Elements in muscle measured in vivo and in vitro with X-ray spectrometry

Elevated concentrations of elements and abnormalities of neuromuscular junctions in tongue muscles of Down's syndrome

X-ray spectrometry was used to measure the concentrations of calcium, iron, copper and zinc in tongue muscles from patients with Down's syndrome (DS) undergoing partial glossectomy. Similar measurements on samples from autopsies served as controls. Electron microscopy was used to examine neuromuscular junctions. The calcium and copper were significantly elevated and correlated in DS while the iron and zinc showed little change. The copper increase is probably connected with the known high level of Zn-Cu superoxide dismutase (SOD), coded for by chromosome 21. (In DS there is a trisomy 21). The excess of SOD may interfere with free radicals needed for excitation-contraction coupling and may be instrumental in damaging junctional membranes. The high calcium may result from such membrane damage. It is suggested that neuromuscular junction pathology, either genetic or free radical induced, may cause the tongue weakness in DS.

The procoagulant effect of zinc on fibrin clot formation

The influence of Zn+2 on fibrin clot formation was investigated by measuring its effect on the clotting times of fibrinogen exposed to thrombin. It was observed with either human or bovine thrombin that 0.01-0.1 mM Zn+2 induced significant reductions of clotting times in a concentration-dependent manner. The procoagulant effect of Zn+2 occurred in the presence of Ca+2 but was inhibited by metal chelating agents. Higher levels of Zn+2 (greater than 0.2 mM final concentration) were required to accelerate thrombin-induced clot formation in the presence of citrate or oxalate. Similarly with oxalated human plasma, greater than 0.2 mM Zn+2 decreased the clotting time. Cations such as Mg+2 and Mn+2 caused little change in clotting times. As an extension of these findings, we examined the effect of Zn+2 on the inhibition of thrombin by antithrombin-III (AT-III). The presence of as little as 0.006 mM Zn+2 in an incubating mixture of thrombin and AT-III severely reduced the inhibitory activity of AT-III towards thrombin. It was observed that the relative intrinsic fluorescence emission of human thrombin decreased upon exposure to Zn+2 but was unaffected by Mg+2 or Mn+2. It is suggested that Zn+2 can form a complex with thrombin, which results in altered reactivity towards fibrinogen and decreased inhibition by AT-III.

Correlation of erythrocyte and plasma levels of zinc, copper, and iron with evidence of metastatic spread in cancer patients

The level of plasma copper (Cu-Pl) and zinc (Zn-Pl) and the level of erythrocyte iron (Fe-RBC), copper (Cu-RBC), and zinc (Zn-RBC) were determined in the blood of 70 normal donors and 138 patients with various solid tumors by diagnostic x-ray spectrometry (DXS), a technique based on x-ray fluorescence spectrometry analysis. There were no significant changes in the mean values of Zn-Pl, Fe-RBC, and Cu-RBC in the patients when compared with those of normal donors. The mean level of Cu-Pl in the normal donors was 1.34 +/- 0.37 micrograms/ml; it was significantly increased in the patients, ranging between 1.47 +/- 0.34 micrograms/ml for patients without evidence of active cancer (NED) and 1.91 +/- 0.76 micrograms/ml for patients with hepatic metastases. The most significant change observed was an increase in the Zn-RBC found in the patients with clinical evidence of metastatic spread. Whereas the Zn-RBC level in the normal donors was 9.85 +/- 1.47 micrograms/g wet weight, and not significantly elevated in the NED patients, it was elevated to values of 11.37 +/- 1.55 micrograms/g (P less than 0.004) for patients with soft tissue and hepatic metastases and was 12.34 +/- 1.65 micrograms/g (P less than 0.001) for patients with bone metastases. The data suggest a clear correlation between Zn-RBC and metastatic spread in nonlymphomatous human cancer.

Element analysis of skeletal muscle in Duchenne muscular dystrophy using x-ray fluorescence spectrometry

Concentrations of calcium, iron, copper, and zinc were simultaneously measured by x-ray fluorescence spectrometry in muscle biopsies from 11 normal subjects, 13 patients with Duchenne muscular dystrophy (DMD), and 3 DMD carriers. Calcium and copper levels were significantly elevated in patients with DMD compared to controls, and one presumptive carrier also showed an elevated calcium concentration. Comparisons with morphological data for the same samples showed a significant positive correlation between calcium concentration and the percentage area of type 2 fibers in controls, but no other correlations were found to be significant. These results illustrate the value of x-ray fluorescence spectrometry and provide further evidence for the involvement of calcium in dystrophic processes.

Microanalysis and X-ray fluorescence spectrometry of platelets in diseases with elevated muscle calcium

Electron microscopic X-ray microanalysis and X-ray fluorescence spectrometry were done on platelets from patients with Duchenne muscular dystrophy and idiopathic scoliosis (both these conditions are known to be associated with increased intramyofibre calcium). A significant increase in calcium and phosphorus concentrations was found in the dense granules and whole cells of both conditions. The findings suggest that idiopathic scoliosis like Duchenne muscular dystrophy is a multisystem disease with detectable changes in platelets.