Direct in vivo strain measurements in human bone-a systematic literature review.

Bone strain is the governing stimuli for the remodeling process necessary in the maintenance of bone's structure and mechanical strength. Strain gages are the gold standard and workhorses of human bone experimental strain analysis in vivo. The objective of this systematic literature review is to provide an overview for direct in vivo human bone strain measurement studies and place the strain results within context of current theories of bone remodeling (i.e. mechanostat theory). We employed a standardized search strategy without imposing any time restriction to find English language studies indexed in PubMed and Web of Science databases that measured human bone strain in vivo. Twenty-four studies met our final inclusion criteria. Seven human bones were subjected to strain measurements in vivo including medial tibia, second metatarsal, calcaneus, proximal femur, distal radius, lamina of vertebra and dental alveolar. Peak strain magnitude recorded was 9096 µÎµ on the medial tibia during basketball rebounding and the peak strain rate magnitude was -85,500 µÎµ/s recorded at the distal radius during forward fall from standing, landing on extended hands. The tibia was the most exposed site for in vivo strain measurements due to accessibility and being a common pathologic site of stress fracture in the lower extremity. This systematic review revealed that most of the strains measured in vivo in different bones were generally within the physiological loading zone defined by the mechanostat theory, which implies stimulation of functional adaptation necessary to maintain bone mechanical integrity.

A full body musculoskeletal model based on flexible multibody simulation approach utilised in bone strain analysis during human locomotion.

Load-induced strains applied to bone can stimulate its development and adaptation. In order to quantify the incident strains within the skeleton, in vivo implementation of strain gauges on the surfaces of bone is typically used. However, in vivo strain measurements require invasive methodology that is challenging and limited to certain regions of superficial bones only such as the anterior surface of the tibia. Based on our previous study [Al Nazer et al. (2008) J Biomech. 41:1036-1043], an alternative numerical approach to analyse in vivo strains based on the flexible multibody simulation approach was proposed. The purpose of this study was to extend the idea of using the flexible multibody approach in the analysis of bone strains during physical activity through integrating the magnetic resonance imaging (MRI) technique within the framework. In order to investigate the reliability and validity of the proposed approach, a three-dimensional full body musculoskeletal model with a flexible tibia was used as a demonstration example. The model was used in a forward dynamics simulation in order to predict the tibial strains during walking on a level exercise. The flexible tibial model was developed using the actual geometry of human tibia, which was obtained from three-dimensional reconstruction of MRI. Motion capture data obtained from walking at constant velocity were used to drive the model during the inverse dynamics simulation in order to teach the muscles to reproduce the motion in the forward dynamics simulation. Based on the agreement between the literature-based in vivo strain measurements and the simulated strain results, it can be concluded that the flexible multibody approach enables reasonable predictions of bone strain in response to dynamic loading. The information obtained from the present approach can be useful in clinical applications including devising exercises to prevent bone fragility or to accelerate fracture healing.

Flexible multibody simulation approach in the analysis of tibial strain during walking.

Strains within the bone tissue play a major role in bone (re)modeling. These small strains can be assessed using experimental strain gage measurements, which are challenging and invasive. Further, the strain measurements are, in practise, limited to certain regions of superficial bones only, such as the anterior surface of the tibia. In this study, tibial strains occurring during walking were estimated using a numerical approach based on flexible multibody dynamics. In the introduced approach, a lower body musculoskeletal model was developed by employing motion capture data obtained from walking at a constant velocity. The motion capture data were used in inverse dynamics simulation to teach the muscles in the model to replicate the motion in forward dynamics simulation. The maximum and minimum tibial principal strains predicted by the model were 490 and -588 microstrain, respectively, which are in line with literature values from in vivo measurements. In conclusion, the non-invasive flexible multibody simulation approach may be used as a surrogate for experimental bone strain measurements and thus be of use in detailed strain estimations of bones in different applications.

Genome DNA sequencing around the EF-1 alpha multigene locus of Arabidopsis thaliana indicates a high gene density and a shuffling of noncoding regions.

In Arabidopsis thaliana, EF-1 alpha proteins are encoded by a multigene family of four members. Three of them are clustered at the same locus, which was positioned 24 cM from the top of chromosome 1. A region of DNA spanning 63 kb around these locus was sequenced and analyzed. One main characteristic of the locus is the mosaic organization of both genes and intergenic regions. Fourteen genes were identified, among which only four were already described, and other unidentified are most likely present. Functionally diverse genes are found at close intervals. Exon and intron distribution is highly variable at this locus, one gene being split into at least 20 introns. Several duplications were found within the sequenced segment both in coding and noncoding regions, including two gene families. Moreover, a sequence corresponding to the 5' noncoding region of the EF-1 alpha genes and harboring a 5' intervening sequence is duplicated and found upstream of several genes, suggesting that noncoding regions can be shuffled during evolution.

[Vitamin E as protective agent against hemolysis in leprosy patients under dapsone treatment]. / Vitamina E como agente protector de hemólisis en pacientes de lepra tratados con dapsona.

