Changes of total content of serum magnesium in elderly Chinese women with osteoporosis

Objective To explore whether the serum levels of magnesium (Mg) and calcium (Ca) differ between osteoporotic and nonosteoporotic elderly Chinese women. Methods Using WHO classification criteria based on bone mineral density (BMD), general healthy Chinese women older than 65 yr were classified as osteoporosis (OP), osteopenia, and normal group according to the T-score of the femur neck. Then their physical characteristics, serum levels of magnesium (sMg), calcium (sCa), and other biochemical measurements were analyzed. Results Altogether, 324 subjects were included in the final analysis with 77 in OP, 137 in osteopenia, 110 in normal group. The level of sMg in women with OP is significantly higher (0.91±0.11 mmol/L) than both the osteopenia (0.88±0.09 mmol/L) and the normal (0.87±0.08 mmol/L) even after being adjusted for both age and body mass index (BMI), which might result from potentially low levels of sCa. sMg inversely related to sCa in subjects with OP (r=−0.240, p=0.038), whereas the total levels of sCa and sMg kept relatively steady. Conclusion High content of sMg and potentially low content of sCa could be a feature of the serum profile of elderly Chinese women with OP, the clinical significance of which needs further elucidation. Supplementation of Mg for elderly Chinese women with OP did not appear to be necessary.     

Analysis of zinc and magnesium levels in pinealectomized chicks

Melatonin is the main product of the pineal gland, and trace metals play a critical role in growth and development. The purpose of this study was to assess the serum zinc (Zn) and magnesium (Mg) levels in pinealec-tomized chicks and their possible interactions with the development of spinal deformity. Chicks were divided into two equal groups: unoperated controls (group M) and pinealectomized chicks (group N). Pinealectomies were performed at the age of 3 d. After 8 wk, serum Zn and Mg levels of 10 animals from each group were measured by spectrophotometric assay. The results of analyses were compared using the Mann-Whitney U-test. The correlation between serum Zn and Mg levels were assessed by Spearman's correlation. In this study, it was obvious that the serum Zn levels in group N were significantly lower than those in group M (2.8±0.10 vs 4.2±0.14 ppm; p<0.0005). In contrast, Mg levels in group N was high compared with the values in group M, although there was no significant difference (17.8±0.69 vs 15.7±0.85 ppm; p>0.05). In pinealectomized animals, serum Zn levels declined significantly while serum Mg levels increased, albeit insignificantly. Thus, there was a moderately positive but not statistically significant correlation between Mg and Zn levels in unoperated controls (r=0.273, p>0.05), whereas there was a negative but not statistically significant correlation between Zn and Mg levels in pinealectomized chicks (r=−0.115, p>0.05). In addition, the serum Mg to serum Zn ratio was significantly higher in group N than in the group M control (6.39±0.32 vs 3.75±0.22, respectively; p<0.001). From the results of the current study, it is clear that surgical pinealectomy in newly hatched Hybro Broiler chicks has a significant effect on serum Zn level. However, the serum Mg did not change significantly. Because serum Mg is not a good indicator of Mg status in chicks, it is speculated that other tissues, such as muscle or spine, might productively be explored as a more sensitive Mg biomarker for this model. The present study provides experimental evidence that serum trace metal levels might be affected in pinealectomized animals because of the lack of its main neurohormone melatonin.     

Changes of total content of magnesium and zinc status in patients with chronic toxoplasmosis

The aim of this study was to investigate the effects of the Toxoplasma gondii infection on the total content of the essential elements Zn and Mg levels. Plasma zinc and magnesium concentrations were measured in 158 patients whose anti-T gondii IgG antibodies were positive. Scores were obtained for the patients and their age- and sex-matched 82 sero-negative healthy controls. The mean concentration of Mg in blood was significantly lower in sero-positive patients than in their controls both in females (p<0.01) and males (p<0.01). The average Zn concentration in seropositive female patients was 0.72±0.2 mg/L and 0.65±0.1 mg/L in controls (p>0.05). The mean values of the Zn in blood were 1.00±0.3 mg/L in seropositive male patients and 0.84±0.2 in controls (p>0.05). No correlation could be demonstrated between age and mean values of Zn and Mg in both sero-positive females/males and controls (p>0.05). No significant correlation could be found between blood Zn and Mg levels in seropositive female/male patients and controls (p>0.05). Mg levels were found to be clearly decreased in the patients with chronic toxoplasmosis, whereas no change was observed in Zn levels.     

