Chapter23克莱森缩合

Editor's Notes

• #28: Beri-beri                               "A certain very troublesome affliction, which attacks men,                               is called by the inhabitants Beri-beri (which means sheep).                              I believe those, whom this same disease attacks, with their                               knees shaking and legs raised up, walk like sheep.   It is a                              kind of paralysis, or rather Tremor: for it penetrates the                              motion and sensation of the hands and feet indeed                               sometimes the whole body..."                                                                                                              Jacobus Bonitus, Java, 1630       Thiamine deficiency usually causes weight loss, cardiac abnormalities, and neuromuscular disorders.   The classic thiamine deficiency syndrome in humans is beri-beri (sometimes called Kakke).   Thiamine is abundant in whole grains, usually in the scutellum (the thin covering of the starchy interior endosperm), but is scarce in the endosperm. Unfortunately beri-beri is still common in parts of southeast Asia where polished rice is a staple and thiamine enrichment programs are not fully in place.   Beri-beri is characterized by anorexia (loss of appetite) with subsequent weight loss, enlargement of the heart, and neuromuscular symptoms such as paresthesia (spontaneous sensations, such as itching, burning, etc.), muscle weakness, lassitude (weariness, general weakness), and foot and wrist droop.   There are three main types of beri-beri:   (1) dry (also neuritic, paraplegic, and pernicious) beri-beri; (2) wet (also edematous or cardiac) beri-beri; (3) and infantile (also acute) beri-beri.      Dry beri-beri usually inflicts older adults and affects mainly the peripheral nerves with little cardiac involvement.   It is characterized by atrophy (wasting away) and peripheral neuritis (inflammation of nerves) of the legs and paraplegia (paralysis of the lower extremities).   In contrast wet beri-beri displays substantial cardiac involvement especially tachycardia (rapid heart beat) in addition to peripheral neuropathy.   Edema progresses from the feet upwards to the heart causing congestive heart failure in severe cases.   Infantile beri-beri is usually seen in breast-feeding infants whose mothers are thiamine deficient (but not necessarily showing signs of beri-beri).   These infants are usually anoretic and often have trouble keeping the milk down.   Once the disease begins it moves rapidly causing heart failure in a matter of hours. Wernicke-Korsakoff Syndrome       Wernicke-Korsakoff Syndrome or Wernicke's encephalopathy is the thiamine deficient disease seen most often in the Western hemisphere.   It mainly affects alcoholics due to three reasons:   (1) the diets of alcoholics are usually poor; (2) diets rich in carbohydrates (e.g., alcohol or rice) increase the metabolic demands of thiamine; and (3) alcohol inhibits intestinal ATPase which is involved in the uptake of thiamine.   Two observations suggest a genetic invovlement with Wernicke-Korsakoff Syndrome: (1) it is much higher in among Europeans than non-Europeans; and (2) transketolase (see above under " Thiamine in the Pentose Phosphate Pathway") from Wernicke-Korsakoff Syndrome patients binds TPP 10 time less strongly than normal transketolase.   The symptoms of Wernicke-Korsakoff syndrome include confusion, sixth nerve damage resulting in ophthalmoplegia (paralysis of an eye motor nerve) and nystagmus (rhythmical oscillation of the eyes), psychosis, confabulation, and impaired retentive memory and cognitive function.   In severe cases the patient may slip into a coma.   A congenital defect in transketolase which causes a low binding affinity for TPP increases the chances of acquiring Wernicke-Korsakoff syndrome.