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M D'Erme

Publications and source records attributed to M D'Erme.

At least 19 recordsLinked to original sources
PubMed1997

Does poly(ADP-ribosyl)ation regulate the DNA methylation pattern?

The existence of a possible correlation between poly(ADP-ribosyl)ation and DNA methylation processes was investigated. In vivo and in vitro experiments were carried out on L929 mouse fibroblasts preincubated for 24 h with or without 3-aminobenzamide, a well-known inhibitor of poly(ADP-ribose) polymerase. Both experimental approaches evidenced a close relationship between these two important nuclear enzymatic mechanisms, suggesting that the poly(ADP-ribosyl)ated isoform of H1 histone and/or long and branched protein-free ADP-ribose polymers could act as protecting agents against full methylation of the CpG dinucleotides in genomic DNA.

Animals↗
PubMed1996

H1-H1 cross-linking efficiency depends on genomic DNA methylation.

Oligonucleosomal DNA preparations from condensed-inactive chromatin were examined, before and after artificial methylation by bacterial SssI methylase, for their ability to allow cooperative H1-H1 interactions under conditions of different ionic strength. Our results support the conclusion that, within the highly methylated genomic DNA, there are some CpG's whose unmethylated state is critical for chromatin folding. Circular dichroism spectra indicate that artificial overmethylation of native oligonucleosomal DNA reduces its efficiency in inducing an ordered conformation of H1 histone. Temperature melting profiles confirm on the other hand that the native and the artificially overmethylated forms of oligonucleosomal DNA are both able to bind H1 histone.

Circular Dichroism↗
PubMed1996

Specific inhibitory effect of H1e histone somatic variant on in vitro DNA-methylation process.

H1e and H1c histone variants were purified from mouse L929 fibroblasts using a reverse phase HPLC, and their effect on in vitro DNA methylation was investigated, together with their ability to bind unmethylated or methylated CpG-rich 44bp oligonucleotides. In a "physiological" range of H1:DNA ratios only H1e, at variance from H1c, was found to cause a marked inhibition of in vitro enzymic DNA methylation. It was also shown that both variants have a similar affinity in binding a methylated CpG-rich oligonucleotide, but that the binding to the same oligonucleotide in the unmethylated form occurs preferentially with H1e rather than with H1c. H1e is therefore likely to be directly involved in maintaining CpG-rich sequences in the unmethylated state.

Animals↗
PubMed1996

Autoimmunity to the GM2-1 islet ganglioside before and at the onset of type I diabetes.

Recently, the GM2-1 pancreatic islet ganglioside, proposed as a potential autoantigen in type I diabetes autoimmunity, has been biochemically characterized and found to be a novel ganglioside structure. In the present study, we aimed to determine whether an autoimmune response toward this novel islet molecule is 1) present in type I diabetes and is specifically directed against this molecule and not to gangliosides in general and 2) predictive of disease in high-risk subjects. To this end, the following patients have been studied: 1) 24 newly diagnosed type I diabetic subjects, 20 islet cell autoantibody (ICA)-negative first-degree relatives of type I diabetic subjects, and 25 age-matched normal control individuals; and 2) 31 prospectively evaluated ICA+ first-degree relatives of type I diabetic subjects who were followed for up to 10 years, during which 14 of them developed type I diabetes. A direct assay for autoantibodies to GM2-1 and to other pancreatic gangliosides (GM3, GD3, GD1a) was developed using an indirect immunoperoxidase technique performed directly on thin layer chromatography plates. Anti-GM2-1 autoantibodies (all belonging to the IgG class) were expressed in a high percentage of newly diagnosed type I diabetic subjects (71%), while no significant difference was found in the expression of antibodies directed against other pancreatic gangliosides (GM3, GD3, GD1a) among the different groups studied. Anti-GM2-1 autoantibodies were also present in ICA+ relatives (64%) (P < 0.001 vs. control subjects and ICA-relatives): in this group, life table analysis of progression to diabetes showed that anti-GM2-1 autoantibodies were significantly (P < 0.001) associated with disease, occurring in all relatives developing type I diabetes within 5 years and thus identifying a cohort of ICA+ subjects with markedly increased diabetes risk.