Block of single cardiac sodium channels by intracellular magnesium

Currents through single cardiac sodium channels have been measured in inside-out patches from guinea pig ventricular cells. To abolish the fast inactivation, Na channels were modified by DPI 201–106. In symmetrical Na solutions, a diminution of outward sodium currents can be observed that depends on the intracellular magnesium concentration and the membrane potential. Inward currents were not altered by the concentrations of magnesium used (between 0 and 22.5 mmol/1). In Mg free solutions a linear current-voltage relation can also be measured in the range of outward Na currents. At +60 mV (symmetrical Na solutions, single channel conductance 24 pS) a half maximal block of cardiac Na channels by intracellular magnesium was found at 2.1 mmol/l. From the analysis of single channel current-voltage relationships the concentration and voltage-dependent block by intracellular magnesium of cardiac sodium channels could be described as binding of Mg at one site with a K _d value of 5.1 mmol/1 at 0 mV. The site is located at an electrical distance of 0.18 from the inside. Offprint requests to: B. Nilius     

Contribution of dissolved calcium and magnesium to phytoplanktonic particulate phosphorus concentration at the heads of two river reservoirs

At the heads of two river reservoirs, the Ishitegawa Dam and the Nomura Dam Reservoirs in Japan, the concentrations of phytoplanktonic particulate phosphorus (PP) were compared with those of dissolved calcium (Ca) and magnesium (Mg), using multiple regression analyses on the data taken from samples which registered more than 6.0 µg l^–1 in chlorophyll a concentration. Of the 27 monthly samples, 16 from the Ishitegawa Reservoir and 17 from the Nomura Reservoir were used. A significant regression line, logPP = k ₁F + k ₂, was obtained, where k ₁ (> 0) and k ₂ were constants and F (named the Ca-Mg index) consisted of log(Ca/Mg) – 0.5 log(ca + Mg) in mol concentration in Ca and Mg, in common with the two reservoirs (r ² = 0.730 & 0.913).     

Alteration in cardiomyocyte mechanics by suboptimal levels of extracellular magnesium

The beneficial effects of magnesium supplementation in pathological situations is well known, but the myocardial response to a nominal decrease in the level of magnesium has received relatively little attention. Hypomagnesemia can occur as chronic or acute manifestation of physiological changes, pathological conditions, or pharmacological interventions. Experimental interest was focused on the mechanical changes in adult rat heart myocytes following variation in extracellular Mg²⁺. Isolated cells were exposed to different levels of extracellular Mg²⁺ and the amplitude and rate of contraction were measured as a function of change in cell length using a video-based edge-detection system. Investigations have revealed that variation in the level of Mg²⁺ within physiological limits leads to mechanical changes. A decrease in the level of extracellular Mg²⁺ was accompanied by a significant increase in contractile amplitude and decrease in the velocities of contraction and relaxation. The contractile amplitude measured as percentage shortening were 3.08 ± 0.19%, 4.62 ± 0.19% and 6.9 ± 0.40%, respectively, on exposure to 1.8, 0.8, and 0.48 mM Mg, and the corresponding velocities of contraction and relaxation normalized to amplitude were 0.54 ± 0.02, 0.40 ± 0.03, 0.31 ± 0.03 and 0.47 ± 0.02, 0.35 ± 0.02, 0.24 ± 0.02. The variations in contractile parameters associated with the change in the level of Mg were statistically significant (p < 0.01). Variation in the contractile properties associated with change in extracellular Mg²⁺ may be effected by alteration in Ca²⁺ transients.     

