1,720,989 research outputs found
Beta-N-acetyl-D-glucosaminidase activity levels in atrophic gastrocnemius muscle of Rana esculenta.
No full text1. The atrophic status induced by long-term sciatectomy or tenotomy is different, since only in the first case have we found an irreversible muscular degeneration. 2. Up to 20 days after denervation or tenotomy the beta-N-acetylglucosaminidase showed increased specific activity. 3. The time-course of the beta-NAG increase is closely correlated with the loss of contractile capacity. 4. beta-NAG increases to 170% and does not fall in 20 days after cutting the nerve; but increases to 150% on day 4 and falls to 130% on day 20 after tenotomy
Performances in extreme environments: effects of hyper/hypobarism and hypogravity on skeletal muscle.
No full textMany environmental factors may affect muscle plasticity but some have exclusive
characteristics that allow them to play a key role to maintain the muscle capacity to generate
force; these factors are: i) the oxygen availability and ii) the load applied to muscle fibres.
Hyperbarism is a condition that occurs when a man is subjected to pressure increases. To keep
the lungs from collapsing, the air is supplied to him under high pressure which exposes the
blood in the lungs to high alveolar gas pressures. Under this condition, the PO2 become
sufficiently increased, serious disorders may occur, such as modification of oxygen delivery
and/or oxygen availability to permit regular muscle contraction. Also altitude hypobaric
hypoxia induces modification of muscle capacity to generate work. Prolonged exposure to high
altitude leads significant loss in body mass, thigh muscle mass, muscle fiber area and volume
density of muscle mitochondria. Spaceflight results in a number of adaptations to skeletal
muscle, including atrophy and early muscle fatigue. Muscle atrophy is observed in a wide
range of muscles, with the most extensive loss occurring in the legs, because astronauts are no
longer needed to support the body's weight. This review will describe the background on these
topics suggesting the strategies to correct the specific muscle changes in presence of
environmental stresses, such as the alteration in oxygen-derived signaling pathways or the
metabolic consequence of microgravity that may indicate rational interventions to maintain
muscle mass and function
Effetti della saponina sull’uptake di Ca++ in frazioni microsomiali purificate di muscolo sartorio di rana.
No full text
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
Cellular and molecular responses of human skeletal muscle exposed to hypoxic environment.
No full textThe effects of a hypobaric, hypoxic environment and exercise performed under extreme conditions, such as at high altitudes, are intriguing physiological aspects that need to be investigated directly on human climbers. Their skeletal muscle is one of the main tissues that can suffer from hypoxia and physical challenges, which will both define the muscle adaptation and the molecular signature of regenerative capacity. We investigated the muscle regenerative capacity characterizing satellite cells. Our study shows that satellite cells are altered by hypobaric, hypoxic environments and exercise performed at high altitudes. Of note, in human skeletal muscle after this 5,000 m a.s.l. expedition. SCs showed a significantly lower ability to regenerate skeletal muscle, in respect to before this high-altitude expedition. This impairment appears to be due to reduced satellite cell activity, consistent with their decreased myogenicity and fusion ability. Furthermore, at the transcriptional level several pathways, such as cell cycle, myogenesis, oxidative metabolism, proteolysis and sarcomeric protein synthesis, were found dysregulated
The S-100: a protein family in search of a function
No full textThe S-100 is a group of low molecular weight (10-12 kD) calcium-binding proteins highly conserved among vertebrates. It is present in different tissues as dimers of homologous or different subunits (alpha, beta). In the nervous system, the S-100 exists as a mixture composed of beta beta and alpha beta dimers with the monomer beta represented more often. Its intracellular localisation is mainly restricted to the glial cytoplasmic compartment with a small fraction bound to membranes. In this compartment the S-100 acts as a potent inhibitor of phosphorylation on several substrates including the synaptosomal C-Kinase and Tau, a microtubule-associated protein. The S-100 in particular conditions, after binding with specific membrane sites (Kd = 0.2 microM; Bmax = 4.5 nM), is able to modify the activity of adenylate cyclase, probably via G-proteins. In addition, the Ca2+ homeostasis is also modulated by S-100 via an increase of specific membrane conductance and/or Ca2+ release from intracellular stores. "In vitro" and "in vivo" experiments showed that lower (nM) concentrations of extracellular S-100 beta act on glial and neuronal cells as a growth-differentiating factor. On the other hand, higher concentrations of the protein induce apoptosis of some cells such as the sympathetic-like PC12 line. Finally, data obtained from physiological (development, ageing) or pathological (dementia associated with Down's syndrome, Alzheimer's disease) conditions showed that a relationship could be established between the S-100 levels and some aspects of the statii
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