Vertebrates - Tissues
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Frozen hydrated rat renal kidney cortex (unetched)
The cortex of the kidney is composed of many proximal and distal convoluted tubules. These are obvious here in longitudinal, transverse and oblique fracture (compare with slightly etched preparation).
Bar: 10um
Frozen hydrated rat renal kidney cortex (slightly etched)
If the specimen is warmed to a temperature at which sublimation of water occurs, subsurface information about the specimen may be obtained. In this case the surface was warmed to -80°C for four minutes.
Comparison with the unetched image demonstrates the value of etching, improving the amount and quality of information from the specimen surface.
Bar: 10um
Fractures through the myocardium
Small pieces of heart have been mixed, washed in buffer then cryo-protected with 30% glycerol. Contracted myofibrils can be seen in longitudinal aspect. The fracture in places has occurred along the sarcolemma and the positions of the Z-lines (marked by ‘z’) and the T-tubules (marked by arrows) are clearly visible in places.
The intimate relationship between the capillaries and the myofibrils can be appreciated from this preparation. The contents of the capillary have a smooth appearance due to the presence of glycerol.
Bar: 5um
Critical point dried mouse lung
NB: compare with frozen hydrated mouse lung (below).
The lung consists of a mass of spongy alveoli where gaseous exchange occurs between blood and air. These are connected to the trachea via small airways called bronchioles.
The micrograph illustrates a mass of alveoli (marked by ‘a’) associated with alveolar ducts into which the bronchioles open (marked by ‘b’). A mass of capillaries are associated with the alveoli. The walls of the alveoli (septa) are composed of epithelial cells, connective tissue and elastin. The walls are generally one cell thick and highly hydrated.
Consequently, conventional preparation methods such as dehydration followed by critical point drying cause collapse and shrinkage of this very delicate tissue.
Bar: -5um (inset: 10um)
Frozen hydrated mouse lung
Low-temperature SEM retains all of the cellular and extra-cellular fluids in the lung tissue. Consequently, the micrograph clearly illustrates that the bronchioles are covered with a thin layer of mucus (marked by arrows). None of the alveoli show any collapse.
Bar: 5um