Exam 1 Flashcards
(210 cards)
1
Q
Hypertrophy in muscles
A
- increase in postnatal muscle mass
- satellite cells
- Growth of muscle reflects in its mass
- > the number of cells present and the amount of protein accumulated in each cell
2
Q
Altering Muscle Hyperplasia
A
- MYOSTATIN is the key player
- Negative regulator of muscle growth
- Reduce or knock out myostatin to increase muscle fiber hyperplasia
Ex. Mighty mouse, Piedmontese, Belgian Blue - myomiRNA, muscle specific miRNA, negative regulators of gene expression; however some also activate gene expression
Ex. Texel sheep
3
Q
Extracellular Matrix Proteins (ECM) Role in Control of Cartilage Maturation(Growth Plate)
A
- ECM is critical for proper differentiation and organization of growth plate chondrocytes
- Mutations in collagen XI causes severe skeletal abnormalities
- Deficiency of collage XI causes death at birth
4
Q
Muscle Pathologies (Dystrophies)
A
- rapid loss of muscle protein and skeletal muscle mass with muscular dystrophies
- due to greatly increased protein degradation with little or no change in muscle protein synthesis
5
Q
What type of animal should we farm more of?
A
- ruminants, like cattle, because they can take grass and things we can not utilize in our diets and make it into consumable produce
6
Q
PAX 7 Role in Myogenesis
A
- Works with PAX3 in early development
- predominates during post-natal growth and muscle regeneration in the adult
- Satellite cells
7
Q
Intramuscular (IM or marbling) Adipose Depot
A
- fat deposited within the muscle
- primary factor determining quality grade in young beef carcasses (impacts value)
- some consumers willing to pay for high marbling
- increase marbling score=increase number and area occupied by fat cell
- accumulate in close proximity to blood vessels
- extended time-on-feed increases excess fat deposition
- postnatal adipose tissue dev was believed to occur in order of internal, intermuscular, subcutaneous and intramuscular, BUT new research shows its simultaneous
8
Q
Callipyge Gene (CLPG) Sheep Mutation
A
- Specific muscle hypertrophy, only certain muscles affected
- unique inheritance pattern
- natural mutation that increases muscle mass
- Hypertrophy of loin and leg, “beautiful buttocks”
- Evident at 4-6 wk of age
- Non-mendelian Genetics
- Polar overdominance
- Heterozygotes who inherit the CLPG mutation from sire(paternal/dad) express the phenotype
- Homozygotes are normal in appearance
- leg grows at a faster rate than the loin
9
Q
Fetal phase in embryonic development
A
- maturation and specialization of tissues
- dramatic increase in size of existing organs and tissues
- over 75% of fetal growth occurs in this phase
- becomes recognizable as to what species animal is
10
Q
2 Types of bone
A
1) Hard, Compact or Cortical
- Dense, hard nature
- Cortical ring surrounding a bone marrow cavity of long bones
- 80% of bone in the skeleton
2) Spongy
- Sponge-like appearance
- vertebrae, flat bones or end of long bone
- Deposited in a fibrous network
- Found in axial skeleton (vertebrae) as well as in epiphyseal and marrow regions of long bones
- 20% of bone in skeleton
11
Q
Growth
A
- general and normal expansion of size as produced by the accretion of tissues similar in composition to that of original tissue or organ
- if an animal has increased in weight, it has grown
- cannot use weight to determine growth in finishing lots because the animals have put on excess fat
12
Q
Lipolysis
A
- release of fatty acids from triglycerides
- hormone controlled process
13
Q
Advantage of brown fat in sheep
A
- increasing brown fat can help to increase survival rate of lambs after birth
- maternal supplementation with Arginine can increase BAT in lambs
- must supplement to ewe bc they do not have brown fat
14
Q
Maturation in Myogenesis
A
- functional muscle fibers form from myotubes
- once myoblasts fuse into myotubes, they further differentiate to mature
15
Q
Regulatory factors
A
- factors that regulate determination or differentiation
Ex: muscle regulatory factors - specific factors to regulate the process
16
Q
Order of adipose deposition
A
- Perirenal
- Visceral
- Intermuscular
- Subcutaneous
- Intramuscular
17
Q
What happens as muscle grows?
A
- increase in DNA
- Increase in protein
- Increase in the amount of protein per unit of DNA
18
Q
M line in a sarcomere
A
- center of thick filament
19
Q
Two Osteogenic pathways in Osteogenesis
A
1) intramembranous ossification
- flat bones of the face, most of the cranial bones, and the clavicles (collarbones)
2) endochondral ossification
- long bones
20
Q
Sarcomere
A
- smallest unit of contraction
- many of them
- one z line to z line makes up a single sarcomere
- length of sarcomere influences meat tenderness
- > if in contracted state meat will be tougher and vice versa
21
Q
Visceral(VS) Adipose Depot
A
- located within the body cavity in close association with the viscera
22
Q
Myofibrillogenesis (part of differentiation)
A
- development and formation of myofibrils(muscle fibers)
- 1st myofibrils are unstriated
- as myogenesis proceeds, those immediately beneath the sarcolemma are the first to become striated
- nuclei migrate from their central core position to the periphery
- Increase in number by further fusion of myoblasts
23
Q
Calcium metabolism
A
- is a complex system
- Ca++ very tightly regulated
- Will be released into the bone from the blood stream
1) Low blood Ca - Release of PTH which stimulates osteoclast activity and corresponding resorption of bone calcium
2) High blood Ca - Thyroid gland releases Calcitonin
- Stimulates osteoblast activity with a corresponding deposition of calcium into bone
24
Q
Sliding Filament Theory
A
- muscle shortens during contraction without either filament (thick or thin) changing in length
- instead filaments slide past eachother in their region of overlap
- force of contraction is generated by the process that actively moves thick and thin filaments past eachother
25
SNP(single nucleotide polymorphism) Within the Myostatin Gene
- SNPs transition the G allele to an A allele in the 3’ UTR
- Creates a target site for miRNAs
- miRNA down-regulates myostatin, causes hyperplasia
26
Adipose tissue role
- stores triglycerides and acts as an energy reservoir
- store surplus lipid energy for subsequent mobilization in times of need
- protection for vital organs (KPH)
- reservoir for fat storage (lipids)
27
miRNA
- Small non-coding RNA which post-transcriptionally regulate gene expression
- most are negative regulators of gene expression
- if binds to mRNA during translation mRNA is degraded and the protein is not produced
28
How is growth accomplished?
