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At least 847 records · Page 47Linked to original sources
PubMed2003

[Soil nitrogen mineralization and its prediction in winter wheat-summer maize rotation system].

The mineralization of soil nitrogen in winter wheat-summer maize growth season was studied with field experiment, and its prediction was made by interval leached aerial incubation combined with first-order dynamic model. The results showed that the amount of soil mineralized nitrogen had a large variation among years and crops. The soil nitrogen mineralization was lower in winter wheat growth season than in summer maize growth season, resulted in the yield increment of summer maize being not significant with increasing nitrogen fertilization rate. The amount of soil mineralized nitrogen occupied 31%-60% of the total nitrogen uptake by winter wheat and 62%-108% by summer maize. It was understandable why crop yield (especially summer maize) was not significantly response to applied nitrogen fertilizer. The amount of soil mineralized nitrogen decreased with increasing soil nitrogen supply. The mineralization was positive in normal nitrogen supply range(0-300 kg N.hm-2). The first order dynamic model could only predict the whole trend of mineralization in growth season, but could not reflect its variation in some growth stages. The role of the model was still important in view of the prediction of nitrogen mineralization before sowing.

Crops, Agricultural↗
PubMed2001

In situ net mineralization rates in a heterogeneous mixed deciduous forest receiving elevated n deposition.

In situ net mineralization was studied at 6 locations (E, Eb, Ec, F1, F2, F3) of a heterogeneous mixed deciduous forest ("De Gulkeputten") with oak (Quercus robur L., Quercus rubra) and birch (Betula pendula) as dominant species. Net nitrogen mineralization was determined by means of a sequential in situ incubation experiment using intact soil cores. For all incubations, the net mineralization rates of the organic (F+H) layer varied between -0.4 and 2.0 g N m(-2) month(-1), while the net nitrification rates varied between -0.6 and 0.7 g NO3- -N m(-2) month(-1). The net mineralization and nitrification rates of the mineral (0-30 cm) layer ranged from 4.5 g N m(-2) month(-1)to 8.8 g N m(-2) month(-1)and from -1.0 to 4.9 g NO3- -N m(-2) month(-1) respectively. In general, net mineralization rates increased from August 1998 to October 1998. Net mineralization rates were positively correlated with the gravimetrical moisture content and mineralization and nitrification rates were mutually positively correlated.

Betula↗
PubMedDate not supplied

Creatine monohydrate and resistance training increase bone mineral content and density in older men.

Our purpose was to determine the effects of creatine supplementation combined with resistance training on bone mineral content and density in older men. Twenty-nine older men (age 71 y) were randomized (double blind) to receive creatine (0.3 g/kg creatine for 5 d and 0.07 g/kg thereafter) or placebo while participating in resistance training (12 weeks). Bone mineral content and density were determined by dual energy X-ray absorptiometry before and after training. There was a time main effect for whole-body and leg bone mineral density (p < or = 0.05) with these measures increasing by approximately 0.5%, and 1%, respectively in the combined groups. There was a group by time interaction for arms bone mineral content, with the group receiving creatine increasing by 3.2% (p < 0.01) and the group receiving placebo decreasing by 1.0% (not significant). Changes in lean tissue mass of the arms correlated with changes in bone mineral content of the arms (r = 0.67; p < 0.01). Resistance training of 12 weeks increases bone mineral density in older men and creatine supplementation may provide an additional benefit for increasing regional bone mineral content. The increase in bone mineral content may be due to an enhanced muscle mass with creatine, with potentially greater tension on bone at sites of muscle attachment.

Absorptiometry, Photon↗
PubMed1979

[Respiratory tract diseases in coal miners. I. Pneumoconiosis].

