Blood, maintaining

How do buffers in human blood maintain the blood s pH In the Chemistry Course Challenge, you will learn about the buffer system in blood. 

The question often arises whether a sample must be analyzed immediately or can be stored, and if so, under what conditions and for how long (B4a, H5a, W9a). Freshly drawn blood maintained anaerobically (A3) at 38 C decreases in pH at the rate of —0.062 unit per hour and in pCOj, at 4.8 1.3 mg Hg per hour. At 0-4°C, the change is minimal — 0.006 0.004 pH unit and 0.6 0.06 mm Hg. There has been controversy concerning the use of minerol oil to maintain specimens for carbon dioxide analysis (G2). Paulsen found that values of total carbon dioxide in plasma collected in stoppered tubes with and without paraflSn oil were identical if the tubes without oil were completely filled to the stopper (P4). The loss of carbon dioxide in tubes stored at room temperature without oil was about 6 mEq/1 in 2.5-4 hours. The problem for the laboratory is unfilled tubes and the storage of separated serum or plasma before analysis and in plastic cups during continuous-flow procedures. 

How is the concentration of glucose in the blood maintained (a) during rest after a carbohydrate-rich meal and (b) during prolonged exercise ... 

Why do some lakes become acidic when showered by acid rain, while others remain unaffected How does blood maintain a constant pH in contact with countless cellular acid-base reactions How can a chemist sustain a nearly constant [H30 ] in reactions that consume or produce HsO" or OH The answer in each case depends on the action of a buffer. 

Besides calcium and 1, 25-(0H)2D3, phosphorus plays an important role in the regulation of 1, 25-(0H)2D3 levels in blood. Maintaining rats on a low phosphorus diet results in a marked accumulation of 1,25-(OH)2D3 in blood even in the absence of the parathyroid gland Furthermore, phosphate deprivation in thyroparathy-roidectomized rats will bring about a stimulation of 1,25-(OH)2D3 accumulation in blood and tissue. Thus in thyroparathyroidectomized rats a clear inverse relationship between serum inorganic phosphorus levels and 1,2S-(OH)2D3 accumulation has been demonstrated Under conditions of low blood phosphorus, 1,25-(OH)2D3... 

The liver removes toxins from the blood, maintains the levels of blood sugars and produces protein for the blood plasma. Hazardous substances can cause the liver to be too active or inactive (e.g. xylene), lead to liver enlargement (e.g. cirrhosis caused by alcohol) or liver cancer (e.g. vinyl chloride). 

How does blood maintain such a narrow pH range Like all buffers, blood contains significant amounts of both a weak acid and its conjugate base. When additional base is added to blood, the weak acid reacts with the base, neutralizing it. 

This difference in behavior for acetic acid in pure water versus water buffered at pH = 7 0 has some important practical consequences Biochemists usually do not talk about acetic acid (or lactic acid or salicylic acid etc) They talk about acetate (and lac tate and salicylate) Why Its because biochemists are concerned with carboxylic acids as they exist in di lute aqueous solution at what is called biological pH Biological fluids are naturally buffered The pH of blood for example is maintained at 7 2 and at this pH carboxylic acids are almost entirely converted to their carboxylate anions... 

Alcohol. The number of driving under the influence of alcohol (DUl) cases reflects the enormity of the dmnken driving problem in the United States (9). Tests to measure blood alcohol concentration are conducted on blood, urine, or breath (10). In the case of urine and breath, the alcohol concentration measured is reported in terms of the equivalent blood alcohol concentration. Most states in the United States presume that a person is under the influence of alcohol with respect to driving a motor vehicle at a blood alcohol concentration of 0.10%, ie, an ethanol concentration >10 g/100 mL of blood. Some states maintain a lower necessary concentration of 0.08%. In some European countries levels are as low as 0.05%. A blood alcohol concentration of 0.10% in a 68-kg (150-lb) person is the equivalent of about four drinks of 80 proof alcohoHc beverage or four 340-g (12-oz) beers in the body at the time of the test (see Beer Beverage spirits, distilled Wine). Ethanol is metabolized at the equivalent rate of about one drink per hour. 

A small (25-kg), portable apheresis system, available in 1993, is designed to meet a wide variety of blood cell separation needs. The role of the apheresis system is to control the behavior, separation, and collection of blood components from the bowl while maintaining maximum donor safety. The system controls the flow rates of blood and components through variable pump speeds. It directs the flow of components out of the bowl, by fully automatic opening and closing of valves based on the output of the system sensors. The system monitors the separation of blood components in the bowl by an optics system that aims at the shoulder of the bowl. A sensor on the effluent line monitors the flow of components out of the bowl. 

