Extracellular ATP and UTP stimulate cartilage proteoglycan and collagen accumulation in bovine articular chondrocyte pellet cultures.
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Bovine articular chondrocytes were maintained in high density pellet cultures with and without serum and nucleotide triphosphates for different periods of time. Despite half-lives in culture of about 3 h, adenosine triphosphate and uridine triphosphate in the presence of serum increased sulphated glycosaminoglycan and collagen deposition above control levels. In the presence of serum a single dose of uridine triphosphate on the first day of culture was sufficient to induce significant increases in subsequent proteoglycan and collagen deposition. We conclude that both adenine triphosphate and uridine triphosphate are anabolic for articular chondrocytes, and that this effect on the chondrocyte is long-term. (+info)
Comparison of acid mine drainage microbial communities in physically and geochemically distinct ecosystems.
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This study presents population analyses of microbial communities inhabiting a site of extreme acid mine drainage (AMD) production. The site is the inactive underground Richmond mine at Iron Mountain, Calif., where the weathering of a massive sulfide ore body (mostly pyrite) produces solutions with pHs of approximately 0.5 to approximately 1.0. Here we used a suite of oligonucleotide probes, designed from molecular data recently acquired from the site, to analyze a number of microbial environments by fluorescent in situ hybridization. Microbial-community analyses were correlated with geochemical and mineralogical data from those environments. The environments investigated were within the ore body and thus at the site of pyrite dissolution, as opposed to environments that occur downstream of the dissolution. Few organism types, as defined by the specificities of the oligonucleotide probes, dominated the microbial communities. The majority of the dominant organisms detected were newly discovered or organisms only recently associated with acid-leaching environments. "Ferroplasma" spp. were detected in many of the communities and were particularly dominant in environments of lowest pH and highest ionic strength. Leptospirillum spp. were also detected in many slime and pyrite-dominated environments. In samples of an unusual subaerial slime, a new uncultured Leptospirillum sp. dominated. Sulfobacillus spp. were detected as a prominent inhabitant in warmer ( approximately 43 degrees C) environments. The information gathered here is critical for determining organisms important to AMD production at Iron Mountain and for directing future studies of this process. The findings presented here also have relevance to the microbiology of industrial bioleaching and to the understanding of geochemical iron and sulfur cycles. (+info)
Deletion of supplemental minerals and vitamins during the late finishing period does not affect pig weight gain and feed intake.
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Two studies were conducted to determine the effects of eliminating the supplemental vitamin and minerals during the last 30 d of finishing on pig performance. The first study was conducted in a controlled university environment and the second under field conditions. Deletion of vitamin and mineral supplements for the last 30 d of finishing had no effects on pig performance or general health of pigs in either the university or the field trial. Besides lowering feed costs, deletion of dietary supplements may reduce the environmental impact of late finishing diets. (+info)
Eumetazoan fossils in terminal proterozoic phosphorites?
(52/1799)
Phosphatic sedimentary rocks preserve a record of early animal life different from and complementary to that provided by Ediacaran fossils in terminal Proterozoic sandstones and shales. Phosphorites of the Doushantuo Formation, South China, contain eggs, egg cases, and stereoblastulae that document animals of unspecified phylogenetic position; small fossils containing putative spicules may specifically record the presence of sponges. Microfossils recently interpreted as the preserved gastrulae of cnidarian and bilaterian metazoans can alternatively be interpreted as conventional algal cysts and/or egg cases modified by diagenetic processes known to have had a pervasive influence on Doushantuo phosphorites. Regardless of this interpretation, evidence for Doushantuo eumetazoans is provided by millimeter-scale tubes that display tabulation and apical budding characteristic of some Cnidaria, especially the extinct tabulates. Like some Ediacaran remains, these small, benthic, colonial fossils may represent stem-group eumetazoans or stem-group cnidarians that lived in the late Proterozoic ocean. (+info)
Multivitamin/mineral supplementation improves plasma B-vitamin status and homocysteine concentration in healthy older adults consuming a folate-fortified diet.
