Untitled - D Ank Unlimited

directional flow 231 disulfide bonds
directional flow
Inhaled microorganisms in dust or droplets greater than 5
μm adhere to the mucosa lining the upper respiratory tract
and are swept upward by cilia to the posterior pharynx followed
by expectoration or swallowing.
directional selection
A form of natural selection in which older alleles are replaced
with newer variants, as in the MHC, leading to change.
discoid lupus erythematosus
A type of lupus erythematosus that involves only the skin,
which manifests a characteristic rash. The viscera are not
involved. The skin manifests erythematous plaques and
telangiectasis with plugging of the follicles. Also called
cutaneous lupus erythematosus.
Discoid lupus erythematosus.
Discoid lupus erythematosus. Immune deposits at dermal–epidermal
junction.
discontinuous epitope
Refer to conformational epitope.
disintegrin
Low molecular weight peptide found in several different
snake venoms. Disintegrins interrupt integrin
function by blocking their interactions with surface
receptors. Thus, they function as integrin inhibitory
proteins.
disodium cromoglycate
A valuable drug for treating immediate (type I) hypersensitivity
reactions, especially allergic asthma. Although
commonly used as an inhalant, it may also be administered
orally or applied topically to the nose and eyes.
Mechanisms of action that have been postulated include
mast cell membrane stabilization and bridging of immunoglobulin
E (IgE) on mast cell surfaces, thereby blocking
bridging by antigen.
disseminated intravascular coagulation (DIC)
A tendency to favor coagulation over fibrinolysis in the
blood circulation as a consequence of various factors.
In DIC, 30 to 65% of the cases are due to infection. Fast
or slow DIC may occur. The fast variety is characterized
by acute, fulminant, consumptive coagulopathy
with bleeding as a result of Gram-negative substances,
massive tissue injury, burns, etc. Deficient or consumed
coagulation factors must be replaced in fast DIC.
Slow DIC accompanies chronic diseases characterized
by thrombosis, microcirculatory ischemia, and endorgan
function. Examples include acute promyelocytic
leukemia, neoplasia, and vasculitis. The pathogenesis
includes endothelial cell damage produced by endotoxins
or other agents, activation of platelets, and activation of
the intrinsic coagulation pathway. Tissue thromboplastin
may be released by trauma or neoplasia, leading to
activation of the extrinsic pathway. Patients with DIC
have elevated partial thromboplastin time, prothrombin
time, fibrinopeptide A, and fibrinogen degradation products
along with decreased fibrinogen, factor V, platelets,
antithrombin III, factor VIII, and plasminogen. Diffuse
cortical necrosis of the kidneys occurs.
dissociation constant
The equilibrium constant for dissociation. This is usually
described in enzyme–substrate interactions. If the interaction
of enzyme with substrate attains equilibrium prior
to catalysis, the Michaelis constant (K M) represents the
dissociation constant. The Michaelis constant is equivalent
to the concentration substrate when the reaction velocity is
half maximal.
distemper vaccine
An attenuated canine distemper virus vaccine prepared
from virus grown in tissue culture or chick embryos.
distribution ratio
The ratio of plasma immunoglobulin to whole-body
immunoglobulin.
disulfide bonds
The S–S chemical bonds between amino acids that link
polypeptide chains together. Chemical reduction may break
these bonds. Disulfide bonds in immunoglobulin molecules
are either intrachain or interchain (i.e., linking heavy to
light chains and heavy to heavy chains). The different types
of bonds in immunoglobulin molecules differ in their ease
of chemical reduction.
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