1,721,001 research outputs found
BONE REGENERATION OF THE CRANIOFACIAL SKELETON WITH BIOENGINEERED SCAFFOLDS
Full text linkLa ricostruzione dei difetti ossei del massiccio facciale rappresenta una sfida chirurgica e attualmente la miglior soluzione, in uso nella pratica clinica, consiste nell’impiego di lembi liberi microchirurgici. Il campo della bioingegneria sta crescendo notevolmente e fornisce alcune alternative alla ricostruzione ossea. Durante il dottorato sono stati condotti una serie di studi preclinici al fine di valutare la performance degli scaffold bioingegnerizzati nella rigenerazione ossea del distretto craniofacciale. Nello studio pilota due tipi di scaffold (un idrogelo costituito da polietilen glicole-chitosano [HyCh] e uno scaffold nato dalla combinazione di acido polilattico, policaprolattone e HyCh [PLA-PCL-HyCh]), seminati con cellule staminali mesenchimali umane (hMSCs) in diverse concentrazioni (i.e. 1000, 2000, and 3000 cells/mm 3 ), sono stati testati per la ricostruzione di difetti mandibolari non critici nel modello animale di coniglio. Le proprietà rigenerative degli scaffold bioingegnerizzati sono state analizzate con studi radiologici in vivo ed analisi radiologiche ed istologiche ex vivo. E’ stato dimostrato che la rigenerazione ossea può essere incrementata significativamente attraverso l’utilizzo di una ricostruzione con scaffold o con scaffold seminato, ottenendo rispettivamente una rigenerazione ossea del 50% e del 70% del sito chirurgico in 120 giorni, confrontata con il 40% che si ottiene con la rigenerazione spontanea. Questi risultati hanno permesso di stabilire un riferimento di base per ulteriori esperimenti volti all’ottimizzazione della performance rigenerativa. E’ stato avviato un primo tentativo di ottimizzare il modello di base con un trapianto allograft di cellule staminali (i.e. rabbit mesenchymal stromal cells [rMSCs] in sostituzione delle hMSCs) e con la somministrazione topica di BMP-2 (i.e. scaffolds seminati con hMSCs a cui si aggiunge BMP-2). Purtroppo i risultati sperimentali così ottenuti non hanno superato il riferimento di base. Studi successivi sono stati dedicati alla progettazione e sviluppo di un nuovo tipo di scaffold composito con architettura core-shell. Tale scaffold grazie alla struttura reticolare del core prodotto mediante stampante 3D presenta notevole versatilità ed eccellenti proprietà meccaniche. Il nuovo scaffold è stato introdotto per testare la possibilità di rigenerare difetti con dimensioni critiche. I risultati ottenuti non sono stati completamente soddisfacenti a causa di problematiche legate al fissaggio subottimale dello scaffold a livello del difetto chirurgico. Infine sono stati eseguiti diversi studi ancillari per fare chiarezza in alcune problematiche della rigenerazione ossea: 1) è stata dimostrata la fattibilità della ricostruzione con scaffold bioriassorbibile di un difetto segmentale di mandibola nel coniglio con un lungo follow up (i.e. 3 months) nessuna complicanza maggiore; 2) è stato sviluppato un valido modello di osteoradionecrosi mandibolare con ottima correlazione dose-effetto biologico anche se, dal punto di vista rigenerativo, lo scaffold seminato con hMSCs non è riuscito a promuovere il processo neo-osteogenetico; 3) è stato condotto uno studio preliminare per investigare l’interazione tra le hMSCs e le cellule tumorali e al momento non sono emerse evidenze che supportino la teoria che le hMSCs possano favorire la crescita tumorale.Reconstruction of maxillofacial skeleton defects is a surgical challenge, and microvascular reconstruction is the current gold standard. The field of tissue bioengineering has been providing an increasing number of alternative strategies for bone reconstruction. We performed a series of preclinical studies to assess the performance of bioengineered scaffolds in craniofacial bone regeneration. In our pilot study an hydrogel made of polyethylene glycol-chitosan (HyCh) and a core-shell combination of poly(L-lactic acid)/poly(ε-caprolactone) and HyCh (PLA-PCL-HyCh), seeded with different concentrations of human mesenchymal stromal cells (hMSCs) (i.e. 1000, 2000, and 3000 cells/mm3), has been explored in non-critical size mandibular defects in a rabbit model. The bone regenerative properties of the bioengineered scaffolds were analyzed by in vivo radiological examinations and ex vivo radiological, histomorphological, and immunohistochemical analyses. We demonstrate that bone regeneration can be boosted by scaffold- and seeded scaffold-reconstruction, achieving, respectively, 50% and 70% restoration of presurgical bone density in 120 days, compared to 40% restoration seen in spontaneous regeneration. These results helped to establish a baseline reference for further experiments and we started to search for an optimization of the regenerative performance. We tried to optimize the baseline model though the application of an allograft model (i.e. seeding rabbit mesenchymal stromal cells [rMSCs] instead of hMSCs) and though the local administration of BMP-2 (i.e. bioengineered scaffolds seeded with hMSCs, implemented with BMP-2). Unfortunately the experimental results could not