In two mines, "A"--in Lower Silesia with low, inclined coal seam and lesser degree of output mechanization and "B"--in the Silesia-Dabrowa Basin with high coal seams and a great degree of output mechanization), work conditions were examined (dust concentration, chemical composition of dust, and microclimate) and medical examinations of underground miners were done. The examinations involved: mine "A"--2094 miners, mine "B"--1846 miners. The two examined populations were almost identical as regards age and length of employment. The number of miners working in bad conditions in the "A" mine was twice as great as that of miners working in bad conditions in the "B" mine. In dust collected on work--stands in the "A" mine the amount of copper, chromium and vanadium was 3 times that in the "B" mine and in the "A" mine approximately 40% more nickel was found in the dust than in the "B" mine. Average dust concentration on work stands was 10 times greater in the "B" mine than in the "A" mine. The rate of pneumoconiosis was on average 3.7% in both populations, in the "A" mine--6.2% and in the "B" mine--0.8%. In currently working miners no nodular changes, like PMF, were found. The rate of pneumoconiosis significantly varied with the length of employment. In 71.7% miners changes in EKG were found, in the "B" mine the number of those with changes being about 10% greater than in those in the "A" mine. In miners from the "A" mine, mostly changes in conduction (17.1%) were found; in the "B" mine these changes were twice less frequent.

Adult↗
PubMed1981

Developmental appearance of the vitamin K-dependent protein of bone during calcification. Analysis of mineralizing tissues in human, calf, and rat.

Several mineralizing tissues have been analyzed for the vitamin K-dependent protein of bone (BGP) in order to establish the temporal relationship between initial mineral deposition and the appearance of BGP. These studies demonstrate that the appearance of BGP in developing bone is not dependent on birth, as had been suggested in earlier studies of rat development, but rather on the prior deposition of bone mineral. In fetal human bone, the level of BGP (grams of BGP/mol of bone PO4) rises from 5% of the adult level at 10 weeks gestational age to the adult level at 15 weeks. Thus, adult levels of BGP are reached in human bone shortly after the initial appearance of mineral and long before birth. In adolescent rats, which have overall levels of BGP in bone near the adult level, the appearance of BGP at the ends of growing bones and in bone induced by implantation of demineralized bone matrix follows mineral deposition by approximately 2 weeks. The relative absence of BGP in initially deposited bone mineral and its subsequent appearance several days later may be causally related to the maturation of bone mineral to hydroxyapatite, a structure which binds BGP. The implications of the timing of BGP appearance in mineralizing tissues to its possible function in bone are discussed.

Adult↗
PubMed1980

Aspects of microprobe analysis of mineralized tissues.

Mineralizing tissues were the first biological specimens to be examined by the electron microprobe. The necessity for performing analyses at high spatial resolution has led to the increasing use of energy dispersive (ED) detectors in CTEMs/STEMs. Because the ED detector accepts x-rays from a large solid angle, it often detects a large extraneous x-ray contribution from the instrument. By carefully redesigning and remaking the specimen stage and its environment from aluminium, the instrumental contribution may be subtracted from spectra recorded on this specimens. Measurements of the apparent concentrations of Ca and P in araldite due to extraneous x-rays from other parts of the specimen, show that accurate quantitative analyses of Ca and P may be performed in unmineralized organic matrix such as osteoid, despite the proximity of fully mineralized tissue. Quantitative microprobe analyses have been performed on 1) intracellular mineral deposits, 2) osteoid, 3) mineralized matrix in trabecular bone from rachitic (R), vitamin D-treated (D) and normal (N) rats. The composition of the intracellular mineral deposits was similar in all 3 groups with mean Ca:P molar ratios = approximately 1.0. The Ca and P levels in osteoid from each group were sufficiently high that, assuming: a) that all of the Ca and P was in ionized form and b) that osteoid has a water content of 59% the calculated [Ca2+] x [HPO4(2-)] products were much greater than that required for spontaneous precipitation of mineral. In the D and N groups, the Ca and P concentrations in mineralized matrix increased with increasing distance into bone, but in the R group they remained constant. The Ca:P molar ratios of the mineralized matrix and of the serum were highest in the R group (bone: 1.85--1.87, serum: 5.76 +/- 1.05), intermediate in the D group (bone: 1.72--1.90, serum: 2.46 +/- 0.36) and lowest in the N group (bone: 1.68--1.80, serum: 1.25 +/- 0.17).

Bone Matrix↗
PubMed1995

Longitudinal assessment of bone mineral density in children with chronic asthma.

