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  • 1
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    Inferring the Evolutionary History of Primate microRNA Binding Sites: Overcoming Motif Counting Biases (2014)
    Oxford University Press
    Details
    Publication Date: 2014-06-26
    Description: The first microRNAs (miRNAs) were identified as essential, conserved regulators of gene expression, targeting the same genes across nearly all bilaterians. However, there are also prominent examples of conserved miRNAs whose functions appear to have shifted dramatically, sometimes over very brief periods of evolutionary time. To determine whether the functions of conserved miRNAs are stable or dynamic over evolutionary time scales, we have here defined the neutral turnover rates of short sequence motifs in predicted primate 3'-UTRs. We find that commonly used approaches to quantify motif turnover rates, which use a presence/absence scoring in extant lineages to infer ancestral states, are inherently biased to infer the accumulation of new motifs, leading to the false inference of continually increasing regulatory complexity over time. Using a maximum likelihood approach to reconstruct individual ancestral nucleotides, we observe that binding sites of conserved miRNAs in fact have roughly equal numbers of gain and loss events relative to ancestral states and turnover extremely slowly relative to nearly identical permutations of the same motif. Contrary to case studies showing examples of functional turnover, our systematic study of miRNA binding sites suggests that in primates, the regulatory roles of conserved miRNAs are strongly conserved. Our revised methodology may be used to quantify the mechanism by which regulatory networks evolve.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
    Published by Oxford University Press
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  • 2
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    Monitoring of parameters of functional and cost analysis of personnel processes of the enterprise quality management system (2020)
    Institute of Physics
    Details
    Publication Date: 2020-09-26
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics
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  • 3
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    Management of personnel risks in the organisation quality management system (2019)
    Institute of Physics
    Details
    Publication Date: 2019-05-01
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics
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  • 4
    Electronic Resource
    Electronic Resource
    The effect of fluoride on bone of rats fed diets deficient in calcium or phosphorus (1977)
    Springer
    Calcified tissue international 22 (1977), S. 9-17 
    Details
    ISSN: 1432-0827
    Keywords: Bone ; Fluoride ; Calcium ; Phosphorus ; Mechanical Strength
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract Four groups of weanling rats were fed for 2 weeks on a diet sufficient or insufficient in calcium and/or phosphorus. Each group was divided into four subgroups which were offered distilled water supplemented with 0, 50, 75, or 150 ppm fluoride. High levels of fluoride in drinking water inhibited weight gain. This inhibition was less in rats deficient in phosphorus than when normal-phosphorus diets were offered. At a low level, fluoride was without any effect on bone ash, thickness of femoral cortical bone, and mechanical strength, as measured by maximal load, ultimate stress to breaking, and limit of elasticity. Modulus of elasticity was decreased. At higher levels fluoride tended to decrease most of these parameters, except in rats deprived of both calcium and phosphorus. The effect of fluoride was modified by lack of dietary calcium and/or phosphorus and appeared to be weaker in rats deficient in these nutrients. Lack of dietary calcium and/or phosphorus decreased bone strength more than did fluoride content of water and of bone mineral. Concentration of bone ash and thickness of femoral cortical bone were closely correlated with parameters of mechanical strength.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02010341
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of local application of fluoride on healing of experimental bone fractures in rabbits (1977)
    Springer
    Calcified tissue international 22 (1977), S. 297-302 
    Details
    ISSN: 1432-0827
    Keywords: Fluoride ; Gelfoam ; Fracture ; Ossification ; Breaking force
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract The effect of local application of low fluoride concentrations on the healing of experimental bone-radii fractures in 20 rabbits was examined. No external fixation was required after the osteotomy and gelfoamℜ being used as a medium for fluoride application. Histologic mineral and mechanical strength measurements were carried out on the healing callus. There were no significant changes in the ashpercentage and the fluoride concentration of the ash between the experimental and control callus. A significantly higher percentage of ossified tissue was found in the fluoride treated callus. The breaking strength was found to be significantly higher in the bone fractures treated with fluoride, whereas there was no notable difference between the surface areas. It is postulated that the greater amount of ossified tissues, the differences in organization of the bone trabecules, and/or an improved mineral crystallinity may be responsible for this result.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02010368
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of cholecalciferol derivatives on the mechanical properties of chick bones (1982)
    Springer
    Calcified tissue international 34 (1982), S. 501-505 
    Details
    ISSN: 1432-0827
    Keywords: Cholecalciferol ; 1α-Hydroxychole-calciferol ; 24R, 25-Dihydroxycholecalciferol ; Mechanical properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Chicks were depleted of vitamin D, divided into groups, and treated daily with (a) cholecalciferol, (b) 1α-hydroxycholecalciferol [1α(OH)-D3], (c) 24R, 25-dihydroxycholecalciferol [24R,25-(OH)2D3], or (d) 1α(OH)D3 and 24R,25(OH)2D3. Two additional groups of chicks were studied, one that was continuously depleted of vitamin D, and another that was continuously supplemented with the vitamin, since day 1. After killing, the tibiae were removed and tested for their mechanical properties. Bending load was applied to the midshaft, and the intrinsic properties of this site, its quantity and geometry were analyzed. From a mechanical point of view, the weakest bones found were of birds depleted of vitamin D, whereas the strongest were of those treated with 1α(OH)D3. Only the bones of the 24R,25(OH)2D3-treated or the 1α(OH)D3 and 24R,25(OH)2D3-treated groups of birds showed mechanical properties comparable to those obtained with vitamin D-replete chicks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02411292
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  • 7
    Electronic Resource
