Effects of sodium and magnesium sulfate in drinking water on mallard ducklings

One-day-old mallard (Anas platyrhynchos) ducklings were given drinking water for up to 28 days that contained concentrations of sodium and/or magnesium similar to those found in saline wetlands. Growth, tissue development, and biochemical characteristics of these ducklings were compared to those reared on fresh water. Much of the ingested salt was excreted by passage of voluminous fluid excreta. This effect occurred in birds given water with as little as 500 ppm Mg or 1,000 ppm Na. The supraorbital salt gland was active within 4 days in ducklings drinking water containing greater than or equal to 1,500 ppm of Na. Feather growth was decreased in ducklings drinking water with greater than or equal to 1,500 ppm of either Na or Mg. Ducklings drinking water with 3,000 ppm of either ion, or 1,500 ppm of each, grew more slowly than control birds. Ducklings drinking water with 3,000 ppm of either Na or Mg had reduced thymus size and bone breaking strength. Those drinking water with 3,000 ppm of Mg, or 3,100 ppm Na and 1,300 ppm Mg also had less trabecular bone and enlarged adrenals. Birds drinking the latter water had an elevated concentration of Na and calcium, and a decreased concentration of phosphorus and chloride in their serum, and elevated plasma protein levels. Ducklings reared on fresh or slightly saline water adapted very poorly to an abrupt change to more saline water (specific conductivity = 15,250 microns hos/cm) at 14 days of age. These birds stopped eating, became inactive and some died within 3 days; survivors had many tissue and biochemical abnormalities at 20 days of age. The level of salinity in these trials was similar to that in "brackish" or "moderately saline" wetlands and lower than that previously found to have effects on growth and feathering of ducklings. Many of the sublethal effects were subtle and non-specific manifestations of stress, and would be difficult to detect in wild ducklings on saline wetlands.     

Serum electrolytes and skeletal mineralization in hard- and soft-water areas

Serum levels of calcium and magnesium were measured in two Ontario cities that differ widely in the hardness of their local water-supply. The hypothesis being tested was that residents of the city with the hard water-supply (and a low cardiovascular death-rate) would show relatively high serum levels of calcium and/or magnesium. In addition, a comparison was made of the cortical thickness of the second metacarpal bone in the two areas to see if there was any evidence of increased skeletal mineralization in the hard-water area. The results obtained did not support either of these hypotheses, but it is suggested that the failure to demonstrate differences in body-levels of calcium or magnesium may not be incompatible with one (or both) of these water-borne elements functioning as the “water-factor” in cardiovascular disease.     

Multiple choice.

It is possible that there is a systematic geographical variation in the proportion of deaths from ischemic heart disease that occur suddenly, and that this variation may be causally related to water hardness or some other environmental factor. Three indices of sudden death have been examined; each showed a correlation with water hardness that was of similar sign and magnitude. A detailed examination of 1686 deaths occurring in residents of two cities which differ widely in the hardness of their water supply confirmed that in deaths ascribed to heart disease the proportion of sudden deaths was higher (by 20-30%) in the northern (soft-water) city than in the southern (hard-water) city.     

Selective stimulation by tri-iodothyronine of myocardial deoxyribonucleic acid polymerase-α in neonatal rats

