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Biomedical subjects

A Aiello

Publications and source records attributed to A Aiello.

At least 19 recordsLinked to original sources
PubMed2006

Maximum-likelihood estimation of Mueller matrices.

We show that the method of maximum-likelihood estimation, recently introduced in the context of quantum process tomography, can be applied to the determination of Mueller matrices characterizing the polarization properties of classical optical systems. Contrary to linear reconstruction algorithms, the proposed method yields physically acceptable Mueller matrices even in the presence of uncontrolled experimental errors. We illustrate our method with the case of an unphysical measured Mueller matrix taken from the literature.

Journal Article↗
PubMed2006

Angular spectrum of quantized light beams.

We introduce a generalized angular spectrum representation for quantized light beams. By using our formalism, we are able to derive simple expressions for the electromagnetic vector potential operator in the case of (a) time-independent paraxial fields, (b) time-dependent paraxial fields, and (c) nonparaxial fields. For the first case the well-known paraxial results are fully recovered.

Journal Article↗
PubMed2005

Role of spatial coherence in polarization tomography.

We analyze an experimental setup in which a quasi-monochromatic spatially coherent beam of light is used to probe a paraxial optical scatterer. We discuss the effect of the spatial coherence of the probe beam on the Mueller matrix representing the scatterer. We show that, according to the degree of spatial coherence of the beam, the same scattering medium can be represented by different Mueller matrices. This result should serve as a warning for experimentalists.

Computer Simulation↗
PubMed2005

Physical bounds to the entropy-depolarization relation in random light scattering.

We present a theoretical study of multimode scattering of light by optically random media, using the Mueller-Stokes formalism which permits us to encode all the polarization properties of the scattering medium in a real 4 x 4 matrix. From this matrix two relevant parameters can be extracted: the depolarizing power D(M) and the polarization entropy E(M) of the scattering medium. By studying the relation between E(M) and D(M), we find that all scattering media must satisfy some universal constraints. These constraints apply to both classical and quantum scattering processes. The results obtained here may be especially relevant for quantum communication applications, where depolarization is synonymous with decoherence.

Journal Article↗
PubMed2004

How to observe high-dimensional two-photon entanglement with only two detectors.

We propose a novel setup to investigate the entanglement of orbital angular momentum states living in a high-dimensional Hilbert space. We incorporate noninteger spiral phase plates in spatial analyzers, enabling us to use only two detectors. The two-photon states that are produced are not confined to a 2 x 2-dimensional Hilbert space, and the setup allows the probing of correlations in a high-dimensional space. For the special case of half-integer spiral phase plates, we predict that the Clauser-Horne-Shimony-Holt-Bell parameter S is larger than achievable for two qubits (S=2 sqrt[2]), namely, S=31 / 5.

Journal Article↗
PubMed2004

Ray splitting in paraxial optical cavities.

We present a numerical investigation of the ray dynamics in a paraxial optical cavity when a ray-splitting mechanism is present. The cavity is a conventional two-mirror stable resonator and the ray splitting is achieved by inserting an optical beam splitter perpendicular to the cavity axis. We show that depending on the position of the beam splitter the optical resonator can become unstable and the ray dynamics displays a positive Lyapunov exponent.

Journal Article↗
PubMed2003

Ray chaos in optical cavities based upon standard laser mirrors.

We present a composite optical cavity made of standard laser mirrors; the cavity consists of a suitable combination of stable and unstable cavities. In spite of its very open nature the composite cavity shows ray chaos, which may be either soft or hard, depending on the cavity configuration. This opens a convenient route for experimental studies of the quantum aspects of a chaotic wave field.

Journal Article↗
PubMed2003

Sustainable production of bioactive compounds from sponges: primmorphs as bioreactors.

