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Epigenomic regulation of the transcriptome by DNA methylation and posttranscriptional gene silencing by miRNAs are potential environmental modulators of skeletal muscle plasticity to chronic exercise in healthy and diseased populations. We utilized transcriptome networks to connect exercise-induced differential methylation and miRNA with functional skeletal muscle plasticity. Biopsies of the vastus lateralis were collected from middle-aged Polynesian men and women with morbid obesity (44 kg/m(2) ± 10) and Type 2 diabetes before and following 16 wk of resistance (n = 9) or endurance training (n = 8). Longitudinal transcriptome, methylome, and microRNA (miRNA) responses were obtained via microarray, filtered by novel effect-size based false discovery rate probe selection preceding bioinformatic interrogation. Metabolic and microvascular transcriptome topology dominated the network landscape following endurance exercise. Lipid and glucose metabolism modules were connected to: microRNA (miR)-29a; promoter region hypomethylation of nuclear receptor factor (NRF1) and fatty acid transporter (SLC27A4), and hypermethylation of fatty acid synthase, and to exon hypomethylation of 6-phosphofructo-2-kinase and Ser/Thr protein kinase. Directional change in the endurance networks was validated by lower intramyocellular lipid, increased capillarity, GLUT4, hexokinase, and mitochondrial enzyme activity and proteome. Resistance training also lowered lipid and increased enzyme activity and caused GLUT4 promoter hypomethylation; however, training was inconsequential to GLUT4, capillarity, and metabolic transcriptome. miR-195 connected to negative regulation of vascular development. To conclude, integrated molecular network modelling revealed differential DNA methylation and miRNA expression changes occur in skeletal muscle in response to chronic exercise training that are most pronounced with endurance training and topographically associated with functional metabolic and microvascular plasticity relevant to diabetes rehabilitation.

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Zampanolide and its less active analog dactylolide compete with paclitaxel for binding to microtubules and represent a new class of microtubule-stabilizing agent (MSA). Mass spectrometry demonstrated that the mechanism of action of both compounds involved covalent binding to ß-tubulin at residues N228 and H229 in the taxane site of the microtubule. Alkylation of N228 and H229 was also detected in α,ß-tubulin dimers. However, unlike cyclostreptin, the other known MSA that alkylates ß-tubulin, zampanolide was a strong MSA. Modeling the structure of the adducts, using the NMR-derived dactylolide conformation, indicated that the stabilizing activity of zampanolide is likely due to interactions with the M-loop. Our results strongly support the existence of the luminal taxane site of microtubules in tubulin dimers and suggest that microtubule nucleation induction by MSAs may proceed through an allosteric mechanism.

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Peloruside A is a novel secondary metabolite isolated from a New Zealand marine sponge, Mycale hentscheli, that has potent paclitaxel-like microtubule-stabilizing activity and is cytotoxic at nanomolar concentrations. Its 16-membered macrolide ring is similar to that of epothilone, a drug currently under clinical investigation as an anticancer agent. Like paclitaxel, peloruside A arrests cells in the G(2)-M phase of the cell cycle and induces apoptosis. The relatively simple structure of peloruside makes it suitable for the design and synthesis of analogues with improved tumor targeting and reduced tumor cross-resistance.

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Using fetal sheep as the experimental model, we have elucidated some of the key events that culminate in the formation of primordial follicles. A special effort was made to determine the source of the somatic cells that ultimately become granulosa cells of primordial follicles. Between gestational days 38-100: (1) light and electron microscopy was used to characterize changes in ovarian histoarchitecture; (2) incorporation of BrdU was used to identify populations of proliferating cells within fetal ovaries before, during and after, follicular formation; and (3) in situ hybridisation was used to determine the cell-specific and temporal patterns of expression of mRNAs encoding for selected steroidogenic enzymes. At day 38 somatic (pregranulosa) cells were in contact with oogonia and easily distinguished from endothelial and mesenchymal cells. Between days 38 and 45, pregranulosa cell-oogonia complexes progressively coalesced to form 'tube-like' structures referred to as ovigerous cords. These cords consisted of pregranulosa cells and oogonia arranged such that pregranulosa cells formed the outer wall of the cords. Ovigerous cords were avascular, enveloped in a prominent basal lamina, open-ended where they interfaced with the ovarian surface epithelium, and formed a separate compartment whereby oogonia/oocytes were segregated from the surrounding stroma and vasculature until the time of follicular formation. The structural integrity of ovigerous cords was maintained through day 75, at which time primordial follicles (type 1 and type 1a) first emerged from the cords at the interface of the cortex and medulla. On the basis of the sequential structural changes that occurred during the differentiation and development of fetal ovaries and location of proliferating cells identified by the incorporation of BrdU, we conclude that the majority of the granulosa cells in primordial follicles are derived from mesothelial cells originating from the ovarian surface epithelium. In addition, from the cell-specific distribution and temporal pattern of expression of mRNAs for key steroidogenic enzymes we hypothesize that steroid hormones may play a pivotal paracrine/autocrine role in the formation and/or function of ovigerous cords as well as the development of the ovarian vascular network.

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The origin of follicle (i.e., pregranulosa) cells that become the somatic component of primordial follicles is obscure. In addition, information regarding the structural changes that accompany the concomitant regression of ovigerous cords and the appearance of primordial follicles is lacking. In the present study, ovine ovaries collected at frequent time intervals between Day 38 and Day 100 of fetal life were examined by light and electron microscopy. To gain new information regarding the origin of follicular cells, incorporation of 5-bromo-2'-deoxyuridine was used to identify proliferating cells at selected stages of development. Based on the location and identity of proliferating cells, apoptotic cells, and sequential changes in histoarchitecture, we hypothesize 1) that most (i.e., >95%) of the granulosal cells in newly formed primordial follicles originate from the ovarian surface epithelium; 2) that the sequential events leading to follicle formation take place entirely within ovigerous cords, with the first follicles forming at the interface of the cortex and medulla; and 3) that the loss (i.e., >75%) of germ cells, but not of somatic cells, within the ovigerous cords is a means by which each surviving oocyte gains additional pregranulosal cells before follicle formation. Conceptual models detailing the chronology of developmental events involved in the formation of primordial follicles in sheep are discussed.

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