Total Body Ca Research Articles

Metal uptake and acute toxicity in zebrafish: Common mechanisms across multiple metals

Zebrafish larvae ( Danio rerio) were used to examine the mechanisms of action and acute toxicities of metals. Larvae had similar physiological responses and sensitivities to waterborne metals as adults. While cadmium and zinc have previously been shown to reduce Ca 2+ uptake, copper and nickel also decreased Ca 2+ uptake, suggesting that the epithelial transport of all these metals is through Ca 2+ pathways. However, exposure to cadmium, copper or nickel for up to 48 h had little or no effect on total whole body Ca 2+ levels, indicating that the reduction of Ca 2+ uptake is not the acute toxic mechanism of these metals. Instead, mortalities were effectively related to whole body Na +, which decreased up to 39% after 48 h exposures to different metals around their respective 96 h LC50s. Decreases in whole body K + were also observed, although they were not as pronounced or frequent as Na + losses. None of the metals tested inhibited Na + uptake in zebrafish (Na + uptake was in fact increased with exposure) and the observed losses of Na +, K +, Ca 2+ and Mg 2+ were proportional to the ionic gradients between the plasma and water, indicating diffusive ion loss with metal exposure. This study has shown that there is a common pathway for metal uptake and a common mechanism of acute toxicity across groups of metals in zebrafish. The disruption of ion uptake accompanying metal exposure does not appear to be responsible for the acute toxicity of metals, as has been previously suggested, but rather the toxicity is instead due to total ion loss (predominantly Na +).

Mineral composition of two genetic lines of barrows and gilts from twenty to one hundred twenty-five kilograms of body weight1,2

Two genetic lines of barrows and gilt pigs with lean BW gain averages of 280 and 375 g/d were used to evaluate their macro- and micromineral contents at BW intervals from 20 to 125 kg of BW. The experiment was a 2 x 2 x 5 factorial arrangement of treatments (i.e., 2 sexes, 2 genetic lines, and 5 BW intervals) conducted in a completely randomized design in 6 replicates using a total of 120 pigs. Initially, 12 pigs (3 from each genetic line and sex) were killed, and then at approximately 25 kg of BW intervals to 125 kg. Pigs were fed vitamin and mineral fortified corn-soybean meal diets. At slaughter the total body (except digesta and blood) of each pig was ground and analyzed for their macro- and micromineral contents. The high-lean genetic line (P < 0.03) pigs and barrows (P < 0.01) reached their targeted BW an average 3 d earlier than the low-lean genetic line and gilts. Total macro- and micromineral contents increased as BW increased, generally in a linear or quadratic (P < 0.01) manner. There was an increasing difference between genetic lines in some minerals as BW increased. Total body Ca content was greater in the low-lean genetic line with increasing differences occurring as BW increased resulting in a BW x genetic line interaction (P < 0.05), whereas P was similar for both genetic lines. The quantity of K (P < 0.01) and S (P < 0.01) increased at a greater rate in the high-lean genetic line as BW increased, resulting in BW x genetic line interactions (P < 0.01). Body Cl (P < 0.01), Mg (P < 0.06), Mn (P < 0.05), Se (P < 0.01), and Zn (P < 0.01) were greater in the high-lean genetic. As BW increased, the Ca:P and the P:K ratios were increasingly greater (P < 0.01) in the low-lean genetic line, whereas the K:Na ratio was greater (P < 0.01) in high-lean genetic line. Although K and Fe were greater (P < 0.05) in gilts than in barrows, other mineral content differences were not significant. When minerals were expressed on a per kilogram of empty BW basis, the macro- and microminerals differed (P < 0.01) as BW increased indicating a response by body maturity. Genetic line had a greater effect on mineral content per kilogram of empty BW than sex. These results indicate that differences in mineral content are largely affected by BW or physiological age and by genetic line. Best-fitting equations were developed to determine macro- and micromineral contents of both genetic lines.