overcome the outcome of 70% restoration of presurgical bone density in 120 days. Afterwards our team developed and produced a new hybrid core-shell composite scaffolds in 3D-printed PLA-HyCH with excellent mechanical properties. We introduced a the new composite scaffold in our experiments, testing the possibility of regenerating of critical size defects, but once again we could not obtain a better performance than our reference value. This finding probably was consequence of suboptimal fixation of the scaffolds at level of the surgical defects. Moreover, some ancillary studies were performed in order to clarify some issues of the bone regeneration: 1) the feasibility of the reconstruction of a segmental mandibular defect though a bioresorbable hybrid core-shell composite scaffold was proved with a long follow up (i.e. 3 months) of the animal without any major complication; 2) a valid animal model of mandibular osteoradionecrosis with an excellent correlation between dose and biological damage was developed, but, from the regenerative standpoint, the scaffold-hMSC model could not highly catalyze the bone repair of bone defects in this particular setting; 3) a preliminary investigation focused on the interaction between hMSCs and tumor cells was accomplished, and, from the few data obtained at the moment, no evidence supported the hypothesis that hMSCs could promote tumor growth
Precision Medicine in the Treatment of Malignancies Involving the Ventral Skull Base: Present and Future
No full textWhen is a multidisciplinary surgical approach required in sinonasal tumours with cranial involvement?
Full text linkThe term "sinonasal tumours" includes a large spectrum of diseases, which are characterized by heterogeneous biological behavior and prognosis, and located in a critical anatomic area. Diagnosis and treatment of sinonasal tumours require the contribution of different disciplines. A narrative review was performed to highlight the role of surgeons in contributing to a multidisciplinary approach to sinonasal tumours. Diagnosis and staging of sinonasal tumours is challenging and requires collaboration between surgeons, radiologists, and pathologists. The identification and management of critical extensions (orbital or intracranial encroachment, vascular abutment or encasement) is fundamental for successful treatment. Most cases of advanced sinonasal tumours can undergo surgical intervention by an adequately trained otorhinolaryngological team. The contribution of neurosurgeons and oculoplastic surgeons is required in selected scenarios. In rare circumstances, multidisciplinary reconstructive strategies can be indicated for complex tissue defects. Furthermore, a multidisciplinary approach is pivotal in the management of perioperative complications. While surgery remains the mainstay of treatment, the role of non-surgical adjuvant or even exclusive treatments is constantly expanding
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Margins in oncologic nasopharyngeal surgery: a systematic review with meta-analysis
No full textObjective. Nasopharyngeal malignancies are rare heterogenous histologies (nasopharyngeal carcinoma [NPC], minor salivary glands carcinomas, and low-grade papillary nasopharyngeal adenocarcinoma) and a significant proportion of patients experience loco-regional recurrence after primary treatment. Resection margin status is a key prognostic factor that influences recurrence and survival, although definitions and criteria for negative, close, and positive margins remain inconsistent. This systematic review with meta-analysis aimed to summarise the existing definitions of resection margins in the literature and evaluate their impact on clinical outcomes in patients undergoing nasopharyngectomy with a specific focus on NPC. Methods. A systematic literature review was conducted according to PRISMA guidelines. Electronic databases (Scopus, PubMed, and Web of Science) were searched up to November 2024. Studies reporting on surgical margins and survival outcomes in patients with NPC treated with endoscopic or open nasopharyngectomy were included. Pooled odds ratios (OR) for overall survival (OS), diseasespecific survival (DSS), and disease-free survival (DFS) were calculated using a random-effects model. Results. A total of 45 studies met the inclusion criteria, with 12 included in the meta-analysis. Positive surgical margins were associated with worse 5-year DFS (OR 2.21, 95% CI 1.55-3.14, p < 0.001), while no significant impact was observed on 3-year DFS (OR 2.3, p = 0.239), 3-year OS (OR 2, p = 0.167), 5-year OS (OR 2.98, p = 0.115), 3-year DSS (OR 1.25, p = 0.761), or 5-year DSS (OR 2.57, p = 0.265). Margin positivity rates were 16.9% for endoscopically-treated NPC, 20.6% for open-surgery NPC, and 20.6% for mixed histology, with no significant difference between surgical approaches (p = 0.995). Conclusions. Positive resection margins significantly impact DFS in recurrent NPC. Standardised margin definitions are needed to improve prognostication and guide decisions on adjuvant therapy
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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