1. Hyperplasia
| 2. Hypertrophy
29
Double Muscling- the cause and effect
```
CAUSE
- Loss of active myostatin
- Myostatin is a NEGATIVE regulator of
muscle growth
- little amount of myostatin means that animal will develop extra muscle fibers and have increased hyperplasia (lots of muscle development)
EFFECT
- Increased hyperplasia
- Born with double the number of muscle
fibers
- improved sensory traits
- increases the percentage of carcass weight as primal cuts in finished steers
- muscle fiber diameter does not differ only number
```
30
Nebulin
- myofibrillar protein
| - parallels thin filament to Z line
31
Serial Slaughter Studies
- uniform group of steers managed the same way
| - slaughter them at given intervals of time across a finishing period
32
How can DNA and protein increase?
- Satellite cells
- > First identified in 1961 by Alexander Mauro
- > It is a postnatal source of DNA
- > Control postnatal muscle growth
33
How to measure whole body protein metabolism?
- urinary excretion of 3-methylhistidine (3-MH)
- Myosin and actin have histidine residues that are post-translationally modified with the addition of a methyl group
- 3-MH can not be reused and is quantitatively excreted in the urine on muscle breakdown
- usually expressed as a ratio of 3-MH to creatine
Exception: In Sheep, 3-MH is further metabolized and cannot to be used to measure protein breakdown
34
How to measure prenatal development
- figuring out how old the fetus is to project birthdate
1) somite formation
- # = age
- mice and poultry
2) weight
3) length
- crown to rump length (livestock)
- measured from poll to ischium of pelvis
4) anatomical indications
- visual evaluation of gross developmental changes
- late phases will show this
35
GDF8 allele of Texel sheep is characterized by:
- by a G to A transition in the 3’UTR
- creates a target site for miRNAs
- > MyomiRNAs that are highly expressed in skeletal muscle
- This causes translational inhibition of the myostatin gene and hence contributes to the muscular hypertrophy of Texel sheep
- strongly expressed in skeletal muscle
- total level of circulating myostatin was 1/3 of that in wild type sheep although mRNA levels were unaffected
36
Pluripotent Stem Cells
- can give rise to all cell types of the body, but not placental cells
- embryonic stem cells
37
Myogenesis Summary
- prenatal formation of skeletal muscle
- Muscle mass is determined by number and size of muscle fibers
- During myogenesis, extent of muscle multiplication largely determines number of muscle fibers
- MRFsand PAX3/7 control the process
- MyomiRNAs are also involved
- Muscle fiber number is set before birth!
- > Postnatal growth(after myogenesis) is hypertrophy of existing fibers
38
Estrogen receptors Role in Control of Cartilage Maturation (Growth Plate)
- Pubertal growth spurt and cessation of growth are induced by sex hormones
- causes a pubertal growth sport (causes people to
reach maturation earlier and cessation)
39
Osteogenic cell
- develops into osteoblast
| - stem cell
40
How does bone form through fetal development?
- Throughout fetal development and into postnatal growth and development, bone forms on the cartilaginous matrix
- By the time a fetus is born, most of the cartilage has been replaced with bone
- Some additional cartilage will be replaced throughout childhood, and some cartilage remains in the adult skeleton
41
Inheritance of double muscling
- Gene responsible for double muscling phenotype has
been mapped to chromosome 2
- Named mh for muscular hypertrophy
- DM phenotype occurs in the homozygous
recessive condition (mh/mh)
- Heterozygote (mh/N) exhibits some increase
in muscle mass and has less negatives
42
What is the largest muscle tissue in an animal
- longissimus thoracic et lumborum
| - accounts for 10% of total muscle weight
43
Tissues
- closely associated with cells and cell products that act synergistically to perform specific functions
44
I band in a sarcomere
- isotropic, light band
| - region which only contains thin filaments
45
Perirenal (PR) Adipose Depot
- fat deposited around the kidney
46
White Adipose Tissue (WAT)
- primary site of energy storage (stores lipids)
- most common fat cell, used to store fat and found beneath the skin and abdomen
- adipocytes, specialized cells devoted to the accumulation of triglycerides
- contains triglycerides that are formed from free fatty acids and released from lipoproteins in bloodstream
- other metabolites accompany the fatty acids into the adipocyte which are required for de novo fatty acid synthesis
47
Satellite Cells
- Quiescent or dormant cells found between
basement membrane and sarcolemma in adult or
postnatal skeletal muscle
- Source of nuclei for postnatal muscle growth
- Important for muscle repair!!
- muscle satellite cells play a crucial role in postnatal muscle growth (fuse with existing muscle fibers and provide the nuclei needed for postnatal fiber growth)
- muscle hypertrophy in postnatal growth
48
Costamere
- myofibrillar protein
- anchors myofibrils to sarcomere
- floods calcium into the cell
49
How are muscle fibers classified
- classified based on speed of contraction and type of metabolism
- differs based on muscle fiber types
- Type 1 (primary fiber development of myogenesis)
- Type 2A, 2X and 2B(secondary fiber development)
50
How has animal production and growth changed in animal markets?