Correlation of serum trace elements and melatonin levels to radiological, biochemical, and histological assessment of degeneration in patients with intervertebral disc herniation

The aim of our study was to assess the blood concentrations of some trace elements and melatonin (MLT) in patients with intervertebral disc herniation (IDH) and to investigate the interaction of histological and biochemical degeneration findings with aging. The present study was carried out on 13 subjects (8 women and 5 men) diagnosed with IDH. They were divided into three groups according to their ages. Nighttime serum MLT, zinc (Zn), and magnesium (Mg) levels were determined in all patients. In addition, computed tomography (CT) scan of the brain and magnetic resonance imaging examination of the lumbar spine were obtained in this study. The Zn level and Zn/Mg ratio showed a decline in patients with IDH with aging, whereas the serum Mg level and tissue hydroxyproline content increased. A positive correlation between serum Zn and MLT concentrations was found (r=0.104, p=0.734). In addition, there was a positive correlation between serum Zn level and Zn/Mg ratio (r=0.835 and p<0.01), and a negative correlation between serum Mg level and Zn/Mg ratio (r=−0.571, p<0.05). On CT study, both volume percentage of calcified pineal gland and density of calcification were found to increase progressively with advancing age. The results of semiquantitative evaluation of disc tissues of patients with IDH for histological degeneration findings showed that 66.7% of discs treated had slight degeneration in younger age group, but 75.0% and 100% of discs had moderate or marked degeneration in older age groups. Our data indicated that there is a close relationship between MLT and Zn or Mg levels in the serum samples of patients with IDH, and the levels of these elements might be affected by the presence of degeneration process and serum MLT level, or vice versa.     

Time course of antioxidant responses of Capsicum annuum subjected to a progressive magnesium deficiency

The effect of magnesium (Mg²⁺)‐deficiency on the antioxidant responses of Capsicum annuum was investigated over a 60‐day period under controlled conditions. This Mg²⁺‐deficiency aimed to mimic the physiological conditions that plants may experience in the field. At each harvest time, five different leaf‐levels (L2 to L6) were distinguished. L2 and L6 correspond to the second and sixth youngest leaves, respectively. The following parameters were determined: Mg²⁺, chlorophyll and protein contents, total and redox pools of ascorbate and glutathione, and the activities of superoxide dismutase, ascorbate peroxidase, dehydroascorbate reductase, and glutathione reductase. Under Mg²⁺‐deficiency, leaf Mg²⁺ contents decreased over time in all leaf‐levels except in the second youngest leaves (L2), where they remained constant at about 0.25% (dry weight basis). Mg²⁺‐deficiency led to an increase in the antioxidant enzyme activities concomitant with an increase in the ascorbate and glutathione pools, whereas total chlorophyll and soluble protein contents decreased. The L2 leaves showed an increase in glutathione reductase activity and in the ascorbate redox state whereas no difference was observed for the other parameters. Superoxide dismutase activities increased in L5 leaves from day 15 and, afterwards, in L3 to L5 leaves, irrespective of Mg²⁺ content. At day 30, glutathione reductase activities increased in L2 to L4 leaves and dehydroascorbate reductase activities in L4 leaves. At day 45, we observed an increase in the ascorbate peroxidase activities in L3 to L5 leaves. At the same time, ascorbate and glutathione pools increased in intermediate leaves, whereas chlorophyll content decreased in L3 and L4 leaves, and protein content decreased in L4 leaves. Results suggest that pepper leaves enhance their defence capacities against oxidative stress by increasing ascorbate more than glutathione synthesis. However, cells showed higher regeneration rates for the glutathione redox state than for the ascorbate redox state.     

