1,721,064 research outputs found
Ribosome biogenesis: from structure to dynamics.
No full textIn this chapter we describe the status of the research concerning the nucleolus, the major nuclear body. The nucleolus has been recognized as a dynamic organelle with many more functions than one could imagine. In fact, in addition to its fundamental role in the biogenesis of preribosomes, the nucleolus takes part in many other cellular processes and functions, such as the cell-cycle control and the p53 pathway: the direct or indirect involvement of the nucleolus in these various processes makes it sensitive to their alteration. Moreover, it is worth noting that the different nucleolar factors participating to independent mechanisms show different dynamics of association/disassociation with the nucleolar body
A mechanism for the export of the small ribosomal subunits as revealed by cytochemical labeling at fluorescence and electron microscopy
No full textEffect of physical exercise on the ultrastructural features of skeletal muscle mitochondria in old mice.
No full textSarcopenia is an age-related decline of muscle mass, strength and quality which represents a potent risk factor for frailty, loss of independence and physical disability in elderly. The mechanisms leading to sarcopenia are still largely unknown and no specific therapy is presently available to counteract its onset or progress. Several studies have stressed the importance of physical exercise as an effective approach to prevent/limit the sarcopenic process. In the present work we have investigated at transmission electron microscopy the effects of treadmill running on the mitochondrial structure in aged skeletal muscle by comparing exercised versus sedentary old (28 months) mice, and using adult (12 months) individuals as control. Our observations demonstrated that ageing induces an accumulation of mitochondria characterised by larger size and longer cristae than in adulthood, and by a frequent association with lipid droplets. The mitochondrial alterations are partially reversed in old mice after treadmill running, thus providing further evidence that an adapted physical exercise may represent a suitable non-pharmacologic approach to limit the negative effects of ageing on the skeletal muscle, even when applied at late age
Aging in the Skeletal Muscle Revealed by Molecular Immunohistochemical Imaging
Full text linkThe skeletal muscle is a complex organ mainly composed of multinucleated fibres responsible for contractile activity, but it also contains postnatal myogenic stem cells (i.e., satellite cells), connective cells and nervous cells. The skeletal muscle is severely affected by aging, undergoing a progressive reduction in muscle mass, strength and endurance in a condition known as sarcopenia. The mechanisms underlying sarcopenia still need to be completely clarified, but they are undoubtedly multifactorial, involving all cell types constituting the skeletal muscle. Immunohistochemistry has widely been used to investigate skeletal muscle aging, identifying age-related molecular alterations in the various myofibre components, as well as in the satellite cells and peri-fibre environment. The wide range of immunohistochemical data reported in this review is proof of the primary role played by this long-established, yet modern, technique. Its high specificity for the molecules of interest, and the possibility of imaging and quantifying the signal in the real histological or cytological sites where these molecules are located and active, makes immunohistochemistry a unique and irreplaceable tool among the laboratory techniques in biomedicine
Molecular and structural alterations of skeletal muscle tissue nuclei during aging
Full text linkAging is accompanied by a progressive loss of skeletal muscle mass and strength. The mechanisms underlying this phenomenon are certainly multifactorial and still remain to be fully elucidated. Changes in the cell nucleus structure and function have been considered among the possible contributing causes. This review offers an overview of the current knowledge on skeletal muscle nuclei in aging, focusing on the impairment of nuclear pathways potentially involved in age-related muscle decline. In skeletal muscle two types of cells are present: fiber cells, constituting the contractile muscle mass and containing hundreds of myonuclei, and the satellite cells, i.e., the myogenic mononuclear stem cells occurring at the periphery of the fibers and responsible for muscle growth and repair. Research conducted on different experimental models and with different methodological approaches demonstrated that both the myonuclei and satellite cell nuclei of aged skeletal muscles undergo several structural and molecular alterations, affecting chromatin organization, gene expression, and transcriptional and post-transcriptional activities. These alterations play a key role in the impairment of muscle fiber homeostasis and regeneration, thus contributing to the age-related decrease in skeletal muscle mass and function
Uranyl-free staining as a suitable contrasting technique for nuclear structures at transmission electron microscopy
No full textUranyl acetate solution has widely been used as staining reagent for samples processed for ultrastructural morphology, cytochemistry, and immunocytochemistry. Although uranyl acetate guarantees high performance as a staining reagent, the radioactive uranyl salts make its use and purchase severely restricted. In this view, we used a non-radioactive lanthanide mix solution as contrasting dye for both nucleoplasmic and nucleolar ribonucleoprotein-containing components. This method guarantees a good contrast without masking the probe-antigen immunoreaction, thus proving to be a suitable tool for high-resolution studies of both cyto- and immunocytochemistry on acrylic resin-embedded samples
Simultaneous ultrastructural analysis of fluorochrome-photoconverted diaminobenzidine and gold immunolabelling in cultured cells
No full textDiaminobenzidine photoconversion is a technique by which a fluorescent dye is transformed into a stably insoluble, brown, electrondense signal, thus enabling examination at both bright field light microscopy and transmission electron microscopy. In this work, a procedure is proposed for combining photoconversion and immunoelectron microscopy: in vitro cell cultures have been first submitted to photoconversion to analyse the intracellular fate of either fluorescent nanoparticles or photosensitizing molecules, then processed for transmission electron microscopy; different fixative solutions and embedding media have been used, and the ultrathin sections were finally submitted to post-embedding immunogold cytochemistry. Under all conditions the photoconversion reaction product and the target antigen were properly detected in the same section; Epon-embedded, osmicated samples required a pre-treatment with sodium metaperiodate to unmask the antigenic sites. This simple and reliable procedure exploits a single sample to simultaneously localise the photoconversion product and a variety of antigens allowing a specific identification of subcellular organelles at the ultrastructural level
Ultrastructural immunocytochemistry shows impairment of RNA pathways in skeletal muscle nuclei of old mice: A link to sarcopenia?
Full text linkDuring aging, skeletal muscle is affected by sarcopenia, a progressive decline in muscle mass, strength and endurance that leads to loss of function and disability. Cell nucleus dysfunction is a possible factor contributing to sarcopenia because aging-associated alterations in mRNA and rRNA transcription/maturation machinery have been shown in several cell types including muscle cells. In this study, the distribution and density of key molecular factors involved in RNA pathways namely, nuclear actin (a motor protein and regulator of RNA transcription), 5-methyl cytosine (an epigenetic regulator of gene transcription), and ribonuclease A (an RNA degrading enzyme) were compared in different nuclear compartments of late adult and old mice myonuclei by means of ultrastructural immunocytochemistry. In all nuclear compartments, an age-related decrease of nuclear actin suggested altered chromatin structuring and impaired nucleus-to-cytoplasm transport of both mRNA and ribosomal subunits, while a decrease of 5-methyl cytosine and ribonuclease A in the nucleoli of old mice indicated an age-dependent loss of rRNA genes. These findings provide novel experimental evidence that, in the aging skeletal muscle, nuclear RNA pathways undergo impairment, likely hindering protein synthesis and contributing to the onset and progression of sarcopenia
Impairement of transcription in culture cells after in vivo incorporation of anti-RNP antibodies
No full textUse of halogenated precursors to define a transcription time window (ttw) after treatment with hypometabolizing molecules.
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