Muscularity and adiposity in addition to net acid excretion as predictors of 24-h urinary pH in young adults and elderly.

OBJECTIVE: In patients with nephrolithiasis, an inverse relationship between 24-h urinary pH (24h-UpH) and body weight has been reported. Whether body composition indices and 24h-UpH are similarly associated in healthy subjects needs investigation. DESIGN: Cross-sectional, retrospective analysis. SETTING: Dortmund, Germany and Gothenburg, Sweden. SUBJECTS: Healthy young adults (18-23 years; n=117) and elderly (55-75 years; n=85) having a mean body mass index (BMI) of 22.80+/-3.4 and 25.3+/-3.9 kg/m2, respectively. METHODS: Anthropometric data, 24h-UpH, and 24-h urinary excretion rates of net acid (NAE), creatinine, and urea were determined. After adjusting for urea (reflecting protein intake), renal creatinine output was used as a biochemical marker for muscularity. The BMI served as a marker of adiposity. RESULTS: NAE, body weight, and BMI were significantly (P<0.05) higher, and height and creatinine significantly lower in the elderly, whereas body-surface area (BSA) was not different. Step-wise multiple regression analysis using BSA-corrected urinary variables revealed NAE as the primary predictor of 24h-UpH (with R2 values of 0.64 and 0.68 in young adults and elderly, respectively, P<0.0001), followed by urea (P<0.0001), creatinine (P<0.05), and BMI (P<0.05 for the young adults and P=0.12 for the elderly). These associations were negative for NAE and BMI, and positive for urea and creatinine. CONCLUSIONS: Muscularity (i.e. creatinine adjusted for urea) and particularly in the group of young adults, adiposity (i.e. BMI) proved to be modest, but significant predictors of 24h-UpH. Future research should focus on more obese subjects in whom insulin resistance and particular kidney functions should also be examined to further substantiate the role of obesity in low-urine pH-associated conditions, for example, nephrolithiasis.

Supplementation with alkaline minerals reduces symptoms in patients with chronic low back pain.

The cause of low back pain is heterogeneous, it has been hypothesised that a latent chronic acidosis might contribute to these symptoms. It was tested whether a supplementation with alkaline minerals would influence symptoms in patients with low back pain symptoms. In an open prospective study 82 patients with chronic low back pain received daily 30 g of a lactose based alkaline multimineral supplement (Basica) over a period of 4 weeks in addition to their usual medication. Pain symptoms were quantified with the "Arhus low back pain rating scale" (ARS). Mean ARS dropped highly significant by 49% from 41 to 21 points after 4 weeks supplemention. In 76 out of 82 patients a reduction in ARS was achieved by the supplementation. Total blood buffering capacity was significantly increased from 77.69 +/- 6.79 to 80.16 +/- 5.24 mmol/L (mean +/- SEM, n = 82, p < 0.001) and also blood pH rose from 7.456 +/- 0.007 to 7.470 +/- 0.007 (mean +/- SEM, n = 75, p < 0.05). Only intracellular magnesium increased by 11% while other intracellular minerals were not significantly changed in sublingual tissue as measured with the EXA-test. Plasma concentrations of potassium, calcium, iron, copper, and zinc were within the normal range and not significantly influenced by the supplementation. Plasma magnesium was slightly reduced after the supplemenation (-3%, p < 0.05). The results show that a disturbed acid-base balance may contribute to the symptoms of low back pain. The simple and safe addition of an alkaline multimineral preparate was able to reduce the pain symptoms in these patients with chronic low back pain.

Mechanisms of Mg(2+) transport in cultured ruminal epithelial cells.

