204 research outputs found
CALORIMETRIA DIFFERENZIALE A SCANSIONE DI MISCELE FOSFOLIPIDICHE DA MEMBRANE DI GLOBULI ROSSI
No full textNegli ultimi anni particolare attenzione è stata posta alle relazioni tra funzione delle membrane, le loro proprietà chimico-fisiche e la composizione in acidi grassi, prevalentemente della frazione fosfolipidica considerato il fatto che fosfolipidi, trovati nelle membrane biologiche, derivano le loro proprietà idrofobiche dagli acidi grassi costituenti.
Le correlazioni più frequentemente analizzate sono quelle tra componenti di membrana e i loro acidi grassi modificati, in vivo, da alterazioni della composizione lipidica della dieta o, in vitro, mediante opportune modifiche del mezzo di coltura.
Somministrando diete diverse a bovine da latte abbiamo creato una “banca” di campioni di membrane di globuli rossi a diversa composizione lipidica (1, 2).
Scopi di questo studio sono stati: 1) l’analisi della composizione delle miscele di fosfolipidi estratti dalle membrane, 2) la valutazione delle correlazioni tra composizione e proprietà termotropiche delle miscele.
I lipidi totali sono stati estratti dagli eritrociti bovini con miscele di cloroformio/metanolo in diversi rapporti e le miscele lipidiche sono state frazionate mediante cromatografia su colonna.
Le singole specie fosfolipidiche sono state separate in HPTLC e quantificate mediante densitometria a scansione.
La composizione in acidi grassi dei fosfolipidi di membrana è stata valutata mediante gas-liquido cromatografia e dispersioni acquose tamponate sono state esaminate mediante calorimetria differenziale a scansione.
Per ogni campione è stato calcolato il contenuto di acidi grassi saturi (S), insaturi (U) e l’indice di insaturazione (UI).
I principali acidi grassi presenti (mediamente ≥ 10% in peso) sono risultati: C16:0, C18:0, C18:1, C18:2 e C24:0.
Le miscele di fosfolipi mostrano una o due transizioni di fase a temperature comprese tra 17.7 e 40.0 °C. La prima temperatura di transizione è compresa tra 17.7 e 26.0 °C.
UI e U/S non risultano essere correlati al contenuto percentuale delle diverse specie molecolari di fosfolipidi (PC, PE, SM, PS+PI) e di PC+SM, costituenti principali del foglietto esterno del doppio strato lipidico.
Esiste, invece, una correlazione lineare tra la prima temperatura di transizione ed UI (P < 0.05) e U/S (P < 0.01). La prima temperatura di transizione diminuisce all’aumentare di UI o del rapporto U/S.
References
1. G. Monticelli, S. Rapelli, G. Montorfano, P. Magistretti and B. Berra- “Red blood cell membrane composition following diet manipulation in the cow” Riv. Ital. Sostanze Grasse 67: 507-515 (1990)
2. G. Monticelli, M. Masserini,G. Lercker, T. Beringhelli, P. Marciani, E. Calappi and B. Berra – “Red blood cell membrane composition following diet manipulation in the cow. II: phospholipid fatty acid distribution and physico-chemical characteristics of membrane and its constituents” Riv. Ital. Sostanze Grasse 69: 189-199 (1992
Does joining social media groups help to reduce students’ dropout within the first university year?
No full textUsing observational data, the aim of our study paper was to investigate whether university students’ dropout within the first year is influenced by participation in social media groups such as Facebook pages created and run by other students. Specifically, in this paper such participation is considered as a treatment and represents a means to help promote and strengthen social relationships amongst students but also to help share information on courses and other material useful for studying and preparing for exams. For this purpose, data from a sample survey of students enrolled in a major Italian university were used. Given a non-random treatment assignment, analysis was carried out using propensity score matching (PSM) in order to correct for selection bias due to a set of observable pretreatment covariates. Several matching techniques and sensitivity analyses suggested that the results were robust for estimating an average treatment effect on the treated group. The estimated effect indicated that participation in social media groups is effective for lowering the dropout rate
Change of ganglioside accessibility at the plasma membrane surface of cultured neurons, following Protein Kinase C activation
No full textWhile the mechanism of signal transduction across the plasma membrane from the exo- to the endoplasmic side has been extensively investigated, the possible return of messages back to the outer layer is less known. We studied the effect of protein kinase C activation on the ganglioside accessibility at the exoplasmic face of intact rat cerebellar granule cells in culture, using the enzyme sialidase as the probing molecule. Under the experimental conditions (1 milliunit/mL enzyme, 2 min incubation at 37 degrees C), only GT1b and GD1a gangliosides were partially affected by the enzyme (28.6 and 25.7% hydrolysis, respectively). After cell treatment with phorbol 12-myristate 13-acetate, inducing protein kinase C activation, GT1b and GD1a ganglioside susceptibility to sialidase was strongly decreased (8.6 and 15.9% hydrolysis, respectively). A reduction of ganglioside hydrolysis was also observed when protein kinase C activation was induced by cell treatment for 15 min with 100 mu M glutamate. On the contrary, accessibility did not vary when protein kinase C translocation was not effective (either in the absence of Ca2+ in the medium or using 1 mu M glutamate) or when the kinase activity was inhibited by staurosporine. These data suggest that following PKC activation, a key step of inbound transmembrane signaling, cell may dispatch outbound messages to the plasma membrane outer layer, changing the selective recognition and crypticity of glycolipids at the cell surface, possibly through a modulation of their segregation state
Is Generation Z more Inclined than Generation Y to Purchase Sustainable Clothing?
