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Biomedical subjects

M Signorini

Publications and source records attributed to M Signorini.

At least 37 records · Page 2Linked to original sources
PubMed1993

Studies on tissue transglutaminases: interaction of erythrocyte type-2 transglutaminase with GTP.

Ca2+ and GTP are the main modulators of type-2 transglutaminases. To study the interaction of the enzyme with GTP, we have employed periodate-oxidized GTP as an affinity-label probe. Dialdehyde GTP bound irreversibly to type-2 transglutaminase in a time-dependent way with 1:1 stoichiometry at complete modification. The reaction took place in the absence, but was more rapid in the presence, of cyanoborohydride. Native GTP prevented incorporation of dialdehyde GTP, and Ca2+ significantly slowed down the reaction rate. The modified enzyme displayed decreased sensitivity to Ca2+, with a sigmoid saturation curve. We conclude that type-2 transglutaminase has a single GTP-binding site, the modification of which by dialdehyde GTP mimics nucleotide binding to the enzyme.

Affinity Labels↗
PubMed1993

Regulation of transglutaminase activity by GTP in digitonin permeabilized Yoshida tumor cells.

Yoshida tumor cells contain consistent amounts of type 2 transglutaminase, along with a membrane bound form of the enzyme. Digitonin permeabilized cells retain a large proportion of type 2 TGase and of substrate proteins which are labelled by radioactive putrescine in the presence of calcium. GTP inhibits protein labelling at low calcium concentration by inhibiting type 2 TGase without affecting membrane-bound TGase. These results support the notion that inhibition of type 2 TGase by GTP is physiologically relevant.

Animals↗
PubMed1992

Updated evaluation of the activity of antibiotics in a burn centre.

The results of microbiological tests performed in a burns unit between January 1989 and December 1990 have been analysed. Burn wound swabs and biopsies, blood cultures, central venous and urinary catheters, bronchial aspirates, pharyngeal swabs and faecal cultures for a total of 7950 examinations were considered. Staph. aureus was the most frequently isolated bacterium, followed by Staph. epidermidis, Pseud. aeruginosa and E. coli. The antibiograms have shown a low efficacy rate of cephalosporins, even of the latest generation, while with Gram-positive isolates the highest rates of activity were recorded by vancomycin and teicoplanin (100 per cent sensitivity). The situation seems better with Gram-negative organisms since they appear to be sensitive to a larger number of antimicrobial agents.

Adolescent↗
PubMed1992

Inactivation of placental factor XIIIa by acrylamide.

Acrylamide rapidly and irreversibly inactivates thrombin activated Factor XIIIa, without affecting neither the intact zymogen nor its proteolytic activation. The inactivation is strictly dependent on the presence of calcium ions and is accompanied by a decrease in the number of free and total thiol residues, suggesting that cysteine residue(s), whose reactivity is modulated by calcium, is (are) probably responsible for the acrylamide-directed inactivation.

Acrylamide↗
PubMed1991

Exploring the catalytic mechanism of skeletal muscle UDP-glucose pyrophosphorylase: identification of a hyperreactive cysteine at the enzyme active site.

1. The involvement of cysteine residues in the catalytic mechanism of UDP-glucose pyrophosphorylase was suggested by the rapid inactivation of the enzyme by N-ethylmaleimide, even at 1:1 reagent/enzyme stoichiometric ratios. 2. The inactivation is largely prevented by uridine substrates (UDP-glucose and UTP) in agreement with the assumption that the reactive cysteine is located at the active site.

Animals↗
PubMed1991

Pain threshold changes by skin vibratory stimulation in healthy subjects.

