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Results for “Calcification, Physiologic”

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At least 685 records · Page 38Linked to original sources
PubMed2001

Calcium requirements during adolescence to maximize bone health.

The calcium requirements of boys and girls during adolescence have largely been based on balance studies, including more recently the use of stable nuclides. Bone measurements by dual energy X-ray absorptiometry (DXA) and similar instruments have provided an end-point by which to assess skeletal development, either of the entire skeleton or of specific bones, in relation to the consumption of calcium and other nutrients and to physical activity. Several cross-sectional studies, using measurements of bone mineral density (BMD) and bone mineral content (BMC), suggest that optimal calcium intakes for female adolescents may be somewhat lower than published as the Adequate Intakes (AIs) by the Institute of Medicine in 1997, but they may be somewhat higher for adolescent males. These results suggest that gender should be considered in establishing recommendations for calcium. In addition, other studies have provided evidence that prepubertal and postpubertal skeletal growth of males and females is enhanced by regular physical activities and that the optimal attainment of BMC and BMD by females by late adolescence may not be dependent on such a high calcium intake as previously thought, although males may need at least the recommended amount. Therefore, physical activity should also be considered in establishing recommendations for calcium. In summary, two lines of evidence suggest that more extensive information on diet and lifestyle should be considered in the future for making more specific recommendations on calcium intakes for optimal skeletal development for prepubertal and postpubertal boys and girls.

Adolescent↗
PubMed2003

Fetal femur length is influenced by maternal dairy intake in pregnant African American adolescents.

BACKGROUND: Pregnant adolescents may compete with their developing fetuses for the nutrients required for optimal bone mineralization. OBJECTIVE: The objective of this study was to determine the effect in pregnant African American adolescents of maternal dairy intake at entry into prenatal care on fetal femur development between 20 and 34 wk of gestation. DESIGN: A 10-y retrospective chart review was carried out in 1120 pregnant African American adolescents ( 3 servings/d), and a dose-response relation was suggested in the intermediate dairy-intake group (2-3 servings/d; P = 0.089). CONCLUSION: These data suggest that consumption of < 2 servings of dairy products/d by pregnant adolescents may negatively affect fetal bone development by limiting the amount of calcium provided to the fetus.

Adolescent↗
PubMed2003

Broiler nonphytin phosphorus requirement in the finisher and withdrawal phases of a commercial four-phase feeding system.

Two experiments were conducted to determine the nonphytin phosphorus (nPP) requirement for broilers, based on broken line analysis, in the finisher (32 to 42 d) and withdrawal phases (42 to 49 d) of a four-phase feeding program. The determined nPP concentrations used were 0.15, 0.19, 0.26, and 0.31% in the finisher phase, experiment 1 (Exp 1), and 0.10, 0.13, 0.22, and 0.27% in the withdrawal phase, experiment 2 (Exp 2). The analyzed calcium levels in the diets were 0.69 +/- 0.02% and 0.72 +/- 0.05% in Exp 1 and 2, respectively. In Exp 2, an additional treatment was included in which birds were fed NRC-recommended (1994) nPP levels from hatch to 49 d. There were no differences (P>0.05) among dietary treatments in weight gain, feed intake, and feed efficiency in either experiment. In Exp 1, tibia ash weight of birds fed the diets containing 0.15% nPP was lower (P<0.05) than that of birds fed diets containing 0.19, 0.26, or 0.31% nPP. A requirement of 0.20 +/- 0.01% nPP was determined for male broilers weighing between 1,541 to 2,194 g and from 32 to 42 d of age based on broken line analysis of tibia ash weight response to different dietary nPP levels. In Exp 2, the nPP requirement of male broilers weighing between 2,396 g at 42 d and 3,076 g at 49 d, based on tibia ash weight, was 0.16 +/- 0.02% nPP.

Animal Nutritional Physiological Phenomena↗
PubMed2002

Inhibition of nanobacteria by antimicrobial drugs as measured by a modified microdilution method.

Compounds from 16 classes of antimicrobial drugs were tested for their abilities to inhibit the in vitro multiplication of nanobacteria (NB), a newly discovered infectious agent found in human kidney stones and kidney cyst fluids from patients with polycystic kidney disease (PKD). Because NB form surface calcifications at physiologic levels of calcium and phosphate, they have been hypothesized to mediate the formation of tissue calcifications. We describe a modified microdilution inhibitory test that accommodates the unique growth conditions and long multiplication times of NB. This modified microdilution method included inoculation of 96-well plates and determination of inhibition by periodic measurement of the absorbance for 14 days in cell culture medium under cell culture conditions. Bactericidal or bacteriostatic drug effects were distinguished by subsequent subculture in drug-free media and monitoring for increasing absorbance. NB isolated from fetal bovine serum (FBS) were inhibited by tetracycline HCl, nitrofurantoin, trimethoprim, trimethoprim-sulfamethoxazole, and ampicillin at levels achievable in serum and urine; all drugs except ampicillin were cidal. Tetracycline also inhibited multiplication of isolates of NB from human kidney stones and kidney cyst fluids from patients with PKD. The other antibiotics tested against FBS-derived NB either had no effect or exhibited an inhibitory concentration above clinically achievable levels; the aminoglycosides and vancomycin were bacteriostatic. Antibiotic-induced morphological changes to NB were observed by electron microscopy. Bisphosphonates, aminocaproic acid, potassium citrate-citric acid solutions, and 5-fluorouracil also inhibited the multiplication of NB in a cidal manner. Insights into the nature of NB, the action(s) of these drugs, and the role of NB in calcifying diseases may be gained by exploiting this in vitro inhibition test system.

Anti-Bacterial Agents↗
PubMed2006

Diaphyseal bone formation in murine tibiae in response to knee loading.

Mechanical stimulation is critical for bone architecture and bone mass. The aim of this study was to examine the effects of mechanical loads applied to the knee. The specific question was whether loads applied to the tibial epiphysis would enhance bone formation in the tibial diaphysis. In C57/BL/6 mice, loads of 0.5 N were applied for 3 min per day for 3 days at 5, 10, or 15 Hz. Bone samples were harvested 13 days after the last loading. The strains were measured 13 +/- 2 microstrains at 5 Hz in the diaphysis. The histomorphometric data in the diaphysis clearly showed enhanced bone formation. First, compared with nonloaded control the cross-sectional cortical area was increased by 11% at 5 Hz and 8% at 10 Hz (both P < 0.05). Second, the cortical thickness was elevated by 12% at 5 Hz (P < 0.01) and 8% at 10 Hz (P < 0.05). Third, mineralizing surface (MS/BS), mineral apposition rate (MAR), and bone formation rate (BFR/BS) were increased at 5 Hz (P < 0.01 for MS/BS; P < 0.001 for MAR and BFR/BS) and at 10 Hz (P < 0.05 for MS/BS; P < 0.01 for MAR and BFR/BS). Bone formation was enhanced more extensively in the medial side than the lateral or the posterior side. The results reveal that knee loading is an effective means to enhance bone formation in the tibial diaphysis in a loading-frequency dependent manner without inducing significant in situ strain at the site of bone formation.

Adaptation, Physiological↗