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F Esposito

Publications and source records attributed to F Esposito.

At least 73 records · Page 4Linked to original sources
PubMed1997

Redox-mediated regulation of p21(waf1/cip1) expression involves a post-transcriptional mechanism and activation of the mitogen-activated protein kinase pathway.

p21(waf1/cip1) gene expression is induced by DNA damage in cells with wild-type p53 and contributes to the arrest of cell growth. It was demonstrated that under many experimental conditions, including oxidative stress, p21(waf1/cip1) expression can be induced through p53-independent pathways. Since most of these experimental conditions induce the phosphorylation of mitogen-activated protein kinase (MAPK) and thus its activation, we evaluated p21(waf1/cip1) mRNA levels in cells exposed to an oxidative stress, induced by diethylmaleate (Et2Mal), and in which the MAPK pathway was blocked. The expression of a dominant-negative mutant of MEK, the MAPK kinase that phosphorylates and activates MAPK, and of a dominant-negative [Asn17]Ras mutant prevented the Et2Mal-induced accumulation of p21(waf1/cip1) mRNA. Similarly, the expression of MEK- and of [Asn17]Ras mutants decreased the 12-O-tetradecanoyl-phorbol 13-acetate (TPA)-mediated p21(waf1/cip1) induction. Furthermore, TPA-induced and serum-induced p21(waf1/cip1) mRNA accumulation was blocked by pretreating the cells with the antioxidant compound N-acetylcysteine, suggesting that oxidative stress is involved in these responses. p21(waf1/cip1) mRNA levels reached a maximum within 2 h of adding Et2Mal or TPA; however, the rate of transcription from a p21(waf1/cip1)-promoter construct did not increase during this period. In contrast, cells treated with actinomycin D show an increase of p21(waf1/cip1) mRNA stability after Et2Mal treatment. This result suggests that the increase in p21(waf1/cip1) mRNA at early times results from post-transcriptional regulatory events. Longer exposure to TPA may activate p21(waf1/cip1) gene transcription through an Sp1-dependent mechanism, while Et2Mal treatment gradually inhibits p21(waf1/cip1) gene transcription through oxidative changes that affect Sp1 binding to DNA.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1997

Electrically-elicited surface mechanomyogram in myotonic dystrophy.

The surface oscillation of the muscle during electrical stimulation is detectable by an accelerometer as a surface mechanomyogram (MMG). The aim of this study was to evaluate whether MMG properties reflect the mechanical muscle changes induced by myotonic dystrophy (MyD). To this end, the tibialis anterior of seven MyD patients and seven age- and sex-matched controls (C) was supramaximally stimulated at 1 (single twitches), 5, 10, 15, 20 Hz for 3 s at the most proximal motor point. RESULTS SINGLE TWITCHES: The MMG amplitude was 67% less, the duration 37% longer, the electromechanical delay 64% longer, and the spectrum mean frequency, 44% lower in the MyD patients than in controls. REPETITIVE STIMULATION: At each stimulation frequency, the average MMG peak-to-peak was less in the MyD patients than in C. CONCLUSION: The differences between the MMGs of MyD patients and C support the hypothesis that, together with the well-known changes in sarcolemmal excitability, an alteration in electromechanical coupling and a failure in contractile machinery may coexist in MyD.

Biomechanical Phenomena↗
PubMed1997

Do insecticide-treated curtains reduce all-cause child mortality in Burkina Faso?