Luxury uptake of magnesium by peas,Pisum sativum

Increasing the magnesium (Mg) concentration of vegetables (biofortification) will often require ‘luxury’ uptake where the whole‐plant concentration of Mg (c_p) is greater than required for maximum yield. Our aim was to quantify some of the physiological factors influencing luxury uptake of Mg to aid subsequent development of agronomic techniques for biofortification. Peas, Pisum sativum, were used as a test species. A sand culture experiment related vegetative growth and c_p for plants grown with a range of Mg and potassium (K) supply rates. We developed a model of Mg uptake including feedback control exerted by c_p. The model was parameterised with results from a solution culture experiment and then used to explore ways to increase luxury uptake of Mg. Feedback control of Mg uptake by c_p was weak. Biomass did not increase if the Mg concentration exceeded 0.11% in the whole plant or 0.13% in the shoots. Values obtained in the field are often larger than this. Our results indicate that luxury uptake of Mg by peas is readily achieved, provided that there is ample supply of Mg²⁺ to the root surfaces. In field soils though, transport of Mg²⁺ to the roots may limit uptake and cation exchange processes restrict the ability of Mg fertilisers to substantially increase Mg uptake. Increasing root growth will usually increase Mg uptake, but c_p may not rise if biomass is also increased.     

Magnesium supplementation and iron status among female students: The intervention study

BackgroundLiterature data indicate the benefit of magnesium (Mg) supplementation. The aim of this study was to examine the effect of short-term Mg supplementation on iron status in healthy female participants.MethodsOne hundred healthy female students of the University of Belgrade - Faculty of Pharmacy participated the study during eleven intervention days. Students ingested Mg preparations with the same dose of the active substance. The analysis included the measurement of serum iron, unsaturated iron binding capacity (UIBC), total iron binding capacity (TIBC), total Mg (tMg), ionized Mg (iMg), complete blood count, met-, carboxyand oxy-haemoglobin (metHgb, COHgb, O2Hgb). Transferrin concentrations and percentage of transferrin saturation (SAT) were calculated manually. The association among the analyzed biochemical parameters was examined using polynomial regression. A principal component analysis (PCA) was used for the evaluation of interdependence between the analyzed parameters.ResultsA statistically significant trend for change in O2Hgb (%) by tertiles of iMg concentrations was found (P = 0.029). Serum tMg reached significant positive correlation with the SAT at concentration levels greater than 0.9 mmol/L, after 11 days of intervention (R2=0.116). Ionized Mg in a concentration higher than 0.6 mmol/L is positively correlated with SAT and serum Fe (R2=0.214; 0.199, respectively). PCA revealed variability of 64.7% for two axes after 11 days.ConclusionsMg supplementation leads to an improvement in the certain iron status parameters even in individuals with optimal levels of these indices. However, caution should be exercised when supplementing Mg, and laboratory monitoring of the interaction is required.     

Effect of various degrees and duration of magnesium deficiency on lipid peroxidation and mineral metabolism in rats

Severe magnesium (Mg) deficiency changed mineral homeostasis, increased lipid peroxidation, and reduced Mg²⁺/Ca²⁺ antagonism. To investigate whether the pathobiochemical effects directly correlate with the degree of Mg deficiency or whether there might be a threshold for significant alterations, diets with 70, 110, 208, 330, and 850 ppm of Mg were fed to growing Wistar rats. After feeding the diets for 0, 10, 20, and 30 days, parameters of free radical action (malondialdehyde and vitamin E content), mineral content (Mg, Ca, Fe, Zn) in various tissues (liver, spleen, heart, kidney, muscle) and plasma parameters (Mg, Ca, Fe, Zn, alanine- and aspartate-aminotransferase, tumor necrosis factor- [TNF-] were analyzed. The tissue Mg content was either unchanged or only slightly reduced in severe Mg deficiency. The iron (Fe) content rose when the extracellular Mg²⁺ concentration was below 0.25 mmol/L. There was a close positive correlation between the tissue Fe and the malondialdehyde content and a negative correlation between the malondialdehyde and the vitamin E content. Below the threshold of about 0.25 mmol/L of plasma Mg²⁺ concentration, elevated zinc (Zn) concentrations were found in liver and kidney as well as in plasma increased transaminases and TNF-. The same threshold could be observed for the increase of tissue calcium (Ca) content, except in the kidney where calcifications were found already in less severe Mg deficiency. Concerning changed mineral homeostasis with subsequent lipid peroxidation and membrane damage, plasma Mg²⁺ concentrations must be below 0.25 mmol/L: above this threshold effects of Mg deficiency alone can be compensated.     

