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Biomedical subjects

M Signorini

Publications and source records attributed to M Signorini.

At least 19 recordsLinked to original sources
PubMed1995

Inactivation and cleavage of liver 6-P-gluconate dehydrogenase during irradiation in the presence of vanadate.

Lamb liver phosphogluconate dehydrogenase is inactivated and selectively cleaved during irradiation in the presence of vanadate. Under our experimental conditions, the correlation between the species of vanadate in solution and rates of enzyme inactivation and cleavage indicates tetravanadate as the most likely photosensitizing agent, in agreement with previous data on other proteins. The enzyme is inactivated more rapidly at acidic pH and is partially protected by the coenzyme NADP, but not by the substrate phosphogluconate. Complete inactivation is obtained when only half of the protein is cleaved into smaller peptides. Differences in the pattern of the peptides produced are observed when irradiation is carried out in phosphate rather than in Hepes buffer: in the former instance cleavage results into formation of a main peptide of 47 kDa, while in latter case two additional peptides of 31 and 25 kDa are produced.

Animals↗
PubMed1995

Transglutaminase-catalyzed polymerization of troponin in vitro.

In the presence of calcium ions, tissue transglutaminase catalyzes the polymerization of skeletal muscle troponin to high molecular weight insoluble aggregate. The specific action of transglutaminase is proved by the isolation of glutamyl-spermidine isopeptide derivatives. The process involves mainly the troponin T subunit (TnT), with formation of dimers and trimers of TnT, which were reactive with specific antibodies by immunoblotting. Furthermore when incubation is carried out in the presence of radioactive polyamines, the label is incorporated selectively into TnT subunits.

Animals↗
PubMed1995

Superior orbital fissure syndrome complicating zygomatic fractures. Pathogenesis and report of a case. Case report.

Superior orbital fissure syndrome complicates zygomatic fractures either when the nerves that cross the fissure are damaged by bone fragments, or when the increased pressure in the orbit at the time of the injury compresses the nerves against the rim of the fissure. Oedema and bleeding may also have the same effect. We present a patient who was treated conservatively, and the ophthalmological problem subsided, although not completely, within a year.

Blepharoptosis↗
PubMed1995

[Ear prostheses in burns of the external ear. Technical notes].

Ear reconstruction is best performed with autologous tissue. However, there are selected cases in which a prosthesis may be preferred. Some patients are unwilling to undertake multiple surgical procedures, others do not accept the chest wall scar. More importantly, in severe post burn cases, the scars in the periauricular region can truly compromise the outcome of an autologous reconstruction. In such cases, the authors perform a prosthetic reconstruction which is anchored to the cranial bone by means of osteointegrated titanium screws. The method described here has been modified compared to the original Bränemark system. A new microscrew design allows the implants to be inserted in a single surgical procedure. A magnetic anchoring system avoids cumbersome external rods, and the overall size of the masses emerging from the skin is significantly reduced. These improvements increase patient comfort and compliance.

Bioprosthesis↗
PubMed1995

Purification and properties of 6-phosphogluconate dehydrogenase from beet leaves.

We have purified to homogeneity 6-Phosphogluconate dehydrogenase from leaves of silver beet (Beta vulgaris L.) by means of cation-exchange and affinity chromatography. The enzyme is a homodimer of 52 kDa subunits; it catalyzes NADP dependent oxidation of 6-P-gluconate with Michaelian substrate saturation. The activity is affected by some intermediates of carbohydrate metabolism, particularly erythrose-4-P. Subcellular fractionation studies indicate the cytosolic location of the enzyme.

Chromatography, Affinity↗
PubMed1994

Self-expanding prostheses complicating augmentation mammoplasties.

A new and serious complication was experienced by patients of three independent surgeons following routine augmentation procedures. In each case reported, double-lumen prostheses had been used. All cases were reoperated with a diagnosis of capsular contracture. However, at surgery it was found that the outer lumen of the prostheses had overfilled with 60-160 cc of interstitial fluid, probably because of an osmotic gradient. The possible causes of this unfortunate complication are considered.

Adult↗
PubMed1994

Contraction and growth of deep burn wounds covered by non-meshed and meshed split thickness skin grafts in humans.