- increased the size of the animals, but with more muscle and less fat
51
Diaphysis
- shaft region of bone
- cartilage becomes bone
- bone ossification(grows length of bone)
52
IGF-1 Role in Control of Cartilage Maturation (Growth Plate)
- Stimulate proliferation of chondrocytes
53
Adipocyte Growth
- Postnatal adipose tissue growth is an increase in the number of adipocytes (Hyperplasia) and an increase in the size (hypertrophy)
- 70% due to increase in cell diameter and volume
- 30% due to increase in cell number
- hyperplasia continues through postnatal growth
- > grows in waves, increase cell number followed by an increase in volume
54
Adipocyte transcription Factors (MRFs of the fat cells)
1. Peroxisome proliferator activated receptor (PPARy)
- transcription factor that binds to the fat specific enhancer present in the adipocyte fatty acid
2. CCAAT-enhancer binding protein (C/EBP)
- C/EBPa and PPARy appear to act synergistically by triggering the adipocyte differentiation program and reciprocally activating transcription of one another
3. Reinoic Acid (RA)
4. WNT
55
Types of Genetic Mutations in Muscle Growth
1. Myostatin
Double muscled animals
A. Piedmontes and Belgian Blue have mutations in myostatin gene (complete KO)
B. Texel has reduction in active myostatin due to miRNA mutation
C. Dogs are homozygous for mutation(2 copies)
2. Callipyge
- miRNA involved
- unique inheritance pattern (heterozygotes that inherit gene from sire/dad)
- specific muscle hypertrophy that becomes evident after birth
- prevents normal down regulation of key genes (DLK-1, PEG-11)
56
A band in sarcomere
- antisotropic, dark band
| - length of thick filament and contains thin filament(actin) that overlaps the thick filament(myosin)
57
TGF-beta Super Family
- inhibits proliferation of satellite cells
- causes prenatal muscle growth rates in adults*
- knockout of myostatin, increases muscle fiber hyperplasia
ex: Double Muscled Cattle
- loss of active myostatin causes increased muscle fiber hyperplasia and double in muscle size
58
Abdominal Fat Pad (poultry) Adipose Depot
- within the body cavity, under the skin
59
2 populations of somitic cells
1) Dermomyotome
- form dermatome and myotome
- dermatome-> cells responsible for forming dermis
- mytome-> cells responsible for developing all muscles of the body
2) Sclerotome
- form vertebral column
60
Buttons
- Cartilaginous ends of the thoracic vertebrae in cattle
- with age, Ossification starts from the center and works outwards
- Evaluate top 3 buttons anterior to the 12th rib
- Also look at the lumbar region for ossification (work posterior to anterior)
61
True growth
- increase in structural tissues (bone, muscle and connective tissue)
62
What do bones need to grow?
- Bone contains Calcium and Phosphorus in an 2:1 ratio
- You want double the amount of calcium to phosphorous
- Most recommendations are to feed Ca:P at 2:1 ratio
- You find most feeds don’t have lots of calcium, they are majority phosphorous, so in order to make the 2:1 ratio of calcium to phosphorous then you can add limestone
- Magnesium and Vitamin D are necessary for proper growth
63
Paranemin and Synemin
- myofibrillar protein
| - bind and stabilize myofibril to myofibril interactions
64
How do satellite cells increase muscle fiber growth
- Proliferate slowly(make multiple cells)
- Differentiate into myoblasts
- Fuse with existing fibers
- Purpose to either increase DNA content per fiber or
replace nuclei that are no longer functional
- Minimum number must be maintained to ensure
regenerative potential in mature muscle
- satellite cells decrease as muscle grows into adulthood, there is a much larger number at birth
65
Embryonic growth in meat animals
- meat animals spend a majority of their existence in the prenatal stage
- development of all tissues begins at fertilization
66
Heritability and selection to help feed the growing population
- animal growth and carcass traits have high heritability
- look for animals with faster rates of growth and utilize those animals
- identify superior genetics and use animals with those
67
Reserve Zone of Epiphyseal Growth Plate
- The reserve zone is the region closest to the epiphyseal end of the plate and contains small chondrocytes within the matrix
- These chondrocytes do not participate in bone growth but secure the epiphyseal plate to the osseous tissue of the epiphysis
68
3 Types of Adipose Tissue
1. Brown
2. White
3. Brite (brown IN white), or Beige
69
Elastin fibers
- embedded in mucopolysaccharide ground substance
- > chondroitin sulphates most important
- rubberlike
- capable of being stretched to nearly twice their length
70
Perimysium
- surrounds muscle bundle in skeletal muscle
71
Sir John Hammond
- pioneer in animal growth research
- documented that the growth of animals produces tissues that accumulate in a sigmoidal manner
- showed that different tissues and organs grow at different rates and mature at different times
72
Purpose of Skeleton
- provides structural support for the body
73
How does Adipocyte Hypertrophy Occur
- occurs through the accumulation of triglycerides in the adipocytes
1. Incorporation of dietary fatty acids
2. De Novo Fatty Acid Synthesis
- "from scratch"
- utilization of precursors to synthesize fatty acids
3. Lypolysis
- non-esterified free fatty acids
- release of glycerol is best measure of the rate of lypolysis
74
Secondary Myotube Fibers
- Smaller, develop on the framework of the primary fibers
- influenced by maternal nutrition (runt pigs have lower number of secondary fibers)
- 80-90% of myofibers present at birth are derived from secondary fibers
- fetal phase
- muscle fiber types 2A, 2X and 2B evolve
75
Can We Accelerate Marbling Deposition? Study