Serum zinc and magnesium levels in patients with blastocystosis

The aim of the study was to investigate the total content of the essential elements of zinc and magnesium levels in patients infected with Blastocystis hominis. Zinc and magnesium concentrations were measured in 52 patients who were positive for the intestinal parasite Blastocystis hominis. Scores were obtained for the positives and their age- and sex-matched 60 Blastocystis hominis-negative healthy controls. For comparison of two groups of continuous variables, the independent samples t-test was used. The mean concentration of magnesium in blood was significantly lower in Blastocystis hominis-positive patients than in their controls both in females (p<0.05) and males (p<0.05). The average zinc concentration in Blastocystis hominis-positive female patients was 0.61±0.2 mg/L and 0.60±0.2 mg/L in controls (p>0.05). The mean values of the zinc in blood were 0.62±0.2 mg/L in Blastocystis hominis-positive male patients and 0.82±0.1 in controls (p>0.05). No correlation could be demonstrated between age and mean values of zinc and magnesium in Blastocystis-positive females/males and controls (p>0.05). No significant correlation could be found between blood zinc and magnesium levels in Blastocystis-positive female/male patients and controls (p>0.05). Magnesium levels were found to be clearly decreased, whereas no change was observed in zinc levels in the patients with Blastocystis compared to controls.     

Responsivenes of total content changes of magnesium and zinc status in patients infected with Giardia intestinalis

The aim of the study was to investigate the changes of total content of the essential elements of zinc and magnesium levels in patients infected with Giardia intestinalis. Zinc and magnesium concentrations were measured in 64 patients who were positive for the intestinal parasite G. intestinalis. Scores were obtained for the positives and their 60 age- and sex-matched G. intestinalis-negative healthy controls. The mean concentration of magnesium in blood was significantly lower in G. intestinalis-positive patients than in their controls both in females (p<0.05) and males (p<0.05). The average zinc concentration in G. intestinalis-positive female patients was 0.76±0.3 mg/L and it was 0.60±0.2 mg/L in controls (p>0.05). The mean values of the zinc in blood were 0.73±0.2 mg/L in G. intestinalis-positive male patients and 0.82±0.1 mg/L in controls (p>0.05). No correlation could be demonstrated between age and mean values of zinc and magnesium in both G. intestinalis-positive females/males and controls (p>0.05). No significant correlation could be found between blood zinc and magnesium levels in G. intestinalis-positive female/male patients and controls (p>0.05). Magnesium levels were found to be clearly decreased, whereas no change was observed in zinc level in the patients infected with G. intestinalis compared to controls.     

Serum selenium versus lymphocyte subsets and markers of disease progression and inflammatory response in human immunodeficiency virus-1 infection

Serum selenium levels were determined cross-sectionally in 57 HIV-infected patients who were classified according to the Centers for Disease Control (CDC) 1993 classification system. Mean serum selenium levels were lower in CDC stage II (58.7±12.2 μg/L;p<0.01;n=18) and stage III (47.6±11.3 μg/L;p<0.01;n=19) HIV-infected patients, than in healthy subjects (80.6±9.6 μg/L;n=48) and stage I patients (73.6±16.5 μg/L;n=20). Serum selenium levels were positively correlated with CD4 count, CD4/8 ratio, hematocrit, and serum albumin (r=0.42;r=0.39;r=0.48; andr=0.45;p<0.01, respectively) and inversely with serum levels of thymidine kinase (r=−0.49;p<0.01;n=49) and β2-microglobulin (r=−0.46;p<0.001;n=49). In addition, serum selenium levels in 20 randomly selected AIDS-free individuals (CDC I:n=10; CDC II:n=10) were inversely correlated with serum concentrations of interleukin-8 (IL-8) and soluble tumor necrosis factor receptors (sTNFR) types I and II. There was no correlation with serum immuneglobulin A and total serum protein levels. The results show that the progressive deprivation of serum selenium in HIV-infection is associated with loss of CD4⁺-cells and with increased levels of markers of disease progression and inflammatory response.     

