Biomedical subjects

G Zanetti

Publications and source records attributed to G Zanetti.

At least 37 records · Page 2Linked to original sources

PubMed2001

An integrated simulator for surgery of the petrous bone.

This paper describes work being undertaken as part of the IERAPSI (Integrated Environment for the Rehearsal and Panning of Surgical Intervention) project. The project is focussing on surgery for the petrous bone, and brings together a consortium of European clinicians and technology providers working in this field. The paper presents the results of a comprehensive user task analysis that has been carried out in the first phase of the IERAPSI project, and details the current status of development of a pre operative planning environment and a physically-based surgical simulator.

Cochlear Implantation↗

PubMed2001

[Epidemiology and physiopathology of urinary incontinence after radical prostatectomy].

Beginning in the 1980s, a series of anatomical discoveries were introduced to modify the classic retropubic radical prostatectomy proposed by Millin in 1942 in an effort to reduce intra and postoperative complications such as intraoperative bleeding and postoperative erectile dysfunction and incontinence. Urinary incontinence post retropubic "anatomical" radical prostatectomy remains a distressing problem for the patient and the physician rating from 6 to 20% even in the hands of experienced surgeons from high volume Academic Centers. The reason for the discrepancy in results is unclear and should be searched in surgical experience of the surgeon, volume of surgical activity of the Center, and selection of the patients undergoing the radical retropubic procedure. In the Literature we identified methodological factors which can bias the data on post radical retropubic prostatectomy such as 1) Consensus is lacking on definition of continence and/or incontinence following radical retropubic prostatectomy 2) Different surgical techniques are compared: sphincter damaging, versus repairing, versus preserving; bladder neck sparing versus non sparing; nerve sparing versus non sparing 3) Patients with preoperative urinary incontinence are included in the series and the preoperative continence status is not known. 4) Different timing in registration of incontinence. 5) Different methods in data collection. This latter seems to be the most important reason for discrepancy in the collection of the data. Self administered questionnaires oriented to evaluate incontinence analyzed by a third party seem to be the most powerful and objective tool for post prostatectomy incontinence rating. Post prostatectomy incontinence may be attributed to sphincter dysfunction as a result of surgical injury during prostatic surgery and/or to bladder dysfunction including detrusor instability and decreased compliance resulting in stress or urge or mixed stress/urge postoperative incontinence. In the Literature bladder dysfunction is considered to be responsible or jointly responsible for post RRP incontinence in a rate as high as 93%. More recently, a major role is considered to be played in post RRP incontinence pathophysiology by intrinsic sphincter insufficiency. Rarely bladder dysfunction is an isolated cause of incontinence. Moreover the symptom of stress incontinence accurately predicts the finding of intrinsic sphincter deficiency. The apical dissection and the preservation of the intrinsic sphincter remain the most complex parts of RRP and the keys to the maintenance of postoperative urinary continence.

Humans↗

PubMed2000

The CrIIL reduction of [2Fe-2S] ferredoxins and site of attachment of CrIII using 1H NMR and site-directed mutagenesis.

