University of Siena

About: University of Siena is a education organization based out in Siena, Italy. It is known for research contribution in the topics: Population & Cancer. The organization has 12179 authors who have published 33334 publications receiving 1008287 citations. The organization is also known as: Università degli studi di Siena & Universita degli studi di Siena.

Corneal crosslinking: riboflavin concentration in corneal stroma exposed with and without epithelium.

Abstract: Purpose To evaluate intrastromal concentrations of riboflavin with and without epithelium to ensure the efficacy and safety of corneal crosslinking (CXL) by the standard and transepithelial procedures. Setting Department of Ophthalmology and Department of Pharmacology G. Segre, Siena University, Siena, Italy. Methods This study comprised keratoconic patients enrolled for penetrating keratoplasty (PKP) and warm-stored sclerocorneal rings unsuitable for transplantation. Half the PKP specimens were debrided, and half were left with the epithelium in situ. One of the latter and 1 debrided sample were not exposed to riboflavin (controls). Samples in both groups were soaked with 0.1% riboflavin–dextran 20% solution instilled every 2 minutes for 5, 15, and 30 minutes. Riboflavin concentrations were determined by high-performance liquid chromatography (HPLC). Results The study evaluated 14 PKP specimens and 16 sclerocorneal rings. Control samples did not show a riboflavin emission peak. In exposed samples with epithelium, the mean riboflavin concentration was 91.88 ng/g after 5 minutes of exposure, 95.60 ng/g after 15 minutes, and 94.92 ng/g after 30 minutes. In the debrided samples, the mean riboflavin concentration was 14.42 μg/g, 20.92 μg/g, and 24.06 μg/g, respectively. No differences were seen between the in vivo samples and the ex vivo samples. Conclusions The HPLC quantitative study showed that stromal concentrations of riboflavin increased with exposure time only if the epithelium was removed. A theoretically safe and effective riboflavin concentration of 15 μg/g was obtained for ultraviolet A-induced CXL only after the epithelium was removed and after at least 10 minutes of riboflavin application every 2 minutes.

Tourism's Impact on Long-Run Mexican Economic Growth

Abstract: Tourism is one of the most important factors in the productivity of the Mexican economy with significant multiplier effects on economic activity. This paper investigates possible causal relationships between tourism expenditure, real exchange rate and economic growth by using quarterly data. Johansen co-integration analysis shows the existence of one cointegrated vector among real GDP, tourism expenditure, and real exchange rate where the corresponding elasticities are positive. The tourism-led growth hypothesis is confirmed through cointegration and causality testing. Expenditure is weakly exogenous to real GDP producing a more than proportional effect in growth (it means real GDP increases 60% more when expenditure in tourism is increased). Short-run Granger causality shows that causality goes from expenditure to GDP, and there is a bidirectional short-run causality between real exchange rate and real GDP. Impulse response analysis shows that a shock in expenditure produce a continuous positive effect on growth while a shock in real exchange rate produces first a negative effect and then a positive one.

Leptin signaling in breast cancer: An overview

Abstract: The adipocyte-derived peptide leptin acts through binding to specific membrane receptors, of which six isoforms (obRa-f) have been identified up to now. Binding of leptin to its receptor induces activation of different signaling pathways, including the JAK/STAT, MAPK, IRS1, and SOCS3 signaling pathways. Since the circulating levels of leptin are elevated in obese individuals, and excess body weight has been shown to increase breast cancer risk in postmenopausal women, several studies addressed the role of leptin in breast cancer. Expression of leptin and its receptors has been demonstrated to occur in breast cancer cell lines and in human primary breast carcinoma. Leptin is able to induce the growth of breast cancer cells through activation of the Jak/STAT3, ERK1/2, and/or PI3K pathways, and can mediate angiogenesis by inducing the expression of vascular endothelial growth factor (VEGF). In addition, leptin induces transactivation of ErbB-2, and interacts in triple negative breast cancer cells with insulin like growth factor-1 (IGF-1) to transactivate the epidermal growth factor receptor (EGFR), thus promoting invasion and migration. Leptin can also affect the growth of estrogen receptor (ER)-positive breast cancer cells, by stimulating aromatase expression and thereby increasing estrogen levels through the aromatization of androgens, and by inducing MAPK-dependent activation of ER. Taken together, these findings suggest that the leptin system might play an important role in breast cancer pathogenesis and progression, and that it might represent a novel target for therapeutic intervention in breast cancer.

Role of p53 in the Regulation of Cellular Senescence

Abstract: The p53 transcription factor plays a critical role in cellular responses to stress. Its activation in response to DNA damage leads to cell growth arrest, allowing for DNA repair, or directs cellular senescence or apoptosis, thereby maintaining genome integrity. Senescence is a permanent cell-cycle arrest that has a crucial role in aging, and it also represents a robust physiological antitumor response, which counteracts oncogenic insults. In addition, senescent cells can also negatively impact the surrounding tissue microenvironment and the neighboring cells by secreting pro-inflammatory cytokines, ultimately triggering tissue dysfunction and/or unfavorable outcomes. This review focuses on the characteristics of senescence and on the recent advances in the contribution of p53 to cellular senescence. Moreover, we also discuss the p53-mediated regulation of several pathophysiological microenvironments that could be associated with senescence and its development.