MoViES: molecular vibrations evaluation server for analysis of fluctuational dynamics of proteins and nucleic acids

Analysis of vibrational motions and thermal fluctuational dynamics is a widely used approach for studying structural, dynamic and functional properties of proteins and nucleic acids. Development of a freely accessible web server for computation of vibrational and thermal fluctuational dynamics of biomolecules is thus useful for facilitating the relevant studies. We have developed a computer program for computing vibrational normal modes and thermal fluctuational properties of proteins and nucleic acids and applied it in several studies. In our program, vibrational normal modes are computed by using modified AMBER molecular mechanics force fields, and thermal fluctuational properties are computed by means of a self-consistent harmonic approximation method. A web version of our program, MoViES (Molecular Vibrations Evaluation Server), was set up to facilitate the use of our program to study vibrational dynamics of proteins and nucleic acids. This software was tested on selected proteins, which show that the computed normal modes and thermal fluctuational bond disruption probabilities are consistent with experimental findings and other normal mode computations. MoViES can be accessed at http://ang.cz3.nus.edu.sg/cgi-bin/prog/norm.pl.

TRMP: a database of therapeutically relevant multiple pathways

Disease processes often involve crosstalks between proteins in different pathways. Different proteins have been used as separate therapeutic targets for the same disease. Synergetic targeting of multiple targets has been explored in combination therapy of a number of diseases. Potential harmful interactions of multiple targeting have also been closely studied. To facilitate mechanistic study of drug actions and a more comprehensive understanding the relationship between different targets of the same disease, it is useful to develop a database of known therapeutically relevant multiple pathways (TRMPs). Information about non-target proteins and natural small molecules involved in these pathways also provides useful hint for searching new therapeutic targets and facilitate the understanding of how therapeutic targets interact with other molecules in performing specific tasks. The TRMPs database is designed to provide information about such multiple pathways along with related therapeutic targets, corresponding drugs/ligands, targeted disease conditions, constituent individual pathways, structural and functional information about each protein in the pathways. Cross links to other databases are also introduced to facilitate the access of information about individual pathways and proteins.

AVAILABILITY

This database can be accessed at http://bidd.nus.edu.sg/group/trmp/trmp.asp and it currently contains 11 entries of multiple pathways, 97 entries of individual pathways, 120 targets covering 72 disease conditions together with 120 sets of drugs directed at each of these targets. Each entry can be retrieved through multiple methods including multiple pathway name, individual pathway name and disease name.

SUPPLEMENTARY INFORMATION

http://bidd.nus.edu.sg/group/trmp/sm.pdf

Modulated angle beam ultrasonic spectroscopy for evaluation of imperfect interfaces and adhesive bonds

An experimental method incorporating high frequency pulsed angle beam ultrasonic measurements modulated by low frequency vibrations of a bonded structure is described. This method uses parametric/nonlinear mixing between high and low frequencies to characterize adhesive degradation. It is demonstrated that good quality (undamaged) bonds exhibit little dependence of ultrasonic signature on the overlay of low frequency vibration loads; however, environmentally degraded or imperfect bonds exhibit strong modulation of the resonance frequency of the ultrasonic signal reflected from the bond. The results are interpreted using a model for normal and oblique wave interaction with two nonlinear interfaces separated by an adhesive layer under quasi-static stress modulation.

Inverse ultrasonic determination of imperfect interfaces and bulk properties of a layer between two solids

A method for determination of the complete set of physical, geometrical, and interfacial properties of an isotropic layer embedded between two known solids is discussed. These properties are: Lamé elastic moduli, density and thickness of the layer, and complex normal and transverse interfacial stiffnesses between the layer and the substrates. The properties are combined in the form of eight nondimensional parameters, which are determined from experimental reflection spectra at two incident angles: normal and oblique. The conditions for simultaneous determination of bulk layer properties and the interface normal and transverse springs with losses and the stability of the inversion method against data scatter are addressed. The inversion model is validated by experiment on normal and angular ultrasonic reflectivity from a layer between two semispaces in dry mechanical contact and from an environmentally degraded adhesive joint. The layer properties were measured independently, showing good agreement with the reconstructed results.

Secondary sulphonylurea failure: what pathogenesis is responsible?