Autoantibodies↗
PubMed1996

[Lesions of the collateral ligaments of the ankle: diagnosis and follow-up with magnetic resonance and ultrasonography].

Acute sprains are one of the most frequent ankle conditions; the lateral collateral ligaments are often involved. Currently, plain radiography and clinical examination are the methods of choice in the management of these injuries. This study was aimed at describing the MR findings of acute ankle sprains, to assess which ligaments are involved, to study the repair process during conservative treatment and, finally, to compare MR and US findings in acute and chronic injuries. We divided our study into a prospective and a retrospective parts. In the prospective study, MRI was performed in 20 consecutive patients with acute ankle sprain diagnosed at the emergency care unit of our institute and treated conservatively with braces. The patients with fractures were excluded. Follow-up was based on a series of MR exams performed every 30 days for 6 months. We diagnosed 18 injuries of the lateral collateral ligaments, 5 of the anterior talofibular ligament (ATFL) (2 partial and 3 complete tears) and 13 of both the ATFL and the calcaneofibular (CFL) (6 partial and 7 complete tears). The follow-up showed complete edema resorption at 30 days in 2 patients with no ligament injuries; the persistence of a medium-large amount of fluid in partial tears at 30 days and its complete resorption at 60 days; and, finally, the persistence of a medium-large amount of fluid at 180 days in 2 complete tears. No scar could be identified in all the patients with ligament injuries. The retrospective study was based on the comparison of MR (gold standard) and US findings in 78 patients with ankle sprain, 28 in the acute and 50 in the chronic phase. In the first group we found 9 ATFL injuries (6 partial and 3 complete tears), 5 ATFL and CFL injuries (3 partial and 2 complete tears), 2 complete tears of lateral collateral ligaments, 3 deltoid ligament (DL) injuries, 2 ATFL and DL injuries and 2 injuries of both lateral and medial collateral ligaments. US was in agreement with MRI in 85% of ATFL, 67% of CFL and 28% of DL injuries; US also yielded 2 false positives in PAA. In the second group of 50 patients, MRI showed 11 ATFL and 8 ATFL and CFL injuries, 3 injuries of lateral collateral ligaments, 6 DL and 8 ATFL, CFL and DL injuries and 5 complete tears of both internal and external collateral ligaments; 10 exams were negative. US had 58% agreement with MRI in ATFL, 46% in CFL and 21% in DL injuries. In this series, US yielded 3 false positives in PAA injuries.

Adolescent↗
PubMed1995

Does hypomethylation of linker DNA play a role in chromatin condensation.

The inhibitory effect that H1 histone exerts on the in vitro DNA methylation process, catalysed by mammalian DNA methyltransferase, together with the relative hypomethylation of linker DNA in eukaryotic cells chromatin, suggest that this hypomethylated state of linker DNA can be of importance in allowing or regulating H1-dependent chromatin condensation. In native oligonucleosomes (olnu), i.e., in chromatin fragments consisting of 5-20 nucleosomes each, there was a correlation between the effects of H1 on the DNA ellipticity at 280 nm and the in vitro assayed methyl-accepting ability. The same was true in H1-depleted or in H1-reconstituted preparations. Artificial methylation caused olnu DNA to lose its ability to allow cooperative H1-H1 interactions under ionic strength conditions similar to those known to affect the transition of the 10-nm filament to the 30-nm chromatin fiber. These results suggest that hypomethylation of linker DNA plays a role in the H1-H1 interactions that are needed for solenoid condensation.

Animals↗
PubMed1995

Specific variants of H1 histone regulate CpG methylation in eukaryotic DNA.