Three forms of DNA polymerase (alpha, beta and gamma) were separated from isolated rat myocardial cells on the basis of template, pH and ionic requirements, sensitivity to N-ethylmaleimide and position on sucrose gradients. Tri-iodothyronine administration (20mug/100g intraperitoneally) to 3-week-old rats resulted in selective stimulation of DNA polymerase-alpha (198+/-7.1 versus 102+/-5.8pmol of [(3)H]dTMP/30min per mg of protein in untreated controls, P<0.01), with no change in polymerases-beta and -gamma. [(3)H]Thymidine incorporation into myocardial DNA was also enhanced in tri-iodothyronine-treated neonatal rats (132+/-11.2 versus 53+/-4.1c.p.m./mug of DNA in controls, P<0.001). Increased incorporation was associated with an expansion of deoxyribonucleoside 5'-triphosphate pools, especially that of dTTP (24+/-1.6 versus 10+/-1.1pmol/mg of DNA, P<0.01). Neither DNA polymerase activities nor [(3)H]thymidine incorporation were changed in 6-month-old rats in response to tri-iodothyronine. Unstimulated adult myocardial cells had DNA polymerase activities comparable with those in 3-week-old animals, but significantly lower [(3)H]-thymidine incorporation and deoxyribonucleoside triphosphate concentrations. Enhancement of both DNA polymerase-alpha activity and [(3)H]thymidine incorporation in tri-iodothyronine-treated young rats was prevented by concomitant administration of either vinblastine (1mug/g) or daunomycin (2mug/g); actinomycin D (0.1mug/g) or cycloheximide (8mug/g), on the other hand, prevented the increase in [(3)H]thymidine incorporation, but not DNA polymerase-alpha activation. These results demonstrate an age-dependent stimulation of myocardial DNA replication by tri-iodothyronine and suggest an inter-relationship between DNA synthesis and subsequent entry into mitosis.     

Thyroid activity of spontaneous hypertensive rats.

Thyroid activity of both male and female spontaneous hypertensive (SH) rats was studied by measurements of uptake and rate of release of 131-I, urinary excretion of 131-I, and thyroxine secretion rate (TSR). In addition, thyroid glands were removed at death and weighed. Radioactivity of the thyroid gland of male rats measured at intervals after administration of 131-I revealed a significantly reduced maximal uptake at 21.5 hr after injection and a reduced rate of release. The mean biological half-life of 131-I for the control group was 37.8 plus or minus 3.1 (SE) hr compared to 54.8 plus or minus 7.2 hr for hypertensives (P less than 0.05). Similar results were observed for females in that biological half-life of 131-I was 32.2 plus or minus 1.2 hr compared with 84.1 plus or minus 4.1 hr for hypertensives (P less than 0.01). Urinary excretion of 131-I by hypertensive rats at 24, 48, and 72hr after injection of 131-I did not differ from control in either experiment. Thyroid weight at autopsy was increased significantly above that of normotensive controls. TSR was measured indirectly in a third group of male spontaneously hypertensive and normotensive rats. TSR of control rats was estimated to be 0.97 mug T4/100 g body wt/day and 1.35 mug T4/100 g body wt/day for SH RATS. The results are consistent with the suggestion that the method for measurement of TSR in hypertensive rats gives an artifactually high value because TSH secretion is elevated.     

The effect of difluorodichloromethane (FC 12) on isolated rat and rabbit heart]

We have tried to determine if dichlorodifluoromethane (F.C. 12) might have an effect in vitro on the isolated rat and rabbit hearts. The direct action of F.C. 12 on the heart in vitro is similar in both rats and rabbits. It occurs at doses such as 20 +/- 10 mug/ml (rat) and 35 +/- 5 mug/ml (rabbit). F.C. 12 depresses the strength of the myocardial contractions; the effect is reversible at low concentration (less than 60 mug/ml) but irreversible at high concentration (greater than or equal to 120 mug/ml). It also causes a slight bradycardia, but no significant effect on the basal tonus. At high concentration, F.C. 12 may produce arrhythmia : this action occurs more readily in the rat heart than in the rabbit heart.     

Glycolipids of the fish testis.

