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Biomedical subjects

R Ammendola

Publications and source records attributed to R Ammendola.

At least 19 recordsLinked to original sources
PubMed2001

Regulation of p21waf1/cip1 expression by intracellular redox conditions.

Reactive oxygen species (ROS) have been considered for a long time only as molecules for inducing oxidative damage to proteins, lipids, and nucleic acids. However, in the last few years some physiological effects of ROS have been hypothesized, consisting of the redox regulation of several biological processes, including the transduction of mitogenic signals. This means that intracellular generation of ROS could be necessary to maintain homeostasis, as well as that their formation/scavenging should be controlled processes. We developed an experimental procedure that causes redox perturbations in intact cells, based on the exposure of living cells to diethylmaleate (DEM), a GSH-depleting agent. By this procedure we demonstrated that ROS generated following DEM treatment induces a G1 arrest, that is accompanied by several redox-dependent changes in cell cycle-related proteins. One of these is the p53-independent accumulation of p21waf1/cip1, which requires the integrity of the ras-MAPK pathway. Accordingly, DEM treatment strongly activates ERK2. On the other hand, redox perturbations provoked by DEM induce several early phenomena, including p21waf1/cip1 and Rb dephosphorylation.

Animals↗
PubMed1998

Chronic unexplained liver disease in children with primary immunodeficiency syndromes.

Liver disease may be found in patients with primary immunodeficiency syndromes because of the high risk of infection with hepatotropic viruses related to the treatment with blood derivatives. The prevalence of liver disease in these patients and its etiology, however, is still not completely understood. We have evaluated the prevalence and the etiology of liver disease in children with different forms of primary immunodeficiencies. Thirty patients included in the study underwent molecular studies to detect common hepatotropic viruses, including hepatitis C and G viruses. Liver involvement was found in 11 of 30 (36.6%) patients. All patients with liver disease had deficiencies of specific immunity, with a prevalence in this subgroup of 47.8%. Liver disease was more severe in patients with T and B cell combined immune disorders than in those with a selective T cell immunodeficiency. Moreover, the severity of the disease correlated with an overall more rapid fatal outcome. A viral etiology was found in only six of these patients, whereas in the remaining five patients, no cause of liver injury was identified. In the virally infected patients, hepatitis C virus was the most common viral agent. In patients with immunodeficiencies, there is a high prevalence of liver disease not fully explained on the basis of the common viral infections.

Adolescent↗
PubMed1996

Prolonged and high dose recombinant interferon alpha-2b alone or after prednisone priming accelerates termination of active viral replication in children with chronic hepatitis B infection.

BACKGROUND: There is no generally accepted treatment for chronic hepatitis B (HB) infection in children. OBJECTIVES: To evaluate the efficacy of a prolonged course of high dose interferon alone or after prednisone priming in children with chronic HB infection. METHODS: The outcome of 31 children with HB e antigen (HBeAg)-positive chronic hepatitis who randomly received either no treatment (n = 9) or 10 million units of interferon alpha-2b/m2, alone (n = 13) or after prednisone priming (n = 9), three times weekly for 1 year was studied. RESULTS: One patient withdrew from treatment. By the end of the first year treatment induced a loss of HB virus DNA and HBeAg from serum in 10 of 21 patients (48%), and a loss of HB surface antigen (HBsAg) in 4 (19%). Alanine aminotransferase values became normal in one patient (4.8%). Response rates in the two groups of treated patients were similar. In controls only one patient lost HBeAg and HBV DNA (11%; P = 0.05), and none lost HBsAg or showed alanine aminotransferase normalization (P = 0.21 and 0.70, respectively). After a posttreatment 2-year follow-up there were still no differences in the response rates of the two treatments; of the 21 pooled treated patients, 61% lost HBeAg and DNA and 67% normalized alanine aminotransferase (vs. 33 and 44% of controls, respectively; P = 0.32 and 0.40). Reversion to HBeAg and HBV DNA negativity in treated patients occurred significantly earlier (P = 0.02 and 0.006, respectively) than in controls. No further patient lost HBsAg, but one reacquired HBsAg. Treated patients had posttreatment histologic scores better than controls (P = 0.03). CONCLUSIONS: Our medium term follow-up results indicate that a prolonged course of high dose interferon in children with chronic HB infection, regardless of prednisone priming, poorly affects response rates but significantly speeds termination of active viral replication.