The recently reported NMR solution structure of FeIIIFeIII parsley FdI has made possible 2D NOESY NMR studies to determine the point of attachment of CrIIIL in FeIIIFeIII...CrIIIL. The latter Cr-modified product was obtained by reduction of FeIIIFeIII parsley and spinach FdI forms with [Cr(15-aneN4) (H2O)2]2+ (15-aneN4 = 1,4,8,12-tetraazacyclopentadecane), referred to here as CrIIL, followed by air oxidation and chromatographic purification. From a comparison of NMR cross-peak intensities of native and Cr-modified proteins, two surface sites designated A and B, giving large paramagnetic CrIIIL broadening of a number of amino acid peaks, have been identified. The effects at site A (residues 19-22, 27, and 30) are greater than those at site B (residues 92-94 and 96), which is on the opposite side of the protein. From metal (ICP-AES) and electrospray ionization mass spectrometry (EIMS) analyses on the Cr-modified protein, attachment of a single CrIIIL only is confirmed for both parsley and spinach FdI and FdII proteins. Electrostatic interaction of the 3+ CrIIIL center covalently attached to one protein molecule (charge approximately -18) with a second (like) molecule provides an explanation for the involvement of two regions. Thus for 3-4 mM FeIIIFeIII...CrIIIL solutions used in NMR studies (CrIIIL attached at A), broadening effects due to electrostatic interactions at B on a second molecule are observed. Experiments with the Cys18Ala spinach FdI variant have confirmed that the previously suggested Cys-18 at site A is not the site of CrIIIL attachment. Line broadening at Val-22 of A gives the largest effect, and CrIIIL attachment at one or more adjacent (conserved) acidic residues in this region is indicated. The ability of CrIIL to bind in some (parsley and spinach) but not all cases (Anabaena variabilis) suggests that intramolecular H-bonding of acidic residues at A is relevant. The parsley and spinach FeIIFeIII...CrIIIL products undergo a second stage of reduction with the formation of FeIIFeII...CrIIIL. However, the spinach Glu92Ala (site B) variant undergoes only the first stage of reduction, and it appears that Glu-92 is required for the second stage of reduction to occur. A sample of CrIIIL-modified parsley FeIIIFeIII Fd is fully active as an electron carrier in the NADPH-cytochrome c reductase reaction catalyzed by ferredoxin-NADP+ reductase.

Amino Acid Sequence↗

PubMed2000

Competition between C-terminal tyrosine and nicotinamide modulates pyridine nucleotide affinity and specificity in plant ferredoxin-NADP(+) reductase.

Chloroplast ferredoxin-NADP(+) reductase has a 32,000-fold preference for NADPH over NADH, consistent with its main physiological role of NADP(+) photoreduction for de novo carbohydrate biosynthesis. Although it is distant from the 2'-phosphoryl group of NADP(+), replacement of the C-terminal tyrosine (Tyr(308) in the pea enzyme) by Trp, Phe, Gly, and Ser produced enzyme forms in which the preference for NADPH over NADH was decreased about 2-, 10-, 300-, and 400-fold, respectively. Remarkably, in the case of the Y308S mutant, the k(cat) value for the NADH-dependent activity approached that of the NADPH-dependent activity of the wild-type enzyme. Furthermore, difference spectra of the NAD(+) complexes revealed that the nicotinamide ring of NAD(+) binds at nearly full occupancy in the active site of both the Y308G and Y308S mutants. These results correlate well with the k(cat) values obtained with these mutants in the NADH-ferricyanide reaction. The data presented support the hypothesis that specific recognition of the 2'-phosphate group of NADP(H) is required but not sufficient to ensure a high degree of discrimination against NAD(H) in ferredoxin-NADP(+) reductase. Thus, the C-terminal tyrosine enhances the specificity of the reductase for NADP(H) by destabilizing the interaction of a moiety common to both coenzymes, i.e. the nicotinamide.

Amino Acid Sequence↗

PubMed2000

Increase in the prevalence of symptomatic upper urinary tract stones during the last ten years.

PURPOSE: In industrialized countries the prevalence of upper urinary tract stones has continually increased during the 20th century, but there are considerable differences between countries and also within the same country. To study whether there is still an increase in the frequency of renal stones, an investigation was undertaken to determine the prevalence of stone formers in a village near Milan, Italy, during two time periods, with an interval of 12 years. MATERIALS AND METHODS: Questionnaires were administered in 1986 and 1998 to all adult (age >25 years) occupants of two random samples of households in the village. Participants were asked whether they had experienced a kidney stone during their lifetime. RESULTS: The overall prevalence of stone formers among males was 6.8% in 1986 and 10.1% in 1998; that among females was 4.9% in 1986 and 5.8% in 1998. In all age classes, the respondents in the 1998 survey more frequently reported a history of stones than in 1986, but the prevalence of renal stones was significantly higher in 1998 than in 1986 only among males aged 31-40 and 51-60 years. The yearly incidence was estimated at 0.4%, with 0.6 and 0.18% in men and women, respectively. CONCLUSIONS: This marked increase in renal stones could be the result of environmental factors such as dietary habits and lifestyle, in particular the influence of an increased consumption of animal protein should be considered.

