Microlesions on rumen papillae of sheep fed diets of wheat grain.

Scanning electron microscope evidence of microlesions on the rumen papillae of lambs fed a wheat grain diet is presented. These represent an early and previously unrecognised stage of rumenitis.

A simple technique for examining frozen hydrated specimens in the scanning electron microscope.

The use of a wide angle backscattered electron detector in a scanning electron microscope, which has the capability of the specimen chamber pressure being controlled independently of the column pressure, provides a simple technique for examining frozen hydrated specimens. Large specimens have been examined within 1 min of being placed on the stub and have been examined for many hours without charging artefacts or distortion due to dehydration.

A wet stage modification to a scanning electron microscope.

A modification to the vacuum system of a JSM2 scanning electron microscope has enabled hydrated specimens to be placed inside the specimen chamber of the instrument and to be surronded by water vapour at a pressure up to approximately I 3-kPa (10 Torr). The surface topography was observed by detecting the backscattered electrons using a wide angle backscattered electron detector placed close to the specimen. The microscope was operated in the normal scanning mode which allowed the examination of the surface topography of the specimens, whilst still retaining the depth of focus which is a feature of the SEM. This modification has enabled a resolution of approximately 0.2 mum to be obtained from biological specimens partially immersed in water at temperatures just above 0 degrees C.