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G Geraci

Publications and source records attributed to G Geraci.

At least 37 records · Page 2Linked to original sources
PubMed1995

Cloning and characterization of a developmentally regulated sea urchin cDNA encoding glutamine synthetase.

A 2935-bp cDNA clone encoding glutamine synthetase (GS) was isolated from a cDNA library prepared from four-blastomere Paracentrotus lividus sea urchin embryos. The sequence consists of a 75-bp 5' untranslated region (5'-UTR) followed by a 1095-bp coding region corresponding to a 365-amino-acid (aa) protein, a 1747-bp 3'-UTR and a terminal 18-bp poly(A) tail. The encoded protein shows about 66% identical residues, as compared with human and lobster class-II GS. The sequence contains the Mn(2+)-binding aa and the highly conserved aa regions observed in other GS. Northern blot analyses show that the GS mRNA is present in the sea urchin egg and is developmentally regulated in the embryo.

Amino Acid Sequence↗
PubMed1994

Isolation of a new H3.3 histone variant cDNA of P. lividus sea urchin: sequence and embryonic expression.

A cDNA encoding a new H3 histone variant has been isolated from a Paracentrotus lividus sea urchin embryo cDNA library. The encoded protein is identical to the H3.3 histone subtype identified in other species, with the difference that E replaces D at position 81. The clone corresponds to a transcript of about 1.6 kb, not dependent on DNA replication, present in the unfertilized egg and at all stages of embryonic development. The coding part of the cDNA cross-reacts also with a 0.5 kb H3 late histone mRNA.

Animals↗
PubMed1994

1,10-Phenanthroline and Xenopus laevis teratology.

Frog oocytes and embryos have long served as traditional subjects of embryological research providing structural and functional information for the interpretation of the biological processes underlying development. A large number of various chemical agents induce typical teratological changes in frog embryos. However, the effects of metal deficiency of the first transition and IIB series or of chelating agents specific for these metals have never been examined in the frog. Multidentate chelating agents, including 1,10-phenanthroline (OP), which coordinate metals through N, O or S donor atoms are teratogenic also but in a manner characteristic for this class of reagents and completely different from those referred to above. Exposure to 10(-5) M OP causes maximal malformations with minimal mortality inducing craniofacial and skeletal abnormalities with failure of eye, head and other organ formation in 74% of frog embryos. In contrast, the non chelating analogue 1,7-phenanthroline (MP) has no effect at this concentration. A concentration of 10(-3) M OP is lethal. The known characteristics of either zinc and/or iron complexes with OP as well as the concentrations of these elements in frog oocytes and embryos are consistent with the hypothesis that the teratological observations are due to an effect of OP on either zinc or iron proteins.

Abnormalities, Drug-Induced↗
PubMed1993

Anion-mediated lysine-arginine interaction. Evidence in Chaetopterus variopedatus sperm protamine.

Chaetopterus ariopedatus sperm protamine is a stable oligomer. Specific amino acid side chain modifications show that the oligomeric structure depends on anion-mediated lysine-arginine interactions. The occurrence of this type of interaction is confirmed by the finding that poly-L-arginine readily forms aggregates with poly-L-lysine or with the native but not with the protamine with carbamylated epsilon-amino groups.

Amino Acids↗
PubMed1993

Amino-acid sequence of the cooperative dimeric myoglobin from the radular muscles of the marine gastropod Nassa mutabilis.

The complete amino-acid sequence of the dimeric and cooperative myoglobin from the radular muscles of Nassa mutabilis, a common edible gastropod mollusc on the Italian coast, has been determined. The molecule is a homodimer. The monomer is composed of 147 amino-acid residues, with a molecular mass of 15,760 Da. Its sequence is homologous with those of the dimeric myoglobins of the gastropod molluscs of the Prosobranchia subclass Busycon canaliculatum (63% conserved residues) and Cerithidea rhizophorarum (46% conserved residues). The rate of autoxidation to met-myoglobin of N. mutabilis oxymyoglobin at 25 degrees C is strongly pH-dependent with relative minimal rate values in the pH range 7 to 8.

