1,720,969 research outputs found
Nanotechnology and Food: Brief Overview of the Current Scenario
No full textAbstractThe rapidly expanding sector of nanotechnologies has applications in every industrial sector. The production of food of animal origin recognizes several possibilities for technological development through the use of nanomaterials, at animal farming, food processing and product storage levels. Direct use of nanomaterials during these production stages, as well as the uptake from the environment, can lead to the presence of such materials in the final product. In this context analytical methods for the detection and characterization of nanomaterials in complex food matrices and toxicological data are strongly needed to assess the risk for consumers
In vitro and ex vivo photostability studies on Flumethasone and Fluocinolone acetonide
No full textFlumethasone and Fluocinolone acetonide are synthetic corticosteroids used topically for the short-term treatment of various inflammatory skin diseases such as eczema, eye, nose, and ear infections, stomatitis and psoriasis.
As other 11-hydroxy corticosteroids, they have shown to be sensitive to light. Previous studies have demonstrated their reactivity under UV light (UVB>UVA) both in organic and aqueous solvents and their main photoproducts have been isolated and characterized. For this high instability to UV irradiation, these drugs may lose their therapeutic activity. Indeed, their packaging instructions always indicate to protect them from light during storage. Moreover, the same problem may arise when patients are exposed to solar radiation. In order to verify the instability of these molecules when applied on the skin under UV light, the photodegradation of the two drugs is studied both in vitro (aqueous solution and commercial formulation) and in the pig skin; this ex vivo model, very close to the human skin, was used to study the fate of drugs in this organ when exposed to light.
Both the glucocorticosteroids applied on the pig skin showed high photoinstability under UVB irradiation (up to 40 % for Flumethasone and to 30 % for Fluocinolone acetonide, under 10J/cm2 of UVB). The photoproducts formed in the skin were the same found in vitro, except for the hydroperoxide of Fluocinolone. The very high reactivity of this photoproduct towards biological substrates (i.e. proteins and lipids) could be the reason of the lack of its detection
UVB photolysis of betamethasone and its esters: Characterization of photoproducts in solution, in pig skin and in drug formulations
No full textThe stability of the synthetic glucocorticosteroid betamethasone under UVB light was studied both in vitro (water and methanol solution and in topical and injectable commercial formulations) and ex vivo (pig skin). From irradiated methanol solutions three main photoproducts were isolated by HPLC and TLC and characterized by NMR/MS analyses. The modifications involve parts of the molecule peculiar for the therapeutic activity, that is, rearrangement of ring A ("lumi"- and "photolumiderivatives"), and Norrish Type I fragmentation of the ketolic chain ("androderivative"). Two clinically used esters of betamethasone were also studied, namely the 17-valerate and 21-phosphate, and their photoproducts identified. The HPLC method developed for the photolysis studies in solution was also applied to the analysis of commercial formulations. In a cream and a solution for parenteral use, betamethasone highly decomposed under UVB irradiation, even in the presence of the bactericidal agents chlorocresol and phenol, which are able to absorb part of the incoming radiation. As a model for the UV exposed skin to which the drug is applied, ex vivo pig skin was used; not only the yield of photodegradation was evaluated, but the photoproducts were also identified. A test on THP-1 cells demonstrated the loss of anti-inflammatory activity of betamethasone, when modified by UVB light
Photoactivation of corticosteroids in UVB-exposed skin.
