Abstract:
1)
The Ultrastructural appearance of frozen-fractured mouse
liver cell membranes, and consistent variations in the
distribution of membrane-associated particles caused by
various pretreatments as described by previous investigators,
were confirmed in this study.
2)
Freeze fracturing, was evaluated as a method for studying the
ultrastructure of single celled microorganisms. Large
prokaryotes with previously undescribed morphologies were
investigated using freeze fracturing, thin sectioning, and
negative staining techniques.
3)
Structures thought to represent flagellar attachment sites were
demonstrated in frozen fractured bacterial preparations for the
first time.
4)
A previously undescribed level of cell organization was discovered
in a rumen organism classified morphologically as Selenomonas.
5)
A technique was devised to retrieve replicas from both sides
of the fracture of a single frozen-fractured specimen. The
results obtained by its use support the theory that frozen cell
membranes fracture along some interior plane rather than at
the membrane-cytoplasm boundary. The technique also showed
that the particles seen on frozen fractured membranes lie within
the thickness of the membrane.
6)
For determination of the third dimension in freeze fracture
replicas, i.e. the heights of various features, an alternative
method to stereoscopy was devised.
This method, which
can be made semiautomatic in execution, involves microdensitometry of electron micrograph negatives and certain
mathematical manipulation of the optical density data.