Abundant expression of SPARC, birc2 and boca mRNAs in goldfish scale

The existence of scales in teleost is related to the protective functions of the vertebrate integument and each scale is considered to be a counterpart of hair and/or nail. However, the scales can contain about 20% of the total body Ca so that they also appear to represent an internal Ca reservoir. Thus, in order to confirm whether scales are available for calcified tissue research or keratinized tissue research, characteristics of cells in the scale were examined by identifying differentially expressed genes. Subtraction cloning was subjected to scale ‐ gill (SG) and gill ‐ scale (GS). Six clones from SG and 4 from GS were isolated. Among them, SG1, SG2, and SG3 showed the high homology to SPARC, baculoviral IAP repeat containing 2 (birc2), and bcl2‐related ovarian killer a (boka), respectively. In situ hybridization confirmed birc2 and boca expression in flat cells along the ridge. Birc2 also expressed in large cells between the ridges. SPARC expressed in flat and small cells between the ridges. Although all the cells in the scale were designated as scleroblasts, there were several types of cells with different gene expression. Co‐expression of birc2 and boka along the ridge suggested that anti‐apoptotic mechanism worked to maintain the ridges. Since the cells did not always express SPARC, Ca homeostasis and/or osteocytic manifestation seemed to be maintained by the limited number of the cells.

Effects of Dietary Calcium Intervention on Adolescent Mothers and Newborns

To evaluate the effects of dietary calcium (Ca) intervention on adolescent pregnant mothers and their newborns. Seventy-two pregnant adolescent mothers were randomized into one of 3 groups: control, orange juice fortified with calcium, and dairy. The orange juice and dairy groups were required to take more than 1,200 mg Ca. Calcium tablets were added for those not able to meet required Ca. Maternal and infant weight, length, and blood pressure (BP) were recorded. Maternal dietary records were evaluated. Mother's blood was drawn for serum Ca, phosphate (P), magnesium (Mg), and vitamin 25-hydroxyvitamin D (D). Cord blood was collected for serum Ca and D. Newborn total body Ca was determined. All mothers were similar in weight, height, and BP. Mothers in the orange juice plus calcium and dairy groups had higher intakes of Ca (1,472 mg and 1,771 mg) than controls (862 mg). One half of the mothers in the orange juice plus calcium group required Ca tablets. Mothers in the dairy group had higher intakes of P, D, and Mg, higher serum folate and D, and higher cord D levels. Mothers in the orange juice plus calcium group had higher serum P but lower serum folate and D. Infants (3,517+/-273 g) in the dairy group were heavier than infants in the control (3,277+/-177 g) and orange juice plus calcium (3,292+/-165 g) groups. Infants in the dairy group had higher total body calcium than control infants. Calcium diet supplemented with dairy products during adolescent pregnancy resulted in higher maternal vitamin D and folate serum levels and higher newborn weight and bone mineralization compared with controls.

Effects of dietary calcium and cadmium on cadmium accumulation, calcium and cadmium uptake from the water, and their interactions in juvenile rainbow trout

The objective of this study was to examine the effects of chronically elevated dietary Ca 2+ (as CaCO 3), alone and in combination with elevated dietary Cd, on survival, growth, and Cd and Ca 2+ accumulation in several internal compartments in juvenile rainbow trout ( Oncorhynchus mykiss). In addition, effects on short-term branchial uptake and internal distribution of newly accumulated waterborne Ca 2+ and Cd during acute waterborne Cd exposure (50 μg/L as CdNO 3 for 3 h) were monitored using radiotracers ( 45Ca, 65Cd). Fish were fed with four diets: 20 mg Ca 2+/g food (control), 50 mg Ca 2+/g food, 300 μg Cd/g food, and 50 mg Ca 2+/g + 300 μg Cd/g food for 30 days. There were no significant effects on growth, mortality, or total body Ca 2+ accumulation. The presence of elevated Ca 2+, Cd, or Ca 2+ + Cd in the diet all reduced waterborne Ca 2+ uptake in a short-term experiment (3 h), though the inhibitory mechanisms appeared to differ. The effects were marked after 15 days of feeding, but attenuated by 30 days, except when the diet was elevated in both Ca 2+ and Cd. The presence of elevated Ca 2+ in the diet had only modest influence on Cd uptake from the water during acute Cd challenges but greatly depressed Cd uptake from the diet and accumulation in most internal tissues. None of the treatment diets prevented the decreases in waterborne Ca 2+ uptake and new Ca 2+ accumulation in internal tissues caused by acute exposure to waterborne Cd. In conclusion, there are complex interactions between waterborne and dietary effects of Ca 2+ and Cd. Elevated dietary Ca 2+ protects against both dietary and waterborne Cd uptake, whereas both waterborne and dietary Cd elevations cause reduced waterborne Ca 2+ uptake.

The choice of the dialysate calcium concentration in the management of patients on haemodialysis and haemodiafiltration.

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 approximately 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.