Upon HPLC fractionation of human placenta or calf thymus H1 histone preparations, only some fractions enriched in the H1e-c variants were able to exert a severe inhibition on in vitro enzymatic DNA methylation. These fractions, though similar to the other variants in interacting with genomic DNA, were also the only ones which could bind CpG-rich ds-oligodeoxyribonucleotides (oligos). Both the 6-CpG ds-oligo and the DNA purified from chromatin fractions enriched in 'CpG islands' were good competitors for the binding of H1e-c to the 6meCpG ds-oligo. This ability to bind any DNA sequence and to suppress the enzymatic methylation in any sequence containing CpG dinucleotides suggests, for these particular H1 variants, a possible role in maintaining CpG island DNA and linker DNA at low methylation levels.

Animals↗
PubMed1995

Binding of histone H1e-c variants to CpG-rich DNA correlates with the inhibitory effect on enzymic DNA methylation.

Within the H1 histone family, only some fractions enriched in the H1e-c variants are effective in causing a marked inhibition, in vitro, of enzymic DNA methylation and, in gel retardation and Southwestern blot experiments, in binding double-stranded (ds) CpG-rich oligonucleotides. Both the 6-CpG ds-oligonucleotide and the DNA purified from chromatin fractions enriched in 'CpG islands' are good competitors for the binding of H1e-c to 6-meCpG ds-oligonucleotide. Because of their ability to bind any DNA sequence and to suppress the enzymic methylation in any sequence containing CpG dinucleotides, these particular H1 variants could play some role in maintaining linker DNA at low methylation levels and even in preserving the unmethylated state of the CpG-rich islands which characterize the promoter regions of housekeeping genes.

Animals↗
PubMed1995

GM2-1 pancreatic islet ganglioside: identification and characterization of a novel islet-specific molecule.

Recent studies have indicated that GM2-1, a pancreatic islet monosialo-ganglioside, is an islet-specific component whose expression is metabolically regulable and represents one of the target antigens of cytoplasmic islet cell antibodies. In the present study we aimed to biochemically characterize this molecule using a panel of biochemical techniques including gas chromatography, thin layer chromatography, enzymatic digestion and mass spectrometry. GM2-1 ganglioside was extracted from human pancreas and purified by thin-layer chromatography. Fatty acids in the ceramide (the hydrophobic portion of the molecule), identified by gas chromatography ranged from C16:1 to C24:1. The oligosaccharide chain was enzymatically digested by the sequential application of various exoglycosidases (neuraminidase followed by beta-galactosidase, followed by beta-hexosaminidase) and characterized by gas chromatography identification of the liberated sugars. The following structure was deducted from enzymatic studies and confirmed by mass spectrometry analysis: N-acetyl neuraminic acid-galactose-galactosamine-galactosamine-glucose-ceramide. This is a novel ganglioside structure, not yet described, which shares characteristics with a neuronal glycolipid autoantigen: the LM1 ganglioside. Both GM2-1 and LM1 have a single sialic acid residue in the terminal position, the same migration position on thin layer chromatography and the same number of carbohydrate moieties. In conclusion, we have characterized a novel islet-specific ganglioside molecule with unusual characteristics, such as the terminal sialic acid and the galactosamine residues, which may facilitate both its antigenicity and its involvement in beta-cell autoimmunity.

Carbohydrate Sequence↗
PubMed1994

Histone-induced condensation of rat testis chromatin: testis-specific H1t versus somatic H1 variants.

Due the likely role of H1 histone variants in inducing the formation of folded DNA filaments with different stabilities, the condensing capacity of the testis-specific H1t versus the somatic variants was tested. Circular dichroism analyses of rat testis H1-depleted oligonucleosomes (5-2kbp) revealed that H1t, which appears in germ cells during the meiotic prophase of mammalian spermatogenesis, exerts the lowest condensing effect as compared to the other variants. The distribution of H1 subtypes among different chromatin fractions was also investigated and gave evidence that H1t is more abundant in chromatin regions which are more sensitive to DNAase I digestion.