Adult↗

PubMed2000

Catheter insertion simulation with co-registered direct volume rendering and haptic feedback.

We have developed an experimental catheter insertion simulation system supporting head-tracked stereoscopic viewing of volumetric anatomic reconstructions registered with direct haptic 3D interaction. The system takes as input data acquired with standard medical imaging modalities and regards it as a visual and haptic environment whose parameters are interactively defined using look-up tables. The system's display, positioned like a surgical table, provide a realistic impression of looking down at the patient. Measuring head motion via a six degrees-of-freedom head tracker, good positions to observe the anatomy and identify the catheter insertion point are quickly established with simple head motion. By generating appropriate stereoscopic images and co-registering physical and virtual spaces beforehand, volumes appear at fixed physical positions and it is possible to control catheter insertion via direct interaction with a PHANToM haptic device. During the insertion procedure, the system provides perception of the effort of penetration and deviation inside the traversed tissues. Semi-transparent volumetric rendering augment the sensory feedback with the visual indication of the inserted catheter position inside the body.

Catheterization, Peripheral↗

PubMed1999

Interaction of the soluble recombinant PsaD subunit of spinach photosystem I with ferredoxin I.

Photosystem I of higher plants functions in photosynthesis as a light-driven oxidoreductase producing reduced ferredoxin. Its peripheral subunit PsaD has been identified as the docking site for ferredoxin I. With the aim of elucidating the structure-function relationship and the role of this subunit, a recombinant form of the spinach protein was produced by heterologous expression in Escherichia coli. The PsaD protein was synthesized in soluble form and purified to homogeneity. The interaction of the PsaD subunit with ferredoxin I was investigated using three different approaches: chemical cross-linking between the two purified proteins in solution, affinity chromatography of the PsaD subunit on a ferredoxin-coupled resin, and titration with ferredoxin of the protein fluorescence of the subunit. All these studies indicated that the isolated PsaD in solution has a definite conformation and maintains the ability to bind ferredoxin I with high affinity and specificity. The Kd value of the complex of PsaD and ferredoxin is in the nanomolar range, which is consistent with reported Km values for ferredoxin I photoreduction by thylakoid membranes. The ionic strength dependence of the K(d) suggests that the protein-protein interaction is at least partially electrostatic in nature. Nevertheless, none of the glutamate residues of the acidic cluster of residues 92-94 of ferredoxin I, which have been reported to be involved in the interaction with the subunit, seems to be essential for PsaD binding, as borne out by experiments using ferredoxin I mutants in positions 92-94.

Cross-Linking Reagents↗

PubMed1999

Meropenem (1.5 g/day) is as effective as imipenem/cilastatin (2 g/day) for the treatment of moderately severe intra-abdominal infections.

This multicentre, open-label, randomised trial compared meropenem (0.5 g/8 h) and imipenem/cilastatin (at the commonly used dosage of 0.5 g/6 h) in monotherapy in patients with moderately severe intra-abdominal infections (IAIs). In total, 161 patients were randomised (82 meropenem, 79 imipenem/cilastatin). The mean APACHE II scores in the two groups were 5.8 and 6.4, respectively. At the end of therapy, 65/71 (91.6%) evaluable meropenem recipients were clinically cured or improved, compared to 60/64 (93.8%) imipenem/cilastatin recipients. This difference and that in an intention-to-treat analysis (82.1 vs 86.1%, respectively), were not statistically significant. Both drugs were generally well tolerated. Thus, meropenem 0.5 g/8 h is as clinically effective and well tolerated as imipenem/cilastatin 0.5 g/6 h in moderately severe IAIs.

APACHE↗

PubMed1999

Relationship between surface properties and cellular responses to crystalline silica: studies with heat-treated cristobalite.