Sulphonylurea (SU) stimulates insulin secretion by pancreatic beta-cells and is generally used as a first-line treatment for type 2 diabetes. However, after long-term SU treatment (six months or over), some patients begin to show an increase in blood glucose once again (secondary SU failure). Two theories have been put forward to explain this failure--dysfunction of the proinsulin conversion machinery or insulin resistance. However, the primary pathogenesis behind secondary SU failure still needs to be investigated. Using a reliable technique that specifically identifies intact proinsulin (IPI), total proinsulin (TPI) and specific insulin (SI), this study aims to discover if a defect in the proinsulin converting mechanism plays a role in SU failure. Three groups were recruited for this study: healthy controls (n=8), SU responders (n=38) and secondary SU failures (n= 46). Serum concentrations of insulin-related molecules released in response to a standard glucose challenge test were compared between the groups. It was found that total SI was lower in the patient groups (P<0.05 compared to the control group), while TPI and IPI showed no distinct difference between the three groups (P>0.05). TPI:SI ratio and IPI:SI ratio showed marked increases in the patient groups (P<0.05 compared to control group), with no obvious quantitative difference between SU responders and secondary SU failures (P>0.05). Similar results for the Homa Insulin Resistant Index were found between the two patient groups. Interestingly, blood glucose at 180 mins after glucose challenge was significantly higher in the secondary SU failure group (P<0.05), with no correlation to SI, while the SU responder group showed good correlation between the parameters (P<0.05). We conclude that type 2 diabetes is associated with obvious dysfunction in the proinsulin-converting process and shows severe SI deficiency in responding to glucose challenge. Dysfunction of the proinsulin conversion mechanism was not an extra cause responsible for SU failure.

Establishment of a highly efficient transformation system for pepper (Capsicum annuum L.)

Application of modern genetic manipulation has been limited in pepper ( Capsicum annuum L.) due to the lack of an efficient transformation system. Following the development of an efficient protocol for in vitro regeneration of pepper cotyledons, we investigated the key factors affecting transformation and established a highly efficient genetic transformation system using the pepper cotyledon as starting material. In this system, cotyledon explants are preconditioned for 2 days on kanamycin (km)-free DM1 medium [Murashige and Skoog (MS) salts/Gamborg B5 vitamins basal medium supplemented with 20 g/l sucrose, 5,000 mg/l DJ nutrients and a hormone combination of 1.0 mg/l indoleacetic acid (IAA) and 5.0 mg/l 6-benzyladenine (BA) solidified with 0.7% agar, pH 5.8], followed by co-cultivation with Agrobacterium tumefaciens on DM1 for 2 days and delay selection on DM1 with 500 mg/l carbenicillin (carb) for 2 days. The explants are then placed on DM1 containing 10 mg/l AgNO(3), 50 mg/l km-sulfate and 500 mg/l carb. After 4-5 weeks, the explants with buds are transferred to EM1 medium (MS salts/Gamborg B5 vitamins basal medium supplemented with 20 g/l sucrose, 5,000 mg/l DJ nutrients, 10 mg/l AgNO(3) and a hormone combination of 1.0 mg/l IAA, 3.0 mg/l BA and 2.0 mg/l gibberellic acid, solidified with 0.7% agar, pH 5.8) with 50 mg/l kanamycin and 500 mg/l carbenicillin for the elongation of buds. After 3-6 weeks, 1- to 2-cm-long elongated shoots are excised and planted on RM1 medium (MS basal medium supplemented with a hormone combination of 0.2 mg/l NAA and 0.1 mg/l IAA, solidified with 0.8% agar, pH 5.8) with 25 mg/l km and 200 mg/l carb for rooting. We tested four genotypes of pepper, and all presented a high differentiation efficiency (81.3% on average), elongation rate (61.5%) and rooting efficiency (89.5%). Polymerase chain reaction analysis results showed that 40.8% of the regenerated plantlets were transgenic plants.

Bone mass and density response to a 12-month trial of calcium and vitamin D supplement in preadolescent girls

BACKGROUND

Maximal bone acquisition in adolescent girls through dietary and lifestyle practices is advocated to prevent or minimize the development of osteoporosis and its associated complications in later life. Longitudinal investigations of bone acquisition in children and adolescents have utilized areal bone mineral density (BMD, mg/cm(2)) as a measure of bone mass and strength. Peripheral quantitative computed tomography (pQCT), which provides a three-dimensional display of data, separate analyses of bone compartments, and bone mass in terms of volumetric BMD (vBMD, mg/cm(3)), has recently been introduced for clinical use.

OBJECTIVE

To assess the impact of a 12-month daily calcium supplement on total and trabecular bone acquisition as measured by pQCT in preadolescent girls.