Effects of low calcium concentrations on two common freshwater crustaceans, Gammarus lacustris and Astacus astacus

Summary 1. Field studies indicate that low Ca concentrations limit the distribution and success of Ca‐demanding freshwater crustaceans in soft‐water localities. A long‐lasting depletion of Ca caused by reversed acidification could thus be detrimental to such species. 2. Experimental studies of Gammarus lacustris and Astacus astacus revealed decreased survival and retarded growth at ambient Ca concentrations &lt;5 mg l−1, compared with animals reared at 10 mg l−1. 3. A significant proportion of the total body Ca content was lost during the moult, but moulting frequencies were not affected by ambient Ca concentration. Complete postmoult calcification of the carapace could not be achieved at ambient Ca concentrations &lt;5 mg l−1, and individuals reared at such conditions had a lower specific Ca content than individuals reared at sufficient Ca levels. 4. A juvenile bottleneck regarding the susceptibility to Ca deficiency was shown in G. lacustris, as neonates had a relatively higher mass‐specific Ca content and a higher Ca threshold for survival than adults. 5. Because of a short postmoult calcification period of less than 2 days, G. lacustris had limited ability to compensate for low water Ca levels by obtaining Ca from food. However, food might be an important source of Ca for A. astacus living at low ambient Ca, because eating could be resumed during the relatively long calcification period (&gt;15 days).

Calcium intake, calcium bioavailability and bone health.

Calcium accounts for 1-2 % of adult human body weight. Over 99 % of total body Ca is found in the teeth and bones. Therefore, in addition to the obvious structural role of the skeleton, it also serves as a reservoir for Ca. Dietary Ca intake has an important impact on bone metabolism and bone health. Chronic Ca deficiency resulting from inadequate intake or poor intestinal absorption is one of several important causes of reduced bone mass and osteoporosis. It is vital, therefore, that adequate dietary Ca is consumed at all stages of life - in early life so that the genetically programmed peak bone mass can be reached and in later adulthood so that the skeletal mass can be maintained and age-related bone loss minimised. Unfortunately, there is wide variation in the estimates of daily Ca requirements made by different expert authorities. Furthermore, there is evidence that many individuals are not consuming these recommended levels. The consequence of this for bone health will be discussed in the present review. Besides the amount of Ca in the diet, the absorption of dietary Ca in foods is also a critical factor in determining the availability of Ca for bone development and maintenance. Thus, there is a need to identify food components and/or functional food ingredients that may positively influence Ca absorption in order to ensure that Ca bioavailability from foods can be optimised. This approach may be of particular value in individuals who fail to achieve the dietary recommended level of Ca.

Calcium intake, calcium bioavailability and bone health

Calcium accounts for 1–2 % of adult human body weight. Over 99 % of total body Ca is found in the teeth and bones. Therefore, in addition to the obvious structural role of the skeleton, it also serves as a reservoir for Ca. Dietary Ca intake has an important impact on bone metabolism and bone health. Chronic Ca deficiency resulting from inadequate intake or poor intestinal absorption is one of several important causes of reduced bone mass and osteoporosis. It is vital, therefore, that adequate dietary Ca is consumed at all stages of life — in early life so that the genetically programmed peak bone mass can be reached and in later adulthood so that the skeletal mass can be maintained and age-related bone loss minimised. Unfortunately, there is wide variation in the estimates of daily Ca requirements made by different expert authorities. Furthermore, there is evidence that many individuals are not consuming these recommended levels. The consequence of this for bone health will be discussed in the present review. Besides the amount of Ca in the diet, the absorption of dietary Ca in foods is also a critical factor in determining the availability of Ca for bone development and maintenance. Thus, there is a need to identify food components and/or functional food ingredients that may positively influence Ca absorption in order to ensure that Ca bioavailability from foods can be optimised. This approach may be of particular value in individuals who fail to achieve the dietary recommended level of Ca.

