Disseminated arterial calcification and enhanced myogenic response are associated with abcc6 deficiency in a mouse model of pseudoxanthoma elasticum.

OBJECTIVE: Pseudoxanthoma elasticum is an inherited metabolic disorder resulting from ABCC6 gene mutations. It is characterized by progressive calcification and fragmentation of elastic fibers in the skin, retina, and the arterial wall. Despite calcium accumulation in the arteries of patients with pseudoxanthoma elasticum, functional consequences remain unknown. In the present study, we investigated arterial structure and function in Abcc6(-/-) mice, a model of the human disease. APPROACH AND RESULTS: Arterial calcium accumulation was evaluated using alizarin red stain and atomic absorption spectrometry. Expression of genes involved in osteochondrogenic differentiation was measured by polymerase chain reaction. Elastic arterial properties were evaluated by carotid echotracking. Vascular reactivity was evaluated using wire and pressure myography and remodeling using histomorphometry. Arterial calcium accumulation was 1.5- to 2-fold higher in Abcc6(-/-) than in wild-type mice. Calcium accumulated locally leading to punctuate pattern. Old Abcc6(-/-) arteries expressed markers of both osteogenic (Runx2, osteopontin) and chondrogenic lineage (Sox9, type II collagen). Abcc6(-/-) arteries displayed slight increase in arterial stiffness and vasoconstrictor tone in vitro tended to be higher in response to phenylephrine and thromboxane A2. Pressure-induced (myogenic) tone was significantly higher in Abcc6(-/-) arteries than in wild type. Arterial blood pressure was not significantly changed in Abcc6(-/-), despite higher variability. CONCLUSIONS: Scattered arterial calcium depositions are probably a result of osteochondrogenic transdifferentiation of vascular cells. Lower elasticity and increased myogenic tone without major changes in agonist-dependent contraction evidenced in aged Abcc6(-/-) mice suggest a reduced control of local blood flow, which in turn may alter vascular homeostasis in the long term.

Incorporation and distribution of strontium in bone.

The distribution and incorporation of strontium into bone has been examined in rats, monkeys, and humans after oral administration of strontium (either strontium chloride or strontium ranelate). After repeated administration for a sufficient period of time (at least 4 weeks in rats), strontium incorporation into bone reaches a plateau level. This plateau appears to be lower in females than in males due to a difference in the absorption process. Steady-state plasma strontium levels are reached more rapidly than in bones, and within 10 days in the rat. The strontium levels in bone vary according to the anatomical site. However, strontium levels at different skeletal sites are strongly correlated, and the strontium content of the lumbar vertebra may be estimated from iliac crest bone biopsies in monkeys. The strontium levels in bone also vary according to the bone structure and higher amounts of strontium are found in cancellous bone than in cortical bone. Furthermore, at the crystal level, higher concentrations of strontium are observed in newly formed bone than in old bone. After withdrawal of treatment, the bone strontium content rapidly decreases in monkeys. The relatively high clearance rate of strontium from bone can be explained by the mechanisms of its incorporation. Strontium is mainly incorporated by exchange onto the crystal surface. In new bone, only a few strontium atoms may be incorporated into the crystal by ionic substitution of calcium. After treatment withdrawal, strontium exchanged onto the crystal is rapidly eliminated, which leads to a rapid decrease in total bone strontium levels. In summary, incorporation of strontium into bone, mainly by exchange onto the crystal surface, is dependent on the duration of treatment, dose, gender, and skeletal site. Nevertheless, bone strontium content is highly correlated with plasma strontium levels and, in bone, between the different skeletal sites.

Transport measurements across Caco-2 monolayers of different organic and inorganic selenium: influence of sulfur compounds.

