Growth and Muscle Production

Transcription

1 Growth and Muscle Production The goal of these lectures is to discuss basic physiology associated with the control of growth and muscle production. 32 The sections for this lecture are: Animal growth and animal development Muscle: structure, myogenesis, growth Notes on whole-body growth Notes on hormonal regulation of growth Life is a series of chemical reactions occurring in compartmentalized environments. The main purpose of life is to keep itself alive Physiology, the study of how life works, is based on the simultaneous occurrence of the following three concepts: levels of organization structure / function relationship homeostatic regulation Growth & Muscle Development Growth, general and normal expansion of size as produced by accretion of tissues similar in constitution to that of original tissue or organ Hypertrophy, cells increase in size Hyperplasia, cells increase in number Accretion, cells accumulate or secrete True growth, e.g. increase in muscle/bone Fattening, accumulation of fat 1950 Whole body growth, from cell changes up Development, temporal collective changes today Muscle Production involve homeostatic responses leading to a steady state that is borderline to a pathological state (thus they are more susceptible to diseases). 1

2 Human Growth & Development Mother & son. At 8-foot-4, Leonid Stadnik, 33 years old, is the tallest human being on the planet (2005) Arnold Schwarzenegger. He won several world bodybuilders competitions and until recently was the governor of California. Average daily gain, or the daily increase in weight, is a direct reflection of the human and farm animal s ability to grow. Muscle growth, a main tissue that increased its weight, does so by multiple reasons, ultimately affecting undifferentiated muscle cells. Animal Growth & Development Average daily gain, or the daily increase in weight, is a direct reflection of the human and farm animal s ability to grow. Muscle growth, a main tissue that increased its weight, does so by multiple reasons, ultimately affecting undifferentiated muscle cells. 2

3 Animal Growth & Development Market Hog Performance 1950 today Animal Growth & Development 1950 today The economic contribution of meat animal production in the USA is significant (approx. 40% of total farm income). Therefore, Implementation of animal technologies that may improve animal performance can mean the difference between operational success and failure. For example Paylean (ractopamine a ß agonist) is a compound added to swine diets to improve efficiency. It stimulates growth in some tissues and blunt growth in others. Its use require changes in type / amount of dietary proteins provided to maximize the benefits. 3

4 Animal Growth & Development how to get from here to here today Muscle tissue has relatively large cells harnessed in a vast network of connective tissue (epimysium, fasciculi, perimysium, primary bundle, scondary bundle, intramuscular fat or marbling, endomysium, sarcolemma). 4

5 Muscle tissue has relatively large cells harnessed in a vast network of connective tissue (epimysium, fasciculi, perimysium, primary bundle, scondary bundle, intramuscular fat or marbling, endomysium, sarcolemma). Selected Myofibrillar and Other Cytoskeletal Proteins Located in Muscle Fibers Muscle tissue has relatively large cells harnessed in a vast network of connective tissue (epimysium, fasciculi, perimysium, primary bundle, scondary bundle, intramuscular fat or marbling, endomysium, sarcolemma). 5

6 Approximate Composition of Mammalian (percent fresh weight basis). Muscle tissue has relatively large cells harnessed in a vast network of connective tissue (epimysium, fasciculi, perimysium, primary bundle, scondary bundle, intramuscular fat or marbling, endomysium, sarcolemma). DO YOU SEE A PROBLEM? Multinucleated units like skeletal muscle cells are incapable of undergoing division. Myoblasts or muscle cell precursors are responsible for increasing muscle mass. In the G1-phase of the cell cycle, myoblast are sensitive to growth factors and steroids. 6

7 Multinucleated units like skeletal muscle cells are incapable of undergoing division. Myoblasts or muscle cell precursors are responsible for increasing muscle mass. In the G1-phase of the cell cycle, myoblast are sensitive to growth factors and steroids. Satellite cells are quiscent or dormants since they remain capable of re-entering the proliferative cell cycle without dividing. They are the apparent target for growth promotants used in adult animals, such as ßagonists, GH, IGF, steroids. 7

8 Satellite cells, located between the sarcolemma and the basal lamina, are activated to proliferate and ultimately fuse with each other to form new muscle fibers. This rarely occcurs normally in adults, but might be the site of action of some growth promotants. Satellite Cells Satellite cells, located between the sarcolemma and the basal lamina, are activated to proliferate and ultimately fuse with each other to form new muscle fibers. This rarely occcurs normally in adults, but might be the site of action of some growth promotants. 8

