Secretory cells, functions

Secretory cells, including neurons, also possess a specialized regulated secretory pathway. Vesicles in this pathway have soluble proteins, peptides or neurotransmitters stored and concentrated within secretory vesicles. At that point, these vesicles are actively transported to a site for extracellular delivery in response to a specific extracellular signal. Exocytosis through regulated secretion accomplishes different functions, including the... 

In the periphery, 5-HT4 receptor mRNA is found in vascular smooth muscle. Newly developed drugs that activate 5-HT4 receptors are of interest for their potential in treating cardiac arrhythmia. The 5-HT4 receptor is also located on neurons of the alimentary tract, for example the myenteric plexus of the ileum, and on smooth muscle cells and secretory cells of the gastrointestinal tract, where they evoke secretions and the peristaltic reflex. 5-HT4 receptor agonists (e.g. cisapride, prucalopride, tegaserod) are used therapeutically in the treatment of constipation-predominant irritable bowel syndrome and in functional motility disorders of the upper gastrointestinal tract. 

The general approach for the functional characterization of ESTs from an oil gland cDNA library is outlined in Fig. 9.2. The isolation of secretory cells was... 

Figure 9.2 Outline of a functional genomics approach to evaluate ESTs from a peppermint oil gland secretory cell cDNA library.

The peppermint oil gland secretory cell cDNA library has proven to provide a highly enriched source of candidate genes involved in essential oil biosynthesis. A functional genomics approach has successfully been employed to clone genes involved in the mevalonate-independent pathway of isoprenoid biosynthesis and in the peppermint-specific steps producing (-)-menthol and (-)-menthone. The optimization of LC-MS technology to profile phosphoiylated carbohydrates and... 

Segura M. Su Z. Piccirillo C. Stevenson MM Impairment of dendritic cell function by excretory-secretory products a potential mechanism for nematode-induced immunosuppression. 

INTESTINE Characterization of a membrane potassium ion conductance in intestinal secretory cells using whole cell patch-clamp and calcium-sensitive dye techniques, 192, 309 isolation of intestinal epithelial cells and evaluation of transport functions, 192, 324 isolation of enterocyte membranes, 192, 341 established intestinal cell lines as model systems for electrolyte transport studies, 192, 354 sodium chloride transport pathways in intestinal membrane vesicles, 192, 389 advantages and limitations of vesicles for the characterization and the kinetic analysis of transport systems, 192, 409 isolation and reconstitution of the sodium-de-pendent glucose transporter, 192, 438 calcium transport by intestinal epithelial cell basolateral membrane, 192, 448 electrical measurements in large intestine (including cecum, colon, rectum), 192, 459... 

The thin (8 nm) outer cell membrane or "plasma-lemma" (Fig. 1-7) controls the flow of materials into and out of cells, conducts impulses in nerve cells and along muscle fibrils, and participates in chemical communication with other cells. Deep infoldings of the outer membrane sometimes nm into the cytoplasm. An example, is the "T system" of tubules which functions in excitation of muscle contraction (Figs. 19-7, 19-21). Surfaces of cells designated to secrete materials or to absorb substances from the surrounding fluid, such as the cells lining kidney tubules and pancreatic secretory cells, are often covered with very fine projections or microvilli which greatly increase the surface area. 

The risk of post-transplant diabetes mellitus is greater with tacrolimus than with ciclosporin, but this was mostly true in black patients and during the initial months after transplantation (1084). In one study, insulin sensitivity, alpha and beta cell function, and beta cell reserve were studied in 14 hepatitis C-positive patients with liver transplants, who took tacrolimus or ciclosporin maintenance for 1 year (1085). The patients were matched for low prednisolone dosage (1.1 mg/day versus 1.3 mg/day), body mass index, lean body mass, and sex, and compared with eight controls. Insulin sensitivity and insulin secretory reserve were significantly different from controls, but there was no significant difference between ciclosporin and tacrolimus. 

As several types of secretory cells are present in some species (Fig. 8.16) it is possible that two or more types of secretions may be produced (443) and the functions of the glands may be more complex than is at present recognised. Considering that oncosphere secretions have been shown to be strongly antigenic and have been used as vaccines (Chapter 11), it is surprising that so little is known regarding their composition and this is an area that clearly calls for further work. 

Figure 5 Proteomics reveals functional secretory vesicle protein systems for neuropeptide biosynthesis, storage, and secretion. Chromaffin secretory vesicles (also known as chromaffin granules) were isolated and subjected to proteomic analyses of proteins in the soluble and membrane components of the vesicles. Protein systems in secretory vesicle function consisted of those for 1) production of hormones, neurotransmitters, and neuromodulatory factors, 2) generating selected internal vesicular conditions for reducing condition, acidic pH conditions maintained by ATPases, and chaperones for protein folding, and 3) vesicular trafficking mechanisms to allow the mobilization of secretory vesicles for exocytosis, which uses proteins for nucleotide-binding, calcium regulation, and vesicle exocytosis. These protein systems are coordinated to allow the secretory vesicle to synthesize and release neuropeptides for cell-cell communication in the control of neuroendocrine functions.

How can we define the molecular basis of specific phenotypic states Cells such as muscle or secretory cells must have characteristic patterns of biochemical reactions that support their structural properties and metabolic functions. The persistence of a cell in a steady phenotypic state suggests that the underlying network of metabolic reactions also operates in a steady state. The metabolic network is controlled by signaling molecules that promote or... 

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