Exam #1: Cell Biology VI Flashcards
MAPs
Microtubule Associated Proteins
MAP-T (Tau)
- Forms crosslinks between microtubules
- In Alzheimer’s Disease, hyperphosphorylated, leading to aggregation
- Histological “flame” appearance
- Eosinophilic
Neurofibrillary Tangles
- Caused by Tau aggregates
- Will cause cell death, but remain as “ghost cells, or tombstones”
Microfilaments
- Comprised of subunits of actin (have positive & negative end)
- Stained with Phallacidin conjugated with a green fluorescein dye
Where do actin microfilaments grow & disassemble?
- Grow= positive end
- Disassemble= negative end
Where are microfilaments found?
1) Microvilli
2) Cell Cortex
3) Adherens belt
4) Filopodia
5) Lamellipodium
6) Stress Fibers
7) Contractile Ring
What drug inhibits actin polymerization?
Cytochalasins
Thick Filaments
- Myosin subunits
- Darker staining band in striated muscle
- Interact with light staining band (thin filaments)
What pathology does a mutation in myosin give rise to?
Cardiomyopathy
What are the six differe types of Intermediate Filaments?
1) Cytokeratins
2) Desmin
3) GFAP
4) Neurofilament protein
5) Nuclear Lamin
6) Vimentin
Cytokeratin
- Epithelial Tissue
- Glandular organs (liver & pancreas)
Desmin
Muscle (smooth & striated)
GFAP
- Glial Fibrillary Acidic Protein
- Astrocytic Glial Cells
- DO NOT cross link like neurofilaments
Neurofilament Protein
- Neurons
- Cross-linking imparts great tensile strength
Nuclear Lamin
Nucleus of all cells
Vimentin
- Mesodermal Tissue
- Chondroblasts
- Fibroblasts
What can you tell about a tumor by its intermediate filament composition?
Origin
What do you know if a tumor expressed two different types of intermediate filaments?
The tumor is de-differentiating, which is an indication of a more aggressive type of tumor.
Mallory Bodies
- Hallmark of alcoholic liver disease
- Caused by aggregation of cytokeratins in the liver
Epidermoylsis Bullosa Simplex
- Mutations of cytokeratin fiber 14
- Separation of the epidermis where it connects to the dermis
- Causes severe skin blistering & sloughing of skin
Rosenthal’s Fibers
- Aggregates of GFAP
- Seen in astrocytomas
- V. long & thick flame- like projection
Centrosome
- MTOC (Mirotubule-organizing-center)
- Cytoplasmic region near nucleus containing two centrioles oriented perpendicularly
Centriole
Comprised of microtubules in a 9 x 3 arrangement i.e. 9 triplet sets of microtubules
How is nuclear appearance useful in diagnosis?
- Cancer
- Well differentiated tumor cells are less aggressive/ better prognosis
- Poorly differentiated tumor cells are more aggressive/ poorer prognosis
Nucleolus
Site of ribosome synthesis & assembly
Cajal Body
Contain molecular machinery involved in splicing pre-mRNA into mRNA
PML Body
- Promylocytic Leukemia Body
- Function in DNA repair & apoptosis
Nuclear Envelope
- Formed by two lipid bilayers, outer & inner
- Space between is the perinuclear space
- Contains protein complexes that form nuclear pores
Outer Nuclear Membrane
- Typically continuous with the rER
- Ribosomes are often attached
What can readily cross the nuclear pore complex?
Small molecular weight molecules
What are nuclear lamins?
- Type of intermediate filament
- Important in cell division
- Form the nuclear lamina lattice
Nuclear Import
- Protein w/ nuclear localization signal
- Binds nuclear import receptor
- Recognize the nuclear pore complex
- Imported in
- Energy dependent, GTP
What is transported into the nucleus?
- Proteins to assemble ribosomal subunits
What is exported from the nucleus?
- Ribosomal subunits
Progeria
- Premature aging
- Caused by defect in nuclear lamins
What is the role of lamins during mitosis?
- Prophase= phosphorylate lamins for disassembly of the nuclear envelope
- Late Telophase= fuse/ reassemble nuclear envelope nuclear envelope fragments by dephosphorylating lamins
Euchromatin
- Loosely coiled chromatin
- Charge density is less packed
- Basic
- Less intense basophilic staining
- Indication of how active the nucleus is i.e. Euchromatin is very actively transcribing
Heterochromatin
- Tightly coiled chromatin
- Charge density is tightly packed together
- Basic
- Causes very dense basic staining
Chromatin
- DNA wrapped around histone proteins
- “Beads on a string”
Barr Body
- “Drum-stick” that comes off the nucleus
- Indication of female cells
Would you expect to see a nucleolus in a heterchromatic nucleus?
No, it would be very difficult to distinguish between them b/c both are going to stain very strongly
Orphan Annie Eye Nuclei
- Hallmark histological sign of papillary thyroid cancer
- Nuclei appear empty
