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Tanke NT, Liu Z, Gore MT, Bougaran P, Linares MB, Marvin A, Sharma A, Oatley M, Yu T, Quigley K, Vest S, Cook JG, Bautch VL. Endothelial Cell Flow-Mediated Quiescence Is Temporally Regulated and Utilizes the Cell Cycle Inhibitor p27. Arterioscler Thromb Vasc Biol 2024; 44:1265-1282. [PMID: 38602102 DOI: 10.1161/atvbaha.124.320671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Accepted: 03/27/2024] [Indexed: 04/12/2024]
Abstract
BACKGROUND Endothelial cells regulate their cell cycle as blood vessels remodel and transition to quiescence downstream of blood flow-induced mechanotransduction. Laminar blood flow leads to quiescence, but how flow-mediated quiescence is established and maintained is poorly understood. METHODS Primary human endothelial cells were exposed to laminar flow regimens and gene expression manipulations, and quiescence depth was analyzed via time-to-cell cycle reentry after flow cessation. Mouse and zebrafish endothelial expression patterns were examined via scRNA-seq (single-cell RNA sequencing) analysis, and mutant or morphant fish lacking p27 were analyzed for endothelial cell cycle regulation and in vivo cellular behaviors. RESULTS Arterial flow-exposed endothelial cells had a distinct transcriptome, and they first entered a deep quiescence, then transitioned to shallow quiescence under homeostatic maintenance conditions. In contrast, venous flow-exposed endothelial cells entered deep quiescence early that did not change with homeostasis. The cell cycle inhibitor p27 (CDKN1B) was required to establish endothelial flow-mediated quiescence, and expression levels positively correlated with quiescence depth. p27 loss in vivo led to endothelial cell cycle upregulation and ectopic sprouting, consistent with loss of quiescence. HES1 and ID3, transcriptional repressors of p27 upregulated by arterial flow, were required for quiescence depth changes and the reduced p27 levels associated with shallow quiescence. CONCLUSIONS Endothelial cell flow-mediated quiescence has unique properties and temporal regulation of quiescence depth that depends on the flow stimulus. These findings are consistent with a model whereby flow-mediated endothelial cell quiescence depth is temporally regulated downstream of p27 transcriptional regulation by HES1 and ID3. The findings are important in understanding endothelial cell quiescence misregulation that leads to vascular dysfunction and disease.
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Affiliation(s)
- Natalie T Tanke
- Curriculum in Cell Biology and Physiology (N.T.T., V.L.B.), The University of North Carolina at Chapel Hill
| | - Ziqing Liu
- Department of Biology (Z.L., M.T.G., P.B., M.B.L., A.M., A.S., M.O., T.Y., K.Q., S.V., V.L.B.), The University of North Carolina at Chapel Hill
| | - Michaelanthony T Gore
- Department of Biology (Z.L., M.T.G., P.B., M.B.L., A.M., A.S., M.O., T.Y., K.Q., S.V., V.L.B.), The University of North Carolina at Chapel Hill
| | - Pauline Bougaran
- Department of Biology (Z.L., M.T.G., P.B., M.B.L., A.M., A.S., M.O., T.Y., K.Q., S.V., V.L.B.), The University of North Carolina at Chapel Hill
| | - Mary B Linares
- Department of Biology (Z.L., M.T.G., P.B., M.B.L., A.M., A.S., M.O., T.Y., K.Q., S.V., V.L.B.), The University of North Carolina at Chapel Hill
| | - Allison Marvin
- Department of Biology (Z.L., M.T.G., P.B., M.B.L., A.M., A.S., M.O., T.Y., K.Q., S.V., V.L.B.), The University of North Carolina at Chapel Hill
| | - Arya Sharma
- Department of Biology (Z.L., M.T.G., P.B., M.B.L., A.M., A.S., M.O., T.Y., K.Q., S.V., V.L.B.), The University of North Carolina at Chapel Hill
| | - Morgan Oatley
- Department of Biology (Z.L., M.T.G., P.B., M.B.L., A.M., A.S., M.O., T.Y., K.Q., S.V., V.L.B.), The University of North Carolina at Chapel Hill
| | - Tianji Yu
- Department of Biology (Z.L., M.T.G., P.B., M.B.L., A.M., A.S., M.O., T.Y., K.Q., S.V., V.L.B.), The University of North Carolina at Chapel Hill
| | - Kaitlyn Quigley
