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2 - Biology of preterm labour
- Edited by Jane Norman, University of Glasgow, Ian Greer, University of Glasgow
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- Book:
- Preterm Labour
- Published online:
- 07 August 2009
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- 18 August 2005, pp 26-75
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Summary
Introduction
The prevention of preterm labour remains one of the primary goals of obstetric research. To achieve this effectively, we need to understand the mechanisms regulating uterine contractility, cervical ripening and activation of the fetal membranes. Whether preterm labour represents an acceleration of the mechanisms involved in term labour remains controversial. Romero et al. (1997) propose that the fundamental difference between term and preterm labour is that the former results from physiological activation of the components of a common terminal pathway, while preterm labour results from disease processes activating one or more of the components of this pathway. In contrast, Challis et al. (2000) suggest that the causes of preterm labour may vary at different times during pregnancy and will not necessarily reflect acceleration of the processes occurring during labour at term. At present, the factors maintaining myometrial quiescence during pregnancy, and those that stimulate the onset of uterine contractions and cervical ripening at term remain obscure. Until these factors are elucidated, it seems unlikely that effective strategies for the treatment of preterm labour will be found (Goldenberg and Rouse 1998).
Myometrial contractions
The uterus is spontaneously active and, using electromyographic measurements, contractile activity can be detected in both pregnant and non-pregnant women (Morrison 1996). Two different types of electromyographic activity have been described in the myometrium of the pregnant rhesus monkey, referred to as contractures and contractions, and are believed to be present in most species (Nathanielsz et al. 1992).
A comparison between feeding systems (pasture and TMR) and the effect of vitamin E supplementation on plasma and milk fatty acid profiles in dairy cows
- Jane K Kay, John R Roche, Eric S Kolver, Norman A Thomson, Lance H Baumgard
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- Journal:
- Journal of Dairy Research / Volume 72 / Issue 3 / August 2005
- Published online by Cambridge University Press:
- 09 May 2005, pp. 322-332
- Print publication:
- August 2005
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Unidentified constituents in fresh pasture increase milk fat cis-9, trans-11 conjugated linoleic acid (CLA) concentration, and prevent milk fat depression, even though ruminal conditions conducive to reducing milk fat synthesis exist. One possible explanation is vitamin E (α-tocopherol), a constituent high in fresh pasture, but naturally low in conserved/dried forages and cereal grains. Twenty late-lactating dairy cows previously consuming a total mixed ration (TMR) were randomly allocated to one of two dietary treatments for 21 d: TMR (control; n=10); and TMR plus an additional 10000 i.u. α-tocopherol/d (VIT E; n=10). These cows were simultaneously compared with 13 late-lactation dairy cows previously grazing fresh pasture (PAS) balanced for age, parity and genetic merit. Average daily α-tocopherol intakes were approximately 468, 10520 and 1590 i.u./cow for the control, VIT E and PAS treatments, respectively. Dietary α-tocopherol supplementation (VIT E v. control) slightly increased milk fat content by 0·23 percentage units, but did not significantly alter milk fatty acid composition. Plasma trans-11 18[ratio ]1 (VA) content tended to increase and trans-10 18[ratio ]1 levels numerically declined following α-tocopherol supplementation suggesting possible changes in rumen biohydrogenation products. In addition, increased α-tocopherol intake in TMR-fed cows decreased serum urea levels and tended to alter milk fat 15[ratio ]0 suggesting changes in rumen microbial populations. However, when compared with cows grazing pasture, TMR-fed cows supplemented with α-tocopherol, still produced milk with lower cis-9, trans-11 CLA and VA, and higher trans-10 18[ratio ]1 concentrations suggesting α-tocopherol is not a primary reason for milk fatty acid profile differences between pasture and TMR-fed cows. Therefore, additional unknown pasture constituents favour production of fatty acids originating from the cis-9, trans-11 instead of the trans-10, cis-12 CLA biohydrogenation pathways.
