Secretory activity

Anthropologic features of humans, their physical activities, ventilation capacities, and the state of their circulation all affect exposure to chemical compounds. Some of the physiological determinants of exposure will be dealt with below. Exercise typically increases cardiac output, facilitates circulation, increases the minute volume of ventilation, is associated with vasodilation of the skin circulation, and increases perspiration and secretory activity of the sweat glands. All of these changes tend to facilitate the absorption of chemicals through multiple routes. 

As under most circumstances progesterone action will hold primacy over estrogenic effects, the cervical mucus, endometrium, and probably the fallopian tubes reflect progestational stimulation. The cervical mucus becomes thick and viscous and thus impervious to spermatozoa. The endometrium is in a state that is not receptive for implantation of a fertilized egg. Probably, the progestational impact on the secretory activity and peristalsis in the fallopian tubes also assists the general contraceptive effect. It is difficult, however, to assess the relative contribution of the various effects to the... 

M. Rougier, Secretory activity of the root cap. Plant Carbohydrates II, extracellular Carbohydrates Encyclopedia of Plant Physiolo>>y (W. Tanner and F. A. Lcowus, eds.), Springer Verlag, Berlin, Germany, 1981. 

Secretory diarrhea results in an increase in the net movement (secretion) of ions into the intestinal lumen leading to an increase in intraluminal fluid. Medications, hormones, and toxins may be responsible for secretory activity. 

Much as in other mammals, human females concentrate in their mammary regions features potentially related with infant-directed communication. The potential semiochemical significance of the human breast will be examined here in terms of 1) morphology and secretory activity of areolar skin glands 2) infant responses when exposed to the effluvium of their mother s breast and areolae, and to the odour of related secretions 3) volatile compounds present in pure areolar secretions as compared with those of milk 4) relations of maternal areolar gland endowment to adaptive outcomes in the infant and the mother. 

Many of the endocrine glands are listed in Table 4.1. This table includes not only the well-accepted hormone-secreting tissues but also those such as adipose tissue (see Chapter 9 for further details), which also have secretory activities. 

The problem we have not yet touched upon is how components can specifically move from one cellular component to another. Both the entry and the exit of SFV spike proteins are dependent on a number of such cellular processes. The newly synthesized spike proteins move from the ER to the Golgi complex and then to the cell surface. The cell surface membrane is continuously retrieved by endocytosis into endosomes. From here the endocytosed membrane components probably recycle back to the cell surface, but some components may also be channeled into lysosomes for degradation. Especially in cells with secretory activity, the recycling pathway from the cell surface also includes the Golgi complex (see Farquhar and Palade, 1981). 

The amount of parthenolide in capsules of the dried leaves given in two studies [5,60] measured as anti-secretory activity in platelets was estimated at 2-3 //mol by comparison with a known concentration of parthenolide. 

The hypothalamus is part of the brain. It is an important regulatory centre and produces a range of peptide-releasing and release-inhibiting hormones, which control the secretory activity of the pituitary. 

Using in vivo techniques, natural and synthetic fibrous materials have been shown to induce fibrosis and carcinogenic responses that were directly related to dose, if the materials were placed on the target tissues. Chrysotile appeared to be more biologically active than the other UICC asbestos samples or fibrous glass, with particle size and shape having some influence on the response. In vitro experiments indicate that fibers can be cytotoxic and possibly mutagenic, increase the secretory activity of fibroblasts, and possibly initiate an immune cascade. 

The hepatocyte secretes biliary fluid into the bile canaliculi (dark green), tubular intercellular clefts that are sealed off from the blood spaces by tight junctions. Secretory activity in the hepatocytes results in movement of fluid towards the canalicular space (A). The hepatocyte has an abundance of enzymes carrying out metabolic functions. These are localized in part in mitochondria, in part on the membranes of the rough (rER) or smooth (sER) endoplasmic reticulum. 

Causes of diarrhea (in red) Many bacteria (e.g., Vibrio cholerae) secrete toxins that inhibit the ability of mucosal ente-rocytes to absorb NaCl and water and, at the same time, stimulate mucosal secretory activity. Bacteria or viruses that invade the gut wall cause inflammation characterized by increased fluid secretion into the lumen. The enteric musculature reacts with increased peristalsis. 

Pharmacology Calcium is essential for the functional integrity of the nervous and muscular systems, for normal cardiac contractility and the coagulation of blood. It also functions as an enzyme cofactor and affects the secretory activity of endocrine and exocrine glands. 