- Department of Biology (Z.L., M.T.G., P.B., M.B.L., A.M., A.S., M.O., T.Y., K.Q., S.V., V.L.B.), The University of North Carolina at Chapel Hill
| | - Sarah Vest
- Department of Biology (Z.L., M.T.G., P.B., M.B.L., A.M., A.S., M.O., T.Y., K.Q., S.V., V.L.B.), The University of North Carolina at Chapel Hill
| | - Jeanette Gowen Cook
- Department of Biochemistry and Biophysics (J.G.C.), The University of North Carolina at Chapel Hill
| | - Victoria L Bautch
- Curriculum in Cell Biology and Physiology (N.T.T., V.L.B.), The University of North Carolina at Chapel Hill
- Department of Biology (Z.L., M.T.G., P.B., M.B.L., A.M., A.S., M.O., T.Y., K.Q., S.V., V.L.B.), The University of North Carolina at Chapel Hill
- McAllister Heart Institute (V.L.B.), The University of North Carolina at Chapel Hill
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Kinghorn K, Gill A, Marvin A, Li R, Quigley K, Singh S, Gore MT, le Noble F, Gabhann FM, Bautch VL. A defined clathrin-mediated trafficking pathway regulates sFLT1/VEGFR1 secretion from endothelial cells. Angiogenesis 2024; 27:67-89. [PMID: 37695358 PMCID: PMC10881643 DOI: 10.1007/s10456-023-09893-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Accepted: 08/07/2023] [Indexed: 09/12/2023]
Abstract
FLT1/VEGFR1 negatively regulates VEGF-A signaling and is required for proper vessel morphogenesis during vascular development and vessel homeostasis. Although a soluble isoform, sFLT1, is often mis-regulated in disease and aging, how sFLT1 is trafficked and secreted from endothelial cells is not well understood. Here we define requirements for constitutive sFLT1 trafficking and secretion in endothelial cells from the Golgi to the plasma membrane, and we show that sFLT1 secretion requires clathrin at or near the Golgi. Perturbations that affect sFLT1 trafficking blunted endothelial cell secretion and promoted intracellular mis-localization in cells and zebrafish embryos. siRNA-mediated depletion of specific trafficking components revealed requirements for RAB27A, VAMP3, and STX3 for post-Golgi vesicle trafficking and sFLT1 secretion, while STX6, ARF1, and AP1 were required at the Golgi. Live-imaging of temporally controlled sFLT1 release from the endoplasmic reticulum showed clathrin-dependent sFLT1 trafficking at the Golgi into secretory vesicles that then trafficked to the plasma membrane. Depletion of STX6 altered vessel sprouting in 3D, suggesting that endothelial cell sFLT1 secretion influences proper vessel sprouting. Thus, specific trafficking components provide a secretory path from the Golgi to the plasma membrane for sFLT1 in endothelial cells that utilizes a specialized clathrin-dependent intermediate, suggesting novel therapeutic targets.
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Affiliation(s)
- Karina Kinghorn
- Curriculum in Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC, USA
| | - Amy Gill
- Department of Biomedical Engineering, Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Allison Marvin
- Department of Biology, The University of North Carolina at Chapel Hill, CB No. 3280, Chapel Hill, NC, 27599, USA
| | - Renee Li
- Department of Biology, The University of North Carolina at Chapel Hill, CB No. 3280, Chapel Hill, NC, 27599, USA
| | - Kaitlyn Quigley
- Department of Biology, The University of North Carolina at Chapel Hill, CB No. 3280, Chapel Hill, NC, 27599, USA
| | - Simcha Singh
- Department of Biology, The University of North Carolina at Chapel Hill, CB No. 3280, Chapel Hill, NC, 27599, USA
| | - Michaelanthony T Gore
- Department of Biology, The University of North Carolina at Chapel Hill, CB No. 3280, Chapel Hill, NC, 27599, USA
| | - Ferdinand le Noble
- Department of Cell and Developmental Biology, Institute of Zoology, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Feilim Mac Gabhann
- Department of Biomedical Engineering, Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Victoria L Bautch
- Curriculum in Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC, USA.
