polymorphism data.

Drosophila melanogaster belongs to a closely related group of eight species collectively known as the melanogaster subgroup; all are native to sub-Saharan Africa and islands off the east coast of Africa. The phylogenetic relationships of most species in this subgroup have been well documented; however, the three most closely related species, D. simulans, D. sechellia, and D. mauritiana, have remained problematic from a phylogenetic standpoint as no data set has unambiguously resolved them. We present new DNA sequence data on the nullo and Serendipity-alpha genes and combine them with all available nuclear DNA sequence data; the total data encompass 12 genes and the ITS of rDNA. A methodological problem arose because nine of the genes had information on intraspecific polymorphisms in at least one species. We explored the effect of inclusion/exclusion of polymorphic sites and found that it had very little effect on phylogenetic inferences, due largely to the fact that 82% of polymorphisms are autapomorphies (unique to one species). We have also reanalyzed our previous DNA-DNA hybridization data with a bootstrap procedure. The combined sequence data set and the DNA-DNA hybridization data strongly support the sister status of the two island species, D. sechellia and D. mauritiana. This at least partially resolves what had been a paradox of parallel evolution in these two species.

Animals↗
PubMed1996

Immunological findings in HIV-Leishmania coinfection.

It is supposed that Leishmania infection increases human immunodeficiency virus (HIV) replication in seropositive individuals. Two groups of 9 HIV-infected intravenous drug users each, one group with HIV-Leishmania coinfection (as determined by bone marrow microscopy, culture and an immunofluorescent assay, the other with HIV infection alone, but no evidence of Leishmania coinfection were matched for sex, age, time since first diagnosis of HIV infection, number of AIDS-defining diseases, proportion of patients treated with AZT and months of treatment, CD4/CD8 ratio, beta 2-microglobulin level and HIV p24 antigen positivity rate. IL-4, -6, -10 and -12 and IFN-gamma levels were determined by commercial enzyme immunoassays. The HIV-1 RNA copy number was quantified with the nucleic-acid-sequence-based amplification method (NASBA). The differences between the two groups were highly significant for all markers determined except for IL-12 and IFN-gamma. We found a higher viral load in the patients with HIV-Leishmania coinfection compared to the patients with HIV infection alone (p < 0.009). In 6 HIV-positive individuals without Leishmania coinfection, the HIV-1 RNA copy number was below the detection limit of NASBA (i. e. < 400 copies/100 microliters). Plasma levels of IL-4, -6, and -10 were significantly elevated in the coinfected group (p < 0.0001; p < 0.02, and p < 0.005). The results of our study show that the viral load is increased in patients with HIV-Leishmania coinfection in comparison to the controls. This might be partly due to Th2 immune activation, as demonstrated by higher plasma levels of IL-4, -6 and -10 in HIV-Leishmania-coinfected patients than in HIV-infected individuals.

AIDS-Related Opportunistic Infections↗
PubMed1996

Mitochondrial DNA sequence variation across linguistic and geographic boundaries in Italy.

A previous investigation demonstrated the existence of extensive allele frequency diversity within an area of northern Italy crossed by a linguistic (dialect) boundary and by the Po River, either of them or both presumably constraining gene flow. We obtained hair samples from 45 school pupils from 9 localities in that area and sequenced a 255-bp segment of the mtDNA D loop. Estimates of the minimum number of migration events from gene genealogies suggest that the linguistic barrier impaired gene flow more than the river did. However, an analysis of molecular variance (AMOVA) showed that most sequence diversity occurs within rather than between populations and that the differences between groups of populations, defined either by linguistic or geographic criteria, do not reach significance. Three areas of rapid genetic variation were identified; their locations suggest that populations of the western part of the study area evolved in relative isolation. Therefore mtDNA sequence variation does not seem to reflect the same processes--drift and presence of dispersal barriers--that led to the observed distributions of nuclear allele frequencies.

Adolescent↗
PubMed1996

High mitochondrial sequence diversity in linguistic isolates of the Alps.

