PubMed Health⌕ Search

Biomedical subjects

L Baldo

Publications and source records attributed to L Baldo.

9 recordsLinked to original sources
PubMed2005

Phylogeny of Wolbachia pipientis based on gltA, groEL and ftsZ gene sequences: clustering of arthropod and nematode symbionts in the F supergroup, and evidence for further diversity in the Wolbachia tree.

Current phylogenies of the intracellular bacteria belonging to the genus Wolbachia identify six major clades (A-F), termed 'supergroups', but the branching order of these supergroups remains unresolved. Supergroups A, B and E include most of the wolbachiae found thus far in arthropods, while supergroups C and D include most of those found in filarial nematodes. Members of supergroup F have been found in arthropods (i.e. termites), and have previously been detected in the nematode Mansonella ozzardi, a causative agent of human filariasis. To resolve the phylogenetic positions of Wolbachia from Mansonella spp., and other novel strains from the flea Ctenocephalides felis and the filarial nematode Dipetalonema gracile, the authors generated new DNA sequences of the Wolbachia genes encoding citrate synthase (gltA), heat-shock protein 60 (groEL), and the cell division protein ftsZ. Phylogenetic analysis confirmed the designation of Wolbachia from Mansonella spp. as a member of the F supergroup. In addition, it was found that divergent lineages from Dip. gracile and Cte. felis lack any clear affiliation with known supergroups, indicating further genetic diversity within the Wolbachia genus. Finally, although the data generated did not permit clear resolution of the root of the global Wolbachia tree, the results suggest that the transfer of Wolbachia spp. from arthropods to nematodes (or vice versa) probably occurred more than once.

Animals↗
PubMed2005

Genetic variability in the three genomes of Nasonia: nuclear, mitochondrial and Wolbachia.

Nasonia consists of three closely related species of parasitoid wasps that are all infected with the endosymbiotic bacteria Wolbachia, a reproductive parasite common in arthropods. This situation presents the opportunity to compare patterns of variation in three associated genomes, Wolbachia and the nuclear and mitochondrial genomes of its host. Furthermore, although Nasonia wasps are emerging as a model for evolutionary and genetic studies, little is known about their genetic variability. Using amplified fragment length polymorphisms (AFLPs), all three species present a relatively high level of nuclear polymorphism and have different patterns of variation, with one of the species, Nasonia giraulti, being divided into two divergent subgroups. In each species, the mitochondrial pattern of variation is different from the nuclear pattern, possibly due to genetic hitchhiking of the mitochondria during (cytoplasmically inherited) Wolbachia sweeps. Mitochondria in Nasonia show a synonymous substitution rate approximately 10-15-fold higher than nuclear genes, probably reflecting an elevated mitochondrial mutation rate that is among the highest found in insects. Finally, all three species are doubly infected with their own strains of Wolbachia, one each from the two major supergroups (A and B). Sequence analysis reveals that each of the three Nasonia species acquired their A and B bacteria independently by horizontal transfer events from other insects with the exception of B type Wolbachia in N. longicornis and N. giraulti, which were acquired prior to speciation and then codiverged with the host. This represents one of the few clear-cut examples of codivergence of Wolbachia during host speciation.

Animals↗
PubMed2002

Different rates of nucleotide substitutions in Wolbachia endosymbionts of arthropods and nematodes: arms race or host shifts?

The genus Wolbachia encompasses intracellular bacteria found in arthropods and in filarial nematodes. In arthropods, Wolbachia is primarily a reproductive parasite and shows relatively frequent horizontal transfer between host species, while in nematodes it appears to be a mutualist and is strictly vertically transmitted. We can expect that different selective pressures are acting on their genomes. Here we present an analysis of three Wolbachia genes, wsp, ftsZ and dnaA. In wsp of arthropod Wolbachia, an excess of non-synonymous substitutions was observed, providing evidence for positive selection. In nematode Wolbachia, no evidence for positive selection was found. Pressure for amino acid variation in wsp of arthropod Wolbachia could derive either from an arms race with the host or from the occurrence of more frequent hosts shifts due to horizontal transmission. In nematode Wolbachia, the lack of positively selected sites could result from the absence of an arms race, or from the homogeneity of the biochemical environment they exist in (ensured by strict vertical transmission). In ftsZ minor differences in substitution patterns were observed between arthropod and nematode Wolbachia, only in the 3'-portion of the gene. dnaA showed comparable patterns of variation in both lineages, with evidence for strong conservation.