Animals↗
PubMed1994

Characteristics of proteinuria in experimental diabetes mellitus.

An impairment of protein charge selectivity has been invoked to explain the initial anionic proteinuria in diabetic nephropathy. The aims of this work were to investigate charge and size protein perm-selectivity abnormalities in experimental diabetes and to monitor these changes over time after diabetes induction. Diabetes was induced in 56 Sprague-Dawley male rats by streptozotocin; the control group was represented by 38 normal rats. Blood glucose, body weight, urine volumes, and proteinuria in 24-h urine collections were evaluated at 3, 6, 9, and 12 months of diabetes. The Bradford method and mono- and bidimensional gel electrophoresis were used to determine and characterize proteinuria. Body weight increase was lower (P < 0.05, P < 0.0001, P < 0.05 at 3, 6, and 12 months, respectively), urine volumes were greater (P < 0.001, P < 0.005, P < 0.05 at 6, 9, and 12 months, respectively) and the proteinuria was significantly increased (P < 0.05 at 3 months, P < 0.001 at 6 months, P < 0.01 at 9 months, and P < 0.05 at 12 months) in diabetic rats compared with the control group. When the charge and the size of urine proteins were considered, small (30 kDa) and anionic proteins were found to be mainly excreted in diabetic rats, at 3 months of the disease; at 6 months, higher amounts of albumin and cationic proteins with higher molecular weight (50 kDa) were also found in the urine; at 9 and 12 months the changes previously described were associated with an excretion of proteins weighing about 75 kDa.(ABSTRACT TRUNCATED AT 250 WORDS)

Albuminuria↗
PubMed1993

Inhibition of CpG methylation in linker DNA by H1 histone.

H1 exerts a specific in vitro inhibitory effect on enzymic DNA methylation. The experiments reported in this paper were undertaken in order to assess whether the lower methylation level found in internucleosomal DNA compared to core DNA is the in vivo consequence of the well-known localization of this histone in the linker region, as opposed to a possible deficiency of CpG dinucleotides in linker DNA. The methyl-accepting ability of H1-depleted oligonucleosomes from human placenta and of the corresponding core particles were assayed by addition of purified DNA methyltransferase, using S-adenosylmethionine as the methyl group donor. We have found that approx. 80% of newly-incorporated methyl groups are localized in linker DNA, which is indeed a good potential substrate for enzymic DNA methylation. Addition of quasi-physiological amounts of H1 to H1-depleted oligonucleosomes markedly reduced their methyl-accepting ability, while exerting a re-condensing effect on these particles, as revealed by the distortions of their circular dichroism spectra.

Chromatin↗
PubMed1993

Effect of H1 histone isoforms on the methylation of single- or double-stranded DNA.

The loosely and tightly bound H1 histone isoforms were shown to exert, on the in vitro methylation of linker DNA in H1-depleted oligonucleosomes, inhibitory or activating effects respectively similar to those previously shown in the methylation of Micrococcus luteus dsDNA. When assayed on the enzymic methylation of Micrococcus luteus ssDNA, addition of the tightly bound one resulted in a stimulation similar to that exerted on double-stranded bacterial DNA or on linker DNA from mammalian chromatin, while the loosely bound isoform had no effect whatsoever. The transformation of the "typical" loosely bound H1 isoform into its tightly bound counterpart can be visualized as being an essential event in the modulation of DNA methylation process in eukaryotic chromatin.

Cell Nucleus↗
PubMed1992

[Magnetic resonance and arthroscopy of the knee. A double-blind study in 40 patients].