Amino Acid Sequence↗
PubMed1993

Inhibition of erythroid differentiation in MEL cells by UV irradiation. Cell cycle and DNA repair activity.

Irradiation with a 3-s pulse of 254 nm UV light has been used to study sensitivity to mutagenic agents of mouse erythroleukemia (MEL) cell cultures in correlation with the cell cycle. A dose of UV irradiation was chosen that had no consequences for cell viability and growth. For this reason phenotypic effects were monitored on the progeny of all cells of the irradiated cultures by scoring those unable to undergo erythroid differentiation upon induction with dimethyl sulfoxide. The very short period of irradiation made it possible to show that MEL cells, synchronized by two sequential blocks of deoxythymidine and one of hydroxyurea (HU), are sensitive to UV irradiation only in a very short period of time at about 60 min after release from HU block. Determinations of deoxythymidine incorporation into DNA show that this time period corresponds only marginally to the initial part of the S phase during which irradiation has no consequences for cell properties. Cells are not sensitive to UV irradiation in G1 and in G2/M unless, immediately after irradiation and for the following 2 h, cultures are treated with 1 mM HU to interfere with DNA repair. Alkaline sucrose gradient analyses show at all tested times that irradiation leads to fragmentation of cell DNA. The data suggest that an immediate increase of deoxythymidine incorporation into DNA following irradiation is not necessary for the efficient repair of damaged DNA. In fact, the percent of cells expressing the erythroid phenotype is normal in the progeny of cells irradiated in G2/M, when TdR incorporation is at a minimum. Repair activities appear then to be mechanistically divided into two phases, (1) recognition labeling of the altered sites and (2) reconstitution of the DNA sequences. The first activity appears to be operative at all phases of the cycle, the second activity is little or not operative in G2/M, possibly delayed to the following G1 period.

Animals↗
PubMed1993

[Treatment of diastolic dysfunction of the left ventricle].

Numerous studies have already recognized the importance of diastole in the pathogenesis of congestive heart failure. Non-invasive evaluations are based particularly on echo-Doppler, on radionuclide angiography and on cine-nuclear magnetic resonance: they have enabled an accurate evaluation of diastolic function and dysfunction, although invasive hemodynamic study maintains a gold standard position. All these methods of study have consented the identification of 3 basic components (anatomic and functional): active relaxation, passive elastic relaxation, atrial function. The Authors have identified the causes of diastolic failure with a particular attention to the various components of diastole. They have analyzed the implication of therapy on the basis of a clear understanding of the etiology, pathogenesis and pathophysiology of the underlying cardiac disease.

Diastole↗
PubMed1993

[Perinatal and maternal pathology in 38 pregnant women with endemic goiter].

In a group of 38 pregnant women with primary, uni- or multinodular non-toxic endemic goitre, who were clinically euthyroid, 7.8% (3 cases) had previously undergone strumectomy for benign pathologies of the goitre and 10.5% (4 cases) received L-thyroxine therapy during pregnancy at a dose of 50 or 100 micrograms/day; during the course of pregnancy goitre was asymptomatic in 37 women (97.4%) and an endocystic hemorrhage occurred in 1 (2.6%) case. The goitre increased in volume in 42.1% (16 cases) of pregnant women monitored to term. Out of 20 patients undergoing ELISA of hormonal levels, 6 (30%) revealed TSH concentration more than twice the maximum normal value with normal concentrations of other thyroid hormones. There was a significant inverse correlation (r = 0.525) between T4 and TSH. Birth at term occurred at 39.9 +/- 2.6 weeks and was spontaneous in 78.9% of cases (30 cases) and laparotomic in 21.1% (8 cases). Perinatal pathologies included: 1 case (2.6%) of endo-uterine fetal death, 1 case of oligoamnios and 1 of IUGR. Funicular pathologies were observed in 13.1% of patients (5 cases). The Apgar index was > 8 in the 37 live births. The mean weight of male and female neonates and neonates from nulliparas and pluriparas was within the norm. When the data examined were compared to the results of the control group it was seen that there were no statistically significant differences.

