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G Poletti

Publications and source records attributed to G Poletti.

At least 19 recordsLinked to original sources
PubMed2006

Atomic force microscopy characterization of Xenopus laevis oocyte plasma membrane.

We used atomic force microscopy (AFM) to characterize the plasma membrane of Xenopus laevis oocytes. The samples were prepared according to novel protocols, which allowed the investigation of the extra- and intracellular sides of the membrane, both of which showed sparsely distributed spherical-like protrusions. Regions with comparably sized and densely packed structures arranged in an orderly manner were visualized and dimensionally characterized. In particular, two different arrangements, hexagonal and square packing, were recognizable in ordered regions. The lateral dimension of structures visualized on the external side had a normal distribution centered on 25.5 +/- 0.3 nm (mean value +/- SE), whereas that on the intracellular side showed a normal distribution centered on 30.2 +/- 0.8 nm. The height of the protrusions was 2-5 nm on the external side and 1-3 nm on the intracellular side. The mean number of structures on the external and intracellular sides of the plasma membrane was about 1000 microm(-2) and 850 microm(-2) respectively. Trypsin treatment greatly decreased the size of the membrane protrusions, thus confirming the proteic nature of the structures. These results show that AFM is a useful tool for structural characterization of proteins in a native eukaryotic membrane.

Animals↗
PubMed2006

Atomic force microscopy imaging of actin cortical cytoskeleton of Xenopus laevis oocyte.

In this study we report an atomic force microscopy (AFM) investigation of the actin cortical cytoskeleton of Xenopus laevis oocytes. Samples consisted of inside-out orientated plasma membrane patches of X. laevis oocytes with overhanging cytoplasmic material. They were spread on a freshly cleaved mica surface, subsequently treated with Triton X-100 detergent and chemically fixed. The presence of actin fibres in oocyte patches was proved by fluorescence microscopy imaging. Contact mode AFM imaging was performed in air in constant force conditions. Reproducible high-resolution AFM images of a filamentous structure were obtained. The filamentous structure was identified as an actin cortical cytoskeleton, investigating its disaggregation induced by cytochalasin D treatment. The thinnest fibres showed a height of 7 nm in accordance with the diameter of a single actin microfilament. The results suggest that AFM imaging can be used for the high-resolution study of the actin cortical cytoskeleton of the X. laevis oocyte and its modifications mediated by the action of drugs and toxins.

Actins↗
PubMed2006

Fire-eater's pneumonitis.

The authors report a case of acute respiratory failure that fulfils the diagnostic criteria for fire-eater's pneumonitis; pathological features, usually described only in experimental works on animals, are also discussed.

Adult↗
PubMed2005

Study of modifiable risk factors for asthma exacerbations: virus infection and allergen exposure increase the risk of asthma hospital admissions in children.

BACKGROUND: Asthma exacerbation is the most common cause of hospital admission in children. A study was undertaken to investigate the importance of allergen exposure in sensitised individuals in combination with viral infections and other potentially modifiable risk factors precipitating asthma hospital admission in children. METHODS: Eighty four children aged 3-17 years admitted to hospital over a 1 year period with an acute asthma exacerbation (AA) were matched for age and sex with two control groups: stable asthmatics (SA) and children admitted to hospital with non-respiratory conditions (IC). Risk factors were assessed by questionnaires and determination of allergen sensitisation, home allergen exposure, pollen exposure, and respiratory virus infection. RESULTS: Several non-modifiable factors (atopy, duration of asthma) were associated with increased risk. Among the modifiable factors, pet ownership, housing characteristics, and parental smoking did not differ between the groups. Regular inhaled corticosteroid treatment was significantly less common in the AA group than in the SA group (OR 0.2, 95% CI 0.1 to 0.6; p = 0.002). A significantly higher proportion of the AA group were virus infected (44%) and sensitised and highly exposed to sensitising allergen (76%) compared with the SA (18% and 48%) and IC groups (17% and 28%; both p<0.001). In a multiple conditional logistic regression (AA v SA), allergen sensitisation and exposure or virus detection alone were no longer independently associated with hospital admission. However, the combination of virus detection and sensitisation with high allergen exposure substantially increased the risk of admission to hospital (OR 19.4, 95% CI 3.7 to 101.5, p<0.001). CONCLUSIONS: Natural virus infection and real life allergen exposure in allergic asthmatic children increase the risk of hospital admission. Strategies for preventing exacerbations will need to address these factors.