A fibrogenic sample of cristobalite dust, CRIS (crystalline silica of mineral origin), was heated to 1300 degrees C (CRIS-1300) to relate induced physicochemical modifications to cytotoxicity. Heating did not affect dust micromorphology and crystallinity, except for limited sintering and decreased surface area of CRIS-1300. Thermal treatments deeply affected surface properties. Electron paramagnetic resonance showed surface radicals progressively annealed by heating, mostly disappearing at >/=800 degrees C. Surface hydrophilicity or hydrophobicity, evaluated with water vapor adsorption, still showed some hydrophilic patches in CRIS-800, but CRIS-1300 was fully hydrophobic. Heating modified the biological activity of cristobalite. Cytotoxicity, tested on proliferating cells of the mouse monocyte macrophage cell line J774, showed that CRIS was cytotoxic and CRIS-800 was still cytotoxic, but CRIS-1300 was substantially inert. Cytotoxicity of CRIS to the rat lung alveolar epithelial cell line, AE6, as measured by colony forming efficiency, was greatly reduced for CRIS-800 and eliminated for CRIS-1300. The rate of lactate dehydrogenase release by rat alveolar macrophages was lowered for CRIS-800, and release was completely inactivated for CRIS-1300. The absence of surface radicals and the onset of hydrophobicity may both account for the loss of cytotoxicity upon heating. Differences observed between CRIS-800 and CRIS-1300, both fully deprived of surface radicals, indicate that hydrophobicity is at least one of the surface properties determining the cytotoxic potential of a dust.

Adsorption↗

PubMed1999

A productive NADP+ binding mode of ferredoxin-NADP + reductase revealed by protein engineering and crystallographic studies.

The flavoenzyme ferredoxin-NADP+ reductase (FNR) catalyzes the production of NADPH during photosynthesis. Whereas the structures of FNRs from spinach leaf and a cyanobacterium as well as many of their homologs have been solved, none of these studies has yielded a productive geometry of the flavin-nicotinamide interaction. Here, we show that this failure occurs because nicotinamide binding to wild type FNR involves the energetically unfavorable displacement of the C-terminal Tyr side chain. We used mutants of this residue (Tyr 308) of pea FNR to obtain the structures of productive NADP+ and NADPH complexes. These structures reveal a unique NADP+ binding mode in which the nicotinamide ring is not parallel to the flavin isoalloxazine ring, but lies against it at an angle of approximately 30 degrees, with the C4 atom 3 A from the flavin N5 atom.

Amino Acid Sequence↗

PubMed1999

A prospective study of recurrence rate and risk factors for recurrence after a first renal stone.

PURPOSE: We investigate further the recurrence rate and risk factors for recurrence in 300 consecutive patients who presented to our stone clinic after a first stone episode 7 to 17 years ago. MATERIALS AND METHODS: The medical records of the patients who presented consecutively with a first stone episode from 1980 to 1990 were studied and supplemented by a followup mail questionnaire and telephone interviews. At first visit serum samples were taken from all patients and 24-hour urine samples were collected for metabolic testing. RESULTS: A total of 195 patients were followed successfully, of whom 52 (27%) experienced symptomatic stone recurrence after a mean plus or minus standard deviation of 7.5+/-5.9 years. However, ultrasound examination of 36 symptom-free patients showed recurrent stones in 28%. Comparison of patients with or without recurrence confirmed that recurrence was not influenced by sex, family history of stones and urinary risk factors. However, age at onset of the disease was lower for patients who had 2 or more stones during followup than those who had only 1 stone or no recurrence. CONCLUSIONS: Stones can recur as long as 10 years after the first episode, although the rate is lower than previously reported. The metabolic evaluation after a first stone episode needs to be reappraised in terms of its cost-effectiveness, since recurrences do not seem to be predictable from standard laboratory tests.

Adolescent↗

PubMed1999

Evaluation of urinary level of NMP22 as a diagnostic marker for stage pTa-pT1 bladder cancer: comparison with urinary cytology and BTA test.