- Department of Biology, The University of North Carolina at Chapel Hill, CB No. 3280, Chapel Hill, NC, 27599, USA.
- McAllister Heart Institute, University of North Carolina, Chapel Hill, NC, USA.
- UNC Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, USA.
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Tanke NT, Liu Z, Gore MT, Bougaran P, Linares MB, Marvin A, Sharma A, Oatley M, Yu T, Quigley K, Vest S, Cook JG, Bautch VL. Endothelial cell flow-mediated quiescence is temporally regulated and utilizes the cell cycle inhibitor p27. bioRxiv 2024:2023.06.09.544403. [PMID: 37662222 PMCID: PMC10473767 DOI: 10.1101/2023.06.09.544403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
Background Endothelial cells regulate their cell cycle as blood vessels remodel and transition to quiescence downstream of blood flow-induced mechanotransduction. Laminar blood flow leads to quiescence, but how flow-mediated quiescence is established and maintained is poorly understood. Methods Primary human endothelial cells were exposed to laminar flow regimens and gene expression manipulations, and quiescence depth was analyzed via time to cell cycle re-entry after flow cessation. Mouse and zebrafish endothelial expression patterns were examined via scRNA seq analysis, and mutant or morphant fish lacking p27 were analyzed for endothelial cell cycle regulation and in vivo cellular behaviors. Results Arterial flow-exposed endothelial cells had a distinct transcriptome, and they first entered a deep quiescence, then transitioned to shallow quiescence under homeostatic maintenance conditions. In contrast, venous-flow exposed endothelial cells entered deep quiescence early that did not change with homeostasis. The cell cycle inhibitor p27 (CDKN1B) was required to establish endothelial flow-mediated quiescence, and expression levels positively correlated with quiescence depth. p27 loss in vivo led to endothelial cell cycle upregulation and ectopic sprouting, consistent with loss of quiescence. HES1 and ID3, transcriptional repressors of p27 upregulated by arterial flow, were required for quiescence depth changes and the reduced p27 levels associated with shallow quiescence. Conclusions Endothelial cell flow-mediated quiescence has unique properties and temporal regulation of quiescence depth that depends on the flow stimulus. These findings are consistent with a model whereby flow-mediated endothelial cell quiescence depth is temporally regulated downstream of p27 transcriptional regulation by HES1 and ID3. The findings are important in understanding endothelial cell quiescence mis-regulation that leads to vascular dysfunction and disease.
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Affiliation(s)
- Natalie T Tanke
- Curriculum in Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Ziqing Liu
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Michaelanthony T Gore
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Pauline Bougaran
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Mary B Linares
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Allison Marvin
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Arya Sharma
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Morgan Oatley
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Tianji Yu
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Kaitlyn Quigley
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Sarah Vest
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Jeanette Gowen Cook
- Department of Biochemistry and Biophysics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Victoria L Bautch
- Curriculum in Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- McAllister Heart Institute, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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Abstract
The effect of an acute bout of exhaustive exercise on hepatic fatty acid synthase (FAS) gene expression was examined in rats. Female Sprague-Dawley rats (age 8 wk) were fasted for 48 h (F, n = 6), or fasted, refed a high-fructose diet for 6 h, and killed at rest (R, n = 6) or killed after running on a treadmill at 27 m/min and 5% grade for 88 +/- 7 min (E, n = 6). Gel mobility shift assay indicated that R rats had twofold higher liver nuclear protein binding to oligonucleotides corresponding to the insulin responsive sequence (-71/-50) and carbohydrate response element (+283/+303) on the FAS promoter, compared with F rats. Exercise severely attenuated this binding in liver nuclear extracts to the levels seen in F rats. Competition and supershift experiments revealed that the bound protein complexes contained the upstream stimulatory factors. Nuclear run-on experiment revealed a 49-fold increase in transcription rate of the FAS gene in R vs. F rats, whereas exercise suppressed the transcription rate. FAS mRNA abundance and FAS enzyme activity were dramatically increased with refeeding but were unaltered by exercise. The results reveal that dietary induction of hepatic FAS is stimulated by increased nuclear protein binding to insulin responsive sequence and carbohydrate response element, whereas exhaustive exercise attenuates the binding, which may precede downregulation of FAS mRNA and enzyme synthesis reported in our previous work (M. A. Griffiths, R. Fiebig, M. T. Gore, D. H. Baker, K. Esser, L. Oscai, and L. L. Ji. J. Nutr. 126, 1959-1971, 1996).
