The adult carbohydrate metabolism

Mecfianism of Action A cinchona alkaloid that relaxes skeletal muscle by increasing the refractory period, decreasing excitability of motor end plates (curare-like), and affecting distribution of calcium with muscle fiber. Antimalaria Depresses oxygen uptake, carbohydrate metabolism, elevates pH in intracellular organelles of parasites. Therapeutic Effect Relaxes skeletal muscle produces parasite death. Pharmacokinetics Rapidly absorbed mainly from upper small intestine. Protein binding 70%-95%. Metabolized in liver. Excreted in feces, saliva, and urine. Half-life 8-14 hr (adults), 6-12 hr (children). 

Q3 The thyroid hormones thyroxine and triiodothyronine have many metabolic effects. In adults they increase metabolic rate, oxygen and calorie consumption, stimulate carbohydrate metabolism and turnover of protein, deplete fat stores and increase catabolism of free fatty acids. Thyroid hormones stimulate heart rate and force and increase pulmonary ventilation, gastrointestinal motility and central nervous system (CNS) activity. Actions on the heart can result in an increased incidence of dysrhythmias. Thyroid hormones are critical for the normal growth and development of the infant, particularly in respect of skeletal growth and maturation of the CNS. 

Propofol infusion syndrome mimics the mitochondrial myopathies, in which there are specific defects in the mitochondrial respiratory chain. The clinical features of mitochondrial myopathy result from a disturbance in lipid metabolism in cardiac and skeletal muscle. These patients generally remain well until stressed by infection or starvation, although subclinical biochemical abnormalities of mitochondrial transport can be demonstrated. It has been suggested that early management of critically iU children may not include adequate calorific intake to balance the increase in metabolic demands, and that in susceptible children the diversion of metabolism to fat substrates may cause the propofol infusion sjmdrome. It is unclear if the dose or duration of propofol infusion alters this effect. As adults have larger carbohydrate stores and require lower doses of propofol for sedation, this may account for the relative rarity of the sjmdrome in adults. The authors suggested that adequate early carbohydrate intake may prevent the propofol infusion syndrome (71). 

Recently it has been shown that strain differences in helminths may lead to differences in end products. Kolhagen and coworkers [26] found a variation from 30-60% in the production of lactate in different strains of H. diminuta. It has been reported by McManus [27] that carbohydrate metabolism in adult schistosomes may exclusively lead to lactate formation and that homolactate fermentation is not per se essential for generating ATP in these worms. 

Another area of considerable conceptual difficulty relates to the observation that the adult animal exists in a more-or-less steady-state, well removed from equilibrium. When observed day-to-day there is generally little variation in body composition while the animal is on a consistent diet, the mass of protein, carbohydrate, and fat remaining approximately constant. This constancy is maintained despite the rapid turnover of the body s constituents. The living system is not static but dynamic, the steady-state being maintained because synthetic reactions exactly balance degradative processes. How this balance is achieved and what governs the overall rate of metabolic flux and heat production are the main topics of this section. 

Thyroxine (also known as Levothyroxine or T4) is the ultimate metabolism regulator. Its reactions and products influence carbohydrate metabolism, protein synthesis and breakdown, and cardiovascular, renal, and brain function. Thyroxine is essential to an animal s functions and it is essential for development in the young. Tadpoles won t develop into frogs, for example. Untreated human babies will develop cretinism, a condition marked by severe mental and physical retardation. Adult humans with low thyroxine levels (hypothyroidism) suffer mental slowness, weight gain, depression, and fatigue. ... 

In his review of the relations between the adrenal cortical hormones and carbohydrate metabolism, Verzdr (1952) lemarked that the present situation may be described briefly as follows the action of the adrenal cortex is related to the central process of energy production of the cell, which is the degradation or transformation of glucose. This being the case it could be expected that these hormones would also prove to have an influence on mitotic activity, at least in tissues of the type of adult mouse epidermis in which the rate of energy production is low. 

A number of hormones are known to influence the course of carbohydrate metabolism, and these have all been shown to influence the epidermal mitotic rate of adult mice. Those hormones which stimulate the rate of energy production also stimulate the rate of epidermal mitosis, whereas those which inhibit energy production also inhibit epiderm mitosis. 

These are in vivo tests used for the investigation of carbohydrate metabolism. They consist of giving an oral glucose load (usually SO g for adults) to fasting subjects followed by the collection of blood and urine samples at intervals for up to two hours or sometimes longer. There are several types of abnormal curve. 

Thiamin is the least stored of all the vitamins. The adult human body contains approximately 30 mg. Of the thiamin stored in the body, about 80% is thiamin pyrophosphate, about 10% is thiamin triphosphate, and the remainder is thiamin monophosphate. The liver, kidneys, heart, brain, and skeletal muscles have somewhat higher concentrations than the blood. If the diet is deficient, tissues are depleted of their normal content of the vitamin ini to 2 weeks, so fresh supplies are needed regularly to provide for maintenance of tissue levels. Body tissues take up only as much thiamin as they need with the need increased by metabolic demand (fever, increased muscular activity, pregnancy, and lactation) or by composition of the diet (carbohydrate increases the need for thiamin, while fat and protein spare thiamin). Because thiamin is water soluble, most of the vitamin not required for day-to-day use is excreted in the urine. This means that the body needs a regular supply, and that unneeded intakes are wasted. With a well-balanced diet, approximately 0.1 mg is normally excreted every 24 hours. However, the amount excreted in the urine decreases as the intake becomes inadequate and increases as the intake exceeds body needs because of this, the most widely used biochemical method to assess thiamin status in individuals is the measurement of the vitamin in the urine. 

The differences in metabolism between dextrose and fructose were investigated 30-40 years ago (Burger, 1921 Wierzuchowski, 1926 Cori and Cori, 1928 Bollman and Mann, 1931, 1934) but the influence of different dietary carbohydrates on the accumulation of liver lipid has only recently been investigated. It has been reported that dietary sucrose induced greater liver fat deposition than dextrin in male weanling rats (Litwack et al, 1952) and in adult male rats (Marshall and Wormack, 1954) and that fructose was like sucrose in this respect (Harper et al., 1953). The total content of fat and cholesterol in the liver was found to be less in male rats fed cornstarch than in sucrose-fed animals (Adams et al., 1959) but the reverse has also been reported (Guggenheim et al., 1960). In adult rabbits of both sexes it has been shown that the amount of liver lipid is related not only to the amount... 

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