- Timing of Exposure to high concentrate diet(conc)
- found that when ate conc-conc had highest marbling deposition
- conc-forage had second best
- forage-conc third
- forage-forage lowerst
76
3 types of muscle
1) skeletal
2) smooth
3) cardiac
77
Adipogenesis
- includes proliferation, differentiation and conversion of cells into lipid-filling cells (adipocytes)
1. Fertilized Egg
2. Fibroblast/adipoblast (determination)
3. Preadipocyte (differentiation)
4. Adipocyte
78
Runts
- Common in litter bearing animals
- While in utero restriction of nutrient supply to the developing fetus (maternal nutrtion/nutrient delivery to the fetus)
-> can alter muscle fiber development
- Limited blood supply to the fetus caused by poor uterine position
- Has a low birth weight compared to others
- Has lower postnatal growth
- produce carcasses with less muscle and more fat
- there is a reduction in secondary to primary muscle fibers
Ex: Runt Pig
79
Carcass Maturity Classification
- Growth plate closure determines maturity in lamb carcasses
- > used to determine age of carcass for grading
- During processing, feet are removed at distal end of metacarpal
- If less than 12 months of age, epiphyseal cartilage is present and it “breaks” at distal epiphyseal plate
- if over 12 months of age, epiphyseal cartilage is ossified and foot separates at metacarpophalangeal joint, "Spool joint"
- In beef, ossification of vertebral column determines skeletal maturity
- > Sacral –lumbar –thoracic (posterior to anterior)
80
Mesenteric (MS) Adipose Depot
- around intestines
81
Myostatin
- Discovered that GDF-8(myostatin) is a negative regulator of muscle growth(prevents from growing too much muscle and not enough fat)
- inhibits myogenesis (cell muscle growth and proliferation)
- if do not have enough myostatin animal will have little body fat and EXCESSIVE MUSCLE
- detected early in the myotome
- continued expression in adulthood
- located in the cytoplasm of muscle fibers
- myostatin expression occurs during periods of primary and secondary fiber formation
- Myostatin also involved in muscle homeostasis during
adulthood
-> May inhibit satellite cell proliferation
82
Subcutaneous (SC) Adipose Depot
- fat deposited under the skin or hide
- pigs predominantly deposit here
- ruminants
83
Tibial dyschondroplasia (TD)
- Seen in poultry predominately, ~50% of broiler chickens have this problem
- Growth plate cartilage accumulates in proximal region of tibia and femur
- Getting too much cartilage and not enough none formation, you don’t have enough structural support
- Lameness, increased fractures in fibula, and increased susceptibility to osteomyelitis
- growth plate cartilage is not properly degraded and accumulates at the expense of bone formation
84
Maintenance Energy Requirement
- 15-25% of energy intake by animals is used to replace muscle protein that is degraded
- replacing proteins that are turned over each day
85
Exception to Myogenesis
- some fish
- do not appear to form myofibers in biphasic manner like mammals
- exhibit indeterminate growth (continued growth throughout life)
- can produce new muscle fibers throughout their growth (hyperplastic)
86
Growth/Differentiation Factor-8 (GDF-8) is in this family
- Expressed during muscle and adult skeletal
muscle development
- also known as myostatin
- mostly causes hyperplasia
During Embryogenesis
-> GDF-8 is restricted to myotome of developing somites
As an Adult
-> GDF-8 is expressed in many muscles throughout the body
87
Sliding Filament Theorists and their conclusions
- two independent research groups formed the sliding model of contraction
1) Huxley and Hanson
2) Huxley and Niedergerke
- figured out that muscle shortens during contraction w out either filament changing in length
- filaments slide over eachother and area of overlap increases
88
Why is it difficult to study and measure protein degradation/turnover?
1. In vivo
- methodology is complicated
2. In vitro
- isolated muscle fibers or strips are in negative nitrogen balance
3. Tissue Culture
- cells are usually embryonic in terms of quantity of protein accumulated
89
How much protein in skeletal muscle can be replaced per day
- 20-25% of protein in the skeletal muscle can be broken down and replaced per day (especially in earlier life)
90
How do we produce more beef to feed a growing world?
- need to increase beef prod by 65%
1) increase number of animals
2) produce more beef meat per animal
91
Thick filament
- myosin
- most abundant contractile protein
- myosin is a hexamer (2 heavy chains and 2 light chains)
- head heavy and tail light
HEAD
- site of actin interaction
- catalytic site for ATP hydrolysis
92
Proteolytic Enzymes
- responsible for protein degradation
| - endopeptidases
93
2 Types of Muscle Fiber
- Depends on the function of the muscle
1. Posture muscles
- Increased number of red, fatigue-resistant muscle
fibers
- Provide tonic tension to maintain posture
2. Locomotive muscle
- Primarily of fast contracting, glycolytic fibers
- Provide quick power movements that last for a short period of time
94
What is bone comprised of?
- Comprised of an organic matrix that provides flexibility and strength
- A mineral-impregnated matrix is very strong and has the ability to remodel itself
1) 30% of bone is a matrix
- > Composed of collagen fibers and a component called ground substance
2) 70% of bone is composed of minerals
- > Provide rigidity and strength
95
Muscle tissues
- skeletal muscle represents the bulk of carcass weight in meat animals
- ***largest muscle = longissimus thoracic et lumborum, which accounts for 10% of total muscle weight
96
Intermuscular (IT) Adipose Depot
- fat deposited between muscles
| - ruminants
97
How do bones grow in length?