Calcium balance in embryos and larvae of the freshwater-adapted teleost, Oreochromis mossambicus

Changes in Ca(2+) content and flux, and the development of skin chloride cells in embryos and larvae of tilapia, Oreochromis mossambicus, were studied. Tilapia embryos hatched within 96h at an ambient temperature of 26-28°C. Total body Ca(2+) content was maintained at a constant level, about 4-8 nmol per individual, during embryonic development. However, a rapid increase in body Ca(2+) level was observed after hatching, 12.8 to 575.3 nmol per individual from day 1 to day 10 after hatching. A significant influx and efflux of Ca(2+) occurred during development, with the average influx rate for Ca(2+) increasing from 5.9 pmol mg(-1) h(-1) at 48h postfertilization to 47.8 pmol mg(-1) h(-1) at 1 day posthatching. The skin was proposed as the main site for Ca(2+) influx before the development of gills, and the increased Ca(2+) influx may be ascribed to gradual differentiation of skin surface and chloride cells during embryonic development. Ca(2+) efflux was 16-56 pmol mg(-1) h(-1) in 1-day-old larvae. The resulting net influx of Ca(2+), 10-12 pmol mg(-1) h(-1), accounted for the increased Ca(2+) content after hatching. When comparing the measured and estimated ratios of efflux and influx, active transport was suggested to be involved in the uptake of Ca(2+). Chloride cells, which may be responsible for the active uptake of Ca(2+), started to differentiate in the skin of embryos 48h after fertilization, and the density of chloride cells increased following the development. A possibility of active transport for Ca(2+) in early developmental stages of tilapia is suggested.

The effect of ambient Ph on electrolyte regulation during the postmoult period in freshwater crayfish Procambarus clarkii

ABSTRACT The effects of ambient pH on postmoult net fluxes of Ca, acidic/basic equivalents (H+, NH4+/OH−, HCO3−), Na and Cl−, total body Ca, haemolymph pH and electrolyte status were assessed in the freshwater crayfish Procambarus clarkii (Girard). Variables were monitored for 5 days postmoult in acidic (pH5.2; H2SO4) or alkaline (pH9.2; KOH) artificial tap water (ATW) and compared with those in control (pH7.4) tap water. In control ATW there was an initial net influx of Ca (+2700 μmolkg−1 h−1) and titratable basic equivalents (+5000 μmolkg−1 h−1) that declined with time. Calcium uptake accounted for 40% of total body Ca (0.49mmol g−1); haemolymph Ca concentration remained constant. Haemolymph pH was initially relatively alkalotic (7.7) but recovered within 24h. A 20% haemolymph dilution by water uptake at ecdysis necessitated uptake of Cl− and Na for the first 2–3 days postmoult (+1000 μmolkg−1 h−). In acidic ATW, Ca and basic equivalent uptake were both 60% reduced during the first 3–4 days and total body Ca was reduced by 37%. Chloride and Na uptake and haemolymph [Cl−] were decreased. In alkaline ATW, Ca and basic equivalent uptake were elevated by 30% for the first 2 days and haemolymph alkalosis was maintained. Sodium and Cl−balance were unaffected. Thus, ambient pH affects Ca and basic equivalent fluxes associated with postmoult calcification. Regulation of Na and Cl−levels is also impaired in acidic ATW.

Multi-geometry241AmBe neutron irradiator: Design and calibration for total-body neutron activation analysis

Neutron activation analysis provides an accurate elemental assessment of body compositional compartments; the analytical technique identifies skeletal, muscle, protein, and fat masses. Our irradiator system uses 56241AmBe sources (4.4·107 n/s each) which can be arranged in four basic geometries to examine body sizes from a preterm infant (500 g, 30 cm) to a very large adult (120 kg, 2m). Both in vivo and human cadaver studies have been performed. Precisions of 1 to 2% for total body Ca, P, Na, and Cl have been obtained.

Estrogens and progestogens conserve bone in rats deficient in calcitonin and parathyroid hormone

To examine the abilities of estrogens and progestogens to slow bone resorption and conserve bone in ovariectomized rats deficient in calcitonin (CT) or parathyroid hormone (PTH), nine groups of animals with 45Ca-labeled bones were studied for 12 wk. Rats were thyroidectomized (TX), parathyroidectomized (PTX), or given sham neck operations (Sham) and treated orally with either estrogen, 300 micrograms 17 beta-estradiol.kg body wt-1.wk-1; progestogen, 500 micrograms norethisterone acetate.kg body wt-1.wk-1; or placebo (Plac). The TX rats had parathyroid autografts and thyroxine replacement. In all surgical groups, estradiol (E2) and norethindrone (Nor) slowed urinary 45Ca excretion and conserved bone (P less than 0.001). However E2 lowered urinary hydroxyproline more than Nor. Total body Ca values (mg +/- SD) were Sham + Plac, 3,079 +/- 201; Sham + E2, 3,886 +/- 335; Sham + Nor, 3,567 +/- 459; TX + Plac, 3,123 +/- 159; TX + E2, 3,869 +/- 235; TX + Nor, 3,540 +/- 422; PTX + Sham, 3,067 +/- 249; PTX + E2, 3,775 +/- 414; PTX + Nor, 3,635 +/- 467. Importantly, E2 and Nor conserved bone as effectively in TX and PTX groups as in Sham rats, although the PTX rats had slower bone resorption and lower plasma 1,25-dihydroxyvitamin D values (P less than 0.001) than groups with intact parathyroids. We conclude that the effects of estrogens and progestogens to slow bone resorption and conserve bone are independent of CT and PTH. These findings appear relevant to the pathogenesis and treatment of postmenopausal osteoporosis.

