Terms used by the scientists and explained as simply as
possible
It has always been a problem that this is one of the most
obscure subjects in microbiology and as such many of the terms
make little sense even to scientists working in virology or
bacteriology. Many of the terms involved are now those used by
chemists and geneticists and they also mean little to the other
groups. The influx of politics and economics into the decision
making has also made things difficult to the laboratory
scientists. Terms will be explained as if the person reading
them has a biological degree and are in alphabetical order.
- ACDP.
- Advisory Committee on Dangerous Pathogens
- ADAS
- Agricultural Development and Advisory Service.
This was a government organisation that provided cheap
veterinary and agricultural advice to farmers. The Thatcher
Government decided that the farmers should pay higher prices and
that it should be privatised if possible. As a result it was
decreased in size dramatically.
- Agent
- The element that is able to transmit a disease. We
are currently unsure what the absolute agent is for a TSE (such
as CJD). Some arguments suggest that it is a virus (see
Diringer) some that it is a virino (see Kimberlin or Narang) and
many that it is a prion (see Bolton or Prusiner).
- Alzheimer's disease
- A specific disease associated with
the breakdown of nervous tissue in the brain, giving rise to a
dementia in the patient. This seems to be one of the most
common conditions of older people in the Western world.
- Amyloid
- A chemical that builds up inside tissue in an
amorphous way.
- Amyloidogenesis
- The production of amyloid
- Amyloidosis
- The build up of amyloid to a degree that it
causes damage to the tissues or action of those tissues in the
body.
- Astrocyte
- One of the brain cells that supports the
nervous tissue.
- Astrocytosis
- The spread of astrocytes into damaged tissue.
- Ataxia
- Loss of coordination by an animal with neurolgical
damage.
- Bioassay
- The inoculation of tissue into another animal in
order to see if it is infective (if it is, the animal will
develop disease). Multiple dilutions of the inoculum will, if
the dilutions are enough, get to the point that not enough
infection is present in the inoculum to cause disease. The
lowest amount of inoculum that will still transmit the disease
is said to contain one infective unit.
- Birefringence
- The appearence under the microscope of
congo red staining of amyloid.
- BSE
- Bovine spongiform encephalopathy
- cDNA
- the DNA of the chromosome i.e. chromosomal DNA.
- Cellular culture
- The culture of individual cells in a
test-tube. Some of these can be infected with a TSE agent and
these cultures can then be used to see if a drug may work
against the agent
- Chronic wasting disease (of deer)
- A
disease found at Fort Worth Zoo only in deer and elk.
- Crystalloids
- The build up of PrP in a crystal form in
such a way as to induce the production of PrPsc from PrPc.
- Clinicopathological correalations
- The association between
the damage that appears to the brain under the microscope and
the damage that appears to have happened to the activity of the
brain.
- CNS
- Central nervous system..
- Congo red
- A specific dye that is used to stain amyloid
but has also been found to inhibit the build up of PrP in
infected tissue in culture.
- Congophilic
- Material in histological sections that
becomes stained by Congo red.
- Creutzfeld-Jakob disease
- A TSE that gives rise to a
pre-senile demntia in human.
- CSF
- Cerebrospinal fluid
- CVL
- Central Veterinary Laboratory
- DNA
- Deoxyribonuclic acid. The chemical that carries the
genome in the chromosome of animals, plants and some viruses.
- Dalton
- A measure of the weight of the molecule.
- DoH
- Department of Health, UK
- Dominant
- The extent to which a gene is expressed;
dominant indicates that it is expressed a lot.
- Downer cows
- Cattle that show neurological problems (an
american term)
- EEG
- Electroencephalogram
- Electrophoresis
- The drawing of a mixture of proteins
through a fine gel by an electric current. This separates the
proteins so that they can be identified.
- Epidemiology
- The changes in the numbers of cases of
disease in relation to time and space.
- Episome
- A part of a gene.
- EU
- European Union.
- Famillial fatal insomnia
- A clinical disease found in
humans that has been found to be a TSE and is due to a specific
change found in the prion protein.
- FSE
- Feline spongiform encephalopathy
- Genome
- The total make-up of the genes for an infective
agent (or any other life).
