Analytical approaches for biomedical elemental analysis

Articulating spacers used in two-stage revision of infected hip and knee prostheses abrade with time

BACKGROUND

Articulating spacers used in two-stage revision surgery of infected prostheses have the potential to abrade and subsequently induce third-body wear of the new prosthesis.

QUESTIONS/PURPOSES

We asked whether particulate material abraded from spacers could be detected in the synovial membrane 6 weeks after implantation when the spacers were removed for the second stage of the revision.

PATIENTS AND METHODS

Sixteen hip spacers (cemented prosthesis stem articulating with a cement cup) and four knee spacers (customized mobile cement spacers) were explanted 6 weeks after implantation and the synovial membranes were removed at the same time. The membranes were examined by xray fluorescence spectroscopy, xray diffraction for the presence of abraded particles originating from the spacer material, and analyzed in a semiquantitative manner by inductively coupled plasma mass spectrometry. Histologic analyses also were performed.

RESULTS

We found zirconium dioxide in substantial amounts in all samples, and in the specimens of the hip synovial lining, we detected particles that originated from the metal heads of the spacers. Histologically, zirconium oxide particles were seen in the synovial membrane of every spacer and bone cement particles in one knee and two hip spacers.

CONCLUSIONS

The observations suggest cement spacers do abrade within 6 weeks. Given the presence of abrasion debris, we recommend total synovectomy and extensive lavage during the second-stage reimplantation surgery to minimize the number of abraded particles and any retained bacteria.

Gene expression profiling in chronic copper overload reveals upregulation ofPrnpandApp

The level at which copper becomes toxic is not clear. Several studies have indicated that copper causes oxidative stress; however, most have tested very high levels of copper exposure. We currently have only a limited understanding of the protective systems that operate in cells chronically exposed to copper. Additionally, the limits of homeostatic regulation are not known, making it difficult to define the milder effects of copper excess. Furthermore, a robust assay to facilitate the diagnosis of copper excess and to distinguish mild, moderate, and severe copper overload is needed. To address these issues, we have investigated the effects on steady-state gene expression of chronic copper overload in a cell culture model system using cDNA microarrays. For this study we utilized cells from genetic models of copper overload: fibroblast cells from two mouse mutants, C57BL/6- Atp7aMobrand C57BL/6- Atp7aModap. These cell lines accumulate copper to abnormally high levels in normal culture media due to a defect in copper export from the cell. We identified 12 differentially expressed genes in common using our outlier identification methods. Surprisingly, our results show no evidence of oxidative stress in the copper-loaded cells. In addition, candidate components perhaps responsible for a copper-specific homeostatic response are identified. The genes that encode for the prion protein and the amyloid-β precursor protein, two known copper-binding proteins, are upregulated in both cell lines.

Determination of the spatial distribution of major elements in the rat brain with X-ray fluorescence analysis

An energy dispersive X-ray fluorescence analysis was applied for determining the spatial (two-dimensional) distribution of elemental concentrations in rat brain sections. Freeze-dried brain sections prepared from normal and ischemic rats with middle cerebral artery occlusion were scanned with a collimated X-ray beam (0.18 mm in diameter, 50-kV acceleration voltage). The fluorescent Kalpha X-rays of P, S, Cl, and K were detectable, so that the two-dimensional distribution of fluorescent X-ray intensities could be determined for these elements. Furthermore, quantitative determination was possible for P and K by using the fundamental parameter technique. However, the accurate determination of Na and Ca was difficult, because of the low energy of Kalpha X-ray of Na, and the interference of K-Kbeta with Ca-Kalpha. The change in elemental concentrations in ischemic tissue, including the decrease in K concentration and increase in Cl concentration, was demonstrated by this method as a two-dimensional contour map. Since it is possible to obtain a pictorial representation of the elemental concentration in tissue sections, this method may be useful to evaluate the ionic changes in injured brain tissue in relation to histological or autoradiographical observations.

Influence of protein calorie malnutrition and fasting on the activities of delta-aminolevulinic acid dehydratase and porphobilinogen deaminase in rats

Rats were fed a restricted standard diet (6-8 g daily) for 4 weeks. The erythrocyte activity of delta-aminolevulinic acid dehydratase showed a very expressed decrease (7.9 times) and its hepatic activity diminished more than twice. Porphobilinogen deaminase activity was reduced by 40% and 17% respectively. After a 3-day total food deprivation delta-aminolevulinic acid dehydratase activity remained unchanged in red blood cells, but an increase by 52% was found in the liver. The erythrocyte activity of porphobilinogen deaminase was reduced by 42% and its hepatic activity--by 16%.

Mg2+ administered up to twenty-four hours following reperfusion prevents ischemic damage of the Ca1 neurons in the rat hippocampus

Inductively coupled plasma emission spectrometry analysis was applied to determine ischemia-induced changes of Mg2+ and Ca2+ in vulnerable regions of rat brain. This method can provide an accurate quantification and lower detection limits, as compared to atomic absorption spectrophotometry or several other methods. In the hippocampus, Mg2+ content significantly increases 24 h following 20 min of ischemia, followed by a gradual decrease between 48 and 72 h. Ca2+ accumulation was found at 48 and 72 h. At the cell membrane, Mg2+ plays a role as an endogenous calcium channel blocker of both the receptor-operated and voltage-dependent gates and, in the mitochondria, Mg2+ inhibits Ca2+ uptake processes. We propose that the mobilization of Mg2+ after 24 h reperfusion may counteract the process of ischemia-induced neuronal damage and that decreases of Mg2+ may be correlated with the degree of brain injury. However, in the natural concentration of Mg2+, the counteraction may not be sufficient for a neuroprotective effect. Therefore, after 24 h reperfusion, an artificial enhancement of Mg2+ is necessary for neuroprotection. In order to test the above hypothesis, MgCl2, (50 mM) was administered directly to the CA1 sector of the rat hippocampus before and at various intervals following 20 min of ischemia. Pyramidal cells were evaluated seven days later and neuronal density was determined. Consistent with the hypothesis, a neuroprotective effect was observed, even when MgCl2 was administered 24 h, but not 48 h, after the ischemic episode.

DC plasma emission spectroscopic analysis of pancreatic calculi

Previous studies on pancreatic calculi (PC) from alcoholic pancreatitis and our recent studies on calculi from tropical pancreatitis have shown them to consist mainly of CaCO3 with minute quantities of Mg. However, no attempt was made to look for other elements in PC. This is because of the difficulty in obtaining adequate samples of PC, coupled with the technical limitations in analyzing multi-elements from small samples. In this study, our aim was to analyze the major, minor and trace elements of PC from different parts of the world. DC plasma emission spectroscopy, a modern method that permits determination of multiple elements from small samples, was used in elemental analysis. We identified 17 elements in addition to calcium. Selenium was looked for but was absent. It was interesting that the elemental composition of PC in four patients from different geographical areas with divergent etiological factors remained the same. Absence of Se is of interest, as Se deficiency is associated with pancreatic fibrosis in experimental animals and it is often noted in chronic alcoholics and the malnourished. This preliminary study emphasizes the need for analysis of the elemental composition of pancreatic juice in normals and in conditions predisposing to chronic pancreatitis, to understand lithogenesis and possibly also the etiology of, at least, some types of pancreatitis.