Proximal cytoplasm

The terminology in the literature is confusing. Terms used for the outer (nucleate) zone include syncytial layer, surface layer, distal cytoplasm, tegument and for the inner (nucleated) zone perikarya, proximal layer, tegumental cells, cytons, perinuclear cytoplasm. Bearing in mind that descriptive terms are more likely to be remembered and used correctly than non-descriptive words, the terms distal cytoplasm and proximal cytoplasm, which are well established in the literature, are used in this text, for these zones. The term tegumental cytons is used for the basic cells which make up the syncytial epithelium (Fig. 2.1). 

Two nonsynonymous polymorphisms have been identified (4-6), at amino acid 49 within the amino-terminus of the receptor and in the proximal cytoplasmic tail within the proposed eighth a-helix at amino acid 389. There are discrepant reports regarding the effects of the Ser Gly substitution at position 49 on receptor function. In one report, basal and agonist-stimulated adenylyl cyclase activities were... 

In principle, RTK autophosphorylation could occur in cis (within a receptor monomer) or in trans (between two receptors in a dimer). In the first case, ligand binding would cause a change in receptor conformation that would facilitate c/ s-autophosphorylation of tyrosine residues located within or outside the PTK domain. In the second case, no conformational change must occur upon dimerization. The simple proximity effect would provide sufficient opportunity for trans-phosphorylation of tyrosines in the cytoplasmic domain by a second RTK. 

FIGURE 1-19 A myelinated PNS axon (A) is surrounded by a Schwann cell nucleus (N). Note the fuzzy basal lamina around the cell, the rich cytoplasm, the inner and outer mesaxons (arrows), the close proximity of the cell to its myelin sheath and the 1 1 (celhmyelin internode) relationship. A process of an endoneurial cell is seen (lower left), and unstained collagen (c) lies in the endoneurial space (white dots). X20,000. 

The process of infection of lupine nodule cells by Rhizobia was examined by the thin-section electron microscopic technique, as well as the freeze-fracture technique. Different membranes such as infection thread membranes, peribacterioid membranes, plasma membranes, membranes of cytoplasmic vesicles, and membranes of the Golgi bodies and ER were stained with uranium-lead, silver, phosphotungstic acid, and ZIO (31). ZIO stained the membranes of the proximal face of the Golgi bodies and endoplasmic reticulum. ZIO staining has given good contrast in thick sections such as a cotyledon cell, a root cell, and an aleurone layer for ER, dictyosomes cisternae, mitochondria, and nuclear envelopes (17,32-37). 

After administration of mercuric chloride to adult rat kidneys, several changes were found, for example, pars recta of the proximal tubular segment showing fragmentation and disruption of the plasma membrane, basophilic staining, vesiculation and disruption of endoplasmic reticulum and other cytoplasmic membranes, mitochondrial swelling, loss of mitochondrial dense granules and condensation of nuclear chromatin [223-225]. 

The cytoplasmic NAD-reducing hydrogenase (SH) of the bacterium R. eutropha is a heterotetrameric enzyme, which contains several cofactors (Friedrich et al. 1996 Thiemermann et al. 1996). The Ni-containing subunit is called HoxH. This subunit plus the small subunit HoxY form the strictly conserved hydrogenase module with the Ni-Fe centre and a proximal [4Fe-4S] cluster. HoxF and HoxU represents the Fe-S/flavoprotein moiety which is closely related to a similar moiety in NADHrubiquinone oxidoreductase. The SH has been subject to molecular biological techniques in order to study its modular structure, mechanism and biosynthesis. 

The reason that host proteins are excluded from the plasma membrane segment enclosing the nudeocapsid is due probably to their lack of affinity for the capsid protein (Garoff and Simons, 1974). The apposition of the spike proteins on the external side of the bilayer and the close proximity of the nudeocapsid to the cytoplasmic face of the bilayer may effectively prevent host proteins from becoming included in the viral particle. 

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