Water, cations, and norepinephrine content of cardiovascular tissues of unilaterally nephrectomized dogs treated with deoxycorticosterone and NaCl.

Deoxycorticosterone pivalate (2.5 mg/kg) given intramuscularly on four occasions 10-15 days apart over a period of 45 days to unilaterally nephrectomized adult male mongrel dogs, receiving as drinking solution 0.9% NaCl in 5% dextrose, resulted in an average sustained rise in the mean arterial blood pressure of 30 mm Hg (1 mm Hg - 133 N/m2) in 60% of the animals. Hypertensive dogs had in their arterial tissues generally more sodium, potassium, magnesium, and calcium than the similarly treated but non-hypertensive dogs, but compared to the tissues of operated untreated or unoperated normotensive dogs, only sodium and calcium were significantly higher. The dogs who were similarly treated but did not develop hypertension had in their arterial tissues less sodium, potassium, and magnesium than operated untreated or unoperated normotensive dogs. Norepinephrine content in the branches of mesenteric arteries of all deoxycorticosterone- and NaCl-treated animals, irrespective of their blood pressure, was significantly lower, and in the myocardium significantly higher, than either the unoperated normotensive or operated but not further treated dogs. It is concluded, therefore, that in deoxycorticosterone + NaCl treatment the dogs which developed hypertension had more arterial sodium, potassium, magnesium, and calcium than those who were similarly treated but remained within the limits of normal blood pressure, and that there was no difference between hypertensive and non-hypertensive dogs in regard to their cardiovascular norepinephrine content.     

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。     

Magnesium and phosphate enrichment of culture medium stimulates the proliferation of epidermal cells from newborn and adult mice

The proliferation and differentiation of mouse epidermal cells can be sequentially analyzed by modification of extracellular calcium. Newborn cells cultured in low calcium medium (less than 0.1 mM) proliferate as a monolayer and maintain a typical basal cell phenotype in culture but have a limited proliferative capacity and short lifespan. Elevation of the magnesium content of the culture medium from 1 to 5 mM stimulated the proliferation of newborn mouse (1-3 days old) keratinocytes. Maximal DNA synthesis rates, as determined on day 5 of culture, were up to 2-3-fold higher in the magnesium-enriched cultures. Exposure to high magnesium caused 3-4-fold increases in the DNA content of newborn keratinocyte cultures, and extended the confluent phase of epidermal cell growth to over 10 days. Other divalent cations (strontium, copper, zinc, nickel, beryllium, and barium) did not improve keratinocyte growth in culture. Keratinocytes from the tail skin of adult (3 months old) mice displayed an absolute requirement for high phosphate in the culture medium. The medium containing an optimal (10 mM) phosphate concentration prevented the cell detachment caused by the standard low (1 mM) phosphate medium, and in combination with an elevated magnesium content (10-15 mM) it markedly increased both DNA synthesis rates and DNA content of the adult cell cultures. Optimally growing, newborn or adult cultures contained less cells in the G1 phase of the cell cycle and more cells in S and G2 +M. The addition of phosphate and magnesium per se did not induce keratinocyte differentiation and did not interfere with the high calcium (1 mM)-induced differentiation.     

