Biomedical subjects

Francesca Ferri

Publications and source records attributed to Francesca Ferri.

5 recordsLinked to original sources

PubMed2006

Methane drizzle on Titan.

Saturn's moon Titan shows landscapes with fluvial features suggestive of hydrology based on liquid methane. Recent efforts in understanding Titan's methane hydrological cycle have focused on occasional cloud outbursts near the south pole or cloud streaks at southern mid-latitudes and the mechanisms of their formation. It is not known, however, if the clouds produce rain or if there are also non-convective clouds, as predicted by several models. Here we show that the in situ data on the methane concentration and temperature profile in Titan's troposphere point to the presence of layered optically thin stratiform clouds. The data indicate an upper methane ice cloud and a lower, barely visible, liquid methane-nitrogen cloud, with a gap in between. The lower, liquid, cloud produces drizzle that reaches the surface. These non-convective methane clouds are quasi-permanent features supported by the global atmospheric circulation, indicating that methane precipitation occurs wherever there is slow upward motion. This drizzle is a persistent component of Titan's methane hydrological cycle and, by wetting the surface on a global scale, plays an active role in the surface geology of Titan.

Journal Article↗

PubMed2006

Early effects of topoisomerase I inhibition on RNA polymerase II along transcribed genes in human cells.

We have determined the early effects of camptothecin and alpha-amanitin on genomic DNA-binding sites of RNA polymerase II (RNAPII), TATA-binding protein (TBP), DNA topoisomerase I (Top1), and histone components in human transcribed loci by chromatin-immunoprecipitation (ChIP). The two agents caused notably different alterations in active chromatin. Camptothecin induced a specific reduction of RNAPII density at promoter pause sites and histone modifications suggesting an increased chromatin accessibility. alpha-Amanitin caused an accumulation of RNAPII at transcribed genes, a reduction of TBP bound to chromatin and a less accessible chromatin structure. Interestingly, RNAPII reduction at promoter pause sites occurred within 5-10min of camptothecin treatment, and was not a response to replication-dependent DNA breaks. ChIP analyses of RNAPII along transcribed genes indicated that RNAPII levels were transiently increased at internal exons, and that camptothecin effects could be fully reversed by DRB, a cdk inhibitor. Top1 was found to be enriched in active chromatin, therefore suggesting that Top1 inhibition at the transcribed template and/or adjacent regulating regions immediately affects RNAPII at active genes. The findings are novel in vivo evidence of camptothecin effects on RNAPII bound to transcribing genomic regions, and are consistent with the hypothesis that Top1 activity can be involved in transcription regulation at the level of promoter clearance.

Amanitins↗

PubMed2006

Approaches to semi-synthetic minimal cells: a review.

Following is a synthetic review on the minimal living cell, defined as an artificial or a semi-artificial cell having the minimal and sufficient number of components to be considered alive. We describe concepts and experiments based on these constructions, and we point out that an operational definition of minimal cell does not define a single species, but rather a broad family of interrelated cell-like structures. The relevance of these researches, considering that the minimal cell should also correspond to the early simple cell in the origin of life and early evolution, is also explained. In addition, we present detailed data in relation to minimal genome, with observations cited by several authors who agree on setting the theoretical full-fledged minimal genome to a figure between 200 and 300 genes. However, further theoretical assumptions may significantly reduce this number (i.e. by eliminating ribosomal proteins and by limiting DNA and RNA polymerases to only a few, less specific molecular species). Generally, the experimental approach to minimal cells consists in utilizing liposomes as cell models and in filling them with genes/enzymes corresponding to minimal cellular functions. To date, a few research groups have successfully induced the expression of single proteins, such as the green fluorescence protein, inside liposomes. Here, different approaches are described and compared. Present constructs are still rather far from the minimal cell, and experimental as well as theoretical difficulties opposing further reduction of complexity are discussed. While most of these minimal cell constructions may represent relatively poor imitations of a modern full-fledged cell, further studies will begin precisely from these constructs. In conclusion, we give a brief outline of the next possible steps on the road map to the minimal cell.

Animals↗

PubMed2006

Lidocaine pretreatment for the prevention of propofol-induced transient motor disturbances in children during anesthesia induction: a randomized controlled trial in children undergoing invasive hematologic procedures.

BACKGROUND: We examined the effect of lidocaine pretreatment before propofol administration on the incidence of transient motor disturbances and on propofol requirements for anesthesia induction in infants and children undergoing repeated painful diagnostic and therapeutic hematological procedures. METHODS: A series of 358 children subgrouped according to the presence of a peripheral-vein or central venous catheter were randomly assigned to receive an intravenous dose of 2% lidocaine (2.0 mg.kg(-1)) or an equivalent volume of saline, 1 min before propofol (1.5-3.5 mg.kg(-1)) injected for anesthesia induction. RESULTS: The incidence of spontaneous movements was significantly lower in patients pretreated with lidocaine than in those receiving placebo (2.5% vs 29%; P < 0.001, by chi-square test), as was the propofol induction dose (1.6 +/- 0.2 mg.kg(-1) vs 2.2 +/- 0.3 mg.kg(-1); P < 0.001) and pain at the injection site in patients peripheral-vein catheter (12% vs. 54%; P < 0.001). Lidocaine administration also improved children's acceptance as reported by parents on the Observational Scale of Behavioral Distress administered 2 h after the procedure (6.5 +/- 2.5 vs. 9.4 +/- 3.3; P < 0.001). Bouts of coughing developed significantly more frequently after lidocaine pretreatment than after placebo (62.5% vs. 17.5%; P < 0.001). CONCLUSIONS: Because lidocaine pretreatment before the induction of propofol-based anesthesia decreases propofol-induced motor disturbances, lowers hypnotic requirements and reduces pain at the injection site, without inducing untoward events, thus improving children's and parental acceptance, it should become standard practice in infants and children undergoing repeated painful diagnostic and therapeutic hematological procedures.

Analysis of Variance↗

PubMed2005

A soft solid surface on Titan as revealed by the Huygens Surface Science Package.

The surface of Saturn's largest satellite--Titan--is largely obscured by an optically thick atmospheric haze, and so its nature has been the subject of considerable speculation and discussion. The Huygens probe entered Titan's atmosphere on 14 January 2005 and descended to the surface using a parachute system. Here we report measurements made just above and on the surface of Titan by the Huygens Surface Science Package. Acoustic sounding over the last 90 m above the surface reveals a relatively smooth, but not completely flat, surface surrounding the landing site. Penetrometry and accelerometry measurements during the probe impact event reveal that the surface was neither hard (like solid ice) nor very compressible (like a blanket of fluffy aerosol); rather, the Huygens probe landed on a relatively soft solid surface whose properties are analogous to wet clay, lightly packed snow and wet or dry sand. The probe settled gradually by a few millimetres after landing.

Journal Article↗