Net Mg(2+) absorption from the rumen is mainly mediated by a transcellular pathway, with the greater part (62%) being electrically silent. To investigate this component of Mg(2+) transport, experiments were performed with isolated ruminal epithelial cells (REC). Using the fluorescent indicators mag-fura 2, sodium-binding benzofuran isophthalate, and 2', 7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein, we measured the intracellular free Mg(2+) concentration ([Mg(2+)](i)), the intracellular Na(+) concentration ([Na(+)](i)), and the intracellular pH (pH(i)) of REC under basal conditions, after stimulation with butyrate and HCO(-)(3), and after changing the transmembrane chemical gradients for Mg(2+), H(+), and Na(+). REC had a mean resting pH(i) of 6.83 +/- 0.1, [Mg(2+)](i) was 0.56 +/- 0. 14 mM, and [Na(+)](i) was 18.95 +/- 3.9 mM. Exposure to both HCO(-)(3) and HCO(-)(3)/butyrate led to a stimulation of Mg(2+) influx that amounted to 27.7 +/- 5 and 29 +/- 10.6 microM/min, respectively, compared with 15 +/- 1 microM/min in control solution. The increase of [Mg(2+)](i) was dependent on extracellular Mg(2+) concentration ([Mg(2+)](e)). Regulation of pH(i) has been demonstrated to be Na(+) dependent and is performed, for the most part, by a Na(+)/H(+) exchanger. The recovery of pH(i) was fully blocked in nominally Na(+)-free media, even if [Mg(2+)](e) was stepwise increased from 0 to 7.5 mM. However, an increase of [Mg(2+)](i) was observed after reversing the transmembrane Na(+) gradient. This rise in [Mg(2+)](i) was pH independent, K(+) insensitive, dependent on [Mg(2+)](e), imipramine and quinidine sensitive, and accompanied by a decrease of [Na(+)](i). The results are consistent with the existence of a Na(+)/Mg(2+) exchanger in the cell membrane of REC. The coupling between butyrate, CO(2)/HCO(-)(3), and Mg(2+) transport may be mediated by another mechanism, perhaps by cotransport of Mg(2+) and HCO(-)(3).

Effects of magnesium deficiency on joint cartilage in immature beagle dogs: immunohistochemistry, electron microscopy, and mineral concentrations.

Quinolone-induced chondrotoxicity is possibly associated with the magnesium-chelating properties of quinolones. This toxic effect seems to be restricted to a rather short time period during postnatal development as shown in rats and dogs. We studied developmental changes of the integrin pattern on canine chondrocytes (e.g. the alpha(v)beta(3)- or alpha(5)beta(1)-integrin), because integrin function depends on divalent cations, as well as the matrix composition (e.g., collagen type II, fibronectin), in 11-, 18-, and 55-week-old Beagles (n=8) by immunohistochemistry. We also analyzed the magnesium and calcium content by atomic absorption spectroscopy in cartilage and bone and studied the effects of a magnesium-deficient diet on joint cartilage in four immature Beagles (18 weeks old at necropsy). The dogs were fed the magnesium-deficient diet for 40 to 46 days. All dogs exhibited gait alterations ('limping') after 4 weeks on the magnesium-deficient diet. Male, magnesium-deficient dogs exhibited pronounced weakness in their front legs; in one of these dogs the front legs were hyperextended to a 90 degrees angle. We observed no significant differences in the integrin pattern in samples from dogs at different developmental stages or in magnesium-deficient dogs in comparison to age-matched controls. Localization of fibronectin in the joint cartilage was found to vary with the age of the dogs as well as with the site of collection. In the middle zone of immature joint cartilage, corresponding to the predilective site of quinolone-induced cartilage lesions, we observed a slight increase in staining with the fibronectin antibody in some samples from magnesium-deficient dogs. Electron microscopy revealed alterations in chondrocytes from the magnesium-deficient dogs (e.g., swollen mitochondria and enlarged endoplasmic reticulum) which are also seen after treatment with quinolones. In summary, we found no significant differences of the integrin pattern on chondrocytes from joint cartilage of dogs at various developmental stages. However, magnesium deficiency in immature dogs induced similar clinical symptoms as quinolone treatment as well as distinct alterations in chondrocytic fibronectin staining and their ultrastructure. This corroborates our findings in rats where magnesium chelation is an important event in quinolone-induced chondrotoxicity.