湖南烟区土壤交换性钙、镁含量及对烤烟品质的影响

分析了湖南烟区主要土壤类型交换性钙、镁元素含量状况及其对烟叶品质的影响,结果表明:(1)土壤交换性钙、镁含量在不同土壤类型间存在显著性差异,交换性钙含量平均为8.87cmol/kg,以红壤含量最高;交换性镁含量平均为1.16cmol/kg,以黄棕壤含量最高;交换性钙镁比值大小依次为:红壤(11.74)>水稻土(10.25)>黄壤(6.84)>黄棕壤(6.14),在烟叶实际生产中,应重视镁肥在红壤和水稻土中的施用;(2)烟叶钙含量偏高(21.93g/kg±4.37g/kg),烟叶镁含量偏低(2.52g/kg±1.26g/kg),两者均存在广泛的变异性;(3)整体来看,烟叶钙含量随土壤中交换性钙含量的升高和镁含量的降低而显著升高;烟叶镁含量随土壤交换性镁含量的升高而升高,与土壤交换性钙含量的相关性不显著;(4)典型相关分析表明,土壤中交换性镁含量的降低可能引起烟叶钾含量的提高,从而使得烟叶钾素和镁素含量达到较好的平衡;(5)土壤交换性钙、镁含量与烟叶其它化学成分指标的相关分析表明,土壤交换性钙有利于烟株对硼和氯素的吸收,对氮、锌和锰素的吸收则有显著的抑制作用;而土壤交换性镁有利于烟叶总糖、硼素和锰素的积累,对氮、磷、铁和锌素的吸收具有显著的抑制作用。     

Magnesium Supplementation did not Affect the Increasing Bone Zinc Concentration in Rats Given Excess Calcium as Carbonate

We investigated the effect of magnesium supplementation on zinc distribution in rats given excess calcium as carbonate. Rats were given a control diet (5 g/kg calcium and 0.5 g/kg magnesium), a high calcium diet (HC, 25 g/kg calcium and 0.5 g/kg magnesium) or the high calcium diet supplied with magnesium (HCM, 25 g/kg calcium and 2.5 g/kg magnesium) for 4 weeks. Calcium carbonate and magnesium oxide were used for increasing these mineral concentrations in diets. Although feed intake did not differ among the groups, the excess calcium suppressed feed efficiency, irrespective of dietary magnesium concentration. Femoral magnesium concentration was lower in the HC group than in the control and the HCM groups. Femoral zinc concentration was higher in the HC group and the HCM group than in the control group. The zinc concentration in the kidney was lower in the HC group and the HCM group than in the control group. The excess calcium did not affect zinc concentration in plasma and other tissues such as the liver, testis, and spleen, irrespective of dietary magnesium. These results suggest that the increasing bone zinc and the decreasing renal zinc do not result from magnesium insufficiency in rats given excess calcium as carbonate.     

Biochemical response to cadmium

The effect of daily oral administration of ethanol (2.5, 5, or 10% in drinking water for 8 wk), lead (10 mg/kg, po, once daily for 8 wk), or their combination on tissue trace-metal concentration and hematopoietic and hepatic biochemical indices was investigated in male rats. Ethanol (10%) ingestion enhanced the hepatic lipid peroxidation and decreased the calcium and magnesium content of blood and liver. Coexposure to lead and ethanol (5 and 10%) produced a more pronounced elevation of blood zinc protoporphyrin (ZPP) and hepatic lipid peroxidation. Combined lead-ethanol exposure also lowered the concentration of blood and hepatic magnesium and calcium and increased the amount of lead in the blood, liver, and brain compared to a group treated with lead alone. The results suggest that chronic alcohol ingestion results in calcium and magnesium loss. However, coexposure to lead and ethanol could result in more serious depletion of calcium and magnesium, and this could be the cause of suspected synergism between alcohol consumption and lead poisoning.     

Reduction of Brain Calcium After Consumption of Diets Deficient in Calcium or Vitamin D

Abstract: Rats fed diets deficient in calcium or vitamin D for 4 weeks displayed hypocalcemia, as indicated by a 50% reduction in serum calcium and a sevenfold elevation of serum parathyroid hormone. These treatments also decreased the calcium content of brain tissue. On a regional basis. this effect was greatest in the brain stem (24% decrease) and least in striatum (10% decrease). Subcellular analysis indicated that the depletion of brain calcium was greatest in the soluble and the microsomal fractions. Infusion of calcium solutions reversed the depletion of brain calcium produced by dietary deficiencies. In control rats. parathyroidectomy or infusion of parathyroid hormone did not alter the calcium content of brain tissue, although these treatments affected the levels of calcium in the serum. In general, these treatments had no effect on the magnesium content of serum or brain tissue. However, vitamin D deficiency did increase the magnesium content of the myelin and synaptosomal fractions. This increase was reversed by parathyroidectomy. These observations demonstrate that long-term hypocalcemia produces distinct changes in the localization of calcium and magnesium in brain tissue. Furthermore. these studies suggest that though brain calcium levels are influenced by serum concentrations, serum changes must be of large magnitude and long duration for brain calcium levels to be affected.     

