1,720,979 research outputs found
Role of sphingosylphosphorylcholine on skeletal muscle denervation and regeneration
No full textPresent work is aimed at studying the role of sphingosylphosphorylcholine
(SPC), a natural bioactive sphingomyelin derivative, on denervation
and regeneration of skeletal muscle. SPC is known to
participate in growth, proliferation and survival of various cell
systems. The experiments were performed in adult rats. SPC was
continuously released by a mini-osmotic pumps connected by a
catheter to control, denervated or regenerating (after bupivacaine
injection) soleus muscles. Supplementation of SPC to adult muscles,
produced significant atrophy of fibres and light changes to fibre type
composition. In contrast, SPC did not influence denervation atrophy.
During regeneration, SPC produced alterations on fibre dimensions
and on myosin expression. In conclusion, it appears that SPC exerts
distinctive actions depending on definite condition of skeletal muscl
Effects of sphingomyelin derivatives on innervated and denervated rat soleus muscle
No full textPresent work is aimed at studying the effects of natural bioactive
sphingomyelin derivatives, on normal and denervated
slow-twitch skeletal muscle. The effects on fibre cross sectional
area and myosin heavy chains composition of sphingosine
(SPH), sphingosine 1-phosphate (S1P) and sphingosylphosphorylcholine
(SPC) were studied. Denervation was bilaterally
performed cutting the sciatic nerve at the level of trochanter
in adult rats. A group of animals was used as controls.
Sphingolipids were continuously released by a mini-osmotic
pumps implanted subcutaneously in the scapular region and
connected by a catheter to the left (control or denervated) soleus
muscles. Supplementation of SPC to adult control soleus
muscle, produced significant atrophy of fibres and small
changes to fibre type composition. No significant effects of
SPH and S1P were found. In contrast, SPH and, to a smaller
extent, S1P reduced the atrophy and the slow-to-fast transformation
produced by 7-14 days of denervation. Preliminary
results indicate that these sphingolipids may exert their action
by reducing the overall muscle apoptosis and by activating
satellite cells
Myosin light chains of avian and mammalian slow muscles: peptide mapping of 2S light chains.
No full textJ Muscle Res Cell Motil. 1984 Aug;5(4):411-21.
Myosin light chains of avian and mammalian slow muscles: peptide mapping of 2S light chains.
Dalla Libera L, Betto R, Lodolo R, Carraro U.
Abstract
The 2S light chains of mammalian and avian slow muscle myosin, indistinguishable by two-dimensional gel electrophoresis, have been examined by peptide mapping. The fragments obtained with S. aureus V8 protease were analysed either by gel electrophoresis or by reverse-phase high performance liquid chromatography. The peptide maps of avian 2S light chains contain fragments distinct from those of mammalian 2S light chains. Chicken and turkey LC2S appear to be more similar to each other than those from mammalian species (rat and rabbit). These results are in agreement with the relative phylogenetic distances among the four species studied here. The 2S light chain of slow muscle represent further examples of polypeptides which comigrate in two-dimensional gel electrophoresis in spite of their different peptide maps.
PMID:
6384262
[PubMed - indexed for MEDLINE
Maximum shortening velocity and coexistence of myosin heavy chain isoforms in single skinned fast fibres of rat skeletal muscle.
No full textMyosin heavy chain composition of a large number (288) of single fibres from slow (soleus), and fast (superficial part of tibialis anterior, and plantaris) muscles of adult (3-5-month-old) Wistar rats was determined. A combination of SDS-PAGE and monoclonal antibodies against myosin heavy chains allowed to identify four myosin heavy chain isoforms (1, 2A, 2X, and 2B) and to detect myosin heavy chain coexistence. Four groups of fibres containing only one myosin heavy chain (1 myosin heavy chain, 2A myosin heavy chain, 2X myosin heavy chain, and 2B myosin heavy chain), and five groups containing more than one myosin heavy chain (1 and 2A myosin heavy chains, 2A and 2X myosin heavy chains, 2X and minor amounts of 2B (2X-2B fibres), 2B and minor amounts of 2X (2B-2X fibres), and 2A, 2X, and 2B myosin heavy chain were identified and their relative percentages were assessed. Coexistence of fast myosin heavy chain isoforms was found to be very frequent (50\% of the fibres in plantaris, and 30\% in tibialis anterior), whereas coexistence of slow and fast (2A) myosin heavy chain was very rare. Maximum shortening velocity (V0) was determined using the slack-test procedure in a subset of 109 fast fibres from the above population. The values of V0 formed a continuum extending from 2A to 2X to 2X-2B to 2B-2X to 2B fibres. 2A fibres had the lowest value of V0 and 2B fibres the highest. Only the differences between 2A and 2B and 2A and 2B-2X fibres were statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS
Effects of age on sarcoplasmic reticulum properties and histochemical composition of fast- and slo-twitch rat muscles
No full textCalcium release activity of sarcoplasmic reticulum and enzyme-histochemical properties were investigated in extensor digitorum longus (e.d.l.) and soleus muscles in young (4 months and old (24 months) male rats. With age, the caffeine threshold concentration for calcium release from the sarcoplasmic reticulum of soleus skinned muscle fibres showed only minor modifications. On the other hand, in e.d.l. skinned muscle fibres, the caffeine threshold concentration decreased significantly (P < 0.05). The histochemical fibre type composition changed with age both in soleus and in e.d.l. muscles, showing a common transformation toward a more oxidative histochemical profile. In fact, in aged soleus, a significant (P < 0.05) increase was observed of type 1 fibres to represent almost the totality of the muscle fibres (more than 98%), while types 2C and 2A were reduced in proportion. In aged e.d.l. the percentage of type 1 (P < 0.05), 2A and 2X (a recently identified fourth component of the fast-twitch muscle types) fibres increased, with a reduction of type 2B (P < 0.01) fibres. The present results suggest that the changes in contractile properties of aged muscles may be related to the changes not only in fibre composition but also in the mechanism of calcium release from sarcoplasmic reticulum
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
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