Ultrastructure of Achilles tendons of rats treated with ofloxacin and fed a normal or magnesium-deficient diet.

Fluoroquinolones can cause tendinitis and tendon rupture. However, toxicological as well as clinical information on quinolone-induced tendopathy is scarce. We performed extensive electron microscopic studies with Achilles tendon specimens from ofloxacin-treated rats. The drug was given at a dose of 1,200 mg/kg (body weight) orally. Juvenile Wistar rats received one or three oral doses each of 1,200 mg of ofloxacin/kg (body weight)/day. Three days after treatment, the tenocytes of their Achilles tendons showed degenerative alterations, such as multiple vacuoles and vesicles in the cytoplasm that had developed due to swellings and dilatations of cell organelles. Other indications of cell degradation were the occurrence of cell debris and cell detachment from the extracellular matrix accompanied by a loss of cell-matrix interaction. The tenocytes of juvenile Wistar rats that had been treated at day 36 with a single oral dose of 1,200 mg of ofloxacin/kg (body weight) and sacrificed either 3 or 6 months later exhibited similar degenerative alterations. The number of degenerative alterations of tenocytes after ofloxacin treatment was considerably higher in rats that had received a magnesium-deficient diet than in rats with normal magnesium status. Of the adult rats that had been treated once, 5 times, and 10 times with ofloxacin and killed 1 day later, only those with the 10-times treatment showed a significantly increased number of degeneratively altered tenocytes. In summary, effects observed in tendons show similar pathological features as described earlier in cartilage, indicating that quinolone-induced arthropathy and quinolone-induced tendopathy probably are different clinical manifestations of the same toxic effect on cellular components of connective tissue structures.

[Diagnosing magnesium deficiency. Current recommendations of the Society for Magnesium Research]. / Diagnostikdes Magnesiummangels. Aktuelle Empfehlungen der Gesellschaft für Magnesium-forschung e. V.

The cardiovascular risk increases with decreasing serum levels of magnesium, and this already at concentrations within the previous reference range (0.70-1.10 mmol/L). For this reason, the Society for Magnesium Research has updated its 1986 recommendations for the diagnosis of magnesium deficiency. The diagnosis is based on the patient's history, his clinical symptoms, and the results of clinical-chemical investigations of plasma/serum and urine. Further diagnostic methods used include the determination of ionized serum magnesium and the magnesium retention test. The optimal serum magnesium concentration is > 0.80 mmol/L.

Effects of fluoroquinolones and magnesium deficiency in murine limb bud cultures.

Quinolone-induced arthropathy is probably caused by a lack of functionally available magnesium in immature joint cartilage. We used an in vitro assay to study the effects of fluoroquinolones on cartilage formation in mouse limb buds from 12-day-old mouse embryos in regular and in magnesium-deficient medium. Omission of magnesium from the medium had no adverse effect on the outcome of the culture: limb buds grew and differentiated well in regular and in magnesium-deficient Bigger's medium. Lack of calcium, however, severely impaired the development of the explants; this result was even more enhanced when both minerals (magnesium and calcium) were omitted. Electron microscopy revealed cell necrosis and deposition of electron-dense material in the vicinity of chondrocytes from limb buds after 6 days in a magnesium-free medium. A series of seven fluoroquinolones was tested at 30, 60, and 100 mg/l medium. At a concentration of 30 mg/l sparfloxacin only had a slight effect on limb development. At concentrations of 60 and 100 mg/l sparfloxacin, temafloxacin and ciprofloxacin impaired limb development in vitro concentration-dependently. The effects were enhanced in a magnesium-deficient medium (concentration of magnesium <10 micromol/l). Fleroxacin, lomefloxacin and ofloxacin impaired limb development only slightly; no significant differences were recognizable between the outcome in regular and in magnesium-deficient medium. Pefloxacin did not show any effect on limb development in both media. Using electron microscopy, very similar alterations as described above for the limbs cultured in magnesium-deficient medium were observed with ofloxacin at a concentration of 30 mg/l, which had no effect on the growth of the explants when evaluated macroscopically. The affinity of six fluoroquinolones to magnesium was determined by the use of a fluorescence assay. The affinity to magnesium correlated with the activity of the drugs in the limb bud assay. We conclude that fluoroquinolones have no effect on murine limb development in vitro at concentrations that are achieved under therapeutic conditions (peak concentrations approx. 1-5 mg/l in plasma). Effects at higher concentrations (60 and 100 mg/l) are slightly enhanced (factor 2) if the magnesium concentration in the medium is low. Macroscopically, limbs develop regularly in a magnesium-free medium, but ultrastructurally typical alterations are exhibited (e.g. cell necrosis and pericellular deposition of electron-dense material).

