General pathophysiology - metabolism Flashcards
pseudo-ruminant
is a classification of animals based on their digestive tract differing from the ruminants. Hippopotami and camels are ungulate mammals with a three-chambered stomach (ruminants have a four-chambered stomach) while equids and rhinoceroses are monogastric herbivores.
Like ruminants, some pseudoruminants may use foregut fermentation to break down cellulose in fibrous plant species (while most others are hindgut fermenters with a large cecum).
rabbits, guinea pigs, horses
Protein digestion begins in the stomach with the action of an enzyme called
Secreted by what cells?
pepsin
Pepsin is an endopeptidase that breaks down proteins into smaller peptides.
Gastric chief cells secrete pepsin as an inactive zymogen called pepsinogen.
Almost all the plasma proteins are synthesized in the liver with the exception of
immunoglobulins, which are synthesized by plasma cells.
The metabolism of plasma proteins also mainly occurs in the liver.
The functions of proteins in cells and tissues
A. Physical/Structural
B. Biochemical
C. Anti-infective agents
D. Liver and muscle proteins are energy and nitrogen reserves
- The functions of soluble proteins in the extracellular space
A. Physical (Maintenance of the viscosity of body fluids (plasma, secretions; Generating oncotic pressure of body fluids)
B. Biochemical (buffering, enzyme, transport etc.)
- Humoral protection against infection (Ig)
The average half-life of proteins is about
80 days, while that of the bone marrow, liver, kidneys and plasma is 10 days.
It is considerably shorter in muscle, skin, collagen and bone tissue as well as in the haemoglobin of mature erythrocytes.
trypsin
proteolytic enzyme produced in the pancreas in the precursor form of inactive trypsinogen.
Trypsin is an enzyme in the first section of the small intestine that starts the digestion of protein molecules by cutting long chains of amino acids into smaller pieces.
chymotrypsin
is a digestive enzyme synthesized in the pancreas that plays an essential role in proteolysis, or the breakdown of proteins and polypeptides.
As a component in the pancreatic juice, chymotrypsin aids in the digestion of proteins in the duodenum by preferentially cleaving peptide amide bonds.
carboxypeptidase
pancreatic enzyme
is a protease enzyme that hydrolyzes (cleaves) a peptide bond at the carboxy-terminal (C-terminal) end of a protein or peptide.
This is in contrast to an aminopeptidases, which cleave peptide bonds at the N-terminus of proteins.
aminopeptidases
are enzymes that catalyze the cleavage of amino acids from the amino terminus (N-terminus) of proteins or peptides (exopeptidases).
dipeptidases
are enzymes secreted by enterocytes into the small intestine. Dipeptidases hydrolyze bound pairs of amino acids, called dipeptides.
Dipeptidases are secreted onto the brush border of the villi in the small intestine, where they cleave dipeptides into their two component amino acids prior to absorption.
Nitrogen balance =
the difference between the total nitrogen intake by an organism and its total nitrogen loss.
Organisms have no stores of amino acids, therefore the magnitude of the nitrogen balance is determined by the difference between synthesis and breakdown of proteins.
Protein metabolism is affected by dietary and hormonal factors.
Positive nitrogen balance
This means that the intake of nitrogen into the body is greater than the loss of nitrogen from the body, so there is an increase in the total body pool of protein.
Predominance of anabolic processes is related to the action of androgen and
(o)estrogen hormones, insulin and somatotropin.
Negative nitrogen balance
This means that the amount of nitrogen excreted from the body is greater than the amount of nitrogen ingested.
Catabolic processes are related to the action of cortisol , thyroxine and progesterone.
Negative nitrogen balance is associated with burns, serious tissue injuries, fever, hyperthyroidism, wasting diseases, and during periods of fasting.
Endogenous protein reserve is
a labile (metabolisable, easily mobilisable) protein fraction of the organism.
Such protein will be used as a source of nitrogen in case the diet does not provide adequate protein, and will be restored as soon as the protein content in the diet is sufficient.
Reserves of nitrogenous compounds are primarily created by the liver, gastrointestinal wall and muscle tissue. In fattening bulls, such protein reserves comprise about 5% of the total proteins of the organism.
up to 25% of body protein can be lost before fatal or extreme adverse effects
PROTEINEMIA
The presence of protein in the blood.
The blood plasma/serum protein concentration of production animals generally ranges between 50 and 90 g/l, depending on the species, breed, age and diet as well as the fluctuations in the volume of protein and plasma.
Relative hypoproteinemia
Hypoproteinemia is a condition where there is an abnormally low level of protein in the blood.
Relative hypoproteinemia is occurs when plasma protein concentrations are lower than normal, but the absolute content of protein in the vascular space is normal. This is a dilutional hypoproteinemia and is attributable to either excessive fluid therapy or excessive water intake.
Hyperthyreosis
another word for hyperthyroidism
Hyperthyreosis is characterized by an increase in the activity of the thyroid gland. Enlargement of the thyroid gland is known as thyroid goiter.
hydremia
an abnormally watery state of the blood.
Relative hyperproteinemia
= decrease in the volume of plasma – dehydration (exicosis = loss of fluid)
e.g.