Adolescent↗
PubMed1995

A p53-independent pathway for activation of WAF1/CIP1 expression following oxidative stress.

Incubating human cells in diethylmaleate (DEM) depletes the intracellular pool of reduced glutathione (GSH) and increases the concentration of oxidative free radicals. We found that DEM-induced oxidative stress reduced the ability of p53 to bind its consensus recognition sequence and to activate transcription of a p53-specific reporter gene. Nevertheless, DEM treatment induced expression of WAF1/CIP1 but not GADD45 mRNA. The fact that N-acetylcysteine, a precursor of GSH that blocks oxidative stress, prevented WAF1/CIP1 induction by DEM suggests that WAF1/CIP1 induction probably was a consequence of the ability of DEM to reduce intracellular GSH levels. DEM induced WAF1/CIP1 expression in Saos-2 and T98G cells, both of which lack functional p53 protein. DEM treatment did not produce an increase in membrane-associated protein kinase C, but ERK2, a mitogen-activated protein kinase, was phosphorylated in a manner consistent with ERK2 activation. DEM treatment also produced a dose-dependent delay in cell cycle progression, which at low concentrations (0.25 mM) consisted of a G2/M arrest and at higher concentrations (1 mM) also involved G1 and S phase delays. Our results indicate that oxidative stress induces WAF1/CIP1 expression and arrests cell cycle progression through a mechanism that is independent of p53. This mechanism may provide for cell cycle checkpoint control under conditions that inactivate p53.

Animals↗
PubMed1995

Negative and positive elements in the promoter region of the human apoferritin L gene.

We have characterized the promoter of the human gene coding for the apoferritin L subunit. Transient transfections of 5' and 3' deletion mutants indicate that the efficiency of the L promoter depends on both negative and positive cis-elements, located upstream and downstream of the transcription start point. DNaseI footprinting analysis of this DNA region revealed the presence of five protected segments. The most upstream one (element 1) corresponds to the negative cis-element and is recognized by factor(s) sharing a GC-sequence specificity. Three positive elements are in the region upstream of the start of transcription; a fifth positive cis-element (element 5) is localized in the first exon of the L gene.

Apoferritins↗
PubMed1995

Differentially expressed mRNAs as a consequence of oxidative stress in intact cells.

Intracellular redox conditions influence the activity of several transcription factors leading to a modulation of the expression of the genes controlled by these factors. We examined the changes in cell transcription patterns after oxidative stress induced by diethylmaleate (DEM). Using the differential display technique we identified several differentially expressed sequence tags, four of which are identical or highly homologous to sequences contained in the human cDNAs encoding vimentin, c-fos, cytochrome oxidase IV and ribosomal protein L4; another one corresponds to a transcript of the mitochondrial genome of unknown function. The remaining five cDNAs are not recorded in any sequence data bank. One of these, named Rox3, lights up two mRNA species of approximately 3400 and 3600 bp, significantly increased after treatment with DEM or with other oxidizing agents. This increase appears precociously after exposure to DEM and it is completely prevented by pretreatment with N-acetylcysteine. The Rox3 fragment was used to screen a cDNA library; one fully sequenced clone showed 100% homology with the putative human guanine nucleotide regulatory protein nep1.

Cell Line↗
PubMed1994

The DNA-binding efficiency of Sp1 is affected by redox changes.

We have previously demonstrated that the DNA-binding efficiency of Sp1 is greatly decreased in nuclear extracts from 30-month-old rat tissues compared to those from young ones, although its gene appears to be normally expressed. As reactive oxygen intermediates are known to accumulate in aged animals, we investigated the effect of oxidation on the Sp1 DNA-binding activity. Electrophoretic mobility shift assays and DNase I footprintings showed that high concentrations of dithiothreitol, added to the aged tissue extracts, fully restore the Sp1 DNA-binding efficiency. However, in young nuclear extracts hydrogen peroxide treatment strongly decreases the Sp1 DNA-binding activity that is restored by the treatment with high dithiothreitol concentrations. To ascertain whether the oxidative stress is directed toward the Sp1 molecule alone, or whether it acts on unknown Sp1 cofactor(s) necessary for DNA binding, we purified Sp1 from young rat liver and demonstrated that when the purified protein is added to aged nuclear extracts, it efficiently binds to its DNA cis-element. Moreover, purified Sp1 treated with hydrogen peroxide lost its ability to bind its cis-element and the DNA-binding efficiency was fully restored after incubation with dithiothreitol.

