Biomedical subjects

A Gambetta

Publications and source records attributed to A Gambetta.

4 recordsLinked to original sources

PubMed2006

Photoinduced transient stark spectroscopy in organic semiconductors: a method for charge mobility determination in the picosecond regime.

Subpicosecond photoinduced Stark spectroscopy experiments are carried out for measuring charge carrier mobility in organic semiconductors. The technique is demonstrated in state-of-art devices based on methanofullerene. The transient mobility of photogenerated charge carriers is measured in the picosecond time domain. Electric field dependent mobility is observed from the earliest time scales. In addition, two distinct transport regimes are revealed: a short-lived state, approximately 10 ps, of high mobility and a transient towards the trap limited transport, associated with the mesoscopic structure of the medium.

Journal Article↗

PubMed2005

Intersubband exciton relaxation dynamics in single-walled carbon nanotubes.

We study exciton (EX) dynamics in single-walled carbon nanotubes (SWNTs) included in polymethylmethacrylate by two-color pump-probe experiments with unprecedented temporal resolution. In the semiconducting SWNTs, we resolve the intersubband energy relaxation from the EX2 to the EX1 transition and find time constants of about 40 fs. The observation of a photoinduced absorption band strictly correlated to the photobleaching of the EX1 transition supports the excitonic model for primary excitations in SWNTs. We also detect in the time domain coherent oscillations due to the radial breathing modes at approximately 250 cm(-1).

Journal Article↗

PubMedDate not supplied

Regulatory relevance of lipoproteins in interleukin-2 stimulated lymphocytes in vitro.

The regulatory role of very low density lipoproteins (VLDL) in de novo protein synthesis and in natural killer (NK) mediated cytotoxicity against cancer cells was evaluated in IL-2 activated peripheral blood mononuclear cells (PBL). Supplementing of VLDL to the incubation medium induced a potent dose-related inhibitory effect on the synthesis and secretion of (35S) labelled proteins. The maximal inhibitory response was observed at 50 micrograms/ml cholesterol VLDL. The effect of VLDL on the IL-2 induced ability of lymphocytes to kill cancer cells and to interfere with target cell proliferation was then evaluated. Maximal cytotoxicity was observed at 50 micrograms VLDL/ml as cholesterol. This VLDL-dependent stimulatory effect was associated with a significant decrease in the proliferative effect of the medium conditioned by PBL. The possibility that VLDL mediate the regulation of immune functions by interacting with metabolic patterns expressed by IL-2 stimulated lymphocytes is discussed in light of these results.

Adult↗

PubMedDate not supplied

Decrease of polyunsaturated fatty acids and elevation of the oleic/stearic acid ratio in plasma and red blood cell lipids of malnourished cancer patients.

The fatty acids profiles of plasma and red blood cell lipids have been evaluated in 12 malnourished cancer patients in comparison with samples from eight healthy controls. In such patients, significantly lower levels of linoleic acid (LA) as percentage of total fatty acids were observed in plasma phospholipids (PL) and cholesterol esters (CE), and in red blood cells PL. The levels of arachidonic acid (AA) and the unsaturation index of the two lipid classes were also reduced in plasma CE but not in PL. In spite of the marked reduction of LA and, more generally, of total polyunsaturated fatty acids (PUFA), no elevation of eicosatrienoic acid (20:3 n-9) was observed, such acid being considered a typical index of essential fatty deficiency. Moreover, no modification of the parameters indicating impairment of the fatty acid desaturation activity was shown. In addition, the levels of palmitic and oleic acids were significantly higher in both plasma PL and CE and in red blood cells PL. The reported elevation of the oleic to stearic acid ratio in lipids of red blood cells from malnourished cancer patients, already observed by other authors, was confirmed in our study. This ratio was even more markedly elevated in plasma lipids of the patients. A very good correlation was found between the reduction of linoleic acid levels, especially in plasma CE, and weight loss, suggesting enhanced utilization of this fatty acid in association with extensive depletion of lipid stores, in this pathological state.

Erythrocytes↗