-Deprivation of water, water starvation
-Chronic diarrhea
-Excessive sweating (hyperhidrosis)
Absolute hyperproteinemia
means you have abnormally high levels of protein in your blood plasma.
- γ- globulinemia due to infection
- β- and γ-globulinemia due to tissue breakdown
Absolute hypoproteinemia
Absolute hypoproteinemia occurs when there is a reduction in the amount of plasma proteins in the vascular space in the presence of normal or almost normal plasma volume.
The reduced protein concentration can be the result of impaired production or accelerated loss.
- Loss due to blood loss, formation of exudate
and transudate - Protein deficiency/starvation
- Decline in synthesis (liver
diseases/damage, endocrine disorders) - Loss of plasma proteins due to proteinuria, enteritis, obstruction of lymphatic drainage and increased venous pressure
(BLOOD) PLASMA PROTEIN CONCENTRATIONS IN DOGS AND CATS, g/l
54-78 g/L
(BLOOD) PLASMA PROTEIN CONCENTRATIONS IN large ANIMALS, g/l
horses, pigs, cows
52 - 89 g/L
Albumin is ?
Approximately ?% of albumin is in the intracellular/extravascular space.
the main protein in blood plasma; also present in milk.
Its half-life is inversely proportional to the plasma albumin concentration
(that is, a decreased albumin content results in increased half-life, whereas increasing albumin concentrations cause the metabolic rate to increase by up to 50%).
Approximately 60% of albumin is in the intracellular/extravascular space.
Reduction in the plasma albumin levels results in the reabsorption of albumin into blood. Interstitial albumin acts as a (pH) buffer.
Decreased osmotic pressure in the interstitial space and plasma
stimulates
stimulates albumin synthesis
Immunoglobulins, also known as antibodies, are
glycoprotein molecules produced by
plasma cells
The primary factor that controls immunoglobulin
synthesis is
antigenic stimulation:
describe dysproteinemia
is a clinical state characterized by abnormal, often excessive, synthesis of immunoglobulin (Ig) molecules or subunits. Dysproteinemia results from clonal proliferation of plasma cells or B lymphocytes.
Acute inflammatory dysproteinemia
- Causes tissue damage of different origins
- The shifts are quantitatively related to the stage of development/progress and expression of the disease
- Variations in the plasma protein concentrations are the result of the changes in the synthesis rate, whereas increase and decrease in concentrations are in equilibrium.
3 points about chronic inflammatory dysproteinemia
- Occurs in the chronic stage of inflammation, in the case of malignant tumours and liver diseases.
- Involves an in crease in the levels of immunoglobulins usually along with hyperproteinemia. Levels of different immunoglobulin classes increase differently.
- It is arguable whether the changes in the plasma protein patterns are disease-specific or not.
*Increased oncotic pressure inhibits
albumin synthesis.
*Albumin synthesis depends on appropriate supply of amino acids and energy.
Urea is
the major end product of nitrogen metabolism. The urea cycle describes the conversion reactions of ammonia into urea, these reactions occur in the liver.
Uric acid / Creatinine / Indican
Indican
Indican is a tryptophan metabolite that is excreted mostly in the feces but also in small amounts in the urine as a result of absorption and detoxification of indole produced by bacterial action on tryptophan in the intestines.
The presence of indican in the urine indicates amino acid malabsorption.
Normal BUN range in farm animals
blood urea nitrogen 3.3–6.7 mmol/L
Increase in BUN may be due to (4)
- Liver diseases; fever
- Abnormal losses of fluids and electrolytes (ileus, diarrhoea, sweating, extensive burns) lead to dehydration of tissues and intensification of lytic processes in tissues
- Kidney disorders may cause 2–10-fold increase – retentional hyperazotemia
- Mechanical damage of tissues – productional hyperazotemia
Increase in BUN causes autointoxication or uremia.
azotemia
high concentrations of N compounds in blood
can be pre-renal, renal or post-renal
can lead to uremia
creatinine
metabolic nitrogen product
is a breakdown product of creatine phosphate from muscle and protein metabolism. It is released at a constant rate by the body.
isosthenuria
refers to the excretion of urine whose specific gravity is neither greater nor less than that of protein-free plasma, typically 1.008-1.012.
Isosthenuria reflects damage to the kidney’s tubules or the renal medulla.
causes of pre-renal azotemia (5)
dehydration
heart dieases (hypotension - low filtration rate)
shock
a diet rich in protein (only elevated BUN)
bleeding in the GI tract (only elevated BUN)
(When GI bleeding occurs, the blood is digested to protein. This protein is transported to the liver via the portal vein, and metabolized to BUN in the urea cycle. Higher BUN values are therefore associated with the digestion of blood.)
causes of renal azotemia
renal failure
causes of post-renal azotemia
urinary tract obstruction
bursting of the bladder
uremia
is the term for high levels of urea in the blood.
Uremia is often a sign of end-stage renal (kidney) disease and typically preceded by azotemia.
“Azotemia is a similar, less severe condition with high levels of urea, where the abnormality can be measured chemically but is not yet so severe as to produce symptoms. Uremia describes the pathological and symptomatic manifestations of severe azotemia.”
if there are no clinical signs, only azotemia, then the patient is not considered
uremic
what are the most imporant substrates for proteins.
amino acids
can also serve as an energy source via oxidation of their carbon chain