The transport and uptake of the most common Se compounds, selenate (SeO42-), selenite (SeO3(2-)), selenomethionine, and selenocystine, were investigated using confluent monolayers of Caco-2 cells, a human carcinoma cell line. Comparative measurements were performed in the absorptive (apical to basolateral side) and exsorptive (basolateral to apical side) directions. Apparent permeability coefficients (Papp), calculated from transport experiments in the absorptive direction, showed increasing values in the following rank order: about 1 x 10(6) cm/s < mannitol < SeO3(2-) < or = selenocystine < selenomethionine < SeO4(2-) < or = about 16 x 10(4) cm/s. The ratios of the Papp measured in the absorptive versus exsorptive directions indicated that only the organic forms presented a net polarized transport (Papp ratio >> 1), suggesting the presence of a transcellular pathway. No significant excretion was observed. The transport of selenomethionine was inhibited by its sulfur analog, methionine, suggesting a common transport mechanism. In contrast, an inhibition of the transport of selenocystine by cysteine was not observed. From the two substrates tested, sulfate and thiosulfate, only thiosulfate inhibited the transport of SeO4(2-) . This effect was also observed for SeO32- (i.e., was unspecific), which questioned the assertion of a common transport for sulfate and SeO4(2-) and may confirm the paracellular pathway of SeO42- suggested by the Papp ratio of about 1. The addition of glutathione (GSH) in large excess had no consequence on the passage of SeO3(2-) but strongly increased the uptake (about fourfold). The liquid chromatography - mass spectrometry (LC-MS) data showed that, in the ionic condition of incubation medium, GSH promptly reduced SeO3(2-) (< or = 2 min) in its elemental form Se0, which cannot ascribe to selenodiglutathione a direct role in the effect of GSH.

Blood cadmium concentration in the population of the Rabat area, Morocco.

Blood cadmium concentrations were determined in 377 adults, 297 men and 80 women, randomly selected from the Rabat Transfusion Center, Morocco. The mean blood cadmium level was 1.1+/-0.7 microg/l, which was higher than in French subjects, with an average of 0.7+/-0.6 microg/l. In Moroccan people, the mean blood cadmium concentration of men, 1.1+/-0.8 microg/l, was significantly higher than that of women, 0.8+/-0.4 microg/l, whereas in the French people tested, there was no statistically significant difference between men and women. In Morocco, employment of men and the smoking habits of men and women were linked to an increase of blood cadmium levels. The significantly higher level observed in men could be due to a higher percentage of men who were smokers and to professional activity leading to increased exposure to cadmium.

Fatal poisoning due to intravasation after oral administration of barium sulfate for contrast radiography.

A fatal poisoning after oral administration of barium sulfate for contrast radiography is reported. Barium sulfate is an insoluble salt and therefore is almost nontoxic. The case described here involves a 61-year-old woman who underwent two CT scans of the digestive tract with oral administration of barium sulfate during a surgical procedure. Within several hours after the first barium swallow examination the patient presented nonspecific neurologic and cardiovascular manifestations that rapidly progressed and led to death a few days later. Laboratory findings demonstrated elevated levels of barium in the blood and cerebrospinal fluid. The most likely mechanism of poisoning was progressive intravasation of barium due to stasis of contrast material related to intestinal obstruction.

[Lead blood levels in children under 6 years of age in the Mans region]. / Etude de l'imprégnation saturnine d'enfants de moins de 6 ans de la région du Mans.

OBJECTIVES: High lead levels in children can have a deleterious effect on intellectual development. We assessed blood lead levels in children in the Le Mans region. METHODS: Children aged between 6 months and 6 years were included in the study. Inclusion criteria were health status requiring a blood sample and amount of blood available after ordered tests sufficient for lead blood analysis. The study group included 365 children. RESULTS: Mean blood level in the 365 children was 37.2 +/- 20.6 micrograms/l. Six of the children had blood levels greater than 100 mu/l. None of the children had a level over 200 micrograms/l. Location of the home or date of construction of the home were not significantly correlated to blood lead levels, however blood lead levels were higher in children with neurological or behavioral disorders. This observation was made in a limited number of children. CONCLUSION: The risk of excessively high blood lead levels in children under 6 years of age is low in the Le Mans region. There is however a risk when old houses are renovated or in children with neurological or behavior disorders.