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Affiliation(s)
- R Fiebig
- Biodynamics Laboratory and Interdepartmental Program of Nutritional Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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Fiebig R, Griffiths MA, Gore MT, Baker DH, Oscai L, Ney DM, Ji LL. Exercise training down-regulates hepatic lipogenic enzymes in meal-fed rats: fructose versus complex-carbohydrate diets. J Nutr 1998; 128:810-7. [PMID: 9566986 DOI: 10.1093/jn/128.5.810] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The maximal activity and mRNA abundance of hepatic fatty acid synthase (FAS) and other lipogenic enzymes were investigated in rats meal-fed either a high fructose (F) or a high cornstarch (C) diet. The diet contained 50% F or C (g/100 g), casein (20%), cornstarch (16.13%), corn oil (5%), minerals (5.37%), vitamins (1%) and Solka-floc (2%). Female Sprague-Dawley rats (n = 44) were randomly divided into C or F groups that were meal-fed for 3 h/d; each group was subdivided into exercise-trained (T) and untrained (U) groups. Treadmill training was performed 4 h after the initiation of the meal at 25 m/min, 10% grade for 2 h/d, 5 d/wk, for 10 wk. Rats were killed 9 h after the meal and 27 h after the last training session. F-fed rats had significantly higher activities of all lipogenic enzymes assayed and mRNA abundance of FAS and acetyl-coenzyme A carboxylase (ACC) than C rats (P < 0.05). Concentrations of plasma insulin and glucose and liver pyruvate were not altered by F feeding. Proportions of the fatty acids 18:2 and 20:4 were lower, whereas those of 16:0 and 16:1 were higher, in livers of F than of C rats (P < 0.05). Training decreased FAS activity by 50% (P < 0.05), without affecting FAS mRNA level in C rats; this down-regulation was absent in the F rats. ACC mRNA abundance tended to be lower in CT than in CU rats (P < 0.075). L-Type pyruvate kinase activity was lower in FT than in FU rats (P < 0.05), whereas other lipogenic enzyme activities did not differ between T and U rats of each diet group. We conclude that hepatic lipogenic enzyme induction by high carbohydrate meal feeding may be inhibited by exercise training and that a fructose-rich diet may attenuate this training-induced down-regulation.