Metal ion content of Escherichia coli versus cell age.

The potassium, calcium, magnesium, and zinc ion content of cells in exponential and synchronously growing cultures of Escherichia coli B/r was determined with an X-ray fluorescence spectrometer and an atomic absorption spectrophotometer. Cellular potassium, calcium, and magnesium content increased smoothly during the cell cycle, but cellular zinc showed a steplike increase about 10 to 15 min after cell division in a culture having a doubling time of 47 min. The possible role of cellular zinc in the control of cell division is discussed.     

Low intracellular magnesium in patients with acute pancreatitis and hypocalcemia.

To determine the role of magnesium deficiency in the pathogenesis of hypocalcemia in acute pancreatitis, we measured magnesium levels in serum and in peripheral blood mononuclear cells in 29 patients with acute pancreatitis, 14 of whom had hypocalcemia and 15 of whom had normal calcium levels. Only six patients had overt hypomagnesemia (serum magnesium less than 0.70 mmol per liter [1.7 mg per dl]). The mean serum magnesium concentration in hypocalcemic patients was not significantly lower than in normocalcemic patients, but the mononuclear cell magnesium content in hypocalcemic patients with pancreatitis was significantly lower than in normocalcemic patients with pancreatitis (P less than .01). The serum magnesium level did not correlate with that of serum calcium or the mononuclear cell magnesium content, but the latter did significantly correlate with the serum calcium concentration (r = .81, P less than .001). Most patients with hypocalcemia had a low intracellular magnesium content. Three normomagnesemic, hypocalcemic patients with alcoholic pancreatitis also underwent low-dose parenteral magnesium tolerance testing and showed increased retention of the magnesium load. We conclude that patients with acute pancreatitis and hypocalcemia commonly have magnesium deficiency despite normal serum magnesium concentrations. Magnesium deficiency may play a significant role in the pathogenesis of hypocalcemia in patients with acute pancreatitis.     

Magnesium Supplementation through Seaweed Calcium Extract Rather than Synthetic Magnesium Oxide Improves Femur Bone Mineral Density and Strength in Ovariectomized Rats

Commercially available seaweed calcium extract can supply high amounts of calcium as well as significant amounts of magnesium and other microminerals. The purpose of this study was to investigate the degree to which the high levels of magnesium in seaweed calcium extract affects the calcium balance and the bone status in ovariectomized rats in comparison to rats supplemented with calcium carbonate and magnesium oxide. A total of 40 Sprague-Dawley female rats (7?weeks) were divided into four groups and bred for 12?weeks: sham-operated group (Sham), ovariectomized group (OVX), ovariectomized with inorganic calcium and magnesium supplementation group (OVX-Mg), and ovariectomized with seaweed calcium and magnesium supplementation group (OVX-SCa). All experimental diets contained 0.5% calcium. The magnesium content in the experimental diet was 0.05% of the diet in the Sham and OVX groups and 0.1% of the diet in the OVX-Mg and OVX-SCa groups. In the calcium balance study, the OVX-Mg and OVX-SCa groups were not significantly different in calcium absorption compared to the OVX group. However, the femoral bone mineral density and strength of the OVX-SCa group were higher than those of the OVX-Mg and OVX groups. Seaweed calcium with magnesium supplementation or magnesium supplementation alone did not affect the serum ALP and CTx levels in ovariectomized rats. In summary, consumption of seaweed calcium extract or inorganic calcium carbonate with magnesium oxide demonstrated the same degree of intestinal calcium absorption, but only the consumption of seaweed calcium extract resulted in increased femoral bone mineral density and strength in ovariectomized rats. Our results suggest that seaweed calcium extract is an effective calcium and magnesium source for improving bone health compared to synthetic calcium and magnesium supplementation.     

