Chromosomes Ultrastructure

DNA and Chromosome Structure 104 Chromosome Ultrastructure 104 The Mitotic Apparatus 105... 

Aist JR, Berns MW 1981 Mechanics of chromosome separation during mitosis in Fusarium (Fungi imperfectly, new evidence from ultrastructural and laser microbeam experiments. J Cell Biol 91 446-458... 

Mutant Tbce mice. Progressive motor neuropathy (PMN), an autosomal recessive murine disease, manifests as weakness beginning within a few weeks of birth [14, 136]. These mice are homozygous for a Trp 524 Gly substitution of Tbce (tubulin-specific chaperone E), localized to mouse chromosome 13 [14]. Tbce mRNA is present in neurons in the spinal cord. Degenerative changes are conspicuous in motor axons, and ultrastructural studies of peripheral nerves of PMN mice disclose reduced numbers of microtubules in these axons. Mutations of the highly conserved Trp524 residue, which appears to influence... 

The Ewing family of tumors comprises small round cell neoplasms of bone and soft tissue that are, in part, defined by a particular chromosomal aberration [t(ll 22)] and variants thereof. Over the past 15 years, it has become clear that ES and peripheral PNET are part of the same spectrum of neoplastic proliferations. Besides the karyotypic marker just mentioned, both of those tumor types also show neuroectodermal features in tissue culture and similarities in proto-oncogene expression. As classically defined, ES was distinguished from PNET by an absence of pseudorosettes and the lack of ultrastructurally or immunohistochemically detectable neuroectodermal features. However, this diagnostic separation is now considered to be antiquated and has been abandoned. 

Cytogenetically MTSCs show multiple chromosomal losses (1, -4, -6, -8, -9, -13, -14, -15, and -22). Differentiation toward loop of Henle, distal convoluted tubule, or collecting ducts has been suggested by their overall immunoprofile and ultrastructural features. 

As an alternative, our laboratory has developed a novel method of tagging specific chromosome regions using protein/DNA interactions a 256 lac operator repeat serves as a target for lac repressor binding. This methodology avoids the requirement for in situ hybridization and allows improved ultrastructural preservation (Robinett et al., 1994, 1996 Li et al., 1995). Used in conjunction... 

Brinkley, B. R. (1969), Ultrastructural aspects of chromosome damage, in Genetic Concepts and Neoplasia, University of Texas Press. 

It is obvious from this description that the chromosome is the most important element in mitosis, and that at the end of mitosis, each chromosome has produced an exact replica of itself that is transferred to a daughter cell. What is it in the chromosomal structure that makes such replication possible An answer to that vital question was sought by studying the ultrastructure and the chemical composition of the chromosome. 

Evidence indicating that, in interphase nuclei, the chromosomes are attached to the nuclear membrane comes from ultrastructural studies and from analysis of the segregation of newly synthesized DNA. Woollam et al. (1967) describe attachment of both distal and centro-meric ends of pachytene chromosomes to the nuclear membrane of mouse spermatocytes moreover, these authors suggest, on the basis of the nearness of centromeric attachments to the sex vesicle in these cells, that centromeric and distal attachment points are at opposite poles of the nucleus (cf. also, Sved, 1966). Davies and Tooze (1966) have examined mitotic chromosomes of newt erythroblasts, a cell type characterized by scarcity of endoplasmic reticulum. In interphase erythroblasts, numerous areas are found where chromatin appears to be closely associated with the nuclear membrane. At mitosis the chromosomes are observed to carry fragments of nuclear membrane, sometimes appearing as membrane-limited sheets of chromatin, continuous with the chromosomes. 

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