1,721,056 research outputs found
Linneo ad Acireale
No full textIn questo lavoro si traccia il profilo del botanico siciliano Giuseppe Riggio inserendolo nel contesto della contemporanea ricerca scientifica europea
Do not throw away anything from the pig.
No full textAmong the surgical sciences, paediatric cardiac surgery is one of the closest to the concept of reconstruction. Despite the common use of the verb ‘to recycle’ in the third millennium, this notion cannot always be applied to our field and a multitude of materials, patches and conduits have to be used, often leading to rejection, aneurysm formation, calcification and stenosis.
Moreover, our population is very particular for the potential of growing inherent to the age of patients. For these reasons we are forced to use materials that can give the best results in short-term follow-up but that cannot remain effective in the longer term.
The opportunity to use living materials, growing patches or valves, opens up exciting possibilities—opens up incredible possibilities for our patients.
The extracellular matrix (ECM) is the naturally-occurring bioscaffold that surrounds cells in almost all tissues and organ structures. It is an acellular biomaterial that is gradually remodelled, leaving behind organized and healthy tissue. When implanted as a patch, the ECM acts as a scaffold into which the patient's cells migrate and integrate until it is gradually replaced. ECMs originating from various organs have been tested and good results reported.
Among the types available, the CorMatrixTM patch (CorMatrix®, Alpharetta, Georgia, USA), which is derived from porcine small intestinal submucosa extracellular matrix (SIS-ECM), is one of the most promising options among those commercially available.
In this issue of the Journal [1], Witt and colleagues report their experience in the use of the SIS-ECM CorMatrix patch in 37 paediatric patients. Their patient population was divided into four groups, depending on the implant location: septal defect patching, vascular patching, outflow tract patching or valve reconstruction.
There were four deaths (10.8%) at a follow-up time of 411 ± 225 days (range 62–757 days), with no death attributed to the implanted SIS-ECM, even though, in one patient with coronary ostial stenosis after supravalvular aortic patch enlargement, the suspicion of a relationship is legitimate.
The best results were reported in the septal closure group. Unfortunately, a septal closure can be accomplished perfectly with many other cheaper materials and the potential of SIS-ECM is probably greatly reduced in this situation. In adult patients, where the extent of the patch is bigger, SIS-ECM is probably justified and could provide better results in terms of the possibility of restoring suitable cardiac muscle.
In pulmonary or aortic enlargement plasty, the growth potential of SIS-ECM is interesting. In Witt's experience [1], vascular patching accounted for more than 50% of SIS-ECM patch applications (26 locations), with just one re-operation for pulmonary artery residual stenosis. No aneurysm formation was reported when used for aortoplasty [1].
This promising experience confirms that of others. Indeed, Padalino implanted SIS-ECM patch on the abdominal aorta in 15 rats [2]. Graft re-population was demonstrated as early as 15 days after implantation, while it was almost completely remodelled 180 days after implantation. No significant graft aneurysmatic dilation or detachment was present. The new aortic wall presented with an intima incorporating an endothelial lining, a media with smooth muscle cells and an adventitia containing vessels and fibroblasts [2].
The same encouraging results were not obtained in the clinical experience by McCready, who reported seven episodes of patch aneurysm among 76 patients who had undergone patch angioplasty of the carotid artery following endoarterectomy [3]. The patch used in this latter study was another SIS-ECM product (Surgisis® by Cook Surgical, Bloomington, IN, USA) that was thinner than CorMatrix. However, aneurysmal dilation of the graft patch has been described when the CorMatrix was used in carotid patch angioplasty.
As regards right ventricular outflow tract (RVOT) reconstruction, Witt reported on six patients with one re-operation. In three patients, a unicusp SIS-ECM valve was created but, unfortunately, one patient died from low cardiac output and the other two showed moderate-to-severe valve incompetence.
School reported four unicusp valves implanted in pulmonary outflow tract reconstruction with three of them competent at an average follow-up of 9 months: too short to be of significance [4]. Quarti reported 26 cases treated with SIS-ECM patch reconstruction, nine of which were cusp extension valvular repairs: five aortic, two tricuspid, one mitral and one pulmonary valve. At a mean follow-up of 12.5 months no patients had undergone re-operation and no more than mild incompetence was evident [5].
A large variability of results is evident among all the reported experiences. An interesting experimental study by Tottey confirms that differences exist in the composition, structure and mechanical properties of SIS-ECM prepared from tissues harvested from animals of different ages. In their conclusion, SIS-ECMs harvested from pigs aged 12 weeks are suitable for withstanding substantial mechanical loading after in vivo implantation and remodelling into load-bearing or force-generating tissues, while animals aged >52 weeks will yield scaffolds that may persist longer after in vivo implantation [6].
The interactions between the CorMatrix patch and the surrounding tissues can also be affected by the implantation techniques, the suture materials and other factors, potentially explaining the extreme variability of the results.
In our experience in Bologna, the SIS-ECM CorMatrix patch was used in 19 locations on 16 patients (septal patch in 6; pulmonary artery patch enlargement in 5; valve reconstruction in 5 [3 aortic, 1 mitral and 1 tricuspid]; Senning procedure as part of double switch operation in 2 and aortic arch reconstruction in 1). All patients are alive at a mean follow-up of 15 months. One patient underwent re-operation for recurrent incompetence 24 months after repair of a dysplastic aortic valve. The explanted patch appeared pliable and without any calcification.
Our impression is that the SIS-ECM CorMatrix patch is very useful in pulmonary artery enlargement and valve cusp extension by reason of its pliability and thinness, whilst it is probably not necessary for septal closure. Since clinical studies so far have limited follow-up, it is not possible to confirm the ability of the patch to regenerate normal tissue in anatomical and functional terms, although this has been demonstrated in experimental studies. However, the absence of calcific degeneration is encouraging and sufficiently important to recommend its use.
If the material proves capable of allowing for growth, previously unimagined possibilities will open up, forever solving all the problems related to the use of non-living materials
Tetralogy of Fallot with coronary-to-pulmonary artery fistula: a diagnostic snare.
No full textAn 11-month-old infant, moderately cyanotic, with diagnosis of tetralogy of Fallot underwent corrective surgery. At echocardiographic evaluation, a subatretic right ventricular outflow tract without aortopulmonary collateral arteries, confluent pulmonary arteries and normal coronary pattern were evidenced. During operation, an undiagnosed large coronary-to-pulmonary artery fistula was disclosed. Because of the large variety of aortopulmonary collateral arteries that can be associated with this pathology, further imaging study is mandatory when oxygen saturation does not match the right ventricular outflow tract obstruction severity
Neonatal aortic arch surgery
No full textSurgical repair of the aortic arch is entailed in the neonatal period of patients with: hypoplastic left heart syndrome, interrupted aortic arch, hypoplastic aortic arch and complex aortic coarctation. Aortic arch surgery requires a period of circulatory arrest and deep hypothermia. Cerebral selective perfusion has recently been introduced as an alternative to circulatory arrest with the aim of reducing mortality and neurological complications. Moreover, the arch reconstruction phase can be safely performed under moderate hypothermia and with cerebral and myocardial perfusion (on beating heart), thus, completely avoiding cerebral ischemia and completely avoiding or drastically reducing myocardial ischemi
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
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
- …