Adolescent↗
PubMed2004

Reported versus confirmed wheeze and lung function in early life.

AIMS: To investigate the relation between parentally reported wheeze (unconfirmed), physician confirmed wheeze, and subsequent lung function. METHODS: Children at risk of allergic disease (one parent atopic) were recruited antenatally and followed prospectively from birth. During the first three years of life parents were asked to contact the study team if their child was wheezy. The presence of wheeze was confirmed or not by the primary care or study physician. Respiratory questionnaire and specific airway resistance measurement (sR(aw), body plethysmograph) were completed at age 3 years. RESULTS: A total of 454 children were followed from birth to 3 years of age. One hundred and eighty six (40.9%) of the parents reported their child wheezing in the first three years of life, and in 130 (28.6%) the wheeze was confirmed. A total of 428 children attended the three year clinic review, of whom 274 (64%) successfully carried out lung function tests. There was no significant difference in sR(aw) (kPa.s; geometric mean, 95% CI) between children who had never wheezed (n = 152; 1.03, 1.00 to 1.06) and those with a parentally reported but unconfirmed wheeze (n = 36; 1.02, 0.96 to 1.07, p = 1.00). sR(aw) was significantly higher in children with a physician confirmed wheeze (n = 86; 1.17, 1.11 to 1.22, p < 0.001) compared to those with no history of wheeze or with unconfirmed wheeze. CONCLUSIONS: Children with physician confirmed wheeze have significantly poorer lung function compared to those with parentally reported but unconfirmed and those who have never wheezed. A proportion of parents may have little understanding of what medical professionals mean by the term "wheeze".

Analysis of Variance↗
PubMed2003

Poly(lactide-co-glycolide) microspheres containing bupivacaine: comparison between gamma and beta irradiation effects.

The beta- and gamma-irradiation effects on stability of microspheres made of poly(lactide-co-glycolide) 50:50 copolymer (PLGA) containing bupivacaine (BU) were studied. Microspheres containing 10, 25, and 40% w/w, respectively, of BU were prepared by spray drying and irradiated in air with beta- and gamma-irradiation at a dose of 25 kGy. Morphology (atomic force microscopy, particle-size analysis), physico-chemical characteristics (DSC and FT-IR spectroscopy), drug content and in vitro dissolution profile of microspheres were all determined; the stability of irradiated microspheres was evaluated over a 9-month period. The decrease of BU content in gamma-irradiated microspheres was almost always constant independent of the amount of BU per sample, therefore it was in inverse proportion to drug loading (range between 5 and 15%). BU release rate increased immediately after irradiation and increased slightly until 90 days of storage. As far as beta-irradiated microspheres are concerned, BU content decreased in a significant way (approximately 3%) only in microspheres containing 10% w/w of BU. Immediately after irradiation, drug release rate in beta-irradiated microspheres increased less than in the corresponding gamma-irradiated microspheres, and it did not change further over the following storage period. BU-loaded microspheres have been shown to be more stable against beta- than gamma-irradiation. AFM revealed that the surface roughness of the irradiated microspheres increases depending on irradiation. As such, if a parameter is quantifiable, it is proposed as a marker of degradation due to ionizing radiation.

Anesthetics, Local↗
PubMed2003

A comparative study between AFM and SEM imaging on human scalp hair.

A comparative study of AFM and SEM imaging of the same area of a human scalp hair has been carried out to determine the similarity and the differences between the two techniques. Sample preparation for SEM analysis requires a metallization step and vacuum exposure, both of which could potentially induce modifications to the surface details. By contrast, AFM is a suitable technique to evaluate any effect resulting from sample manipulation because it can be applied without any specific treatment. AFM analysis demonstrates that sample metallization is responsible for modifications to the surface details of hair, mainly comprising an increase in height of scale steps and of root mean square roughness together with variation in scale profiles. Sample treatments for SEM imaging are in general potentially responsible for surface modifications to the samples involved.

Hair↗
PubMed2000

Aortobronchial fistula after aortic dissection type B.