Changes in the Concentration of Microelements in the Teeth of Rats in the Final Stage of Type 1 Diabetes,with an Absolute Lack of Insulin

The mineral content of tooth hard tissue may influence the rate of decay change. Considering this fact, we aimed at examining if type 1 diabetes might be a contributing factor to the appearance of tooth decay. The experiment was conducted on female Wistar rats. To induce diabetes, rats were intravenously injected with 1 mL streptozocine 0.01 M citrate buffer. The control group of rats was injected with 1 mL 0.01 M citrate buffer only. After 10 days, teeth and blood serum samples were obtained. Fluoride concentration was determined by potentiometer method, and calcium and magnesium, by AAS. Serum concentrations of glucose and estradiol in the diabetic rats were significantly higher compared to the control group. In the experimental group, a statistically significant decrease of fluorine concentration in both teeth and serum were observed. Calcium and magnesium concentrations in blood serum and dental magnesium concentration were significantly higher in rats with type 1 diabetes compared with the control. A downward trend in the content of dental calcium in streptozotocin-induced diabetic rats was observed. The results obtained indicate that caries initiation and progression could be promoted by metabolic changes associated with diabetes affecting the mineral composition of tooth hard tissue.     

The milk of the fur-seal, Arctocephalus tropicatis gazella; in particular the composition of the aqueous phase

Milk and plasma samples from the Southern fur-seal (Arctocephalus tropicalis gazella) , collected from animals shot between 0 and 26 days post-partum , have been analysed. The aqueous phase of milk (ultracentrifugate) was hyperosmotic to plasma by about 35 m-osmol/kg water but contained no lactose. The osmolality of milk could be accounted for by the ionic content, of which sodium and potassium (in approximately equal amounts) were the main cations. The fat content of the milk was very high (approximately 40%), except in very early lactation (0 and 1 day post-partum). The concentrations of chloride, calcium, magnesium, phosphate and citrate in the aqueous phase are given. Major differences between the composition of fur-seal milk and that of other mammals are pointed out, and discussed in relation to water conservation, energy and fat supply, and prolonged milk storage in this snecies.     

Ion concentrations in oviduct and uterine fluid and blood serum during the estrous cycle in the bovine

In the bovine up to 40% of embryos die before implantation but despite the importance of ions in oviduct and uterine fluid formation and in gamete, zygote and early embryo development there is very little published information on the ion concentrations of oviduct or uterine fluid. The free anions chloride, phosphate and sulphate and the free cations sodium, calcium, magnesium and potassium were measured in oviduct fluid on days 0, 2, 4 and 6 and in uterine fluid on days 6, 8 and 14 and in corresponding blood samples. Oviduct and uterine fluids were collected in situ. Sodium was 25-fold higher than potassium and 80-fold higher than the other ions and chloride was 10-fold higher than potassium and 40-fold higher than the other ions in oviduct and uterine fluid. Phosphate, sulphate, magnesium, potassium and calcium were at lower concentrations in all fluids. Oviduct calcium and sodium were higher on day 0 than other days. The most striking uterine differences were the higher potassium and lower chloride, sodium and magnesium on day 14 than other days. There were significant positive associations between oviduct and blood chloride, sulphate, magnesium and calcium while only uterine sulphate was positively related to its blood concentration. There was no relationship between fluid secretion rate and no association between the concentrations of systemic progesterone or oestradiol and any ion in oviduct or uterine fluid. The different concentrations and associations between ions in the oviduct, uterus and blood suggest a differential regulation of ion secretion by the oviduct and uterine epithelia.     