Animals↗
PubMed1996

An electrospray investigation on in vitro glycation of ribonuclease.

The in vitro reactions of RNase with different concentrations of glucose or fructose have been studied by means of electrospray mass spectrometry coupled with microcolumn high performance liquid chromatography. The results obtained have shown that, subsequent to the protein glycation, a series of cross-linking products are generated. Their molecular weights demonstrate that severe degradation processes of the proteic substrate takes place after the cross-linking process.

Amino Acid Sequence↗
PubMed1996

The in vitro glycation of lysozyme and the influence of buffer concentration investigated by mass spectrometry.

The non-enzymatic reactions between glucose or fructose with lysozyme, performed under pseudo-physiological conditions, have been studied by means of matrix-assisted laser desorption/ionization mass spectrometry. Phosphate buffer at concentrations of 0.05, 0.2 and 0.5 M has been employed. The formation of glycated proteins as well as of cross-linking products has been always observed. In the case of glucose, high phosphate buffer concentrations affect the glycation kinetics and promote the formation of cross-linking products. With fructose, such influence is moderate, the reaction kinetics being mainly influenced by the higher reactivity of the sugar.

Buffers↗
PubMed1995

A new effective method for the evaluation of glycated intact plasma proteins in diabetic subjects.

The molecular weights of plasma proteins from healthy subjects and from patients with well-or badly-controlled diabetes mellitus have been determined by use of a matrix-assisted laser desorption ionization method, representing a highly accurate technique for the determination of the molecular weight of large biomolecules. Using this approach, different molecular weights of human serum albumin have been found for healthy (66,572-66,694 dalton) and diabetic (66,785-68,959 dalton) subjects. Such differences can be rationalized as being due to the different number of glucose molecules condensed on the protein and/or their further oxidation products; in the case of our diabetic patients this number is in the range of 1.4-14.8. The data show the high validity and specificity of the technique, which allows us to evaluate, without any protein degradation procedure, the number of glucose molecules condensed on a specific protein and ascertain the relationship of this number to the physiopathogenetic conditions of the subjects studied.

Adult↗
PubMed1993

A study on in vitro glycation processes by matrix-assisted laser desorption ionization mass spectrometry.

The number of glucose molecules condensed on glycated bovine serum albumin have been easily determined by means of matrix-assisted laser desorption/ionization mass spectrometry. Measurements were carried out on samples from incubation of the protein with glucose at different concentrations (0.02 M, 0.2 M, 2 M and 5 M). A clear increase in molecular mass of BSA with respect to incubation time is detected. In contrast to what is observed with fluorescence, the plots of molecular mass increase vs. incubation time show the occurrence of a steady state, corresponding to the complete saturation of all the protein sites reactive against glucose. Comparison of fluorescence and molecular mass data reveals that some further reactions, different from condensation, must take place, which could be in principle either intramolecular or originated by reactivity of modified condensed glucose moieties vs. free glucose.

Glucose↗
PubMed1991

Investigation of products arising from enzymatic digestion of advanced glycated albumin by high-performance liquid chromatography/mass spectrometry.

The structural investigation of the products arising from 28 days incubation of albumin with high glucose concentration and further enzymatic hydrolysis has been carried out by means of high-performance liquid chromatography/mass spectrometry (HPLC/MS) under plasmaspray conditions. By this approach many different compounds have been detected, and for most of them, possible structures have been proposed on the basis of literature data and molecular weight assignments.

Animals↗