Glycolipids were purified from the total lipid extract of the testis or milt of a kind of puffer (Fugu rubripes rubripes) by adsorption column chromatography using silicic acid and magnesium silicate and by preparative silica gel TLC. The glycolipids were identified as glucosylceramide (116 mug/g wet tissue) and galactosylceramide 26.7 mug/g). Seminolipid, a sulfagalactolipid specific to mammalian testis was not detected, but the presence of a small amount of sulfatide (15.2 mug/g) was demonstrated. The long-chain bases of both cerebrosides were mainly C18-sphingenine, but in sulfatide, C20-sphingenine was more abundant than C18-sphingenine. In both cerebrosides and sulfatide, the fatty acid compositions were similar, with nervonic acid as the predominant component. Two species of gangliosides were also obtained and were identified as N-acetylgalactosaminyl(1 leads to 4)[N-acetylneuraminyl(2 leads to 3)]galactosyl(1leads to 4)glucosylceramide (59.8 mug/g) and N-acetylneuraminyl(2 leads to 3)galactosyl(1 leads to 4)N-acetylglucosaminyl(1 leads to 3)galactosyl(1 leads to 4)glucosylceramide (45.0 mug/g). The long-chain bases of the two gangliosides consisted of C18-spingenine and C20-sphingenine, and the major fatty acids were palmitic and stearic acids.     

Low level environmental lead exposure--a continuing challenge

The current threshold for lead toxicity, defined as a blood lead level of 10 mug/dL, was adopted by the United States (US) Centers for Disease Control and Prevention (CDC) in 1991 and the World Health Organization in 1995. Since that time, adverse health outcomes at blood lead levels below this threshold have been well demonstrated. Most concern probably relates to children of pre-school age; an international pooled analysis has demonstrated lead-associated intellectual deficits at blood lead levels well below 10 mug/dL. In the case of adults, several convincing population studies have shown a positive association between blood lead and risk of death. The largest such study compared mortality information from participants with blood lead levels in the highest third of the blood lead distribution (3.6 mug/dL or greater) with those in the lowest third (less than 1.9 mug/dL). After adjustment for potential confounders, estimates of the excess risk were 25% for all cause mortality and 55% for cardiovascular mortality. The adverse consequences of lead exposure have no discernible blood lead threshold, implying there is no safety margin at existing exposure levels. Despite marked declines in population mean blood lead levels since 1980, low level environmental lead exposure remains a significant public health concern.     

Characterization of two lipoproteins containing apolipoproteins B and E from lesion-free human aortic intima

Lesion-free areas of aortic intimas from seven men, 30 to 49 years old, were extracted with aqueous buffer within a few hours after an accidental or sudden death. Two lipoprotein fractions could be isolated by density gradient ultracentrifugation from all cases. The mean composition of fraction I (d less than 1.012 g/ml) resembled that reported for the cholesteryl ester-rich, beta-migrating very low density lipoprotein (beta-VLDL); the composition of fraction II (d 1.021-1.046 g/ml) resembled that of plasma low density lipoprotein (LDL). Mean diameter of the particles was 35 +/- 8 nm in fraction I and 25 +/- 5 nm in fraction II (22 +/- 2 nm in plasma LDL). Both fractions contained apolipoproteins B (apoB) and E (apoE), and had increased electrophoretic mobilities and reduced contents of linoleic acid. The immunoreactivity of apoB to a polyclonal and two monoclonal antibodies in both fractions was not different from that of plasma lipoproteins. The apoE isoform patterns in both fractions were similar to those obtained from the respective postmortem plasmas. When incubated with mouse peritoneal macrophages, fractions I and II enhanced the incorporation of radioactive oleate into cholesteryl esters by 10- to 20-fold and 3- to 4-fold, respectively, in comparison to plasma LDL. In conclusion, our results indicate that lesion-free human aortic intima contains two types of apoB- and apoE-containing lipoprotein particles, both of which might be potentially atherogenic.     

