PubMed Health⌕ Search

Biomedical subjects

M Schenone

Publications and source records attributed to M Schenone.

9 recordsLinked to original sources
PubMed2001

Domain interactions between streptokinase and human plasminogen.

Plasmin (Pm), the main fibrinolytic protease in the plasma, is derived from its zymogen plasminogen (Plg) by cleavage of a peptide bond at Arg(561)-Val(562). Streptokinase (SK), a widely used thrombolytic agent, is an efficient activator of human Plg. Both are multiple-domain proteins that form a tight 1:1 complex. The Plg moiety gains catalytic activity, without peptide bond cleavage, allowing the complex to activate other Plg molecules to Pm by conventional proteolysis. We report here studies on the interactions between individual domains of the two proteins and their roles in Plg activation. Individually, all three SK domains activated native Plg. While the SK alpha domain was the most active, its activity was uniquely dependent on the presence of Pm. The SK gamma domain also induced the formation of an active site in Plg(R561A), a mutant that resists proteolytic activation. The alpha and gamma domains together yielded synergistic activity, both in Plg activation and in Plg(R561A) active site formation. However, the synergistic activity of the latter was dependent on the correct N-terminal isoleucine in the alpha domain. Binding studies using surface plasmon resonance indicated that all three domains of SK interact with the Plg catalytic domain and that the beta domain additionally interacts with Plg kringle 5. These results suggest mechanistic steps in SK-mediated Plg activation. In the case of free Plg, complex formation is initiated by the rapid and obligatory interaction between the SK beta domain and Plg kringle 5. After binding of all SK domains to the catalytic domain of Plg, the SK alpha and gamma domains cooperatively induce the formation of an active site within the Plg moiety of the activator complex. Substrate Plg is then recognized by the activator complex through interactions predominately mediated by the SK alpha domain.

Binding Sites↗
PubMed2001

Structure and binding determinants of the recombinant kringle-2 domain of human plasminogen to an internal peptide from a group A Streptococcal surface protein.

The X-ray crystal structure of a complex of a modified recombinant kringle-2 domain of human plasminogen, K2Pg[C4G/E56D/L72Y] (mK2Pg), containing an upregulated lysine-binding site, bound to a functional 30 residue internal peptide (VEK-30) from an M-type protein of a group A Streptococcus surface protein, has been determined by molecular replacement methods using K4Pg as a model, and refined at 2.7 A resolution to a R-factor of 19.5 %. The X-ray crystal structure shows that VEK-30 exists as a nearly end-to-end alpha-helix in the complex with mK2Pg. The final structure also revealed that Arg17 and His18 of VEK-30 served as cationic loci for Asp54 and Asp56 of the consensus lysine-binding site of mK2Pg, while Glu20 of VEK-30 coordinates with Arg69 of the cationic binding site of mK2Pg. The hydrophobic ligand-binding pocket in mK2Pg, consisting primarily of Trp60 and Trp70, situated between the positive and negative centers of the lysine-binding site, is utilized in a novel manner in stabilizing the interaction with VEK-30 by forming a cation-pi-electron-mediated association with the positive side-chain of Arg17 of this peptide. Additional lysine-binding sites, as well as exosite electrostatic and hydrogen bonding interactions involving Glu9 and Lys14 of VEK-30, were observed in the structural model. The importance of these interactions were tested in solution by investigating the binding constants of synthetic variants of VEK-30 to mK2Pg, and it was found that, Lys14, Arg17, His18, and Glu20 of VEK-30 were the most critical amino acid binding determinants. With regard to the solution studies, circular dichroism analysis of the titration of VEK-30 with mK2Pg demonstrated that the peptidic alpha-helical structure increased substantially when bound to the kringle module, in agreement with the X-ray results. This investigation is the first to delineate structurally the mode of interaction of the lysine-binding site of a kringle with an internal pseudo-lysine residue of a peptide or protein that functionally interacts with a kringle module, and serves as a paradigm for this important class of interactions.

Amino Acid Sequence↗
PubMed2000

[Translabial ultrasonography in the diagnosis of stress urinary incontinence in women].

The target of this work is to evaluate the translabial ultrasonography (US) reliability as valid alternative to chain cystography in the pre and post operative assessment of patients with stress urinary incontinence (SUI). From June 1996 to May 1999, we studied 448 patients ranging in age from 35 to 90 years old with SUI from defect of anatomic support. Patients underwent translabial ultrasonography. The translabial US was performed with the patient in lithotomic position using a linear 7.5 MHz probe. The bladder was slightly filled, and the probe positioned longitudinally at the introitus to evaluate downwards and posterior rotation of bladder neck and urethra in basal conditions as well as during the abdominal strain. The evaluation of the anterior urethral angle of the 448 patients who underwent translabial US showed that, during the abdominal strain, all the patients with SUI had a very significative rotation of the urethral axis compared to continent women. Translabial US is a quick, simple, reliable non-invasive procedure. It may be used routinely for the pre and post-operative evaluation of anti-incontinence surgery.

Adult↗
PubMed1999

[Giuliani's method of anterio-lateral transabdominal muscle splitting and nerve preservation for kidney tumors].

