Study Guide Terms Exam 1- Microscopy Flashcards
What is Cyvenio and how does it work?
- liquid biopsy device for the immunomagnetic and microfluidic capture of CTCs
- Uses antibodies that bind to proteins on CTCs surface. The antibodies are attached to magnetic particles, so once the antibodies bind to the CTCs the particles are separatd from the rest of the blood using a magnetic field
- Is more specific than vortex but may miss CTCs that do not have the marker
What research question does Cyvenio address?
- cancer progression and metastasis
- treatment efficacy
- cancer detection and monitoring
amount of CTCs correlated to cancer progression/if cancer has spread
What is Vortex and how does it work?
- device for microfluidic extraction of CTCs from liquid biopsies
- relies on physical characteristics of CTCs to capture them in a microfluidic vortex
- WBCs and RBCs move down the river faster leaving CTCs behind. They are collected and counted- no antibodies used to count
What research question does Vortex address?
- CTC collection (same as Cyvenio)
- But does not use antibodies and can capture a broader range of CTCs
What is CellInsight CX5 instrument and how does it work?
- automated imaging system designed for high-throughput analysis of cells using fluorescent and brightfield microscopy to capture high-resolution images of cells in multi-well plates
- can scan 1000s of samples automatically
- extracts quantatative data on cell morphology, intracellular markers, protein expression, and other metrics
What research questions does CellInsight Cx5 attempt to address?
- drug discovery: researchers can study how potential drug candidates affect cellular phenotypes such as cell cycle progression/mitosis
- Toxicology studies: can assess how chemicals or drugs impact cell viability/structure/function
- Cell morhphology and phenotype changes
Class example: used to see if GVA halts cells in mitosis
What is brightfield/compound light microscopy and how does it work?
- oldest and most often used microscope, used to look at dead cells and tissue sections (often used by pathologists and cytochemists)
- resolving power of .2 microns
- Process:
- fixation using chemicals like formaldehyde (cross-links proteins)
- dehydration, replace H2O w ethanol
- xylene replacement
- infiltration w paraffin- results in wax block w tissue held in statis
- microtome to cut 10-15 micron sections
- place sliced sample onto slide
- remove wax and return sliced sample to being filled with water
What research questions does bright field microscopy attempt to address?
- Often used in pathology and cytochemistry- used for dead tissue sections/cells
- Best for specimens that naturally contrast with their background or can be easily stained (hematoxylin for nucleus, teosin for cytoplasm)
- Lasks intracellular detail
What is a cryostat and how does it work?
- easier to get tissue samples cut than paraffin
- sections are quickly frozen
What research questions does a cryostat attempt to address?
- often used in operating rooms for quick analysis- not typically used for pathology reports
- Ex. Mohs surgery- skin removed in consecutive rings until margin is found and rings are quicklly analyzed
What is a phase microscope and how does it work?
- light microscope, contrast created from light interference- adds wavelengths in sync to enhance or out of sync to diminish
- used by cell culture biologists, designed to look at living cells without fication or dyes
What research questions does phase microscopy attempt to address/solve?
- used in living cells w/o fixation or dyes (non-invasive, preserves natural cellular behavior)
- allows researchers to observe finer details of live cells that would otherwise be difficult to see in brightfield microscopy (enhanced contrast, idealfor trasnparent spcimens that lack contrast under brightfield microscopy)
- Real-time dynamics
What is Differential Interference Contrast/Nomarski microscopy and how does it work?
- light microscope that enhances contrast of transparent unstained specimens
- converts phase shifts into variations in light intensity
- provides 3-D image
What research questions does DIC/Nomarski optics attempt to address/solve?
- Provides pseudo-3D images that highlight surface details and edges
- Applications include single cell electrophysiology (slender pipette and poke cell to look at change in membrane potential) and patch clamping (monitors ion flow through single cell membrane channels)
What is patch clamping and how does it work?
- Glass micropipette with a very fine tip used to form a tight seal with the cell membrane, suction is applied
- membrane can be pulled to study of intracellular side of ion channels (inside-out) or extracellular side (outside-out)
- amplifier connected to pipette controls voltage accross the membrane or can measure the current that flows through ion channels
What research questions does patch clamping attempt to address/solve?
- ion channel function
- action potential generation/signal propagation
- NT and drug effects on ion channel activity
- synaptic transmission
What is darkfield microscopy and how does it work?
- illuminates specimen with scattered light from the specimen
- creates bright images of the sample against a dark field
- useful for small/thin structures that would otherwise be difficult to see using brightfield microscopy
What research questions does darkfield microscopy attempt to address/solve?
- often used by microbiologists because it can detect very small particles/microorganisms that scatter light
- can see bacteria very clearly, much better than bright field/phase
What is point scanning confocal microscopy and how does it work?