- Genotype
- The types of the genes of an organism.
- Gertmann-Straussler-Scheinker
- A familial TSE found in
humans and associated with a specific change in the PrP gene.
- Glycoform
- A type of protein with a specific type of
glycoprotein attatched. i.e. two proteins would be of the same
glycoform if they carried the same glycoprotein. This was
important in that Dealler's hypothesis that the strain of prion
disease depended on the glycan chain was shown to some degree by
Collinge et al in 1996 and that this inferred that treatment was
possible.
- Glycoprotein
- A protein that carries attatched to it some
chains of sugars (glycans). PrP carries two of these chains and
it has been suggested that it is different chains that actually
separate the strains of TSEs.
- Glycosylated
- With a carbohydrate added.
- Iatrogenic cases
- These are the cases of CJD that appear
as a result of medical activity inoculating the disease into the
patient. e.g. growth hormone inoculations.
- HPLC
- a method of separating molecules using liquid
chromatography
- Immunoblotting
- The removal of specific proteins onto a
filter paper, and then testing the paper for the protein. This
is a way of purifying and being sure of what is found.
- Immunohistochemistry
- The testing of sections of tissue
for specific proteins by attatching them with specific
antibodies, and then looking for the antibodies through the
enzymes to which they were connected.
- Immunolabelling
- The testing of sections of tissue (or
electron microscopy samples) by attatching antibodies to
specific proteins in the tissue. The antibodies may have
further labels attatched to them and it is these that act as the
labels.
- Immunostaining
- As in immunohistochemistry but using a dye
as the indicator.
- Infective range
- The range of animals that a disease can
infect.
- Infective Unit
- This is the minimum amount needed to
transmit a TSE from one animal to another of the SAME species.
- Inversely related
- One item affects another so that when
one increases the other drops.
- Kuru
- A disease found in the Fore tribe in New Guinea, and
due to the eating of human infected tissue by members of a
tribe. In general the women ate brain tissue rather than the
men and so it was the women and children that died relatively
rapidly of the disease.
- Lateral (or horizontal) transmission
- transmission of a
disease from one animal to another except from the parent to the
offspring. Generally this is the transmission between two
animals alive at the same time and for one to be exposed to the
agent from the other.
- MAFF
- Ministry of agriculture fisheries and food in the UK.
- Maternal transmission
- The transmission of disease from
the mother to the offspring (not necessarily before birth).
- MBM
- Meat and bone meal.
- Microglia
- immune cells from inside the CNS
- Murine models
- models of disease, using mice as the animal
being infected.
- Neuroanatomy
- The anatomy of the brain, spinal cord and
peripheral nervous system.
- Neurogenenic culture
- The growth of nervous tissue in the
test tube for the growth of the TSE agent in the tissue.
- Neurogenesis
- The production of new nervous tissue.
- Open reading frame
- or ORF. The is the part of the gene
that is used to start the production of some RNA from a gene
made of DNA.
- OTM
- Over thirty months. See TMR.
- PAGE
- polyacrylamide gel electrophoresis to separate
molecules.
- Parenteral
- Inoculation into the body (not by mouth)
- Passage
- The inoculation of an infection into an animal
and then harvesting the infective agent from the animal.
- Pathogenesis
- The production of damage (pathology) in a
tissue.
- PCR
- Polymerase chain reaction. A method use to make
multiple copies of DNA.
- Peripheral
- This generally refers to the ingestion or
inoculation of material into an animal outside the central
nervous system.
- Phenotype
- The effect made on the organism by the genes
that it carries. Some genes (see genotype) may have no effect.
- Plaques
- The proteinaceous elements that may build up in
brain tissue as a result of infection. They may, however, be
found in other diseases apart from a TSE.
- Polymerisation
- This is the way that prions may be thought
to build up. i.e. by one PrPc joining onto the end of a PrPsc
crystal.
- Precursor
- The chemical element that changes due to
enzymatic or physical pressure.
- Prion
- This is the protein that makes up the infectious
agent claimed by a large number of groups now to be the
infectious particle that transmits the disease from one cell to
another and from one animal to another. It is made from the
normal protein PrPc (the c stands for chromosomal) that is
produced in small quantities on many cells and especially the
lymphoid and nervous tissue cells.
