Biomedical subjects

S Cavallo

Publications and source records attributed to S Cavallo.

12 recordsLinked to original sources

PubMed2000

The unusual dodecameric ferritin from Listeria innocua dissociates below pH 2.0.

The stability of the dodecameric Listeria innocua ferritin at low pH values has been investigated by spectroscopic methods and size-exclusion chromatography. The dodecamer is extremely stable in comparison to the classic ferritin tetracosamer and preserves its quaternary assembly at pH 2.0, despite an altered tertiary structure. Below pH 2.0, dissociation into dimers occurs and is paralleled by the complete loss of tertiary structure and a significant decrease in secondary structure elements. Dissociation of dimers into monomers occurs only at pH 1.0. Addition of NaCl to the protein at pH 2.0 induces structural changes similar to those observed upon increasing the proton concentration, although dissociation proceeds only to the dimer stage. Addition of sulfate at pH values >/= 1.5 prevents the dissociation of the dodecamer. The role played by hydrophilic and hydrophobic interactions in determining the resistance to dissociation of L. innocua ferritin at low pH is discussed in the light of its three-dimensional structure.

Anions↗

PubMed1999

Incorporation of iron by the unusual dodecameric ferritin from Listeria innocua.

The polypeptide chain that assembles into the unusual dodecameric shell of Listeria innocua apoferritin lacks the ferroxidase centre characteristic of H-type mammalian chains, but is able to catalyse both Fe(II) oxidation and nucleation of the iron core. A cluster of five carboxylate residues, which correspond in part to the site of iron core nucleation typical of L-type mammalian ferritins, has been proposed to be involved in both functions. The features of the iron uptake kinetics and of Fe(II) autoxidation in the presence of citrate followed spectrophotometrically confirm this assignment. In Listeria the kinetics of iron uptake is hyperbolic at low Fe(II)-to-dodecamer ratios and becomes sigmoidal when iron exceeds 150 Fe(II) atoms per dodecamer, namely when a fast crystal growth phase follows a slow initial nucleation step. Iron autoxidation in the presence of citrate displays a similar behaviour. Thus the time course is sigmoidal at low citrate-to-Fe ratios at which Fe(III) polymerization is predominant, but is hyperbolic at ligand concentrations high enough to prevent polymerization. The marked inhibitory effect of Tb(III) on the kinetics of iron incorporation confirms that carboxylates provide the iron ligands in L. innocua apoferritin. Iron uptake followed in steady-state fluorescence experiments allows one to distinguish Fe(II) binding and oxidation from the subsequent movement of Fe(III) into the apoferritin cavity as in mammalian ferritins despite the different localization of the tryptophan residues.

Apoferritins↗

PubMed1998

Formation and movement of Fe(III) in horse spleen, H- and L-recombinant ferritins. A fluorescence study.

Iron oxidation and incorporation into apoferritins of different subunit composition, namely the recombinant H and L homopolymers and the natural horse spleen heteropolymer (10-15% H), have been followed by steady-state and time-resolved fluorescence. After aerobic addition of 100 Fe(II) atoms/polymer, markedly different kinetic profiles are observed. In the rL-homopolymer a slow monotonic fluorescence quenching is observed which reflects binding, slow oxidation at the threefold apoferritin channels, and diffusion into the protein cavity. In the rH-homopolymer a fast fluorescence quenching is followed by a partial, slow recovery. The two processes have been attributed to Fe(II) binding and oxidation at the ferroxidase centers and to Fe(III) released into the cavity, respectively. The fluorescence kinetics of horse spleen apoferritin is dominated by the H chain contribution and resembles that of the H homopolymer. It brings out clearly that the rate of the overall process is limited by the rate at which Fe(III) leaves the ferroxidase centers of the H chains where binding of incoming Fe(II) and its oxidation take place. The data obtained upon stepwise addition of iron and the results of optical absorption measurements confirm this picture. The correspondence between steady-state and time-resolved data is remarkably good; this is manifest when the latter are used to calculate the change in fluorescence intensity as apparent in the steady-state measurements.

Animals↗

PubMed1998

Association between cyclin D1 (CCND1) gene amplification and human papillomavirus infection in human laryngeal squamous cell carcinoma.

