CLONE
COARCTATION OF THE AORTA
to prevent and treat epileptic fits (see
epilepsy
).
It also prevents
petitmal
attacks
in children. Side effects include drowsi-
ness, dizziness, fatigue, and irritability.
clone
An exact copy. In medicine, the
term usually refers to copies of cells,
genes, or organisms. Clones of cells are
all descended from one original cell. In
many types of cancer, cells are thought
to be derived from one abnormal cell.
Clones of genes are duplicates of a sin-
gle gene. In research, several copies of a
gene can be made to enable the gene to
be studied in detail. Clones of organ-
isms are produced by removing the
nuclei from cells of a donor individual
and transplanting them into the egg
cells of another individual. When the
eggs mature into living plants or ani-
mals, they are all identical to the donor.
clonidine
An
antihypertensive drug
used
to reduce high blood pressure. Possible
side effects include drowsiness, dizziness,
dry mouth, and constipation. Abrupt
withdrawal of high doses can cause a
dangerous rise in blood pressure.
clonus
A rapid series of abnormal
mus-
cle
contractions that occur in response
to stretching. Clonus is a sign of dam-
age to nerve fibres that carry impulses
from the motor cortex in the
cerebrum
to a particular muscle. It is also a fea-
ture of seizures in grand mal
epilepsy
.
clostridium
Any of a group of rod-
shaped
bacteria
. Clostridia are found in
soil and in the gastrointestinal tracts of
humans and animals. They produce
powerful toxins and are responsible for
potentially
life-threatening
diseases
such as
botulism
,
tetanus
,
and
gangrene
.
clotrimazole
A drug used to treat yeast
and fungal infections, especially c
an-
didiasis
(see
antifungal drugs
).
clove oil
An oil distilled from the dried
flower-buds of
EUGENIA CARYOPHYLLUS
,
used mainly as a flavouring in pharma-
ceuticals. Clove oil is sometimes used
to relieve abdominal pain due to
flatu-
lence
and as a remedy for toothache.
cloxacillin
A penicillin-type antibiotic
used to treat infections with staphylo-
coccal bacteria (see
penicillin drugs
).
clubbing
Thickening and broadening of
the tips of the fingers and toes, usually
with increased curving of the nails. It is
associated with chronic lung diseases,
such as
lung cancer
,
bronchiectasis
, and
fibrosing
alveolitis
;
with certain heart
abnormalities; and, occasionally, with
Crohn's disease
and
ulcerative colitis
.
club-foot
A deformity of the foot, pre-
sent from birth (see
talipes
).
cluster
headaches
Brief but severe
headaches that recur up to several times
a day over a few days. Cluster head-
aches affect one side of the head or
face. The cause is uncertain but they
may be due to dilation of blood vessels
in the brain as in
migraine
.
Beta-blocker
drugs
may be given to reduce the sever-
ity and frequency of cluster headaches.
CNS
An abbreviation for
central nervous
system
(the brain and spinal cord).
CNS stimulants
Drugs that increase
mental alertness (see
stimulant drugs)
.
coagulation, blood
The main mecha-
nism by which blood clots are formed,
involving a complex series of reactions
in the blood
plasma
(see
blood clotting
).
coal tar
A thick, black, sticky substance
distilled from coal. It is a common
ingredient of ointments and medicinal
shampoos prescribed for skin and scalp
conditions such as
psoriasis
and some
forms of
dermatitis
and
eczema
.
co-amoxiclav
A
penicillin drug
containing
a mixture of
amoxicillin
and clavulanic acid.
Because it is a more powerful antibiotic
than amoxicillin alone, co-amoxiclav is
used to treat infections caused by
amoxicillin-resistant strains of bacteria.
coarctation of the aorta
A
congenital
heart defect of unknown cause, in which
there is narrowing in a section of the
aorta
that supplies blood to the lower
body and legs. In response, the heart
has to work harder, causing
hyperten-
sion
in the upper part of the body.
Symptoms usually appear in early child-
hood and include headache, weakness
after exercise, cold legs, and, rarely,
breathing difficulty and swelling of the
legs due to
heart failure
. Associated
abnormalities include a heart
murmur,
weak or absent pulse in the groin, lack
of synchronization between groin and
wrist pulses, and higher blood pressure
in the arms than in the legs. X-rays con-
firm the diagnosis. Corrective surgery is
usually performed at 4-8 years of age.
C
133
previous page 131 BMA Illustrated Medical Dictionary read online next page 133 BMA Illustrated Medical Dictionary read online Home Toggle text on/off