Pattern of cardiac fibrosis in rabbits periodically fed a magnesium-restricted diet and administered rare earth chloride through drinking water

It has been postulated that causation of the tropical cardiomyopathy endomyocardial fibrosis (EMF) is linked to magnesium (Mg) deficiency and cardiac toxicity of the rare earth element cerium (Ce). The aim of the present study was to define the myocardial lesions in rabbits that were fed on Mg-restricted diet (70–80 ppm) periodically and were provided drinking water contaminated with rare earth chloride (1 g/L). Forty New Zealand white rabbits were divided into four groups following a 2 × 2 factorial design. Two groups were periodically fed on Mg-restricted diet with one of them receiving water contaminated with rare earth chloride. The other two groups were continuously fed on Mgsufficient diet (350–400 ppm) with one of them receiving water contaminated with rare earth chloride. All animals were sacrificed at the end of 6 mo. Cardiac tissues were subjected to histology, elemental analysis (calcium [Ca], Mg, and Ce) and estimation of collagen content and collagen phenotypes. Histological lesions were compared with those of EMF in humans and those of acute Mg deficiency in animals. The results suggest that in rabbits, recurrent episodes of Mg deficiency lead to myocardial fibrosis similar to the pattern observed in human EMF.     

含血停搏液镁离子浓度对未成熟心肌保护的影响

目的 采用幼兔离体心脏模型。模拟临床上可能出现的含血停搏液Ca^2 浓度变化,探讨适宜于未成熟心肌保护的Mg^2 浓度。方法 3-4周龄长耳白兔,依照含血停搏液不同Mg^2 浓度（0.6mmol/L,4.0mmol/L,8.0mmol/L,120mmol/L,16.0mmol/L）随机分为5组,建立Langendorff离体心脏灌注模型。采用Ca^2 浓度1.2-1.5mmol/L的含血停搏液,运用温血停搏液诱导停搏,冷血停搏液间断灌注,低温保护,终末温血停搏液控制性再灌注技术,观察以下指标：1、血流动力学指标;实验前后恢复率;心率,主动脉流量,冠脉流量,心排量,左室收缩压和左室舒张末压;2、心肌含水量;3、冠脉流出液乳酸盐含量;4、心肌肌酸激酶和乳酸脱氢酶漏出率;5、心肌细胞内Na^2 ,Ca^2 含量;6、心肌组织ATP含量;7、心肌组织SOD活性,MDA含量;8、心肌超微结构。结果 1、心率恢复率,主动脉流量恢复率及左室收缩压恢复率组间总体差异无显著性。而冠脉流量恢复率,心排量恢复率和左室舒张末压恢复率以Mg^2 浓度8.0mmol/L和12.0mmol/L为优,0.4mmol/L组最差。2、心肌含水量以Mg^2 浓度8.0mmol/L和12.0mmol/L为最低。3、冠脉流出液乳酸盐含量0.4mmol/L组,8.0mmol/L和12.0mmol/L组高于欺科2组。4、心肌乳本能部氢酶漏出率以8.0mmol/L组最低,而肌酸激酶漏出率以8.0mmol/L和12.0mmol/L组为最低。5、心肌细胞内Na^ 、Ca^2 含量;6、心肌组织ATP含量;7、心肌组织SOD活性,MDA含量;8、心肌超微结构。结果：1、心率恢复率,主动脉流量恢复率及左室收缩压恢复率组间总体差异无显著性。而冠脉流量恢复率,心排量恢复率和左室舒张末压恢复率以Mg^2 浓度8.0mmol/L和12.0mmol/L为优,0.4mmol/L组最差。2、心肌含水量以Mg^2 浓度8.0mmol/L和12.0mmol/L为最低。3、冠脉流出液乳酸盐含量0.4mmol/L组最差。2、心肌含水量以Mg^2 浓度8.0mmol/L和12.0mmol/L为最低。3、冠脉流出液乳桎卤含量0.4mmol/L组,8.0mmol/L和12.0mmol/L组高于其余2组。4、心肌乳酸脱氢酶漏出率以8.0mmol/L组最低,而肌酸激酶漏出率以8.0mmol/L和12.0mmol/L组为最低。5、心肌细胞内Na^2 含量以8.0mmol/L和12.0mmol/L组为最低,而心肌细胞内Ca^2 含量以8.0mmol/L组最低。6、心肌组织ATP含量以12.0mmol/L组为最高。7、心肌组织SOD活性以8.0mmol/L和12.0mmol/L组库最高,而MDA含量各组间总体差异无显著性。8、心肌超微结构;8.0mmol/L和12.0mmol/L组表现为基本正常未成熟心肌超微结构,而0.4mmol/L组超微结构有明显损伤表现。结论 对于未成熟心肌,当采用温血停搏液诱导停搏,冷血停搏液间断灌注,低温保护,温血停搏液终末控制性再灌注技术时,为避免含血停搏液Ca^2 浓度偏高对未成熟心肌的不利影响。应维持含血停搏液中Mg^2 浓度在8-12mmol/L。     

