Previous studies by Stephens and McNulty and Strecker and Stephens have demonstrated that foil barriers placed between the mesonephros and lateral plate at stages 12 to 15 inhibited limb development, but foil barriers placed between the neural tube and somites at stages 11 to 12 resulted in limbs with normal skeletal patterns. It was concluded that some influence present in the paraxial region of the embryo at stages 11 to 15 is necessary for normal limb development. The present study was undertaken to localize that influence more precisely. Foil barriers were placed in the lateral edge of the somites or segmental plate of stage 10 to 15 chick embryos. Barriers placed into stage 13 to 15 embryos resulted in chicks with normal limbs, but barriers placed into stage 10 to 11 embryos resulted in chicks with defective limbs. Barriers inserted just lateral to Hensen's node at stages 6 to 8 resulted in embryos with defective or absent wings. We also grafted stage 4 to 9 presumptive limb territories with and without Hensen's node. Explants without Hensen's node formed limb-like structures in 1% of the cases. Explants with Hensen's node formed limb-like structures in 27% of the cases. When barriers were implanted and a node was placed on the lateral side of the barrier, limbs formed in 40% of the cases. These data suggest a medial to lateral progression of some as yet unknown morphogenetic influence necessary for normal limb development and we hypothesized that the influence may initially emanate from Hensen's node.
A differential diagnosis between fetus amorphus and placental teratoma based on the presence of an umbilical cord and/or skeletal organization in the fetus amorphus has been proposed (Fox and Butler-Manual: Journal of Pathology 88:137-140, 1964). We report a description of one new case of fetus amorphus, along with the results of a critical reexamination of 96 cases from the literature. Our findings fail to support the proposed criteria for distinguishing fetus amorphus from placental teratomas. We find that the presence or absence of an umbilical cord does not relate at all to the developmental state of the specimen. The extent of skeletal development may be a more valid criterion; however, the internal organization in the fetus amorphus forms an anatomical continuum with that of the placental teratoma, making a differential diagnosis meaningless. Additional research is necessary to solve this dilemma.
Fifteen identified species and 13 genera, of endoparasitic helminths (Digenea, Eucestoda, Nematoda, Acanthocephala) were collected from 207 white crappie and 189 channel catfish June, 1967, through September 1968, from a 3,300-acre, turbid reservoir in northc#{232}ntral Oklahoma. Differences in the prevalence and intensity of helminths from six reservoir collection sites were not statistically significant. Statistically significant differences in intensity and prevalence of certain helminth were found among different age classes of the hosts. Ontogenetic changes in the food habits of channel catfish, from a diet of invertebrates to fish, were apparently the reason for changes in the occurrence of many enteric helminths. The occurrence of some helminths, however, was independent of age. Changes relating to age in the crappie were limited to the occurrence of Posthiodiplostomum mninimumn
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