A group of 18 burned patients was excised between days 2 and 5 postburn days, while 20 patients were operated later, between days 25 and 35 postburn. After early excision the wounds covered with meshed grafts contracted to a mean wound size of 56 per cent while the wounds covered with non-meshed grafts contracted to a mean wound size of 64 per cent. After late excision wounds covered with meshed grafts contracted to a mean wound size of 40.5 per cent while wounds covered with non-meshed grafts contracted to a mean wound size of 51.5 per cent. With early excision, meshed grafts grew back to a size of 78.5 per cent while non-meshed grafts grew back to a size of 91 per cent. With late excision, meshed grafts grew back to a size of 69.5 per cent while non-meshed grafts grew back to a size of 75.5 per cent.

Adolescent↗
PubMed1994

The surgical anatomy of the subcutaneous fascial system of the scalp.

The surgical anatomy of the fascial layers and vascularization of the scalp was studied by means of 11 bilateral cadaver dissections. This article is organized as follows: first, a description of the layers and fasciae of the scalp and their relationships with the main vascular structures, and then a description of the histological structure of the subgaleal fascia (composed of multiple connective vascularized sheets that glide over one another) and of its blood supply. In our dissections, we found the constant topographic distribution of the major perforant vessels to the subgaleal tissues as follows: in the temporal region, perforant vessels from the superficial temporal artery near and 10 to 14 cm above the zygomatic arch, where the superficial temporal artery leaves the surface of the galea to enter the superficial subcutaneous tissue, and in the fronto-parieto-occipital region, many small perforant vessels evenly entering the subgaleal plane every 5 to 10 mm. These findings could lead to greater use of fascial or composite flaps from the scalp region.

Arteries↗
PubMed1994

Utility of topical benzoyl peroxide for prevention of surgical skin wound infection.

BACKGROUND: Benzoyl peroxide is a powerful oxiding agent with broad spectrum germicidal activity and good liposolubility. Therefore, it may represent a good agent for prevention of wound infection in areas with high density of sebaceous glands. OBJECTIVE: The aim of this study was to analyze the effectiveness of topical benzoyl peroxidase gel for prevention of surgical skin wound infections in the centrofacial area. METHODS: A prospective study was performed on 673 patients. The patients were divided into two groups. Group A, 335 patients, was given no antibacterial prophylaxis. In group B, 338 patients, prophylactic medication with a gel containing 10% benzoyl peroxide was performed once a day for the 7 days before the surgery. RESULTS: Thirteen of 673 patients had wound infections (1.93%). Eleven of these 13 patients were in group A (3.24%) and two were in group B (0.59%) (P < .01). CONCLUSIONS: Topical benzoyl peroxide is an efficacious, harmless, and inexpensive agent for prevention of wound infections in seborrheic regions.

Administration, Topical↗
PubMed1993

Structural investigation of transglutaminase by Fourier transform infrared spectroscopy.

The secondary structure of transglutaminase was investigated by Fourier transform infrared spectroscopy. Spectra of the protein in both H2O and 2H2O were analyzed by deconvolution and second derivative methods in order to observe the overlapping components of the amide-I band. The quantitative analysis of the amide-I-band components was made by a curve-fitting procedure. The protein was studied in the absence and in the presence of 1 mM GTP, 1 mM Ca2+ and 1 mM GTP/1 mM Ca2+. The quantitative analysis of infrared spectra revealed that no remarkable changes in the secondary structure of the enzyme are induced by GTP, Ca2+ or Ca2+/GTP. Major changes, however were observed in the thermal-denaturation behavior of the protein. The protein showed maximum of denaturation at temperatures over 50-55 degrees C in the absence or in the presence of 1 mM Ca2+ and over 55-60 degrees C in the presence of 1 mM GTP or 1 mM Ca2+/1 mM GTP. The results obtained indicate that GTP induces a stabilization of the tertiary structure of the enzyme, even in the presence of 1 mM Ca2+. The thermal denaturation patterns of the protein suggest the occurrence of Ca(2+)-dependent aggregation.

Enzyme Stability↗
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↗