Strontium distribution and interactions with bone mineral in monkey iliac bone after strontium salt (S 12911) administration.

The analysis of the interaction of strontium (Sr) with bone mineral is of interest because a new agent containing Sr (S 12911) has shown positive effects on bone mass in various animal models of osteoporosis and is currently being developed for preventive and curative treatment of postmenopausal osteoporosis. Iliac bone samples were obtained from 20 male monkeys: 4 untreated control animals, 12 animals sacrificed at the end of a 13-week treatment with high dose levels of S 12911 (750, 275, or 100 mg/kg/day orally), and 4 animals sacrificed 6 weeks after the end of a 13-week treatment with S 12911 (750 or 100 mg/kg/day orally). The distribution of Sr was determined and quantified by X-ray microanalysis. Changes at the crystal level were evaluated by X-ray diffraction and Raman microspectrometry. In the control animals, traces of Sr were found to be homogeneously distributed throughout the bone tissue. In the treated monkeys, Sr could only be detected in calcified matrix. In monkeys sacrificed at the end of the treatment, Sr was found to be dose-dependently incorporated into the mineral substance of the compact and cancellous bone. Sr was heterogeneously distributed with three to four times more Sr in new than in old compact bone, and approximately two and a half times more Sr in new than in old cancellous bone. The bone Sr content dramatically decreased in the animals sacrificed 6 weeks after the end of the treatment. Diffraction showed no significant changes in the characteristics of the crystal lattice. Sr appeared to be easily exchangeable from bone mineral and was slightly linked to mature crystals through ionic substitutions. Even at the highest dose level tested, less than 1 calcium ion out of 10 was substituted by 1 Sr ion in each crystal. In conclusion, taken up by bone, Sr was heterogeneously distributed with a higher concentration in new than in old bone but induced no major modifications of the bone mineral (crystallinity, crystal structure) at the crystal level. As a result, a treatment with S 12911 Sr salt should not induce any alteration of bone mineral.

[Study of blood lead levels in a population of 616 subjects from the regions: Centre and Pays de Loire]. / Etude de la plombémie dans une population de 616 sujets des régions Centre et Pays de Loire.

OBJECTIVES: Low-lead level exposure has been associated with harmful health effects. Blood lead is the most widely used marker of exposure. In this work, our purpose was to evaluate the present level of blood lead in a group of 616 subjects from the general population living in two regions of France: Centre and Pays de Loire. METHODS: Subjects were randomly included in the study. Blood lead was measured by inductively coupled plasma mass spectrometry which is the most sensitive and specific method. RESULTS: The mean blood lead concentration of the population studied ranged from 46.7 +/- 20.5 micrograms/l in the 6-10 year old to 86.6 +/- 42.4 micrograms/l in the 50-66 year old subjects. From 385 children under 13 years old, 5 had blood lead higher than 100 micrograms/l, the maximum acceptable level recommended by the American Centers for Disease Control. Women had lower blood lead values than men and their levels remained unchanged until 50 years but increased beyond this age. CONCLUSION: Mean lead levels were low in this French population. There is however risk of higher levels in persons living in old housing.

Enhancement of bismuth toxicity by l-cysteine.

Bismuth-induced encephalopathies observed in France about twenty years ago have never received convincing explanation. In previous papers we have shown in animal experiments that L-cysteine enhanced Bi absorption without leading to encephalopathies. in this paper we have studied in greater detail the toxicity and the pharmacokinetics of Bi, and L-cysteine, given by intraperitoneal route to mice, singly and simultaneously as a Bi-L-cysteine complex. Bismuth and L-cysteine, were nontoxic singly since their LD50 were higher than 15 mmol/kg, but were toxic (LD50 = 0.3 mmol/kg) when they were given as a complex. The complex was about 50 times more toxic than the separate products. The changes in the levels of Bi and L-cysteine in blood versus time after the injection of the Bi-L-cysteine complex suggests that the complex entered into the blood under a non-dissociated form but just afterwards the complex dissociated and the levels of Bi decreased rapidly whereas the levels of L-cysteine remained high. The concentrations of Bi in tissues, blood, brain, kidney and liver were higher when it was given as the Bi-L-cysteine complex than alone. But the increase of the levels of Bi in tissues induced by L-cysteine was not sufficient to explain the 50 fold increase of the toxicity of the complex in comparison with Bi and L-cysteine given alone. Since the increase of the levels of Bi induced by L-cysteine was not sufficient to explain the increase of the toxicity of the complex, another explanation is required. We suggest that this increase results from the stimulation of peroxidation by bismuth and L-cysteine, as already observed for iron and L-cysteine. Other experiments are needed to verify the validity of this hypothesis.