The purpose of this research is to evaluate the changes of cutaneous pain threshold induced by vibratory stimuli applied to the skin. The pain threshold was tested by means of electrical stimuli using the method of limits. Both vibratory stimuli (conditioning stimuli) and electrical stimuli (test stimuli) were driven by a computer. The experiments were carried out on the dorsal surface of the second phalanx of the index finger in the dominant hand of 34 healthy subjects (18 males and 16 females). The conditioning stimuli were sinusoidal waves (250 microm peak to peak) at a rate of 30 and 300 Hz. During the experiment (6 min of vibration and 9 min after) the cutaneous temperature of the stimulated area was recorded. Both vibratory rates induced significant increases of the pain threshold but the 30 Hz vibrations were the more effective. After stimulation the pain threshold lowered to a steady value which was higher than before the start of vibrations. Such threshold changes showed no correlation throughout the experiment with changes in skin temperature. We therefore advance the hypothesis that the main factors which modulate the pain threshold are neuronal connections between tactile and pain pathways.

Adult↗
PubMed1991

Photocleavage of muscle glycogen phosphorylase by vanadate.

Glycogen phosphorylase is progressively degraded during irradiation with near UV light in the presence of vanadate. The pattern of protein cleavage by monovanadate is characterised by fewer peptides than that by decavanadate, which leads to fragmentation in a ligand dependent way. In both instances, the initial cleavage releases a peptide of 82,000 daltons which accounts for the N-terminal portion of the subunit, including the regulatory phosphorylation site.

Autoradiography↗
PubMed1991

Antibiotic prophylaxis of wound infections in skin surgery.

A controlled prospective study of 2165 outpatients undergoing skin surgery was performed to evaluate the utility and the effects of several antibiotic schedules for prophylaxis of wound infections. The patients were divided into four groups. Twenty-three of the 541 group A patients, given no antibiotics, had wound infections. Eight of the 542 group B patients, given systemic antibiotics from immediately after surgery until the third day, had wound infections. Four of the 540 group C patients, treated only with local sterile antibiotic powder sprinkled into the wound during surgery, had wound infections develop, and only one infection occurred in the 542 group D patients given systemic antibiotics from 2 days before surgery until the second day after surgery. This last schedule was the best for prophylaxis of wound infections in contamination-prone regions. Local antibiotic administration is a simple method for prevention of infections in routine skin surgery.

Administration, Cutaneous↗
PubMed1990

Vanadate promotes photooxidative cleavage and inactivation of muscle phosphofructokinase.

During irradiation in the presence of decavanadate, the subunits of phosphofructokinase underwent progressive degradation to a fragment of about 78,000 daltons. This cleavage pattern was altered when the photoirradiation was performed in the presence of monomeric vanadate with formation of several smaller peptides. The specificity of the decavanadate induced cleavage was proved by the resistance of other enzymes to the treatment and by the effects of phosphofructokinase ligands. During irradiation, the activity of the enzyme declined. Differences between the rate of inactivation and of cleavage of enzyme subunits suggest the occurrence of multiple processes.

Ammonia↗
PubMed1989

Inactivation of skeletal-muscle UDP-glucose pyrophosphorylase by reaction with carboxylate-directed reagents.

Skeletal-muscle UDP-glucose pyrophosphorylase is inactivated by reaction with 2-ethoxy-N-(ethoxy-carbonyl)-1,2-dihydroquinoline (EEDQ) and 1-(3-dimethylaminopropyl-3-ethylcarbodi-imide (EDAC), two reagents specific for carboxylate groups. The former reagent is a more effective inactivator than EDAC. Although no evidence of reversible enzyme-reagent complexes of the affinity-labelling type was obtained by kinetic analysis of the inactivation, the selective protection of UDP-glucose pyrophosphorylase activity against inactivation by EEDQ in the presence of uridine substrates is indicative of an active-site-directed effect. The results are consistent with the hypothesis that EEDQ modifies a single carboxylate group located in a hydrophobic domain close to the substrate-binding site, leading to enzyme inactivation. In contrast, the reaction between UDP-glucose pyrophosphorylase and EDAC appears to involve a different region of the enzyme.

Animals↗