DLE
DONOR
clear up after taking a few deep breaths
or after resting for a short time. Severe,
prolonged, or recurrent dizziness should
be investigated by a doctor. Treatment
depends on the underlying cause.
DLE
Discoid
lupus erythematosus
.
DM SA scan
A type of
kidney imaging
technique (see
radionuclide scanning)
.
DNA
The abbreviation for deoxyribo-
nucleic acid, the principal molecule
carrying genetic information in almost
all organisms; the exceptions are cer-
tain viruses that use
RNA
.
DNA is found
in the
chromosomes
of cells; its double-
helix structure allows the chromosomes
to be copied exactly during the process
of cell division. (See also
nucleic acids
.)
DNA
DNA fingerprinting
See
genetic fin-
gerprinting
.
dogs, diseases from
Infectious or par-
asitic diseases that are acquired from
contact with dogs. They may be caused
by viruses, bacteria, fungi, protozoa,
worms, insects, or mites living in or on a
dog. Many parasites that live on dogs can
be transferred to humans. The most seri-
ous disease from dogs is
rabies
.
The UK
is free of rabies, but travellers to coun-
tries in which rabies exists should treat
any bite with suspicion. Dog bites can
cause serious bleeding and shock and
may become infected.
Toxocariasis
and
hydatid disease
are potentially serious
diseases caused by the ingestion of
worm eggs from dogs. In the tropics,
walking barefoot on soil that is contam-
inated with dog faeces can lead to dog
hookworm infestation
.
Bites from dog
fleas
are an occasional
nuisance.
Ticks
and
mites
from dogs,
including a canine version of the
scabies
mite, are other common problems. The
fungi that cause
tinea
infections in dogs
can be caught by humans.
Some people become allergic to ani-
mal
dander
(tiny scales from fur or
skin). They may, for example, have asth-
ma or urticaria when a dog is in the
house. (See also zoonoses.)
dominant
A term used in
genetics
to
describe one of the ways in which a
gene
is passed from parent to offspring. Many
characteristics are determined by a single
pair of genes,
1
of each pair being inherit-
ed from each parent. A dominant gene
overrides an equivalent
recessive
gene.
For example, the gene for brown eye
colour is dominant, so if a child inherits
the gene for brown eyes from
1
parent
and the gene for blue eyes from the other,
he or she will have brown eyes. Some
genetic disorders are determined by a
dominant gene. Examples include
Mar-
fan's syndrome
and
Huntington's disease
.
The child will have the disease if he or she
inherits the gene from
1
or both parents.
domperidone
An
antiemetic drug
used
to relieve nausea and vomiting associ-
ated with some gastrointestinal disorders
or during treatment with certain drugs or
radiotherapy
. Adverse effects may in-
clude breast enlargement and secretion
of milk from the breast.
donor
A person who provides blood for
transfusion, tissues or organs for trans-
plantation, eggs, or semen for artificial
insemination. The organs most frequently
donated are kidneys, corneas, heart,
lungs, liver, and pancreas. Certain organs
can be donated during a person's life-
time; some are only used following
brain
death
. All donors should be free of can-
cer, serious infection (such as hepatitis
B), and should not carry
HIV
.
Organs for
transplantation must be removed within
a few hours of brain death, and before or
immediately after the heartbeat has
stopped. In some kidney transplants, the
kidney is provided by a living donor,
usually a relative whose body tissues
match well on the basis of
tissue-typing
.
Suitable related donors may also pro-
vide bone marrow for transplantation
179
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