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Biomedical subjects

G D'Urso

Publications and source records attributed to G D'Urso.

At least 19 recordsLinked to original sources
PubMed2001

Increased circulating levels of ouabain-like factor in patients with asymptomatic left ventricular dysfunction.

BACKGROUND: Much evidence has been accumulated that human plasma contains digitalis-like factor(s) with Na/K ATPase inhibitor properties. Increased concentrations of ouabain-like factor (OLF) have been reported in patients with moderate to severe hypertension and in patients with overt congestive heart failure due to dilated cardiomyopathy. AIM: The presence of circulating OLF has not been investigated in borderline to mild hypertension or in the early stage of dilated cardiomyopathy. METHODS AND RESULTS: The study population consisted of 18 normal volunteers, 24 patients with borderline to mild hypertension, 47 patients with asymptomatic left ventricular dysfunction (ALVD) due to dilated cardiomyopathy and 26 patients with cardiac arrhythmias but normal left ventricular function. OLF values (pM ouabain equivalent) were assayed in extracted plasma, using a radioimmunoassay for ouabain. OLF was, respectively, 29.4+/-20.6 pM in normal controls, 39.1+/-23.8 pM in hypertensives, 35+/-18 pM in patients with cardiac arrhythmias, 52.3+/-25.8 pM in ALVD patients not treated with digoxin and 64.6+/-29.6 pM in ALVD patients treated with digoxin. Patients with ALVD, both treated and not treated with digoxin, had OLF significantly higher (P<0.05) than all the other groups. In patients with ALVD no correlation between OLF and left ventricular ejection fraction was observed. In the hypertensive group no correlation between OLF and both diastolic and systolic pressure was found. CONCLUSION: Increased concentrations of OLF were observed in patients with left ventricular dysfunction due to dilated cardiomyopathy, before the occurrence of overt heart failure, suggesting that OLF may be an early marker of the disease.

Adult↗
PubMed2001

Schizosaccharomyces pombe cells lacking the amino-terminal catalytic domains of DNA polymerase epsilon are viable but require the DNA damage checkpoint control.

In Schizosaccharomyces pombe, the catalytic subunit of DNA polymerase epsilon (Pol epsilon) is encoded by cdc20(+) and is essential for chromosomal DNA replication. Here we demonstrate that the N-terminal half of Pol epsilon that includes the highly conserved polymerase and exonuclease domains is dispensable for cell viability, similar to observations made with regard to Saccharomyces cerevisiae. However, unlike budding yeast, we find that fission yeast cells lacking the N terminus of Pol epsilon (cdc20(DeltaN-term)) are hypersensitive to DNA-damaging agents and have a cell cycle delay. Moreover, the viability of cdc20(DeltaN-term) cells is dependent on expression of rad3(+), hus1(+), and chk1(+), three genes essential for the DNA damage checkpoint control. These data suggest that in the absence of the N terminus of Pol epsilon, cells accumulate DNA damage that must be repaired prior to mitosis. Our observation that S phase occurs more slowly for cdc20(DeltaN-term) cells suggests that DNA damage might result from defects in DNA synthesis. We hypothesize that the C-terminal half of Pol epsilon is required for assembly of the replicative complex at the onset of S phase. This unique and essential function of the C terminus is preserved in the absence of the N-terminal catalytic domains, suggesting that the C terminus can interact with and recruit other DNA polymerases to the site of initiation.

Catalytic Domain↗
PubMed2000

Effects of shearing and supplemental level on intake of dry ewes grazing on barley stubble.

Twenty-eight Comisana dry ewes were utilised to evaluate the effect of shearing (14 shorn and 14 unshorn ewes) and supplemental level (100 and 300g of concentrate) on intake of barley stubble. Shorn ewes showed a small increase in dry matter intake (at the end of August: 1.32 vs. 1.10kg/day; p<0.01). Intake of barley stubble decreased as supplement level increased (mean: 1.18 vs. 1.29; p<0.01). On average, substitution effect was 0.63. Total lamb weight per ewe was greater in the group receiving 300g of concentrate (7.38 vs. 5.85; p<0.05). Shearing induced a small, but not significant decrease in total lamb weight per ewe (6.18 vs. 7.05kg/ewe). Results seem to indicate that unshorn ewes react better to environmental stress and that 300g improve reproductive performance.

Journal Article↗
PubMed2000

Selective inhibition of human erythrocyte Na+/K+ ATPase by cardiac glycosides and by a mammalian digitalis like factor.