Alterations in Ca2+-ATPase activity and calcium-binding protein regucalcin mRNA expression in the kidney cortex of rats with saline ingestion

The alteration in calcium metabolism in rats ingested with saline was investigated. Rats were freely given saline as drinking water for 2 and 7 days. Calcium concentration in the serum was significantly elevated by saline ingestion for 2 and 7 days, while serum inorganic phosphorus concentration was not altered. Serum urea nitrogen concentration was significantly increased by saline ingestion for 7 days. Calcium content in the femoral-diaphyseal and metaphyseal tissues was not altered by saline ingestion for 7 days. Calcium content in the kidney cortex was significantly elevated by saline ingestion for 7 days. Ca2+-ATPase activity in the basolsateral membranes of kidney cortex was clearly increased by saline ingestion for 2 and 7 days. The enzyme activity was not altered by the addition of sodium chloride (10-3 and 10-2 M), parathyroid hormone (10-7 and 10-6 M), and calcitonin (3 × 10-8 and 3 × 10-7 M) in the enzyme reaction mixture. A calcium-binding protein regucalcin mRNA expression in the kidney cortex was markedly suppressed by saline ingestion for 7 days, although such a suppression was not seen for 2 days. These results suggest that saline ingestion causes the disturbance of calcium transport system in the kidney cortex of rats, and that the renal disorder may induce hypercalcemia.     

The impact of diets with different magnesium contents on magnesium and calcium in serum and tissues of the rat

The impact of three different magnesium diets (70, 1,000 and 9,000 ppm) on total, ionized and bound magnesium as well as ionized calcium in serum and total calcium and magnesium in femoral bone, skeletal muscle, heart and liver of male Sprague-Dawley rats was investigated. The percentage of ionized serum magnesium was unproportionally high in rats fed a low magnesium (70 ppm) diet. Femoral magnesium was correlated with ionized and total serum magnesium. In contrast, there was generally no correlation between total serum magnesium and the magnesium fractions in skeletal muscle, heart and liver. In rats fed the magnesium deficient diet, total cardiac concentration of magnesium was even significantly increased along with total calcium content, while there were no effects on total muscle and liver magnesium. Within the single groups, ionized serum calcium was never proportional to dietary magnesium, but in all three magnesium diet groups together, it was inversely correlated with dietary magnesium. Moreover, ionized serum calcium was inversely correlated with both ionized and total serum magnesium. In all 3 groups together, the concentrations of total calcium and magnesium in heart and skeletal muscle were correlated, within the single groups correlation existed only in the 1000 ppm group. Magnesium influx via calcium channels during low magnesium intake has been seen in non cardiac tissues [35,36], but nothing similar is known about non selective channels for divalent cations in the heart [33]. Thus, magnesium uptake by cardiac cells along with calcium seems to be possible, especially at low intracellular magnesium concentrations, but is still poorly investigated. We suggest that the calcium-antagonistic effect of magnesium is related to the turnover rate of magnesium rather than to its tissue concentrations.     

Content and deposition of major mineral elements in different tissues and empty body of growing bulls of the german simmental breed

54 bulls of the German Simmental breed were fed either on a high energy level (maize silage ad libitum and 1.8 kg concentrate) or on a low energy level (maize silage restrictively and 1.0 kg concentrate). In dependence on feeding intensity a mean daily weight gain of 870 or 1210 g was obtained. Animals were slaughtered with a live mass of 200 kg, 350 kg, 500 kg, 575 kg and 650 kg. Empty body was divided into 13 cuts and afterwards separated into lean, bone and adipose tissues and tendons. Major mineral element content was determined in these tissues as well as in the noncarcass parts.