Evaluation of inductively coupled mass spectrometry for the determination of platinum in plasma.

Among the different analytical methods used for the determination of platinum in blood plasma from patients treated by platinum derivatives, inductively coupled plasma mass spectrometry appears to be the most sensitive (detection limit 0.05 microgram l-1) and the best adapted for measuring low concentrations. The preparation of the samples consisted only of a dilution. The recoveries were close to 100% and both within-run and between-days reproducibility were very good. The determination of free platinum which was only about 5% of total plasma platinum was chosen to illustrate the inductively coupled mass spectrometric method.

Effects of an EDTA infusion on the urinary elimination of several elements in healthy subjects.

Ethylene diamine tetraacetate calcium disodium salt (EDTA Ca Na2), 1 g dissolved in 250 ml of 5% w/v glucose solution, was infused intravenously over 1 h into 10 healthy subjects (eight males and two females). Urines were collected over 24 h, the day before and on the day of the EDTA Ca Na2 infusion test. The elements Al, B, Ba, Cu, Fe, Mn, Si, Sr, Zn, Na, K, Ca, Mg, S and P were measured by inductively coupled plasma optical emission spectrometry. Pb was measured by inductively coupled plasma mass spectrometry. The EDTA Ca Na2 infusion increased the 24 h elimination of Al from 9.8 micrograms to 58 micrograms, of Fe from 66 to 121 micrograms, of Mn from 2.9 to 16.5 micrograms, of Pb from 9.8 to 56 micrograms and of Zn from 623 to 8847 micrograms. The ratio of the increase of urinary elimination induced by EDTA Ca Na2 was about 2 for Fe, 5 for Al, Pb and Mn, and 15 for Zn.

Aluminium determination in the skin of patients with and without end-stage renal failure.

Aluminium (Al) concentration in the skin was determined by inductively coupled plasma optical emission spectrometry to look for a correlation between Al exposure and skin content in patients with end-stage renal failure. Skin Al concentrations were higher in dialyzed patients than in the nondialyzed group (1.02 +/- 0.30 vs. 0.26 +/- 0.10 micrograms/g; p less than 0.001). Moreover, in the dialyzed group, the patients treated for more than 100 months had a higher concentration of Al in the skin than the others (1.20 +/- 0.26 vs. 0.80 +/- 0.18 micrograms/g; p less than 0.05). Al skin content correlated better with the deferoxamine infusion test (DIT) than with Al blood plasma concentration. In conclusion, our data confirm that the DIT is a valuable tool for the evaluation of body Al content.

Urinary elimination of molybdenum by healthy subjects as determined by inductively coupled plasma mass spectrometry.

The concentration of molybdenum was measured by inductively coupled plasma mass spectrometry (ICPMS) in the urines of two groups of healthy people living in two areas of France, Brest and Paris, about 500 km away. The concentration of Mo in the 24-hour urines of 10 healthy subjects from the Brest region was 25 +/- 10 micrograms/l, 38 +/- 20 micrograms/24 h and 21 +/- 9 micrograms/g creatinine. The concentration of Mo in the morning urines of 23 healthy men of the Paris region was 41 +/- 34 micrograms/l and 21 +/- 15 micrograms/g creatinine. Thus the mean elimination of Mo per gram of creatinine was the same in the two groups (21 +/- 9 and 21 +/- 15). Since the three main isotopes of Mo m/z = 95, 96 and 98, corresponding to an abundance percentage of 16, 17 and 24.5, respectively, were simultaneously analyzed in each sample and led to similar results, the ICPMS method seems reliable.

