Fish Physiology Lecture 2 Some General Processes Feeding and Digestion Growth and Metabolism

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Fish PhysiologyLecture 2Some General
ProcessesFeeding and DigestionGrowth and
Metabolism

• Dr. Eric B. May

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Some General Processes

• The Root and Bohr Effect
• Charles and Boyles Laws
• Salting Out Effect
• Active Transport Mechanisms
• Membrane Transport of Macromolecules

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The Root and Bohr Effect
Root Effect Hb O2 Binding Capacity
100
Hb-O2 Saturation ()
Bohr Effect rbc intracellular pH and Hb O2
Affinity
0
Partial Pressure of O2
4
The Salting Out Effect
In cells the effect of salting out is usually
mediated by lactate which when increased in a
cell results in lower solubility of N2. The net
effect is that N2 comes out of solution and since
the gas laws apply is removed from the cell into
any open space even against pressure gradients.
C
N2
? Lactate
P
N2
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Charles Lawor Charles and Gay-Lussacs Law

• At constant pressure and moles there is a direct
  relation between temperature and volume of a gas
• V constantT or
• V/T k (constant)

Volume
Temperature
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Boyles Law

• At constant temperature and moles there is a
  direct relation between pressure and volume of a
  gas
• V constantP or
• V/P k (constant)

Volume
Pressure
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Active Transport Mechanisms

• A Cosymport or symport movement of ions or
  molecules via ionic gate or macromolecule
• B Antiport movement of ions or molecules via
  ionic gate or macromolecule

A
B
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Trans-Membrane Transport of Macromolecules

• 1 Attachement of molecule to receptor or surface
• 2 Involution of surface
• 3 Engulfment of molecule
• 4 Pinching off and import of macromolecule into
  the cell

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Feeding and Digestion
My Best Subject
Feeding
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Energy Budgets

• Intake ( I Income)
• Macronutrients
• Carbohydrates
• Fats/Oils
• Proteins
• Micronutrients
• Vitamins
• Essential
• Fatty Acids
• Amino Acids
• Sugars

• Energy Use (E Expenditure)
• Respiration
• Osmoregulation
• Movement
• Feeding
• Digestion
• Reproduction

IF I E Growth 0 I lt E Growth
I gt E Growth
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Diversity

• Again a Question of Adaptation
• Often Consumer and Consumed Co-Evolve
• Menhaden and Algae
• Striped Bass and Menhaden
• Driver of Speciation Exploitation of New Energy
  Resources

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Capture and Ingestion

• Jaw and Mouth Action
• Biting
• Blue fish Bite, Shear
• Eel Bite, Rotate, Tear
• Swallowing
• Striped Bass Engulf, Digest, Expell
• Ram Feeding
• Menhaden
• Whale Shark
• Suction Feeding
• Stone Rollers
• Chubs

Modification Nipping, Parrot Fish
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Body Shape

• Rover (Predators Usually)
• Sharks
• Bluefish
• Tunas
• Lie in Wait (Ambush Predators)
• Gar
• Pikes
• Barracudas
• Monkfish
• Anglerfish

Streamlined Torpedo Shape Body Caudal Fin
(BCF)

Rear Oriented Fins Instant Propulsion - BCF

Pelvics and Pectorals Push Off, Tail for
Propulsion
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Body Shape (Continued)

• Surface Oriented Fish
• Killifish
• Flying Fish
• Surface Filter Feeders
• Menhaden
• Bottom Fish
• Flat Fish
• Deep Bodied Fish
• Butterfly Fish
• Angel Fish
• Eel Like Fish
• Moray Eel
• American Eel

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Grouping by Diet

• Herbivores
• Phytoplankton
• Macrophytes
• Carnivores
• Zooplankton
• Selective (High Cost but Food Specific)
• Non-Selective (Low Cost but Non Specific)
• Benthic (Live in Water Column, but Feed Off
  Bottom)
• Fish Feeders (Ichthyvores or Piscivores)
• Detritivores

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Grouping by Diet (Continued)

• Usually a function of co-adaptation of mouth and
  digestive tract, ie
• Menhaden Gizzard, elongated large intestine
• Striped Bass Muscular stomach, short intestines
• Butterfly Fish Coiled small and large
  intestines

• Herbivores
• Detritivores
• Carnivores

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Feeding and Digestion
Eat your Veggies!
Digestion
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Digestion(Mechanical)