To evaluate the capabilities of ultra-low-field MR for the high-resolution imaging of the knee with a short acquisition time, a prospective double-blind study was carried out on 40 consecutive patients with acute or chronic articular conditions who were examined with both MR imaging and arthroscopy. Three-dimensional gradient-echo MR sequences were employed which allow many thin high-resolution slices to be obtained in a relatively short time. To evaluate the results arthroscopy, performed the day after MR imaging, was considered the gold standard. MR imaging and arthroscopy were in agreement in 84.6% of meniscal tears with 91.6% sensitivity and 80% specificity, in 82% of anterior cruciate ligament lesions with 100% sensitivity and 80% specificity and in 81% of cartilage lesions with 100% sensitivity and 61% specificity. On the whole, MR imaging and arthroscopy were in agreement in 82.5% of cases with 97.2% sensitivity and 75.3% specificity. MR imaging gave more information about collateral ligament, muscle and bone involvement. These results confirm the capabilities of ultra-low-field MR imaging in the study of the knee: the technique allows diagnostic studies to be performed in a short time, at a low cost, and with similar results to those obtained with higher field strengths.

Anterior Cruciate Ligament↗
PubMed1992

[Normal anatomy and findings in traumatic pathology of the popliteal system. A MR study].

To date, the lesions of the popliteal system, which are responsible for the so-called postero-lateral knee instability, are still an imperfectly known chapter of knee conditions. We retrospectively analyzed 215 consecutive MR examinations performed May-August 1991 to evaluate MR capabilities in correctly depicting both the normal anatomy and the pathologic conditions of the popliteal system. Using our standard protocols for knee study and two different magnets (0.064 and 0.5 T), we identified 23 lesions of the popliteus and of its meniscal and peritoneal insertions, and 17 lesions involving also other capsular and ligamentous structures of the knee. Coronal T1-weighted images were the best ones to correctly identify normal knee anatomy, whereas sagittal T2-weighted images were more sensitive in detecting popliteal lesions. Our results had clinical or surgical confirmation in all cases.

Humans↗
PubMed1991

Histones and DNA methylation in mammalian chromatin. II. Presence of non-inhibitory tightly-bound histones.

After removal, by high-salt extraction, of the loosely-bound components present in human placenta chromatin, tightly-bound cationic proteins could be solubilized, by acid extraction, from the 'stripped' chromatin, as well as from the 'stripped' loops or from the 'digested matrix'. These acid-soluble tightly-bound proteins are, in terms of apparent molecular mass and immunoreactivity, quite similar to the 'typical', loosely-bound histones, and, similarly to their 'loosely-bound' counterparts, they can be subdivided in distinct H1-, H2A-, H2B-, H3- and H4-like components, the 'digested matrix' being however characterized by the absence of tightly-bound H1. These tightly-bound histones, at variance from the 'typical' ones, readily find a right-handed helical conformation upon renaturation by progressive dialyses. The H1 components strongly differ also in their effects on enzymic DNA methylation: while 'typical' H1 has a strong inhibitory effect, its tightly-bound counterpart exerts a slight but definite stimulation.

Chromatin↗
PubMed1991

Histones and DNA methylation in mammalian chromatin. Differential inhibition by histone H1.

Histones (from calf thymus or from human placenta), if renatured in the presence of EDTA, caused a severe inhibition of in vitro methylation of double-stranded DNA (from Micrococcus luteus) by human placenta DNA methyltransferase. The absence of EDTA during the histone renaturation procedure abolished--at least in the 'physiological' range of the histones/DNA ratio--the inhibition. The H1 component was responsible for this inhibition, no effect being exerted by the other histones. H1 preparations were more effective if renatured in the presence of EDTA--90% inhibition being reached at a 0.3:1 (w/w) H1/DNA ratio. It seems likely that the requirement for the presence of EDTA during the renaturation process is correlated to its ability to induce a fairly stable ordered conformation of the histones, although this effect could also be shown with the 'inactive' H2a, H2b and H3 components, and was instead less evident with histone H1. The restriction to histone H1 of the ability to inhibit enzymic DNA methylation may account for the lower methylation levels present in the internucleosomal DNA of mammalian chromatin.

Animals↗