Effect of physical activity on calcium and phosphorus metabolism in the rat

Changes in skeletal mass, nutritional calcium and phosphorus balance, and intestinal calcium absorption were studied in four groups of rats: control, exercise allowing free access to food, exercise with pair-feeding to control levels, and immobilization. The exercise regimen consisted of treadmill running 25 m/min, 60 min/day, 5 days/wk for 13 wk; rats were immobilized by bilateral sciatic denervation. The total body Ca (TBCa) was measured by neutron activation analysis as an index of skeletal mass. Standard metabolic balance techniques were used to determine calcium and phosphorus balance, and an in situ duodenal loop ligation preparation was used to study the active and passive intestinal Ca transport processes. Exercise promoted a positive Ca and P balance and increased the skeletal mass, largely as a result of an increase in 1,25-dihydroxyvitamin D and an enhancement of the intestinal Ca absorption efficiency. Urinary excretion of Ca and P did not differ from control levels and food intake was not a factor because pair-fed rats responded to exercise almost identically to those fed ad libitum. Conversely, immobilization caused a decrease in TBCa and a lower Ca and P balance. These effects are the result of an increased urinary mineral excretion, greater endogenous fecal excretion, and decreased mineral absorption efficiency in the intestine.

Specific Effects of Weight Loss, Protein Deficiency and Energy Deprivation on the Water and Electrolyte Composition of Young Rats

Specific effects of weight loss, protein deficiency and energy deprivation on the water and electrolyte content of the body were studied. Longitudinal changes in total body Na and Cl were measured by neutron activation analysis in young rats fed either a low protein diet (LP) ad libitum or a control diet in restricted amounts (ER). Total body Ca was determined to monitor growth of skeletal mass. Four balance periods were defined to represent various stages of protein or energy deprivation. The chemical composition of the rats was determined at the end of the study and compared with that of rats killed at the start of the study. Changes in body composition of LP rats were attributable chiefly to wasting of body cell mass. There was no retention of Na and Cl until severe hypoalbuminernia and edema developed after chronic protein deprivation; at this time, Na and Cl were retained in the same proportion as their molar ratio in extracellular fluid (ECF). The resulting increase in ECF volume accounted for the high total body water values in LP rats. Energy restriction to approximately 80% of maintenance requirements for 20 d resulted in Na retention in a compartment distinct from either the Cl or Ca space. With prolonged ER, there was preferential wasting of cell mass and adipose tissue but relative preservation of the ECF compartment; there was no net retention of Na and Cl, and hydration of fat-free mass was normal. The differences in the body compositions of ER and LP rats suggested that protein and energy deprivation can have separate effects on Na and Cl homeostasis that are distinct from changes induced by a loss of cell mass.

Calcitonin may modulate placental transfer of calcium in ewes.

In pregnant ewes bearing twin fetuses and fed an adequate Ca diet, the consequences of calcitonin (CT) deficiency (induced by thyroidectomy performed on day 30 of gestation, associated with daily thyroxine supplementation) differed according to the time of pregnancy. Such a deficiency had no significant effect either on fetal total body Ca content or on placental transfer of Ca in 77-day-old fetuses. On the contrary, CT deficiency for 110 days (on day 140 of pregnancy) was associated with an increased Ca concentration in fetal total body and increased placental transfer of Ca from the dam to its fetus, which did not occur in five thyroidectomized ewes supplemented with thyroxine and CT. This indicates that CT might protect the skeleton of the pregnant female against excessive demineralization by modulating placental transfer of Ca, when such a transfer become important, during periods of intense mineralization of the fetal skeleton.

