Allan L. Allenspach

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Selected tissues from chick embryos were fixed in 2% glutaraldehyde and 1% OsO(4), both buffered at pH 7.6 with Veronal-acetate, and were embedded in Maraglas or Araldite. Two types of cell division have been noted. Generally, epithelial cells divide predominantly by a shortening of the chromosome-to-pole distance rather than by spindle elongation;(More)
Chick embryo limb bud cartilage contains a family of proteoglycans, a few of which have been identified ultrastructurally by antibody labelling. Limb bud cartilage from stage 30-34 chick embryos was high-pressure frozen, freeze-substituted and embedded in Lowicryl resin. Sections were treated with polyclonal antibodies for core protein and monoclonal(More)
Early chick embryos (stages 11-29), or parts thereof, were frozen by the high pressure technique and subjected to a variety of freeze substitution protocols. In addition to hexadecene, unincubated albumen was used as a cryoprotectant to surround the specimens during the freezing event. The quality of freeze ranged from poor to very good in these highly(More)
In an earlier publication (Allenspach & Hamilton, 1962) an account was given of chick esophageal development and histogenesis up to 10 days of incubation. The esophagus becomes completely occluded at 5 days (stage 26, Hamburger & Hamilton, 1951) and reopens rapidly at 7-J-8 days (stages 33-34). Detailed observations were made of the histological changes in(More)
We investigated function and ultrastructure of sciatic nerves isolated from wood frogs (Rana sylvatica) endemic to the Northwest Territories, Canada, following freezing at −2.5 °C, −5.0 °C, or −7.5 °C. All frogs frozen at −2.5 °C, and most frogs (71%) frozen at −5.0 °C, recovered within 14 h after thawing began; however, frogs did not survive exposure to(More)
The origin of trypsin in the digestive tract of Lumbricus terrestris was localized by using the chromogenic tryptic substrate carbobenzyloxy-L-arginine-β-napthylamide HCl (CANA) coupled with the azo dye Fast Garnet GBC. The specificity of earthworm trypsin toward the naphthylamide substrate was confirmed by disc gel electrophoresis of homogenates of the(More)