Using Epidemiology and Genomics to Understand Osteosarcoma Etiology

Osteosarcoma is a primary bone malignancy that typically occurs during adolescence but also has a second incidence peak in the elderly. It occurs most commonly in the long bones, although there is variability in location between age groups. The etiology of osteosarcoma is not well understood; it occurs at increased rates in individuals with Paget disease of bone, after therapeutic radiation, and in certain cancer predisposition syndromes. It also occurs more commonly in taller individuals, but a strong environmental component to osteosarcoma risk has not been identified. Several studies suggest that osteosarcoma may be associated with single nucleotide polymorphisms in genes important in growth and tumor suppression but the studies are limited by sample size. Herein, we review the epidemiology of osteosarcoma as well as its known and suspected risk factors in an effort to gain insight into its etiology

Bone mineral density in patients with inherited bone marrow failure syndromes.

BackgroundPatients with inherited bone marrow failure syndromes (IBMFS) may have several risk factors for low bone mineral density (BMD). We aimed to evaluate the prevalence of low BMD in IBMFS and determine the associated risk factors.MethodsPatients with IBMFS with at least one dual-energy X-ray absorptiometry (DXA) scan were evaluated. Diagnosis of each IBMFS, Fanconi anemia (FA), dyskeratosis congenita, Diamond-Blackfan anemia, and Shwachman-Diamond syndrome was confirmed by syndrome-specific tests. Data were gathered on age, height, and clinical history. DXA scans were completed at the lumbar spine, femoral neck, and forearm. BMD was adjusted for height (HAZ) in children (age ≤20 years). Low BMD was defined as a BMD Z-score and HAZ ≤-2 in adults and children, respectively, in addition to patients currently on bisphosphonate therapy.ResultsNine of thirty-five adults (26%) and eleven of forty children (27%) had low BMD. Adults with FA had significantly lower BMD Z-scores than those with other diagnoses; however, HAZ did not vary significantly in children by diagnosis. Risk factors included hypogonadism, iron overload, and glucocorticoid use.ConclusionsAdults and children with IBMFS have high prevalence of low BMD. Prompt recognition of risk factors and management are essential to optimize bone health

Entropy Driven Crystal Formation on Highly Strained Substrates

In heteroepitaxy, lattice mismatch between the deposited material and the underlying surface strongly affects nucleation and growth processes. The effect of mismatch is well studied in atoms with growth kinetics typically dominated by bond formation with interaction lengths on the order of one lattice spacing. In contrast, less is understood about how mismatch affects crystallization of larger particles, such as globular proteins and nanoparticles, where interparticle interaction energies are often comparable to thermal fluctuations and are short ranged, extending only a fraction of the particle size. Here, using colloidal experiments and simulations, we find particles with short-range attractive interactions form crystals on isotropically strained lattices with spacings significantly larger than the interaction length scale. By measuring the free-energy cost of dimer formation on monolayers of increasing uniaxial strain, we show the underlying mismatched substrate mediates an entropy-driven attractive interaction extending well beyond the interaction length scale. Remarkably, because this interaction arises from thermal fluctuations, lowering temperature causes such substrate-mediated attractive crystals to dissolve. Such counterintuitive results underscore the crucial role of entropy in heteroepitaxy in this technologically important regime. Ultimately, this entropic component of lattice mismatched crystal growth could be used to develop unique methods for heterogeneous nucleation and growth of single crystals for applications ranging from protein crystallization to controlling the assembly of nanoparticles into ordered, functional superstructures. In particular, the construction of substrates with spatially modulated strain profiles would exploit this effect to direct self-assembly, whereby nucleation sites and resulting crystal morphology can be controlled directly through modifications of the substrate

The methodological quality of aphasia research: an investigation using the PsycBITE™ database

This paper examines methodological quality of aphasia research using the Psychological database for Brain Injury Treatment Efficacy™(www.psycbite.com). PsycBITE™ includes five designs: Systematic Reviews (SR), Randomised Controlled Trials (RCT), non-RCT (NRCT); Case Series (CS) and Single Subject Designs (SSD). Of 310 studies indexed for aphasia: SR=8 (3%); RCT=22 (7%); NRCT=17 (5%); CS=48 (15%); SSD=215 (69%). Methodological quality ratings (MQR) using the PEDro scale (scored out of 10) were available for 9 RCTs (mean MQR=4.6 SD = 1.5), 5 NRCTs (mean MQR=2.3, SD =1.1), and 12 CSs (mean MQR=0.9, SD =0.7). Methodological quality is discussed with suggestions for future treatment studies