9 Satellite Cells quiscent satellite cell daugther cell returning to quiscence fusion with pre-existent microtubes activated myoblasts proliferating myoblasts myoblasts commited to myogenic linage myoblasts fusion into new myotubes and new myofibers Satellite cells, located between the sarcolemma and the basal lamina, are activated to proliferate and ultimately fuse with each other to form new muscle fibers. This rarely occcurs normally in adults, but might be the site of action of some growth promotants. Satellite Cell (SC) SC quiescent SC SC activated proliferatingg SC commited to myogenic linage SC fusion into myotubes SC maturation into myofibers Satellite cells, located between the sarcolemma and the basal lamina, are activated to proliferate and ultimately fuse with each other to form new muscle fibers. This rarely occcurs normally in adults, but might be the site of action of some growth promotants. 9

10 Satellite Cells Factor Proliferation Differentiation Migration E2 increase FGF increase decrease equivocal Ghrelin decrease increase HGF increase decrease increase IGF-I increase increase IGF-II increase increase IL-6 increase IL-15 increase increase Satellite cells, located between the sarcolemma and the basal lamina, are activated to proliferate and ultimately fuse with each other to form new muscle fibers. This rarely occcurs normally in adults, but might be the site of action of some growth promotants. Satellite Cells Factor Proliferation Differentiation Migration Leptin increase decrease LIF increase increase Myostatin decrease decrease PDGF increase increase T increase TGF-beta equivocal equivocal increase TNF equivocal decrease VEGF increase increase increase Satellite cells, located between the sarcolemma and the basal lamina, are activated to proliferate and ultimately fuse with each other to form new muscle fibers. This rarely occcurs normally in adults, but might be the site of action of some growth promotants. 10

11 control fiber # feed restricted Percentage (%) Tissue weight water muscle fat fat bone protein ash Average daily gain, or the daily increase in weight, is a diret reflection of the animal s 11

12 Whole Body Animal Growth Characteristics Red of Muscle Fibers White in Domestic Meat Animals and Birds muscle fiber size white white red muscle fiber # white red red 12

13 Whole Body Animal Growth double muscled normal Whole Body Animal Growth Distribution of Body Components During Growth and Development 13

14 Whole Body Animal Growth Satellite cells respond to growth promotants Whole Body Animal Growth Examples of growth promotants Effect of Exogenous GH on Muscle Fiber Size in Boars, Gilts and Barrows. Effect of beta- Adrenergic Agonists on Muscle Fiber Size. But what are they increasing?? 14

15 Whole Body Animal Growth Effect of Major Genes on Histochemical Traits of Valuable Muscles in Different Species Data from genetically modified animals Data from promotant treated animals Relative Change (% control) in Amount of Type 1, 2A, 2Ax & 2B Myosin Heavy Chain (MyHC) Isoform in Longissimus Muscle of Pigs Feed PAYLEAN over a 6 week Period. Whole Body Animal Growth Examples of growth promotants Effect of Cimaterol on Muscle Fiber Type Composition in Young Friesian Bulls Effect of Implants (RALGRO and SYNOVEX-S) on Muscle Fiber Type Composition in Cattle 15

16 Hormonal Regulation of Growth Performance and Carcass Characteristics of Implanted Cattle with Estradiol (E2) and Trenbolane Acetate (TBA) Alone or in Combination Hormonal Regulation of Growth Stress - related factors Cas and others Major Effects of GH SS GHRH GH 16

17 Hormonal Regulation of Growth Stress - related factors Cas and others GH on Pig Growth and its Carcass SS GHRH GH Hormonal Regulation of Growth Stress - related factors Cas and others hgrf on Lamb Growth and Carcass SS GHRH GH 17

18 Hormonal Regulation of Growth Adrenergic hormones Response to Adrenal Medulla Stimulation Hormonal Regulation of Growth Zilpaterol, Steers Growth and Carcass Performance 18

19 Hormonal Regulation of Growth Satellite cells respond to growth promotants Hormonal Regulation of Growth 19

20 Hormonal Regulation of Growth A Chihuahua walking with a Great Dane more than 50 times its mass. Hormonal Regulation of Growth 20

21 Hormonal Regulation of Growth 21