Lectures 3, 9, 10, 11: Prenatal and

Transcription

1 Animal growth and development 2 nd review Lectures 3, 9, 10, 11: Prenatal and Muscle Growth and Development

2 Development Principles similarity among species progressive causal and irreversible; ing complexity formation of discrete structures, to a final stable state t cellular association effects period of p competence

3 From: Hafez & Dyer (1969) Animal Growth and Nutrition, p. 23. Lea & Febiger, Philadelphia a.

4 From: Gerrard, DE & Grant, AL Principles of Animal Growth & Development. Kendall/Hunt Pub. Co., Dubuque, IA

5 From: Hafez & Dyer (1969) Anima Philadelphia. al Growth and Nutrition, p. 23. Lea & Febiger,

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7 Pre-natal growth Pre-natal growth α birth weight (duh!) Factors affecting: Heredity Dam size/age Litter size Placental size Maternal nutrition/health

8 Skeletal muscle striated voluntary Types of muscle Smooth muscle Cardiac muscle From: Frandson, RD Anatomy and Physiology of Farm Animals. Lea & Febiger, Philadelphia.

9 From: Frandson, RD Anatomy and Physiology of Farm Animals. Lea & Febiger, Philadelphia.

10 From: Swatland, HJ Structure and Function of Meat Animals. Prentice-Hall, Inc., Englewood Cliffs, NJ.

11 Sarcomere Fundamental unit of muscle fiber From Z line to Z line From: Swatland, HJ Structure and Function of Meat Animals. Prentice-Hall, Inc., Englewood Cliffs, NJ.

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13 Fiber types Based upon contraction speed and metabolic pattern Slow-twitch, oxidative (SO) AKA Type 1, β red depend upon oxidative metabolism, mitochondria fiber diameters cell size (protein:dna) slower contraction speeds ( 100 msec)

14 Fiber types Based upon contraction speed and metabolic pattern Fast-twitch, glycolytic (FG) AKA Type 2b, α white depend upon anaerobic (glycolytic) metabolism, mitochondria fiber diameters fast contraction speeds ( myosin ATPase); p ( y ) 7.5 msec

15 Fiber types Based upon contraction speed and metabolic pattern Fast-twitch, oxidative-glycolytic (FOG) AKA Type 2a, intermediate, α red both oxidative and glycolytic capacity intermediate fiber diameters fast contraction speeds

16 Histochemical determination of fiber types Myosin ATPase staining Acid or alkali preincubation Fast alkali-stable Slow acid-stable Proportional to twitch speed Succinate dehydrogenase (SDH) staining Proportional to mitochondrial density From: Swatland, HJ Structure and Function of Meat Animals. Englewood Cliffs, NJ. Prentice-Hall, Inc.,

17 Functions of different fiber types Slow, oxidative Slow, repetitive movements, e.g. postural muscles Very resistant t to fatigue Fast, glycolytic Rapid movements, heavy force generation Easily fatigued; can go into O 2 debt for short periods Fast, oxidative-glycolytic Adapted for rapid, repetitive movements Recruited after SO fibers Intermediate fatigue; recover faster than FG fibers Also: tonic muscle fibers (unusual) Multiply l innervated Graded response to stimulation frequency (vs. propagated action potential) Efficient isometric tension (e.g., anterior latissimus dorsi, holds wings against body)

18 From: McLachlan, J and Wolpert, L The spatial pattern of muscle development in chick limb. In: Goldspink, DF (Ed.) Development and Specialization of Skeletal Muscle. Cambridge University Press, Cambridge.

19 Cellular differentiation Pre-myoblasts myoblasts myotubes 1 myofibers Late-arriving unfused myoblasts 2 myotubes 2 myofibers

20 Myoblast fusion is a terminal differentiation step; myotubes can no longer divide (i.e. cells leave the cell cycle):

21 From: Swatland, HJ Structure and Function of Meat Animals. Prentice-Hall, Inc., Englewood Cliffs, NJ.

22 From: Swatland, HJ Structure and Function of Meat Animals. Prentice-Hall, Inc., Englewood Cliffs, NJ.

23 From: Swatland, HJ Structure and Function of Meat Animals. Prentice-Hall, Inc., Englewood Cliffs, NJ.

24 Prenatal expression of MRFs in the mouse Day Somite Limb bud 7 8 Myf-5 9 " myogenin 10 " " MRF-4 Myf-5 11 " " " " myogenin MyoD 12 " " " " " 13 " " " " 14 " " " " 15 " " " 16 " MRF-4 " " MRF-4 17 " " " " " 18 " " " " " 19 " " " " " 20 " " " " " 21 " " " " "

25 Physiological differentiation 1. Growing nerves invade developing muscle; multiple nerves contact each fiber, each nerve contacts many fibers 2. By birth, only one nerve contacts each fiber; each nerve contacts many fibers 3. Motor unit = set of fibers innervated by a single nerve 4. All fibers within a motor unit are of the same type

26 From: Goldspink, G Growth of muscle. In: Goldspink, DF (Ed.) Development and Specialization of Skeletal Muscle. Cambridge University Press, Cambridge.

27 The number of muscle fibers is set prior to birth (around the end of the second trimester; Therefore, post-natal muscle growth involves increases in length and girth of existing muscle fibers.

28 The number of muscle fibers is set prior to birth (around the end of the second trimester; Therefore, post-natal muscle growth involves increases in length and girth of existing muscle fibers.

29 Sex Males have more muscle (70 vs. 64% of carcass wt) and less fat (11 vs. 16%) than females BUT: Distribution of carcass muscle, fat and bone in cattle (% of carcass wt) Tissue Forequarter Hindquarter F M F M Muscle Fat Bone SO Th d t (f t i ld) i i th l SO: The advantage (for meat yield) is in the lowervalue forequarter, i.e., neck & shoulders.

30 Hormonal control of muscle development and growth IGF-I, IGF-II proliferation differentiation Basic FGF, TGF-β proliferation differentiation GH no direct effects?

31 Genetics Species and breeds vary in muscularity Muscle distribution relatively constant among cattle breeds Exceptions exist, e.g. athletes, double-muscled cattle, callipyge sheep

32 From: Lawrence, TLJ and Fowler, VR Growth of Farm Animals. CAB International, New York.

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35 From: Goldspink, G Growth of muscle. In: Goldspink, DF (Ed.) Development and Specialization of Skeletal Muscle. Cambridge University Press, Cambridge.

36 From: Goldspink, DF Physiological factors influencing protein turnover and muscle growth. In: Goldspink, DF (Ed.) Development and Specialization of Skeletal Muscle. Cambridge University Press, Cambridge.

37 Source: Hill et al., Animal Physiology, Sinauer Associates, Sunderland, MA.

38 Animal experiments Human experiments From: Goldspink, G Growth of muscle. In: Goldspink, DF (Ed.) Development and Specialization of Skeletal Muscle. Cambridge University Press, Cambridge.

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40 Source: Hill et al., Animal Physiology, Sinauer Associates, Sunderland, MA.