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Haldane effect: In the presence of oxygen, less carbon dioxide binds in
the blood because when oxygen combines with hemoglobin, the hemoglobin
becomes a stronger acid, which combines with less carbon dioxide.
Haploid:
Having half the number of chromosomes characteristically found in the
somatic cells of an organism; characteristic of mature gametes.
Hartnup's disease:
a genetic disorder resulting in
defective absorption of the amino acid, tryptophan.
HDL:
high density
lipoproteins. HDL transport cholesterol from the tissues to the liver where
it can be eliminated in bile. HDL-cholesterol is considered good
cholesterol, because higher blood levels of HDL-cholesterol are associated
with lower risk of heart disease.
Heme:
compounds of iron complexed in a
characteristic ring structure known as a porphyrin ring.
Hemodialysis:
a medical procedure that uses a
specialized machine to filter waste products from the blood, while restoring
its normal constituents. Hemodialysis is needed to perform the work of the
kidneys if they can no longer function effectively.
Hemoglobin:
the oxygen-carrying pigment in
red blood cells.
Hemolysis:
rupture of red blood cells.
Hemolytic anemia:
Anemia resulting from hemolysis
(the rupture of red blood cells).
Hemorrhage:
excessive or uncontrolled
bleeding.
Hepatic:
Refers to the liver.
Hepatitis:
literally, inflammation of the
liver. Hepatitis caused by a virus is known as viral hepatitis. Other causes
of hepatitis include toxic chemicals and alcohol abuse.
Hereditary spherocytosis:
a hereditary form of anemia
characterized by abnormally shaped red blood cells which are spherical and
abnormally fragile. The increased fragility of these red blood cells leads
to hemolytic anemia (anemia caused by the rupture of red blood cells).
Heterodimer:
a dimer or complex of two
different molecules, usually proteins.
Heterozygous:
possessing two different forms
(alleles) of a specific gene.
HIV:
human
immunodeficiency virus. The virus that causes AIDS.
Homocysteine:
a sulfur-containing amino acid,
which is an intermediate in the metabolism of another sulfur-containing
amino acid, methionine. Elevated homocysteine levels in the blood have been
associated with increased risk of cardiovascular disease.
Homodimer:
a dimer or complex of two of the
same molecule, usually a protein.
Homologous:
having the same relative
position, value, or structure.
Homozygous:
possessing two identical forms
(alleles) of a specific gene.
Hormone:
a chemical secretion released by a gland
or a tissue, which affects or regulates the activity of specific cells or
organs. Complex bodily functions, such as growth and sexual development,
are regulated by hormones.
Human
growth hormone (HGH): Hormones secreted by the anterior pituitary gland
that stimulates growth of body tissues, especially skeletal and muscular
tissues. Also known as somatotropin and somatotropic hormone
(STH).
Huperzine-A:
(Main function: acetylcholine esterase inhibitor) (Pronunciation: hoo-PEHR-zeen). Huperzine is an alkaloid found in the club moss, Huperzia serrata – a plant
used in Chinese traditional medicine. Huperzine is a potent inhibitor of the
enzyme that disposes of acetylcholine in the brain; it therefore elevates
acetylcholine levels. When taken orally, huperzine has shown a high
bioavailability and rapid penetration into the brain. Side effects are
minimal at therapeutic doses. Huperzine exhibits memory-enhancing activities
in animals and humans. Its benefits are said to include increased alertness,
greater short-term memory retention and increased energy.
Huperzine shows promise for treating Alzheimer’s disease and other dementias
because: It reduces oxidative damage
produced by beta-ameloid protein (a protein overproduced in Alzheimer’s brains); It elevates acetylcholine levels
that are typically depleted by Alzheimer’s; It has demonstrated ability to
enhance memory; It has a longer duration of action
and higher therapeutic index than tacrine and donepezil (the best FDA-approved Alzheimer’s drugs).
Read more...
Hydroxyapatite:
a calcium phosphate salt.
Hydroxyapatite is the main mineral component of bone of bone and teeth, and
is what gives them their rigidity.
Hydroxylation:
a chemical reaction involving the
addition of a hydroxyl (-OH) group to a compound.
Hyperparathyroidism:
excess secretion of parathyroid
hormone by the parathyroid glands resulting in the disturbance of calcium
metabolism. Symptoms may include increased blood levels of calcium (hypercalcemia),
decreased blood levels of phosphorus, loss of calcium from bone, and kidney
stone formation.
Hypertension:
high blood pressure, defined as a
systolic blood pressure greater than 140 mm Hg and/or diastolic blood
pressure greater than 90 mm Hg.
Hyperthyroidism:
an excess of thyroid hormone
which may result from an overactive thyroid gland or nodule, or from taking
too much thyroid hormone.
Hypoparathyroidism:
a deficiency of parathyroid
hormone, which may be characterized by low blood calcium levels (hypocalcemia).
Hypothalamus:
An area at the base of the brain
that regulatesbodily functions, such as body temperature, hunger, and
thirst.
Hypothesis:
an educated guess or proposition
that is advanced as a basis for further investigation. A hypothesis must be
subjected to an experimental test to determine its validity.
Hypothyroidism:
a deficiency
of thyroid hormone which is normally made by the thyroid gland, located in
the front of the neck.
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