Plasma Collection. Human plasma is collected from donors either as a plasma donation, from which the red cells and other cellular components have been removed and returned to the donor by a process known as plasmapheresis, or in the form of a whole blood donation. These are referred to as source plasma and recovered plasma, respectively (Fig. 1). In both instances the donation is collected into a solution of anticoagulant (146) to prevent the donation from clotting and to maintain the stabiUty of the various constituents. Regulations in place to safeguard the donor specify both the frequency of donation and the volume that can be taken on each occasion (147). 

Table 11 summarizes values for the median lethal dose (LD q) for several species. In case of massive exposure, convulsions must be controlled, and glucose, fluid balance, and uriaary output must be maintained. Medical surveillance requires checking for damage to the Hver, the organ that apparently sustains initial damage, and monitoring for changes ia the blood profile. 

NIDDM is a much more common disease than IDDM, accounting for about 85—90% of all cases of diabetes meUitus. Whereas NIDDM may be present at any age, the incidence increases dramatically with advanced age over 10% of the population reaching 70 years of age has NIDDM. Patients with NIDDM do not require insulin treatment to maintain life or prevent the spontaneous occurrence of diabetic ketoacidosis. Therefore, NIDDM is frequendy asymptomatic and unrecognized, and diagnosis requires screening for elevations in blood or urinary sugar. Most forms of NIDDM are associated with a family history of the disease, and NIDDM is commonly associated with and exacerbated by obesity. The causes of NIDDM are not well understood and there may be many molecular defects which lead to NIDDM. 

Metabolites of vitamin D, eg, cholecalciferol (CC), are essential in maintaining the appropriate blood level of Ca ". The active metabolite, 1,25-dihydroxycholecalciferol (1,25-DHCC), is synthesized in two steps. In the fiver, CC is hydroxylated to 25-hydroxycholecalciferol (25-HCC) which, in combination with a globulin carrier, is transported to the kidney where it is converted to 1,25-DHCC. This step, which requites 1-hydroxylase formation, induced by PTH, may be the controlling step in regulating Ca " concentration. The sites of action of 1,25-DHCC are the bones and the intestine. Formation of 1,25-DHCC is limited by an inactivation process, ie, conversion of 25-HCC to 24,25-DHCC, catalyzed by 24-hydroxylase. 

Some tablets that provide a sustained period (up to 8—12 h) of therapy may be coated during processing. A portion is released first to bring the dmg to the desired blood concentration (onset of activity), whereas a sustained-release portion maintains an effective level for a prolonged period of time (duration of activity), eg, by coating erosion or diffusion of dmg through it. 

The bioflavanoids (vitamin P complex) are substances which maintain the small blood vessel walls. The substances are widely distributed among plants, eg, all citms fmits, and have been used medicinally to decrease capillary permeability and fragility. 

Isoflurane is a respiratory depressant (71). At concentrations which are associated with surgical levels of anesthesia, there is Htde or no depression of myocardial function. In experimental animals, isoflurane is the safest of the oral clinical agents (72). Cardiac output is maintained despite a decrease in stroke volume. This is usually because of an increase in heart rate. The decrease in blood pressure can be used to produce "deHberate hypotension" necessary for some intracranial procedures (73). This agent produces less sensitization of the human heart to epinephrine relative to the other inhaled anesthetics. Isoflurane potentiates the action of neuromuscular blockers and when used alone can produce sufficient muscle relaxation (74). Of all the inhaled agents currently in use, isoflurane is metabolized to the least extent (75). Unlike halothane, isoflurane does not appear to produce Hver injury and unlike methoxyflurane, isoflurane is not associated with renal toxicity. 

Florfenicol concentrations in the brain, cerebrospinal fluid (CSF), and aqueous humor were one-fourth to one-half the corresponding semm concentrations. Concentrations in these tissues and fluids did not decrease as rapidly, maintaining a low, but fairly constant value. Because the brain, CSF, and aqueous humour are separated from the blood by specialized barriers, florfenicol can seemingly only cross these barriers to a limited extent. 

In addition to its internal blood flow operation, the heart has its own system of blood vessels to keep the muscle wall of the heart, the myocardium, supphed with oxygenated blood (Fig. 3a). The coronary arteries, which branch from the aorta to the right and left sides of the heart, are vital to maintaining that supply. The heart is an extraordinary electromechanical muscle that can be trained to increase blood flow to the body sixfold. It can range from 5 to 30 L /min during exertion. 

A broad-based cardiomyoplasty market should emerge by the late 1990s. Successhil development of a small-diameter graft to use in coronary bypass surgery instead of the patient s saphenous vein or mammary artery seems likely to occur by the year 2000. Development of appropriate materials and manufacturing methods are needed to maintain patency without damaging blood in grafts below 4 mm in diameter. 

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