Pathobiochemical effects of graded magnesium deficiency in rats.

Severe Mg deficiency changed mineral homeostasis, induced membrane damage, increased lipid peroxidation and cytokine concentrations, and reduced immunocompetence. In order to investigate whether the pathobiochemical effects correlate directly with the degree of Mg deficiency or whether there might be a threshold with no detectable effects above, diets with 70, 110, 208, 330 and 850 ppm 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) in various tissues (liver, spleen, heart, kidney, muscle) and plasma parameters (Mg, Ca, Fe, alanine- and aspartate-aminotransferase) were measured. After 30 days 6-keto-prostaglandin F1 alpha, thromboxane B2, tumor necrosis factor-alpha, and immunoglobulins (IgG, IgM, IgA) were additionally analyzed. Tissue Mg content was either unchanged or only slightly reduced in severe Mg deficiency. Tissue Fe content rose when the extracellular Mg concentration was below 0.25 mM. There was a close positive correlation between tissue Fe and malondialdehyde content, and malondialdehyde was negatively correlated with vitamin E content. Below a threshold of about 0.25 mM plasma Mg concentration, transaminases increased in plasma. The same threshold could be observed for the increase of tissue Ca content, except in the kidney where calcifications were found already in mild Mg deficiency. Tumor necrosis factor-alpha and 6-keto-prostaglandin F1 alpha were increased when the plasma Mg concentration was below 0.15 mM, and thromboxane B2 was increased when plasma was lower than 0.25 mM. IgG and IgA were significantly reduced below 0.25 mM plasma Mg and IgM below 0.4 mM plasma Mg. Mild Mg deficiency, therefore, can be compensated and might not lead to pathological symptoms if not combined with other pathobiological conditions.

Effects of magnesium deficiency on magnesium and calcium content in bone and cartilage in developing rats in correlation to chondrotoxicity.

Quinolone-induced arthropathy has been described in juvenile rats between 3 and 6 weeks of age, but not in adult rats. The mechanism of this chondrotoxic effect is probably related to the Mg2+-chelating properties of the drugs, since identical cartilage lesions were observed in magnesium-deficient juvenile rats without quinolone treatment. However, the reasons for the phase-specificity of the effect are unknown. In the present study, we fed a magnesium-deficient diet to Wistar rats at different postnatal developmental stages. Cartilage lesions were only observed in magnesium-deficient rats between 3 and 5 weeks of age, but not in rats receiving the magnesium-deficient diet during weeks 5 to 8, weeks 8 to 11, or months 15 to 16. The formation of cartilage lesions was not related to the magnesium concentration in plasma, since magnesium concentrations in plasma were similarly reduced in rats with and without cartilage lesions. However, chondrotoxicity correlated with magnesium content in articular cartilage. In articular cartilage (articular and epiphyseal cartilage in immature rats) and bone, magnesium content was more reduced in rats receiving the magnesium-deficient diet between 3 and 5 weeks of age as compared with rats receiving the magnesium-deficient diet during weeks 8 to 11 postnatally. It was not possible to reduce the magnesium content in bone tissue of 15-month-old Wistar rats, which suggests a lower magnesium turnover in aged rats. Magnesium content in epiphyseal cartilage of 2-week-old rats (total femoral head) was 41.9 +/- 16.9 mmol/kg dry weight. The magnesium content in joint hyaline cartilage was significantly lower in 4-week-old rats (19.5 +/- 3.6 mmol/kg dry weight) and increased subsequently again to 48.5 +/- 9.2 mmol/kg dry weight (mean +/- SD; n = 8 to 16). Increase of the magnesium content in femoral bone between weeks 4 and 6 postnatally was less pronounced (139 +/- 10 and 175 +/- 15 mmol/kg dry weight, respectively). Taken together, these data show that in 4-week-old rats, magnesium concentration in joint hyaline cartilage is significantly lower than at other times during postnatal development. Only at this developmental stage can cartilage lesions be induced by feeding rats a magnesium-deficient diet. This period correlates well with the sensitive phase of immature rats toward the chondrotoxic action of quinolones.