To evaluate whether insecticide-treated netting (ITN) reduces child mortality in different epidemiological settings, 4 large, randomized, controlled trials were conducted in Africa. Here we report the findings from the trial in Burkina Faso, in an area of hyperendemic and markedly seasonal malaria transmission. The trial involved 158 villages, with a total population of some 90,000, grouped into 16 geographical clusters. Ascertainment of mortality among children aged 6-59 months began in early 1993. In June/July 1994, 8 of the clusters, randomly selected, received permethrin-treated curtains. Follow-up of children and ascertainment of mortality continued until May 1996. A 15% reduction in all-cause mortality among children aged 6-59 months was observed over the 2-year period following the installation of the curtains (95% c.i. -4% to 30%). In the first year, post-intervention mortality was substantially lower in the clusters receiving curtains compared with the control clusters (rate ratio = 0.74; 95% c.i. 0.57, 0.95) but in the second year, there was no difference between mortality in the two groups (rate ratio = 0.99). The overall two-year impact of the intervention is consistent with the impacts observed in other trials which have demonstrated reductions in child mortality of from 17% to 33%. However, the year-by-year analysis raises some concerns about the long-term effect of ITN. Further follow-up of this population is warranted.

Burkina Faso↗
PubMed1997

Wild isolates of Plasmodium falciparum malaria show decreased sensitivity to in vitro inhibition of parasite growth mediated by autologous host antibodies.

Antigenic diversity in field populations of Plasmodium falciparum parasites may delay the acquisition of protective immunity to malaria, the development of which may thus require repeated exposure to infection over a prolonged period of time. In this study we show that P. falciparum parasites may vary in their sensitivity to antibody-mediated invasion/growth inhibition in vitro. Wild isolates of P. falciparum from children living in an endemic area of Burkina Faso were tested for their sensitivity to the growth inhibitory effects of antibodies originating from the same (autologous) and from other donors (heterologous). A significantly lower invasion inhibition activity was obtained when the isolates and antibodies were tested in autologous compared with heterologous combinations. The lower sensitivity to growth inhibition by autologous antibodies may be due to immune pressure in vivo, selecting from a heterogeneous parasite population those with a low expression of the antigens recognized by the host's antibodies. Alternatively, the parasites cultured from each child might represent expanding parasite populations, mainly constituting strains not earlier seen by the immune system of that specific host. The results reinforce the concern about Plasmodium antigenic diversity as a major obstacle towards the development of an effective malaria vaccine.

ABO Blood-Group System↗
PubMed1996

Different response to Plasmodium falciparum malaria in west African sympatric ethnic groups.

The comparison of malaria indicators among populations that have different genetic backgrounds and are uniformly exposed to the same parasite strains is one approach to the study of human heterogeneties in the response to the infection. We report the results of comparative surveys on three sympatric West African ethnic groups, Fulani, Mossi, and Rimaibé, living in the same conditions of hyperendemic transmission in a Sudan savanna area northeast of Ouagadougou, Burkina Faso. The Mossi and Rimaibé are Sudanese negroid populations with a long tradition of sedentary farming, while the Fulani are nomadic pastoralists, partly settled and characterized by non-negroid features of possible caucasoid origin. Parasitological, clinical, and immunological investigations showed consistent interethnic differences in Plasmodium falciparum infection rates, malaria morbidity, and prevalence and levels of antibodies to various P. falciparum antigens. The data point to a remarkably similar response to malaria in the Mossi and Rimaibé, while the Fulani are clearly less parasitized, less affected by the disease, and more responsive to all antigens tested. No difference in the use of malaria protective measures was demonstrated that could account for these findings, and sociocultural or environmental factors do not seem to be involved. Known genetic factors of resistance to malaria did not show higher frequencies in the Fulani. The differences in the immune response were not explained by the entomological observations, which indicated substantially uniform exposure to infective bites. The available data support the existence of unknown genetic factors, possibly related to humoral immune responses, determining interethnic differences in the susceptibility to malaria.

Adolescent↗
PubMed1996

Inhibition of feline immunodeficiency virus infection in vitro by envelope glycoprotein synthetic peptides.

