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1.
Aviat Space Environ Med ; 76(10): 915-22, 2005 Oct.
Article in English | MEDLINE | ID: mdl-16235873

ABSTRACT

INTRODUCTION: Static bone histomorphometry was applied to existing iliac bone sections originating from a 370-d 5 degrees head-down bed rest experiment. This bed rest experiment is the longest ever to have been conducted. We hypothesized that bed rest would decrease cancellous bone volume fraction and that this effect would be reversed by countermeasures. METHODS: Eight healthy male subjects underwent 370 d of 5 degrees head-down bed rest. Three subjects were treated with bisphosphonate (Xidifon, potassium salt of ethane-1-hydroxy-1-disphosphonate, EHDP) combined with an exercise regimen (1-2 h x d(-1)) for the entire study period. Five subjects underwent 120 d of bed rest without countermeasures followed by 250 d of bed rest with the exercise regimen. Transiliac bone biopsies were obtained either at baseline and day 366, or at baseline, day 116, and day 366 at alternating sides of the ileum. Static histomorphometry was performed using a computerized method. RESULTS: The 120 d of head-down bed rest without countermeasures resulted in decreased bone volume fraction BV/TV (-6.3%, p = 0.046) and trabecular number (Tb.N; -10.2%, p = 0.080) and increased trabecular separation (Tb.Sp; 14.7%, p = 0.020), whereas the 250 d of subsequent head-down bed rest with exercise treatment prevented further significant deterioration of the histomorphometric measures. DISCUSSION: The 120 d of 5 degrees head-down bed rest without countermeasures induced significant deterioration of iliac crest cancellous bone histomorphometric properties. On average, the countermeasures consisting of either bisphosphonate and exercise, or exercise alone were able to either prevent or stop immobilization-induced changes of the iliac cancellous bone structure.


Subject(s)
Bed Rest , Head-Down Tilt/adverse effects , Ilium/anatomy & histology , Ilium/cytology , Osteoporosis/physiopathology , Adult , Biopsy , Diphosphonates/therapeutic use , Humans , Iliac Aneurysm , Male , Space Flight
2.
Acta Astronaut ; 56(9-12): 820-30, 2005.
Article in English | MEDLINE | ID: mdl-15835013

ABSTRACT

Changes in trabecular bone composition during development of osteoporosis are used as a model for bone loss in microgravity conditions during a space flight. Symbolic dynamics and measures of complexity are proposed and applied to assess quantitatively the structural composition of bone tissue from 3D data sets of human tibia bone biopsies acquired by a micro-CT scanner. In order to justify the newly proposed approach, the measures of complexity of the bone architecture were compared with the results of traditional 2D bone histomorphometry. The proposed technique is able to quantify the structural loss of the bone tissue and may help to diagnose and to monitor changes in bone structure of patients on Earth as well as of the space-flying personnel.


Subject(s)
Bone Density , Osteoporosis/physiopathology , Tibia/anatomy & histology , Aged , Aged, 80 and over , Algorithms , Bone Demineralization, Pathologic , Cadaver , Female , Humans , Image Processing, Computer-Assisted , Imaging, Three-Dimensional , Male , Microradiography , Middle Aged , Osteoporosis/diagnostic imaging , Tibia/diagnostic imaging
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