Dapsone (4,4'diaminodiphenyl-sulphone) commonly used in the treatment of patients who suffer from leprosy, is a strongly oxidative drug, producing damage to the red cell membrane. This study investigated whether Vitamin E would have a protective effect on the red cell membrane from oxidant damage caused by Dapsone in patients with leprosy. We have studied 16 patients for 4 months, divided into two groups. Group 1 (n = 7) dapsone (DDS): 100 mg/day; Group 2 (n = 9) dapsone: 100 mg/day in addition with Vitamin E: 800 U/day. We did not include patients with low levels of Glucose-6-Phosphate Dehydrogenase (G-6-PD) because of their sensibility to this drug. At the beginning of the treatment we determined the level of G-6-PD. All patients showed a normocytic normochromic anemia with a decrease in Haptoglobine levels (below 5 mg/dl). Statistical analyses showed that reticulocyte counts did not present significant differences between groups all through evolution. As for methemoglobin (Hi) we observed in Group 1 an increase between the first and the fourth month, which was not seen in group 2. Statistical analyses of the results suggest that oral Vitamin E confers partial protective effect and does not correct the hemolysis parameters produced by Dapsone treatment except for Hi levels which were more sensitive to the oxidant damage.

[Erroneous extrapolation as a frequent defect in medical students]. / La extrapolación errónea como defecto frecuente en alumnos de medicina.

Scientific aptitude development, useful for methodic management of information, is indispensable for teaching and learning, investigation, medical practice and customary life. Correct extrapolation is one of its components. This work deals with appropriate use of extrapolation among medical students. 118 students from a potentially experimented, interested and adapted population were analyzed (103 coursing 2nd. year and the others, last years). All of them were exposed simultaneously and without opportunities of exchanging opinions, to three tests: graphical, clinical and general (open answer). Results point out extrapolation as a current defect in the studied population. Deficiencies in related teaching experiences are also revealed. On the other hand, certain designs--although in the general low level of correct answers--appeared more familiar than others to the students. A deepening of analysis in extrapolation scientific aptitude and preventive exposition to valid experiences since 1st. year of medical career is proposed.

La extrapolación errónea como defecto frecuente en alumnos de medicina. / [Erroneous extrapolation as a frequent defect in medical students]

Scientific aptitude development, useful for methodic management of information, is indispensable for teaching and learning, investigation, medical practice and customary life. Correct extrapolation is one of its components. This work deals with appropriate use of extrapolation among medical students. 118 students from a potentially experimented, interested and adapted population were analyzed (103 coursing 2nd. year and the others, last years). All of them were exposed simultaneously and without opportunities of exchanging opinions, to three tests: graphical, clinical and general (open answer). Results point out extrapolation as a current defect in the studied population. Deficiencies in related teaching experiences are also revealed. On the other hand, certain designs--although in the general low level of correct answers--appeared more familiar than others to the students. A deepening of analysis in extrapolation scientific aptitude and preventive exposition to valid experiences since 1st. year of medical career is proposed.

[Ultrastructural changes in the human nasal respiratory epithelium in hypersensitivity reactions]. / Modificaciones ultraestructurales del epitelio respiratorio nasal humano en reacciones de hipersensibilidad.

In immunoallergic syndromes, the structure of normal respiratory nasal mucous membrane is modified. The epithelial lining (which is responsible for the effectiveness of the mucociliary synergy), is secondarily affected. Its modifications depend, generally, on the severity and chronicity of the clinical case. Normal and pathologic material obtained from inferior turbinate bone (of similar structure and response to the rest of the respiratory nasal mucous membrane) were studied through transmission and scanning electron microscopies, employing both methods as complementary analysis. In normal cases, the presence of different kinds of cells was confirmed. Some additional characteristics about intercellular spaces and junctions as well as the possible role of the above mentioned structures in transudation were also described. In pathologic cases, increasing lesion staging grades could be determined. In the first stage, structural alterations could not be observed despite the existence of functional disturbances (i.e. ciliary dyskinesia and non-synergic motility). In an advanced stage, ciliary abnormalities could be observed with abnormalities in the number, morphology, spatial orientation and distortion in the number of different cell types. With cellular linkage affectation, the severity of the lesion increased and the cells were easily desquamated, giving rise to intercellular spaces which communicated freely with the organ lumen. Finally, in the most severe cases, the epithelial lining was diminished to a monolayer, with complete cellular dissociation and lack of differentiation. This cellular disarrangement allowed free passage of substances in both directions through the monolayer.

[Innovative approach of teaching-learning of histology and embriology]. / Enfoque innovador de la enseñanza-aprendizaje de histología y embriología.

The paper presents an innovative approach to the teaching-learning of histology and embryology. The traditional teaching of the subject in the Faculty of Medical Sciences of Rosario National University, Santa Fe, Rosario, Argentina, up to 1974 is subjected to critical analysis, and on this basis the need for the innovation is propounded and the method for applying it proposed. A detailed account is given of the theoretical framework of the experiment reported, of the general and specific objectives of the teaching-learning technique, and of the thematic units into which the curriculum was divided. In the teaching-learning plan followed--described in the article--the conventional professorial lecture and its accompanying practical demonstrations are replaced by round tables and theoretical-practical tasks requiring active involvement and integrating theory and practice, in which teams tackle problems under teacher coordination. It also provides for evaluation of the students, teachers and course and eliminates the conventional examination.