Sponges [phylum Porifera] are a rich source for the isolation of biologically active and pharmacologically valuable compounds with a high potential to become effective drugs for therapeutic use. However, until now, only one compound has been introduced into clinics because of the limited amounts of starting material available for extraction. To overcome this serious problem in line with the rules for a sustainable use of marine resources, the following routes can be pursued; first, chemical synthesis, second, cultivation of sponges in the sea (mariculture), third, growth of sponge specimens in a bioreactor, and fourth, cultivation of sponge cells in vitro in a bioreactor. The main efforts to follow the latter strategy have been undertaken with the marine sponge Suberites domuncula. This species produces compounds that affect neuronal cells, such as quinolinic acid, a well-known neurotoxin, and phospholipids. A sponge cell culture was established after finding that single sponge cells require cell-cell contact in order to retain their telomerase activity, one prerequisite for continuous cell proliferation. The sponge cell culture system, the primmorphs, comprises proliferating cells that have the potency to differentiate. While improving the medium it was found that, besides growth factors, certain ions (e.g. silicate and iron) are essential. In the presence of silicate several genes required for the formation of the extracellular matrix are expressed (silicatein, collagen and myotrophin). Fe3+ is essential for the synthesis of the spicules, and causes an increased expression of the ferritin-, septin- and scavenger receptor genes. Furthermore, high water current is required for growth and canal formation in the primmorphs. The primmorph system has already been successfully used for the production of pharmacologically useful, bioactive compounds, such as avarol or (2'-5')oligoadenylates. Future strategies to improve the sponge cell culture are discussed; these include the elucidation of those genes which control the proliferation phase and the morphogenesis phase, two developmental phases which the cells in primmorphs undergo. In addition, immortalization of sponge cells by transfection with genomic DNA appears to be a promising way, since recent studies underscore the applicability of this technique for sponges.

Amino Acid Sequence↗
PubMed2002

Tamoxifen in the treatment of hepatocellular carcinoma: 5-year results of the CLIP-1 multicentre randomised controlled trial.

BACKGROUND: In 1998, when data of a meta-analysis on tamoxifen in the treatment of hepatocellular carcinoma (HCC) had suggested a little advantage for this treatment, we published the results of a multicenter randomised controlled trial, that showed no survival benefit for tamoxifen vs. control. Here we report an updated analysis of the study results 4.5 years after the closure of enrollment. METHODS: The study had a planned sample size of 480 patients. Patients with any stage HCC were eligible, irrespective of locoregional treatment. Tamoxifen was given orally, 40 mg/die, from randomisation until death. RESULTS: 496 patients were randomised by 30 Institutions from January 1995 to January 1997. Information was available for 477 patients. As of July 2001, 374 deaths (78%) were recorded, and median survival times were 16 and 15 months (p=0.54), in the control and tamoxifen arm. Data were further analysed separately for advanced patients and for those eligible to potentially curative locoregional treatments: relative hazard of death for patients receiving tamoxifen was equal to 0.98 (95% CI 0.76-1.25) for the former group and 1.38 (95% CI 0.95-2.01) for the latter. The prognostic score recently devised by our group (CLIP score) was, as expected, strictly correlated (p<0.0001) to the locoregional treatment received and strongly correlated with prognosis. CONCLUSIONS: the update of the present study confirms that tamoxifen is not effective in prolonging survivals, both in advanced patients and in those potentially curable and that the CLIP score is able to predict prognosis.

Carcinoma, Hepatocellular↗
PubMed2001

Messenger RNAs in synaptosomal fractions from rat brain.

Synaptosomal fractions from rat brain have been analyzed with semi-quantitative RT-PCR methods to determine their content of mRNAs coding for presynaptic, postsynaptic, glial, and neuronal proteins. Each mRNA was determined with reference to the standard HPRT mRNA. In our analyses, mRNAs were considered to be associated with synaptosomes only if their relative amounts were higher than in microsomes prepared in a polysome stabilizing medium, rich in Mg(++) and K(+) ions, or in the homogenate. According to this stringent criterion, the following synaptosomal mRNAs could not be attributed to microsomal contamination and were assumed to derive from the subcellular structures known to harbor their translation products, i.e. GAT-1 mRNAs from presynaptic terminals and glial processes, MAP2 mRNA from dendrites, GFAP mRNA from glial processes, and TAU mRNA from neuronal fragments. This interpretation is in agreement with the involvement of extrasomatic mRNAs in local translation processes.