BACKGROUND: With the emphasis on asthma as a chronic inflammatory process, the management of moderate to severe asthma, even in the pediatric population, has shifted to the regular use of inhaled anti-inflammatory agents, including inhaled corticosteroids. Accompanying the use of these agents has been the precaution that long-term use may have subtle or potential side effects, including growth suppression or decreased bone mineral deposition. OBJECTIVE: We sought to study the effects of inhaled anti-inflammatory agents on bone mineral density accumulation in growing asthmatic children. Included in this report is the longitudinal acquisition of bone mineral density in children with moderate to severe asthma. METHODS: Bone mineral density in normal and asthmatic children was measured longitudinally by dual-energy absorptiometry. Bone densitometry was determined twice over a 7- to 16-month period in 21 asthmatic children and a 13- to 60-month period in 14 normals. These children with two longitudinal visits were compared with a group of 107 normal children who had a single bone mineral density measurement. RESULTS: Nineteen of 21 asthmatic children used regular inhaled corticosteroids during the interval visits. The majority of the asthmatic boys had bone mineral density measurements, at both visits, that were at a higher percentile than normal boys with two visits. Asthmatic girls had bone density measurements at percentiles not significantly different than normal girls with two visits. CONCLUSIONS: The advancement of bone mineral density in asthmatic children provides support for the safety of inhaled anti-inflammatory medications on bone mineral density in children with significant asthma.

Adolescent↗
PubMed1994

Bone mineral affection in asymptomatic adult patients with celiac disease.

OBJECTIVES: Osteopenia is a well-known complication of overt celiac disease, but whether such defective bone mineralization is present among asymptomatic or silent patients is not known. Our objectives were: 1) to examine bone mineralization of a group of asymptomatic celiac patients; 2) to compare these results with those of symptomatic patients. METHODS: Bone mineral density of the spine and total skeleton by dual energy x-ray absorptiometry and serum parameters of mineral metabolism of eight recently diagnosed asymptomatic patients with celiac disease were studied. Results were compared with those obtained in 20 untreated symptomatic celiacs, 14 patients treated with gluten-free diet for a mean time of 15 yr, and 153 healthy adult subjects, matched by sex and age. RESULTS: Four and five out of eight asymptomatic patients presented with reduced mineralization of the spine and the total skeleton, respectively (> 1 SD below normal values for sex and age). Two patients presented with severe osteopenia of the spine, and the other three presented with severe osteopenia of the whole skeleton (> 2 SD below mean normal values). Osteopenia at plane bone level (total skeleton) was significantly lower when compared to healthy controls (p < 0.02). Symptomatic untreated patients had significantly more severe deterioration of bone mineralization than did asymptomatics (p < 0.05) and treated patients (p < 0.05). No difference in bone mineral density was observed between treated patients and asymptomatic celiacs. Serum levels of calcium, alkaline phosphatase, 25-OH vitamin D, and parathormone did not show conclusive abnormalities. CONCLUSIONS: Our findings provide direct evidence that reduced bone mineralization occurs in asymptomatic celiac patients before any other symptom becomes evident. Only early diagnosis and treatment of celiac disease can avoid the deterioration of the bone structure observed in all clinical status of celiac disease.

Absorptiometry, Photon↗
PubMedDate not supplied

[The micro- and ultrastructural organization of mineralized cartilage in the human pubic symphysis].

Samples of the pubic symphysis of humans from 18 to 87 years of age were studied at the light- and ultramicroscopic levels. The structural organization of the mineralized cartilage were investigated in mutual relationship with the basophilic line of calcification and the subchondral bone. The front of mineralization of the public symphysis cartilage is formed by calcified capsules of chondrocytes, thick and thin bundles of mineralized collagen fibers, mineral granules in the interterritorial matrix of the cartilage. In humans aged from 20 to 29 years the front of mineralization of the pubic symphysis cartilage is intermittent, by 40-49 years the amount of gaps becomes less, at the age of 70-79 years the front of mineralization becomes intermittent again. In elderly and senile people mineral plates of complex configuration appear in the interterritorial matrix and chondrocyte capsules, by the age of 87 there appear thick highly mineralized bundles of collagen fibers.

Adolescent↗
PubMed1995

[Nutrition and bone mineral density in premenopausal women].