No full textIncreasing clothing (over)consumption, supported by the fast fashion industry, has caused a significant reduction in clothing costs, raised major sustainability challenges, and highlighted the need for engaging in more sustainable consumption behaviour to mitigate the negative environmental, social, and economic consequences. Although green purchase behaviour is now well understood, extant literature still lacks a comprehensive approach to explain consumers behaviour (especially that of the younger generations) with respect to sustainable clothing. Using survey data collected through a structured questionnaire, this study aims to assess whether Generation Z is more inclined to buy sustainable or eco-friendly clothing than Generation Y. Given the non-random selection of respondents, analysis was conducted using propensity score matching to correct for potential bias based on a set of observable confounders. The results show that Generation Z is more likely to buy second-hand clothing, whereas Generation Y is more interested in clothes made of organic and eco-sustainable fabrics
A finite mixture regression model for evaluating University admission test and students’ careers
No full textThe evaluation of the initial preparation of students wishing to enroll in a
degree program is an important issue since students are required to take an admission
test before enrolling in a degree program. In this paper we aim at investigating the
effect of the University admission test on the students’ careers at the end of the first
academic year, also detecting, if they exist, unobserved but meaningful subgroups of
students with similar progression in their university careers. The analysis is referred to
the participants to the admission test carried out in September 2011 at the Department
of Economics and Management, University of Pisa. Data were analysed using a finite
mixture regerssion model in order to investigate population heterogeneity
Effect of ethanol amine plasmalogens on Fe-induced peroxidation of arachidonic acid in dipalmitoylphosphatidylcholine vesicles
No full textWe have investigated the influence of ethanolamine plasmalogens on iron-induced oxidation of arachidonic acid in dipalmitoylphosphatidylcholine (DPPC) vesicles. Lipoperoxidation was induced by the addition of 50 muM FeSO4 and studied above (50 degreesC) and below (15 degreesC) the gel-to liquid transition temperature of the vesicles, at two different pH values (7.4 or 6.4). The extent of peroxidation was measured as thiobarbituric reactive product formed and the influence exerted by ethanolamine plasmalogens (PEPL) in this process was compared to that of dipalmitoylphosphatidylethanolamine (DPPE) and diacylphosphatidylethanolamines (DAPE). The extent of peroxidation of arachidonic acid embedded in DPPC vesicles was similar at the two temperatures and greater at 50 degreesC under acidic conditions. However, the peroxidative process was significantly decreased at 50 degreesC in the presence of PEPL, but not of DPPE or DAPE and the inhibitory effect was enhanced at pH 6.4. The possibility that a different phase distribution of the phospholipids, namely a transition from a lamellar to a hexagonal phase, may play a role in the scavenger effect of ethanolamine plasmalogens is discussed
The thermotropic behaviour of red blood cell membrane phospholipids
No full textPhospholipids are the major constituents of biological membranes and the lipid structural organization is important to membrane function. In this study we have examined, by differential scanning calorimetry (DSC), the thermal behaviour of phospholipids extracted from bovine red blood cell membrane and related the observed characteristics to the phospholipid classes in the mixture. Phospholípíd classes were separated by thin layer chromatography. DSC was performed on aqueous buffer dispersions (pH 7.4) approx. 3 mM. For all phospholipid samples at least one, or sometimes two transitions were observed. The calorimetric scans show the presence of a broad transition between 0 and 30 °C (midpoint of the transition at 24.1 - 24.5 °C) whereas the second phase transition occurs at a transition temperature of 32.4 - 38.1 °C. The analyzed membranes contained the same amounts of phosphatidylcholine (PC; 6 - 9 % w/w of total phospholipids) and phosphatidylethanolamine (PE; 24 – 32 %) but different percentual contents of sphingomyelin (SM; 16 – 31 %), which contributes to rigidification, and phosphatidylserine + phosphatidylinositol (PS + PI; 30 – 44 %) which may be considered as fluidizers, similar to lecithin. In all the analyzed samples practically identical temperatures at the first phase transition were obtained. The second phase transition, when occurring, was at very different temperatures. No direct correlation has been found between this second phase transition and the SM/PC ratio also if variations of this ratio in artificial bilayers and biological membranes have a pronounced effect on the system properties. The second phase transition appeared in samples characterized by an high value of the (PS + PI)/PC ratio (> 5.4) and the transition temperature increased with the value of this ratio. Further investigations seem to be necessary to consider the importance of the fatty acid composition of the studied mixtures on the thermotropic behaviour
A Longitudinal Analysis of Riskiness Indicators After the 2008 and 2011 Economic Crises: The Case of Italian Manufacturing
No full textThe Great Recession derived from USA subprime crisis involved the European countries in two different steps: in the first phase, referred to 2008–2009, the finance contraction and the bank failures spread out across the whole Atlantic area involving, above all, the financial market but also influencing the real economy. The second phase, started in 2011 and lasted until 2014–2015, affected the Euro zone and sovereign debts of the countries until 2015 in depth. Also for Italy, the crisis period was characterized by a deep negative conjuncture until 2009, by a slight recovery until the first half of 2011 and by an intense recession from 2011 to 2015. The aim of this work is to collect evidence on the Italian manufacturing system with the following goals: to investigate the riskiness–distress risk trend across industries in 2008–2017 period and to understand how this trend inluences the performance of the company at the end of the period. To perform this analysis a Latent Growth Curve Model is proposed, using an important Italian private database containing the book-value data of the joint-stock company Italian firms
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