Animals↗
PubMed2001

Cholecystoenteric fistula (CF) is not a contraindication for laparoscopic surgery.

BACKGROUND: Cholecystoenteric fistula (CF) is a rare complication of cholelithiasis. The aim of this study was to evaluate the safety and risk of complications when the laparoscopic approach is applied in patients with CF. METHODS: A questionnaire was mailed to all surgeons with experience of >100 cholecystectomies working in Naples, Italy, and the neighboring area. RESULTS: Between February 1990 and May 1999, 34 patients presented with cholecystoenteric fistula (0.2% of >15,000 laparoscopic cholecystectomies performed in the same period). These patients were allocated into two groups: the LT group (those who underwent laparotomic conversion after the diagnosis of CF), which consisted of 20 patients, four men and 16 women, with a mean age of 66.5 +/- 9.3 years (range, 46-85) and the LS group (laparoscopically treated patients), which consisted of 14 patients, three men and 11 women, with a mean age of 65.6 +/- 8.8 years (range, 51-74). They types of CF observed were as follows: in the former group of patients, cholecystoduodenal fistulas (n = 11, 55%), cholecystocolic fistulas (n = 5, 25%), cholecystojejunal fistulas (n = 3, 15%), and cholecystogastric fistulas (n = 1, 5%); in the latter group, cholecystoduodenal fistulas (n = 8, 5.1%), and cholecystocolic fistulas (n = 4, 28.6) and cholecystojejunal fistulas (n = 2, 14.3%). Stapler closure of CF was done in four LT patients and three LS patients with cholecystoduodenal fistula; it was also done in three LT patients and three LS patients with cholecystocolic fistula. Hand-sutured fistulectomy was performed in six LT patients and three LS patients with cholecystoduodenal fistula, in two LT patients with cholecystocolic fistula, and in all patients with cholecystojejunal or cholecystogastric fistula. There were no deaths or intraoperative complications in either group. One patient in the LT group developed a bronchopneumonia postoperatively. Postoperative hospital stay was significantly longer in LT patients-17 +/- 4 vs 3+/-1 days (p < 0.001). CONCLUSION: Cholecystoenteric fistula is an occasional intraoperative finding during laparoscopic cholecystectomy. The results of this study, which are based on the collective experiences of 19 surgeons, illustrate the growing success of the laparoscopic approach to this condition, including a decreasing rate of conversion to open surgery over the last 3 years.

Aged↗
PubMed2001

New bioactive sulfated metabolites from the Mediterranean tunicate Sidnyum turbinatum.

In addition to the known sodium 3,7,11,15-tetramethylhexadeca-1,19-diyl sulfate (4), the BuOH extract of the Mediterranean tunicate Sidnyum turbinatum was shown to contain four new metabolites: 1-heptadecanyl sulfate (1), 1-octadecanyl sulfate (2), sodium (2S)-2,6,10,14-tetramethylpentadeca-1,18-diyl sulfate (3), and 1-hexyl sulfate (5). Their structures were determined by spectroscopic and chemical methods. Compounds 1-5 exhibited in vitro antiproliferative activity estimated on the WEHI 164 cell line.

Animals↗
PubMed2000

Human glial cell line-derived neurotrophic factor receptor alpha 4 is the receptor for persephin and is predominantly expressed in normal and malignant thyroid medullary cells.