No full textThe photodegradation of flumethasone (FM) and fluocinolone acetonide (FC) was studied in solution and in the pig skin. Both glucocorticosteroids applied to the pig skin were unstable under UVB light. The photoproducts formed in the skin were the lumi-, photolumi- and andro-derivatives for FM, the same found in vitro. Instead, FC hydroperoxide formed in solution was not found in the skin: the reactivity and oxidative ability of this photoproduct towards biological substrates (lipids, proteins) seems the reason of the lack of its detection in the ex vivo model. In fact, it demonstrated to quickly oxidize amino acids and peptides, and to react with BSA both in the dark and under irradiation. Moreover, the presence in the irradiated pig skin of the FC andro-derivative, which usually forms in H-donating environment, seems consistent with the mechanism of Norrish I fragmentation followed by H-abstraction, likely from the surrounding biological substrates. These findings indicate that photoreactivity of these compounds may take place in the skin of patients exposing themselves to sunlight and is a warning about possible skin damage as a result of that. Furthermore, photolability of these drugs in the skin might cause loss of their therapeutic activity
In vitro phototoxicity of phenothiazines: Involvement of stable UVA photolysis products formed in aqueous medium
No full textThis paper reports the results of an in vitro evaluation of the phototoxic potential of stable photoproducts formed by UVA photolysis of three phenothiazines, perphenazine, fluphenazine, and thioridazine, in a water environment. Perphenazine gave a single product due to dechlorination. From thioridazine, the two major products formed; the endocyclic sulfoxide and the endocyclic N-oxide in which the 2-SCH3 substituent was replaced by a hydroxy group were tested. From fluphenazine, two products have been examined as follows: an exocyclic N-piperazine oxide and a carboxylic acid arising from hydrolysis of the 2-CF3 group. The phototoxicity of the isolated photoproducts has been studied in order to determine their possible involvement in the photosensitizing effects exhibited by the parent drugs, using hemolysis and 3T3 fibroblasts viability as in vitro assays. As fluphenazine, perphenazine, and thioridazine did, some photoproducts proved phototoxic. In particular, the perphenazine dechlorinated photoproduct and the thioridazine N-oxide were found to exert phototoxic properties similar to the parent compounds. Therefore, our data suggest that some phenothiazine photoproducts may play a role in the mechanism of photosensitivity of these drugs. Because some of these photoproducts correspond to metabolic products of phenothiazines found in humans, it cannot be ruled out that metabolites of phenothiazines can be phototoxic in vivo
Study of the Interactions with UV Light of Non Steroidal Anti-Inflammatory Drugs, the Selective Inhibitors of the Cyclooxygenase-2: Photostability and Photosensitizing Properties in vitro
No full textIn the last years, skin photosensitization is appearing in the most sensitive subjects with a greater number of drugs (Antibiotics, Antifungals, Diuretics and Cardiovascular agents, NSAIDs and Antipsychotics) either applied directly on the skin or administered systemically, and results in the risk of tumors of the skin. It’s likely that other drugs that induce moderate phototoxicity are not recognized as 'photosensitizers' since the induced cutaneous reactions are taken for mild sunburn or solar eczemas. The selective inhibitors of the cyclooxygenase-2 (CSIs), drugs entered recently the market, are here studied in terms of phototoxicity and photostability, since their chemical structure suggests their interactions with UV light. This reactivity could bring to changes of the molecule or to its activation, with induction of photosensitizing effects. Indeed, for the less recent Nimesulide, some phototoxic reactions have already been reported in humans. In fact, CSIs drugs are characterized by the presence of an aromatic structure with high degree of conjugation, of a sulphonamide moiety (similar to that of the Sulphonamides, the phototoxicity of which has been already demonstrated) and, in some of them, of a trifluoromethyl group highly unstable under irradiation (as in the case of Fluphenazine). The present study includes investigations on the photostability of PTPBS (4-[5-phenyl-3-(trifluoromethyl)-1H-pyrazol-1-yl]benzenesulfonamide), and the evaluation of its phototoxic potential in vitro on cellular models and on isolated biomolecules
Betamethasone phototoxicity: in vitro, in vivo and ex vivo studies
No full textBetamethasone is a synthetic glucocorticosteroid present in numerous systemic and topical commercial formulations for the treatment of rheumatic diseases and skin disorders. The drug is highly unstable under UV light (UVB > UVA) and it has demonstrated moderate photosensitizing activity in patients exposed to solar radiation. Since this drug is taken to treat cutaneous diseases, it’s likely that its induced photosensitization reactions are not always recognized as they are taken for mild sunburn or solar eczemas as well. Three methods (in vitro, in vivo and ex vivo) were used to test drug phototoxicity. The in vitro phototoxicity was determined by exposing Balb/c 3T3 fibroblasts to UVB radiation in the presence of 100 μM drug. The results showed that dark incubation and low UVB dose (0.4 J/cm2) did not affect cell viability. On the contrary, upon exposure to this low UVB dose, Betamethasone was able to induce a decrease of cell viability (30%).
In vivo phototoxicity was assayed by means of skin erythema induction in albino guinea pig skin. The drug (200 g) induced skin erythema both when applied as a methanol solution (+/--) and as a commercial formulation (cream containing 0.1% Betamethasone) (++/-).