Effects of Cadmium on Aquatic Hyphomycetes

Two kinds of experiments, sporulation and growth experiments, were carried out to demonstrate the effect of cadmium on aquatic hyphomycetes. Oak (Quercus petraea L.) leaves were exposed in a hard-water stream (Lüssel, Swiss Jura) and a soft-water stream (Ibach, Black Forest) for 2 months. In the laboratory, fungal sporulation on the leaves in stream water enriched with cadmium (as CdCl₂) was studied. A measurable effect was found when the cadmium concentration exceeded 0.1 ppm (0.1 mg/liter). Concentrations higher than 100 ppm inhibited conidium production completely. This toxic effect of cadmium was species dependent and much higher in soft water (water with low concentrations of calcium and magnesium) than in hard water. Growth experiments with Alatospora acuminata Ingold, Clavariopsis aquatica De Wildeman, Flagellospora curvula Ingold, Heliscus lugdunensis Saccardo and Therry, and Tetracladium marchalianum De Wildeman showed the same pattern of cadmium sensitivity as that seen in the sporulation experiments. Mycelial growth was less sensitive to cadmium than was fungal sporulation. High concentrations of competing cations (e.g., calcium and zinc) or potential ligands could reduce cadmium toxicity. Calcium content seems to be the most important factor responsible for the different sensitivity of aquatic hyphomycetes in hard and soft water.     

Role of exercise testing early after myocardial infarction in identifying candidates for coronary surgery.

It has been suggested that ST depression in lead V5 or equivalent on early exercise testing after acute myocardial infarction predicts a high risk of death. To evaluate exercise testing and radionuclide ventriculography in this context 103 consecutive patients with myocardial infarction who were able to undertake a limited exercise test before discharge from hospital were exercised and underwent gated blood pool scanning. No serious complications resulted from exercise testing. Twenty nine patients developed ST depression in lead V5, 19 had exertional hypotension, 31 developed a heart rate of greater than or equal to 130 beats/min, and 15 had complex ventricular arrhythmias. Death during the first year after discharge from hospital was associated with exertional hypotension (p less than 0.001) and a heart rate on exercise testing of greater than or equal to 130 beats/min (p less than 0.05); these two variables identified all nine deaths. Inability to complete the exercise protocol for any reason was also predictive of death (p less than 0.01). Ventricular arrhythmias and ST depression in lead V5 induced by exercise were not significantly associated with an increased risk of death. The mean (SD) radionuclide ejection fraction in the patients who died was 29 (16%) compared with 43 (11)% in the patients who survived (p less than 0.001). ST changes on exercise testing after myocardial infarction appear to be less predictive of later complications than haemodynamic signs, which may indicate left ventricular damage rather than ischaemia.     

Survey of strontium in mineral waters sold in Japan

The concentrations of strontium, calcium, and magnesium in 33 brands of natural mineral waters commercially available in Japan were determined by inductively coupled plasma-atomic emission spectrometry. The geometric mean values were 94.4 microg/L for strontium, 19.1 mg/L for calcium, and 2.82 mg/L for magnesium. Wide confidence intervals of 1.96-4539 microg/L for strontium, 0.865-421 mg/L for calcium, and 0.064-123 mg/L for magnesium were observed. The significant linear relationships among the three elements over a wide distribution range suggest that the synchronized variations of these elements are regulated by the natural ecosystem and not from accidental contamination from human activities or exceptionally high natural sources. Using the results of multiple linear regression analysis, the strontium concentration can be predicted by that of calcium with the appropriate power function. The results of this study suggest that mineral water can be an important nutritional source of strontium. As trace elements imbalance is often found in older patients with chronic renal failure, we propose that close attention of trace elements intake from trendy foods or beverages is necessary to prevent this hidden problem of a rapidly aging society.     

