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Biomedical subjects

W E Reif

Publications and source records attributed to W E Reif.

5 recordsLinked to original sources
PubMed1985

Constructional morphology: the analysis of constraints in evolution dedicated to A. Seilacher in honour of his 60. birthday.

Evolutionary change is opportunistic, but its course is strongly constrained in several fundamental ways. These constraints (historical/phylogenetic, functional/adaptive, constructional/morphogenetic) and their dynamic relationships are discussed here and shown to constitute the conceptual framework of Constructional Morphology. Notwithstanding recent published opinions which claim that the "discovery" of constraints renders Neodarwinian selection theory obsolete, we regard the insights of Constructional Morphology as being entirely consistent with this theory. As is shown here in the case of the Hyracoidea, formal analysis of the constraints which have framed the evolution of various characters extends our understanding of the evolution of a taxon.

Adaptation, Physiological↗
PubMed1980

Development of dentition and dermal skeleton in embryonic Scyliorhinus canicula.

Serial sections ranging from very young embryos to hatched juveniles and whole embryos of Scyliorhinus show that dentition and dermal skeleton belong to two independent secondary developmental fields that differ both developmentally and structurally. The development of the dentition starts very early, with a thickening of the ectoderm in the region of the mouth (stage 04), the invagination of the dental lamina (stage 18), and the formation of the germs of the first generation (stage 20). Tooth replacement movements start only near the end of embryogenesis (stage 35). Scale germs, on the other hand, first begin to form at stage 24. Scales erupt shortly before the animal hatches (stage 43). Only one scale generation is formed during embryogenesis. The forces which erupt the scales may come from fluid pressures in vacuoles of the fibrous layer of the dermis. Those which erupt the teeth probably also result from similar fluid pressures. The crown and upper part of the base of scales and teeth are formed by cells of the inner dental epithelium which are differentiated from the ectoderm. They are also formed by odontoblasts which are derived from the vascular layer of the dermis. However, the basal plates of scales and teeth containing the anchoring fibers are formed by osteoblasts, which are derived from the fibrous layer of the dermis.

Animals↗
PubMed1975

[Regulating and limiting factors in evolution].

It is shown in a literature review, that in the Typostrophic Theory autonomous mechnisms in the organism are considered as the factors which play a decisive role in orienting and controlling the evolutionary process. Selection is a controlling factor of only minor importance. The synthetic Theory, on the other side, says that phylogenetic changes are not random or controlled by "internal factors" but can always be considered as adaptive remodellings. They are achieved by selection acting on the variation within populations. Ecological, historical and "bautechnische" (fabricational) factors are considered as limiting mechanisms in the evolutionary process. They are discussed in detail in the text.

Adaptation, Biological↗
PubMed1975

[Scanning electron microscopy of the dental enamel from a dermoid teratoma].

Tooth enamel in the dermal teratoma is constructed very much like normal human tooth enamel, but is relatively less mineralized because of low phosphate supply. Prism bands are not present; the reasons for this are not clear. In the inner half of the enamel are numerous lumpy aggregates budded off from the tissue of the enamel organ. Enamel in the vicinity of these aggregates is abnormally constructed.

Dental Enamel↗