BASAL GANGLIA
B
SYMPTOMS
The majority of basal cell carcinomas
occur on the face, often at the side of an
eye or on the nose. It starts as a small,
flat nodule and grows slowly, eventually
breaking down at the centre to form a
shallow ulcer with raised edges.
Diagnosis is confirmed through a
biopsy (removal of a small sample of
cells for microscopic analysis). Without
treatment, the tumour gradually invades
and destroys the surrounding tissues,
but it virtually never spreads to other
parts of the body.
TREATMENT
Treatment of basal cell carcinoma is
usually with surgery (or in some cases
radiotherapy)
and is often completely
successful.
Plastic surgery
may also be
required, however, depending on the
size and site of the tumour.
PREVENTION
The risk of developing this form of skin
cancer can be reduced by avoiding over-
exposure to strong sunlight, by using
sunscreens,
and by wearing protective
clothing such as sun hats. People who
have previously had a basal cell carcin-
oma may develop further tumours and
should be especially alert to any new
changes in their skin. (See also
melan-
oma, malignant; squamous cell carcinoma;
sunlight, adverse effects of.)
basal ganglia
Paired nerve cell clusters deep within
the cerebrum (the main mass of the
brain)
and the upper part of the brain-
stem. The basal ganglia play a vital part
in producing smooth, continuous mus-
cular
actions
and
in
stopping
and
starting
movement.
Any
disease
or
degeneration affecting the basal ganglia
and their connections may lead to the
appearance of involuntary movements,
trembling, and weakness, as occur in
Parkinson’s disease.
basal metabolic rate (BMR)
The rate at which energy is used by the
body just to maintain vital functions.
Such vital functions include breathing,
circulation,
and digestion.
(See
also
energyrequirements
;
metabolism
).
base
See
alkali.
basement membrane
The thin membrane that lies directly
beneath the
epithelium
(the layer of cells
that covers surfaces of the body and
lines most hollow structures within it).
The basement membrane is composed
of protein fibres and carbohydrates.
base pair
Part of a
DNA
molecule comprising two
chemicals known as nucleotide bases
that are linked together by means of
hydrogen bonds. A base pair forms one
“rung” of the DNA “ladder”. There are
only two possible pairings of the four
bases: guanine always pairs with cyto-
sine and adenine with thymine. The
sequence of base pairs in each DNA
chain provides the code for the activi-
ties of the cell (see
genetic code).
(See
also
nucleic acids.)
basic life support
Resuscitation techniques that may be
performed by a first aider (see
rescue
breathing
;
cardiopulmonary resuscitation
).
If basic life support measures fail to
restore a normal heartbeat and sponta-
neous breathing,
advanced life support
must then be administered by trained
medical personnel.
basilar membrane
A membrane within the cochlea (the
inner
ear
structure containing the recep-
tor for hearing). Sound waves cause the
basilar membrane to vibrate, stimulat-
ing sensory hair cells to send electrical
signals to the brain.
basophil
A type of
white blood cell
that plays a part
in inflammatory and allergic reactions.
Batten’s disease
One of a group of hereditary metabolic
diseases (see
metabolism, inborn errors
of)
to which
Tay-Sachs disease
also
belongs. In Batten’s disease, abnormal
fatty substances accumulate in the cells
of the
nervous system,
causing progres-
sive dementia, worsening seizures, and
loss of vision. Symptoms of the condi-
tion usually first appear during early
childhood.
There is no known treatment for Bat-
ten’s disease, which is generally fatal
during childhood.
Bazin’s disease
A rare disorder, mainly affecting young
women,
in
which
tender
swellings
develop under the skin in the calves. In
most cases no cause can be found,
although Bazin’s disease may sometimes
be linked to
tuberculosis.
B-cell
See
B-lymphocyte.
BCG vaccination
A vaccine that gives immunity against
tuberculosis.The
BCG vaccine is prepared
from an artificially weakened strain of
bovine (cattle) tubercle bacilli, the rod-
shaped
bacteria
that are responsible for
causing tuberculosis. The letters BCG
stand for
“bacille
Calmette-Guerin”,
after the two men who developed the
tuberculosis vaccine.
WHY IT IS DONE
The BCG vaccine is given to people who
are at risk of tuberculosis and to those
whose tuberculin test is negative, indi-
cating that they are likely to have no
immunity to the disease. People at risk
include health workers, contacts of peo-
ple with tuberculosis, and immigrants
from countries where there is a high
rate of tuberculosis. Infants born to
immigrants in this category are immu-
nized, without having a tuberculin test,
within a few days of birth. The vaccine
is also recommended for children aged
10 to 14 years for whom the tuberculin
test is negative.
HOW IT IS DONE
The vaccine is usually injected into the
upper arm. About six weeks later, a
small pustule appears. This normally
heals completely, leaving a small scar,
but can occasionally develop into a
chronic
ulcer
(open sore).
Becker’s muscular dystrophy
A type of
muscular dystrophy.
beclometasone
A
corticosteroid drug
that is used in the
treatment of
asthma
and hay fever (see
rhinitis, allergic).
When prescribed as a
nasal spray, beclometasone controls the
symptoms of these conditions by redu-
cing inflammation and the production
of mucus in the lining of the nose. Pre-
scribed as an inhaler for the treatment
of asthma, the drug reduces inflamma-
tion of the airways, thereby controlling
wheezing and coughing.
Beclometasone is often given with
bronchodilator drugs
in the management
of asthma. A severe asthma attack may
require the dose to be increased. The
action of beclometasone is slow, how-
ever, and its full effect takes several days
to occur. Possible adverse effects of the
drug include hoarseness, throat irrita-
tion, and, on rare occasions, fungal
infections in the mouth.
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