• Mechanical Jaws
• Winnowing Cichlids (Sort Chaff from Food)
• Flat Plate Jaws Grinding
• Short Teeth Grinding and Tearing
• Elongate Sharp Teeth - Shearing
• Mechanical Pharyngeal Jaws and Plates
• Gill Rakers - Sieving
• Gizzard Like Modifications - Menhaden

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The Gastrointestinal SystemThe Generalized Tract

• Serosa/Adventitia External Covering or Shared
  Connective Tissue
• Tunica Muscularis Circular and Longitudinal
  Muscle Masses
• Tunica Submucosa Connective Tissue, Vascular
  Supply, Nerves
• Tunica Mucosa Internal Lining, Absorptive
  Surface

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The Esophagus

• Serosa/Adventitia A transition
• Muscularis Muscles More Spiral and in
  Opposition
• SubMucosa Thin
• Mucosa Stratified squamous to cuboidal

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The Stomach- Anterior or Fundic

• Adventitia to Serosa
• Muscularis Arranged as Spiral Bands in
  Opposition
• Submucosa Thick
• Mucosa Cuboidal to Columnar with Deep Pits
  Lined by Parietal Cells Secrete HCl

Parietal Cell
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The Stomach Posterior or Cardiac

• Primarily Serosa
• Muscularis Spiral Bands in Opposition
• Submucosa Thick
• Mucosa Stratified Squamous

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Stomach - Modifications

• Agastric
• Short Straight Carnivores
• Long Straight Herbivores
• Simple - Carnivores
• Gastric
• Spiral Valves Elasmobranchs
• Cecate Herbivores
• Diverticulate Herbivores and Carnivores

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The Small Intestine

• Adventitia/Serosa Intermingled
• Muscularis Primarily Circular with External
  Longitudinal Bands
• Submucosa Thick with large arteries and veins
• Mucosa Divided into
• Limiting muscle band
• Lamina propria connective tissue and vascular
  supply
• Mucosa

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Small Intestine - Modifications

• Simple Insectivores Usually
• Elongate Complex Carnivores
• Spiral - Herbivores

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Large Intestine

• Serosa Primarily
• Muscularis Thin Circular, Longitudinal Muscle
  Bands
• Submucosa Moderate Thickness
• Mucosa Thin Muscularis Mucosa, Crypts Lined
  with Mucus Secreting Cells

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Digestion - Chemical
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Digestion Chemical (Continued)

• Stomach Acid Lysis, Acid Activiation of
  Pepsinogen
• Enzymatic Table 1, Previous Slide
• Anterior Small Intestine Site of Initiation
• Length of SI Related to
• Most Pancreatic Enzymes Operate at pH 7 9
• Bile Contains Bicarbonates to Buffer
• Cellulase Produed by Microbes and Larger Gut Size
  Produces Fermentation Vat
• Chitin also via Chitinase and Microbes producing
  N-acetyl-glucosamine

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Digestion - Chemical (Continued)
Fats Fatty Acids/Glycerols

• Enzymatic Variation Some
• Note Krebs Cycle is Main Exchange Point For
  Conversions and Energy Production

Proteins Ammino Acids
Volitile Fatty Acids
Complex Carbohydrates Simple
Sugars
Simple Sugars
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Digestion Chemical (Continued)

• Microbial
• Again View Relation to Gut Size
• Significance of Microbial Balance
• Tilapia
• Carp
• Temperature Effects Cold Temperatures Represent
  a Problem

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Absorption Lipids

• Lipids
• Bile Emulsification
• Absorption
• Conversion to Lipoproteins (Complex Aggregates of
  Macromolecules)
• Volatile Fatty Acids Directly Absorbed (Small
  Sized Molecules with polar/nonpolar groups

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Absorption (Continued)Absorption and
Mobilization of Fatty Acids
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Absorption (Continued)Carbohydrates

• Active Co-transport (Anti-port) of Simple Sugars
• Sodium Ion Moves out Passively in Response to
  Solute Gradient
• If Protein Gates Saturated no Futher Absorption
• Cellulose, Though Complex Carbohydrate is
  Fermented into Volatile Fatty Acids

Lumen
Cell
Monosaccharides
Sodium Ion
Protein is specific to Monosaccharide Type
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Absorption (Continued)Proteins

• Mono-peptides (Amino Acids)
• CoTransport (Antiport) via Na Linked System
• Movement Between Cells
• Di-peptides
• CoTransport (Antiport)
• Pinocytosis
• Poly-peptides
• Pinocytosis