Environmental factors have an important role in osteoporosis. Diet and, in particular, nutrients like calcium, vitamin D or phosphorus were extensively studied as determinants of bone mineral density, but the results remain conflicting and there is no clear evidence for an independent effect of such factors in the bone density of premenopausal women. We studied 66 healthy premenopausal women (20-40 years-old) aiming to relate bone mineral density, as measured in three different sites (distal forearm, lumbar spine and femoral neck) using single X ray and dual energy X-ray absorptiometry, with nutritional intake as estimated by a semi-quantitative food frequency questionnaire. Demographic, anthropometric and other life style variables were also assessed. There was a significant correlation between distal forearm and femoral neck (r = 0.57) or lumbar spine (r = 0.45) bone mineral density. No significant effect of age was observed for distal forearm bone mineral density in these women. In a stepwise multiple linear regression model, evaluating the contribution of all the variables studied, only body mass index (p=0.038) and vitamin A ingestion (p = 0.020) had an independent contribution for the variation in distal forearm bone mineral density. Mean bone mineral density, assessed in the femoral neck (p = 0.003) or the lumbar spine (p = 0.056) was different across tertiles of alcohol ingestion, being higher in non-drinkers. However, among regular drinkers there was a significant positive correlation between alcohol ingestion and femoral neck bone mineral density (Spearman's r = 0.53, p = 0.015). This study shows that the effect of nutrition seems dependent on the anatomical site assessed and that there is a weak correlation between nutritional intake and the actual bone mineral density.

Adult↗
PubMed2005

Bone remodelling is not affected by consumption of a sodium-rich carbonated mineral water in healthy postmenopausal women.

This study was designed to investigate the possible effects of consuming Na-rich carbonated mineral water on bone remodelling and urinary mineral excretion in postmenopausal women. Women (n 18) included were amenorrhoeic (>1 year), healthy and not obese (BMI <30 kg/m2). No woman was taking oestrogen replacement therapy, mineral and vitamin supplements, phyto-oestrogens or medications known to affect bone and lipid metabolism. In two consecutive interventions that lasted 8 weeks each, women drank 1 litre of control mineral water daily and 1 litre of carbonated mineral water, rich in Na, HCO3- and Cl-, daily. Body weight and height were measured, BMI was calculated and blood pressure was measured. Blood samples were taken from fasting subjects and serum obtained to analyse the biochemical bone markers, procollagen I amino-terminal propeptide (PINP) and beta-carboxy-terminal telopeptide of collagen (beta-CTX). At the end of each period, 24 h urine samples were collected to determine Ca, Mg, P, Na+, K+, Cl-, urine excretion and urinary pH. No changes in body weight, BMI or blood pressure were observed during the experimental period. Ca excretion was lower after the intake of carbonated water than after intake of the control water (P=0.037) while P excretion was higher (P=0.015). Total urine, Na and Cl- excretion did not differ between the two periods but urinary pH was increased after the intake of carbonated mineral water. PINP and beta-CTX did not differ between the two periods. Daily consumption of 1 litre of Na-rich carbonated mineral water for 8 weeks does not affect bone remodelling in healthy postmenopausal women.

Anthropometry↗
PubMed2004

Mineral fiber problems and their management: UK 1890-1935.

BACKGROUND: The first intimation that mineral fibers other than asbestos were biologically active, is generally identified with reports of experimental studies by Stanton and Wrench, and Pott and Friedrichs, in the early 1970s. In 1890 however, man-made mineral fiber was recognized to present human health hazards; in 1912 experimental study confirmed asbestos to be fibrogenic, and by 1935 other mineral fibers came to notice as potential lung hazards. METHODS: Published and archival sources have been reviewed to trace the emergence between 1890 and 1935 of the awareness of the health hazards of various fibrous minerals, and the development of strategies for their control. RESULTS: By the early 1900s there was evidence that the asbestos substituted for the man-made mineral fiber insulation material employed to improve the thermal efficiency of steam powered engines, presented a serious health problem. In the early 1930s, other mineral fibers came to be suspected of causing pneumoconiosis. CONCLUSIONS: Containment, local exhaust ventilation and personal respiratory protection were instituted for the amelioration of asbestosis, but because of the limitations of what was perceived to be reasonably practicable on economic grounds, and what was feasible technologically, their benefits were severely limited. Initial and periodic medical examination were introduced as precautionary measures, based on hope rather than on experience. When in the early 1930s, the investigation of coal mine dust and siliceous dust, threw up the hypothesis that fibrous natural mineral dusts other than asbestos might be fibrogenic, this was ignored and no further investigations were pursued and no precautionary measures were set in train.