Post mortem detection of early myocardial infarction by determination of the tissue K+/Na+ ratio

The K+/Na+ ratio was determined in myocardial specimens obtained post mortem from a total of 90 patients. The ratio was 1.0 or higher 25 cases in which there was firm evidence against myocardial infarction, and 0.7, or less in 30 cases with grossly visible signs of myocardial narcosis. The remaining 35 cases were suspect of myocardial infarction on the grounds of either clinical observation or sudden death, without gross change. Out of these the K+/Na+ ratio was above 0.7 histological evidence of myocardial infarction was absent, but other changes accounting for death were present in 17 cases. In another 16 cases a K+/Na+ ratio of 0.7 or less was the sole indication of myocardial infarction, and any other change likely to be responsible for death was absent. In two further cases a false negative result was obtained for the K+/Na+ ratio, owing in all probability to some technical error. The findings suggest that determination of the myocardial K+/Na+ ratio is a great aid in detecting early myocardial infarction. The technique is not affected by post mortem autolysis, and is simple enough for routine use.     

Role of trace elements in primary arterial hypertension

A negative relationship between water hardness and cardiovascular mortality rate was demonstrated and became a source of interest regarding minerals and trace metals in the pathogenesis of atherosclerosis, cardiovascular diseases, and arterial hypertension. Higher incidences of sudden death, cerebrovascular diseases, arterial hypertension, and coronary heart disease have been reported in soft water areas. A major research effort has been devoted to the problem in an attempt to find a protective factor in hard water or a detrimental factor or element in soft water. The roles of calcium, magnesium, cobalt, lithium, vanadium, silicon, manganese, and copper have been considered potentially beneficial, whereas those of cadmium, lead, silver, zinc, and antimony have been considered potentially harmful. Cobalt and zinc have been attributed both roles. In the present article, the role of trace quantities of several elements in mineral water in the etiopathogenesis of primary arterial hypertension is reviewed. An erratum to this article is available at .     

Role of trace elements in primary arterial hypertension Is mineral water style or prophylaxis?

A negative relationship between water hardness and cardiovascular mortality rate was demonstrated and became a source of interest regarding minerals and trace metals in the pathogenesis of atherosclerosis, cardiovascular diseases, and arterial hypertension. Higher incidences of sudden death, cerebrovascular diseases, arterial hypertension, and coronary heart disease have been reported in soft water areas. Amajor research effort has been devoted to the problem in an attempt to find a protective factor in hard water or a detrimental factor or element in soft water. The roles of calcium, magnesium, cobalt, lithium, vanadium, silicon, manganese, and copper have been considered potentially beneficial, whereas those of cadmium, lead, silver, zinc, and thallium have been considered potentially harmful. Cobalt and zinc have been attributed both roles. In the present article, the role of trace quantities of several elements in mineral water in the etiopathogenesis of primary arterial hypertension is reviewed.     

Efficacy of ozonated water against various food-related microorganisms.

