No abstract

Nuclear transplantation experiments show that differentiated cells, such as lymphocytes, from the adult frog can express the genes necessary for tadpole development. The transplanted cells were proven to be lymphocytes by immunological methods. The origin of the tadpoles that developed after lymphocyte nuclei injections was ascertained by a karyotypic marker.

The cytoskeletons of cells from gastrula and neurula stages of the Mexican salamander (A mbystoma mexicanum) and the African clawed toad (Xenopus laeuis) were analyzed. Bundles of intermediate filaments were found in the superficial layer of the epidermis in neurulae (but not in gastrulae) of both organisms. The bundles (tonofilaments) were observed in the forming notochord of the axolotl but not in the differentiating notochord in Xenopus. Serial semithin sections demonstrated that the notochord develops from invaginated deep cells in Xenopus, but from invaginated superficial layer in the axolotl. Scanning electron microscopy of neurula stages from the axolotl and from Xenopus laeuis confirmed this difference in notochord formation. This dissimilarity in notochord formation seems to be a typical difference between anurans and urodeles as was clearly pointed out by Ruffini ('25). This has implications for the fate maps published by Vogt ('29). The considerable differences in early embryonic development suggest to us that the salamanders (urodeles) and frogs and toads (anurans) are not monophyletic in origin.

A case of alcohol contact urticaria is described. The immediate reactions with most of the primary alcohols were positive. Passive transfer was achieved.

Nickel may be found in prepared foods (tinned foods) at markedly higher concentrations than the safe threshold laid down for hypersensitive patients. Some foodstuffs cooked in stainless-steel utensils attack the metal and thus contain much more nickel than when enamel or aluminum saucepans are used. Among the natural organic acids which may be responsible for dissolving stainless-steel, oxalic acid is the most active at equivalent concentrations.