Aging↗
PubMed1993

Immortalization of a cell line showing some characteristics of the oligodendrocyte phenotype.

We have used the polyoma middle T oncogene to immortalize cells from rat embryo encephalon. Immunostaining experiments with monoclonal antibodies demonstrated that the cells of one of the obtained lines, named CEINGE CL3, are stained by anti-vimentin and anti-S100 antibodies, are not stained by anti-neurofilaments (NF) or anti-glial fibrillary acidic-protein (GFAP) antibodies. Only a subset of the CEINGE CL3 cells (20-30%) is stained by an anti-galactocerebroside antibody. Northern blot analysis demonstrated that these cells express low levels of proteolipid protein mRNA, whereas polymerase chain reaction (PCR) amplification failed to evidentiate the presence of both NF and GFAP mRNAs. Either retinoic acid or forskolin treatments or a combination of them are able to induce morphological changes that are accompanied by a complete growth arrest.

Animals↗
PubMed1992

Sp1 DNA binding efficiency is highly reduced in nuclear extracts from aged rat tissues.

To explore the role of transcriptional factors in the genesis of the senescent phenotype, nuclear extracts from 4- and 30-month-old rat brains were analyzed for the presence of DNA-binding proteins able to interact with double-stranded oligonucleotides containing recognition sites for sequence-specific DNA-binding factors. Gel shift assays revealed that the DNA-binding efficiency of Sp1 is significantly reduced in aged animals compared to young ones, whereas CTF/NF1 and AP1 from young and old rat nuclear extracts bind their DNA targets with the same efficiency. The quantitative analysis of Sp1 by immunoblotting indicated that equivalent quantities and degrees of heterogeneity of Sp1 protein are present in both nuclear extracts, suggesting that the observed difference is not due to a different expression of this transcriptional factor. DNase I footprinting of the heavy chain ferritin gene promoter, which contains a Sp1 binding site, demonstrated that the nuclear extract from 30-month-old rat brain does not protect the region involved in the regulation of the H ferritin gene by Sp1. This results in a reduction of about 50% of the expression of the H ferritin mRNA in aged rat brains. Furthermore, the Sp1 binding sites present in the SV40 early promoter are not protected in a DNase I footprinting assay where a nuclear extract from 30-month-old rat brain was used as a source of DNA binding proteins. Liver nuclear extracts prepared from young and aged rats demonstrated that a decrease of Sp1 binding efficiency is similarly present in this tissue.

Aging↗
PubMed1991

A rat brain mRNA encoding a transcriptional activator homologous to the DNA binding domain of retroviral integrases.

We have isolated a rat cDNA, named FE65, hybridizing to an mRNA of about 2,300 nucleotides present in rat brain, undetectable in rat liver and very poorly represented in other tissues. An mRNA of the same size is present in human neuroblastoma cells and is absent from other human cell lines. The FE65 cDNA contains an open reading frame (ORF) coding for a polypeptide of 499 amino acids in which 143 residues can be aligned with the DNA binding domain of the integrases encoded by mammalian immunodeficiency viruses. The remaining part of the FE65 ORF is not homologous with the correspondent regions of the integrases; the first 206 residues of the FE65 ORF show numerous negative charges and a short sequence not dispensable for the function of the transactivating acidic domain of the jun family transcriptional factors. A plasmid which expresses FE65 amino acids 1-232 fused to the yeast GAL4 DNA binding domain was co-transfected with a plasmid containing five GAL4 binding sites upstream of a minimal Adenovirus promoter controlling the expression of the CAT gene. This experiment showed that the fused protein GAL4-FE65 is able to obtain a 30-40 fold increase of the CAT gene expression compared to the expression observed in the presence of the GAL4 DNA binding domain alone. Two types of FE65 mRNA are present in rat brain, differing only for six nucleotides. We demonstrate that this is the consequence of a neuron-specific alternative splicing of a six-nucleotide miniexon, which is also present in the human genome, in an intron/exon context very similar to that of the rat FE65 gene.

