AFFECTIVE DISORDERS
AGGREGATION, PLATELET
in
moods
may
have
an
affective
disorder.
Shallow or reduced affect may
be a sign of
schizophrenia
or of an
organic
brain syndrom e
.
affective
disorders
Mental illnesses
characterized predominantly by marked
changes in
affect
. Mood may vary over a
period of time between
mania
(extreme
elation) and severe
depression.
(See
also
manic-depressive illness.)
affinity
A term used to describe the
attraction between chemicals that causes
them to bind together, as, for example,
between an antigen and an antibody
(see
immune response).
In microbiology,
affinity
describes
physical
similarity
between organisms. In psychology, it
refers to attraction between 2 people.
aflatoxin
A poisonous substance pro-
duced by
Aspergillus flavus
moulds,
which contaminate stored foods, espe-
cially grains,
peanuts,
and cassava.
Aflatoxin is believed to be one of the
factors responsible for the high inci-
dence of liver cancer in tropical Africa.
afterbirth
The common name for the
tissues that are expelled from the uterus
after delivery of a baby. The afterbirth
includes the
placenta
and the mem-
branes that surrounded the fetus.
afterpains
Contractions of the uterus
that continue after childbirth. Afterpains
are normal and are experienced by
many women, especially during breast-
feeding. They usually disappear a few
days following the birth but may require
treatment with
analgesic drugs.
agammaglobulinaemia
A type of
im-
munodeficiency disorder
in which there
is almost complete absence of
B-lympho-
cytes
and
immunoglobulins
in the blood.
agar
An extract of certain seaweeds
with similar properties to gelatine. It
can be taken for constipation to soften
and give bulk to faeces, and to relieve
indigestion and heartburn. Agar is also
used as a gelling agent in media for
bacterial
cultures
.
age
The length of time a person has
existed. Of medical significance in diag-
nosis and in determining treatment, a
person's
age
is
usually
measured
chronologically, but it can also be mea-
sured in terms of physical, mental, or
developmental maturity.
The age of a fetus is measured in terms
of
gestational
age,
which
can
be
assessed accurately by
ultrasound scan-
ning
.
In
children,
the
most
useful
measure of physical development is
bone age (degree of bone maturity as
seen on an
X-ray)
because all healthy
individuals reach the same adult level
of skeletal maturity, and each bone
passes through the same sequence of
growth. Dental age, another measure
of physical maturity, can be assessed by
the number of teeth that have erupted
(see
eruption o f teeth
) or by the amount
of dental calcification (as seen on an
X-ray) compared with standard values.
In adults, physical age is difficult to
assess other than by physical appear-
ance. It can be estimated after death by
the state of certain organs.
Mental age can be assessed by com-
paring scores on
intelligence tests
with
standards for chronological age. A young
child's age can be expressed in terms of
the level of developmental skills, man-
ual dexterity, language, and social skills.
agenesis
The complete absence at birth
of an organ or bodily component, caused
by failure of development in the embryo.
agent
Any substance or force capable of
bringing about a biological, chemical, or
physical change. (See also
reagent
.)
Agent Orange
A herbicide of which
the major constituent is the phenoxy
acid herbicide 2,4,5 T. This substance
may be contaminated in manufacture
with the highly toxic TCDD, commonly
known as dioxin (see
defoliant poisoning
).
age spots
Blemishes that appear on the
skin with increasing age. Most common
are seborrhoeic
keratoses,
which are
brown or yellow, slightly raised spots
that can occur at any site. Also common
in elderly people are freckles, solar kera-
toses
(small
blemishes
caused
by
overexposure to the sun), and
De Mor-
gan's spots,
which are red, pinpoint
blemishes on the trunk. Treatment is
usually unnecessary for any of these,
apart from solar keratoses, which may
eventually progress to skin cancer.
ageusia
The lack or an impairment of
the sense of taste (see
taste
,
loss of
).
aggregation, platelet
The clumping
together of platelets (small, sticky blood
A
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