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This article discusses the importance of calcium balance in the bone response to exercise, particularly in preventing stress fractures in military populations, especially female recruits. The study used dual calcium isotope methodology to assess calcium kinetics in 21 healthy women during load carriage exercise or rest. The results showed that exercise increased total and fractional calcium absorption and improved calcium balance compared to rest. However, the study also highlighted the need for further research to understand calcium kinetics during exercise in different populations and modes of exercise, as well as the role of calcium intake and supplementation in the bone response to exercise. [Extracted from the article]

Two experiments were conducted to determine the requirement for standardized total tract digestible (STTD) Ca by 11- to 25-kg pigs based on growth performance, bone ash, or Ca and P retention and to determine the effect of dietary Ca on expression of genes related to Ca transport in the jejunum and kidneys. Six diets were formulated to contain 0.36% STTD P and 0.32, 0.40, 0.48, 0.56, 0.64, or 0.72% STTD Ca by including increasing quantities of calcium carbonate in the diets at the expense of cornstarch. Two additional diets contained 0.72% STTD Ca and 0.33% or 0.40% STTD P to determine if 0.36% STTD P had negative effects on the Ca requirement. The same batch of all diets was used in both experiments. In Exp. 1, 256 pigs (11.39 ± 1.21 kg initial BW) were randomly allotted to the 8 diets with 4 pigs per pen and 8 replicate pens per diet in a randomized complete block design. On the last day of the experiment, 1 pig from each pen was euthanized and the right femur and intestine and kidney samples were collected. Results indicated that ADG and G:F started to decline (linear and quadratic, P < 0.05) at 0.54 and 0.50% STTD Ca, respectively. In contrast, bone ash increased (quadratic, P < 0.05) as dietary Ca increased and reached a plateau indicating that the requirement for STTD Ca to maximize bone ash was 0.48%. Bone ash, but not ADG or G:F, increased (linear, P < 0.01) as STTD P increased in the diets. The mRNA expression of genes related to transcellular Ca transport decreased (linear, P < 0.01) in the jejunum and in kidneys (linear and quadratic, P < 0.01) as dietary Ca increased. In Exp. 2, 80 pigs (13.12 ± 1.79 kg initial BW) were placed in metabolism crates and randomly allotted to the 8 diets with 10 replicate pigs per diet in a randomized complete block design. Fecal and urine samples were collected using the marker-to-marker approach. Results indicated that the requirement for STTD Ca to maximize Ca and P retention (g/d) was 0.60 and 0.49%, respectively. In conclusion, the STTD Ca requirement by 11- to 25-kg pigs to maximize bone ash was 0.48%; however, ADG and G:F declined if more than 0.54 or 0.50% STTD Ca, respectively, was fed, and the minimum concentration of Ca needed to maximize ADG and G:F could not be determined under the conditions of this experiment. Increasing dietary Ca decreased the mRNA expression of several genes related to transcellular Ca transport in the jejunum and the kidneys. [ABSTRACT FROM AUTHOR]

Combination therapy can be used for the treatment of fungal infections, especially for those caused by antifungal-resistant fungi. In the present study, in vitro interactions and mechanisms between fluconazole and minocycline against Candida albicans were evaluated. The nature of the interactions determined by spectrophotometric method in a checkerboard assay was interpreted using nonparametric models of fractional inhibitory concentration index (FICI) and percentages of growth difference (Δ E). In the mechanism study, we evaluated the potential activity of minocycline on fluconazole penetrating the C. albicans biofilm. Furthermore, the effect of fluconazole and minocycline alone and in combination on the cellular calcium balance, as well as on the uptake and efflux of fluconazole were evaluated. It was found that fluconazole can work synergistically with minocycline against fluconazole-resistant C. albicans; the minimum inhibitory concentration of fluconazole decreased from 512 to 2 μg mL−1 when fluconazole and minocycline were given in combination, with an FICI of 0.035 and 0.064 and high-percentage synergistic interactions of 1250% and 988% for the two resistant strains. The mechanism of action was suggested to be the enhancement of minocycline on fluconazole penetrating biofilm, and inducing the intracellular calcium release, instead of impacting on the uptake and efflux of fluconazole. Our results suggest that the combination of fluconazole and minocycline can reduce the fluconazole resistance of C. albicans in vitro. [ABSTRACT FROM AUTHOR]

Background. During haemodialysis, calcium balance can affect, or be affected by, mineral metabolism. However, when dialysate calcium concentration (d[Ca]) is chosen or kinetic models are employed to calculate calcium balance, bone remodelling is rarely considered. In this study, we examined whether bone remodelling affects calcium mass transfer during haemodialysis. Methods. We dialysed 23 patients using a d[Ca] of 1.0, 1.25, 1.5 or 1.75 mmol/L. Calcium mass transfer was measured and associated with remodelling bone factors. Results. Calcium balance varied widely depending on the d[Ca]. Calcium removal was −578 ± 389, −468 ± 563, +46 ± 400 and +405 ± 413 mg when a d[Ca] of 1.0, 1.25, 1.5 or 1.75 mmol/L was used, respectively (1.0 and 1.25 vs 1.5 and 1.75 mmol/L, P < 0.001; 1.5 vs 1.75 mmol/L, P < 0.05). Univariate analysis showed that calcium balance correlated with calcium gradient, parathyroid hormone (PTH), osteocalcin and dialysis vintage. Multivariate analysis revealed that calcium balance was dependent on calcium gradient, PTH and osteocalcin. Conclusions. These results suggest that bone remodelling could affect calcium mass transfer during haemodialysis. [ABSTRACT FROM AUTHOR]

