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Heterogeneous Tissue (heterogeneous + tissue)
Selected AbstractsPlasticity of human skeletal muscle: gene expression to in vivo functionEXPERIMENTAL PHYSIOLOGY, Issue 5 2007Stephen D. R. Harridge Human skeletal muscle is a highly heterogeneous tissue, able to adapt to the different challenges that may be placed upon it. When overloaded, a muscle adapts by increasing its size and strength through satellite-cell-mediated mechanisms, whereby protein synthesis is increased and new nuclei are added to maintain the myonuclear domain. This process is regulated by an array of mechanical, hormonal and nutritional signals. Growth factors, such as insulin-like growth factor I (IGF-I) and testosterone, are potent anabolic agents, whilst myostatin acts as a negative regulator of muscle mass. Insulin-like growth factor I is unique in being able to stimulate both the proliferation and the differentiation of satellite cells and works as part of an important local repair and adaptive mechanism. Speed of movement, as characterized by maximal velocity of shortening (Vmax), is regulated primarily by the isoform of myosin heavy chain (MHC) contained within a muscle fibre. Human fibres can express three MHCs: MHC-I, -IIa and -IIx, in order of increasing Vmax and maximal power output. Training studies suggest that there is a subtle interplay between the MHC-IIa and -IIx isoforms, with the latter being downregulated by activity and upregulated by inactivity. However, switching between the two main isoforms appears to require significant challenges to a muscle. Upregulation of fast gene programs is caused by prolonged disuse, whilst upregulation of slow gene programs appears to require significant and prolonged activity. The potential mechanisms by which alterations in muscle composition are mediated are discussed. The implications in terms of contractile function of altering muscle phenotype are discussed from the single fibre to the whole muscle level. [source] Analysis of neuronal gene expression with laser capture microdissectionJOURNAL OF NEUROSCIENCE RESEARCH, Issue 5 2002Valerie A.M. Vincent Abstract The brain is a heterogeneous tissue in which the numbers of neurons, glia, and other cell types vary among anatomic regions. Gene expression studies performed on brain homogenates yield results reflecting mRNA abundance in a mixture of cell types. Therefore, a method for quantifying gene expression in individual cell populations would be useful. Laser capture microdissection (LCM) is a new technique for obtaining pure populations of cells from heterogeneous tissues. Most studies thus far have used LCM to detect DNA sequences. We developed a method to quantify gene expression in hippocampal neurons from mouse brain using LCM and real-time reverse transcriptase-polymerase chain reaction (RT-PCR). This method was optimized to permit histochemical or immunocytochemical visualization of nerve cells during LCM while minimizing RNA degradation. As an example, gene expression was quantified in hippocampal neurons from the Tg2576 mouse model for Alzheimer's disease. © 2002 Wiley-Liss, Inc. [source] Microenvironment regulation of PRG4 phenotype of chondrocytesJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 5 2007Megan E. Blewis Abstract Articular cartilage is a heterogeneous tissue with superficial (S), middle (M), and deep (D) zones. Chondrocytes in the S zone secrete the lubricating PRG4 protein, while chondrocytes from the M and D zones are more specialized in producing large amounts of the glycosaminoglycan (GAG) component of the extracellular matrix. Soluble and insoluble chemicals and mechanical stimuli regulate cartilage development, growth, and homeostasis; however, the mechanisms of regulation responsible for the distinct PRG4-positive and negative phenotypes of chondrocytes are unknown. The objective of this study was to determine if interaction between S and M chondrocytes regulates chondrocyte phenotype, as determined by coculture in monolayer at different ratios of S:M (100:0, 75:25, 50:50, 25:75, 0:100) and at different densities (240,000, 120,000, 60,000, and 30,000 cells/cm2), and by measurement of PRG4 secretion and expression, and GAG accumulation. Coculture of S and M cells resulted in significant up-regulation in PRG4 secretion and the percentage of cells expressing PRG4, with simultaneous down-regulation of GAG accumulation. Tracking M cells with PKH67 dye in coculture revealed that they maintained a PRG4-negative phenotype, and proliferated less than S cells. Taken together, these results indicate that the up-regulated PRG4 expression in coculture is a result of preferential proliferation of PRG4-expressing S cells. This finding may have practical implications for generating a large number of phenotypically normal S cells, which can be limited in source, for tissue engineering applications. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:685,695, 2007 [source] Computerised morphometric study of the paraurethral tissue in young and elderly womenNEUROUROLOGY AND URODYNAMICS, Issue 6 2002M. Verelst Abstract Aim. Changes in structural support of the urethra and bladder neck have been proposed to be among the most important factors in the pathogenesis of stress urinary incontinence. In this context, we histologically investigated the paraurethral area in continent women to quantify the relative distribution of connective tissue, smooth muscle, vessels, nerves, and striated muscle. Previously published literature gives only descriptive evaluations of the relative distribution of these tissue components. Methods. We used a computerised morphometric method, which allowed us to estimate the paraurethral tissue distribution in a more objective way. The material was obtained by dissection during autopsy in five premenopausal and five postmenopausal women. Results. Paraurethral tissue consisted of 56% connective tissue (SD, 5%), 30% smooth muscle (SD, 5%), 11% blood vessel (SD, 6%), 2% striated muscle (SD, 3%), and 1% nerves (SD, 1%). We also found that the distribution of different tissue components along the length of the urethra did not differ at a statistically significant level. Furthermore, there was a statistically significant difference in the amount of connective tissue and blood vessels in the postmenopausal women compared with the premenopausal women. Conclusions. The present study shows that the paraurethral area is built of heterogeneous tissue with small changes in its composition along the course of urethra. Increase in connective tissue was found to be the dominating change in the process of ageing. Neurourol. Urodynam. 21:529,533, 2002. © 2002 Wiley-Liss, Inc. [source] Analysis of neuronal gene expression with laser capture microdissectionJOURNAL OF NEUROSCIENCE RESEARCH, Issue 5 2002Valerie A.M. Vincent Abstract The brain is a heterogeneous tissue in which the numbers of neurons, glia, and other cell types vary among anatomic regions. Gene expression studies performed on brain homogenates yield results reflecting mRNA abundance in a mixture of cell types. Therefore, a method for quantifying gene expression in individual cell populations would be useful. Laser capture microdissection (LCM) is a new technique for obtaining pure populations of cells from heterogeneous tissues. Most studies thus far have used LCM to detect DNA sequences. We developed a method to quantify gene expression in hippocampal neurons from mouse brain using LCM and real-time reverse transcriptase-polymerase chain reaction (RT-PCR). This method was optimized to permit histochemical or immunocytochemical visualization of nerve cells during LCM while minimizing RNA degradation. As an example, gene expression was quantified in hippocampal neurons from the Tg2576 mouse model for Alzheimer's disease. © 2002 Wiley-Liss, Inc. [source] | ||||||||||