Head and neck squamous cell carcinomas (SCCs) seem to follow a multistep process of carcinogenesis in which chemical and/or viral agents are associated with specific genetic alterations. The prevalence of human papillomavirus (HPV) infection and the amplification of the cyclin D1 (CCND1) gene were evaluated in a series of 75 laryngeal SCCs by PCR with HPV consensus primers and Southern blot analysis with a CCND1-specific probe, respectively. HPV DNA was detected in 22 of 75 (29.3%) tumors, and it belonged almost exclusively to the highly oncogenic HPV-16, HPV-18, and HPV-33. CCND1 gene amplification was found in 15 of 75 (20%) tumors, and it was associated with HPV infection in a statistically significant manner (chi2 = 20.3; P < 0.001). Because the viral oncoproteins E6 and E7 from high-risk HPV types are known to promote genomic rearrangements, these findings suggest that amplification of the CCND1 gene in laryngeal SCCs may occur as a consequence of the genomic instability associated with HPV infection. In turn, amplified CCND1, either alone or in conjunction with a direct action of the viral oncoproteins E6 and E7, could lead to a perturbation of the cell cycle. This model could explain the involvement of high-risk HPV types in laryngeal carcinogenesis.

Adult↗

PubMed1996

Thermal stability of horse spleen apoferritin and human recombinant H apoferritin.

The thermal stability of horse spleen apoferritin, a heteropolymer composed of 90% L and 10% H chains, has been studied by differential scanning calorimetry and compared with that of the human recombinant H homopolymer. The denaturation temperatures (Tm) are significantly higher for the horse spleen polymer than for the recombinant protein under all experimental conditions (e.g., at pH 7, Tm values are > or = 93 and 77 degrees C, respectively). The thermal denaturation process displays substantial reversibility for both polymers up to a few degrees below Tm, as indicated by CD measurements in the far and near uv regions. At temperatures higher than Tm the thermograms are influenced by the exothermic contribution of aggregation and/or precipitation. The H homopolymer thermogram, which is not distorted by the exotherm, is consistent with a multistate denaturation process. Acid dissociation of apoferritin produces stable dimeric subunits. The thermal unfolding of both dimeric subunits is reversible at least up to Tm and is characterized by an inversion of stability relative to the polymers (at pH 3.5, Tm is 42 degrees C for the horse spleen and 50 degrees C for the H subunit). These results indicate that the stabilization of the polymeric structure arises mainly from interactions between dimers, in accordance with the crystallographic evidence that the dimers are the building blocks of the polymeric molecule.

Animals↗

PubMed1996

Cyclin D1 gene amplification in human laryngeal squamous cell carcinomas: prognostic significance and clinical implications.

The cyclin D1 (CCND1) gene is amplified, rearranged, and overexpressed frequently in human cancer, including squamous cell carcinoma. The gene dosage of CCND1 was examined in 51 primary laryngeal squamous cell carcinomas, and amplification of the gene was found in 9 (17.6%) cases. CCND1 amplification did not correlate with age, tumor localization and extension, cervical lymph node involvement, histopathological grading, and epidermal growth factor receptor levels. In a univariate analysis, CCND1 amplification, tumor extension, lymph node involvement, poor histological differentiation, and high epidermal growth factor receptor levels were correlated significantly with shorter overall survival. In a median follow-up period of 29 months, the overall survival rate was 71.4% for patients affected with tumors displaying a normal CCND1 dosage and only 25.0% for patients affected with tumors carrying amplified CCND1 (P = 0.0288). In a multivariate analysis, only CCND1 and tumor extension retained statistically significant prognostic values (P = 0.037 and 0.041, respectively). This is the first report in which CCND1 amplification is identified as a significant independent prognostic factor in laryngeal carcinoma. Evaluation of CCND1 amplification could be applicable to the clinical management of laryngeal cancer, allowing identification of patients with poor prognoses.

Adult↗

PubMed1996

Telomerase activity in human laryngeal squamous cell carcinomas.