Determination of iodine and bromine in plasma and urine by inductively coupled plasma mass spectrometry.

The simultaneous determination of iodine and bromine in plasma and urine by inductively coupled plasma mass spectrometry, using a Nermag prototype instrument, is described. The sample preparation involves only a 10-fold dilution with a diluent containing europium as an internal standard followed by direct nebulisation in the plasma. The iodine, bromine and europium ions are measured at m/z = 127, 79, and 153, respectively. The sensitivity of the method, with detection limits of 1.6 and 52 micrograms l-1 for iodine and bromine, respectively, is satisfactory for clinical applications. The calibration graphs were linear over the ranges 0-400 micrograms l-1 and 0-40 mg l-1 for iodine and bromine, respectively, which are wide enough for most assays. The recoveries were close to 100% with coefficients of variation of less than 3%. The within-day and between-day reproducibility was about 5%. The concentrations of iodine and bromine in the plasma of 26 healthy individuals were 58 +/- 12 micrograms l-1 and 4.1 +/- 0.9 mg l-1, respectively. The amounts of iodine and bromine eliminated in urine were 94 +/- 97 micrograms per 24 h (range 27-403 micrograms per 24 h) and 3.6 +/- 1.7 mg per 24 h, respectively. These results are in agreement with reported values.

Plasma and urine aluminium concentrations in healthy subjects after administration of sucralfate.

1. Sucralfate (basic sucrose aluminium sulphate), a topical intestinal agent, was administered in suspension or granule form to 25 healthy subjects at a total dose of 4 g day-1 for 21 days. Aluminium in plasma and 24 h urine samples was assayed before, during and after administration of sucralfate by inductively coupled plasma optical emission spectrometry. 2. Sucralfate produced significant increases in plasma and urine aluminium concentrations. On average, plasma aluminium increased from about 2 micrograms 1-1 to more than 5 micrograms 1-1 and 24 h urine aluminium increased from less than 5 micrograms to more than 30 micrograms. Both plasma and urine aluminium concentrations decreased rapidly after sucralfate was stopped. However, urinary aluminium concentrations remained higher than normal 5 and 10 days after discontinuation of sucralfate administration. Moreover subjects receiving sucralfate granules had significantly higher average urinary excretion of aluminium than subjects receiving the suspension. 3. The small but significant increase in plasma and urine aluminium following sucralfate administration in therapeutic doses may reflect intestinal absorption of aluminium. Although such absorption would appear to be moderate in healthy subjects, it is suggested that aluminium-based treatments should be used only intermittently, especially in patients with renal disorders.

Concentration of bone elements in osteoporosis.

In aging and in osteoporosis, decreased bone density is associated with decreased bone mass. However, changes in the bone mineral phase remain a matter for investigation. In particular, it is unknown whether bone mineral loss is directly related to reduction in bone mass or associated with changes in the concentration of mineral elements in mineralized bone tissue. In this study, the cortical bone concentration of elements was determined in biopsies of the ilium from 33 subjects (12 controls and 21 individuals with untreated severe osteoporosis). Calcium and phosphorus concentrations were evaluated in cortical and trabecular bone using energy-dispersive x-ray (EDX) microanalysis and inductively coupled plasma optical emission spectrometry (ICPOES). Bone concentrations of Na, K, Mg, Cu, Zn, Fe, Sr, Al, B, and Si were also determined in cortical bone using ICPOES. Additionally, the concentration of F in cortical bone was measured with a specific ion electrode and the concentration of Pb was determined by atomic absorption spectrometry. In mineralized bone tissue there was no significant age-dependent variation in the concentration of Ca, P, or other elements either in controls or in osteoporotic subjects. Moreover, the concentration of elements in bone tissue did not differ in the two groups. These results suggest that the decrease in bone density in osteoporosis is directly related to evolution of the bone mass, without detectable changes in the concentration of elements in bone.