Maturation morphological changes

Corroborative data have been obtained by extensive studies of iodine deficiency in sheep (Hetzel and Mano, 1994). In these animals, induced iodine deficiency results in reduced brain weight, a reduction in brain DNA and retarded myelination. In keeping with earfier observations, morphological changes in the cerebellum accompanied by delayed maturation were noted (Hetzel et ai, 1989). 

From fertilization until delivery of the mature fetus, cells proliferate and differentiate. The morphological changes in the development of the embryo into a mature infant have been described in detail by embryologists. In contrast, little is known of the detailed molecular alterations associated with each stage of embryonic development. As a result, the biochemistry of growth and development can be described only superficially. 

Maturation or aging is accompanied by morphological changes which primarily affect the cytoskeleton. Microexaminations show that the Z lines, which as cross structures (cf. 12.2.1) separate the individual sarcomeres in the muscle fibril, are broken up during aging. In addition, the fibrillar proteins titin and desmin are degraded. In comparison, the contractile proteins myosin and actin are stable. They are attacked only at temperatures above 25 °C. The connective tissue present outside the muscle cells also remains intact. 

Around birth the CB increase in size. In the cat, between the late fetal and the early postnatal period, the CB volume increases by over 50% in vascular and nonvascular compartments (61). In the rat, glomus cells occasionally have been reported to undergo mitosis during the late fetal and early postnatal period (62,63). The number of nerve terminals increases about fourfold during the neonatal period (64). These morphological changes could participate in the functional and neurochemical maturation of this tissue. 

Cell activation can lead to differentiation of certain cells into more mature cells that exhibit different structural and functional form. For example, immature hematopoietic cells can be stimulated by some proteins to mature, by changing cell morphology and by inducing expression of different intracellular and surface markers. Expression of differentiation markers can be detected and monitored by flow cytometry using specific antibodies against cell surface or intracellular markers. 

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