Epiphyseal plate (growth plate)
- Endochrondral growth
- Area of growth in a long bone, lengthens the bone
- Layer of hyaline cartilage where ossification occurs in immature bones
- On the epiphyseal side, cartilage is formed
- On the diaphyseal side, cartilage is ossified, and the diaphysis grows in length
- The epiphyseal plate is composed of four zones of cells and activity
98
Best Growth Promoting Compounds
- increase muscle growth rates by reduce protein degradation
1. Trenbolone acetate
2. beta-antagonists
99
Determination in Myogenesis
- mesenchymal stem cells become myoblasts(committed muscle cell)
- proliferation occurs (inc of cell #)
- cells are restricted or constrained to a muscle cell lineage (commit to a certain fate)
- triggered by expression of one or more genes:
1. MRFs (muscle regulatory factor genes)
- Myf-5, Myo-D, Mrf-4 (also a differentiation factor), Myo-G
2. PAX 3/7 (Paired Box Genes)
100
Degradation (breakdown)
- proteolysis of polypeptides by the diverse collection of proteinases within both the cytoplasm and lysosomal compartments of muscle cell
101
Mutation of myostatin in Texel Sheep
- Single Nucleotide Polymorphism (SNP) in Texel Sheep
- This mutation creates a target site for miRNA that bind myostatin mRNA and hinder translation to functional protein
- Reduced myostatin causes increased muscle fiber hyperplasia
- Texel Sheep have more A alleles on myostatin gene compared to other breeds (this SNP causes repression of myostatin- 90% have mutation)
- myostatin mutation changed the gene expression profile in prenatal skeletal muscle
102
Multipotent Stem Cells
- can develop into more than one cell type
| - adult stem cells (MSC) and cord blood cells
103
Myogenesis 3 Defined Steps
1. Determination
2. Differentiation
3. Maturation
104
Synthesis
- conversion of amino acids into functional proteins by the protein synthetic apparatus in cytoplasm of muscle cells
105
Transverse tubules (T-tubule)
- part of muscle fibers
| - bilipid membranes that surround myofibril
106
In what ways can we produce more meat while losing land?
1) we will have to produce more beef on fewer hectares of land
2) need more kg of beef meat per animal slaughtered
3) need to use available technologies to increase production efficiency
- the use of growth promotants
107
Unipotent Stem Cells
- develop into only one cell type
| - can determine which cell to become
108
Adipocytes
- found in perimysial spaces, accumulate near blood vessels
- fat cell
- filled with triglycerides
- differentiation of pre-adipocytes
- rounding up of cell shape
- lipogenic enzyme capacity to build up
- has lipid droplets
109
Smooth muscle
- involuntary, non-striated
110
Osteoclasts
- functions in resorption, the breakdown of bone matrix
- large, multinucleate cells
- Involved in bone resorption (breakdown) and remodeling
- Form from fusion of hemopoietic cells of monocyte-marophagelineage
111
Epimysium
- surrounds muscle in skeletal muscle
112
Cells
- smallest unit of life that can replicate independently
- adipocytes (fat cells)
- muscle fibers (muscle cells)
113
Thin filament
- myofibrillar protein=actin
- 2nd most abundant contractile protein
- has G-actin and F-actin subunits (create the groove)
- prominent groove the length of F-actin filament
REGULATORY PROTEINS
- tropomyosin: occupies F-actin groove
- Troponin: located at every 7th G-actin molecule
- interactions between these proteins regulate contraction
114
Connective tissue fibers
1) collagen fibers
| 2) elastin fibers
115
Termination of Long Bone Growth
- Termination occurs when cartilage growth stops or slows to a rate that allows it to be overcome by ossification
- Epiphyseal closure
- > Fusion of the epiphyses and diaphysis into a single bone
116
Growth of tissues
- fat sky rockets at maturity
| - want to harvest the animal before excess fat aka when there is max muscle growth
117
Progression from Epiphyseal Plate to Epiphyseal Line
- Bones continue to grow in length until early adulthood
- The rate of growth is controlled by hormones
- When the chondrocytes in the epiphyseal plate cease their proliferation and bone replaces the cartilage, longitudinal growth stops
- All that remains of the epiphyseal plate is the epiphyseal line
- Epiphyseal plates are visible in a growing bone
- Epiphyseal lines are the remnants of epiphyseal plates in a mature bone
118
MyomiRNA
- muscle specific miRNA
- therefore will cause mRNA degradation during translation
- Currently includes 8 miRNA exclusively or preferentially expressed in striated muscle
- Other miRNAs can alter myogenesis and muscle growth
Ex: Texel Sheep
- reduce the amount of myostatin (a negative regulator of muscle growth)
- little myostatin will cause excessive of muscle growth
119
Medullary Cavity
- bone marrow in the bone
120
Gene Knock Out (KO)
- A genetic technique in which one of the
organism’s genes is made inoperative (KO)
- Results in the loss of function for that
gene/protein
- Used to understand the role of a specific gene
compared to wild-type organism
121
Brown Fat development in Sheep
- brown fat develops in late gestation and disappears shortly after birth
1. 80d of gestation
- dense cell population, but no UCP1
2. 140d of gestation
- increase in size of adipocytes (hypertrophy)
- white and brown adipocytes
- UCP1 maximal activity
3. At birth
- reduction in number of lipid filled cells (white adipocytes)
- lower UCP1 expression level
4. At 30d of age
- disappearance of brown adipocytes
- only white adipocytes visible
- no UCP1 detected
122
Turnover
- general term that encompasses both the processes of protein synthesis and degradation
123
How does gestation length relate to animal size
- animals with larger adult size have longer gestation
| - elephants have the longest, cats have the shortest
124
Fiber type metabolism
- energy metabolism and muscle fiber type relationship
- energy metabolism is primarily either glycolytic or oxidative metabolisms
- Although, all fibers have a combination of both types of metabolisms
125
Transforming Growth Factor-β Superfamily
- Large group of growth and differentiation factors
- Regulate embryonic development
- Maintain tissue homeostasis in adults
126
Ratio of Secondary to Primary Myotube Fibers in Differentiation
- number of secondary myotube fibers which form around the primary myotube fibers varies between species and muscles
- larger number of secondary fibers
Pigs: 14:1
Lamb at birth 12:1
127
Myogenesis Growth Steps
1. Mesenchymal Stem Cells ->
2. myoblasts(determination)->
3. myotubes(differentiation)->
4. myotubes(maturation) ->
5. muscle fibers
128
Callipyge Gene Phenotype in Sheep (what looks like)
- specific muscle hypertrophy
- enlargement of loin and leg during postnatal growth
- reduced protein degradation (higher calpastatin)
- increased protein accretion
- increased cross-sectional area of FOG and FG fibers
- increased percentage of FG fibers
- TOUGH (looks like porkchop instead of lamb)
129
Tissue development in a growth curve
1) bone
- develops early, highest point at the beginning
2) muscle
- intermediate developing, at highest point in beginning
- primary fiber formation
- secondary fiber formation
- maturation
3) fat
- later in developing, low at the beginning
- highly variable
130
Major Secretory products of adipose tissue
- non-esterified fatty acids (NEFA)
- derived from the lipolysis of stored TAG
- process involving three main steps and requiring at least three different lipases
- > fatty acids undergo beta oxidation
131
Osteogenesis
- the formation of bone
- Early embryonic development, skeleton consists of fibrous membranes and hyaline cartilage
- By the 6 or 7th week (9 mo. gestation), the actual process of bone development, ossification(osteogenesis) begins.
