1,721,146 research outputs found
Vena capitis prima and the cavernous sinus in human embryos and fetuses
No full textAfter the intracranial venous-drainage route is switched from the vena capitis prima (VCP) to the transverse sinus, the cavernous sinus is considered to develop from a connecting part of the VCP with the ophthalmic vein (OPV). Observations of histological sections from 12 embryos and 47 fetuses (6-35 weeks) demonstrated that (1) at six weeks, a major tributary of the VCP ran inferiorly in the plica ventralis at the mesencephalic flexure (future tentrium cerebelli) and merged with the OPV in the medial side of the trigeminal ganglion; (2) at seven weeks, being independent of the laterally located primary veins, the superior petrosal sinus (SPS) developed medially in the plica, ran superiorly, and appeared to make an initial confluence with the transverse sinus; (3) until 15-16 weeks, parasellar veins were limited to a few branches of the OPV without communication with the SPS on the lateral surface of the trigeminal ganglion; (4) after 15-16 weeks, parasellar veins increased in number and volume but did not yet drain into the SPS but rather into the newly built inferior petrosal sinus; and (5) near term, parasellar veins started venous drainage to the SPS, whereas few veins were evident around the intracavernous abducens nerve. Consequently, the inferior petrosal sinus might originate from a remnant of the VCP (the so-called pro-otic sinus), but after midterm, most parasellar veins appeared to develop from the OPV without any contribution of the SPS. These findings suggest that parasellar sinus-network might be established after birth.Depto. de Anatomía y EmbriologíaFac. de MedicinaTRUEpu
Examination of the Annular Tendon (Annulus of Zinn) as a Common Origin of the Extraocular Rectus Muscles: 2. Embryological Basis of Extraocular Muscles Anomalies
No full textPurpose: Many reports have described anomalous connections of the superior rectus (SR) with other extraocular rectus muscles, in which additional heads of the other three rectus muscles likely provided the connections. We examined how these connections are established during fetal development.
Methods: We analyzed paraffin-embedded horizontal sections from 25 late-stage fetuses. Horizontal sections are best suited for understanding the mediolateral relationships of muscle origins.
Results: We confirmed a common tendinous origin of the lateral rectus (LR), inferior rectus (IR) and medial rectus (MR) muscles that was separated from the SR origin. Notably, eight fetuses (32%) had tendinous or muscular connections between the SR and other rectus muscles that had one of four morphologies: (a) a thin tendon from the SR to the common tendon of the three rectus muscles (2 fetuses), (b) a thin tendon to the LR (one fetus), (c) a thin tendon to the inferior rectus muscle origin (two fetuses), and (d) SR muscle fibers arising from an additional head of the LR (three fetuses).
Conclusions: The SR seemed to issue a thin tendon that passed along the inferior or lateral side of the oculomotor nerve. Conversely, the LR and inferior rectus muscle were likely to carry a supernumerary bundle that reached the SR. The accessory head of the medial rectus muscle showed a stable morphology in that it seemed to also provide an anomalous double head. However, the presence of an accessory head in the LR was rare. In contrast with our previously published diagram of the orbital apex, the accessory head of the medial rectus muscle passed along the lateral side of the superior oblique.Depto. de Anatomía y EmbriologíaFac. de MedicinaTRUEpu
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
Transient connection or origin of the inferior pharyngeal constrictor during fetal development: A study using human fetal sagittal sections
