Chromium circulation

There appears to be a chromium pool in individuals who are not chromium deficient (136). When there is an increase in level of cHculating insulin in response to a glucose load, an increase in circulating chromium occurs over a period of 0.5—2 h. This is foUowed by a decline and excretion of chromium in urine increases. Chromium deficiency is indicated when no increase or a small increase in blood chromium level or urine chromium occurs. 

Purely gaseous method Articles are suitably jigged inside a retort chamber and vapours of chromium halide, usually diluted with a reducing gas, are circulated. The temperature is maintained within the range 950-1 200°C for chromising of iron and ferrous alloys (recent Russian work on... 

Semi-gaseous method The articles, surrounded by a solid compound containing chromium metal, are packed in a retort chamber, and vapours of chromium halide or halogen compound are circulated in the chamber, which is maintained at 950-1 200 C. 

Elevated levels of chromium in blood, serum, urine, and other tissues and organs have been observed in patients with cobalt-chromium knee and hip arthroplasts (Michel et al. 1987 Sunderman et al. 1989). Whether corrosion or wear of the implant can release chromium (or other metal components) into the systemic circulation depends on the nature of the device. In one study, the mean postoperative blood and urine levels of chromium of nine patients with total hip replacements made from a cast cobalt-chromium-molybdenum alloy were 3.9 and 6.2 pg/F, respectively, compared with preoperative blood and urine levels of 1.4 and 0.4 pg/F, respectively. High blood and urinary levels of chromium persisted when measured at intervals over a year or more after surgery. These data suggest significant wear or corrosion... 

Transferrin is mainly synthesized in the hepatocytes. There are about 20 known variants. Iron is transported by transferrin (approx. 30% of transferrin is saturated with iron). With the help of a membrane receptor, the iron-transferrin complex is taken up and released in the liver cell, where it is immediately bound (because of its toxicity) to ferritin. The liver cells take up iron predominantly from transferrin, to a lesser degree also from haptoglobin, haemopexin, lactoferrin and circulating ferrin. Transferrin, which is mainly formed in the hepatocytes, may also bind and transport, in decreasing order, chromium, copper, manganese, cobalt, cadmium, zinc and nickel. The half-life of transferrin is 1 - 2 hours, which is very short in view of its total blood concentration of 3-4 mg. Approximately 0.4 g ferritin iron is stored in the liver. In the case of transferrin deficiency, its bacteriostatic and fungistatic effects are also reduced. Transferrin without iron saturation is known as apo-transferrin. (31, 66, 67)... 

To improve the corrosion resistance of the stainless steel components, particularly in the weld-affected areas, it is a common practice to passivate the product contact surfaces of installed piping and equipment by circulating a solution of strong oxidant such as nitric or citric acid, or a chelating agent. Passivation removes free iron from the metal surface and creates a thin protective layer of chromium oxide. It is not uncommon to repeat the passivation treatment periodically (every few years) to restore the passive layer. 

A method for predicting the safety of transfusion is based on the use of cells labeled with radioactive chromium (74). After the administration of several milliliters of the labeled blood, the survival of erythrocytes in the recipient s circulation is examined poor survival in vivo indicates that transfusion with these erythrocytes will be hazardous (75,76). There are two types of survival curve for incompatible erythrocytes. A curve described by a single exponential function is seen with most potent IgG antibodies that do not bind complement, including anti-D, anti-C, and anti-K, antibodies. Clearance described by more than one exponential is observed with complement-binding antibodies (77). In the latter there is a slowing of erythrocyte destruction 5-20 minutes after injection... 

The VR-75 RRIM machine made by Accuratio Systems, Inc. (ASI) was used in this study, and a chromium polished steel mold (220 x 293 x 3 mm) with an aftermixer section was also used. It was equipped with cores for hot water circulation and was controlled at 60°C-70°C. The clamping force was supplied by a simple air bag press. The resin used consisted of a polyurea dispersion in a blend of... 

A beneficial response of glucose-intolerant patients to chromium supplementation is presently the only means of confirming chromium deficiency. No practicable method of assessing intracellular chromium depletion is yet available and there is no consistently reliable animal model for chromium deficiency. Furthermore, it has been known from early animal experiments that circulating chromium is not in equihbrium with physiologically important reserves. It has been shown in late pregnancy that serum chromium concentration does not correlate with glucose intolerance, insuhn resistance, or serum hpids. ... 

In Chapter 3.4 a method has been presented for long-term prognosis of metal pollutant mobility, which combines column circulation leaching experiments at variable pH/E -conditions with sequential extraction procedures on the solid waste material before and after these experiments (Schoer FSrstner, 1987). Temporal release patterns are different for the individual elements (Figure 6-5) While at pH 5/400 mV release of cadmium seems to be completed within the experimental period mobilization of copper is still going on and the end point cannot be estimated from the data of the "kinetic" experiments. The same effect has been found for the examples of thallium and vanadium. For the other elements, the endpoint of release can be determined as approximately 10 mg cobalt, 0.6 mg cadmium, 600 mg zinc and 0.3 mg chromium, 2 mg barium and 20 mg lead (per 100 g of solid substrate treated with 140 L solu-... 

Resistance heating usually involves the highest electricity costs, and may require circulating fans to assure the temperature uniformity achievable by the flow motion of the products of combustion (poc) in a fuel-fired furnace. Silicon control rectifiers have made input modulation more economical with resistance heating. Various materials are used for electric furnace resistors. Most are of a nickel-chromium alloy, in the form of rolled strip or wire, or of cast zig-zag grids (mostly for convection). Other... 

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