Sixty-six 20- to 23-amino-acid synthetic peptides, partially overlapping by 10-12 amino acids, spanning the entire sequence of the envelope SU and TM glycoproteins of the Petaluma isolate of FIV, have been used to investigate the Env domains involved in viral infection. Peptides 5 to 7, spanning amino acids 225E-P264 located in a conserved region of the SU protein, and peptides 58 to 61, spanning amino acids 767N-P806 and encompassing hypervariable region 8 of TM protein, exhibited a remarkable and specific antiviral effect against the homologous and one heterologous isolate, as judged by inhibition of FIV-induced syncytium formation and p25 production in CrFK cells. Peptides 5 and 7, but not peptides 58 and 59, also inhibited viral replication of a fresh FIV isolate on nontransformed lymphoid cells. By flow cytometry, peptides 5, 7, 58, and 59 were shown to bind the surface of FIV permissive cells. The antiviral activity of peptides 5 and 7, however, was time-dependent, as inhibition of FIV replication was seen when the peptides were administered before or within 3 hr after virus inoculation; in contrast, TM peptides 58 and 59 exerted a potent inhibitory effect when added up to 24 hr after virus inoculation. Circular dychroism analysis showed that peptide 5 folds to a helical conformation in the presence of a hydrophobic environment. Although the basis for the antiviral action of the peptides is not understood, our data suggest that the inhibitory peptides may act by interacting with cell-surface molecules involved in viral infection.

3T3 Cells↗
PubMed1996

Time and frequency domain analysis of electromyogram and sound myogram in the elderly.

The aim of this work was to evaluate the influence of the ageing process on the time and frequency domain properties of the surface electrical and mechanical activity of muscle. In 20 healthy elderly subjects (10 men and 10 women, age range 65-78 years) and in 20 young controls, during isometric contractions of the elbow flexors in the 20%-100% range of the maximal voluntary contraction (MVC), estimations were made of the root mean square (rms) and the mean frequency (MF) of the power density spectrum distribution, from the surface electromyogram (EMG) and sound myogram (SMG) signals, detected at the belly of the biceps brachii muscle. Compared to the young controls, the MVC was lower in the elderly subjects (P < 0.05); at the same %MVC the rms and the MF of EMG and SMG were lower (P < 0.05) in elderly subjects; the rms and MF of the two signals increased as a function of the effort level in all groups. Only in the 80%-100% MVC range did the EMG-MF level off and the SMG-rms decrease; in contrast the young controls, at 80% MVC the high frequency peak in the SMG power spectrum density distribution was not present in the elderly subjects. The results for MVC and %MVC can be related to the reduction in the numbers of muscle fibres in aged subjects. In particular, the lack of fast twitch fibre motor units (MU), attaining high firing rates, might also explain the result at 80% MVC. In 80%-100% MVC range the two signals rms and MF behaviour may have been related to the end of the recruitment of larger MU with high conduction velocity, and to the further increment of MU firing rate in the biceps brachii muscle beyond 80% MVC, respectively. Thus, the coupled analysis of the EMG and SMG with force suggests that in the elderly subjects the reduction of the number of muscle fibres may have co-existed with a MU activation pattern similar to that of the young subjects.

Adult↗
PubMed1996

Submitral left ventricular aneurysm. Report of 2 surgical cases.

Submitral left ventricular aneurysm most commonly occurs among the black population. Nevertheless, this lesion has been described among whites. We report 2 cases of submitral left ventricular aneurysm that we treated successfully by surgery. Case 1 is that of a 52-year-old Brazilian black man with a submitral left aneurysm and mitral incompetence. Case 2 is that of a 25-year-old white man with a history of recurrent stroke; his echocardiographic study showed a small submitral left ventricular aneurysm. Due to the growing incidence of submitral left ventricular aneurysm among the white population, we emphasize the importance of a targeted echocardiographic study in all patients with a history of embolic episodes in the absence of apparent risk factors for embolism.

Adult↗
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

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↗
PubMed1995

Localization of HLA-A2.1-restricted T cell epitopes in the circumsporozoite protein of Plasmodium falciparum.