132
Endochondral Ossification Overview
- long bone formation
- bone is developed by replacing hyaline cartilage
- takes longer than intramemberous ossification
- forms bones at the base of skull and the long bones
- perichondrium forms (a membrane covering the cartilage)
- creates primary ossification center (a region deep in the periosteal collar where ossification begins)
- secondary ossification center develops
- longitudinal growth of bones occur at the epiphyseal (growth) plate
133
Z line in a sarcomere
- center of thin filament
134
Postnatal muscle growth
- Satellite cells for muscle hypertrophy in postnatal growth
- postnatal muscle growth=hypertrophy
- > the enlargement of a relatively constant number of muscle fibers during postnatal growth
- results from deposition of additional muscle protein and incorporation of more nuclei into multinucleated muscle fiber
- over 50% of DNA muscle is accumulated during postnatal growth
- muscle fiber number does not change, the size increases in postnatal growth (BORN WITH SPEC AMOUNT OF FIBERS AT BIRTH- can vary btw breeds)
- Young vs. Old
- > younger are smaller in size and have fewer nuclei
135
Fractional Synthesis or breakdown rates
- rates expressed as percent per day
- 5% fractional synthesis rate
- > the quantity of new protein equivalent to 5% of that already present is synthesized per day
136
Fattening
- accumulation of fat
| - fattening is not true growth
137
Intramembranous Ossification Overview
- forms flat bones of the face, most of the cranial bones, and the clavicles (collarbones)
- Begins in utero during fetal development and continues on into adolescence
- At birth, the skull and clavicles are not fully ossified nor are the sutures of the skull closed
- This allows the skull and shoulders to deform during passage through the birth canal
- The last bones to ossify via intramembranous ossification are the flat bones of the face, which reach their adult size at the end of the adolescent growth spurt
138
Titin
- 10% myofibrillar protein
- M to Z line
- spring like
- helps maintain the structure of half sarcomere
139
What would happen if we reduced protein degradation?
- would decrease the maintenance energy requirements
- which would increase energy available for growth
- improves efficiency of production
140
Calcium dependent proteases
- calpains (required for activation)
1. u-calpain (micromolar levels of calcium)
2. m-calpain (millimolar levels of calcium)
3. Calpastatin
- inhibitor of calpains
- defined role in proteolytic degradation during postmortem aging of meat
- believed to be involved in degradation of living muscle
141
Primary Myotube Fibers
- formed during the initial stages of myoblast fusion and act as the framework
- more primary fibers means more muscle fibers
- 10-20% of myofibers present at birth are derived from primary fibers
- embryonic phase
- type 1 fibers evolve
142
Hypertrophy
- increase in cell size
143
Dressing % (carcass weight)
- the percent of live weight that becomes carcass weight(no organs just meat)
- majority of carcass weight is muscle (60%)
144
Three Main Functions Of Bone
1) To provide structural support for the body including attachment points for muscle, which are essential for locomotion
2) To serve as store for calcium and phosphorus that can be made available during disturbances in mineral homeostasis
3) To protect internal organs, such as the brain (skull) and lungs (ribs)
145
What is the problem with trying to increase beef production?
- with population expansion a lot of farmland was lost, specifically in the past 10 years
- this trend is expected to continue with population expansion
- NEED LAND TO INCREASE PRODUCTION
146
When a muscle fiber shortens what occurs
- muscle shortens in contraction without either filament changing in length
- width of A band = same length
- width of I band = shortens
- width of H zone = shortens
- distance between H zone to H zone = same
147
Adipoblasts
- undifferentiated mesenchyme cells destined to form adipocytes
- small, have no lipogenic enzymes, contain no lipid droplets
- proliferate
148
PAX 3 Role in Myogenesis
- major role during early skeletal muscle formation in the embryo
- Mutation = Splotch phenotype (in mice will have white patches on the body)
- Defects in muscle development
- increased cell death in myogenic precursors in limb musculature
149
Finishing weights of beef steer, market lamb and hogs
1. Beef Steer
- 1385-1400 lbs
2. Market Lamb
- 125-140 lbs
3. Hogs
- 300-330 lbs
150
Endomysium
- surrounds muscle fiber in skeletal muscle
151
Osteocytes
- Maintains bone tissue
- Mature bone cells
- Responsible for maintenance of bone matrix
152
3 Primary germ layers
- form in the embryonic phase
1) ectoderm
- outermost cell layer
- ultimately forms the skin and neuronal tissues
2) Mesoderm**
- middle layer
- develops into muscle, fat and bone
- origin of all cells/tissues
3) endoderm
- develops into tissues of respiratory and digestive tract
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Brown Adipose Tissue (BAT) or Brown Fat
- converts chemical energy to heat to protect against cold weather
- is darker in color due to mitochondria presence that generates energy for the cells
1. Uncoupling Protein 1 (UCP 1)
- an inner mitochondrial membrane protein, to uncouple oxidative phosphorylation from ATP production causing the dissipation of energy as heat
2. Non-shivering Thermogenesis
- lipolysis process releases fatty acids which are oxidized in situ to produce heat
- critical in maintaining body temperature immediately after birth and in arousal from hibernation
- capacity is lost about 7-10 days after birth
3. 2-4% of birth weight
- pigs lack BAT
154
Why must muscle cell hypertrophy be defined
- muscle fibers are multi-nucleated, so it is difficult to define just one unit
DNA UNIT
- volume of cytoplasm supported or managed by an individual muscle nucleus
DNA Unit Size (mg protein/mg DNA)
- ratio of protein to the number of nuclei (quantity of DNA) in the muscle
155
What happens if there is a mineral imbalance in bone?