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Elevated homocysteine has been identified as an independent risk factor for cardiovascular and cerebrovascular disease. Although multivitamin use has been associated with low plasma homocysteine concentrations in several observational studies, no clinical trials have been conducted using multivitamin/mineral supplements to lower homocysteine. We determined whether a multivitamin/mineral supplement formulated at about 100% Daily Value will further lower homocysteine concentration and improve B-vitamin status in healthy older adults already consuming a diet fortified with folic acid. In this randomized, double-blind, placebo-controlled trial, 80 free-living men and women aged 50-87 y with total plasma homocysteine concentrations of > or =8 micromol/L received either a multivitamin/mineral supplement or placebo for 56 d while consuming their usual diet. After the 8-wk treatment, subjects taking the supplement had significantly higher B-vitamin status and lower homocysteine concentration than controls (P: < 0.01). Plasma folate, pyridoxal phosphate (PLP) and vitamin B-12 concentrations were increased 41.6, 36.5 and 13.8%, respectively, in the supplemented group, whereas no changes were observed in the placebo group. The mean homocysteine concentration decreased 9.6% in the supplemented group (P: < 0.001) and was unaffected in the placebo group. There were no significant changes in dietary intake during the intervention. Multivitamin/mineral supplementation can improve B-vitamin status and reduce plasma homocysteine concentration in older adults already consuming a folate-fortified diet. (+info)
The chemistry of enamel caries.
(54/1799)
The chemical changes which occur during the process of carious destruction of enamel are complex due to a number of factors. First, substituted hydroxyapatite, the main component of dental enamel, can behave in a very complex manner during dissolution. This is due not only to its ability to accept substituent ions but also to the wide range of calcium phosphate species which can form following dissolution. In addition, the composition, i.e., the extent of substitution, changes throughout enamel in the direction of carious attack, i.e., from surface to interior. Both surface and positively birefringent zones of the lesion clearly illustrate that carious destruction is not simple dissolution. Selective dissolution of soluble minerals occurs, and there is the probability of reprecipitation. The role of fluoride here is crucial in that not only does it protect enamel per se but also its presence in solution means that rather insoluble fluoridated species can form very easily, encouraging redeposition. The role of organic material clearly needs further investigation, but there is the real possibility of both inhibition of repair and facilitation of redeposition. For the future, delivering fluoride deep into the lesion would appear to offer the prospect of improved repair. This would entail a delivery vehicle which solved the problem of fluoride uptake by apatite at the tooth surface. Elucidation of the role of organic material may also reveal putative mechanisms for encouraging repair and/or protecting the enamel mineral. (+info)
Evaluation of biological and physical protection against nuclease degradation of clay-bound plasmid DNA.
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In order to determine the mechanisms involved in the persistence of extracellular DNA in soils and to monitor whether bacterial transformation could occur in such an environment, we developed artificial models composed of plasmid DNA adsorbed on clay particles. We determined that clay-bound DNA submitted to an increasing range of nuclease concentrations was physically protected. The protection mechanism was mainly related to the adsorption of the nuclease on the clay mineral. The biological potential of the resulting DNA was monitored by transforming the naturally competent proteobacterium Acinetobacter sp. strain BD413, allowing us to demonstrate that adsorbed DNA was only partially available for transformation. This part of the clay-bound DNA which was available for bacteria, was also accessible to nucleases, while the remaining fraction escaped both transformation and degradation. Finally, transformation efficiency was related to the perpetuation mechanism, with homologous recombination being less sensitive to nucleases than autonomous replication, which requires intact molecules. (+info)
Effects of prebiotics on mineral metabolism.
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Nondigestible oligosaccharides (NDOs) have been found to stimulate absorption of several minerals and to improve mineralization of bone. Hence, these substances are potential ingredients for "functional foods." In addition to a nutritional effect, functional foods have physiologic and psychological benefits that result in improved health or reduced risk of chronic disease. Most of the scientific evidence for the functional effects of NDOs is based on animal experiments in which NDOs increased the availability of calcium, magnesium, zinc, and iron. This stimulatory effect of some NDOs is assumed to be mainly due to their prebiotic character. A prebiotic is defined as a substrate or food ingredient that is nondigestible for the host but is fermented selectively by some of the intestinal microflora. Thus, it stimulates the growth and activity of bacteria with beneficial consequences for the host's health. Recently, these findings were confirmed in human studies for some NDOs. The effects seem to be specific for the type of carbohydrate and are likely related to the rate of fermentation by the intestinal flora and appear to depend on the ingested dose. Contradictory results of the effect of prebiotics in literature may be due to the experimental design because the effect of NDOs depends on the dose, the time of administration, the content of calcium in the diet, the part of the skeleton investigated, and the age of the subjects studied. (+info)