The activation of telomerase has been shown to be an important step during tumorigenesis in a variety of malignancies and is associated with characteristics of cellular immortality, such as indefinite proliferative potential. We studied telomerase activity in a series of human laryngeal carcinomas. Thirty-six tumors from 35 patients were studied using a sensitive PCR-based technique, the telomeric repeat amplification protocol assay. Telomerase activity was present in 32 tumors (89%), and the level of activity correlated with the stage of disease. In two of four telomerase-negative tumors, we found evidence of an inhibitor of telomerase activity. In many cases, samples of mucosa surrounding the tumor were also studied, and telomerase could be detected in 16 of 21 patients. For this reason, we proceeded to perform a topographical analysis that demonstrated a pattern of telomerase activity suggestive of a spread of telomerase-positive cells. In conclusion, these data indicate that telomerase activation is important for laryngeal carcinogenesis and that telomerase assay might be a valuable addition to determine the spread of the disease.

Carcinoma, Squamous Cell↗

PubMed1991

The interaction of hydroxypyridinones with human serum transferrin and ovotransferrin.

The interaction of hydroxypyridinones with human serum transferrin and ovotransferrin has been studied by analyzing the distribution of iron between the chelator and the proteins as a function of both ligand concentration and transferrin saturation. The kinetics of iron removal by 3-hydroxypyridin-4-ones from both transferrins is slow; in ovotransferrin it appears to be monophasic, in contrast to that observed for serum transferrin. After 24 hours incubation at a 40:1 chelator:protein molar ratio, the percentage of iron removed from Fe(III)-ovotransferrin is 50%-60%, and is somewhat higher in the case of serum transferrin, in line with the respective affinity constants for the metal. The 3-hydroxypyridin-2-ones and the 3-hydroxypyran-4-ones, both of which have lower affinities for Fe(III), remove smaller proportions of the metal. The percentage of desaturation obtained with bidentate and hexadentate pyridinones appears to be similar for both transferrin classes at chelator:protein molar ratios from 40:1. The degree of transferrin saturation influences the extent of chelator mediated iron mobilization in the case of serum transferrin, but not of ovotransferrin. 59Fe competition studies demonstrate that bidentate pyridin-4-ones are capable of donating iron to serum apotransferrin; the relative concentrations of ligand and protein influence the distribution of iron because their effective binding constants (at pH 7.4) for Fe(III) are similar.

Apoproteins↗

PubMed1989

Study of proton spin-lattice relaxation variation induced by paramagnetic antibodies.

A murine anti-human melanoma monoclonal antibody fragment was labeled with gadolinium and its proton relaxation efficiency compared to controls at frequencies ranging from 2 to 300 MHz. Relaxation time variations were about 30-40% in 10-15 microM solutions. The labeled fragment showed proton relaxation enhancement relative to free gadolinium, while preserving its immunoreactivity. A tentative labeling of a melanoma pellet by means of the fragment, just at the borderline of a minimum expected T1 variation, gave no detectable difference.

Animals↗

PubMed1986

[Not Available].

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Historiography↗

PubMed1983

[Not Available].

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Child↗

PubMedDate not supplied

Telomerase activity in human hematopoietic progenitor cells.

BACKGROUND AND OBJECTIVE: Telomerase is the enzyme that stabilizes and elongates the telomeric ends of chromosomes. It is expressed in germline and malignant cells and absent in most human somatic cells. The selective expression of telomerase has thus been proposed to be a basis for the immortality of germline and malignant cells. Recently, telomerase activity has been observed in human bone marrow (BM) and peripheral blood (PB) samples. The objective of our study was to further characterize the telomerase-expressing population in BM and PB. METHODS: CD34+ cells were isolated from BM and PB, cultured in vitro, and telomerase activity was assessed by the PCR-based TRAP assay. RESULTS: Telomerase activity in human BM and PB could be almost exclusively assigned to the hematopoietic progenitor cell fraction expressing the CD34 antigen. We observed telomerase activity in CD34+ cells from BM and cytokine-mobilized PB. CD34+ cells lacking co-expression of CD33 demonstrated higher levels of telomerase than myeloid committed CD34+/CD33+ cells. In vitro culture of CD34+ cells in the presence of a cocktail of growth factors inducing differentiation resulted in a decrease of telomerase activity. Telomerase activity increased in peripheral blood during cytokine-induced mobilization of hematopoietic progenitor cells. INTERPRETATION AND CONCLUSIONS: Our data demonstrate that at least a portion of the hematopoietic stem/progenitor cell fraction expresses telomerase and downregulates its expression through differentiation.

Antigens, CD34↗