- Mineral imbalances can result in early growth plate closure
- stunts the growth, long term growth terminated
156
Osteoblasts
- Precursors to osteocytes
| - form bone matrix
157
Totipotent Stem Cell
- can form any cell type in the body, plus extra embryonic or placental cells
- embryonic cells within first couple of divisions after fertilization
158
Osteochondrosis Dissecans (OCD)
- Common with horses, high growth rate
- Can also occur in pigs, growth rate and hormonal imbalance are implicated
- Cartilage and bone developmental disorders
- Skeletal growth is rapid during first 12 mo, 6 months of age bone mineralization is 68% complete
- Significant economic problem
1. Pigs: growth rate and hormonal imbalance are implicated
2. Equine: OCD related to diets high in digestible energy, Phosphorpus, and deficiency in Calcium
- abnormal proteoglycans in isolated OCD lesions
159
4 Bone Cell Types
1 ) Osteogenic cell
2) Osteoblasts
3) Osteocytes
4) Osteoclasts
160
Cartilage Templates for Bones
- uses a model tissue to lay down mineral matrix
- skeletal -> the most common template is cartilage
- cartilage serves as a template to be replaced by new bones*
- During fetal development, a framework is laid down that determines where bones will form
- As the matrix surrounds and isolates chondroblasts, they become chondrocytes (differentiation)
- > Unlike most connective tissues, cartilage is avascular (no blood vessels supplying nutrients and removing metabolic wastes)
- All of these functions are carried on by diffusion through the matrix
- This is why damaged cartilage does not repair itself as readily as most tissues do
161
Percentage basis
- tissue composition as a percentage of carcass weight
162
Percent composition of animals in a growth curve
- fat is low in the beginning
| - bone and muscle at highest point in the beginning, then will decrease
163
Muscle anatomy
- muscle
- muscle fiber bundle
- muscle fiber
- myofibril
- sarcomere
164
Lipogenesis
- synthesis of fatty acids
- incorporation of dietary fatty acids into triglycerides
1. In non-lactating ruminants and pigs this predominantly occurs in adipose tissue, acetate is a precursor
2. In poultry and humans, predominantly occurs in the liver
165
IGF-I (Insulin-like Growth Factor-I)
- stimulates proliferation and differentiation of myogenic cells
- stimulates protein synthesis rates and decreased protein
degradation rates in myogenic cells
- causes postnatal muscle growth rates in adults*
166
Neuralation
- event during development that results in the formation of spinal chord precursors
- helps orient fetus
- occurs simultaneous with events of gastrulation
- neural tube is formed
- once closed, form peripheral nerves
167
Marbling
- intramuscular fat
- fat within the muscle (streaks of fat within muscle)
- choice quality grade vs select quality grade marbling Spread
- when choice carcasses are abundant, spread is lower (vice versa)
- changes daily based on supply of choice carcasses in the market
Choice= small amount
Select= slight amount
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What controls muscle growth?
1. TGF-beta Super Family
| 2. IGF-I (Insulin-like Growth Factor-I)
169
Hyperplasia
- one cell becomes many cells
| - an increase in cell number
170
Differentiation in Myogenesis
- cell membranes of myoblasts FUSE to form MULTINUCLEATED MYOTUBES
- there are primary and secondary myotube fibers
- begin to express muscle specific proteins
- the cells stop dividing
- they align with one another
- there is an up-regulation/activation of muscle specific genes such as actin and myosin
171
Problems that can arise with Bone Growth Summary
- Improper nutrition, especially minerals in early life, can result in poor bone growth or early closure of growth plate
- > suggested 2:1 Ca:P to promote growth
- Dyschondroplasia -chickens
- Osteochondrosis- equine and can also occur pigs
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Adipocyte Hypertrophy
- cell diameter increases as lipid is deposited
- adipose cell number is NOT set at birth
- rate of lipid deposition and hypertrophy depend on relative rates of esterification and lipolysis
- occurs through the accumulation of triglycerides in the adipocytes
173
Connective tissue
- connect and hold tissue together
- differs from other tissues
- provides strength to the tissue and to the body as a whole
- media for transport of nutrients to cells are within the intercellular matrix
174
Determination
- involved progression restriction in their development pattern
- "commit" to a particular fate
- restriction in development and choose a lineage
175
Skeletal muscle
- voluntary, striated and multinucleated
176
Muscle Growth Definition and Trends
- net accumulation of protein that occurs when rate of protein synthesis is greater than the rate of protein degredation
1. Growth: Synthesis > Degradation
2. Atrophy: Synthesis < Degradation
3. Maintenance: Synthesis = Degradation
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Fusion in Myogenesis (part of differentiation)
- myoblasts align and come into close proximity
- small attachments become apparent
- dense structures beneath opposing membranes are generated and form TIGHT JUNCTIONS between myoblasts
- finally membranes join and become one (FUSE)
- forms a myotube
- some myoblasts will not become fibers, but will become satellite cells instead
178
4 Zones of Epiphyseal (Growth) Plate
1) Zone of resting cartilage
2) Zone of proliferating cartilage
3) Zone of hypertrophic cartilage
4) Zone of calcified cartilage
179
Desmin
- myofibrillar protein
| - protein responsible for "tying" myofibrils together
180
Sarcoplasmic reticulum
- part of muscle fibers
| - endoplasmic reticulum of the cell
181
Pre-adipocyte
- determination to form pre-adipocytes
182
How do cells become tissues
- becomes muscle, fat or bone
1) determination
2) differentiation
3) regulatory factors
183
Adipose Tissue Composition