Amino Acid Sequence↗
PubMed1990

Mapping of the gene TCF2 coding for the transcription factor LFB3 to human chromosome 17 by polymerase chain reaction.

A human clone corresponding to the gene for the DNA-binding factor LFB3, a protein highly homologous to the liver-specific transcription factor LFB1, has been isolated and partially sequenced. This gene is designated TCF2. Oligonucleotide primers have been designed for LFB3 and used to amplify specifically the human gene in human/rodent somatic cell hybrids using the polymerase chain reaction. By this means, the human LFB3 gene has been mapped to the long arm of chromosome 17, between the centromere and the APL breakpoint.

Animals↗
PubMed1990

Transcription of the promoter of the rat NF-1 gene depends on the integrity of an Sp1 recognition site.

The transcription start site and promoter of the rat gene coding for the transcription factor NF-1 have been identified. The NF-1 promoter was fused to the chloramphenicol acetyltransferase-coding sequence, and the resulting plasmid was transcriptionally active in the HepG2 cell line. Footprinting and gel retardation analysis indicated that the transcription factor Sp1 binds to the NF-1 promoter. Mutants in the Sp1-binding site displayed a strong reduction in transcriptional activity.

Animals↗
PubMed1990

Isolation of cDNA fragments hybridizing to rat brain-specific mRNAs.

A cDNA minilibrary in pUC18 has been generated from 3-month-old rat brains. Two hundred clones were randomly selected and sequenced. Comparison with a nucleic acid and protein data bank revealed a number of cDNA fragments not homologous to any published sequence. Northern blot analyses of some of these clones yielded 5 brain-specific cDNA fragments. The full-length cDNA for one of these clones has been isolated and completely sequenced. It corresponds to an mRNA of about 1,500 nucleotides, which is present in brain and, to a lesser extent, in heart and skeletal muscle. Its expression is developmentally regulated in the rat brain from 14-day embryos to 3-month-old adults. A very recent comparison with the EMBL nucleotide sequence data bank showed that this mRNA codes for a brain-specific snRNP-associated protein.

Aging↗
PubMed1987

The transcriptional efficiency of clustered tRNA genes is affected by their position within the cluster.

The transcription of a mouse genomic segment containing four tRNA genes, coding for a tRNA(Ala), a tRNA(Ile), a tRNA(Pro) and a tRNA(Lys), has been studied in a HeLa cell extract, demonstrating that differences among their transcriptional efficiencies are evident using as templates either the natural cluster or an equimolecular mixture of the four isolated genes. Nevertheless, the structure of the cluster influences the transcriptional efficiency of the clustered genes. In fact, a cis-acting inhibitory sequence has been located at about 400 bp downstream of the tRNA(Pro) coding sequence. Moreover rearrangements of the reciprocal position of the various tRNA genes within the cluster results in significant changes in the transcriptional rates of the individual transcriptional units.

Animals↗
PubMed1986

Structure and in vitro transcription of tRNA gene clusters containing the primers of MuLV reverse transcriptase.

Three genes coding for mouse tRNAPro have been isolated from a genomic library and characterized both structurally and functionally. Two of these (tPro52 and tPro53) code for the tRNA primer of reverse transcriptase of MuLV. The third one (tPro51) shows several differences (mutations and deletions) that probably prevent the folding of the matured transcript into the cloverleaf structure, and is therefore a pseudogene. This pseudogene gives rise to a RNA transcription product in vitro. tPro52 is clustered with a tRNALys gene and with a tRNAAla gene, which is strongly homologous to the rat identifier repeated sequence. tPro53 is clustered with a tRNAAsp and a tRNAGly gene. Other tRNA-hybridizing sequences are present in the lambda clones that contain tPro51 and tPro53.

Anticodon↗