Finally, compounds that undergo active tubular secretion also are filtered at the glomerulus (assuming protein binding is minimal). Hence, a reduction in secretory activity does not reduce the excretory process to zero but rather to a level that approximates the glomerular filtration rate. 

The liver secretes about 1 L of bile daily. Bile flow and composition depend on the secretory activity of the hepatic cells that line the biliary canaliculi. As the bile flows through the biliary system of ducts, its composition can be modified in the ductules and ducts by the processes of reabsorption and secretion, especially of electrolytes and water. For example, osmotically active compounds, including bile acids, transported into the bile promote the passive movement of fluid into the duct lumen. In the gallbladder, composition of the bile is modified further through reabsorptive processes. 

Renal elimination of foreign compounds may change dramatically with increasing age by factors such as reduced renal blood flow, reduced glomerular filtration rate, reduced tubular secretory activity, and a reduction in the number of functional nephrons. It has been estimated that in humans, beginning at age 20 years, renal function declines by about 10% for each decade of life. This decline in renal excretion is particularly important for drugs such as penicillin and digoxin, which are eliminated primarily by the kidney. 

General activation of the sympathetic system during stress, fear, or anxiety is accompanied by increased secretion of adrenal medullary hormones, which consist primarily of epinephrine in the human. The secretory activity of the adrenal medulla is regulated by the CNS. 

Endothelial cells produce vasoactive substances, which modulate the permeability of vessel walls accordingly, shear stresses may indirectly affect this wall parameter by influencing the secretory activity of endothelial cells. 

This beneficial effect of fluorination on hydrolytic stability has also been demonstrated with the synthetic prostaglandin SC-46275 (Fig. 70). This compound possesses an anti-secretory activity that protects the stomach mucous membrane. However, its clinical development was too problematic because of the instability of the tertiary allyl alcohol in acidic medium (epimerisation, dehydration, etc.). A fluorine atom was introduced on the C-16 methyl to disfavour the formation of the allylic carbocation. This fluorinated analogue possesses the same biological activity, but does not undergo any degradation or rearrangement, and itepimerises only slowly [165]. 

Mechanism of Action An acetylcholine antagonist that inhibits the action of acetylcholine by competing with acetylcholine for common binding sites on muscarinic receptors, which are located on exocrine glands, cardiac and smooth-muscle ganglia, and intramural neurons. This action blocks all muscarinic effects. Therapeutic Effect Decreases GI motility and secretory activity, and GU muscle tone (ureter, bladder) produces ophthalmiccycloplegia, and mydriasis. 

Effect on smooth muscles Acetylcholine causes increase in tone, amplitude of contractions, peristalsis and secretory activity of the gastrointestinal tract. It causes contraction of smooth muscles of gall bladder and relaxation of sphincters of gastrointestinal and biliary tract. 

These drugs exert their laxative action by increasing motility of colon. They mainly alter absorptive and secretory activity by inhibiting Na+ ATPase in mucosal cells, leading to water and electrolyte accumulation in lumen. Colicky pain may occur and on the... 

Dicyclomine Competitive antagonism at M3 receptors Reduces smooth muscle and secretory activity of gut Irritable bowel syndrome, minor diarrhea Available in oral and parenteral forms short t1/2 but action lasts up to 6 hours Toxicity Tachycardia, confusion, urinary retention, increased intraocular pressure Interactions With other antimuscarinics... 

Regulates body temperature via thyroxine Maintains thyroid gland and its secretory activity (colloid discharge)... 

Pygeum africanum, an extract from the bark of the African prune tree, has been used in Europe since 1969 to treat men with mild to moderate symptoms of benign prostatic hyperplasia. The mechanism of action of P. africanum is not known. In animal models, P. africanum modulates bladder contractility, has anti-inflammatory activity, decreases production of leukotrienes and other 5-lipoxygenase metabolites, inhibits fibroblast production, affects adrenal androgens, and restores the secretory activity of prostate epithelium. 

As Ca2+ is important for endocytosis, the sustained secretory activity in its absence eventually depletes NMJ terminals (Longenecker et al. 1970 Ceccarelli and Hurlbut 1980), but not synaptosomes (Watanabe and Meldolesi 1983), of all vesicles. Electrophysiological recordings at NMJs show that in the absence of Ca2+a-LTX causes a large but slow rise in the frequency of spontaneous exocy-totic events, which then slow down and cease altogether bursts of miniatures are never observed. 

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