The antimicrobial effects of ozonated water in a recirculating concurrent reactor were evaluated against four gram-positive and four gram-negative bacteria, two yeasts, and spores of Aspergillus niger. More than 5 log units each of Salmonella typhimurium and Escherichia coli cells were killed instantaneously in ozonated water with or without addition of 20 ppm of soluble starch (SS). In ozonated water, death rates among the gram-negative bacteria--S. typhimurium, E. coli, Pseudomonas aeruginosa, and Yersinia enterocolitica--were not significantly different (P > 0.05). Among gram-positive bacteria, Listeria monocytogenes was significantly P < 0.05) more sensitive than either Staphylococcus aureus or Enterococcus faecalis. In the presence of organic material, death rates of S. aureus compared with L. monocytogenes and E. coli compared with S. typhimurium in ozonated water were not significantly (P > 0.05) affected by SS addition but were significantly reduced (P < 0.05) by addition of 20 ppm of bovine serum albumin (BSA). More than 4.5 log units each of Candida albicans and Zygosaccharomyces bailii cells were killed instantaneously in ozonated water, whereas less than 1 log unit of Aspergillus niger spores was killed after a 5-min exposure. The average ozone output levels in the deionized water (0.188 mg/ml) or water with SS (0.198 mg/ml) did not differ significantly (P < 0.05) but were significantly lower in water containing BSA (0.149 mg/ml).     

Vitamin A Reserves of Canadians

—A survey of vitamin A and carotene stores of Canadians at five major centres across Canada was completed. Vitamin A and carotene analyses were performed on approximately 100 human liver specimens obtained at necropsy from each location.Age influenced liver vitamin A stores. Children between 1 and 10 years of age had the highest vitamin A stores while a trend toward lower liver stores occurred between 20 and 40 years of age. Females had higher liver carotene stores than males but there was no such difference in vitamin A stores.Subjects from all locations were classified according to cause of death: accidental, heart and coronary artery diseases, cancer, respiratory diseases and a miscellaneous disease group. The mean liver vitamin A and carotene stores of the accidental death group differed only from the cancer group. In contrast to the disease groups, no case with undetectable vitamin A was found in the accidental death group.The mean vitamin A and carotene stores of Vancouver subjects were generally higher than those for the other locations. Montreal showed more values in the 0-40 μg. per g. range than the other locations. Vancouver had the least number (15%), with Halifax, Ottawa and Winnipeg being intermediate (32%). These data suggest the need for improved nutrition, prophylactic treatment in disease states and the need for further research on the utilization and metabolism of vitamin A.     

Effects of temperature, and dietary magnesium and nickel levels on magnesium and nickel concentrations during the moult-cycle in Oniscus asellus (Porcellionidae, Isopoda, Crustacea).

Mean magnesium concentrations in intermoult Oniscus asellus, caged at 20 degrees C for 10 days, ranged from 1,059.15 +/- 51.9 ppm on diets containing 10 ppm nickel, to 6,827.6 +/- 314.1 ppm on a mixture of 500 ppm magnesium + 10 ppm nickel. Mean nickel concentrations ranged from 89.4 +/- 4.3 ppm on diets containing 500 ppm magnesium, to 314.0 +/- 14.8 ppm on a mixture of 500 ppm magnesium + 10 ppm nickel. At 30 degrees C, magnesium tissue concentrations ranged from 4,149.8 +/- 153.5 ppm on diets with 10 ppm nickel to 12,602.6 +/- 529.3 ppm on 500 ppm magnesium. Nickel concentrations at 30 degrees C varied from 156.8 +/- 6.7 in isopods in the control to 490.5 +/- 23.5 ppm on those on 500 ppm magnesium + 10 ppm nickel. Magnesium in intermoult isopods was mainly stored in other tissues, including the exoskeleton, and nickel in the hepatopancreas. Differences in both magnesium and nickel concentrations between males and females were not significant. Magnesium and nickel concentrations in postmoult isopods, on the average, amounted to 367.6 +/- 16.5 ppm and 18.7 +/- 0.7 ppm, respectively, at 20 degrees C, and 369.9 +/- 16.3 ppm and 30.9 +/- 1.3 ppm, respectively, at 30 degrees C. Differences between males and females, and between various treatments were not significant at P greater than 0.01. It is suggested that both hepatopancreas and other tissues, including the exoskeleton, are used as sinks to get rid of excessive tissue magnesium and nickel during the moult-cycle.