No full textThe inferior pharyngeal constrictor (IPC) originates from the thyroid and cricoid cartilages and inserts to the pharyngeal raphe. In serial sagittal sections of 37 embryos and fetuses at 6–15 weeks (crown rump length 15–115 mm), we found (1) the IPC connecting to the sternothyroideus and thyrohyoideus muscles (16 fetuses at 6–11 weeks) or (2) the cricothyroideus muscle (6 fetuses at 12–15 weeks) in addition to the usual cricoid origin. These aberrant connections were most likely to be transient origins of the IPC not from a hard tissue but nearby striated muscles. In four of the latter six specimens, a tendinous band from the IPC inferior end connected to the cricothyroideus muscle to provide a digastric muscle-like appearance. These aberrant connections with nearby muscles seemed to become separated by a growing protrusion of the thyroid cartilage. Therefore, these aberrant origins were, even if developed, most likely to be “corrected” to the adult morphology during midterm or late prenatal period. The aberrant or transient origin of the IPC seemed to result from a discrepancy in growth of the cartilage and muscles. Such a discrepancy in growth seems to resemble the IPC wrapping around the superior cornu of thyroid cartilage. In addition, a final or adult-like morphology was found in two of the present 37 fetal specimens. It seemed to suggest a significant redundancy in growth rate of the laryngeal structures.JSPS KAKENHIDepto. de Anatomía y EmbriologíaFac. de MedicinaTRUEpu
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
Perineal raphe with special reference to its extension to the anus: a histological study using human fetuses
No full textThe raphe of the human penis and scrotum is considered to develop secondarily after disappearance of the initial midline seam by fusion of the bilateral genital folds. However, the fetal development was still obscure. We examined histological sections of 30 fetuses (17 males and 13 females) at 10–15 weeks. In male fetuses, the scrotum was not yet clearly identified because of no descent of testis. The perineal raphe was thin and wavy at 10 weeks, and it was continuous with and took a direction same as the inferior wall of the closed penile urethra after physiological hypospadias. Depending on growth of the bulbospongiosus muscle and corpus spongiosus penis, the midline intermuscular septum obtained a connection to the subcutaneous wavy raphe and made the latter thick and straight at 12–15 weeks. Notably, the perineal raphe extended posteriorly to attach to the external anal sphincter. In female fetuses, an epithelial fusion occurred along a short distance at the posterior end of the vestibule. However, in front of the external anal sphincter, a large midline mesenchymal tissue from the urorectal septum did not contain a raphe-like structure. Moreover, since the bilateral bulbospongiosus muscles were separated widely by the vestibule, they did not provide a midline septum. Fetal development of the perineal raphe was accelerated by reinforcement from the muscular septum. In contrast, without such a muscular support, the female raphe could not maintain its growth even if the seed appeared at the posterior end of the vestibule.National Natural Science Foundation (China)Depto. de Anatomía y EmbriologíaFac. de MedicinaTRUEpu
Development of the pulmonary pleura with special reference to the lung surface morphology: a study using human fetuses
No full textIn and after the third trimester, the lung surface is likely to become smooth to facilitate respiratory movements. However, there are no detailed descriptions as to when and how the lung surface becomes regular. According to our observations of 33 fetuses at 9-16 weeks of gestation (crown-rump length [CRL], 39-125 mm), the lung surface, especially its lateral (costal) surface, was comparatively rough due to rapid branching and outward growing of bronchioli at the pseudoglandular phase of lung development. The pulmonary pleura was thin and, beneath the surface mesothelium, no or little mesenchymal tissue was detectable. Veins and lymphatic vessels reached the lung surface until 9 weeks and 16 weeks, respectively. In contrast, in 8 fetuses at 26-34 weeks of gestation (CRL, 210-290 mm), the lung surface was almost smooth because, instead of bronchioli, the developing alveoli faced the external surfaces of the lung. Moreover, the submesothelial tissue became thick due to large numbers of dilated veins connected to deep intersegmental veins. CD34-positive, multilayered fibrous tissue was also evident beneath the mesothelium in these stages. The submesothelial tissue was much thicker at the basal and mediastinal surfaces compared to apical and costal surfaces. Overall, rather than by a mechanical stress from the thoracic wall and diaphragm, a smooth lung surface seemed to be established largely by the thick submesothelial tissue including veins and lymphatic vessels until 26 weeks.Ministerio de Educación, Cultura, Deportes, Ciencia y Tecnología (Japón)Depto. de Anatomía y EmbriologíaFac. de MedicinaTRUEpu
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