OBJECTIVES: Anterolateral transabdominal incisions provide good exposure for supramesocolonic and inframescolonic surgery. However, these incisions section and denervate the rectus abdominis, oblique and transversus abdominis muscles with marked loss of active muscle control in a large number of patients. In 1974, Giuliani described an anterolateral transbdominal approach for renal tumours, which provides good visualization and good access to the renal pedicle, as well as good exposure caudally as far as the aortic bifurcation and cranially as far as the diaphragm. The authors report a new anatomical technique using this incision, which splits the muscles and preserves the nerves thereby avoiding the abdominal muscle hypotonia. MATERIAL AND METHODS: From March 1996 to March 1998, Giuliani's surgical incision was performed in 35 patients undergoing radical nephrectomy for renal cancer (24 on the left side and 11 on the right side). The mean age of the patients was 63.2 years (range: 42 to 80 years) and the mean follow-up was 11.6 months. RESULTS: Tone and active control of muscles of the abdominal wall were completely preserved in all of these 35 patients. However, all patients presented a slight sensory loss in the low portion of the transverse skin incision close to the umbilicus, which improved with time and resolved completely in about 50% of cases. CONCLUSION: The mahor advantage of this anatomical incision compared to the conventional technique is to eliminate permanent functional deficits and hypotonia of the abdominal wall. This anatomical approach also allows easy and perfectly safe wound closure in layers, by reconstructing the anterior abdominal wall.

Abdominal Muscles↗
PubMed1998

Role of impression cytology during hypovitaminosis A.

AIMS: Evaluation of the morphological damage to the ocular surface of patients operated for biliopancreatic diversion for pathological obesity and the correlation of impression cytology with vitamin A plasma levels, adaptometry, and other general variables. METHODS: 48 patients (15 males, 33 females, age range 21-73) and 34 normal subjects were examined with fluorescein and rose bengal, a plasma dose of vitamin A, and adaptometry. The results of the various tests were subdivided into three levels (0 = normal, 1 = moderately altered, 2 = seriously altered). The impression cytology and adaptometry results were correlated with vitamin A levels and other patient data (age, nutritional condition, time since operation, percentage weight loss). All the examinations were repeated after intramuscular therapy with vitamin A. RESULTS: Corneoconjunctival alterations visible with fluorescein and rose bengal staining were present in 67.7% of cases, impression cytology alterations in 93.7%, adaptometric alterations in 82.2%; vitamin A plasma levels were below normal in 95.8% of cases. After the therapy with vitamin A a significant reduction was found for every examination. The correlation between impression cytology and adaptometry and vitamin A plasma levels and between corneoconjunctival alterations and vitamin A plasma levels was significant. There was no significant correlation between impression cytology and nutritional condition, age time since operation, and percentage weight loss. CONCLUSION: These results show impression cytology is a specific indicator for hypovitaminosis A because it is not influenced by other factors related to the general condition of the patient. Many patients with hypovitaminosis A not demonstrating ocular symptoms of changes visible with fluorescein and rose bengal showed alterations with impression cytology.

Adaptation, Ocular↗
PubMed1998

Echobiometric evaluation of the axial length of the eye and intraocular lens calculation in pseudophakic eyes: our experience.

Intraocular lens (IOL) power calculation in 46 pseudophakic eyes (extracapsular cataract extraction with IOL in posterior chamber), utilizing a Javal keratometer, a Sonomed A 2000 echobiometer (probe 10 MHz, velocity=1,548 m/s) and the SRK2 formula, although there was a statistically significant reduction of the axial length, both in normal and hyperopic eyes, demonstrated no statistically significant differences of IOL power, when compared to the power previously calculated in the phakic eye.

Aged↗
PubMed1996

Intravesical idarubicin: a dose-finding study.

A total of 12 patients with completely resected, recurrent papillary tumors of the bladder were entered into a dose-finding study using intravesical idarubicin, a new anthracycline agent that has been shown in vitro to be more active than doxorubicin or daunorubicin, its parental compound. Patients were scheduled to receive eight weekly instillations with the following dose levels: 6.5, 12.5, and 20 mg, all of them diluted in 50 ml saline. Each dose level was initially studied in 3 patients. Dose escalation in the individual patients was not allowed so as to avoid undue toxicity and to evaluate the cumulative toxicity induced by each dose level. Overall, 4 patients were withdrawn due to severe local toxicity (chemocystitis) after a median of 2 instillations (range 1-3) and 3 more patients refused to continue treatment due to mild to moderate toxicity after a median of 4 instillations (range 2-4). Both the patients treated with 20 mg idarubicin and 2 of the 6 patients treated with 12.5 mg were withdrawn due to local toxicity. In contrast, no systemic toxicity was encountered at any dose level. We conclude that doses ranging from 6.5 to 12.5 mg and concentrations varying between 0.125 and 0.250 mg/ml are more appropriate for phase II studies, implying repeated instillations. At these doses and concentrations, however, it is unlikely that idarubicin might be more active than doxorubicin or epirubicin, whereas it might be more toxic.

Administration, Intravesical↗