- Prion rods
- The microscopic rods that appear when prions,
that have been broken up with proteinase K but then allowed to
come back together into crystalline forms.
- Promoter
- A chemical agent that causes the expression of a
gene or the change in the way that it acts.
- Protease K
- This is the enzyme that breaks down proteins
very powerfully...but the protein that is found in an infected
cell is, for some reason not broken down by the enzyme.
- PrP
- The prion protein. It can exist in various forms.
One is called PrPc and is the normal type of the protein that is
found in a cell (i.e. chromosomal PrP). One is called PrPsc (or
PrPscrapie) that is found in the infected cells. It may be
called PrP-res, indicating that it is difficult to break down
with proteinases. PrP27-30 is the name of the prion protein
after it has been broken up
by protease K.
- RNA
- Ribonucleic acid. Often found in viruses as the
nucleic acid that caries the genome of the agent.
- SAF
- Scrapie associated fibrils. These are the fine
structures, seen under the electron microscope that are only
found in brains of TSEs. It has been suggested that they are
the infective agents themselves, as infectivity can be filtered
out with a filter small enough to stop the SAF.
- SBO
- Specified bovine offals. These were the offals of
any cow that were thought to represent a risk to the population.
Introduced in 1989. Thymus, brain, spinal cord, gut (below
duodenum), spleen, tonsils.
- SBM
- Specified bovine materials. These were the parts of
a slaughtered cow that were not considered acceptable for human
consumption as of around December 1995. The name was changed
from SBO because some of the new materials were not offals.
- Scrapie
- The TSE of sheep or goats.
- SDS
- The compound used in solvents and to attatch to
proteins (and hence allow them to be electrophoretically
separated).
- SEs
- Spongiform encephalopathy.
- SEAC
- Spongiform encephalopathy advisory committee.
Tyrrell committee.
- SERC
- Spongiform encephalopathy research campaign.
- Species barrier
- There appears to be needed much greater a
quantity of infectivity to pass a TSE from one species to
another rather to a species that is the same as the one from
which the sample has come.
- Sporadic cases
- The cases of CJD (or perhaps other TSEs)
that are apparently not associated with a change in the gene of
the person developing the disease and not associated with the
inoculation of infective material.
- Strains
- It appears that some forms of a TSE in a specific
animal may have different characteristics from other forms.
These are known as separate strains.
- Sulphated-glycan inhibition
- The chemicals that have been
found to prevent infectivity of inoculated agent.
- TMR
- Thirty Month Rule. The rule introduced in April
1996 by the demand of the farmers in the UK (stated as
unnecessary by MAFF) that catte over 30 months of age should not
be used for human food.
- Transgenic mice.
- These are mice carrying a specific
gene from another animal. There may be more than one copy of
the gene (for instance, in many transgenic mice containing the
human PrP gene there may be over 20 copies) and may actually
replace the gene that is there normally. The gene is unlikely
to be at the same site as the normal gene in the animal
chromosome. To insert the gene requires the DNA to be inserted
into the fertilised ovum of the animal and hence is very
difficult indeed, with many failures.
- Transmissible mink encephalopathy
- or TME. This is the
TSE of mink and has been known for around 30 years, particularly
in the mink farms of the USA.
- Transmissible spongiform encephalopathy
- A disease that
can be transmitted from one animal to another and will produce
changes in the brain that are appear similarly to a sponge (i.e.
some of the cells are clear when seen down the microscope)
- Tubulofilamentous particles
- The particles seen under the
electron microscope that may be associated with infectivity.
- Ultrastructure
- The physical and chemical structure of the
amyloid or PrP. Often this includes the way in which the
proteins are shaped.
- Vertical transmission
- The transmission of an illness from
the parent(s) to the offspring.
- Virino
- A small item that may be the infective agent of a
TSE. It contains protein and nucleic acid.
- Viroids
- Small virus-like particles. A term used often in
TSE to get around the fact that the infective agent is not yet
known.
- Virus
- A infective agent with a specific structure and
able to cause its own multiplication after infection of specific
cell