DESIGN

Early adolescent Caucasian girls (aged 12 years, Tanner Stage 2) were enrolled in a randomized trial of daily calcium supplement (TX, 800 mg calcium carbonate and 400 IU vitamin D) or placebo (C). Body weight, height, and distal tibia measurements by pQCT were obtained at enrollment, 6 and 12 months. Pubertal status and physical activity records were assessed at baseline and 12 months. Three-day food intake records were completed every three months.

RESULTS

Seventy-one girls completed the 12-month trial (TX=35, C=36). No differences were found for age, weight, height, body mass index, pubertal maturation, or reported physical activity at enrollment or during the study. Average intakes during the study were 1524 mg calcium and 496 IU vitamin D (TX) versus 865 mg calcium and 160 IU vitamin D (C) per day. Baseline total bone values were similar, however, trabecular values were greater in TX girls despite randomization. Percent changes were calculated to adjust for baseline differences. Because of the small cortical thickness at the 10% site (mean values < 1.6 mm), cortical mass and density were not analyzed. The percent changes for trabecular bone mineral content (BMC, mg) and vBMD were significantly greater in TX girls (+4.1% BMC and +1.0% vBMD TX versus -1.6% BMC and -2.0% vBMD C, p<0.006; ANCOVA) after 12 months of supplement. Trabecular bone area (BA, cm(2)) and total bone change, however, did not differ between groups.

CONCLUSIONS

Daily calcium and vitamin D supplementation promotes greater trabecular BMC and vBMD acquisition in preadolescent girls. The single site selected for pQCT evaluation in this study did not allow evaluation of the cortical bone compartment. Future studies that utilize the pQCT technique need to incorporate multiple measurement sites to better assess total, cortical, and trabecular bone.

Determination of embedded layer properties using adaptive time-frequency domain analysis

A general model for determination of the complete set of acoustical and geometrical properties of an isotropic layer embedded between isotropic or anisotropic multilayered solids is developed. These properties include density, longitudinal and shear elastic moduli, layer thickness, and loss factors, simultaneously determined from two measurements, one at normal and one at oblique incidence. The inversion model is an extension of the method proposed by Lavrentyev and Rokhlin [J. Acoust. Soc. Am. 102, 3467 (1997)] which is applicable to thick substrates. In this new method, the inversion model mimics an experiment by using the same time-domain gating of the signal reflected from the embedded layer. This allows application of this method to layered solids when reflections from different layers overlap in the time domain. The sensitivity of the method, its stability against data scatter, and the effect of the oblique incident angle are evaluated. The effect of plane-wave approximation versus beam approximation in the inverse algorithm is discussed. Experimental results are given to demonstrate examples of adhesive layer property reconstruction.

The role of androgens in mammary carcinogenesis

Despite extensive research, the precise mechanism of mammary carcinogenesis is unknown. We have developed an animal model in which a high incidence of mammary cancer can be induced within a period of several months using a combination of testosterone (T) and 17beta-estradiol (E2) without the addition of carcinogens. The induced mammary tumours mimic closely the human breast cancer in terms of histopathology. Our results showed that the two sex hormones work synergistically to induce a higher incidence of mammary cancer than either hormone treatment alone. The dosage of T affects only the latency period of mammary cancer but not the final incidence. The results further showed that treatment of T, either alone or in combination with E2, there was overexpression of the androgen receptor (AR) in alveolar or ductal epithelial cells but not in stromal cells. Together with overexpression of AR in epithelial cells, there was an increase in perialveolar and interlobular connective tissue as well as a decrease in surrounding adipose tissue, despite the absence of AR in stromal cells. There was also an increase in proliferation rate of fibroblast-like cells in stroma. These changes were blocked by implantation of flutamide, an antiandrogen, indicating that androgens play a crucial role in the process. These findings highlight that the effect of androgens on the stroma, may be through a paracrine action of epithelial cells. The changes in the stroma may, in turn, promote mammary carcinogeneis in a reciprocal manner.

[The studies on microtensile bond strength measurements of two dentin adhesives]

OBJECTIVE

The purpose of this study was to investigate the feasibility of a modified microtensile method used to test bond strengths of two current one-bottle dentin bond systems (Prime & Bond NT, PBNT; Prime one Mirage, P-One) with a parallel match design.