Adult↗
PubMed1992

Alteration of the proximal bond energy in the unliganded form of the homodimeric myoglobin from Nassa mutabilis. Kinetic and spectroscopic evidence.

CO binding kinetics to the homodimeric myoglobin (Mb) from Nassa mutabilis has been investigated between pH 1.9 and 7.0. Protonation of the proximal imidazole at low pH (less than or equal to 3.0) and the consequent cleavage of the HisF8NE2-Fe proximal bond brings about a approximately 20-fold increase of the second-order rate constant for CO binding. This process displays a pKa = 4.0 +/- 0.2, significantly higher than that observed in all other deoxygenated hemoproteins investigated up to now. Such a feature underlies a decreased energy for the HisF8NE2-Fe proximal bond in the unliganded form and it also appears supported by resonance Raman spectroscopy in the low frequency region of the Fe(II) deoxygenated hemoprotein. Further, the pH-rate profile of N. mutabilis Mb, like that of the homodimeric hemoglobin (Hb) from Scapharca inaequivalvis (Coletta, M., Boffi, A., Ascenzi, P., Brunori, M. and Chiancone, E. (1990) J. Biol. Chem. 265, 4828-4830), can be described only by assuming a concerted proton-linked transition with n = 1.8 +/- 0.1. Such a characteristic suggests, also on the basis of the amino acid sequence homology between N. mutabilis Mb and S. inaequivalvis Hb in the region forming the subunit interface, that the interaction mechanism is similar for the two homodimeric proteins, and drastically different Hb in the region forming the subunit interface, that the interaction mechanism is similar for the two homodimeric proteins, and drastically different from that operative in other hemoproteins.

Animals↗
PubMed1992

Selective gene mutation in MEL cells.

MEL cells, undergoing erythroid differentiation and parasynchronized by dimethyl sulfoxide (DMSO) induction, were irradiated with a 3-s pulse of UV light at sublethal dose. A large number of clones deficient in different gene functions are found in the progeny of the treated cells, if the pulse irradiation is performed 18-24 h from the start of DMSO induction. Kinetics of thymidine incorporation into DNA show that the period of sensitivity corresponds to the S phase. The results show that the activities of the tested genes are differently affected depending on the exact time of cell irradiation. Maximum percent inhibition of cells not expressing glucose-6-phosphate dehydrogenase (G-6-PD) (70%) is produced by irradiating at 20 h from the start of DMSO induction; 6-phosphogluconate dehydrogenase (6-PGD) (55%), and hypoxanthine (guanine) phosphoribosyltransferase (HPRT) (33%), at 21 h; hemoglobin (50%), at 22 h. The time difference in the sensitivity to UV light is highly reproducible and has been exploited to isolate, with high efficiency, cellular clones deficient in any one of the tested functions. Determinations of enzymatic activities on cell lysates show that the expression of tested genes is actually altered in cells that, on the basis of cytochemical tests, appear unaffected by UV irradiation. While the production of mutant clones is observed only during the S phase of the cell cycle, immediate statistical damage of the cellular DNA is produced at all times of irradiation. This finding excludes that the two types of phenotypic alterations, blocked or altered gene expression, both propagated in the progeny of the cells as clonal properties, may derive from a preferential alteration of those functions during the S phase.

Cell Differentiation↗
PubMed1991

Observation of a stable intermediate form in the reaction of human hemoglobin with carbon monoxide.