Segment I of the control region of mtDNA (360 bases) was sequenced in seven samples, each of 10 individuals inhabiting villages in the eastern Italian Alps (South Tyrol and Trentino). Three linguistic groups, German, Italian, and Ladin, were represented by two samples each; the seventh sample comes from an isolated group of German origin, the Mocheni, who are linguistically distinct and geographically separated from the bulk of the German speakers. Seventy-four polymorphic sites were identified, defining 63 different haplotypes. Mocheni and Ladin speakers tend to form two clusters in the evolutionary trees inferred from sequences. Analysis of molecular variance shows significant differentiation within samples, among them, and among linguistic groups. Genetic differences between the Ladins and the other groups are not much smaller than between Europeans and some Africans; variation is large within groups, as well, with the exception of only the Mocheni. In the evolutionary trees where the four alpine groups are compared with other European populations, Mocheni and especially Ladins appear as clear outliers. Romansch-speaking Swiss, who are linguistically related to Ladins, are not genetically similar to them, for this segment of DNA. Because the time elapsed since colonization of the Alps (< or = 12,000 years) is short in mutational terms, the only model accounting for the observed relationships between mtDNA variation and linguistic identity seems one in which a population ancestral to Ladin speakers was already differentiated long before the Alps were settled and the current linguistic affiliations were established. For the Mocheni, the results are consistent with a simpler episode of allele loss, from an original genetic pool common to the ancestors of the current German speakers.

DNA, Mitochondrial↗
PubMed1994

Nuclear background affects frequency dynamics of mitochondrial DNA variants in Drosophila simulans.

Transplasmic lines, in which the original mitochondrial DNA (mtDNA) had been completely replaced by the mtDNA of the donor, were constructed to test for selection on mtDNA variants and to investigate the effects of nuclear-cytoplasmic interactions in Drosophila simulans. These lines were used to set up 12 experimental populations putting in competition two mtDNA variants with two different starting frequencies. Population cages were maintained for 20 generations and periodically sampled to monitor haplotype frequencies. Evidence is provided for a complete reversal of the forces acting on the frequency dynamics of the mtDNA variants according to the lines used to establish the population cages. In the cages where the competing lines had both the original nuclear and mtDNA, the siII type mtDNA variant seemed to be favoured but the situation was reversed when this variant was put in a different nuclear background.

Animals↗
PubMed1993

Rates of DNA evolution in Drosophila depend on function and developmental stage of expression.

DNA-sequence divergence of genes expressed in the embryonic stage was compared with the divergence of genes expressed in adults for 13 species of Drosophila representing various degrees of relatedness. DNA-DNA hybridization experiments were conducted using as tracers complementary DNA (cDNA) reversed transcribed from poly(A)+ mRNA isolated from different developmental stages. The results indicate: (1) cDNA is less diverged than total single-copy DNA; (2) cDNA sequences are not in the rapidly evolving fraction of the single-copy genome of Drosophila; (3) early in evolutionary divergence embryonic messages are about half as diverged as adult messages; sequence data from some of the species compared indicate this is likely due to differences in rates of silent substitutions in genes expressed at different stages of development; and (4) at greater evolutionary distance, the differences in embryonic and adult messages disappear; this could be due to lineage-specific shifts in codon usage.

Animals↗
PubMed1992

HCV infection in HBsAg positive chronic liver disease.

The prevalence of anti-HCV antibodies was determined for a group of 68 patients with various forms of chronic liver disease. All patients that were anti-HCV positive but did not show signs of HBV replication had severe liver disease. We therefore suggest that HCV may be responsible for liver damage in HBsAg positive subjects when there are no evident signs of HBV replication.

Chronic Disease↗
PubMed1992

Preliminary investigation on intrafamilial spread of hepatitis C virus (HCV).

To determine the risk of cohabitant HCV infection, we investigated the sera of 101 family members of 53 anti-HCV antibody positive chronic liver disease patients. Altogether 14.8% of the cohabitants were also anti-HCV antibody positive, compared to a prevalence of 1.4% in the general population. These results suggest that hepatitis-C-virus may spread by person-to-person infection.

Chronic Disease↗
PubMed1991

Mitochondrial DNA sequence divergence in the Melanogaster and oriental species subgroups of Drosophila.