Although rare, aortobronchial fistula complicates thoracic aortic surgery. Correct diagnosis and the infectious nature of the lesion are the most important conditions to define, for the following best therapy. We presented a case of non-infectious postsurgical aortobronchial fistula, revealed by computed-tomographic scan and angiography procedure, treated with prosthetic graft replacement and broad spectrum antibiotic therapy. In the case of infection our policy is homograft replacement. Computed tomography, being able to make diagnosis, should be performed as the initial technique.

Aortic Dissection↗
PubMed2000

The lung as a target organ in patients with hematologic disorders.

The lung is one of the organs most severely affected by complications during the course of hematologic disorders. In the last years an impressive amount of progress has been made in clarifying the pathogenesis of lung diseases, particularly those occurring in conditions of severe immunosuppression such as bone marrow transplantion, acquired immunodeficiency syndrome or leukemia. Peculiar anatomical characteristics render the lung parenchyma highly susceptible to infections, but the clinical outcome is due not only to the injury induced by the pathogens but also to their interactions with inflammatory cells and particularly to the effects of a wide network of secreted cytokines. Polymorphonuclear cells, macrophages, lymphocytes and structural pulmonary cells (epithelial cells, interstitial cells) generate a variety of cytokines and growth factors which, in turn, may be responsible for the majority of the clinical effects in response to infections, such as those of Pneumocystis carinii and cytomegalovirus, but also to certain drugs or to radiation. The pathogenesis of graft-versus-host disease (GVHD) is still poorly understood, but animal models seem to demonstrate the involvement of a number of cytokines and growth factors, together with toxic effects induced by conditioning regimens.

Chemotaxis, Leukocyte↗
PubMed1999

Bjork-Shiley convexo-concave valve: is a prophylactic re-replacement justified?

BACKGROUND: The Bjork-Shiley convexo-concave (BS-CC) heart valves represent the improved model of the standard valve first introduced with a different design of the disc valve to ameliorate hemodynamic performances and reduce thromboembolic complications. About 86,000 BS-CC were implanted during 1979-1986 and of them a small number developed an intrinsic dysfunction resulting in sudden death. METHODS: From 1979 to 1986 we implanted in 117 patients (48 males, 69 females, mean age 46.35+/-12.47, range 8-65 years) 125 BS-CC. In 38.5% (45/117) of the cases heart valve replacement represented the second cardiac procedure after a previous closed heart digital commissurotomy. The mean size of the implanted prosthesis was 25.6+/-2.8 for aortic valve and 29.5+/-1.2 for mitral valve. RESULTS: Hospital mortality was 4.27% (5/117) and survival rate at 10 years is 71.4% and at 17 years 54.7% (Kaplan-Meier). At follow-up causes of death proved valve related in most of the patients but with no evidence of valve fracture. We had 1 case of sudden death in patients at high risk (largest size, aortic position) and 30 cases of death by unknown causes but they did not have an autopsy to confirm the cause of death. CONCLUSIONS: We conclude that in our population with BS-CC at the moment there is no indication for prophylactic replacement because of the higher risks of a reoperation (third or fourth in the 35.4% of our patients) than a strut fracture. Nevertheless we believe an autopsy mandatory in all these patients at risk, when sudden death occurs.

Adolescent↗
PubMed1999

Bovine pericardial bioprosthesis in mitral position. A ten-year follow-up.

BACKGROUND: The pericardial bovine prosthesis Pericarbon should offer some advantages in comparison with the former generations, because its development is focused on solving previous problems and resulted in the variation of the pericardial fixation method, of valve structure and of stent coating. This hypothesis was evaluated through a retrospective follow-up. METHODS: Between 1985 and 1989, 78 Pericarbon prostheses O 29 were implanted in mitral position by the same surgeon. All patients received warfarin for the first three months to maintain an International Normalized Ratio between 2.5 and 3.5; after which they received antiaggregant therapy indefinitely. With an average follow-up period of 7.34 years for a total of 573 patient-years, we evaluated perioperative and late mortality, late morbidity (thromboembolic and haemorrhagic events, reoperations, primary tissue failures, endocarditic events) and patient clinical conditions. RESULTS: Perioperative mortality was 1.28% (1/78), late mortality was 11.6% (9/77) with 5 valve-related deaths. 5-year survival was 93% and 10-year survival 97%. Fifteen patients required reoperation for prosthetic replacement, fourteen for primary tissue failure. There were ten minor thromboembolic events, one major event, one haemorrhage and one prosthetic endocarditis (the last two with patient exitus). After 10 years (75% of patients were in New York Heart Association class I-II. CONCLUSIONS: Besides the known better haemodynamic performance, Pericarbon bioprosthesis seems to present a survival and redofreedom curve comparable to the best porcine prosthesis, with less incidence of endocarditis, thromboembolic events and prosthesis leakage.