In vitro evidence for a Donnan distribution of Mg2+ and Ca2+ by chondroitin sulphate in cartilage.

Fluoroquinolones are known for their ability to form chelate complexes with magnesium. Cartilage lesions observed in juvenile animals after quinolone treatment very probably are a consequence of the lack of functionally available magnesium. In cartilage, which contains high amounts of negatively charged proteoglycans, a Donnan distribution can be expected leading to an inhomogeneous distribution of ions (such as magnesium), which may support the toxic effects of magnesium deficiency or quinolone treatment of cartilage. We performed in vitro experiments using dialysis tubes to simulate the unequal distribution of proteoglycans in cartilage and measured the distribution of magnesium, calcium and ofloxacin. We found that the concentration of free magnesium is significantly reduced with the chondroitin sulphate-free solution due to a Donnan effect. For example, using a 3% chondroitin sulphate solution (outside the tubing) dialysed against a chondroitin sulphate-free solution (inside the tubing) the magnesium concentration decreased by 24% from 0.55 +/- 0.02 to 0.42 +/- 0.04 mmol/l inside the tubing during 48 h observation (P < 0.01). Under physiological conditions this unequal distribution of magnesium probably will be much more pronounced because chondroitin sulphate concentrations in cartilage are higher; nevertheless, magnesium concentration is sufficient for regular function of the tissue. During the sensitive phase of quinolone toxicity, magnesium in juvenile cartilage is lower than at other time points during postnatal development. Moreover, additional complexation by quinolones may further reduce the concentration of functionally available magnesium below the critical level.

Quinolone-induced arthropathy: exposure of magnesium-deficient aged rats or immature rats, mineral concentrations in target tissues and pharmacokinetics.

