الجمعة، 16 يناير 2009
الأحد، 11 يناير 2009
OSMOTIC FRAGILITY TEST
Osmotic Fragility Test (OFT)
A measure of the RBCs resistance to haemolysis by osmotic stress, depending primarily on the volume of the cell, the surface area and the cell's membrane function
RBCs are incubated in varying concentrations of a hypotonic solution of sodium chloride (NaCl)
As the concentration of NaCl decreases, cells take on water to produce osmotic equilibrium
Normal cells begin to haemolyse at NaCl concentrations of approximately 0.50%
Because of their Dec. surface area:volume, spherocytes can not expand as much as normal discoid cells, thus lysis is usually completed by 0.4-0.5%, starting at higher NaCl concentrations
Incubation of blood overnight at 37oC makes the OFT more sensitive
A measure of the RBCs resistance to haemolysis by osmotic stress, depending primarily on the volume of the cell, the surface area and the cell's membrane function
RBCs are incubated in varying concentrations of a hypotonic solution of sodium chloride (NaCl)
As the concentration of NaCl decreases, cells take on water to produce osmotic equilibrium
Normal cells begin to haemolyse at NaCl concentrations of approximately 0.50%
Because of their Dec. surface area:volume, spherocytes can not expand as much as normal discoid cells, thus lysis is usually completed by 0.4-0.5%, starting at higher NaCl concentrations
Incubation of blood overnight at 37oC makes the OFT more sensitive
السبت، 10 يناير 2009
mucopolysaccharidosis
MPS are hereditary progressive disorders due to gene mutation of lysosomal enzymes needed to degrade GAGS..
GAGS:
Long chain complex carbohydrate
GAGS:
Long chain complex carbohydrate
.
The major GAGS are chondroitin-4-sulfate, chondroitin-6-sulfate, dermatan sulfate, heparin sulfate, keratan sulfate, hyaluronan
The major GAGS are chondroitin-4-sulfate, chondroitin-6-sulfate, dermatan sulfate, heparin sulfate, keratan sulfate, hyaluronan
.
Theses substances are synthesized and linked to proteins to form proteoglycans (major constituents of connective tissue, nuclear and cell membranes
Theses substances are synthesized and linked to proteins to form proteoglycans (major constituents of connective tissue, nuclear and cell membranes
)
Degradation start with removal of protein part then digestion of Gags.
Failure of GAGS degradation leads to intralysosomal accumulation of GAGS fragments interfering with cell function
MPS are autosomal recessive except Hunter disease which is X linked recessive.
The most common types are MPS III followed by MPS I and MPS II
Degradation start with removal of protein part then digestion of Gags.
Failure of GAGS degradation leads to intralysosomal accumulation of GAGS fragments interfering with cell function
MPS are autosomal recessive except Hunter disease which is X linked recessive.
The most common types are MPS III followed by MPS I and MPS II
الجمعة، 9 يناير 2009
G6PD ENZYME
The G6PD enzyme catalyzes the oxidation of glucose-6-phosphate to 6-phosphogluconate while concomitantly reducing the oxidized form of nicotinamide adenine dinucleotide phosphate (NADP+) to nicotinamide adenine dinucleotide phosphate (NADPH). NADPH, a required cofactor in many biosynthetic reactions, maintains glutathione in its reduced form.
Reduced glutathione acts as a scavenger for dangerous oxidative metabolites in the cell. With the help of the enzyme glutathione peroxidase, reduced glutathione also converts harmful hydrogen peroxide to water. Red blood cells rely heavily upon glucose-6-phosphatase dehydrogenase (G6PD) activity because it is the only source of NADPH that protects the cells against oxidative stresses; therefore, people deficient in glucose-6-phosphatase dehydrogenase (G6PD) are not prescribed oxidative drugs, because their red blood cells undergo rapid hemolysis under this stress.
Reduced glutathione acts as a scavenger for dangerous oxidative metabolites in the cell. With the help of the enzyme glutathione peroxidase, reduced glutathione also converts harmful hydrogen peroxide to water. Red blood cells rely heavily upon glucose-6-phosphatase dehydrogenase (G6PD) activity because it is the only source of NADPH that protects the cells against oxidative stresses; therefore, people deficient in glucose-6-phosphatase dehydrogenase (G6PD) are not prescribed oxidative drugs, because their red blood cells undergo rapid hemolysis under this stress.
الأحد، 4 يناير 2009
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