METHODS

15 extracted, caries-free human molars were cut to expose occlusal dentin. A 5 mm deep slot was prepared in each crown to divide the crown into nearly equal halves for accepting treatment of the two dentin bond systems, respectively. After 24 h storage in distilled water at 37 degrees C, the bonded teeth were subjected to two treatments: 5 teeth were tested without further treatment and 10 teeth were thermocycled (2400 cycles, between 5 degrees C and 55 degrees C) prior to bond strength testing. Hour-glass shaped specimens with a distance of approximately 1.0 mm at the narrowest portion were cut from each tooth and tested in tensile mode.

RESULTS

Bond strengths (mean MPa) were: for PBNT: 42 & 31, and for P-One 64 & 38 without and with thermocycling, respectively. Two-way ANOVA revealed a significant difference in bond strengths(P < 0.001) between the two systems and when thermocycled. However, a pairwise multiple comparison (Tukey test) showed that after thermocycling the difference between the two systems was not significant (P > 0.05). Regression analysis showed that a correlation existed between the two systems' tensile bond strength values grouped by tooth (correlation coefficient r = 0.575, P < 0.05).

CONCLUSION

The modified microtensile method with a parallel match design is feasible and suitable for evaluating two different bonding systems or dentin treatments.

Diet-gene interactions in estrogen-induced mammary carcinogenesis in the ACI rat

It is well accepted that hormonal, dietary and genetic factors each influence breast cancer risk. However, the underlying mechanisms and the extent to which these factors interact are largely unknown. We have demonstrated that the female ACI rat exhibits a unique genetically conferred propensity to develop mammary cancers when treated with physiological levels of 17beta-estradiol (E2). More recently, we have mapped to rat chromosome 5 a strong genetic modifier of susceptibility to E2-induced mammary cancers, termed estrogen-induced mammary cancer 1 (Emca1), and have identified potential Emca1 candidate genes. Because estrogens have been inextricably linked to the genesis of breast cancer in humans, the ACI rat model has the potential to reveal novel physiologically relevant insights into how the contributory actions of E2 are modified by specific dietary factors. In the present study, we have examined the ability of a 40% restriction of dietary energy consumption to inhibit E2-induced mammary carcinogenesis. The hypothesis tested was that energy restriction will inhibit mammary carcinogenesis even when circulating E2 remains elevated through administration of exogenous hormone. The data presented herein strongly suggest that energy restriction inhibits E2-induced mammary carcinogenesis in the ACI rat at least partly by retarding progression of atypical hyperplastic foci to carcinoma.

[Anatomy structures of nasal cavity and paranasal sinus on virtual endoscopy and coronal image]

OBJECTIVE

To evaluate normal and bony anatomy of nasal cavity and paranasal sinus on the spiral CT virtual endoscopy(VE) and coronal scanning image.

METHOD

After patients were scanned on axial or coronal position by spiral CT, data were transferred to workstation. Structures such as ostium-meatal complex(OMC) were viewed by navigator software when threshold was changing.

RESULT

Turbinates, meatus and ostium-meatal complex were better viewed by virtual endoscopy compared with by coronal scanning image. To some extent, bony anatomy was clearer.

CONCLUSION

Virtual endoscopy is of value in realizing characteristics of nasal cavity and paranasal sinus anatomy.

Pressure changes in spinal canal and evaluation of spinal cord injuries in spinal section subjected to impact

OBJECTIVE

To observe pressure changes in the spinal canal of the vertebrarium subjected to impact. From the point of view of impact, pressure changes and spinal cord injuries, the relationship between the type of spinal fracture and the severity of spinal cord injuries were analyzed and some experimental data were provided for early evaluation of severity of spinal cord injuries.

METHODS

An experimental model of spinal burst fracture was made with Type BIM-I bio-impact machine and techniques of high velocity vertical loading in static pattern and stress shielding were adopted. Vertebral sections T10-L4 taken from fresh cadavers were impacted and pressure changes in the spinal canal were observed. The types and severity of spinal fracture were studied with gross and radiography examination.

RESULTS

Great positive pressure wave (wave A) in the spinal canal of the 4 vertebral specimens with burst fracture was recorded. The peak value of pressure was correlated with the severity of posterior column injuries. Generally, the peak value of pressure was low in the samples with posterior column injuries, but high in the samples without injuries. The predominant features of fractures were burst fractures of vertebral body and severe destruction of the skeletal and fiber structure of the spinal canal. Positive and negative pressure waves (wave B) were recorded in 2 vertebral samples in which no significant abnormal changes were found by radiography examination, however, a little liquid effusion in the vertebral body was found by gross examination.

CONCLUSIONS

The type of pressure wave in the spinal canal is related to the deformation or the destruction of the spinal canal structure. The peak value of the pressure is non-linearly related to the obstruction in the spinal canal, but related to posterior column injuries.