The reaction of human hemoglobin with carbon monoxide has been investigated near the equilibrium isosbestic wavelength (i.e. 426 nm). As previously reported by others [Gray, R.D. & Gibson, Q. H. (1971) J. Biol. Chem. 246, 5176-5178], in the presence of 0.1 M phosphate pH 7.0 a rise-and-fall kinetic pattern can be observed at this wavelength, which indicates the presence of at least one spectroscopically detectable intermediate species. In this paper we demonstrate that (a) the intermediate species is thermodynamically stable; (b) both phases refer to bimolecular processes; (c) only the initial fast phase is observed when deoxyhemoglobin is reacted with substoichiometric amounts of CO (i.e. final [CO]/[heme] less than or equal to 0.5); (d) only the second slow phase is observed when hemoglobin that is partially saturated with CO (Y less than or equal to 0.5) is reacted with saturating CO concentrations; (e) the CO dissociation rate constant measured on the intermediate formed after a partial CO saturation at a final Y approximately 0.4 has a value similar to that observed starting from the fully liganded form. These results can be accounted for by a two-state allosteric model [Monod, J., Wyman, J. & Changeux, J.-P. (1965) J. Mol. Biol. 12, 88-118] under the assumption that either (a) 426 nm is an isosbestic wavelength for the T0-R spectral changes but not for the T0-T liganded reaction; or (b) a functional heterogeneity of the two types of subunits is present in the T state and at this wavelength this feature is spectroscopically detectable.

Carbon Dioxide↗
PubMed1990

Inhibition of MEL cells' capacity to undergo erythroid differentiation by chemicals added during induction.

Erythroid differentiation of murine erythroleukemia (MEL) cells, as induced by dimethyl sulfoxide, can be suppressed by chemicals at very low concentrations, not affecting cell viability and proliferation, if present in the culture medium between 18 and 24 h after addition of the inducer. The effect is apparent on the progeny of the treated cells and is determined, between day 3 and 5 following DMSO induction, as percent value of cells expressing the erythroid phenotype. Cultures showing decreased values are no longer terminal and a large number of clones, incapable of expressing the erythroid phenotype, can be isolated from them. In contrast, induced cultures are terminal if the added chemicals do not decrease the expression of the erythroid phenotype. Incorporation of thymidine into induced cultures reveals that maximal sensitivity of MEL cells to chemicals coincides with DNA duplication. In all affected cells, the inhibition to undergo erythroid differentiation is transmitted from one cell generation to the next.

Cell Differentiation↗
PubMed1989

Histone-lysine methyltransferase activity from sea-urchin embryo nuclei. Changes in substrate specificity upon purification.

The S-adenosylmethionine:histone-lysine methyltransferase (EC 2.1.1.43) enzyme activity, present in the chromatin of sea-urchin embryo nuclei, has been purified about 300-fold with 30% overall yield. The initial activity in the nucleus transfers methyl groups to the epsilon-amino group of lysines and acceptor proteins are chromatin-bound H3 and H4 histones. In contrast, the purified enzyme activity transfers methyl groups to the arginines and acceptor proteins are soluble H3 and H4 histones. The two changes in substrate specificity do not occur at the same time. The variation of acceptor protein from chromatin-bound to soluble histones occurs at the first step, upon nuclei sonication, when no protein fractionation has yet been performed. At that step, lysine is still the only methylated side-chain. The variation of the methylated amino acid from lysine to arginine occurs gradually with increasing enzyme purification. The enzyme activity has a molecular mass of about 200 kDa. Saturation curves for H3 and H4 histones, used as substrate either individually or in total histones, and for AdoMet show no substantial dependence on enzyme purification. Maximal activity for the enzyme, at all purification levels, occurs at about pH 8 for all substrate histones. An increase in the relative concentrations of di- and trimethyllysine derivatives is observed with the more purified enzyme preparations, while the ratio of mono- and dimethylarginine derivatives remains constant. The data are taken as evidence that the same protein molecule is responsible for the two activities.

Animals↗
PubMed1987

Evidences that hemoglobin switch in the chick embryo depends on erythroid cell line substitution.

Chemical identifications of various hemoglobin types were performed on unfractionated erythroid cells derived from chicken embryos at 5 and 7 days of development and on purified primitive and definitive cells. Proteins were pulse-labelled in primitive erythroid cells at various times of culture to identify those actually synthesized. The data show that primitive cells contain and synthesize only embryonic hemoglobins at all stages of maturation and definitive cells contain adult and minor embryonic hemoglobins, but no major embryonic hemoglobins, not even in trace amounts. These results support a model for hemoglobin switch in the chicken embryo based on cell line substitution.

Animals↗
PubMed1986

Structuring of H1 histone. Evidence of high-affinity binding sites for phosphate ions.