Air Pollutants, Occupational↗
PubMed1994

Matrix crystals in cytologic urine specimens: observations on their mineral composition by energy dispersive X-ray microanalysis and morphologic scanning electron microscopy.

Crystals consisting by light microscopy of organic matrix (matrix crystals) encountered in cytologic urine specimens of 8 patients were examined for mineral phase components by scanning electron microscopy with energy dispersive X-ray microanalysis (SEM-EDX) and by morphologic scanning electron microscopy (SEM) performed separately in four of the eight cases. Whenever possible (three cases) mineralized crystals present in these specimens were examined separately by SEM-EDX for comparison of mineral phase composition with that of the corresponding matrix forms. Although by SEM-EDX components of matrix, glass and slide preparation media interfere with the precise estimation of the mineral phase components, the results of this method supported by the SEM morphology suggest that crystals consisting of organic matrix include a mineral phase, the lattice structure of which provides them from the early stages of formation with the characteristic morphology of the fully mineralized forms. This also suggests that organic matrix plays a role in the nucleation of minerals during the formation of certain urinary crystals.

Adult↗
PubMed1996

The mechanism of beta-glycerophosphate action in mineralizing chick limb-bud mesenchymal cell cultures.

Differentiating chick limb-bud mesenchymal cells plated in micromass culture form a cartilage matrix that can be mineralized in the presence of 4 mM inorganic phosphate (Pi), and 1 mM calcium. Previous studies showed that when beta-glycerophosphate (beta GP) is used in place of Pi, the mineral crystals formed are larger and differ in distribution. The present study shows that the difference in distribution is not associated with alterations in cell proliferation, protein synthesis, or with collagen, proteoglycan core protein, or alkaline phosphatase gene expression. Cultures with 2.5, 5, and 10 mM beta GP did show different levels of alkaline phosphatase activity, and in the presence of low (0.3 mM) Ca had different Pi contents (4, 6 and 9 mM, respectively), indicating that the increase in CaxP product may in part be responsible for the altered pattern of mineralization. However, cultures with beta GP in which alkaline phosphatase activity was inhibited with levamisole still had an altered mineral distribution as revealed by Fourier transform-infrared (FT-IR) microspectroscopy. The presence of a casein kinase II-like activity in the mineralizing cultures, the ability of specific inhibitors of this enzyme to block mineralization, and the known ability of beta GP to block phosphoprotein phosphatase activity suggests that altered patterns of matrix protein phosphorylation may influence mineral deposition in these cultures.

Alkaline Phosphatase↗
PubMed2001

Mineralization of 2,4-D, mecoprop, isoproturon and terbuthylazine in a chalk aquifer.

The potential to mineralize 2,4-dichlorophenoxyacetic acid (2,4-D), mecoprop, isoproturon and terbuthylazine was studied in soil and aquifer chalk sampled at an agricultural field near Aalborg, Denmark. Laboratory microcosms were incubated for 258 days under aerobic conditions at 10 degrees C with soil and chalk from 0.15-4.45 m below the surface. The [ring-U-14C]-labeled herbicides were added to obtain a concentration of 6 micrograms kg-1 and mineralization was measured as evolved [14C]carbon dioxide. The herbicides were readily mineralized in soil from the plough layer, except for terbuthylazine, which was mineralized only to a limited extent. In the chalk, lag periods of at least 40 days were observed, and a maximum of 51%, 33% and 6% of the added 2,4-D, mecoprop and isoproturon, respectively, were recovered as [14C]carbon dioxide. Large variations in both rate and extent of mineralization were observed within replicates in chalk. No mineralization of terbuthylazine in chalk was observed. As a measure of the general metabolic activity towards aromatic compounds, [ring-U-14C]-benzoic acid was included. It was readily mineralized at all depths.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1995

In vitro biological effects of clay minerals advised as substitutes for asbestos.