Gut Lumen
Blood
Mono
Mono and Di
Di and Poly
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Issue of Ontogenic Shifts
Back to Normal
Getting Better
This aint right
Adult Juvenile
Larvae
Increasing Gape Size
Gut Maturation
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Energy Budgets

• Intake ( I Income)
• Macronutrients
• Carbohydrates
• Fats/Oils
• Proteins
• Micronutrients
• Vitamins
• Essential
• Fatty Acids
• Amino Acids
• Sugars

• Energy Use (E Expenditure)
• Respiration
• Osmoregulation
• Movement
• Feeding
• Digestion
• Reproduction

IF I E Growth 0 I lt E Growth
I gt E Growth
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A Transition Zone - Energetics
Hormonal Control
Excretion
Adsorption Renal Stomach Intestinal
Storage Lipid Carbohydrate
Mobilization Lipid Carbohydrate Protein
Ingestion
Growth
Reproduction
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Bioenergetics Models
Basic Bioenergetics Equation Consumption
Growth Respiration Waste or C G R
W Expanded Equation Consumption Growth
Standard Metabolism Activity Digestion
Feces Urine Or C G RS RA RD F U
Winberg Equation
G 2 RS
Consumption ------------------------
-
1 (RD F U) Production Based
Model Production (Over Specified Interval)
Growth (Over Interval) X Mean Biomass (Over
Interval Or P G . B)

P Applied to Cohorts Becomes
CTOT -------
G/C
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Bioenergetics (Continued)
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Energetics A Question of TemperatureFirst
Order Kinetic Equations for Enzyme Action
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Second Order Kinetic Equations
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Energetics (Continued)

• Proteins and Amino Acids
• Fish have higher protein requirements than
  terrestrial vertebrates (20 55 vs. 12 25)
• Carnivores High up to 60 of diet
• Low cost associated with homeothermy in cold
  temperature
• Ease of excretion
• Herbivores
• Can digestion protein
• But depending on experimental conditions growth
  vs. protein in diet will vary
• Limiting factor is essential amino acids

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Energetics Some Considerations

• Use of Fish Protein vs. Plant Protein
• Fish meal is becoming and issue
• Salmon offal often contains pathogens requiring
  pasteurization
• Examples
• Salmon use Salmon
• Tilapia use poultry waste
• Growth is Protein Based

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Constraints on Growth

• Food Quality
• Digestible vs. Indigestible
• Ratio
• Availability of Digestible
• Micro Macro Nutrient Ratio
• Prey Shifting
• Ontogenetic Shifts
• Food Quantity
• Prey Availability
• Herbivore Compensation
• Microbial Digestion to Produce VFAs

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Protein Based Energy AssimilationNature of Food
Invertebrates
Algae
Increasing Protein
Macrophytes
Detritus
Increasing Energy Assimilation
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Growth and Metabolism
So, this Is 2007
Im the 1984 Model
Weight
Length
Growth
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Growth SignificancePopulation Estimators
Fishing
Population Estimator Biomass
Recruitment
Growth
Mortality
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Growth (Continued)Descriptors

• Regression Models and Fit
• Condition Factor (K)
• RNADNA Ratios
• Hepato/Somatic Index
• Weight at Age
• Bioenergetics Model

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Regression Models and Fit
r2 .95
Weight
r2 .75
Transition 1980s to 2000s
Length
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Condition Factor
K W L-3 100
K Condition Factor W Weight L Length
Used to describe growth as a function of weight
length relationships. Is a linear model.
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RNADNA Ratios

• Assumption Growth is protein based, therefore
  an indirect measure of growth is the ratio of RNA
  to DNA, the greater the ratio the less the
  production of protein, hence growth. IE lower RNA
  indicates a lack of protein production

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Hepato-Somatic Index
Low Protein Synthesis

• Assumption Protein biosynthesis is largely
  mediated through the liver, hence increased
  demand for protein will be matched with and
  increase in liver volume.

