Ingestion mechanisms

Basic and advanced life-support measures should be utilized as necessary. Treatment is entirely symptomatic and supportive. Gastrointestinal decontamination with activated charcoal may be used depending upon the patient s clinical status, the history of the ingestion, and the time since the ingestion. Mechanical ventilation may be required for patients with decreased respiratory function. 

Control of secretion of anterior pituitary hormones also includes inhibition by hormones produced by target organs. For example, CRH stimulates the anterior pituitary to secrete ACTH, which in turn stimulates the adrenal cortex to secrete corticosteroids. Corticosteroids then feed back to inhibit the secretion of ACTH. Feedback mechanisms are important for the control of most hormones. For example, insulin (qv) secretion from the pancreas increases in response to increased blood glucose resulting from ingestion of a meal. Insulin increases tissue uptake and metaboHsm of glucose, which lowers blood glucose and in turn reduces insulin secretion. 

Facial dushing after ingestion of alcohol occurs in up to one-third of patients taking chlorpropamide. The mechanism, like that of the disulfiram reaction, probably involves inhibition of the oxidation of acetaldehyde, a metaboUte of ethanol. The plasma concentration of chlorpropamide may be correlated with chlorpropamide—alcohol dushing. 

As for other biological substances, states of dynamic equiUbrium exist for the various mineral nutrients as well as mechanisms whereby a system can adjust to varying amounts of these minerals in the diet. In forms usually found in foods, and under circumstances of normal human metaboHsm, most nutrient minerals are not toxic when ingested orally. Amounts considerably greater than the recommended dietary allowances (RDAs) can generally be eaten without concern for safety (Table 1) (3). 

Techniques for handling sodium in commercial-scale appHcations have improved (5,23,98,101,102). Contamination by sodium oxide is kept at a minimum by completely welded constmction and inert gas-pressured transfers. Residual oxide is removed by cold traps or micrometallic filters. Special mechanical pumps or leak-free electromagnetic pumps and meters work well with clean Hquid sodium. Corrosion of stainless or carbon steel equipment is minimi2ed by keeping the oxide content low. The 8-h TWA PEL and ceiling TLV for sodium or sodium oxide or hydroxide smoke exposure is 2 mg/m. There is no defined AID for pure sodium, as even the smallest quantity ingested could potentially cause fatal injury. 

There is a second type of cholinesterase called butyrylcholinesterase, pseudocholinesterase, or cholinesterase. This enzyme is present in some nonneural cells in the central and peripheral nervous systems as well as in plasma and serum, the liver, and other organs. Its physiologic function is not known, but is hypothesized to be the hydrolysis of esters ingested from plants (Lefkowitz et al. 1996). Plasma cholinesterases are also inhibited by organophosphate compounds through irreversible binding this binding can act as a detoxification mechanism as it affords some protection to acetylcholinesterase in the nervous system (Parkinson 1996 Taylor 1996). 

Genotoxicity. No reliable data in humans exist to indicate whether methyl parathion may act by a genotoxic mechanism. One study reported a temporary but significant increase in chromatid breaks and stable chromosomal aberrations in two subjects after ingestion of methyl parathion (Van Bao et al. 1974), but another study reported no significant differences in five subjects after ingestion of methyl parathion when compared with 15 controls (Czeizel 1994). A study that involved combined inhalation and dermal exposure of workers to methyl parathion showed no increase in chromosomal aberrations in their... 

Renal Effects. Hemorrhage of the medullary layer of the kidneys was observed in an early report of three fatal cases of acute oral poisoning with endosulfan (Terziev et al. 1974). More recent studies have reported acute renal failure after ingestion of endosulfan as a major contributing cause of death in two individuals in both cases, postmortem examination showed extensive tubular necrosis (Blanco-Coronado et al. 1992 Lo et al. 1995). Neither case discussed the possible mechanism of endosulfan-induced acute renal failure, but in one case, the authors of the report indicate that the renal lesions may relate to sepsis and shock (Blanco-Coronado et al. 1992). Ingested doses were not determined in any of these cases, and it is not totally clear that the effects observed at autopsy were a direct result of endosulfan exposure, although based on results from acute animal studies, it seems likely. 

Alcoholism leads to fat accumulation in the liver, hyperlipidemia, and ultimately cirrhosis. The exact mechanism of action of ethanol in the long term is stiU uncertain. Ethanol consumption over a long period leads to the accumulation of fatty acids in the liver that are derived from endogenous synthesis rather than from increased mobilization from adipose tissue. There is no impairment of hepatic synthesis of protein after ethanol ingestion. Oxidation of ethanol by alcohol dehydrogenase leads to excess production of NADH. 

Anthocyanins are poorly absorbed from the gastrointestinal tract and the mechanisms involved remain unclear. These compounds are usually recovered in very small amounts in human serum after oral ingestion (less than 1% of the dose) or in the IN fraction after in vitro digestion (about 5%). ° Unlike other polyphenols, anthocyanins constitute an exception because intact glycosides are recovered in the body (without deglycosylation prior to absorption). - This may be explained by either the instability of the free aglycone form or by a specific mechanism of absorption for anthocyanins. 

Mechanisms for transmitting toxin to host Ingestion, Inhalation, dermal contact, physical and biologic vectors ... 

Increased motility results in decreased contact between ingested food and drink and the intestinal mucosa, leading to reduced reabsorption and increased fluid in the stool. Diarrhea resulting from altered motility is often established after other mechanisms have been excluded. IBS-related diarrhea is due to altered motility. 

The site and mechanism of absorption of ingested americium are not known. Based on studies of plutonium, it is likely that americium absorption occurs, at least to some extent, in the small intestine. Studies of the absorption of plutonium in preparations of in situ isolated segments of small intestine of immature miniature swine indicate that absorption of actinides can occur along the entire small intestine, with the highest rates of absorption occurring in the duodenum (Sullivan and Gorham 1982). 

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