BACKGROUND: In the present study we compared the clinical value of two new specific tests for transitional cell carcinoma, urinary nuclear matrix protein (NMP22) levels and bladder tumor antigen (BTA) test, with that of urinary cytology in the follow-up of patients with superficial bladder cancer. MATERIALS AND METHODS: Hundred and five bladder cancer patients were recruited: 30 stage pTa and 45 stage pT1 (group A), and 30 with a history of bladder cancer but no recurrence at the time of the study (group B). Urine samples were collected before any instrumental manipulation of the genitourinary tract. All patients were negative for urinary tract infections at conventional urine analysis. RESULTS: NMP22 at a cutoff value of 6 U/ml showed a sensitivity of 83.3% in pTa cases and 97.7% in pT1 cases, with a false-positive rate of 23.3%. The BTA test was positive in 26.6% of patients with cancer stage pTa and in 66.6% of pT1 stage, with 30% false-positives in the non-neoplastic group. Urinary cytology, performed on three consecutive samples, was positive in 20% of patients with cancer stage pTa and in 64.4% of pT1 stage and did not show any false-positive cases. Stratifying the neoplastic patients according to lesion grade, NMP22 (at a cutoff value of 6 U/ml) was positive in 86.2% of G1, 97.2% of G2 and 90% of G3. BTA was positive in 37.9, 52.7 and 70% of G1, G2 and G3, respectively, while urinary cytology was positive in 37.9, 44.4 and 80%.

Adult↗

PubMed1999

Ultrasound-fluoroscopy guided access to the intrarenal excretory system.

The access to the collecting system can be performed under fluoroscopy computerized tomography, ultrasonographic, mixed ultrasonographic and fluoroscopic guidance. In this paper the creation of a percutaneous transparenchymal ultrasound-fluoroscopy guided access to the intrarenal collecting system completely performed by urologist for different purposes is presented. In five years 297 patients underwent 330 percutaneous kidney accesses to perform derivative nephrostomies (217 pts), percutaneous nephrolithotomies (37 pts), antegrade ureteral manoeuvres (34 pts), antegrade endopyelotomies (7 pts), transitional cell carcinoma of the upper tract resection (2 pts). 11 patients out of these had a percutaneous kidney access in a transplanted kidney. The percutaneous access was successful in 98% of the attemps. A posterior calyx of the lower group (74%), of the medium group (25%) or of the upper group (1%) was accessed. In 73 accesses the mean target calyx diameter was 12.8 mm (range 5-45 mm), the mean operative time 5.4 minutes and the mean fluoroscopy time 5.1 seconds. In 84.5% of the patients the access was performed under local anesthesia when a dilation of the tract was not required. Gross haematuria was observed in 3.9% of the accesses and an arterial lesion treated by embolization in 0.9% of the accesses. Blood transfusion was required in 0.3% of the patients. The ultrasound-fluoroscopy guided access is at least as precise as the fluoroscopy guided one moreover it makes the procedure less invasive and it makes more precise the surgical planning.

Fluoroscopy↗

PubMed1999

Interventional radiology in the treatment of uretero-pelvic-junction.

Numerous authors have reported successful results with both antegrade or retrograde endopyelotomy. Both procedures have proved to be efficient in primary as in secondary obstructions. Some additional etiological factors, such as crossing vessels high-grade hidronephrosis and poorly functioning kidney, may decrease the success rate of these minimally invasive techniques. The development of a cutting balloon catheter used under fluoroscopic control simplified the retrograde technique. This technique proved to be easier to perform than antegrade or retrograde endoscopic incision and did not require specialized instrumentation. In our experience 6 patients from 30 to 65 years old (average age 52) with an ureteropelvic-junction obstruction secondary to open surgery underwent endopyelotomy with the cutting balloon device. At the three month followup 4 patients had renographic patent ureteropelvic junction and no modifications were seen at one year follow up The retrograde endopyelotomy under fluoroscopic control seems to offer a rapid and effective treatment of UPJO. It is indicated for all primary and secondary UPJO obstruction apart forpatients with a concomitant renal stone or with high-insertion ureteropelvic junction.

Adult↗

PubMed1999

Permanent stenting in the treatment of ureteral strictures.

Permanent metallic stents have found wide application for use in the vascular and biliary systems and currently devices are also available for use in the urinary tract. Permanent stenting of the ureter has proven to be an useful option in the management of obstruction caused by external compression due to malignancy whereas the efficacy of permanent stenting in the treatment of benign ureteral strictures is still controversial. We treated three patients with benign ureteral strictures by implantation of a self-expanding endoluminal stent that resulted in ureteral patency persisting up to 24 months.