Increased Protein Synthesis
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Weight at Age
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Growth Control

• Linear
• G Growth
• a Constant (growth rate of a 1 gm fish)
• W Fish Weight
• b weight exponent (-0.35 - -0.45)
• Asymptotic
• The real relationship

Weight
G a x Wb
Age
Weight
Age
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Growth Manipulation
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Growth ManipulationPurpose
Aquaculture vs. Restoration Fast
Growth Not Important Except for Juvenile
growth Sterility Promotes No (An
obvious) Diversion of Energy From Development of
Eggs and Sperm Docility Promotes No Need
Active Fish, Primarily Energy Conservation
for Foraging Growth
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Growth Issue of Markers

• Growth Juvenile Oyster Disease (JOD) Selection
  resulted in fast growth, allowing for spat to
  grow beyond the effects of infection, interpreted
  as increased resistance.
• Immune Response Rainbow trout selected for
  resistance to Enteric Redmouth, result was
  increased non-specific resistance, but not cell
  mediated resistance

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Metabolism Storage Sites

• Glycogen
• Liver, Brain
• Lipid/Fats
• Brain, Adipose Tissue, Liver, Red Muscle (Some
  Species)
• Proteins
• All Cells, Muscle

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Metabolism Products and ExchangesGlucose -
Glycogen
Liver As Glycogen

• Products Glycogen, branched complex
  carbohydrate, mobilized to blood as glucose a
  monosaccharide
• Glycogen Low storage amounts, short term
  solution to energy needs, rapidly depleted
• Dysfunctions Carbohydrate rich diets (gt20)
  result in glycogen liver syndrome, excess
  stimulation of gluconeogenic pathways results in
  same condition

Blood Glucose
Distribution to Organs
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Metabolism Products and ExchangesFats/Lipids
Liver Conversions via Krebs from AAs, Glucose,
FAs to FAs
Liver Formation of Lipoproteins
Blood Movement as FAs, Glycerol
TAG Lipase at Adipose
Adipose Release as Glycerol and FAs
Adipose Conversion to Mobile FA Form
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Metabolism Products and ExchangesFats/LipidsSo
me Considerations

• Triacylglycerol (TAG) Lipase and Insulin serve as
  key regulators for control, primarily anabolic
  pathway
• Fish (Carnivores for Sure) are Hyperinsulinemic
  (High Insulin)

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Metabolism Products and ExchangesFats/LipidsAn
omalies

• Starvation
• Insulin/Glucagon Balance shifts triggering
• Hormones sensitive lipases and glucocorticosteriod
  s
• Gluconeogenesis
• Elevated Proteolysis

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Starvation Continued

• Prolonged Starvation- Leads to Fatty Liver
  Syndrome and Ketosis Like Toxemia
• Generalizations
• High carbohydrate intake elevates enzymes,
  insulin and TAG Lipase
• Epidermal Growth Factor elevated, resulting in
  elevated brain storage of fats
• Growth hormone responds to intake

Acute vs. Chronic Chronic Protein Usage
Carbohydrate Sparing Chronic Decreased
Lipogenesis, Increased Lypolysis Acute
Above Reversed and Growth Hormone Acts Like
Insulin
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Metabolism Products and ExchangesProteins

• 1 Protein Recycling a Normal Internal Cellular
  Process
• 2 Net Growth Turnover and Degradation Balanced
  with or Less than Assimilation Providing Growth
• 3 Metabolic Maintenance Synthesis and
  Degradation are Balanced, Synthesis via all
  Routes
• Protein Degradation and Synthesis 1 , 2, 3 are
  Energy Dependent Pathways

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Metabolism Products and ExchangesProtein Aging

• Primary Dipeptide Bonds
• Secondary Hydrogen Bonds
• Tertiary Disulfide Bonds (ß Pleated and
  Globular
• Quaternary Disulfide Bonds (Usually Dimers and
  tetramers)

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Metabolism Products and ExchangesProtein Aging
Continued

• Processes
• Oxygen Radicals Break Disulfide and Hydrogen
  Bonds
• Deamination Break Amide Bonds
• Proteases (Ca Dependent, Leak from Lysosomes)
• Ubiquitin Attaches Protein, Complex Fuses with
  Lysosomes and Stored or Expelled, So Called Heat
  Shock Proteings
• High Glucose Increased Oxygen Radical Formation

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Metabolism Products and ExchangesProtein
Cycling

• Proteins Constantly Removed and Replaced
• 23 to 42 elevation of 02 consumption in Atlantic
  Cod a Carnivore
• 11 to 22 elevation of O2 consumption in Carp a
  Herbivore
• Tissue Demands (Table 2)
• Cyclohexamide synthesis 80 O2 consumption in
  hepatocytes
• Turnover rates vary high in hepatocytes, low in
  muscle
• Go Back to Synthesis