Structure and function of the human Gly1619Arg polymorphism of M6P/IGF2R domain 11 implicated in IGF2 dependent growth

The mannose 6-phosphate/IGF 2 receptor (IGF2R) is comprised of 15 extra-cellular domains that bind IGF2 and mannose 6-phosphate ligands. IGF2R transports ligands from the Golgi to the pre-lysosomal compartment and thereafter to and from the cell surface. IGF2R regulates growth, placental development, tumour suppression and signalling. The ligand IGF2 is implicated in the growth phenotype, where IGF2R normally limits bioavailability, such that loss and gain of IGF2R results in increased and reduced growth respectively. The IGF2R exon 34 (5002A>G) polymorphism (rs629849) of the IGF2 specific binding domain has been correlated with impaired childhood growth (A/A homozygotes). We evaluated the function of the Gly1619Arg non-synonymous amino acid modification of domain 11. NMR and X-ray crystallography structures located 1619 remote from the ligand binding region of domain 11. Arg1619 was located close to the fibronectin type II (FnII) domain of domain 13, previously implicated as a modifier of IGF2 ligand binding through indirect interaction with the AB loop of the binding cleft. However, comparison of binding kinetics of IGF2R, Gly1619 and Arg1619 to either IGF2 or mannose 6-phosphate revealed no differences in ‘on’ and ‘off’ rates. Quantitative PCR, 35S pulse chase and flow cytometry failed to demonstrate altered gene expression, protein half-life and cell membrane distribution, suggesting the polymorphism had no direct effect on receptor function. Intronic polymorphisms were identified which may be in linkage disequilibrium with rs629849 in certain populations. Other potential IGF2R polymorphisms may account for the correlation with childhood growth, warranting further functional evaluation

Buildup from birth onward of short telomeres in human hematopoietic cells

Telomere length (TL) limits somatic cell replication. However, the shortest among the telomeres in each nucleus, not mean TL, is thought to induce replicative senescence. Researchers have relied on Southern blotting (SB), and techniques calibrated by SB, for precise measurements of TL in epidemiological studies. However, SB provides little information on the shortest telomeres among the 92 telomeres in the nucleus of human somatic cells. Therefore, little is known about the accumulation of short telomeres with age, or whether it limits the human lifespan. To fill this knowledge void, we used the Telomere-Shortest-Length-Assay (TeSLA), a method that tallies and measures single telomeres of all chromosomes. We charted the age-dependent buildup of short telomeres (&lt;3 kb) in human hematopoietic cells from 334 individuals (birth-89 years) from the general population, and 18 patients with dyskeratosis congenita-telomere biology disorders (DC/TBDs), whose hematopoietic cells have presumably reached or are close to their replicative limit. For comparison, we also measured TL with SB. We found that in hematopoietic cells, the buildup of short telomeres occurs in parallel with the shortening with age of mean TL. However, the proportion of short telomeres was lower in octogenarians from the general population than in patients with DC/TBDs. At any age, mean TL was longer and the proportion of short telomeres lower in females than in males. We conclude that though converging to the TL-mediated replicative limit, hematopoietic cell telomeres are unlikely to reach this limit during the lifespan of most contemporary humans.</p