Zinc content of normal human serum and its correlation with some hematic parameters

Numerous studies have demonstrated that several diseases and stress conditions are associated with changes in the levels of zinc in the blood plasma and cellular elements. In this research the association between serum zinc concentrations and other hematic parameters of diagnostic interest has been evaluated. Quantitative determinations of zinc, total plasmatic proteins, albumin, hemoglobin and calculation of mean corpuscular volume were performed on blood samples from 58 males aged 20–61 years. Concentrations measured in our sample are comparable with reference values. Statistically significant correlation coefficients were found between age and albumin (r = - 0.562, P < 0.001), serum zinc and albumin (r = 0.328, P < 0.05), serum zinc and hemoglobin (r = 0.291, P < 0.05), and total plasmatic proteins and albumin (r = 0.463, P < 0.001). These correlation coefficients were significant even after adjustment for age effect. The determination of serum zinc concentration may be useful in the assessment of clinical scenarios. Particularly, it may provide additional information for the diagnosis of specific pathologies, such as hepatic malfunctions. It could also be useful in the identification of different stages of anemia.     

Effects of lithium on thrombopoiesis in patients with low platelet cell counts following chemotherapy or radiotherapy

Therapy for neoplasma is limited by hematological side effects of tumor-destructive therapy and, in part, makes expensive supportive care necessary to overcome and treat leukopenia and thrombocytopenia and their consequences. Thrombocytopenia is a major clinical problem caused by chemotherapy and radiotherapy. An effective and very cost-effective option for treating moderate neutropenia is the administration of lithium carbonate. Lithium induces the release of colony-stimulating factors (CSF) and therefore stimulates proliferation of neutrophil granulocytes. Other cytokines, such as interleukin-1 (IL-1), IL-6, and tumor-necrosis factor-α (TNF-α), are also stimulated. Apart from granulocyte-macrophage-CSF (GM-CSF), there have as yet been no reports of lithium salts inducing early activating factors for the megakaryocytic lineage, such as IL-3, IL-11, stem cell factor and flt-3 ligand, or maturation factors, such as thrombopoietin (TPO). A statistically significant increase in the mean number of platelets for patients with cell counts below 150,000/μL on the commencement of treatment with lithium carbonate could be observed. Patient tolerability of lithium carbonate therapy is very good. Patients with persistent leukopenia and thrombocytopenia following chemotherapy or radiotherapy can be treated with this trace element very cost-effectively. Unfortunately this treatment has not gained acceptance in clinical oncology in the face of extremely cost-intensive treatment with recombinant GM-CSF, IL-11 or, potentially, thrombopoietin.     

Capillary electrophoresis coupled with end‐column electrochemiluminescence for the determination of ephedrine in human urine,and a study of its interactions with three proteins

A tris(2,2‐bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺)‐based electrochemiluminescence (ECL) detection coupled with capillary electrophoresis (CE) method has been established for the sensitive determination of ephedrine for the first time. Under the optimized conditions [ECL detection at 1.15 V, 25 mmol/L phosphate buffer solution (PBS), pH 8.0, as running buffer, separation voltage 12.5 kV, 5 mmol/L Ru(bpy)₃²⁺ with 60 mmol/L PBS, pH 8.5, in the detection cell] linear correlation (r = 0.9987) between ECL intensity and ephedrine concentration was obtained in the range 6.0 × 10^–8–6.0 × 10^–6 g/mL. The detection limit was 4.5 × 10^–9 g/mL (S:N = 3). The developed method was successfully applied to the analysis of ephedrine in human urine and the investigation of its interactions with three proteins, including bovine serum albumin (BSA), cytochrome C (Cyt‐C) and myoglobin (Mb). The number of binding sites and the binding constants between ephedrine and BSA, Cyt‐C and Mb were 8.52, 12.60, 10.66 and 1.55 × 10⁴ mol/L, 6.58 × 10³ mol/L and 1.59 × 10⁴ mol/L, respectively. Copyright © 2011 John Wiley & Sons, Ltd.     

