chapter 1 (methods) Flashcards
fixation
process by which specimen is treated by exposing it to a fixative in order to preserve tissue permanetently
-the fixative should be 15-20 times more in volume than the specimen (samples must be frozen they can not be left out) (fixative fixes it/freezes it)
-fixative is choosen based on the type of molecule you want to preserve
purpose of fixation
prevent autolysis and bacterial attack, allow clear staining of sections, leave them as close to their living state as possible, happens because of the reaction between the fixative and the protein which forms a gel (keeps in in vivo)
histotechnology
science is centering on the microscopic detection of tissue abnormalities for disease diagnosis, treatment, etc…(can also prep surgical specimen for screening by pathologist.)
sample size
thinner better because then the light can pass through it easier, but not too thin
histology
microscopic anatomy; study biological tissue includes histopathy (microscopic study of diseased tissue)
resolving power
limit of resolution of a microscope is the smallest distance between 2 points that can be seen using a scope
hematoxolin and eosin
most common stains
transmission electron microscopy
high magnification of cross section (tungsten filament, condenser lens, specimen, objective lens, projector lens, imaage on screen)
-black and white
-sends x ray through the tissue
scanning electron microscopy
lower magnification of surfaces
-black and white
-only scans the surface of the tissue
confocal fluorescence
clearer image of single cell
-in color (better)
conventional fluorescence
blurry image of cell
-in color
cell culture concerns
contamination is a major concern
cultures
-can be plant or animal
-grow hela cells or plants or clone mice hearts etc.
microtomes
used to cut samples in prep for slides
cryostat
used to freeze the tissue, section tissue without going through all the other steps that could damage the sample BUT your CAN NOT save the sample it is NOT viable for life like fixation
-used in hospitals for quick diagnosis, takes less time
-takes no time to put it through the paraffin
histochemisty
the study of chemical grouping within the cell and tissues
Feulgen Stain
feulgen nuclear reaction for the specific staining of DNA in cytohistochemical samples
-it is a chemical treatment, HCL hydrolysis to produce free aldehyde groups in the DNA backbone structure that could be detected by a colored reaction for aldehydes
-stain for DNA used to be the only way to look for DNA, new methods use antibodies
MAB
antibody drug/ biologic
-NOT A CHEMICAL DRUG
indirect immunohistochemistry
uses primary antibody, labelled secondary antibody to target proteins
immunoflourescence
-develop antibody against antigen
-hit it w a lazer get a color reaction
-labeled primary antibody onto protein with a flourescant tag and signal
-antibodies make the color
antibodies
can be made against anything, DNA, Proteins, etc and the antibody will NOT bind to anything else
colormetric
preferred by pathologist
-takes less time and easier to work with than flourescence
-lasts forever and you can go back tot he sample whenever
-flourescence will not last forever (the signals die)
autoradiography
an image on an x-ray film or nuclear emulsiom produced by the pattern of decay emissions (beta particles or gamma rays) from a distrubutor of radioactive substance
-not used as much as radioactive isotopes or antibodies w flourescent tags
-requires microscope film (makes it harder)
In Situ hybridization
uses single strand DNA instead of antibody
-DNA or RNA has a tag that joins DNA in target site
xray crystallography
x ray beam hits crystalized DNA molecules and its reflected onto the film (the pattern that Watson and crick saw)
eye tissue
the most difficult tissue to cross section bc it is fragile and has different types of tissues within it
-need a different fixative per tissue (lens, cornea etc.)
-davidson is the best fixative
photomicroscopy
camera attachment to microscope
many different types of DNA
-b DNA (regular)
-Z DNA
-Queadraplex etc…