Entropy-driven crystal formation on highly strained substrates

In heteroepitaxy, lattice mismatch between the deposited material and the underlying surface strongly affects nucleation and growth processes. The effect of mismatch is well studied in atoms with growth kinetics typically dominated by bond formation with interaction lengths on the order of one lattice spacing. In contrast, less is understood about how mismatch affects crystallization of larger particles, such as globular proteins and nanoparticles, where interparticle interaction energies are often comparable to thermal fluctuations and are short ranged, extending only a fraction of the particle size. Here, using colloidal experiments and simulations, we find particles with short-range attractive interactions form crystals on isotropically strained lattices with spacings significantly larger than the interaction length scale. By measuring the free-energy cost of dimer formation on monolayers of increasing uniaxial strain, we show the underlying mismatched substrate mediates an entropydriven attractive interaction extending well beyond the interaction length scale. Remarkably, because this interaction arises from thermal fluctuations, lowering temperature causes such substratemediated attractive crystals to dissolve. Such counterintuitive results underscore the crucial role of entropy in heteroepitaxy in this technologically important regime. Ultimately, this entropic component of lattice mismatched crystal growth could be used to develop unique methods for heterogeneous nucleation and growth of single crystals for applications ranging from protein crystallization to controlling the assembly of nanoparticles into ordered, functional superstructures. In particular, the construction of substrates with spatially modulated strain profiles would exploit this effect to direct self-assembly, whereby nucleation sites and resulting crystal morphology can be controlled directly through modifications of the substrate. thermodynamics | colloids | tunable depletion interaction C rystal growth typically initiates at surfaces where the barrier for nucleation is significantly lower than in bulk Results Our system consists of 1.30-μm diameter charge stabilized polystyrene spheres in aqueous solution. The solution contains the nonionic surfactant, hexaethylene glycol monodocecyl ether (C 12 E 6 ), which forms micelles in water. The micelles induce an attractive depletion interaction between polystyrene spheres for surface-to-surface distances of approximately one micelle diameter or less. The depth of the interaction potential is proportional to the entropy gained due to the volume liberated to the micelles when the excluded volume around the two particles overlaps with strength of a few k B T, where k B is Boltzmann&apos;s constant and T is temperature. This interaction is strongly dependent on both the concentration and the diameter of the micelles. By using the surfactant C 12 E 6 , whose micelle concentration and diameter both increase with increasing temperature, small temperature changes allow the particles to overcome thermal fluctuations and form colloidal crystals To study the role of strain in heterogeneous crystallization, a single layer of particles is first self-assembled in the holes of a lithographically patterned template In the experiments, we use bright-field microscopy to monitor how interparticle spacing in growing crystals varies with the Author contributions: J.R.S., S.F.H., R.G., S.J.G., A.H., and I.C. designed research; J.R.S., S.F.H., and A.H. performed research; S.J.G. contributed new reagents/analytic tools; J.R.S., S.F.H., S.J.G., A.H., and I.C. analyzed data; and J.R.S., S.F.H., S.J.G., A.H., and I.C. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. PHYSICS lattice constant of the underlying substrate. Single-layer crystals were first assembled on a featureless microscope coverslip. The equilibrium lattice constant was obtained by measuring the nearest-neighbor separation probability distribution, P(r). We find P(r) is symmetric, peaks at l 0 ∼ 1.35 μm, and decays to zero within 25 nm. This equilibrium lattice constant l 0 was compared with P(r) for all particles on substrates with square and rectangular lattice symmetries having lattice constants ranging between 1.350 and 1.500 μm. Images and P(r) measurements on substrates with square symmetry and three different lattice parameters are shown in To identify how entropic and energetic contributions to particle interactions vary with substrate strain, we performed Monte Carlo simulations of particle pairs on substrates of both isotropic and uniaxial strains. The depletion interaction is modeled by the temperature-independent Morse potential U(r) = E 0 [1 − exp(−a (r − l 0 ))] 2 − E 0 , where E 0 is the depth of the potential, l 0 = 1.0, and a is inversely proportional to the width of the potential. This interaction is applied to all particles, including both in-plane interactions and particle interactions with the underlying substrate, to faithfully reproduce the experiments. As seen in the experiments, gravity is weak compared with the interaction potential-P(r) particles leave the substrate when the interaction level is too low. Calculations show gravitational effects are more than one order of magnitude smaller. We find the parameters a = 65 and E 0 /k B T = 2.27 reproduce the dependence of ΔF s/us /k B T on uniaxial strain as measured in the experiments The temperature-dependent probability p cryst that neighboring crystallizing particles are bonded can be approximated by reflecting twice the probability distribution P(r/l 0 &lt; 1) about the line r/l 0 = 1, as shown by the blue shaded area in These results reveal a process in which entropy-driven thermal fluctuations stabilize crystal formation on substrates with lattice constants significantly larger than the interaction range. Although previous work has described particle crystallization on strained lattices under the influence of depletion potentials PHYSICS results and calculations have direct bearing on heterogeneous crystallization of globular proteins and nanoparticles (26). Specifically, they clarify how the free energy changes with temperature. As illustrated by Methods Sample Preparation. Samples are prepared by adding NaCl (4 mM) to deionized water, after which the nonionic surfactant C 12 E 6 is added (2 wt%). Once the surfactant has equilibrated, polystyrene particles (3% polydispersity; Molecular Probes) are added to the solution. Templates are fabricated by spinning 500 nm poly(methyl methacrylate) onto a microscope coverslip and using electron beam lithography to pattern holes with a diameter of 1.26 μm. The sample is injected into a sample cell formed between the patterned coverslip and a microscope slide with a 170-μm spacer used to set the gap in height. The sample cell is sealed to prevent flow. Temperature control is accomplished by attaching an objective heater to a 100× (1.4 NA) objective and encasing the inverted microscope in a heated chamber with temperature fluctuations ±0.1°C. All data are acquired after the temperature has equilibrated using bright-field microscopy. Computer Simulations. Monte Carlo simulations using the standard Metropolis criterion were applied. To calculate the probability a dimer arranged parallel or perpendicular to the strained direction in the uniaxially strained case, the Monte Carlo moves also contain rotations of the dimer to generate the large number of transitions between orientations. Free-energy differences are calculated from the Boltzmann probability distribution. Using the Morse potential energy then gives the entropic contribution. We restrict the height of the second-layer particles to (z − z 0 )/l 0 ≤ 0.03 because for larger distances above the bottom layer, particles would start to desorb. ACKNOWLEDGMENTS. The authors thank James Sethna for comments