An ex vivo model, epidermis and dermis from isolated pig skin, was also employed. By working both with intact skin and with isolated epidermal cells, it has been possible to determine the extent of intact drug recovery and the cell viability after drug phototreatment.
The three methods used gave comparable results and therefore in vitro and ex vivo tests may be an alternative to in vivo phototoxicity studies.
From our results, Betamethasone can be considered a photosensitizing drug
Roman Opalka: the research to infinity
Full text linkopenL’argomento presentato all’interno di questa tesi è basato sull’operato e sulla vita di Roman Opalka, un noto artista di origini polacche, nato nel 1931 in Francia, nella Somme. Attraverso un analisi attenta ed accurata ci si sofferma non solo sulla vita dell'artista, ma anche sul dilemma dietro alla rappresentazione del tempo e dell'infinito, che l'ha turbato fin dall'infanzia. Per capire la poetica dell’artista sono state prese in considerazione le opere letterarie, le ricerche matematico-scientifiche alle quali Opalka ha fatto riferimento per definire la sua ricerca artistica. Di fondamentale importanza sono stati i cataloghi delle mostre collettive a cui ha partecipato e le testimonianze della seconda moglie Marie Madleine Gazeau. All’interno dell’elaborato, nel definire il concetto di tempo, non viene fatto riferimento solo all’arte ma anche ad altri rami del sapere quali la matematica, la scienza e la filosofia. Questa apertura è volta a definire il concetto di infinito temporale e come questo viene teorizzato dai vari scienziati e pensatori. Nel primo capitolo viene proposta una breve biografia dell’artista. Mentre il secondo capitolo è dedicato alla visione della temporalità e dell’infinito nell’arte, ripercorsa attraverso le teorie e le opere di alcuni tra i più grandi matematici quali Cartesio e Albert Einstein e di grandi artisti come Leonardo Da Vinci e Marina Abramovic. Si indaga sull’origine del tempo e sulla rappresentazione antica e odierna e i differenti mezzi utilizzati per poterne esprimere l’essenza, anche attraverso il suono. Per quanto riguarda l’infinito si parte con le prime definizioni etimologiche utilizzate dagli antichi, partendo da Anassimandro soffermandosi poi nel corso della ricerca sulla dimensione teologica e artistica della rappresentazione. Infine l’ultima parte dell’elaborato è riservata alla mostra In-finitum, tenutasi nel 2009 a Venezia, dove vennero esposte anche opere di Oplaka. L’esposizione risulta di fondamentale importanza per carpire l’essenza di ricerche artistiche dedicate al tema dell’infinito, antecedenti e coeve, opposte o affini all’ideologia di Opalka.The argument presented within this thesis is based on the work and life of Roman Opalka, a well-known artist of Polish origin, born in 1931 in France, in the Somme. Through careful and accurate analysis, we focus not only on the artist's life but also on the dilemma behind the representation of time and infinity, which has troubled him since childhood. To understand the artist's poetics, I took into consideration the literary works, the mathematical-scientific researches to which Opalka referred to define his artistic research. Of fundamental importance were the catalogs of the group exhibitions in which he participated and the testimonies of his second wife Marie Madleine Gazeau. Within the paper, in defining the concept of time, reference is made not only to art but also to other branches of knowledge such as mathematics, science, and philosophy. This opening is aimed at defining the concept of temporal infinity and how this is theorized by various scientists and thinkers. In the first chapter, a short biography of the artist is proposed. While the second chapter is dedicated to the vision of temporality and infinity in art, retraced through the theories and works of some of the greatest mathematicians such as Descartes and Albert Einstein and great artists such as Leonardo Da Vinci and Marina Abramovic. It investigates the origin of time and the ancient and present representation and the different means used to be able to express its essence, also through sound. As for the infinite, we start with the first etymological definitions used by the ancients, starting with Anaximander and then dwelling in the course of research on the theological and artistic dimension of representation. Finally, the last part of the work is reserved for the In-finitum exhibition, held in 2009 in Venice, where works by Oplaka were also exhibited. The exhibition is of fundamental importance for grasping the essence of artistic research dedicated to the theme of infinity, antecedent and contemporary, opposite or similar to the ideology of Opalka
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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