Na+/K+ATPase is a transport membrane protein which contains the functional receptor for digitalis compounds. In this work we compare the inhibition curves of Na+/K+ATPase measured by the inhibition of 86Rb uptake in human red blood cells by cardiac glycosides and by an endogenous digitalis like factor (EDLF) extracted from human newborn cord blood. The curves of Na+/K+TPase inhibition show a monophasic shape for ouabain, strophantidin, digitoxin, proscillaridin and EDLF whereas a biphasic shape for ouabagenin, digoxin, digoxigenin and digitoxigenin. All the drugs are potent inhibitors of erythrocyte Na+/K+ATPase with an IC50 ranging from 1.8 x 10(-9) M to 1.4 x 10(-11) M for the higher affinity binding site and from 1.8 x 10(-6) M to 5.5 x 10(-9) M for the lower affinity site. Digitoxigenin is the most active showing the higher active site at 1.4 x 10(-11) M. Ouabain and digoxin have higher affinity compared with their corresponding genins, while digitoxigenin shows a binding site with higher affinity than the respective cardiac glycosides. The increased affinity of the drugs to Na+/K+ATPase may be related to a lipophilic region in correspondence of the carbons 10, 9, 11, 12, 13 of the steroid nucleus, situated in the opposite side with respect of the C-OH-14. The comparison of the inhibition curves and the HPLC profile of newborn EDLF and of the investigated cardenolides suggest that EDLF may be a compound identical or very similar to ouabain.

Cardiac Glycosides↗
PubMed1998

Effect of sustained-release somatotropin on performance and grazing behavior of ewes housed at different stocking rates.

This study evaluated the effects of recombinant bovine somatotropin (bST; one injection of 320 mg per ewe) on milk production and composition and on the grazing behavior of multiparous ewes in the third to fourth lactation. Forty Comisana lactating ewes were divided into four groups: 1) untreated, grazing on natural pasture (botanical composition: 35% of Graminaceae, 49% of Fabaceae, 6% of Cruciferae, 10% of other families) at a low stocking rate (16 m2/d); 2) untreated, grazing at a high stocking rate (8 m2/d); 3) treated with bST, grazing at a low stocking rate; and 4) treated with bST, grazing at a high stocking rate. The diets of the ewes were supplemented with vetch and oat hay (500 g/d) and with concentrate (500 g/d). Treatment increased milk production (923.8 vs. 669.5 g/d) but had little effect on fat and protein contents. Administration of bST significantly increased herbage intake; the effect on intake was more marked at the high stocking rate. Under these grazing conditions, the treated ewes reduced selective intake behavior and, thus, achieved good feed intake despite the low biomass availability.

Animal Feed↗
PubMed1997

Schizosaccharomyces pombe cdc20+ encodes DNA polymerase epsilon and is required for chromosomal replication but not for the S phase checkpoint.

In fission yeast both DNA polymerase alpha (pol alpha) and delta (pol delta) are required for DNA chromosomal replication. Here we demonstrate that Schizosaccharomyces pombe cdc20+ encodes the catalytic subunit of DNA polymerase epsilon (pol epsilon) and that this enzyme is also required for DNA replication. Following a shift to the restrictive temperature, cdc20 temperature-sensitive mutant cells block at the onset of DNA replication, suggesting that cdc20+ is required early in S phase very near to the initiation step. In the budding yeast Saccharomyces cerevisiae, it has been reported that in addition to its proposed role in chromosomal replication, DNA pol epsilon (encoded by POL2) also functions directly as an S phase checkpoint sensor [Navas, T. A., Zhou, Z. & Elledge, S. J. (1995) Cell 80, 29-39]. We have investigated whether cdc20+ is required for the checkpoint control operating in fission yeast, and our data indicate that pol epsilon does not have a role as a checkpoint sensor coordinating S phase with mitosis. In contrast, germinating spores disrupted for the gene encoding pol alpha rapidly enter mitosis in the absence of DNA synthesis, suggesting that in the absence of pol alpha, normal coordination between S phase and mitosis is lost. We propose that the checkpoint signal operating in S phase depends on assembly of the replication initiation complex, and that this signal is generated prior to the elongation stage of DNA synthesis.

Amino Acid Sequence↗
PubMed1995

Checkpoints in the cell cycle of fission yeast.

When cell cycle progression in fission yeast is disrupted, checkpoint controls ensure that the normal sequence of cell cycle events is maintained. Activation of a checkpoint relies on monitoring signals that might involve assembly of macromolecular structures essential for specific cell cycle processes. The past year has seen further elucidation of two new checkpoints operating during the cell cycle of Schizosaccharomyces pombe. One involves the product of the rum1 gene and prevents cells from entering mitosis from the pre-Start G1 interval. The second checkpoint operates during the later stages of the cell cycle and is essential for coupling the events of mitosis and cell division.

