Analysis of bone tissue mechanical properties

This paper deals with the torsional moment depending on the angle of torsion of the compact bone in laboratory animals and humans. Based on the data from laboratory animals, obtained by measurement, the data on dependence of the torsional moment and the angle of torsion were assumed for humans. Measurements were carried out on four groups of compact bone in laboratory animals. One was the control group, and three other groups were treated by various vitamin D3 metabolites. Equal measurements were performed in only one group of compact bone in humans, due to the impossibility to treat humans with vitamin D3 metabolites. Functional relations between the angle of torsion and the torsional moment for all groups of animal body tissue were determined by measurements, and the results were used to assume the reaction of human compact bone tissue if treated by vitamin D3 metabolites.     

Effects of 1 alpha(OH)-vitamin D3 and 24,25(OH)2-vitamin D3 on long bones of glucocorticoid-treated rats.

Glucocorticoids may induce osteopenia in experimental animals and in man. In order to study the possible effects of vitamin D metabolites in the prevention of glucocorticoid-induced osteopenia in rats, we administered 1 alpha(OH)-vitamin D3, 24,25(OH)2-vitamin D3 or a combination of both metabolites, by intragastric intubation, to rats treated daily by intramuscular injections of 10 mg/kg cortisone acetate. Treatment with the vitamin D metabolites started after 1 month of glucocorticoid therapy, at the time osteopenia was already present. Cortisone acetate decreased the gain weight, increased alkaline phosphatase (AP) and decreased Ca serum levels. It also decreased tibial wet and ash weight and tibial Ca content. Computerized histomorphometry of sections from the upper tibia showed decreased epiphyseal bone volume and increased bone marrow volume; decreased height of hypertrophic cartilage in the growth plate and decreased amount of persisting cartilage in the metaphyseal bone trabeculae were also observed. Administration of 24,25(OH)2D3 alone did not reduce these glucocorticoid-induced bone changes and sometimes even worsened them. 1 alpha(OH)D3 reversed many of the deleterious effects of cortisone acetate. It reduced serum AP levels, increased serum Ca levels, increased bone ash weight, epiphyseal and metaphyseal bone volume, with a concomitant reduction in epiphyseal and metaphyseal bone marrow volume. The best results were obtained by a combination of 1 alpha(OH)D3 and 24,25(OH)2D3. It is presumed that both metabolites are needed to reduce the impact of glucocorticoids on bone. 1 alpha(OH)2D3 acts on the gut, increasing Ca absorption (which was decreased by glucocorticoids), and 24,25(OH)2D3 directly acts on bone to enhance bone formation and mineralization.     

Biologically active metabolite of vitamin D3 from bone, liver, and blood serum

Radioactive metabolites present in bone, blood, liver, and feces of rats given (3)H vitamin D(3) have been isolated. Of these the aqueous soluble metabolite(s) from tissue and all those isolated from feces did not cure rickets in rats, while all the others were at least partially active in this regard. One of the metabolites proved to be as active as the parent vitamin in curing rickets and was found in large amounts in liver, blood, and bone. As much as 50-80% of the radioactivity in bone was found in this metabolite after a 500 IU oral dose of (3)H vitamin D(3). With 10 IU doses of 1,2-(3)H vitamin D(3), most of the radioactivity of the organs examined was found in this metabolite fraction. This metabolite appears to be more polar than vitamin D and is not an esterified form of the vitamin nor a complex of the vitamin with tissue lipids. Its possible role as the metabolically active form of the vitamin is discussed.     

Torsion and Antero-Posterior Bending in the In Vivo Human Tibia Loading Regimes during Walking and Running