The nucleotide sequence of a segment of the mitochondrial DNA from three Drosophila species (D. erecta, D. eugracilis, and D. takahashii), belonging to different subgroups of the melanogaster group has been determined. The segment encompasses three complete tRNA genes (tRNAtrp, tRNAcys, and tRNAtyr) and portions of two protein-coding genes: the subunit 2 of the NADH dehydrogenase (ND2) and the subunit 1 of the cytochrome oxidase (COI). Comparisons also involve homologous sequences already known for four other Drosophila species of the melanogaster group. Length differences were confined in the intergenic region where a long stretch of AT repeats was observed in one of the species analyzed. The three tRNA genes exhibit very different evolutionary rates, the most slowly evolving one, tRNAtyr, is adjacent to the 5' end of COI; tRNAs in similar positions have been previously shown to evolve slowly because they are probably involved in transcript processing. Although the rate of synonymous substitutions was very similar between ND2 and COI genes there were strong discrepancies between them in terms of the number of nonsynonymous substitutions. Differences have also been found in G + C content of the genes, which are likely to be linked to different selective pressures. There is a reduction in G + C content in the region where selective constraints are reduced. This suggests the existence of different levels of constraints along the sequenced segment. An overall analysis of the types of substitutions showed a decrease in A + T content during the course of evolution of the species.

Animals↗
PubMed1991

The effect of heteroplasmy on cytoplasmic incompatibility in transplasmic lines of Drosophila simulans showing a complete replacement of the mitochondrial DNA.

Unidirectional cytoplasmic incompatibility has been observed in crosses between different strains of Drosophila simulans when the males, but not the females, involved in the crosses are infected with intracellular rickettsia-like microorganisms. In contrast to what is known about this system an unexpected partial incompatibility has been observed between two infected strains. Transplasmic lines have been constructed in the laboratory to investigate this phenomenon. The injection of a foreign infected cytoplasm into a strain which apparently shows the same kind of bacterial infection causes an incompatibility in crosses between injected heteroplasmic males, but not injected females, of the same strain. These findings suggest that several crossing types exist within the Drosophila simulans incompatibility system. The complete replacement of the original mitochondrial DNA observed in some of the transplasmic lines made it possible to analyse and exclude any link between incompatibility and mitochondrial genomes.

Animals↗
PubMed1990

Is there selection on RFLP differences in mitochondrial DNA?

Experimental populations of Drosophila simulans were established for the purpose of detecting the presence or absence of selection on a restriction fragment length polymorphism in mitochondrial DNA (mtDNA). It was then discovered that the founding strains differed with respect to the Rickettsia-mediated incompatibility system in this species, which is maternally transmitted together with the mtDNA differences. A population model was constructed using the known fitness effects of the incompatibility system, with the result that the population trajectories can be completely explained by the effects of the microorganism with no need to invoke selection on mtDNA. The strong conclusion is that in this case we can rule out the strong selection proposed by MacRae and Anderson to explain the "dramatic mtDNA changes" in their Drosophila pseudoobscura populations. The population theory used for the experiments is discussed in the context of natural populations. Estimated parameters include the possibility that with two populations, one with the organism and one without it, there may be no bias as to which will invade the other, which in turn suggests no global tendency for the infection to spread or decline.

Animals↗
PubMed1983

Esterase-6 allozymes: biochemical studies of two common and one rare variant in Drosophila melanogaster.

The biochemical properties of three allozymes coded by the Est-6 locus, two common forms (EST-6S and EST-6F) and one rare form (EST-6VF), were studied. The results show the existence of differences in isoelectric point, activity, activation energy, Km, and temperature coefficient among the three variants, especially between the two common forms and the one rare form. The specific activity of the rare enzymatic variant seems to be less affected by temperature variation. The possible significance of these findings in relation to the mechanism of reproduction is briefly discussed.

Alleles↗
PubMedDate not supplied

HCV and HBV infection among multitransfused thalassemics from eastern Sicily.

Serum specimens from 152 Sicilian multitransfused thalassemic subjects were tested for antibodies to hepatitis C virus (anti- HCV) and for HBV markers by enzyme linked immunoassay and with reference to anti-HCV, confirmed by recombinant immunoblot assay. A high rate (47%) of subjects was anti-HCV positive. HBsAg was found in 8% of patients and 55% had anti-HBs or anti-HBc antibodies or both. Contrary to HBV infection, anti-HCV seropositivity was related to the number of transfused units. The highest anti-HCV prevalence was observed between 16 and 20 years; 100% of persons older than 50 years had at least one marker of HBV infection. In conclusion, HCV and HBV are widespread among multitransfused thalassemic. Probably in our area, particularly during the pre-HBsAg screening era, several multitransfused patients were infected by HBV more readily than by HCV.

Adolescent↗