Looking Backward, Looking Forward: MLA Members Speak
- April Alliston, Elizabeth Ammons, Jean Arnold, Nina Baym, Sandra L. Beckett, Peter G. Beidler, Roger A. Berger, Sandra Bermann, J.J. Wilson, Troy Boone, Alison Booth, Wayne C. Booth, James Phelan, Marie Borroff, Ihab Hassan, Ulrich Weisstein, Zack Bowen, Jill Campbell, Dan Campion, Jay Caplan, Maurice Charney, Beverly Lyon Clark, Robert A. Colby, Thomas C. Coleman III, Nicole Cooley, Richard Dellamora, Morris Dickstein, Terrell Dixon, Emory Elliott, Caryl Emerson, Ann W. Engar, Lars Engle, Kai Hammermeister, N. N. Feltes, Mary Anne Ferguson, Annie Finch, Shelley Fisher Fishkin, Jerry Aline Flieger, Norman Friedman, Rosemarie Garland-Thomson, Sandra M. Gilbert, Laurie Grobman, George Guida, Liselotte Gumpel, R. K. Gupta, Florence Howe, Cathy L. Jrade, Richard A. Kaye, Calhoun Winton, Murray Krieger, Robert Langbaum, Richard A. Lanham, Marilee Lindemann, Paul Michael Lützeler, Thomas J. Lynn, Juliet Flower MacCannell, Michelle A. Massé, Irving Massey, Georges May, Christian W. Hallstein, Gita May, Lucy McDiarmid, Ellen Messer-Davidow, Koritha Mitchell, Robin Smiles, Kenyatta Albeny, George Monteiro, Joel Myerson, Alan Nadel, Ashton Nichols, Jeffrey Nishimura, Neal Oxenhandler, David Palumbo-Liu, Vincent P. Pecora, David Porter, Nancy Potter, Ronald C. Rosbottom, Elias L. Rivers, Gerhard F. Strasser, J. L. Styan, Marianna De Marco Torgovnick, Gary Totten, David van Leer, Asha Varadharajan, Orrin N. C. Wang, Sharon Willis, Louise E. Wright, Donald A. Yates, Takayuki Yokota-Murakami, Richard E. Zeikowitz, Angelika Bammer, Dale Bauer, Karl Beckson, Betsy A. Bowen, Stacey Donohue, Sheila Emerson, Gwendolyn Audrey Foster, Jay L. Halio, Karl Kroeber, Terence Hawkes, William B. Hunter, Mary Jambus, Willard F. King, Nancy K. Miller, Jody Norton, Ann Pellegrini, S. P. Rosenbaum, Lorie Roth, Robert Scholes, Joanne Shattock, Rosemary T. VanArsdel, Alfred Bendixen, Alarma Kathleen Brown, Michael J. Kiskis, Debra A. Castillo, Rey Chow, John F. Crossen, Robert F. Fleissner, Regenia Gagnier, Nicholas Howe, M. Thomas Inge, Frank Mehring, Hyungji Park, Jahan Ramazani, Kenneth M. Roemer, Deborah D. Rogers, A. LaVonne Brown Ruoff, Regina M. Schwartz, John T. Shawcross, Brenda R. Silver, Andrew von Hendy, Virginia Wright Wexman, Britta Zangen, A. Owen Aldridge, Paula R. Backscheider, Roland Bartel, E. M. Forster, Milton Birnbaum, Jonathan Bishop, Crystal Downing, Frank H. Ellis, Roberto Forns-Broggi, James R. Giles, Mary E. Giles, Susan Blair Green, Madelyn Gutwirth, Constance B. Hieatt, Titi Adepitan, Edgar C. Knowlton, Jr., Emanuel Mussman, Sally Todd Nelson, Robert O. Preyer, David Diego Rodriguez, Guy Stern, James Thorpe, Robert J. Wilson, Rebecca S. Beal, Joyce Simutis, Betsy Bowden, Sara Cooper, Wheeler Winston Dixon, Tarek el Ariss, Richard Jewell, John W. Kronik, Wendy Martin, Stuart Y. McDougal, Hugo Méndez-Ramírez, Ivy Schweitzer, Armand E. Singer, G. Thomas Tanselle, Tom Bishop, Mary Ann Caws, Marcel Gutwirth, Christophe Ippolito, Lawrence D. Kritzman, James Longenbach, Tim McCracken, Wolfe S. Molitor, Diane Quantic, Gregory Rabassa, Ellen M. Tsagaris, Anthony C. Yu, Betty Jean Craige, Wendell V. Harris, J. Hillis Miller, Jesse G. Swan, Helene Zimmer-Loew, Peter Berek, James Chandler, Hanna K. Charney, Philip Cohen, Judith Fetterley, Herbert Lindenberger, Julia Reinhard Lupton, Maximillian E. Novak, Richard Ohmann, Marjorie Perloff, Mark Reynolds, James Sledd, Harriet Turner, Marie Umeh, Flavia Aloya, Regina Barreca, Konrad Bieber, Ellis Hanson, William J. Hyde, Holly A. Laird, David Leverenz, Allen Michie, J. Wesley Miller, Marvin Rosenberg, Daniel R. Schwarz, Elizabeth Welt Trahan, Jean Fagan Yellin
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- Journal:
- PMLA / Publications of the Modern Language Association of America / Volume 115 / Issue 7 / December 2000
- Published online by Cambridge University Press:
- 23 October 2020, pp. 1986-2078
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- December 2000
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Seasonal and lactational influences on bovine milk composition in New Zealand
- MARTIN J. AULDIST, BRIAN J. WALSH, NORMAN A. THOMSON
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- Journal:
- Journal of Dairy Research / Volume 65 / Issue 3 / August 1998
- Published online by Cambridge University Press:
- 01 August 1998, pp. 401-411
- Print publication:
- August 1998
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This study was designed to evaluate the respective influences of stage of lactation (SOL) and time of year on the seasonal variation in milk composition for pasture-fed dairy cows in New Zealand. Four herds of ∼20 Friesian cows were used, one herd calving in a 6 week period beginning in each of January, April, July and October. Cows grazed rye-grass–white clover pasture only, except during June when all cows received supplementary pasture silage. Milk samples were collected from each cow in milk on four occasions during the year (September, December, March and June), to give a total of three samples per cow (early, mid and late lactation; about 30, 120 and 210 d respectively after calving). Samples were analysed for a detailed range of components. Concentrations of many milk components (e.g. total protein, fat, casein and whey protein) increased as lactation progressed; the extent of these increases depended on the time of year. These results indicated that spreading calving throughout the year would lessen seasonal variations in the gross composition of milk supplied to factories, leading to a more even distribution of product yield across the year. Despite this, variations in some important manufacturing properties were affected by time of year but not by SOL. Ratios of protein[ratio ]fat and casein: whey protein were not significantly affected by SOL, but were affected by time of year. The solid fat content of milk was also affected by time of year. Seasonal variations in the manufacturing properties of milk may be reduced but not eliminated by changing the time of calving.