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Metabolism Products and ExchangesProtein
Synthesis

• The Process
• Transcription
• Translation
• Secondary Modification

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Metabolism Products and ExchangesProtein
Dynamics

• Muscle Primarily Post Mitotic, No Replacement
  with New Cells
• Serves as Primary Protein Storage Site
• While Protein Synthesis and Exchange are Low,
  Muscle Accounts for 50 to 80 of Body Mass
• Go to Table 2A (Atlantic Cod at 300g)

70
Metabolism Products and ExchangesProtein
Dynamics (Figure 2)
Synthesis
Protein Growth
Protein Synthesis
Growth
Consumption
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Metabolism Products and ExchangesProtein
Dynamics Related to Bioenergetics

• Basic Bioenergetics Equation
• Consumption Growth Respiration Waste or C
  G R W
• Expanded Equation
• Consumption Growth Standard Metabolism
  Activity Digestion Feces Urine
• Or C G RS RA RD F U
• Note RS, RA, RD are Specific Dynamic Action
  Therefore the equation could be presented as
• C G S F U S Specific Dynamic Action as
  Measured by O2 Uptake

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Metabolism Products and ExchangesProtein
Dynamics SDA Continued

• Considerations
• Specific Dynamic Action Function of
• Digestion
• Gut Motility
• Enzyme Synthesis
• Absorption
• Clear Link to Essential Amino Acids (EAAs)
• See Table 2B
• Protein Synthesis Linked to Precursors
• Gluconeogenesis and Lipogenesis Minor Processes
• EAAs are Limiting

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Metabolism Products and ExchangesProtein
Dynamics (Table 2B)
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Metabolism Products and ExchangesProtein
DynamicsOutcomes Due to Metabolic Shifts

• Energetics Related to Reproduction ie Vitellogen
  Production
• Response to Disease
• Cellular Response ie Oxidative Burst
• Antibody Production
• Contaminant Induction
• P450 Production Competes with Other Biosynthetic
  Pathways

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Control of Feeding

• Genotypic Influences
• Social Interactions Pecking Order
• Food Constituents EFAs
• Endogenous Factors Such as
• Cholecystokinin (CCK)
• Bombesin Gastrin releasing peptide
• Neuropeptides (Brain and Pancreas)
• NPY for example
• Not proven in fish, but known for mammals
• Can regulate growth via
• Stimulant
• Lignand of receptors for release of GH
• Stimulator for GH release via GnRH which
  stimulates somatotrophs

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Growth Hormone (GH)

• Single-chain peptide
• Produced and stored in somatotroph cells of the
  pituitary
• Similar to those of prolactin and somatolactin
  thus included in the GH/prolactin family of
  hormones
• Assumes central role in the growth of fish
• Has osmoregulatory function as well

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GH Continued
NPY GHRH GnRH

• Neuropeptide Y (NPY), Growth hormone releasing
  hormone (GHRH) and Gonadotropin releasing hormone
  (GnRH) major stimulating hormones
• Somatotropin release-inhibiting factor major
  inhibiting hormone
• Se figure 3 for other factors influencing the
  release of GH

Somatotroph Cell of Pituitary
GH Release
-
SRIF
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GH Continued

• Patterns of Release
• Pulse as in Carp
• Episodic as in Trout
• Diurnal as in mammals?
• Degradation
• Short lived 10 to 45 minutes depending of fish
  species
• Responds to physiological state of the fish
• Stress increases production

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Physiological Response to GHStarvation

• Starved fish have higher GH levels than fed
• Both fed and starved will show a persistent
  decreased GH in response to cortisol levels in
  short term stress situations
• Chronic stress results in elevated GH levels
• Example Yearling Coho salmon, held in fresh
  have depressed GH

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GH in Mammals

• GH secretion amplitude (amount) and frequency
  dictate level of activity
• Number of receptors regulate level of action
• Number of receptors are under feed back to GH
  level
• GH binding protein serves a reservoir for GH

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Tissue Action of GH
Liver Increase Activity Related to Protein, Fat
and Carbohydrate Utilization
Miss Me?
Muscle Increased Biosynthesis
Intestine Increase in Amino Acid Mobilization
and Protein Synthesis
Kidney Increase GH Receptors, Cell Volume and
Osmoregulation
Thyroid Increased T4 Release
Cartilage Increased Proteoglycan synthesis and
Sulfate Uptake