In the lean tissue the mean content (200 kg) of 0.3 g calcium, 10 g phosphorus, 1 g magnesium, 2.3 g sodium and 14.8 g potassium/kg dry matter decreased slightly with rising live mass (200–650 kg). The contents of major mineral elements were much higher in bone tissue. For the fattening period from 200 to 650 kg of live mass mean contents of 151.5 g calcium, 71.3 g phosphorus, 3.2 g magnesium, 5.1 g sodium and 1.1 g potassium per kg DM were analysed. Mineral element content of bone tissue increased with rising live mass as well as animals on low feeding intensity showed a higher mineral content than on high energy level. In all, major mineral element content in fat tissue was very low. In noncarcass parts head and legs calcium and phosphorus had analogous to bone tissue the highest concentration. Hide showed a high content of sodium, whereas organs and digestive tract had a high content of potassium and phosphorus. Total mass of major mineral elements in the different tissues increased above all in the fattening period of 200 to 350 kg. In carcass as well as in empty body, mass of calcium and phosphorus was much higher than magnesium, sodium and potassium. Also animals on low feeding intensity showed a higher mass of major mineral elements in carcass and empty body than animals on high energy feeding intensity. The intensively fed bulls had a mean deposition of 12.7 g calcium, 6.9 g phosphorus, 0.37 g magnesium, 1.2 g sodium and 2.1 potassium per 1000 g of empty body weight gain, whereas restrictively fed bulls deposited in average 15.0 g calcium, 7.8 g phosphorus, 0.4 g magnesium, 1.2 g sodium and 2.4 g potassium per 1000 g of empty body weight gain.     

Mineral relationships and ecological distribution of Fissidens cristatus Wils.

Abstract

Studies carried out in the laboratory indicate that Fissidens cristatus Wils., a moss of chalk and limestone grassland, requires the following conditions for optimum growth: pH, 8.0; calcium, 10 mg/1; potassium, 10 mg/1; magnesium, 50–80 mg/1; iron, less than 0.1 mg/1; It has also been demonstrated that calcium inhibits the short-term uptake of potassium from the culture solution.

Within the shoots of specimens collected from the natural habitat, the potassium content was always higher in the current growth segments, whereas that of calcium was always lower. Seasonal variations in the total content of calcium, potassium and magnesium were observed.

The need to wash material collected in the field prior to chemical analysis has been established and the results are discussed in relation to the distribution and local environmental contamination of F. cristatus.     

Ionic and acid-base consequences of exposure to increased salinity in the zebra mussel, Dreissena polymorpha

Dreissena polymorpha, an invasive freshwater bivalve, displays physiological characteristics that reflect its ancestry in brackish water, yet it has limited ability to withstand modest increases in salinity. We examined changes in hemolymph ion concentrations and acid-base variables in mussels transferred to and incubated in 10% artificial seawater (ASW) for 7 days and then returned to pondwater (PW) for a further 7 days. Hemolymph was sampled (10 animals per sample period) every 4 h for the first 24-h incubation and at 72 h and 168 h for both the transfer to 10% ASW and the transfer back to PW. The initial response to transfer to 10% ASW was a rapid attainment of an apparent isoosmotic steady state, with most hemolymph ion concentrations rising and attaining steady state within 12 h. Hemolymph magnesium rose more slowly, and hemolymph calcium declined despite an increase in its concentration in the bathing medium. Hemolymph pH rose significantly during the first 24 h, from 7.96 to 8.25, as a result of increases in bicarbonate; pH subsequently returned to normal through increases in PCO2. When animals were returned to PW after 7 days' incubation in ASW, the response of the major hemolymph ions was largely the reverse of that effected by the transfer to ASW. Hemolymph pH was not altered significantly until after 72 h in PW, when declines in bicarbonate lowered the pH to 7.73. Strong ion difference (SID) was related significantly to hemolymph pH. Hemolymph calcium and magnesium showed a reciprocal relationship throughout both transfer and incubation. Solubility interactions between sulfate and calcium and magnesium may be important in determining calcium availability in solution. The Na/K ratio in hemolymph was maintained within relatively narrow bounds throughout the procedure and may contribute to the mussels' ability to volume-regulate during an osmotic challenge. Overall, the responses of D. polymorpha to modest changes in salinity were largely the result of passive processes.     

