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Cell division in normal and mutant chick embryos
Başlık:
Cell division in normal and mutant chick embryos
Yazar:
Mohammed, Mohammed Rahgat Hussein, author.
ISBN:
9780438059054
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (359 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Advisors: D. A. Ede.
Özet:
The cellular activities which in concert produce the change of form and pattern observed in the limb development have been listed by Ede and Law (1969). These are mitosis, cell death, cell movements and orientations of any degree, and changes which occur in the course of cell differentiation to give the various tissue types - changes in size and shape and also in packing density through secretion of extracellular materials or other tissue. The effects of these activities on the developing shape of the limb will also be affected by any constraints imposed by overlying ectoderm. These parameters were examined in talpid3 and compared with normal embryos between stages 18 - 26. Of these, rates and distribution of mitosis along the entire limb are the most important parameters producing the increasing mass of the limb in both the normal Euid the talpid3 wing buds. Embryos from the mutant strain talpid were examined as the homozygous condition (ta3/ta3) provides an interesting deviation in appendicular skeletal elements. Changes in the patterns and rates of cell division in the chondrogenic regions were compared with changes in other areas of the limb; the data describe changing growth rates in the peripheral regions and in the subridge region of the limb as well as changes in the chondrogenic regions. The decrease in growth rate in the chondrogenic and peripheral regions of the wing is the result of cessation of cell division. There is a change in the cell-doubling time of the activigly proliferating cells. Talpid3 cells were found to have an increased cell division rate. Between stages 24 - 26 in the talpid3 mutant as well as in normal chick wings there is a gradient of mitosis which reveals differences between different regions of the limb. The results of the present investigation confirm the conclusion that there is no sign of relatively greater growth at the tip of the limb. In fact, these results indicate that the tip has a growth rate equal to or less than that of the proximal regions between stages 25-26. An important extension of the work of Ede is the observation by Wilby and myself that there is an initial proximo-distal gradient in talpid3 with a medial peak which only later gives a proximo-distal gradient similar in direction to normal rather than a series of blocks of tissue each with a uniform unchanging division rate. In both the normal and the talpid3, the development of the limb is divided into morphogenetic and cytodifferentiation phases. It is during the morphogenetic phase that certain tissues acquire properties which are characteristic only of limb tissues. During the phase of cytodifferentiation, cells acquire their specialised function. This phase includes the differentiation of cartilage and muscle, and these two cell types are defined in terms of the structure, regulation and prganisation of their tissue-specific macro-molecules, cell division and other parameters. The cells that are specified to form the different regions of the limb are intrinsically different, even though they may give rise to the same histological type. The cells from the proximal regions do not have quite the same character as those from the regions which will give the zygopodium or autopodium, or those from the whole peripheral jacket; there is something different in the mode of control of their differentiation. The vascular system also plays some part in limb pattern determination. The results recorded show that cell number, cell-doubling time, cell volume, limb volume and cell death are affected by the mutant gene at these early stages of development and continue to be important in the development of form in the limb bud, as well as affecting later stages, e.g. in producing abnormal cartilage development, fusion of limb elements and polydactyly. The data indicate that the ta3 gene not only affects the chondrogenic condensations but all the other regions of the mesenchyme. (Abstract shortened by ProQuest.).
Notlar:
School code: 0547
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(684682.1) | 684682-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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