- confocal microscope (type of microscopy governed by Abbe’s equation with much better theoretical limit of resolution than light microscopes
- Uses confocal pinholes to narrow a monochromatic laser beam and point-by-point scans, then uses a computer to display summed images
significantly improved visualization of cells bc removed out of focus light
What research questions does Point Scanning Confocal microscopy attempt to address/solve?
- More precise imaging
- Can do optical sectioning: can Z stack data and generate 3-D image
- Can use multiple labeling for structure differentiation- can see a lot more in living cells than before (including 3D cellular architecture)
- Especially useful for thick/complex specimens
but fluorochromes photobleach when radiated by laser
ex. allowed for invention of VivaScope for skin issues (handheld)
What is spinning disk confocal microscopy and how does it work?
- differs from point scanning by using large number of pinholes arranged in spiral pttern and spun rapidly
- works much faster
What research questions does spinning disk confocal microscopy attempt to address/solve?
- High speed imaging-fast dynamic processes in live cells (such as endoplasmic reticulum changes)
- reduced phototoxicity due to collecting light more efficiently
- larger scale 3d imaging
What is polarizing light microscopy and how does it work?
- Uses interaction of polarized light with structures that have optical anisotrpy (different optical properties in different directions)
What research questions does polarizing light microscopy attempt to address/solve?
- looking at highly ordered structures organization/orientation
- often used by neurobiologists (microtubles) and muscle cell biologists (actin/myosin)
What is fluorescence microscopy and how does it work?
- Use of flurochromes to measure changes in cell behavior
- Dyes are chemically modified with a special group that allows permeability through cell membrane and detaches once inside the cell
- A light source emits light that is absorbed by the flchrome, exciting the electrons… the flchrome emits light as the electrons return to their ground state. Emitted light is longer wavelength (lower energy) than the excitation light
What research questions does fluorescent microscopy address/solve?
- protein localization
- cell structures
- gene expression
What is FRAP and how does it work?
- Fluorescence recovery after photobleaching
- Steps: molecules of interest labeled w fluorochrome. Specific region of sample photobleached to damage flurophores attached to the molecules in that region. OVer time, unbleached molecules from the surrounding areas diffuse into the bleached region.
- The recovery is tracked by images taken at regular intervals
What research questions does FRAP address/solve?
- lateral fluidity of cell membrane proteins
- diffusion rates of molecules within membranes or cytoplasm
- how fluid/dynamic a cell membrane is
- how proteins move within/netween organelles
What are vital fluorescent dyes and how do they work?
- dyes used to stain live cells/tissues without killing them- do not require fixation so maintain the functional and physiological integrity of the cells
- are fluorescent, diffuse easily, and are membrane insoluble once inside the cell
- JC1:mitochondria (green=monomers=low PMF aka dysfunctional mitochondria, red=J-aggregates=high PMF aka healthy mitochondria)
- Calcein (not membrane soluble, green)-AM/Propidium-Iodide (red): live-dead assay
- Flu3-AM (green): measures intracellular calcium concentrations in living cells
What research questions do vital fluorescent dyes address/solve?
- cell viability (calcein and propidium iodide)
- Membrane integrity
- Mitochondria function (JC-1, based on PMF)
- dynamics of calcium signaling in live cells (Flu-3)
What is TIRF and how does it work?
- microcope that enables visualization of molecules near a surface with high spatial resolution
- works by selectively exciting fluorophores within a thin region of the sample using total internal reflection
- developed to see the edges of cells that you can’t always see in the plate
What research questions does TIRF attempt to address/solve?
- receptor and signaling molecules behavior at cell membrane (dynamic events at cellular interfaces)
What is fluorescence immunocytochemistry and how does it work?
- use of antibodies to idenfity proteins in cells
- Direct method: primary antibody enters cell w attached flurochrome, binds to POI and fluoresces
- Indirect method: after primary antibody enters, secondary antibody enters and binds to primary antibody, and fluoresces. Much more specificity and affinity (and signal amplification bc multiple secondary antibodies can bind to each primary)
What research questions/techniques does fluorescence ICC attempt to address/solve?
- protein localization: where a protein is within a cell
- cellular pathways/processes: how does a protein change location during cell signaling/cell cycle
What is ELISA and how does it work?
- enzyme linked immunobsorbent assay- measures low concentrations of biomolecules w precision
- plate coated w antigen or antibody that binds to target of interest. sampe is added and binds to coating in well. detection antibody that recognizes and binds to target molecule added- often linked to an enzyme to catalyze colorimetric reaction. substrate for enzyme added, causing color change proportional to the amount of target molecule bound in the well
- spectrophotometer used find absorbance to quantify the concentration
can be colorimetric or fluorescent