Quinolone treatment or magnesium deficiency induce identical cartilage lesions in juvenile rats and show additive arthropathogenic effects. It has been shown previously that neither condition is arthropathogenic in 8-week-old rats. Joint cartilage from aged individuals is rather prone to pathological alterations but information on prolonged quinolone treatment and/or dietarily induced magnesium deficiency in aged animals is not available. We treated magnesium-deficient (n = 9) aged Wistar rats (age 15 months) and age-matched controls with daily doses of 600 mg ofloxacin/kg body wt. by gastric intubation for 28 days. Further groups of magnesium-deficient and control rats (n = 9 and n = 10, respectively) received the vehicle only. Peak plasma concentrations of ofloxacin in adult rats were 20.5 +/- 5.6 mg/l (mean +/- SD) following treatment with a single dose of 600 mg/kg body wt. At the end of the experiment the degree of magnesium deficiency was most pronounced in plasma (Mg2+-def., 0.33 +/- 0.12 mmol/l; control, 0.97 +/- 0.08 mmol/l) and less pronounced in sternal cartilage (Mg2+-def., 10.8 +/- 3.6 mmol/kg dry wt; control, 13.3 +/- 2.8 mmol/kg dry wt), whereas the magnesium concentration in femoral bone remained unchanged (Mg2+-def., 201 +/- 13 mmol/kg dry wt; control, 204 +/- 11 mmol/kg dry wt). Histological investigation of the knee joints revealed no cartilage lesions following ofloxacin treatment, magnesium deficiency or a combination of both conditions. By contrast, cartilage lesions such as scars and erosions of the joint surface, chondrocyte clusters within acellular areas of the cartilage matrix and persisting clefts were detectable in knee joints from 7 of 10 adult rats (age 9 months) which had been treated with 4 x 600 mg fleroxacin/kg body wt. at 5 weeks of age. Mean plasma concentration of fleroxacin in juvenile rats was approx. 50 mg/l between 1.5 and 6 h after dosing and the drug was still detectable in plasma 48 h after dosing (0.4 +/- 0.1 mg/l). Our data indicate that joint cartilage in aged rats is not altered by a 4-week quinolone treatment, even during magnesium deficiency. Cartilage lesions in adult rats were only detectable if the animals had been treated during the sensitive phase at 5 weeks postnatally.

Fluid regulation during prolonged physical strain with water and food deprivation in healthy, trained men.

The aim of this study was to investigate fluidregulating mechanisms, with special regard to the role of plasma proteins in the control of plasma volume (PV), and the role of the superficial tissues as a water storage organ of the body during prolonged physical strain. 29 male subjects (mean age 22.2 +/- 2.8 years) were studied during a 5 day period of survival training with multifactorial strain including restricted water intake (11 H2O.day-1) and food intake (628 kJ.day-1) additionally to physical exercise and sleep deprivation (20 h within 5 days). Under field conditions the heart rate was monitored continuously, and body mass, body composition, thickness of the shell tissues, and blood parameters were measured at (T1), after 72 h (T2), after 120 h (T3) and in the recovery period after 48 h (T4) and 72 h (T5). The estimated energy expenditure was approximately 24,000 kJ.day-1. The mean decrease of body mass was 6.77 kg (9.5%) at T3 (p < 0.001), 0.95 kg (1.3%) at T4 (p < 0.05) and 0.68 kg (0.9%) at T5 (n.s.). A reduction of total body water of 3.8 1 was estimated at T3. Serum creatinine ([Cr]) was raised at T3 by 18.5% (p < 0.0001). No relationship was found between [Cr] and other parameters. The PV decreased by 3.7% (p < 0.0001) at T2, increased by 1.6% (p < 0.0001) at T3 and was not different to baseline at T4 (+0.2%; n.s.). Total protein concentration ([TP]) increased at T2 (11.7%; p < 0.0001) and T3 (2.6%; p < 0.01), and decreased (p < 0.0001) at T4 (8.2%) and T5 (5.7%). Plasma proteins shifted into the intravascular space at T2 and T3 and moved out of the intravascular space at T4 and T5. This gives support to the hypothesis that one of the counterregulatory mechanisms maintaining PV during prolonged exercise is provided by protein shifts from the extravascular into the intravascular space. Our data provide evidence that this mechanism assists PV homeostasis efficiently over a period of 120 h with multifactorial strain, even under conditions with a fluid loss of almost 8% of the total body water.

Comparative evaluation of ultrastructural changes in articular cartilage of ofloxacin-treated and magnesium-deficient immature rats.

