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P Alberch

Publications and source records attributed to P Alberch.

7 recordsLinked to original sources
PubMed1986

Plasma T4 and T3 levels in naturally metamorphosing Eurycea bislineata (Amphibia; Plethodontidae).

We measured the circulating T4 and T3 levels in the plethodontid salamander Eurycea bislineata at various stages of metamorphosis using radioimmunoassay (RIA). Seven distinct metamorphic stages were defined based on specific developmental events concerning the remodeling and differentiation of skeletal elements. Special effort was made to study individual variation in the levels of plasma thyroid hormones. For this reason we did not pool serum from several specimens. The RIA was conducted in aliquots of 2 microliters (T4) and 5 microliters (T3), with minimum detectable levels of 100 ng/dl (T4) and 20 ng/dl (T3). In agreement with previous studies on other amphibians, we found metamorphosis in E. bislineata to be accompanied by a sharp increase in the circulating plasma levels of T3 and T4. No hormones were detectable in the larval and adult stages. Our technique allowed for simultaneous measurement of T3 and T4 levels in some individuals. These data indicated that, although both the onset of the production of the two thyroid hormones is simultaneous, T3 remains in the system longer than T4. However, at all metamorphic stages a large proportion of specimens did not exhibit any measurable levels of T3 and/or T4. These results underscore the need to reassess the mode of operation and production of thyroid hormones in amphibian metamorphosis.

Animals↗
PubMed1985

The fate of larval chondrocytes during the metamorphosis of the epibranchial in the salamander, Eurycea bislineata.

The metamorphosis of the epibranchial cartilage, a skeletal component of the hyobranchial apparatus, in the salamander Eurycea bislineata entails a combination of the reabsorption of a larval cartilaginous element with the simultaneous genesis of an adult cartilage in the same place. In this study we focus on the fate of the larval chondrocytes. Two hypotheses are considered: one, larval cells simply die off during metamorphosis, or, alternatively, they dedifferentiate and participate in the formation of the adult element. Thyroxine treatment and experimental tissue manipulation coupled with measurements of thyroxine levels using radioimmunoassay show that, within 24 h after T4 treatment, larval chondrocytes in the epibranchials exhibit large autophagocytic vacuoles, disruption of the rough endoplasmic reticulum, abnormally shaped mitochondria, abundance of lysosomes and nuclear degeneration, all symptoms of the onset of cell death. In conclusion, evidence from light microscopy, TEM and SEM show that the larval chondrocytes in response to rising levels of thyroid hormones undergo a process of lysosomal autophagocytosis and do not participate in the formation of adult structures.

Animals↗
PubMed1983

Size dependence during the development of the amphibian foot. Colchicine-induced digital loss and reduction.

Localized treatment of the limb buds of the frog, Xenopus laevis, and the salamander, Ambystoma mexicanum, with the mitotic inhibitor colchicine results in limbs that, when compared with the contralateral control, are smaller in size and have lost skeletal elements. There is a very well defined pattern in terms of what elements are most likely to be lost. For example, frogs that have lost a toe always lose the first toe, while salamanders always lose the fifth. These differences correspond to qualitative differences in developmental sequence of digital differentiation in anurans as compared to urodeles. We propose a hypothesis in which the digital pattern is indirectly affected by reduction in the number of mesenchymal cells in the embryonic field.

Ambystoma mexicanum↗