Urinary loss of calcium in an anuran amphibian ( Bufo marinus) with a note on the effects of calcemic hormones

1. 1. Fasting toads, Bufo marinus, kept in freshwater, excreted 0.23% of their total body Ca each day in the urine. 2. 2. The mean concentration of Ca in the urine was 0.15 mmol/1 (range 0.04 to 0.62). 3. 3. Plasma: urine Ca concentration ratios as high as 60:1 were observed. 4. 4. Injected vitamin D 3 produced a hypercalcemia, and, in some toads, a hypercalciuria. 5. 5. Injected salmon calcitonin and bovine parathyroid hormone had no demonstratable effect on plasma or urine Ca. 6. 6. The results are discussed in relation to the special physiological problems of the Amphibia and the phyletic distribution of the effects of calcemic hormones.

Bone matrix and mineral abnormalities in postmenopausal osteoporosis

Iliac crest biopsies from 56 postmenopausal osteoporotic females with spontaneous compression fractures and decreased total body Ca were compared to similar tissue from 48 normal controls. Biopsies were analyzed for bone density, Na, Ca, Mg, P, CO 3, and hydroxyproline (OH-P). From the results OH-P/matrix, % mineral, and the ion content of the mineral were calculated. Osteoporotic subjects showed decreased bone density, % mineral in bone, and OH-P in the bone matrix. Within the mineral, CO 3 and Ca P were decreased, while Na and Mg were increased. Statistical analysis showed that matrix OH-P and % mineral varied independently, and therefore the patients were separated into 4 subgroups: Group Ia: decreased matrix OH-P with normal % mineral ( n = 9), Group Ib: decreased matrix OH-P with decreased % mineral ( n = 5), Group IIa: normal matrix OH-P with normal % mineral ( n = 33), Group IIb: normal matrix OH-P with decreased % mineral ( n = 9). Decreased % mineral was associated with decreased bone density and an increase in Na and Mg in the mineral, which suggests skeletal Ca deficiency. Decreased matrix OH-P was associated with decreased bone density and, in the low % mineral group, with decreased mineral CO 3 and Ca P , suggesting a mineral of decreased mean crystal size. When both abnormalities coexisted (Group Ib), the greatest reduction in total body Ca was seen. Patients with normal matrix and normal % mineral (Group IIa) still had decreased bone density. The results suggest that in a large, clinically homogeneous population of postmenopausal osteoporotic women, 4 subgroups can be identified by differences in chemical composition of iliac crest biopsies.

A role for skin in Ca metabolism of frogs?

1. 1. In the leopard frog, Rana pipiens, in vivo Ca loss occurs in similar amounts across the skin and the urine. No change was detected in Ca loss when frogs were injected with either calcitonin or parathyroid hormone. Large doses of 1,25-(OH) 2vitamin D 3 increased urinary Ca loss. 2. 2. 45Ca accumulation across the skin in vivo each day is equivalent to 0.04% of total body Ca or 14% of the total Ca in the extracellular fluids. This accumulation was enhanced by prior adaptation of the frogs to a low Ca pond water. 3. 3. Unidirectional influx (from 0.2 mM Ca on pond side) was remarkably similar in vitro: 0.56 and in vivo: 0.65 nmol cm −2 h −1. Based on in vitro measurements, an active transport process does not appear to be involved in this transcutaneous Ca movement. 4. 4. Substantial deposits of Ca equivalent to five times the total in other “soft” tissues and eleven times that in the total extracellular fluids are found in R. pipiens skin. 5. 5. Although cutaneous Ca does “turnover” slowly as shown by exchange with external 45Ca. the skin Ca concentration does not change with the environmental Ca concentration. 6. 6. Possible role(s) of cutaneous Ca in frogs' overall Ca metabolism are discussed.

47Ca turnover in endemic fluorosis and endemic genu valgum

1. Calcium turnover was determined after intravenous injection of radioactive 47Ca in patients with fluorosis and endemic genu valgum and in age-matched controls. Total Ca turnover in the body, loss of Ca from the body in urine, faeces and sweat (external turnover) and bone mineralization rate were calculated from whole-body retention of 47Ca and specific activity of 47Ca in serum. 2. Total Ca turnover was significantly higher in younger subjects than in older subjects. 3. Total Ca turnover was significantly higher in patients with fluorosis and in those with endemic genu valgum than in age-matched controls, but the external turnover of Ca was lower in both groups of patients than in controls. 4. Bone mineralization rate was significantly higher in patients with fluorosis and in those with genu valgum as compared to age-matched controls. 5. Total body Ca turnover and bone mineralization rates were significantly higher in patients with endemic genu valgum than in those with fluorosis. The differences persited even after adjusting for differences in age between patients with fluorosis and those with genu valgum.