Frederik P M
Scan Electron Microsc. 1982(Pt 2):709-21.
Frozen thin sections are considered as the ideal specimen for high resolution studies on the morphological and chemical composition of biological material. However, during the preparation of such sections alterations may be induced. Ice crystal formation during freezing may limit the useful area to a superficial layer of the frozen sample. Heating and/or melting whenever occurring during sectioning will not result in detectable redistribution of material within the sections. Freeze-drying within the cold chamber of the microtome occurs at a slower rate (approx. 5 x 10(-3)) than the maximum rate of drying under vacuum. Rehydration of dry sections in a moist atmosphere or by contact with aqueous solutions will result in typical structural alterations probably caused by redistribution of material. Vapor fixation of the freeze-dried sections will prevent these structural alterations whereas aldehyde fixation in aqueous solutions prior to freezing may not always be sufficient to prevent structural alterations. When fully hydrated thin sections are required low temperature sectioning is necessary to prevent freeze-drying. Embedding and resectioning of such sections cut at -105 degrees C revealed that one of the surfaces was distorted by a saw-teeth form of chatter, the other side was flat. Low temperature sectioning and cryotransfer enabled the study of fully hydrated sections at the resolution of a STEM as well as the observation of the freeze-drying process under vacuum.
冷冻薄切片被认为是对生物材料的形态和化学成分进行高分辨率研究的理想标本。然而，在制备此类切片的过程中可能会引发一些改变。冷冻过程中冰晶的形成可能会将有效区域限制在冷冻样品的表层。切片过程中无论何时发生加热和/或融化，都不会导致切片内物质的可检测再分布。切片机冷室内的冷冻干燥速率（约5×10⁻³）比真空下的最大干燥速率要慢。干燥切片在潮湿气氛中或通过与水溶液接触进行复水会导致典型的结构改变，这可能是由物质再分布引起的。冷冻干燥切片的蒸汽固定将防止这些结构改变，而在冷冻前在水溶液中进行醛固定可能并不总是足以防止结构改变。当需要完全水合的薄切片时，低温切片是防止冷冻干燥所必需的。对在-105℃下切割的此类切片进行包埋和重新切片显示，其中一个表面因锯齿状颤动而变形，另一侧是平的。低温切片和低温转移使得能够在扫描透射电子显微镜（STEM）的分辨率下研究完全水合的切片，以及观察真空下的冷冻干燥过程。