We studied one sample of commercial sepiolite and two samples of commercial vermiculite--clay minerals proposed as replacements for asbestos--and tested in vitro their abilities to activate complement, to lyse erythrocytes, and to elicit the production of reactive oxygen species (ROS) with human polymorphonuclear leukocytes (PMN) or bovine alveolar macrophages (AM); their behavior was compared with that of asbestos fibers obtained from the Union International Contra Cancer (UICC) as reference standards, as well as with kaolinite and illite, main members of the clay mineral family. Since in short-term in vitro tests the biological activity of mineral particles seems especially related to the active sites on their surface, we first measured the specific surface area of each mineral. Sepiolite was unreactive in two of the three tests we used (complement activation and ROS production) and able to lyse a minimal percentage of red blood cells. Vermiculite was shown to be incapable of activating complement, to have a moderate hemolytic activity and a high ability to elicite ROS production, although lower than that of chrysotile. Sepiolite, therefore, might be of more interest than vermiculite, given the low level of biological effects detected during the tests used to compare both clay minerals with asbestos fibres. The ROS production does not seem to require phagocytosis. A high ROS production was observed with kaolinite: this result casts doubt on the ability of pathogenic mineral dusts in vitro to induce a greater release of ROS than nonpathogenic mineral dusts.

Acridines↗
PubMed1985

A possible energetic role of mineral surfaces in chemical evolution.

The postulated roles of clays and other minerals in chemical evolution and the origin of life are reconsidered in terms of the interaction of these minerals with penetrating sources of energy such as ionizing radiation and mechanical stress. This interaction, including such facets as excitation, degradation, storage, and transfer, is considered here with regard to its profound potential for altering the capabilities of minerals to serve both as substrates for prebiological chemistry and as inorganic prototypic life forms. The interaction of minerals and energy in relationship to surface chemistry is discussed in terms of the spectroscopic properties of minerals, the interaction of energy with condensed phases, some commonly accepted concepts of heterogeneous catalysis in the absence of electronic energy inputs, and some commonly accepted and novel means by which surface activity might be enhanced in the presence of energy inputs. An estimation is made of the potential contribution of two poorly characterized prebiotic energy sources, natural radioactive decay and triboelectric energy. These estimates place a conservative lower limit on their prebiotic abundance. Also some special properties of these energy sources, relative to solar energy, are pointed out which might give them particular suitability for driving reactions occurring under geological conditions. Skeletal support for this broadly defined framework of demonstrated and potential relationships between minerals, electronic excitation, and surface reactivity, as applied to chemical evolution, is provided from the results of our studies on 1/1 clays. We have discovered and partially characterized a number of novel luminescent properties of these clays, that indicate energy storage and transfer processes in clays. These luminescent properties are interpreted in relationship to the electron spin resonance phenomena, to provide a basis for estimating the potential significance of energy storage and transduction in monitoring or driving clay surface chemistry. Consideration of the electronic structure of abundant minerals in terms of band theory and localized defect centers provides a predictive theoretical framework from which to rationalize the capacity of these materials to store and transduce energy. The bulk crystal is seen as a collecting antenna for electronic energy, with the defect centers serving as storage sites. The clay properties produced by isomorphic substitution appear to be intimately associated with all of the life-mimetic chemical processes that have been attributed to clays.(ABSTRACT TRUNCATED AT 400 WORDS)

Chemical Phenomena↗
PubMed1988

Fine powdering exposes the mineral-protected collagen of bone to protease digestion.

The method of heat-denaturation and trypsin digestion was used to dissect bone biochemically into mineral-protected and mineral-unprotected pools of collagenous matrix. It was found that varying the particle size of the bone powder had a profound effect on the results. Using mature bovine cortical bone, the observed pool of "unmineralized" (mineral-unprotected) collagen could be varied from 2% to more than 60% of the total bone collagen simply by decreasing the particle size of the bone sample from greater than 1 mm to less than 38 micron. No major differences were seen in the contents of hydroxypyridinium cross-links between the collagens of the trypsin-soluble and trypsin-insoluble pools from the fine powders, contrary to earlier reports. A trend to a higher content of these cross-links was evident, however, in the very small collagen pool extracted from the coarsest bone particles. Similar extraction differences were noted using bacterial collagenase to probe for mineral-protected vs. mineral-unprotected domains of bone collagen. In summary, the biochemical dissection results appear largely to be an artifact of the powdering technique, the shear energies of which presumably destroy the intimate physical relationship between the mineral crystallites and the collagen fibrils at the fractured surfaces of the bone particles. As the fractured surface area increases with decreasing particle size so the fraction of protease degradable collagen increases. Since powdering is routinely adopted for many structural studies on both the mineral and organic phases of bone, the findings on finely powdered bone should be interpreted cautiously.

Animals↗