Adult↗

PubMed1999

Contact laser treatment for benign prostatic hypertrophy.

Transurethral resection of the prostate (TURP) is still the standard treatment of benign prostatic hypertrophy (BPH) but the surgical lasers recently introduced seem to offer the patient a very low perioperative complication rate, a short learning curve, the reduced operating time and the health care system a very low cost/benefit ratio. We report our personal experience with contact vaporizing laser ablation of the prostate (CLAP) paying attention to efficacy, safety and costs. Between December 94 and March 97, 67 pts (mean age 62.8 +/- 9 years) underwent CLAP for BPH (mean prostate volume 40.4 +/- 17.1 cc). Five pts presented coagulation disorders, five were renal transplant recipients and one had chronic renal failure requiring peritoneal dialysis. All patients were preoperatively submitted to digital rectal examination, transrectal prostatic ultrasound, dosage of serum PSA, determination of the International Prostatic Symptom Score (IPSS), the post voiding residual urine and maximum flow rate. All these exams were repeated at 1, 3, 6, 12 and 24 months after CLAP. The bladder pressure at maximum flow (Pdet-Qmax) was preoperatively determined in 23 patients and repeated at the six months follow up. For CLAP we used an SLT neodynium-YAG laser or diode laser with maximum potency 60 W. For statistical analysis we used Student's t-test for paired data. The mean operating time was 47.9 +/- 12.5 min (range 18-75 min) and the laser energy averaged 17.707 +/- 11.239 J (range 3000-58,000 J). The mean catheter time after CLAP was 2.5 days and the mean hospital stay was 4.8 days. No intraoperative complications occurred. Two patients 48/72 h after surgery presented macrohematuria requiring laser revision, three patients presented an acute urinary retention post catheter removal and one patient had acute prostatis. At the follow up, the IPSS score, Q max, Pdet-Qmax and PVU showed a significant statistical difference respect to baseline values. The prostate volume at the 180-day follow up was not significantly different from baseline values (42.1 +/- 16.8 cc vs 40.4 +/- 17.1 cc). Contact laser ablation of the prostate has been demonstrated to be efficacious and comparable to TURP in relieving BPH obstruction however the higher costs exceeding the TURP ones by 13%, the longer operative times and the lower durability of laser disobstruction impede to replace TURP with the CLAP.

Humans↗

PubMed1999

Successful surgical treatment of ''globus hystericus''.

We report the case of a 52-year old woman who presented with a 4-year history of depression associated with intermittent dysphagia and globus sensation for which she was admitted to a nursing home. Physical examination revealed a murmur on the right carotid artery, while the routine biochemical tests were normal. Chest computer tomography (CT) demonstrated the presence of an anomalous vessel departing from the aortic arch; angiography showed an aberrant right subclavian artery of large lumen and a severe stenosis at the origin of the right internal carotid artery. Surgical intervention was performed and dysphagia disappeared.

Journal Article↗

PubMed1998

Probing the function of the invariant glutamyl residue 312 in spinach ferredoxin-NADP+ reductase.

Ferredoxin-NADP+ reductase, the prototype of a large family of structurally related flavoenzymes, pairs single electrons carried by ferredoxin I and transfers them as a hydride to NADP+. Four mutants of the enzyme, in which Glu-312 was replaced with Asp, Gln, Leu, and Ala to probe the role of the residue charge, size, and polarity in the enzyme activity, have been heterologously expressed, purified, and characterized through steady-state, rapid kinetic studies, ligand-binding experiments, and three-dimensional structure determination by x-ray crystallography. The E312L mutant was the only one that was almost inactive (approximately 1%), whereas unexpectedly the E312A reductase was 10-100% active with the various acceptors tested. Rapid kinetic absorption spectroscopy studies demonstrated that flavin reduction by NADPH was impaired in the mutants. Furthermore, NADP(H) binding was partially perturbed. These functional and structural studies lead us to conclude that Glu-312 does not fulfil the role of proton donor during catalysis, but it is required for proper binding of the nicotinamide ring of NADP(H). In addition, its charge modulates the two one-electron redox potentials of the flavin to stabilize the semiquinone form.

Amino Acid Sequence↗