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.

Guided tissue regeneration versus mucogingival surgery in the treatment of human buccal gingival recession.

Abstract: A surgical technique involving membranes was used to treat localized human buccal recessions 3 mm to 8 mm. The results on 25 patients (test group) were evaluated 18 months postoperatively and compared with the results obtained in 25 other patients (control group) having undergone mucogingival surgery. In the test group, a trapezoidal flap with a large base was raised beyond the mucogingival junction. The exposed root surface was scaled thoroughly to a concave shape. A membrane was bent and adapted onto the concave root surface. The flap was sutured far coronally and the membrane removed one month later. The control patients underwent a 2-step procedure, consisting of a free gingival graft and a coronally positioned flap. The amount of root coverage obtained was similar in the 2 groups (test = 72.73%; control = 70.87%), although the clinical attachment gain (test = 5.12 mm; control = 3.56 mm) and pocket variation (test = 1 mm reduction; control = 0.06 mm increase) differed significantly (P < 0.001). The keratinized tissue width was greater in the control group. The regression analysis showed that the amount of covered root surface after treatment was in strict correlation with the depth of the original recession in the test group, while no correlation was found in the control group. The expected root coverage was greater in the test group when the recession was greater than 4.98 mm, while it was greater in the control group when the recession was less than 4.98 mm. These results indicate that a guided tissue regeneration procedure can be used to successfully treat recession. The membrane procedure compared favorably with the mucogingival surgery in the treatment of deep recession.

Clinical behavior of translucent-fiber posts: a 2-year prospective study.

Abstract: Purpose This study prospectively evaluated the clinical performance of three types of translucent posts over a follow-up period of between 2 and 3 years. Materials and methods Selected were 225 patients with one premolar in need of endodontic treatment, followed by restoration with a fiber post and porcelain crown. The sample was randomly divided into three groups of 75 patients each. The same type of post was used in all patients within a group: group 1 = Aesthetic Plus; group 2 = DT; and group 3 = FRC Postec. For bonding the post, a light-curing adhesive (One-Step) and a dual-curing resin cement (Duo-Link) were applied in group 1 and 2 roots, whereas self-curing materials (Excite DSC as adhesive and MultiLink as resin cement) were used in group 3. After 6, 12, and 24 months, patients were recalled, and a clinical and radiographic examination was performed. For some patients, 30-month follow-up data were also collected. Results Debonding of the post occurrred in eight cases (3.5%); in another six cases, a recurrence of the periapical lesion was reported. Conclusion The statistical analysis did not reveal any significant difference in the survival rate of the tested posts, suggesting that all are equally and sufficiently reliable for clinical use.

Burden-driven feedback control of gene expression

Abstract: In this CRISPR-based feedback control system, sgRNA expression is triggered by the burden of protein overexpression, and the sgRNA directs repression of the exogenous gene promoter to reduce burdensome expression and restore growth of the cell. Cells use feedback regulation to ensure robust growth despite fluctuating demands for resources and differing environmental conditions. However, the expression of foreign proteins from engineered constructs is an unnatural burden that cells are not adapted for. Here we combined RNA-seq with an in vivo assay to identify the major transcriptional changes that occur in Escherichia coli when inducible synthetic constructs are expressed. We observed that native promoters related to the heat-shock response activated expression rapidly in response to synthetic expression, regardless of the construct. Using these promoters, we built a dCas9-based feedback-regulation system that automatically adjusts the expression of a synthetic construct in response to burden. Cells equipped with this general-use controller maintained their capacity for native gene expression to ensure robust growth and thus outperformed unregulated cells in terms of protein yield in batch production. This engineered feedback is to our knowledge the first example of a universal, burden-based biomolecular control system and is modular, tunable and portable.

Ultrastructure of the cytoskeleton in freeze-substituted pollen tubes ofNicotiana alata

Abstract: The ultrastructure of the cytoskeleton inNicotiana alata pollen tubes grownin vitro has been examined after rapid freeze fixation and freeze substitution (RF-FS). Whereas cytoplasmic microtubules (MTs) and especially microfilaments (MFs) are infrequently observed after conventional chemical fixation, they occur in all samples prepared by RF-FS. Cortical MTs are oriented parallel to the long axis of the pollen tube and usually appear evenly spaced around the circumference of the cell. They are always observed with other components in a structural complex that includes the following: 1. a system of MFs, in which individual elements are aligned along the sides of the MTs and crossbridged to them; 2. a system of cooriented tubular endoplasmic reticulum (ER) lying beneath the MTs, and 3. the plasma membrane (PM) to which the MTs appear to be extensively linked. The cortical cytoskeleton is thus structurally complex, and contains elements such as MFs and ER that must be considered together with the MTs in any attempt to elucidate cytoskeletal function. MTs are also observed within the vegetative cytoplasm either singly or in small groups. Observations reveal that some of these may be closely associated with the envelope of the vegetative nucleus. MTs of the generative cell, in contrast to those of the vegetative cytoplasm, occur tightly clustered in bundles and show extensive cross-bridging. These bundles, especially in the distal tail of the generative cell, are markedly undulated. MFs are observed commonly in the cytoplasm of the vegetative cell. They occur in bundles oriented predominantly parallel to the pollen tube axis. Although proof is not provided, we suggest that they are composed of actin and are responsible for generating the vigorous cytoplasmic streaming characteristic of living pollen tubes.