Entropy-driven crystal formation on highly strained substrates

In heteroepitaxy, lattice mismatch between the deposited material and the underlying surface strongly affects nucleation and growth processes. The effect of mismatch is well studied in atoms with growth kinetics typically dominated by bond formation with interaction lengths on the order of one lattice spacing. In contrast, less is understood about how mismatch affects crystallization of larger particles, such as globular proteins and nanoparticles, where interparticle interaction energies are often comparable to thermal fluctuations and are short ranged, extending only a fraction of the particle size. Here, using colloidal experiments and simulations, we find particles with short-range attractive interactions form crystals on isotropically strained lattices with spacings significantly larger than the interaction length scale. By measuring the free-energy cost of dimer formation on monolayers of increasing uniaxial strain, we show the underlying mismatched substrate mediates an entropydriven attractive interaction extending well beyond the interaction length scale. Remarkably, because this interaction arises from thermal fluctuations, lowering temperature causes such substratemediated attractive crystals to dissolve. Such counterintuitive results underscore the crucial role of entropy in heteroepitaxy in this technologically important regime. Ultimately, this entropic component of lattice mismatched crystal growth could be used to develop unique methods for heterogeneous nucleation and growth of single crystals for applications ranging from protein crystallization to controlling the assembly of nanoparticles into ordered, functional superstructures. In particular, the construction of substrates with spatially modulated strain profiles would exploit this effect to direct self-assembly, whereby nucleation sites and resulting crystal morphology can be controlled directly through modifications of the substrate. thermodynamics | colloids | tunable depletion interaction C rystal growth typically initiates at surfaces where the barrier for nucleation is significantly lower than in bulk Results Our system consists of 1.30-μm diameter charge stabilized polystyrene spheres in aqueous solution. The solution contains the nonionic surfactant, hexaethylene glycol monodocecyl ether (C 12 E 6 ), which forms micelles in water. The micelles induce an attractive depletion interaction between polystyrene spheres for surface-to-surface distances of approximately one micelle diameter or less. The depth of the interaction potential is proportional to the entropy gained due to the volume liberated to the micelles when the excluded volume around the two particles overlaps with strength of a few k B T, where k B is Boltzmann&apos;s constant and T is temperature. This interaction is strongly dependent on both the concentration and the diameter of the micelles. By using the surfactant C 12 E 6 , whose micelle concentration and diameter both increase with increasing temperature, small temperature changes allow the particles to overcome thermal fluctuations and form colloidal crystals To study the role of strain in heterogeneous crystallization, a single layer of particles is first self-assembled in the holes of a lithographically patterned template In the experiments, we use bright-field microscopy to monitor how interparticle spacing in growing crystals varies with the Author contributions: J.R.S., S.F.H., R.G., S.J.G., A.H., and I.C. designed research; J.R.S., S.F.H., and A.H. performed research; S.J.G. contributed new reagents/analytic tools; J.R.S., S.F.H., S.J.G., A.H., and I.C. analyzed data; and J.R.S., S.F.H., S.J.G., A.H., and I.C. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. PHYSICS lattice constant of the underlying substrate. Single-layer crystals were first assembled on a featureless microscope coverslip. The equilibrium lattice constant was obtained by measuring the nearest-neighbor separation probability distribution, P(r). We find P(r) is symmetric, peaks at l 0 ∼ 1.35 μm, and decays to zero within 25 nm. This equilibrium lattice constant l 0 was compared with P(r) for all particles on substrates with square and rectangular lattice symmetries having lattice constants ranging between 1.350 and 1.500 μm. Images and P(r) measurements on substrates with square symmetry and three different lattice parameters are shown in To identify how entropic and energetic contributions to particle interactions vary with substrate strain, we performed Monte Carlo simulations of particle pairs on substrates of both isotropic and uniaxial strains. The depletion interaction is modeled by the temperature-independent Morse potential U(r) = E 0 [1 − exp(−a (r − l 0 ))] 2 − E 0 , where E 0 is the depth of the potential, l 0 = 1.0, and a is inversely proportional to the width of the potential. This interaction is applied to all particles, including both in-plane interactions and particle interactions with the underlying substrate, to faithfully reproduce the experiments. As seen in the experiments, gravity is weak compared with the interaction potential-P(r) particles leave the substrate when the interaction level is too low. Calculations show gravitational effects are more than one order of magnitude smaller. We find the parameters a = 65 and E 0 /k B T = 2.27 reproduce the dependence of ΔF s/us /k B T on uniaxial strain as measured in the experiments The temperature-dependent probability p cryst that neighboring crystallizing particles are bonded can be approximated by reflecting twice the probability distribution P(r/l 0 &lt; 1) about the line r/l 0 = 1, as shown by the blue shaded area in These results reveal a process in which entropy-driven thermal fluctuations stabilize crystal formation on substrates with lattice constants significantly larger than the interaction range. Although previous work has described particle crystallization on strained lattices under the influence of depletion potentials PHYSICS results and calculations have direct bearing on heterogeneous crystallization of globular proteins and nanoparticles (26). Specifically, they clarify how the free energy changes with temperature. As illustrated by Methods Sample Preparation. Samples are prepared by adding NaCl (4 mM) to deionized water, after which the nonionic surfactant C 12 E 6 is added (2 wt%). Once the surfactant has equilibrated, polystyrene particles (3% polydispersity; Molecular Probes) are added to the solution. Templates are fabricated by spinning 500 nm poly(methyl methacrylate) onto a microscope coverslip and using electron beam lithography to pattern holes with a diameter of 1.26 μm. The sample is injected into a sample cell formed between the patterned coverslip and a microscope slide with a 170-μm spacer used to set the gap in height. The sample cell is sealed to prevent flow. Temperature control is accomplished by attaching an objective heater to a 100× (1.4 NA) objective and encasing the inverted microscope in a heated chamber with temperature fluctuations ±0.1°C. All data are acquired after the temperature has equilibrated using bright-field microscopy. Computer Simulations. Monte Carlo simulations using the standard Metropolis criterion were applied. To calculate the probability a dimer arranged parallel or perpendicular to the strained direction in the uniaxially strained case, the Monte Carlo moves also contain rotations of the dimer to generate the large number of transitions between orientations. Free-energy differences are calculated from the Boltzmann probability distribution. Using the Morse potential energy then gives the entropic contribution. We restrict the height of the second-layer particles to (z − z 0 )/l 0 ≤ 0.03 because for larger distances above the bottom layer, particles would start to desorb. ACKNOWLEDGMENTS. The authors thank James Sethna for comments