Cell Cycle↗
PubMed1995

DNA polymerase alpha, a component of the replication initiation complex, is essential for the checkpoint coupling S phase to mitosis in fission yeast.

Genetic analysis in the yeast Schizosaccharomyces pombe has shown that three genes cdc18, cut5, and cdt1, are essential for DNA synthesis and also for the checkpoint control that couples completion of DNA replication to the onset of mitosis. To test whether assembly of the replication initiation complex is an important element in the checkpoint control pathway we have investigated if DNA polymerase alpha (pol1), a component of the initiation complex, is essential for the S-phase checkpoint control. We show that germinating S. pombe spores disrupted for the pol1 gene enter mitosis despite defects in DNA synthesis. This is shown by monitoring septation index, DNA content, and by direct immunofluorescence of mitotic spindles using antibodies to alpha-tubulin. In addition we have isolated six temperature sensitive mutants in the pol1 gene that cause cell cycle arrest when grown at the nonpermissive temperature. Our experiments support a model in which DNA polymerase alpha, in addition to being part of the initiation complex, is required for a checkpoint signal that is activated as cells traverse START, and is essential to prevent mitosis until S phase has been completed. In contrast, proteins responsible for the elongation of DNA may not be necessary for this checkpoint signal.

Binding Sites↗
PubMed1990

Cell cycle control of DNA replication by a homologue from human cells of the p34cdc2 protein kinase.

The regulation of DNA replication during the eukaryotic cell cycle was studied in a system where cell free replication of simian virus 40 (SV40) DNA was used as a model for chromosome replication. A factor, RF-S, was partially purified from human S phase cells based on its ability to activate DNA replication in extracts from G1 cells. RF-S contained a human homologue of the Schizosaccharomyces pombe p34cdc2 kinase, and this kinase was necessary for RF-S activity. The limiting step in activation of the p34 kinase at the G1 to S transition may be its association with a cyclin since addition of cyclin A to a G1 extract was sufficient to start DNA replication. These observations suggest that the role of p34cdc2 in controlling the start of DNA synthesis has been conserved in evolution.

Burkitt Lymphoma↗
PubMed1989

Cellular and viral control of the initiation of DNA replication.

Cell-free replication of SV40 DNA in extracts prepared from S phase cells is at least 20-fold more efficient than in extracts from G1 cells. The increased activity of S phase extracts correlates with the presence of an S phase-specific cellular factor that enhances DNA unwinding at the replication origin. This change in origin-DNA structure during the initiation of SV40 replication proceeds through at least three discrete steps which can be distinguished by their extent of topologic unwinding (linking differences of -1, -2 and -5). Specific DNA elements flanking the core origin enhance replication in vivo and facilitate the formation of the pre-initiation complexes, indicating that formation of these underwound conformations may be the limiting step in the initiation of DNA synthesis. In addition, the factor that activates DNA replication in extracts from S phase cells also enhances the formation of the most highly underwound -5 pre-initiation complex. These observations suggest that during SV40 replication, formation of the rate-limiting pre-initiation complex is the focus of at least three regulatory elements. Two of these are DNA sequences flanking the replication origin and the third is a cellular factor specific to the S phase cell.

Adenosine Triphosphate↗
PubMed1988

An origin unwinding activity regulates initiation of DNA replication during mammalian cell cycle.

An in vitro assay was developed to study the positive factors that regulate the onset of DNA replication during the mammalian cell cycle. Extracts prepared from cells at defined positions in the cell cycle were used to examine the replication of SV40 DNA in a cell free system. Extracts prepared from S phase cells were ten times more efficient at initiating replication at the SV40 origin than were extracts from G1 cells, whereas elongation rates were similar in G1 and S reactions. At a discrete point in the cell cycle, just before the cell's entry into S, an activity appeared that was required, in conjunction with SV40 T antigen, for site specific initiation at the SV40 origin. This factor had a role in unwinding DNA at the replication origin.

Antigens, Polyomavirus Transforming↗
PubMed1980

Polyamine levels in rat placenta during pregnancy.

Polyamine levels in rat placenta during pregnancy have been determined. Spermidine and spermine contents are high at the 15th day of gestation, then decrease gradually until to the term, remaining at levels comparable with those occurring in rapid growth tissues. The high levels of spermidine and spermine at 21th day of pregnancy may be related to RNA and protein turnover which is quite elevated at the end of gestation.

Animals↗