    Electronic Resource
    Characterisation of the dynamic vertical force distribution under the foot (1982)
    Springer
    Medical & biological engineering & computing 20 (1982), S. 12-18 
    Details
    ISSN: 1741-0444
    Keywords: Biomechanics ; Foot ; Force distribution ; Force plate ; Rheumatoid arthritis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Measurement of force distribution under the sole of the foot during walking can provide enormous quantities of data with modern recording techniques. Methods are described for presenting such data in pictorial, in parametric and in graphical form. Parametric characterisations include magnitude, timing and location of peak forces and ‘impulses’ (the force-time integrals), parameters describing the local concentration of force and the distribution of the ‘impulse’ over areas of the foot sole. Pictorial displays include force-time graphs for selected areas of the foot, display of movement of the centre of pressure on specific areas and cross-sections through the pressure distribution profile at a specified recorded instant. Such characterisations were considered useful if they provided information on pathological conditions of the feet. A ‘normal’ group was studied to give a baseline for comparisons. An example of abnormality, compared with the normal group, in a patient with rheumatoid arthritis is given. This demonstrates an abnormal distribution of force on the forefoot, and abnormal movement of the centre of pressure consistent with the patient favouring a painful region for weight-bearing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02441844
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  • 8
    Electronic Resource
    Electronic Resource
    Role of the calcaneal inclination in the energy storage capacity of the human foot—a biomechanical model (1990)
    Springer
    Medical & biological engineering & computing 28 (1990), S. 149-152 
    Details
    ISSN: 1741-0444
    Keywords: Calcaneal inclination ; Energy storage ; Foot ; Longitudinal arch ; Model ; Stress fractures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The energy storage capacity of the human foot as a passive structure depends on both its geometry and elastic properties. The present study examines theoretically the relationship between the energy stored in the longitudinal arch and the inclination of the calcaneus, when a vertical load is applied. A simple two-dimensional model was used, consisting of two inclined rigid elements, hinged at the apex of the arch and connected by a horizontal tension spring at the bottom of the arch. The spring serves as the energy-storing element of the model, representing the foot plantar ligaments. The behaviour of the model was examined using both a linear and an exponential spring. It demonstrated that the stored energy depends strongly on the calcaneal inclination. For a given vertical load, the energy storage capacity is low at both large and small inclinations and rises markedly at an intermediate value. Assuming that the incidence of stress fractures during locomotion is affected by insufficient energy attenuation of the foot, this model provides an explanation for the higher prevalence of tibial and femoral stress fractures in subjects with high or low arches.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02441770
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of Fatiguing Exercise on Longitudinal Bone Strain as Related to Stress Fracture in Humans (1998)
    Springer
    Annals of biomedical engineering 26 (1998), S. 660-665 
    Details
    ISSN: 1573-9686
    Keywords: Stress fracture ; Bone strain ; Fatigue ; Aging ; Exercise
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Muscular fatigue in the training athlete or military recruit has been hypothesized to cause increased bone strain that may contribute to the development of a stress fracture. Under normal circumstances, muscles exert a protective effect by contracting to reduce bending strains on cortical bone surfaces. In vivo strain studies in dogs show that muscle fatigue following strenuous exercise elevates bone strain and changes strain distribution. However, a similar experiment has yet to be performed in humans. The purpose of this work was to test the hypothesis in humans that strenuous fatiguing exercise causes an elevation in bone strain. It was also hypothesized that this elevation is greater in younger people than in older people due to the decline in muscle strength and endurance that normally occurs with age. To test these hypotheses, strain in the tibiae of seven human volunteers was measured during walking before and after a period of fatiguing exercise. Neither hypothesis was sustained. Post-hoc analysis of the strain data suggests that strain rate increases after fatigue with a greater increase in younger as opposed to older persons. Although not conclusive, this suggests that it is strain rate, rather than strain magnitude, that may be causal for stress fracture. © 1998 Biomedical Engineering Society. PAC98: 8745Dr, 8745Bp, 0180+b
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1114/1.103
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  • 10
    Electronic Resource
    Electronic Resource
    The relation between external dimensions of the human mandible and cortical bone morphology as determined with the aid of CT scans (1993)
    Springer
    Human evolution 8 (1993), S. 111-123 
    Details
    ISSN: 1824-310X
    Keywords: Mandible ; Morphometry ; moments of inertia ; Biomechanics ; Cortical bones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Computerized tomographs were taken of 22 mandibles, selected from an early Arab population and aged between 17 and 60 years. A specially designed holder was used to define specific locations along the mandible, namely symphysis, mid sagittal section through the corpus, midpoint of the first molar (M1), gonion and ramus. Cortical cross sectional area and principal moments of inertia were then calculated for the locations specified, to obtain estimates of the resistance of the bone to deformation. They were analyzed in relation to age, sex, side and external dimensions of the mandible. The error of measurement calculated from (i) repeated CT scans (ii) repeated measurements (iii) from comparison of CT scans with a sectioned mandible, were of the same order of magnitude. All values were greater in males than in females; they were only slightly affected by age and were unaffected by side. Mandibular length and ramus height accounted for most of the variation observed in moments of inertia. We consider that these results can best be interpreted in accordance with the hypotheses put forward by Hylander (1975, 1985) according to which the mandible acts as a third degree lever, with “wishboning” forces acting at the symphysis and parasagittal bending at the first molar. We now plan to apply this method to study the “strength” of the mandibles of past populations with different dietary adaptations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02436610
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