Mineral uptake in tobacco leaf discs during different developmental stages of shoot organogenesis

Relationships between mineral uptake and tobacco shoot organogenesis were investigated during three morphogenic phases: phase 1, days 0-10, pre-meristem formation; phase 2, days 10-20, meristem initiation and formation; and phase 3, days 20-35, growth and differentiation of induced meristems into leafy shoots. The mineral content of both shoot-forming (SF) and non-shoot-forming (NSF) media was examined over the 35-day culture period. Both SF and NSF explants rapidly consumed iron during phase 1. Nitrate uptake in SF explants was high and independent of explant growth during phases 1 and 2, but greatest and strongly correlated with growth during phase 3. Phosphorus uptake was highest in SF explants during phases 2 and 3, and correlated with explant growth. Uptake of potassium, calcium and sulphur was strongly associated with explant growth during phase 3 whereas magnesium uptake was only poorly correlated with growth. Results from this study indicate that particular minerals may have an important role in regulating development as well as generally supporting growth.     

Effects of niacin on bleomycin-induced increases in myeloperoxidase,prolyl hydroxylase,and superoxide dismutase activities and collagen accumulation in the lungs of hamsters

It has been shown that lung nicotinamide adenine dinucleotide (NAD) depletion accompanies bleomycin (BL)-induced lung fibrosis in the hamster and that treatment with niacin (NA), a precursor of NAD, was found to attenuate lung fibrosis caused by this agent. Niacin was used in the present study to investigate changes in some biochemical parameters and enzymes involved in the development of BL-induced lung fibrosis in the hamster. Niacin (500 mg/kg, IP), or an equivalent volume of saline (SA, IP), was given daily 2 days prior to intratracheal instillation of BL (7.5 U/5 mL/ kg) or SA and everyday thereafter throughout the study. Hamsters were killed at 1, 4, 7, 10, and 14 days after the BL or SA instillation and their lungs processed for various biochemical assays. Hydroxyproline content and superoxide dismutase (SOD) activity in SABL treated animals were significantly (P ± 0.05) elevated at 7 and 10 days, peaking at 14 days to 161 ± 11% and 159 ± 11% of the SASA treated animals, respectively. Although the hydroxyproline level of NABL treated animals was significantly elevated at 7 and 10 days and peaked at 14 days to 123 ± 8% of the NASA control, these values were significantly lower than the SABL treated animals at the corresponding times. The lung SOD activity of NABL groups was significantly higher at 4 days but significantly lower at 10 and 14 days than the SABL groups at the corresponding times. Prolyl hydroxylase (PH) activity and total lung calcium in SABL treated groups were significantly elevated compared to SASA treated groups starting at 4 days, with PH peaking at 10 days to 163 ± 13% and calcium peaking at 7 days to 148 ± 8% of SASA treated groups. The NABL treated animals displayed a significant elevation in PH activity at 4 days only (132 ± 15%), while the calcium content in this group was significantly increased at 4 and 14 days compared to NASA treated animals. However, the activity of PH in the NABL treated animals was significantly lower than the SABL treated animals at 7, 10, and 14 days. The calcium content of the NABL group was significantly lower than the SABL group at 7 and 10 days. The thiobarbituric acid reactive substance equivalents (TBARS) content and myeloperoxidase (MPO) activity were significantly elevated at all time points in SABL groups as compared to SASA groups, with peak elevation of TBARS to 160 ± 9% at 4 days and MPO to 268 ± 40% at 1 day. The TBARS content of NABL groups was significantly elevated above NASA groups at 1, 4, 7, and 10 days. The MPO activity in NABL groups was significantly elevated above NASA groups at 1, 4, 7, and 14 days, but the activity was significantly lower than SABL groups at 4 and 14 days. The data suggest that NA inhibits the extent of oxidative damage or enhances processes involved in the repair of BL-induced alveolar epithelial damage.