Cross-electron-transfer reactions of the [Cu(II/I)(bite)](2+/+) redox couple

A series of outer-sphere cross-electron-transfer reactions involving the [Cu(bite)](2+/+) redox couple has been investigated in acetonitrile at 25 degrees C. In this complex, the bite ligand is a macrocyclic N(2)S(2) ligand with a 2,2'-biphenyl moiety as its backbone. The reaction of [Cu(II)(bite)](2+) with [Ru(hfac)(3)](-) produces [Cu(I)(bite)](+) and [Ru(hfac)(3)] reversibly with K = 1.9. The rate law is second order in both directions, with a rate constant of (8.22 +/- 0.27) x 10(2) M(-1) s(-1) in the forward direction. Rate constants were also obtained for the irreversible reactions of three Co(II) clathrochelates with [Cu(bite)](2+). The oxidation of [Cu(bite)](+) by [Fe(bpy)(3)](3+) was studied in order to obtain a rate constant for oxidation as well as reduction. Application of the Marcus cross relationship to these rate constants gives apparent self-exchange rate constants that are reasonably consistent yet unusually low, with an average value of 1.0 x 10(-2) M(-1) s(-1). The self-consistence of the apparent self-exchange rate constants implies that all of the cross reactions proceed through the same intermediate, and hence, the outer-sphere self-exchange reaction should have a second-order rate law with k = 1.0 x 10(-2) M(-1) s(-1). The much faster first-order self-exchange process reported previously for the [Cu(bite)](2+/+) couple in acetone implies a more efficient mechanism for the self-exchange reaction than for the cross reactions, such as an inner-sphere mechanism. Cyclic voltammograms of [Cu(bite)](n+) are strongly sensitive to the nature of the working electrode, thus precluding the use of these data in interpreting the homogeneous redox kinetics.

Focal adhesion kinase activates Stat1 in integrin-mediated cell migration and adhesion

Recent studies suggest that focal adhesion kinase (FAK) is important for cell migration. We now suggest a mechanism by which FAK activates the signal transducer and activator of transcription (STAT) pathway, regulating cell adhesion and migration. In particular, we observe that FAK is capable of activating Stat1, but not Stat3. Co-immunoprecipitation and in vitro binding assays demonstrate that Stat1 is transiently and directly associated with FAK during cell adhesion, and Stat1 is activated in this process. FAK with a C-terminal deletion (FAKDeltaC14) completely abolishes this interaction, indicating this association is dependent on the C-terminal domain of FAK, which is required for FAK localization at focal contacts. Moreover, Stat1 activation during cell adhesion is diminished in FAK-deficient cells, correlating with decreased migration in these cells. Finally, we show that depletion of Stat1 results in an enhancement of cell adhesion and a decrease in cell migration. Thus, our results have demonstrated, for the first time, a critical signaling pathway from integrin/FAK to Stat1 that reduces cell adhesion and promotes cell migration.

[Construction of a bacterial artificial chromosome (BAC) contig encompassing the bacterial blight resistance gene Xa4 locus in rice]

The gene Xa4 confers dominantly resistance to rice bacterial blight, which has been finely mapped between RFLP markers G181 and L1044, and co-segregated with the resistance gene homologues sequence marker RS13. The three markers were used to screen a rice Bacterial Artificial Chromosome (BAC) library constructed from IRBB56, a Xa4-harborring indica variety, resulting in the detection of totally 128 positive clones. Of the 18 positive clones picked out by RS13, 4 and 6 clones were simultaneously detected by G181 and L1044, respectively. Based on their HindIII restriction patterns, 12 clones were selected out to construct a contig that spanned about 420 kb covering the Xa4 locus, which is a solid base for the isolation of Xa4 gene.

Matriptase and HAI-1 are expressed by normal and malignant epithelial cells in vitro and in vivo