Aged↗
PubMed1998

Adjuvant adoptive immunotherapy with tumour-infiltrating lymphocytes and modulated doses of interleukin-2 in 22 patients with melanoma, colorectal and renal cancer, after radical metastasectomy, and in 12 advanced patients.

Adoptive tumour infiltrating lymphocytes (TIL) in combination with a modulated dosage of interleukin-2 (IL-2) can be used with acceptable toxicity in the treatment of immunogenic tumours. Following an experience of reinfusion in advanced melanoma, colorectal and renal cancer patients, treatment was given to disease-free patients after metastasectomy. The high risk of relapse and favourable ratio between reinfused TIL and possible microscopic residual disease determined this choice of adjuvant treatment. A group of 12 patients with advanced disease (7 melanoma, 4 colorectal carcinoma, 1 kidney carcinoma) were treated with TIL (median 5.8 x 10(10) cells) and IL-2 (West's schedule) modulated towards a lower dosage (from 12 to 6 MIU/day) in order to maintain an acceptable level of toxicity. As treatment was well tolerated, it was offered to another 22 patients in an adjuvant setting after metastasectomy (11 melanoma, 10 colorectal carcinoma, 1 renal cancer), the median dose of TIL reinfused being 4.95 x 10(10) cells. No objective response was observed in advanced patients: all patients progressed after a median of 1.5 months (0-8 months) and median survival was 8 months (3-22+ months). Thirteen patients from the second group are still disease-free after a median of 23+ months (9+ - 47+ months). The remaining 9 patients relapsed after a median of 5 months (3-18 months). Toxicity was moderate as clinical and hepatic/renal function parameters were used to assess the need for dose reductions. Consequently, there was great diversity in IL-2 dosages administered. In particular, there seemed to be a difference in IL-2 doses administered between disease-free cases and those who progressed (17.5 MIU/day versus 7 MIU/day in melanoma patients; 11.2 MIU/day versus 7.1 MIU/day in colorectal cancer patients). By contrast, no differences were observed between number of TIL reinfused and clinical response. Phenotypical characteristics of reinfused TIL were similar to those reported in the literature: 97% were CD3 and 92% were CD8. Aspecific cytolytic activity was evaluated on 12 cases whereas, in 2 melanoma cases, autologous tumour tissue was available for the specific cytotoxicity test. Perforin levels in TIL measured at the end of culture were generally high or very high. Cytokine levels were measured on the supernatant at the end of culture, with an estreme variability in results. Finally, delta chain and p56lck were histologically assessed on the resected tissue from which TIL were cultivated. There were virtually none of the former and a complete absence of the latter, which concurs with data reported in the literature. The same immunocytochemical analysis was carried out on TIL at the end of culture. This time an almost complete restoration of both functions was seen, especially in melanoma patients, who are still free from disease. The study is on-going and it has been decided to focus on disease-free patients after metastasectomy in order to increase the number and possibility of clinical and histological correlations.

Adolescent↗
PubMed1998

Twelve-year follow up with the Sorin Pericarbon bioprosthesis in the mitral position.