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Affiliation(s)
- R Fiebig
- Departments of Kinesiology and Nutritional Sciences, University of Wisconsin-Madison, Madison, WI, USA
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Griffiths MA, Fiebig R, Gore MT, Baker DH, Esser K, Oscai L, Ji LL. Exercise down-regulates hepatic lipogenic enzymes in food-deprived and refed rats. J Nutr 1996; 126:1959-71. [PMID: 8759368 DOI: 10.1093/jn/126.8.1959] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The effects of an acute bout of prolonged exercise on the activities of several hepatic lipogenic enzymes and the abundance of fatty acid synthase (FAS) mRNA were evaluated using a food deprivation-refeeding protocol in which diets contained 50% of the energy from either fructose or cornstarch. Food was withheld from male rats for 48 h and refed for 0, 4, 8, 12, 24 or 48 h. At each time point, half of each dietary group was subjected to a single bout of treadmill running until exhaustion and killed immediately. The other half of each group rested without food for the same amount of time before being killed. Exercise significantly decreased FAS activity by 57, 46, 10, 26 and 70% at 4, 8, 12, 24 and 48 h of refeeding, respectively, in the fructose-fed rats; and by 70 and 63% at 24 and 48 h of refeeding, respectively, in the cornstarch-fed rats. Activities of L-type pyruvate kinase and glucose 6-phosphate dehydrogenase were significantly decreased after exercise in the fructose-fed, but not cornstarch-fed rats. In rested rats, FAS mRNA abundance increased approximately fourfold above the unfed levels after 8 and 12 h of refeeding. Exercise attenuated the diet-induced increases in FAS mRNA abundance. At 8 h of refeeding, both cornstarch- and fructose-fed exercised rats had 71% (P < 0.05) of the FAS mRNA levels of their rested counterparts; at 12 h, these exercised rats showed only 46 and 27% (P < 0.05) of FAS mRNA levels compared with rested rats fed the same diet. We conclude that dietary induction of FAS activity and mRNA abundance can be inhibited by prolonged exercise, suggesting that exercise may influence FAS transcription and/or mRNA stability.
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Affiliation(s)
- M A Griffiths
- Department of Kinesiology, University of Illinois at Urbana-Champaign, USA
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Gore MT, Young RB, Bird CR, Rahe CH, Marple DN, Griffin JL, Mulvaney DR. Myosin heavy chain gene expression in bovine fetuses and neonates representing genotypes with contrasting patterns of growth. Proc Soc Exp Biol Med 1995; 209:86-91. [PMID: 7724620 DOI: 10.3181/00379727-209-43882] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Fetal and neonatal myosin heavy chain (MHC) gene expression was examined in bovine genotypes that differed in their postnatal growth pattern and mature size. Pregnancies were established that would be expected to produce early-, intermediate-, or late-maturing postnatal growth. Fetal skeletal and cardiac muscles were collected at 100 and 200 days of gestation and at 30 days of age. Muscle tissue was analyzed for relative levels of MHC RNA and protein. Longissimus muscle MHC RNA/microgram RNA was greater at the 100-day time point for the intermediate maturity type (P < 0.05), which differed from the 200-day time point where the early maturity type had the greater RNA level (P < 0.05). Triceps muscle MHC RNA/microgram RNA weights differed due to genotype at 200 days gestation but did not differ at 100 days gestation or at 30 days postnatal. Ventricular muscle MHC RNA did not differ due to genotype at any of the three developmental stages. Differences due to maturity type in MHC protein/mg DNA were observed at 30 days of age, but no differences due to maturity type were observed at the prenatal time points. These results indicate that bovine fetal skeletal muscle MHC RNA production can be influenced by genotype and that genotype may be an important factor for future studies examining the role of external influences on fetal muscle growth.
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Affiliation(s)
- M T Gore
- Department of Animal and Dairy Sciences, Auburn University, Alabama 36849, USA
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Gore MT, Young RB, Claeys MC, Chromiak JA, Rahe CH, Marple DN, Hough JD, Griffin JL, Mulvaney DR. Growth and development of bovine fetuses and neonates representing three genotypes. J Anim Sci 1994; 72:2307-18. [PMID: 7528193 DOI: 10.2527/1994.7292307x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Growth was examined in bovine fetuses and neonates that typically differ in mature size and postnatal developmental pattern. Pregnancies were established from matings expected to produce early (E), late (L), and intermediate (I) maturing postnatal growth patterns. Tissues were collected at 100 and 200 d of gestation and 30 d postnatal. Muscle:body weight ratios were lower at 100 and 200 d for the E maturity type than for the L maturity type (P < .05). This differs from observations of muscle:body weight ratios made at 30 d postnatal, at which time ratios for E were either greater than (triceps brachii, P < .05) or similar to those for L. Few differences due to maturity type were observed at 100 d for bone weight:body weight ratios; however, at 200 d of gestation E bone weight:body weight ratios were generally lower (P < .05) than those for L. The genotypic relationship for bone weight:body weight ratio at 30 d postnatal was similar to that observed at 200 d of gestation. Observations of organ weight:body weight ratios revealed no clear patterns due to maturity type. The genotypic relationship for total muscle DNA content was similar to that observed for muscle weight. These results indicate that fetal muscle development differs in cattle that have different postnatal growth patterns by as early as 100 d of gestation and that differences in fetal muscle growth are related to differences in muscle hyperplasia.