- 91% composed of lipids(fat), it is a reservoir for storing fat
- tissue composed almost entirely of fat cells that are organized into lobules
- 80% of total adipose tissue weight is fat, over 90% of lipids stored as TAG
- lobules of fat cells are separated from each other and supported by partitions of loose connective tissue known as septa
- strands of septa form collectively around the stroma and are responsible for carrying blood vessels and nerves into the adipose tissue (high vascularized)
- contains fibroblasts and adipocytes (fat cells)
184
H zone in sarcomere
- region where only thick filament is present
| - in the center of a sarcomere
185
Tissue types
1) muscle tissue
2) connective tissue
3) nervous tissue
4) epithelial tissue
186
Cardiac muscle
- involuntary, striated and mononucleated
187
Belgian Blue Bull and Piedmontese Bull Myostatin Mutation
- results in double muscling from KO of myostatin
- Belgian Blue eliminates the mature active form of myostatin
- Piedmontese has a complete or almost complete loss of myostatin
- increased dystocia
188
The role of MRFs in Myogenesis
- MRFs role is determined using knock out (KO) models
- major control point in myogensis
If knock out Myf5 and MyoD
- the embryo fails to develop any skeletal muscle
If Knock out MyoG
- perinatal death occurs
- complete absence of functional skeletal muscle
189
Percent composition of muscle
- majority of muscle is predominantly water (75%)
| - protein makes up 20%, the other majority
190
Collagen fibers
- tropocollagen
- > most abundant protein in animals, 20-30%
- > synthesized by fibroblast cells
- straight, inextensible, non-branching and white in color
- relatively inelastic
191
Berg and Butterfield
- pioneer in animal growth research
- dissected carcasses at different stages of growth
- demonstrated growth and development patterns in tissue subsets
- new concepts of cattle growth book
192
Growth curve
- sigmoidal growth curve (looks like an S)
- starts slow after birth, then has a rapid inc in the middle, once hit maturity levels slow again
- before and after birth has slow growth
- rapid increase, very efficient growth period
- levels off as animal approaches mature size
193
How is the growth in the population going to affect the meat production system?
- the population is increasing bc due to medical advances seniors are living longer
- need to increase meat production to meet the growing population demand of the world
194
Fibroblastic Growth Factor Receptors Role in Control of Cartilage Maturation (Growth Plate)
- Presence of FGF halts proliferation of epiphyseal growth plate cells
- Appear to instruct cartilage precursors to differentiate
- Humans-mutations in receptors cause them to activate prematurely, cause dwarfism (FGFR3), abnormalities of face and limbs (FGFR2)
195
Differentiation
- elaborate a cell specific development program
- develop into muscle, fat or bone
- can not go back after this, determine what cell type to become
196
Order of utilization of adipose
1. Intramuscular
2. Subcutaneous
3. Intermuscular
4. Visceral
5. Perirenal
197
What is body composition made up of
1) muscle
2) fat
3) bone
198
Brite/Beige Adipose Tissue
- new fat cell type
- immature cell in white fat tissue matures to burn fat
- express the characteristic brown fat marker UCP 1, but they derive from a distinct population of cell precursors than brown brown fat
- regulated not only by cold temperature, beta-andrenergic stimulation and drugs such as TZDs, but also by hormones and secreted peptides
- the evidence that certain stimuli not only increase brown fat tissue, but also induce browning of white fat and increase energy expenditure has become an area of intense investigation for therapeutic purposes
199
Embryonic Phase in embryo development
- gastrulation
- > stage succeeds the formation of a blastocyt
- > regions begin to exert control over development
- > 3 germ layers form
1) ectoderm
2) mesoderm
3) Endoderm
200
Myostatin Knock Out in Mice
- creates larger animals due to increase in skeletal muscle mass by 2-3x
- DNA content(50%) and cell number(95%) increases
- "knock-out" of GDF-8 in mice
- discovered that GDF-8 is a negative regulatory of muscle growth
201
Somitogenesis (Somites)
- begin to see spinal chord, vertebrae and muscle
| - Somites are bilaterally paired blocks of paraxial mesoderm that form along the head to tail axis of the embryo
202
Meat animals vs humans growth rate
- animals mature at a faster rate than humans
| - different sizes but same growth curve
203
What makes up the majority of protein in the USA per capita consumption? What % of carcass weight is muscle and what % of live weight is carcass?
- beef makes up 30% of total per capita consumption in USA
| - 60%
204
Sarcoplasm
- part of muscle fibers
| - cellular cytoplasm
205
Epiphysis
- enlarged ends of bone
| - cartilage is formed for template
206
What does decreased intramuscular fat fractional growth rate indicate?
- intramuscular fat is not a late developing tissue, but can develop early in growth if nutritional management permits
207
3 stages of embryo development
1) germinal phase- fertilization to attachment
- fast
2) embryonic stage- complete when developing organism reflects its mature form
3) fetal phase- point where species identification can be established onward
- 75% of growth period
208
Development
- gradual progression from lower to higher state of complexity
209
Germinal phase in embryonic development
- 11 to 14 d
- characterized by rapid cell division known as cleavage
- increase in cell number without change in overall cell size
- plasticity -> not restricted to develop into a specific tissue
210
Muscle growth depends on:
1. Rate of muscle protein synthesis
2. Rate of muscle protein degradation
- varies in response to physiological demand
- reducing muscle degradation is key to improving muscle growth and efficiency in production
- muscle proteins turn over metabolically
