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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
Acidi grassi omega-3 : nutrienti, alimenti funzionali, farmaci?
No full textThe mechanisms through which ω-3 ed ω-6 fatty acids influence man's health have been thoroughly investigated over the last years and their importance in man's diet is known. The author compares the palaeolithic diet with our current diet, with special reference to the absorption of nutrients and fatty acids. He also emphasizes the positive physio-metabolic effects of the ω-3 fatty acids. Thus, our current dietary models need a ω-3 integration and/or a further supply of such acids to other foods which become "functional" products
Glycemic index, glycemic load: new evidence for a link with acne
Full text linkIn this paper, the link between high glycemic index and load will be reviewed. The data from the literature discussed relate to a short presentation of the physiopathology of acne, including the influence of hyperinsulinemia as a key factor at the beginning of acne
Glycemic index, glycemic load, wellness and beauty : the state of the art
No full textIn this paper, the link between high glycemic index and load will be reviewed. The data from the literature discussed relate to a short presentation of the physiopathology of acne, including the influence of hyperinsulinemia as a key factor at the beginning of acn
GM3 content modulates the EGF-activated p185c-neu levels, but not those of the constitutively activated oncoprotein p185neu
No full textThe functional relationship between ganglioside GM(3) and two tyrosine-kinase receptors, the normal protein p185(c-neu) and the mutant oncogenic protein p185(neu), was examined in HC11 cells and in MG1361 cells, respectively. In the former, p185(c-neu) expression and activation are controlled by EGF addition to the culture medium and by epidermal growth factor receptor (EGFR) activity, whereas the latter express unchangingly high levels of constitutively activated p185(neu). Studies were carried out using (+/-)-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol hydrochloride ([D]-PDMP), which inhibits ganglioside biosynthesis resulting in ganglioside depletion, and addition of exogenous GM(3) to the culture medium. In HC11 cells treated with only [D]-PDMP, p185(c-neu) levels remain similar to control cells, whereas levels of tyrosine-phosphorylated p185(c-neu) increase after treatment with [D]-PDMP in combination with EGF. When exogenous GM(3) is added in combination with [D]-PDMP and EGF, the enhanced phosphorylated-p185(c-neu) returns to control levels. Interestingly, EGFR levels also vary and, analogously to phosphorylated-p185(c-neu), the increase of EGFR content consequent to the [D]-PDMP and EGF addition is reversed by exogenous GM(3). In contrast, the addition of neither [D]-PDMP nor exogenous GM(3) modifies expression and tyrosine-phosphorylation levels of p185(neu) in MG1361 cells. These findings indicate that changes in GM(3) content modulate the tyrosine-phosphorylated p185(c-neu) levels in a reversible manner, but this is not specific for p185(c-neu) because EGFR levels are also modified. Furthermore, these data suggest that GM(3) may play a functional role by affecting the internalisation pathway of p185(c-neu)/EGFR heterodimers, but not of p185(neu) homodimers
Differential scanning calorimetry of erythrocyte reconstituted membrane
No full textThe thermal properties of biomembranes examined by dífferential calorimetry mimic the properties of bílayers formed from their isolated lipids or from synthetic lipids. In this study we have analyzed, by differential scanning calorimetry (DSC), the thermal behaviour of lipids extracted from bovine erythrocyte and of their reconstítuted mixtures. Membrane lipids were extracted from blood samples of 11 cows and separated in the three components: cholesterol, phospholipids and glycolipids. Phospholipid and glycolipid classes were determined by thin layer chromatography. Lipids from erythrocyte membrane of different animals (at controlled diet), at a given time, were pooled together at a proportional amount like in the original membranes. DSC was performed on aqueous buffer dispersions (pH 7.4) of the average lipid components but, ín some cases, the sample contained lipids ísolated from one animal. Average phospholipid sample exhibited two phase transitions: the first at 24 - 26 °C and the second at about 38 °C. Some scans of phospholípids from one animal show only the first transítíon which occurs between 23.1 and 25.4 °C whereas the second phase transition, when occurring, is at very different temperatures (32.4 - 38.1 °C). For all average glycolipid samples one transition was observed at about 35 °C. Mixtures of cholesterol and phospholipids show only one broad transition. In these míxtures the transition temperature is close to that of the second transition of phospholipid samples.
Some correlations between the transition temperatures and the amounts of different phospholipids in the samples have been tested but it seems important to consider the fatty acid composition of the studied míxtures to account for the different levels of saturated and unsaturated fatty acids
Effects of ganglioside biosynthesis inhibition on the expression and phosphorylation of the membrane tyrosine-kinase receptors p185neu/ErbB2 in tumor and normal mammary cell lines
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