Calcium,magnesium, and serum factors in multiplication of normal and transformed human lung fibroblasts

Summary Serum factors determine the extracellular requirement for both Ca²⁺ and Mg²⁺ for multiplication of normal human lung fibroblasts in vitro. Serum factors also affect the extracellular Ca²⁺ requirement for transformed fibroblasts but to a different extent than for normal cells. Transformed cells exhibit a reduced requirement for both Ca²⁺ and Mg²⁺ for multiplication. The apparent reduction in Ca²⁺ requirement of transformed cells is dependent on the level of serum factors in the medium. The reduced Mg²⁺ requirement for transformed cells is more striking than the loss of Ca²⁺ and independent of the level of serum factors in the medium. A sequential effector relationship among serum factors, Ca²⁺ and Mg²⁺, in a proliferative control system for normal cells is proposed. Alteration or bypass of an intracellular Mg²⁺-requiring process is proposed as a major lesion in the transformed cells. This alteration causes an observed loss of requirements for both Ca²⁺ and serum factors for the multiplication of transformed cells. This work was supported by Grant CA-15305 from the National Cancer Institute, Contract 223-74-1156 from the Bureau of Biologics, Food and Drug Administration, HEW Biomedical Research Support Grant S07RR05800, and the W. Alton Jones Foundation.     

Accumulation of magnesium ions during fermentative metabolism in Saccharomyces cerevisiae

When cells of Saccharomyces cerevisiae were grown aerobically under glucose-repressed conditions, ethanol production displayed a hyperbolic relationship over a limited range of magnesium concentrations up to around 0.5 mM. A similar relationship existed between available Mg²⁺ and ethanol yield, but over a narrower range of Mg²⁺ concentrations. Cellular demand for Mg²⁺ during fermentation was reflected in the accumulation patterns of Mg²⁺ by yeast cells from the growth medium. Entry of cells into the stationary growth phase and the time of maximum ethanol and minimum sugar concentration correlated with a period of maximum Mg²⁺ transport by yeast cells. The timing of Mg²⁺ transport fluxes by S. cerevisiae is potentially useful when conditioning yeast seed inocula prior to alcohol fermentations. Received 04 March 1996/ Accepted in revised form 21 August 1996     

Thermoluminescence properties of lithium magnesium borate glasses system doped with dysprosium oxide

We report the impact of dysprosium (Dy³⁺) dopant and magnesium oxide (MgO) modifier on the thermoluminescent properties of lithium borate (LB) glass via two procedures. The thermoluminescence (TL) glow curves reveal a single prominent peak at 190 °C for 0.5 mol% of Dy³⁺. An increase in MgO contents by 10 mol% enhances the TL intensity by a factor of 1.5 times without causing any shift in the maximum temperature. This enhancement is attributed to the occurrence of extra electron traps created via magnesium and the energy transfer to trivalent Dy³⁺ ions. Good linearity in the range of 0.01–4 Gy with a linear correlation coefficient of 0.998, fading as low as 21% over a period of 3 months, excellent reproducibility without oven annealing and tissue equivalent effective atomic numbers ~8.71 are achieved. The trap parameters, including geometric factor (μ_g), activation energy (E) and frequency factor (s) associated with LMB:Dy are also determined. These favorable TL characteristics of prepared glasses may contribute towards the development of Li₂O–MgO–B₂O₃ radiation dosimeters. Copyright © 2015 John Wiley & Sons, Ltd.