Matriptase and its cognate, Kunitz-type serine protease inhibitor, HAI-1, comprise a newly characterized extracellular matrix-degrading protease system that may function as an epithelial membrane activator for other proteases and latent growth factors. Both enzyme and inhibitor have been detected in breast cancer cells, immortalized mammary epithelial cells, and human milk, but not in cultured fibroblasts nor in fibrosarcoma cells. To test the hypothesis that this system is expressed by normal breast epithelium, invasive breast cancers, and other cancers of an epithelial origin (carcinomas) but not in cancers of a mesenchymal origin, we have expanded our expression analysis of matriptase and HAI-1 in vitro and in vivo. Matriptase and HAI-1 were detected at the protein and mRNA levels both in hormone-dependent and hormone-independent cultured breast cancer cells, and this expression correlated with the expression of the epithelial markers E-cadherin or ZO-1. However, none of the breast cancer cell lines tested that express the mesenchymal marker vimentin express matriptase or HAI-1, consistent with an epithelial-selective expression of this system. Expression of matriptase, as determined by Western blot analysis, was observed in primary human breast, gynecological, and colon carcinomas, but not in stromal-derived ovarian tumors and human sarcomas of various origins and histological grades. The epithelial-selective expression of matriptase and HAI-1 was further confirmed in human breast cancers by immunohistochemistry and in situ hybridization, where the expression of the protease and the inhibitor were found in the carcinoma cells and in surrounding normal breast epithelia. The expression of the matriptase/HAI-1 system by malignant epithelial cells in vivo suggests a possible role for this protease in multiple aspects of the pathophysiology of epithelial malignancy, including invasion and metastasis.

Extracellular matrix protein 1 (ECM1) has angiogenic properties and is expressed by breast tumor cells

Tumor growth and metastasis are critically dependent on the formation of new blood vessels. The present study found that extracellular matrix protein 1 (ECM1), a newly described secretory glycoprotein, promotes angiogenesis. This was initially suggested by in situ hybridization studies of mouse embryos indicating that the ECM1 message was associated with blood vessels and its expression pattern was similar to that of flk-1, a recognized marker for endothelium. More direct evidence for the role of ECM1 in angiogenesis was provided by the fact that highly purified recombinant ECM1 stimulated the proliferation of cultured endothelial cells and promoted blood vessel formation in the chorioallantoic membrane of chicken embryos. Immunohistochemical staining with specific antibodies indicated that ECM1 was expressed by the human breast cancer cell lines MDA-435 and LCC15, both of which are highly tumorigenic. In addition, staining of tissue sections from patients with breast cancer revealed that ECM1 was present in a significant proportion of primary and secondary tumors. Collectively, the results of this study suggest that ECM1 possesses angiogenic properties that may promote tumor progression.

[Determination of chloramphenicol in chloramphenicol and dexamethasone sodium phosphate ear drops by first derivative spectrometry]

Determination of chloramphenicol in the ear drops by first derivative spectrometry was studied. The detecting wavelength was 303.0 nm. The linear range was 0-65.2 micrograms.ml-1 (r = 0.9999). The average recovery was 99.84%, RSD = 0.37% (n = 8). The method is simple and accurate.

[Chemical properties and scavenging effects on active oxygen radicals of tea polysaccharides]

The chemical composition and scavenging effects of a kind of glycoprotein from tea on active oxygen free radicals were studied. The tea polysaccharides(TPS) were composed of arabinose, ribose, xylose, glucose and galactose. TPS(8.5-170 mg/L) could scavenge the .OH produced in deoxyribose-Fe2+ reaction and the scavenging rate was between 5.5% to 74.7%.

Predictors of bone mass by peripheral quantitative computed tomography in early adolescent girls

This cross-sectional study used peripheral quantitative computed tomography (pQCT) to evaluate the influences of age, body size, puberty, calcium intake, and physical activity on bone acquisition in healthy early adolescent girls. The pQCT technique provides analyses of volumetric bone mineral density (vBMD) (mg/cm(3)) for total as well as cortical and trabecular bone compartments and bone strength expressed as polar strength strain index (mm(2)). Bone mass of the nondominant distal and midshaft tibia by pQCT and lumbar spine and hip by dual X-ray absorptiometry (DXA) were measured in 84 girls ages 11-14 yr. Pubertal stage, menarche status, anthropometrics, and 3-d food intake and physical activity records were collected. Total and cortical bone mineral content and vBMD measurements by pQCT were significantly related to lumbar spine and femoral neck BMD measurements by DXA. We did not note any significant determinants or predictors for trabecular bone mass. Body weight was the most important predictor and determinant of total and cortical bone density and strength in healthy adolescent girls. Menarche, calcium intake, height, body mass index, and weight-bearing physical activity level age were also identified as minor but significant predictors and determinants of bone density and strength. Bone measurements by the pQCT technique provide information on bone acquisition, architecture, and strength during rapid periods of growth and development. Broader cross-sectional studies using the pQCT technique to evaluate the influence of age, gender, ethnicity, puberty, body size, and lifestyle factors on bone acquisition and strength are needed.