The debate on the most adequate dialysate calcium concentration for intermittent haemodialysis therapy is ongoing. There is probably no one optimal concentration. In general, one would like to maintain a neutral calcium balance in adult haemodialysis patients. However, a slightly negative balance may be preferable to avoid soft-tissue calcium accumulation in face of net calcium loss from the bone with ageing. The problem with measurements of calcium balance is that they are generally imprecise, as are estimations of total body calcium and its distribution in various compartments, unless done with labour-intensive methods and great care. The choice of the dialysate calcium will depend on several factors, including parathyroid and vitamin D status, type and severity of concomitant bone disease, presence or absence of arterial calcification, dietary habits, drug treatment and dialysis modality. Ideally the dialysate calcium would be adapted to each patient's needs. This is not feasible, however, in most dialysis settings and neither is it cost-effective. From a practical point of view, a relatively high dialysate calcium concentration in the range of of 1.50–1.75 mmol/L (3.0–3.5 mEq/L) should probably be preferred in haemodialysis patients with high serum PTH levels who are not prescribed calcium-based phosphate binders or high doses of active vitamin D sterols, and in those who are receiving a calcimimetic. In those who are treated with high doses of calcium-based binders and/or active vitamin D derivatives or who have a very low serum PTH level, the optimal dialysate calcium concentration is probably lower, in the range of 1.25–1.50 mmol/L (2.50–3.0 mEq/L). In the present pro/con debate about the optimal dialysate calcium concentration used for the haemodialysis session, we have accepted to defend the viewpoint that a low calcium concentration may do more harm than benefit in many patients. This viewpoint is opposite to that taken by Gotch [1]. He argues that since calcitriol and other active vitamin D derivatives have become available virtually all haemodialysis patients are in positive calcium balance. We would like to take issue with this statement and warn against the indiscriminate use of a low calcium dialysate in all patients receiving haemodialysis therapy. [ABSTRACT FROM PUBLISHER]

Five untreated osteoporotic patients were studied in a metabolic unit for 30 days while receiving control (0.8 gm/kg) and high (2.0 gm/kg) protein diets of purified proteins. The high protein diet increased urinary calcium and produced a negative calcium balance without causing significant change in calcium absorption, serum chemical values, or urinary sodium and potassium. Variable effects of calcium and/or estrogens were found on the negative balance. Hence, increased dietary protein acutely causes a negative calcium balance in osteoporotic patients and may contribute to bone loss in this disease. [ABSTRACT FROM PUBLISHER]

The choice of an appropriate dialysate calcium (Ca) concentration is crucial in the management of dialysis patients: an excessive Ca load has been associated with vascular calcifications, whereas Ca depletion can worsen secondary hyperparathyroidism (HPT) and decrease bone mass. In haemodialysis (HD), Ca transfer by diffusion depends on the concentration gradient between dialysate and blood, and a gain of Ca is expected when the dialysate Ca is >1.5 mmol/l. However, Ca losses by convective transport (ultrafiltration rate) can even exceed the amount of Ca gained by diffusion. Dialysis Ca balances, in normocalcaemic patients with a mean weight loss of 2–4 kg per session, have been shown to be positive, moderately negative or clearly negative using a dialysate Ca of 1.75, 1.50 or 1.25 mmol/l, respectively. Serum ionized Ca increases during sessions with a dialysate Ca of 1.5 and 1.75mmol/l, and decreases to the lower limits of normal after HD with 1.25 mmol/l. In haemodiafiltration (HDF), Ca mass transfer is strongly affected by the Ca content in the replacement solutions. Bicarbonate-containing bags are Ca free so that dialysate Ca needs to be increased above 1.75 mmol/l to overcome the convective losses and avoid markedly negative balances. Ca mass transfer in HDF is also affected by the infusion mode. Ca balance in post-dilution HDF, for a given concentration gradient between blood and dialysate, does not differ from HD. Conversely, in pre-dilution HDF, dialysate Ca concentration should be increased by ∼0.25 mmol/l to maintain comparable balances. A given dialysate Ca concentration should be prescribed considering the dialysis Ca mass balance, other concomitant therapies (Ca salts, vitamin D metabolites) and the type of bone disease. The current strategy of maintaining normal Ca levels by ensuring an adequate intestinal Ca absorption with large doses of Ca-containing phosphate binders and concomitantly avoiding positive Ca balances from dialysis by using a low Ca dialysate has been questioned recently because of the risk of either worsening HPT or accelerating the progression of vascular calcifications. A dialysate Ca of 1.5 mmol/l seems to be suitable for the majority of patients on HD or post-dilution on-line HDF because the moderately negative dialysis balances can be easily counterbalanced by the administration of mild doses of Ca-containing phosphate binders in order to ensure a neutral total body Ca balance. If necessary, aluminium-free and Ca-free binders can be added to achieve a satisfactory control of hyperphosphataemia, while avoiding an excessive Ca load. [ABSTRACT FROM PUBLISHER]