Localization of human MHC class I-restricted T cell epitopes in the circumsporozoite (CS) protein of the human parasite Plasmodium falciparum is an important objective in the development of antimalarial vaccines. To this purpose, we synthesized a series of overlapping synthetic 20-mer peptides, spanning the entire sequence of the 7G8 CS molecule except for the central repeat B cell domain. The P.f.CS peptides were first tested for their ability to bind to the human MHC class I HLA-A2.1 molecule on T2, a human cell line. Subsequently, the use of a series of shorter peptide analogues allowed us to determine the optimal A2.1 binding sequence present in several of the 20-mers. Binding P.f.CS peptides were further tested for their capacity to activate PBL from HLA-A2.1+ immune donors living in a malaria-endemic area. Specific IFN-gamma production was detected in the supernatant of cultures of PBL from exposed individuals. Cytotoxic T cell lines and clones were derived from the PBL of one responder, and their activity was shown to be HLA-A2.1-restricted and specific for the peptide 334-342 of the CS protein. In addition, double transgenic HLA-A2.1 x human beta 2-microglobulin mice were immunized with peptide 1-10 of the CS protein. T cells derived from immune lymph nodes displayed a peptide-specific HLA-A2.1-restricted cytolytic activity after one in vitro stimulation.

Amino Acid Sequence↗
PubMed1995

DNA binding activity of the glucocorticoid receptor is sensitive to redox changes in intact cells.

The effect of changes of redox conditions on glucocorticoid receptor (GR) activity in intact cells has been studied using two approaches. One was to evaluate the GR-DNA binding in extracts of COS2 cells transiently overexpressing GR and in which reactive oxygen intermediates (ROI) accumulate as a consequence of glutathione (GSH) depletion. GR-DNA binding was significantly decreased in COS2 cells treated with diethylmaleate (DEM), which causes GSH depletion by forming GSH-DEM complexes. A similar effect was observed for Sp1, another Zn-finger transcription factor, whereas no difference was observed for the C/EBP transcription factor, which is known to be unaffected by redox changes in vitro. N-Acetylcysteine (NAC), which counteracts the effects of DEM by increasing GSH biosynthesis, prevents the decrease of GR-DNA binding in cells treated with DEM. The GR-DNA binding efficiency was similarly decreased using extracts from H2O2-treated COS2 cells and from COS2 cells treated with buthionine sulphoximine, which causes GSH depletion via a mechanism different from that of DEM. The other approach was to evaluate the efficiency of a GR-regulated promoter under different redox conditions. In HeLa cells, transfected with a plasmid containing the CAT gene under the control of the glucocorticoid responsive element (GRE) within the mouse mammary tumor virus promoter, and treated with dexamethasone to activate GR, exposure to DEM significantly impaired the activation of CAT gene expression induced by dexamethasone. Also in this case NAC treatment inhibited the effects of DEM.

Base Sequence↗
PubMed1995

Synthesis and immunological characterization of 104-mer and 102-mer peptides corresponding to the N- and C-terminal regions of the Plasmodium falciparum CS protein.

We investigated the immunogenicity and the conformational properties of the non-repetitive sequences of the Plasmodium falciparum circumsporozoite (CS) protein. Two polypeptides of 104 and 102 amino acids long, covering, respectively, the N- and C-terminal regions of the CS protein, were synthesized using solid phase Fmoc chemistry. The crude polypeptides were purified by a combination of size exclusion chromatography and RP-HPLC. Sera of mice immunized with the free polypeptides emulsified in incomplete Freund's adjuvant strongly reacted with the synthetic polypeptides as well as with native CS protein as judged by ELISA and IFAT assays. Most importantly, these antisera inhibited the sporozoite invasion of hepatoma cells. In addition, sera derived from donors living in a malaria endemic area recognized the CS 104- and 102-mers. Conformational studies of the CS polypeptides were also performed by circular dichroism spectroscopy showing the presence of a weakly ordered structure that can be increased by addition of trifluoroethanol. The obtained results indicate that the synthetic CS polypeptides and the natural CS protein share some common antigenic determinants and probably have similar conformation. The approach used in this study might be useful for the development of a synthetic malaria vaccine.

Amino Acid Sequence↗