{'fraction_non_alphanumeric': 0.03697936940443752, 'fraction_numerical': 0.021019852082522383, 'mean_word_length': 5.28361858190709, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Freeze-fracture replication of cells of stratum corneum of human epidermis.

The technique of freeze-fracture replication has particular advantages as a method for studying the functional morphology of biological tissues at the ultrastructural level (Steere, 1957; Weinstein & Someda, 1967; Koehler, 1968; Bullivant, 1969; Moor, 1969, 1971; Branton, 1971). Chemical fixation, dehydration, infiltration with embedding media, and staining, all of which may produce artefacts, are not required, so tissues can be examined in a condition closer to the living state than is possible with conventional techniques employing thin sections. Glycerinated tissue, rapidly frozen to -180 'C, is fractured in vacuo, and the exposed surface is then shadowed from an angle and replicated with platinum and carbon. The replica is then separated from the tissue, placed upon a grid, and examined in the electron microscope. With a frozen cell, the plane of fracture traverses the cytoplasmic matrix in an apparently random fashion, and the two resulting fracture faces appear identical. With membranes (plasma, nuclear, and those surrounding organelles), however, the fracture plane frequently deviates and runs parallel with the membrane for variable distances, thus exposing extensive areas en face. Membranes may also be fractured straight across, thus appearing as they would in thin sections. In epithelia such as the epidermis, which are composed of closely apposed cells, it has been established that two fracture faces associated with the plasma membrane appear in replicas (Bullivant, 1969; Chalcroft & Bullivant, 1970; Scott McNutt & Weinstein, 1970; Breathnach, Stolinski & Gross, 1972 a). One of these faces can be identified as being directed towards the interior of the cell; the other as being directed towards the exterior (Fig. 1). The two faces are separated by a step which includes the intercellular space. These two faces, each belonging to one or other of the apposed cells, are complementary, two similar type faces having been fractured away. Each fracture face of epidermal, and other, plasma membranes carries small (5-7 nm) particles 'membrane-associated particles' and in the epidermis the face directed towards the interior of the cell exhibits, in addition, aggregations of small particles which coincide with desmosomes (Breathnach, Stolinski & Gross, 1972a). Gap junctions and tight junctions also exhibit particular features but this study is not concerned with them. It is still uncertain exactly what these fracture faces represent. Some authors (e.g.