Circular dichroism studies show that low concentrations of phosphate ions induce folding of the H1 histones. Sulfate and perchlorate anions have effects similar to phosphate indicating the presence on H1 histones of binding sites with high affinity for ions with tetrahedral geometry. In fact, the structuring efficiency of different ions, as determined by the midpoint value of the effect/concentration curve, is 0.05 M for NaCl, 0.005 M for NaClO4, 0.001 M for sodium phosphate and 0.0003 M for sodium sulfate on H1 histone from Chaetopterus variopedatus sperm chromatin. Phosphate shows similar folding efficiency also on calf thymus and on sea-urchin sperm H1 histones. The effect of phosphate ions on the H1 molecule is observed also by differential absorption spectroscopy in the region of absorption of amino acid side-chains. Binding studies by gel filtration chromatography on Sephadex columns show that phosphate binding occurs in the presence of structuring concentrations of sodium chloride. About 9 ATP molecules bind to H1 histones derived from non-active cell chromatins while only 3.5 ATP molecules bind to H1 derived from active somatic chromatins. The fluorescence of the tyrosine residues of Chaetopterus sperm H1 is enhanced by chloride ions and heavily quenched by phosphate ions in correlation with structuring of the molecule, demonstrating direct interactions between tyrosine residues and phosphate ions. The defined and limited number of phosphate groups bound per histone molecule, the high affinity of the interaction and the effect on the structure of the histone suggest the participation of phosphate groups in the binding of H1 histones to DNA.

Animals↗
PubMed1986

Inhibition of dimethyl sulfoxide induced erythropoietic differentiation of murine erythroleukemia cells in culture.

The dimethyl sulfoxide induced erythropoietic differentiation of murine erythroleukemia cells, as determined by scoring benzidine positive cells, is inhibited by mitomycin C at concentrations that have no effect on cell proliferation. The inhibition occurs only when cells are treated with mitomycin C during induction and has a limit value of about 50%, independent of mitomycin C concentration. This limit value does not depend on cell heterogeneity since genetically homogeneous subclones, derived from DS19 clone, show levels of mitomycin C inhibition between 16 and 50%. Treatment with mitomycin C at different times after dimethyl sulfoxide addition shows that cell sensitivity to inhibition is not homogeneous during the induction period; it is maximal between 18 and 24 h from the start of induction and is observed with a concentration of mitomycin C as low as 25 fM. The inhibition of the benzidine positive phenotypic expression appears irreversible since this effect is observed on cells even several generations after those which were actually treated.

Animals↗
PubMed1985

Molecular basis of superreactivity of cysteine residues 31 and 32 of seminal ribonuclease.

The molecular basis of the high reactivity toward reducing agents of intersubunit disulfides at positions 31 and 32 of dimeric bovine seminal ribonuclease was investigated by studying in the monomeric enzyme the fast reaction kinetics with disulfides of the adjacent cysteine-31 and -32, exposed by selective reduction of the intersubunit disulfides. Negatively charged and neutral disulfide reagents were used for measuring the thiol reaction rates at neutral pH. The kinetics studied as a function of pH permitted us to define pK values for the thiols of interest and indicated the possibility of determining pK values of SH groups in proteins indirectly by measuring the kinetics of reactivity of the SH groups with a disulfide reagent. The results were compared with those obtained under identical conditions with synthetic thiol peptides and model compounds. The data indicate that the superreactivity of intersubunit disulfides of seminal ribonuclease is matched by the high reactivity at neutral pH of adjacent cysteine residues 31 and 32, as compared to all small thiol compounds tested. The synthetic hexapeptide segment of seminal ribonuclease Ac-Met-Cys-Cys-Arg-Lys-Met-OH, which includes the two cysteine residues of interest, was even more reactive. These data, and the other results reported in this paper, led to the conclusion that the superreactivity at neutral pH of cysteine residues at positions 31 and 32 of bovine seminal ribonuclease is primarily dependent on the nearby presence of positively charged groups, particularly the epsilon-NH2 of lysine-34, and is influenced by the adjacency of the two thiols and by the protein tertiary structure.

Amino Acids↗