Ultrastructural changes in immature articular cartilage were studied after treatment of 5-wk-old rats with ofloxacin-a fluoroquinolone-and in magnesium deficiency. Magnesium deficiency was induced by feeding a magnesium-deficient diet for 9 days; the condition was confirmed by measuring the concentrations of the mineral in plasma, bone, and cartilage samples of the animals by atomic absorption spectrophotometry. Oral administration of single doses of 600 or 1,200 mg ofloxacin/kg body weight and magnesium deficiency were sufficient to induce gross structural cartilage defects. Alterations observed on the ultrastructural level showed striking similarities in magnesium-deficient rats and in rats treated with single doses of 600 mg ofloxacin/kg body weight. Typical observations were (a) bundle-shaped, electron-dense aggregates on the surface and in the cytoplasm of chondrocytes, (b) detachment of the cell membrane from the matrix and necrotic chondrocytes, (c) reduction of the extracellular matrix, and (d) swelling of cell organelles such as mitochondria. These findings further substantiate the histological finding that quinolone treatment and a dietarily induced magnesium-deficiency induce indistinguishable pathological conditions in immature joint cartilage, and they suggest that quinolone-induced arthropathy is probably caused by a reduction of functionally available magnesium (ionized Mg2+) in cartilage (42). Furthermore, they provide a basis for aimed studies with human cartilage samples from quinolone-treated patients that might be available postmortally or after hip replacement surgery.

Iron-induced injury of rat testis.

Male Wistar rats were intraperitoneally injected twice with 0.4 mmol kg-1 FeSO4. One, 2 and 4 days after the second Fe injection, Fe and malondialdehyde (MDA) content in testis was measured, the morphology studied by light and electron microscopy and the number of spermatids counted. After Fe injection, Fe and MDA content had increased in parallel. Light microscopic inspection on days 1 and 2 after Fe injection revealed numerous necroses in the different cell types of the germ epithelium. Four days after Fe injection, fewer alterations were found. Electron microscopic investigations revealed that some spermatids contained up to three nuclei and at least three axonemes. In some sperm tails up to 11 axonemes were found. In some midpieces two or three complexes of axonemes, outer dense fibres and mitochondria were observed. In other midpieces axonemes were absent and replaced by granular and filamentous material. The number of spermatids was reduced 4 days after Fe treatment. The increase in the number of axonemes was similar to that seen in Mg and Zn deficiency, indicating that the increase in Fe content and oxygen free radicals is the major reason for the biochemical and morphological alterations in Mg and Zn deficiency.

Erythropoietin in 29 men during and after prolonged physical stress combined with food and fluid deprivation.

The study investigated the influence of prolonged physical stress during survival training with food and fluid deprivation on the serum concentrations of erythropoietin (EPO). A group of 29 male subjects [mean age 22.2 (SD 2.8) years, height 1.78 (SD 0.06) m, and body mass (m(b)) 73.5 (SD 8.6) kg] were studied for 5 days of multifactorial stress including restricted water intake (11 H2O. day(-1)) and food intake (628 kJ. day(-1)) combined with physical exercise (estimated energy expenditure approximately 24000 kJ.day(-1)) and sleep deprivation (20 h within 5 days). Blood samples were taken before (T1), after 72 h (T2) and 120 h (T3) of physical stress, and after 48 h, (T4) and 72 h (T5) of recovery. The samples were analysed for EPO, and concentrations of serum iron (Fe), haptoglobin (Hapto), transferrin (Trans), ferritin (Fer), haemoglobin (Hb) and packed cell volume (PCV). The m(b) had decreased by 6.77 kg at T3 (P <0.01) and 0.68 kg at T5. The EPO and Hapto decreased during the survival training (P <0.01) and increased during the recovery period (P <0.01). The Fe increased during the survival training (P <0.01) and remained above the control concentrations during recovery (P <0.01). The Hapto decreased during the survival training (P <0.01) and remained below control concentration at T4 and T5 (P <0.01). The Trans decreased continuously over the week (P <0.01). The Fer increased during the survival training (P <0.01) and returned to control concentration at T5. The Hb increased from T1 to T2 (P <0.01) and had decreased significantly at T5 (P <0.01). The PCV increased from T1 to T2 (P <0.01) and remained below control levels afterwards (P <0.01). From our study it was concluded that, in humans, prolonged physical stress with food and fluid deprivation induces a marked EPO decrease, which is followed by a rapid increase during recovery to restore the reduced O2 transport capacity.

