CYTOLOGY DEMONSTRATIONS PART 1
Dr. Crissman
These micrographs are also posted on the bulletin boards by the Bookstore.
They will be available until after the exam.
Boundary between two glial cells, 350,000X
What keeps the two plasma membranes from contacting each other, and as far apart as
they are? Are all membranes symmetrical? Why or Why not? Fawcett, The Cell 1981
FREEZE-FRACTURE EM OF TWO CELL MEMBRANES
An unspecified area of two membranes of adjacent cells. The arrows point to where the
cell membranes of the adjacent cells are fractured. The upper half (E face) is the internal
surface of the outer (exterior) layer of the membrane. The fracture plane then breaks
across the intercellular space and cleaves the membrane of the adjacent lower cell. In this
cell, you are looking at the internal surface of the cytoplasmic layer of lipid (P-face). The
surface is clearly studded with protein particles. The E-face is relatively devoid of
particles. Fawcett, The Cell 1981
MITOCHONDRIA 800X
This is a view of the vertebrate kidney stained with iron alum (Regaud’s method). The
mitochondria stain black. Note that the luminal surface of the cells is almost clear and
that the mitochondria are clearly concentrated in the basal aspect of these cells in the
kidney tubules. The tubular lumens are almost clear in this view. What is the function(s)
of these mitochondria?
CROSS SECTION OF KIDNEY PROXIMAL TUBULE
This represents one of the kidney tubules seen in the previous light micrograph stained
for mitochondria. The tubule is lined by simple cuboidal epithelium with four visible
nuclei and clearly defined microvilli on the luminal surface. The mitochondria are more
evenly distributed in the cytoplasm due to better fixation but they still are more
concentrated in the basal aspect of the cell. Note the RBC’s in the capillaries outside the
tubule in the scant connective tissue. - Budd
MITOCHONDRIA FROM PANCREAS 125,000X
The dark structures within the matrix are mitochondrial polysomes. Mitochondria have
their own components of circular DNA, ribosomes and tRNA so that protein synthesis
can occur in the matrix. Keep in mind that only a small fraction of the genetic
information required to synthesize all the proteins is contained in the circular
mitochondrial DNA. The vast majority of mitochondrial proteins are synthesized in the
cytoplasm on free polysomes using mRNA coded in the nucleus. Replicating – Yes
Independent – NO!!!
Fawcett, The Cell 1981
MITOCHONDRION IN SPERM FLAGELLA 130,000X
What are the organelles along both sides of the sperm tail? How many are there? What is
the functional significance of the proximity of this mitochondrion to the flagellar
microtubular proteins?
Fawcett, The Cell 1981
MITOCHONDRIA FROM THE SUPRADRENAL CORTEX 63,000X
Note the tubular structure of the cristae in these mitochondria. Many of the cristae do not
end blindly, but traverse the entire width of the organelle and are continuous with the
inner membrane on the opposite side.
Note that the mitochondria of different tissues have different functions and
correspondingly, different structures.
Fawcett, The Cell 1981
MITOCHONRIA OF BROWN FAT 70,000X
These are very large mitochondria (5-7 μm) when compared to the size of the nucleus at
the bottom of figure. In spite of their large size, many of the cristae extend across the
entire width of the mitochondrion. One function of brown fat mitochondria is to produce
heat during hibernation. The uncoupler protein, thermogenin, is located in the inner
mitochondrial membrane.
Fawcett, The Cell 1981
MITOCHONDRIA IN LIVER 70,000X
Mitochondria from a hamster liver. At this magnification, one can clearly see the inner
and outer mitochondrial membranes and the resultant intermembrane space. The pale
grey-staining material is the mitochondrial matrix. In the liver, the cristae (arrows) are
not well developed.
Fawcett, The Cell 1981
MITOCHONDRIAL DNA
Mitochondrion from the plant Vica fabia. DNA has been demonstrated in the
mitochondria of many plants and animals. It is found in the form of filaments of varying
thickness located in the matrix in regions of lower density.
DNA is circular, not linear, and is similar in structure to the DNA found in prokaryotic
cells (bacteria). One theory holds that mitochondria are phagocytosed bacteria that
survived ingestion and developed a parasitic relationship with the host cells. Many of the
mitochondrial proteins are coded in the nuclear DNA of the host cell. How this developed
is unknown. Fawcett, The Cell 1981