Digestive tubules

Owen, G. (1970). The fine structure of the digestive tubules of the marine bivalve Cardium edule, Phil. Trans. Roy. Soc. Lond. Ser. B., 258, 245-260. 

Threatened or wounded sea cucumber Holothuraided) will contract its body exposing the small skeletal bones that make up the body wall, which can act as hooks to the mouths of predators. For most species, the connective tissue that makes up the greater part of the body wall is the primary deterrent to predators.The contracted body not only makes a more compact body to bite, but increases the stiffness of the body wall. The sea cucumber also has a very unusual defense mechanism. Many species use the Cuvierian tubules, which are located in the digestive system of the animal to confuse... 

Oxalic acid may have a direct corrosive effect on the eyes, skin, and digestive tract after contact. However, once absorbed (or produced as a result of the metabolism of other compounds), oxalic acid and other soluble oxalates react with calcium in the plasma to form insoluble calcium oxalate. Systemic formation of calcium oxalate may produce hypocalcemia directly. Precipitation of calcium oxalate in the renal system (proximal tubules of the kidney) may lead to local necrosis of the tubular epithelium, producing kidney dysfunction and electrolyte imbalance. Precipitation of calcium oxalate may also occur in the blood vessels, heart, lungs, and liver leading to local effects. 

Elemental mercury is mainly hazardous as vapor. There is less danger of absorbing the metal for the digestive tract. Like the alkylmercurials, elemental Hg affects the central nervons system, accompanied with such symptoms as tremors, irritability, and sleeplessness. Kidney damage is also reported due to influence of inorganic mercury salts due to a complexation of mercury by the protein metallothionein, which accumulates in the renal tubules. 

Toxicology LD50 (oral, rat) 6200 mg/kg, (IP, mouse) 870 mg/kg, (subcut., mouse) 1300 mg/kg, (IV, mouse) 62 mg/kg poison by IV route mod. toxic by IP, subcut. routes mildly toxic by ing. may cause skin/eye/respiratory/digestive tract irritation may cause flaccid paralysis, somnolence, convulsions, changes in tubules (incl. acute renal failure) TSCA listed Hazardous Decomp. Prods. Heated to decomp., emits toxic fumes of POx and Na20 HMIS Health 1, Flammability 0, Reactivity 0 Storage Store in cool, dry place in a tightly closed container... 

Some of the other functions which utilize active transport are (1) the secretion of saliva, gastric juice, and pancreatic juice during digestion (2) absorption of glucose and amino acids from the intestine (3) accumulation of calcium, manganese, magnesium, and phosphate ions within the mitochondria of cells and (4) reabsorption of glucose and amino acids from the kidney tubules. 

The enzymatic activation of xenobiotics is known to take place in those organs in which the endoplasmic reticulum is developed. In insects, these functions are believed to be executed in fat bodies, Malpighian tubules, and various parts of the digestive tract. The age-activity profile of the relevant enzyme(s) in the silkworm shows that the most potent activity is seen in the late larval stage hence, the detection can be most effectively carried out by administering a test compound at this stage. 

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