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Affiliation(s)
- M T Gore
- Department of Animal and Dairy Sciences, Auburn University, AL 36849
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Claeys MC, Mulvaney DR, McCarthy FD, Gore MT, Marple DN, Sartin JL. Skeletal muscle protein synthesis and growth hormone secretion in young lambs treated with clenbuterol. J Anim Sci 1989; 67:2245-54. [PMID: 2599974 DOI: 10.2527/jas1989.6792245x] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
To determine effects of clenbuterol (CB) on muscle protein turnover and growth hormone (GH) secretion, 16 crossbred wether lambs (14.4 kg) were randomized into two groups designated to receive daily oral boluses of gelatin capsules containing corn starch with either 0 (control, CTL) or 1.87 mg/kg body weight CB for either 14 (n = 8) or 28 d (n = 8). This calculates to be approximately 40 mg CB/kg diet. Lambs had ad libitum access to a 16% crude protein corn-soy diet and feed consumption (FC) was measured. After 14 and 28 d, lambs were slaughtered and semitendinosus (ST), longissimus (LD) and brachialis (BR) muscles were exercised, weighed and analyzed for protein (TP) content. For 6 h prior to slaughter of 28-d lambs, 2.5 microCi L-[U-14C]tyrosine/kg was infused intravenously, blood was sampled and plasma was analyzed for specific radioactivity of tyrosine. Plasma GH concentrations were assessed by radioimmunoassay. No differences due to treatment were found in FC, rate of gain or GH concentrations. Semitendinosus and BR weights of control lambs at 14 d did not differ between treatments. At 28 d, ST and BR weights of control lambs (58.8 and 18.5 g, respectively) were less (P less than .10) than those of lambs treated with CB (74.3 and 23.1 g, respectively). The TP per ST and BR at 28 d for control lambs was 71.5 and 85.1% (P less than .10) that of muscles of lambs treated with CB. Fractional protein synthesis rates (FSR) of the BR (9.4 vs 6.1%/d) and total protein synthesized in ST muscle per day (1.4 vs .8 g) were elevated (P less than .10) in lambs treated with CB compared to controls. These data suggest that the increased fractional accretion rate observed in lambs treated with CB for 28 d was caused by increased FSR.
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Abstract
Ninety-three intensively managed, mature ewes were followed through three lactations to study effects and interrelationships of postweaning fast, prophylactic antibiotic injection, number of lactations and breed on subclinical mastitis, milk production and milk composition. Animals used in a 2 x 2 factorial design were allotted to treatment combinations of 1) postweaning 72 h fast or no fast, and 2) 1 x 10(6) units of procaine penicillin or sham i.m. injection at weaning. Treatments were implemented at weaning in yr 1; each ewe received the same treatment in each of the subsequent 2 yr of the study. Breeds included Finnish Landrace (F), Dorset (D), Rambouillet (R), Finnish Landrace x Dorset (FD) and Barbados Blackbelly x Dorset (BD). Milk production was greatest for D, followed by BD, FD, R and F during yr 1 (P less than .01) and overall (P less than .05). Milk production data were not collected in yr 2, but similar results were obtained in yr 3, except that the R and F exchanged rank positions. Milk composition was affected by breed. Breeds differed (P less than .05) in percentage lactose, fat and total nonfat solids in yr 1 and differed (P less than .01) in percentage lactose, fat, solids and protein across the 2 yr. A breed difference (P less than .05) was observed for incidence of mastitis at 3 wk postpartum and at weaning. Milk production was negatively correlated with incidence of mastitis (r = -.22, P less than .05). Milk production was improved (P less than .05) by a 72-h postweaning fast.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- F D McCarthy
- Virginia Polytechnic Institute and State University, Blacksburg 24061
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