BACKGROUND AND AIMS OF THE STUDY: The aim of this study was to evaluate the long-term follow up of the Pericarbon pericardial bioprosthesis implanted in the mitral position. METHODS: Between January 1985 and January 1991, 78 patients (26 males, 52 females; mean age 56.9 +/- 7.8 years) underwent isolated mitral valve replacement with a Pericarbon valve. All bioprostheses were size 29 mm and implanted by the same surgeon. RESULTS: Total follow up was 663.2 pt-years and it was 97% complete. Early mortality was 1.3% (1/78); two minor cerebral embolisms were observed as early complications. At 12 years the overall survival rate was 85.0 +/- and valve-related survival 93.1 +/- 3.0%; freedom from embolic events was 83.0 +/- 4.5% and from endocarditis 98.7 +/- 1.3%. Freedom from primary tissue failure was 56.8 +/- 6.6%; it was 86.3 +/- 7.5% in patients aged > 60 years and 36.8 +/- 8.2% in younger patients. There were 27 reoperations, 26 for primary tissue failure, one for endocarditis. Comparison between basal and follow up echocardiographic studies showed a significant stenotic deterioration of the bioprosthesis and a negligible incidence of regurgitation. Morphological findings of explanted bioprostheses were characterized by stenotic and diffuse microcalcification, but no tissue tear was observed. CONCLUSIONS: These results confirm that the Pericarbon bioprosthesis is structurally safe and free from the fatigue problems which afflicted the first and second generation of pericardial valves. As with other tissue valves, the rate of calcification is age-dependent, suggesting preferential use of the Pericarbon prosthesis in elderly people.

Bioprosthesis↗
PubMed1998

[Correlation between malfunction of a bioprosthesis and deformation of a valve stent. Comparison of three different vale models].

BACKGROUND: Stent deformation seems to be effective in the long term performances of bioprostheses. METHODS: The Inward Banding Angle (IBA) of three different models of bioprostheses explanted during the period 1991-1992 at our Division of Cardiac Surgery in 45 different patients (26 males; 9 females; mean age 59.71 +/- 10.74, range 26-75) has been measured. Explanted valves were as follow: Hancock, (H = 13); Carpentier-Edwards (C = 14) e Xenomedica (X = 18). Primary tissue failure was the most common cause of re-operation (n = 30; 66.7%) but also endocarditis (n = 6; 13.3%) and paraprothetic leak (n = 10; 22.2%). A semi-quantitative score (0-4) was used to assess calcifications (1.51 +/- 1.56); tears (0.41 +/- 0.98); vegetation's (0.51 +/- 0.99) and fibrosis (2.7 +/- 1.27). The mean follow-up was 7.77 +/- 3.79 years (range 1.5 +/- 16 years). The mean IBA evaluated after explantation was 3.34 +/- 2.29 degrees. RESULTS: Statistical analysis showed a significance in term of IBA in the Hancock group vs Carpentier (P < 0.02); a less duration in the Xenomedica group vs H and C (p < 0.001) and an increased susceptibility to vegetation's and fibrosis in the Xvs C (p < 0.01) and H (p < 0.05) respectively. A suggestive correlation between IBA and time and between IBA and diameter was found but no statistical significance was observed. CONCLUSIONS: In conclusions, it is suggested that all materials tends to deform during time and a possible explanation of stent deformation can be the different material used in the stent fabrication. Moreover, mechanical stress and compression around the ring can be another mechanism of creep.

Adult↗
PubMed1995

[Multicenter comparative study of meropenem vs. imipenem in the intramuscular treatment of hospital infections of the urinary tract].

A clinical, multicentre, randomised, comparative study in 283 adult hospitalized patients was carried out to assess efficacy of meropenem in the treatment of complicated and non-complicated urinary tract infections, in comparison to imipenem/cilastatin. Both antibiotics were administered intramuscularly, at a dose of 500 mg bid. The two groups were homogeneous, as regards the distribution between male and female, the mean age of the patients, the severity of infections and the mean duration of treatment. Clinical results were assessed at the end of therapy and follow-up (4-6 weeks). Bacteriological results were assessed at 5-9 days post-treatment and at follow-up. As regards clinical and bacteriological results patients showing a satisfactory response rate were compared, at the end of the treatments using a Chi square test. With both treatments high satisfactory clinical and bacteriological response rates were seen. As regards clinical satisfactory responses (97% of meropenem assessable patients versus 90% of imipenem/cilastatin assessable patients), there was a statistically significant difference in favor of meropenem. The bacteriological outcome was successful (eradication) for 75% of assessable patients in each group. Most failures were seen in the complicated infections, even when pathogens usually sensitives to carbapenemics were initially isolated. Safety was good with both drugs; no withdrawals in any group of treatment was seen because of side effects. The local tolerance of meropenem was globally rated as good.

Adult↗