Other problem

Other problem facing to researchers, working in the field of biosynthesis of polypeptide hormones, consists in how biosynthetic and secretory processes are regulated. Researches mechanisms are conducted in two directions: 1 - studying of the nature of cellular mechanisms, - participating in interface extracellular stimulus with the intracellular processes defining changes of formation and liberation of hormones; 2 - definition of a stage of synthesis of fiber on which regulation is referred, i.e. Finding-out occurs it on (and ), transmitting or posttransmitting level. SUBCELLULAR MORPHOLOGY OF THE CELLS COSECRETING ALBUMINOUS HORMONES Appreciably thanks to works Palade and . many order purchase ultram online data concerning morphology of ways used by a cell have been received. Synthesising squirrel for export. Some subcellular morphological features are inherent various to cells. Such cells contain set of the organellas surrounded with membranes: endoplasmatic , lamellar complexes (apparatus Goldzhi) and varying number of secretory granules The fibers intended for secretion, get to these subcellular organellas and are transported in them. Cosecreted fibers are synthesised on rough endoplasmatic , consisting of the polyribosomes attached to difficult arranged membranous saccules, containing tanks. Again synthesised fibers quickly get access to tanks at the expense of transport through a double layer of lipids of a membrane. On tanks endoplasmatic fibers are transported in a lamellar complex or by direct carrying over through tanks which proceed in membranous channels of a lamellar complex, or by means of the blisters making shuttle movement named transitive elements ( 3-3 see).
Different secretory cells, apparently, mainly use this or that mechanism of transport of fiber from in a lamellar complex. In a complex there is a packing of fibers in secretory blisters and-or secretory granules. The secretory blisters surrounded with a membrane gemmate from a lamellar complex in the form of the unripe granules which are exposed in process of inspissation of albuminous contents to maturing. Fiber liberation in extracellular space occurs by migration of secretory granules on periphery of a cell and merge of the membrane covering granules, to a plasmatic membrane (exocytosis), as leads to an exit of fibers from a cell. Though it is definitive and is not proved, but some biologists consider, that secretion of albuminous hormones can occur also by intracellular transport and liberation of the fibers containing in secretory blisters and unripe secretory granules ( 3-3) [3L see If such alternative-way secretions really exist in addition to the mechanism of formation and an exocytosis of mature granules there is a possibility of that different extracellular stimulating factors differ from each other the comparative efficiency concerning modulation of secretion of a hormone by that or other by. For example, it would be possible to assume, that the secretion of insulin caused by a glucose, on the one hand, is vpxl successfull and calcium or ?-adrenergic agonists - with another, it is carried out by various secretory ways, or that the part of secretion of the parathyroid hormone, not suppressed by the raised level of extracellular calcium, is liberated by, differing from ways. BIOSYNTHESIS WAY Appreciable interest was caused by opening of synthesis of albuminous and polypeptide hormones in the form of larger precursors, which then by splitting are modified in fineer ( 3-4) . Actually albuminous and polypeptide hormones make only one of many classes of the fibers synthesised as precursors. As examples of fibers. Various classes the seralbumin, proteins of egg white, an antibody, collagen, pancreas enzymes, the fibers virus and bound to membranes can serve. Efforts of researchers are focused now on finding-out of a physiological role of biosynthetic precursors on a way of formation of hormones, and also a general meaning of precursors of cosecreted fibers. One of probable functions of sequence of precursors is visible on an insulin example. S-peptid proinsulin - the connecting peptide binding And - and the V-chains of insulin - takes part, apparently, in correct assemblage of chains, framing possibility of effective formation of disulfide communications. Such stabilising function should take place only with reference to the limited number of cosecreted fibers, such, as insulin as many fibers exist in the form of the single polypeptide chains deprived of disulfide ponticuluses. Now there are representations in favour of a probable role of precursors in the posttransmitting processes causing intracellular transport and of hormones on a course of a secretory way . This hypothesis known under the name alarm, is offered Mistein and . [5], and also Blobel and Sabatini for the molecular mechanism with which help the fibers intended for secretion from a cell, selectively get access to the subcellular organellas surrounded with membranes, participating in their transport, packing and secretion. On the basis of the model resulted on 3-5, it is possible to explain a way of biosynthesis of a parathyroid hormone as the representative of polypeptide hormones taking into account positions of an alarm hypothesis.