Glial cell line-derived neurotrophic factor (GDNF) family ligands signal through receptor complex consisting of a glycosylphosphatidylinositol-linked GDNF family receptor (GFR) alpha subunit and the transmembrane receptor tyrosine kinase RET. The inherited cancer syndrome multiple endocrine neoplasia type 2 (MEN2), associated with different mutations in RET, is characterized by medullary thyroid carcinoma. GDNF signals via GFRalpha1, neurturin via GFRalpha2, artemin via GFRalpha3, whereas the mammalian GFRalpha receptor for persephin (PSPN) is unknown. Here we characterize the human GFRalpha4 as the ligand-binding subunit required together with RET for PSPN signaling. Human and mouse GFRalpha4 lack the first Cys-rich domain characteristic of other GFRalpha receptors. Unlabeled PSPN displaces (125)I-PSPN from GFRA4-transfected cells, which express endogenous Ret. PSPN can be specifically cross-linked to mammalian GFRalpha4 and Ret, and is able to promote autophosphorylation of Ret in GFRA4-transfected cells. PSPN, but not other GDNF family ligands, promotes the survival of cultured sympathetic neurons microinjected with GFRA4. We identified different splice forms of human GFRA4 mRNA encoding for two glycosylphosphatidylinositol-linked and one putative soluble isoform that were predominantly expressed in the thyroid gland. Overlapping expression of RET and GFRA4 but not other GFRA mRNAs in normal and malignant thyroid medullary cells suggests that GFRalpha4 may restrict the MEN2 syndrome to these cells.

Animals↗
PubMed2000

Detection of aberrant isotype switch recombination in low-grade and high-grade gastric MALT lymphomas.

Gastric mucosa-associated lymphoid tissue (MALT) lymphoma originates from reactive lymphocytic infiltrates during chronic gastritis, closely associated with Helicobacter pylori infection. MALT lymphomas may be either "low grade" or "high grade," and transformation from low grade to high grade can occur. To obtain information on the maturational state of MALT lymphoma cells, we investigated their ability to undergo isotype switch recombination, which together with immunoglobulin variable gene somatic mutation, contributes to normal B-cell maturation. Using specific probes for the immunoglobulin heavy-chain (IgH) switch regions, we found by Southern blot that 3 out of 5 low-grade cases and 2 out of 2 high-grade cases showed rearrangements within IgH switch regions, which appeared aberrant in 4 of the 5 cases. The cloning of two rearranged fragments from one low-grade and one high-grade case confirmed the aberrant nature of the rearranged fragments. A deletion from the switch mu region (S mu) to the first constant mu exon (C mu 1) and a second deletion from the second constant mu exon (C mu 2) to the gamma 3 region (gamma 3) was detected in the low-grade case. In the high-grade case, there was a deletion of the IgH intronic enhancer (E mu) and a 336-base pair (bp) insertion into the S mu region of a gene (KIAA0307) normally located at 15q24. These data demonstrate for the first time the ability of MALT lymphoma cells to undergo aberrant isotype switch recombinations, which might be directly involved in the development or progression of malignancy.

B-Lymphocytes↗
PubMed2000

Clone-specific PCR reveals wide dissemination of gastric MALT lymphoma to the gastric mucosa.

The development of low-grade gastric mucosa-associated lymphoid tissue (MALT) lymphoma is closely associated with Helicobacter pylori infection. Despite its indolent clinical course and prolonged localization to the site of origin, the lymphoma frequently presents with multifocal lesions. However, the true extent of tumour involvement in the gastric mucosa is unclear, since reactive appearing lymphocytic infiltrates are always present and could contain tumour cells that are not readily identifiable on cytological grounds. Gastrectomy specimens of four MALT lymphoma cases were studied by microdissection and clone-specific polymerase chain reaction (CS-PCR) and of a further case with t(1;14)(p22;q32) by immunohistochemistry for BCL10 protein, which acted as a tumour marker for tumour cells carrying the translocation. CS-PCR revealed that tumour cells were commonly present in histologically non-lymphomatous lymphocytic infiltrates microdissected from areas well separated from tumour lesions. Tumour cells were also frequently found in infiltrates microdissected from the resection margins. These findings were reinforced by direct identification of tumour cells, as recognized by strong BCL10 nuclear staining, in non-lymphomatous lymphocytic infiltrates in the case with t(1;14)(p22;q32). The results show that gastric MALT lymphoma disseminates widely within the gastric mucosa without necessarily forming diagnostic lesions.

Chromosomes, Human, Pair 1↗