In osteomalacia decreased mineralization reduces the stiffness and static strength of bone. We hypothesized that hypomineralization in osteomalacic bone could be quantified by solidstate 31 Osteomalacia (rickets) is a disease characterized by hypomineralization of bone (1). Among the various causes of hypomineralization is a deficiency of vitamin D, calcium, and phosphorus resulting from inadequate nutrition, renal failure, or interference of certain drugs with calcium and vitamin D metabolism (2). Hypomineralization implies a reduced mineral mass per unit volume of bone tissue (also referred to as the degree of mineralization of bone (DMB) (3)). Both the stiffness and compressive strength of bone are largely determined by its mineral content, which in the normal skeleton is very tightly regulated. Currey (4) showed that even small variations in mineral content can have a disproportionately large influence on breaking strength, and noted that the latter decreased threefold for a decrease in ash content (mineral content) from 70% to 63%. Hypomineralization thus results in impaired mechanical competence of the skeleton and therefore increased fracture risk. Evaluation of the DMB requires knowledge about both bone mass and bone volume. The most common modalities used in the diagnosis of bone disease-dual-energy X-ray absorptiometry (DEXA) and X-ray computed tomography (CT)-cannot distinguish between osteoporosis (i.e., a reduced amount of normally mineralized bone) and osteomalacia (a normal amount of undermineralized bone) because these techniques measure only the apparent density as the amount of mineral mass per unit area (or volume, respectively) of tissue. While several destructive methods for measuring true mineral density (gravimetric analysis, microradiography, chemical analysis, etc.) are available, there is currently no noninvasive modality for measuring the DMB.Magnetic resonance imaging (MRI) offers a unique opportunity for noninvasive quantification of bone mineral whose major constituent is a poorly crystalline nonstoichiometric calcium phosphate similar in composition to low-crystalline hydroxyapatite, Ca 10 (OH) 2 (PO 4 ) 6 . The feasibility of imaging 31 P by solid-state MRI (SS-MRI) was recently demonstrated in bone specimens (5,6) as well as in vivo (7,8). However, there has been no demonstration so far that differences in mineralization density can be detected in bone disease. Quantification of phosphorus by MRI is complicated by the lower magnetic moment and unfavorable relaxation properties of the 31 P nucleus. The absence of rapid molecular motions in solids results in extremely short transverse relaxation times (8) and long spin-lattice relaxation times (9), both of which adversely affect the SNR.The purpose of the present work was to explore the feasibility of using 31 P solid-state MRI to quantify phosphorus with sufficient precision to distinguish between osteomalacic and normally mineralized bone in a rabbit model of osteomalacia. Toward this objective we designed and implemented a 3D ...

A detailed characterization of the main chain and side chain dynamics in R. capsulatus ferrocytochrome c(2) derived from (2)H NMR relaxation of methyl group resonances is presented. (15)N relaxation measurements confirm earlier results indicating that R. capsulatus ferrocytochrome c(2) exhibits minor rotational anisotropy in solution. The current study is focused on the use of deuterium relaxation in side chain methyl groups, which has been shown to provide a detailed and accurate measure of internal dynamics. Results obtained indicate that the side chains of ferrocytochrome c(2) exhibit a wide range of motional amplitudes, but are more rigid than generally found in the interior of nonprosthetic group bearing globular proteins. This unusual rigidity is ascribed to the interactions of the protein with the large heme prosthetic group. This observation has significant implications for the potential of the heme-protein interface to modulate the redox properties of the protein and also points to the need for great precision in the design and engineering of heme proteins.

This study was conducted to compare the differences of the uptake of Mn from Mn-lysine complex (MnLys) and MnSO and to determine the potential mechanisms of the uptake of Mn from MnLys. We first established the primary rat intestinal epithelial cell culture model and used it to determine the uptake of Mn from different Mn sources. The MnLys increased (p < 0.001) Mn uptake when compared to MnSO . The uptake of Mn decreased (p < 0.05) with added Fe concentration increasing in the medium regardless of Mn source. The MnLys decreased (p < 0.01) Mn efflux transporter ferroportin 1 (FPN1) mRNA level, but did not influence (p > 0.06) Mn influx transporter DMT1 mRNA expression when compared to MnSO . The results above indicated that the increase of Mn accumulation for MnLys at least partly was due to the decrease of Mn efflux by reduced FPN1 expression. The N-ethylmaleimide, as an l-lysine transport system y inhibitor, decreased (p < 0.001) the uptake of Mn from MnLys, but did not affect (p > 0.10) the uptake of Mn from MnSO . The cycloheximide, as an l-lysine transport system b activator, increased (p < 0.001) the uptake of Mn from MnLys, whereas also did not influence the uptake of Mn from MnSO . The MnLys increased (p < 0.01) the system y member cationic amino acid transporter (CAT) 1, and system b components rBAT and b AT mRNA expression when compared to MnSO . These results suggested that the uptake of Mn from MnLys complex might be transported by CAT1 and system b , which was different from ionized Mn uptake pathway. In conclusion, the uptake of MnLys complex not only might be absorbed as Mn , but also appeared to be transported through CAT1 and system b in the primary rat intestinal epithelial cells.

To investigate changes in BRCA1 following DNA damage, we exposed MCF-7 cells to increasing doses of ultraviolet C. We observed an increase in BRCA1 protein levels above 78 J/m2. This increase was observed as early as 5 min after irradiation. BRCA1 levels were then observed to decrease after 2 h, consistent with the previously published data. By pretreating with cycloheximide prior to irradiation, we observed a decrease in the protein half-life, from 3.5 h to 53 min, suggesting that a decrease in protein half-life may cause the lower levels of BRCA1 after irradiation. We also observed an increase in BRCA1 mRNA within 15 min of irradiation, followed by a decrease after 4 h. These data suggest that newly translated protein may contribute to increases in BRCA1 protein levels. The very rapid changes in BRCA1 support its role as a sensor of DNA damage, as opposed to being a repair gene.