Project description:While blood vessels have muscular walls that undergo tonic contractions to alter vascular resistance and, thus, control blood flow, lymphatics at the level of the collecting vessels and higher have muscular walls capable of rapid phasic contractions that generate lymph flow in addition to tonic contractions that regulate lymph flow resistance. While the ability of lymphatics to undergo rapid phasic contractions has been known for several centuries, the biological elements governing this phenomenon remain unknown. In an attempt to gain insight into the structural and regulatory elements that give lymphatic vessels their unique contractile capabilities, we utilized two-color microarray analysis to compare the thoracic duct of the rat to the vena cava of the same donor animal. Total cellular RNA was isolated immediately following vessel isolation and amplified in the presence of amino allyl dUTP. The resulting modified aRNA was conjugated to either Cy3 or Cy5 dye prior to hybridization to a rat 5.7K oligonucleotide array. Analysis and filtering of the data obtained from the microarray image yielded several contractile and regulatory genes with altered expression in the thoracic duct relative to the vena cava. Further evaluation of the data obtained in this study may aid in illustrating the unique properties of the lymphatic vessel and its muscular wall. Keywords: Thoracic duct, lymphatics, microarray Four unique thoracic duct/vena cava sample pairs were individually analyzed via two-color microarray analysis yielding 4 biological replicates. To minimize dye bias, a dye balance design was utilized in which the orientation of dye assignment was alternated between vessel pairs (i.e. two thoracic duct samples were labeled with Cy3 and two were labeled with Cy5). Prior to analysis, the data from 2 of the replicates was transformed to accomodate the dye balance such that all thoracic duct data is interpreted as Cy5 and all vena cava data is interpreted as Cy3.

Project description:A series of two color gene expression profiles obtained using Agilent 44K expression microarrays was used to examine sex-dependent and growth hormone-dependent differences in gene expression in rat liver. This series is comprised of pools of RNA prepared from untreated male and female rat liver, hypophysectomized (‘Hypox’) male and female rat liver, and from livers of Hypox male rats treated with either a single injection of growth hormone and then killed 30, 60, or 90 min later, or from livers of Hypox male rats treated with two growth hormone injections spaced 3 or 4 hr apart and killed 30 min after the second injection. The pools were paired to generate the following 6 direct microarray comparisons: 1) untreated male liver vs. untreated female liver; 2) Hypox male liver vs. untreated male liver; 3) Hypox female liver vs. untreated female liver; 4) Hypox male liver vs. Hypox female liver; 5) Hypox male liver + 1 growth hormone injection vs. Hypox male liver; and 6) Hypox male liver + 2 growth hormone injections vs. Hypox male liver. A comparison of untreated male liver and untreated female liver liver gene expression profiles showed that of the genes that showed significant expression differences in at least one of the 6 data sets, 25% were sex-specific. Moreover, sex specificity was lost for 88% of the male-specific genes and 94% of the female-specific genes following hypophysectomy. 25-31% of the sex-specific genes whose expression is altered by hypophysectomy responded to short-term growth hormone treatment in hypox male liver. 18-19% of the sex-specific genes whose expression decreased following hypophysectomy were up-regulated after either one or two growth hormone injections. Finally, growth hormone suppressed 24-36% of the sex-specific genes whose expression was up-regulated following hypophysectomy, indicating that growth hormone acts via both positive and negative regulatory mechanisms to establish and maintain the sex specificity of liver gene expression. For full details, see V. Wauthier and D.J. Waxman, Molecular Endocrinology (2008)

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Rattus norvegicus

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