Integrins on joint cartilage chondrocytes and alterations by ofloxacin or magnesium deficiency in immature rats.

Recently, we showed that magnesium deficiency induces lesions in knee joint cartilage from 5-week-old rats that are very similar to ofloxacin-induced cartilage defects. We concluded that quinolone-induced arthropathy is probably due to chelation of magnesium and thus a deficit in functionally available magnesium in joint cartilage (Stahlmann et al. 1995). As magnesium deficiency in joint cartilage could impair chondrocyte-matrix interaction which is mediated by cation-dependent integrin receptors of the beta 1-subfamily, we investigated integrin expression in joint cartilage from untreated, ofloxacin-treated and magnesium-deficient Wistar rats. With immunohistochemical methods using monoclonal and polyclonal antibodies, we showed that the integrin pattern in joint cartilage from rats corresponded largely to integrin expression described for human cartilage tissue: beta 1, alpha 1, alpha 3 and alpha v subunits and the alpha 5 beta 1 and alpha v beta 3 heterodimers were consistently expressed. Joint cartilage lesions were detected in ofloxacin-treated and magnesium-deficient rats. Lesions were more pronounced in the quinolone-treated group. Expression of several integrins was reduced in the vicinity of lesions after oral treatment with 2 x 600 mg ofloxacin/kg for 1 day. Gross-structural lesions (e.g., cleft formation, unmasked collagen fibres) in magnesium-deficient rats were very similar but changes in integrin expression were less pronounced. On the other hand, changes in cartilage matrix composition showed similar alterations in ofloxacin-treated and magnesium-deficient rats: fibronectin deposition in the cartilage matrix increased in both groups while glycosaminoglycan content decreased. In summary, similar defects occur in ofloxacin-treated and magnesium-deficient rats and with immunohistochemical methods subtle differences are demonstrable.

Lipid peroxidation and morphology of rat testis in magnesium deficiency.

Male Wistar rats were fed diets with different Mg content, ranging from 70 to 850 ppm Mg, for 30 days. After 0, 10, 20 and 30 days, some of the rats were sacrificed for measuring weight, lipid peroxidation, Fe, vitamin E, Na+, K+, Mg2+ and Ca2+ content of testes. After 30 days, the morphology of the testes was investigated by electron microscopy. Mg deficiency induced an increase in weight, Na+, Ca2+ and Fe content and a reduction of K+ and Mg2+ content. Vitamin E content was reduced and the content of malondialdehyde as an indicator of lipid peroxidation was increased. Mg deficiency induced morphological alterations in up to 40% of the spermatids in the 70 ppm Mg group, which consisted: 1) in injured stretching of spermatids; 2) in an irregular arrangement of coarse fibres with missing microtubulus complex (axoneme) and microtubulus sheath; 3) in the development of up to 4 bundles of outer fibrils in one spermatid. The increase of Fe content, lipid peroxidation and the onset of morphological alterations occurred already at a mild degree of Mg deficiency.

Buffering and activity coefficient of intracellular free magnesium concentration in human erythrocytes.

Human erythrocytes either untreated or Mg2+(-)loaded by means of A23187 in the presence of 3 or 12 mM MgCl2 were haemolysed by freezing and thawing. In the haemolysates the concentration of total Mg2+ (by atomic absorption spectrophotometry), free Mg2+ (by a Mg2+(-)sensitive electrode) and ATP were determined. The increase in the free Mg2+ concentration was also measured when titrating the haemolysates with MgCl2. The experiments yielded a total Mg2+ buffer capacity of 4.85mM with a Ka of 0.9 mM-1, indicating that 2,3 bisphosphoglycerate was the main Mg2+ buffer in haemolysates of erythrocytes which had been ATP-depleted during preparation. The activity coefficient of free Mg2+ in erythrocytes was the same as in the chloride-based calibration solutions.