Bending, in addition to compression, is recognized to be a common loading pattern in long bones in animals. However, due to the technical difficulty of measuring bone deformation in humans, our current understanding of bone loading patterns in humans is very limited. In the present study, we hypothesized that bending and torsion are important loading regimes in the human tibia. In vivo tibia segment deformation in humans was assessed during walking and running utilizing a novel optical approach. Results suggest that the proximal tibia primarily bends to the posterior (bending angle: 0.15°–1.30°) and medial aspect (bending angle: 0.38°–0.90°) and that it twists externally (torsion angle: 0.67°–1.66°) in relation to the distal tibia during the stance phase of overground walking at a speed between 2.5 and 6.1 km/h. Peak posterior bending and peak torsion occurred during the first and second half of stance phase, respectively. The peak-to-peak antero-posterior (AP) bending angles increased linearly with vertical ground reaction force and speed. Similarly, peak-to-peak torsion angles increased with the vertical free moment in four of the five test subjects and with the speed in three of the test subjects. There was no correlation between peak-to-peak medio-lateral (ML) bending angles and ground reaction force or speed. On the treadmill, peak-to-peak AP bending angles increased with walking and running speed, but peak-to-peak torsion angles and peak-to-peak ML bending angles remained constant during walking. Peak-to-peak AP bending angle during treadmill running was speed-dependent and larger than that observed during walking. In contrast, peak-to-peak tibia torsion angle was smaller during treadmill running than during walking. To conclude, bending and torsion of substantial magnitude were observed in the human tibia during walking and running. A systematic distribution of peak amplitude was found during the first and second parts of the stance phase.     

Ischemia–Reperfusion Injury of Sciatic Nerve in Rats: Protective Role of Combination of Vitamin C with E and Tissue Plasminogen Activator

An ischemia/reperfusion injury of rat’s sciatic nerve was experimentally developed. In this model, we measured the in vivo production of superoxide radical, as a marker of oxidative stress and the occludin expression as an indicator of blood-nerve barrier function and we examined potential protective innervations against these abnormalities. Right sciatic nerves of the animals underwent 3 h of ischemia followed by 7 days of reperfusion and were divided into three groups: ischemic, pretreated with vitamin C in conjunction with vitamin E and treated with tissue plasminogen activator. Compared to measurements from left sciatic nerves used as sham, the ischemic group showed significantly increased superoxide radical and reduced expression of occludin in western blot and immunohistochemistry. No such differences were detected between sham and nerves in the vitamin or tissue plasminogen activator groups. It is suggested that the experimental ischemia/reperfusion model was suitable for studying the relationship between oxidative state and blood-nerve barrier. The reversion of abnormalities by the applied neuroprotective agents might prove to be a clinically important finding in view of the implication of vascular supply derangement in various neuropathies in humans.     

Bone marrow levels of 25 hydroxy vitamin D are not depressed in cases of hip fracture compared with controls

There is little information on tissue as distinct from plasma levels of vitamin D metabolites in cases of hip fracture compared with controls. Femoral neck fractures in the elderly are associated with increased cortical remodelling and endosteal resorption, leading to regional increases in porosity and reduced cortical thickness. Vitamin D metabolites play a central role in the maintenance of normal serum calcium levels and may, through interactions with parathyroid hormone, exert an important influence on bone structure. To investigate whether hip fracture might be associated with tissue vitamin D deficiency, we have measured by radioimmunoassay the levels of 25 hydroxy vitamin D (25 (OH)D) in bone marrow samples extracted from the proximal femurs of 16 female subjects who had suffered fracture (mean age = 82.1 years, standard error (se) 1.9) and nine sex matched post mortem controls (mean age = 83.8 years, se 2.5). Twenty five (OH)D concentrations were significantly greater in the fracture cases (median = 3.7, IQR = 2.5–3.9 ng/g) than in the control group (median = 1.5, IQR = 0.9–2.3 ng/g; P = 0.0007, non‐parametric Wilcoxon/Kruskal–Wallis test). It was suggested in the 1970s that bone loss and hip fracture risk in the UK were driven by vitamin D deficiency. Our results suggest that the alterations in femoral neck bone microstructure and remodelling in hip fracture cannot be assigned to the single cause of relative deficiency of vitamin D. Vitamin D deficiency or insufficiency may nevertheless increase remodelling and loss of bone tissue and contribute causally to a minority of hip fractures. Copyright © 2013 John Wiley & Sons, Ltd.     

Effects of vitamin D3 on the uptake and release of calcium by isolated intestinal mitochondria

Administration of vitamin D3 or 1,25 (OH)2D3 to rachitic chicks produces a decrease of 45Ca uptake by mitochondria from intestinal mucosa. This effect of vitamin D3 shows tissue specificity, since it was not observed in liver mitochondria from the same animals. The Km values were similar (about 10 microM) for intestinal mitochondria from rachitic and treated animals. The Ca2+ efflux in previously loaded mitochondria was not changed by treatment. The Ca content of recently isolated mitochondria was strikingly lower after vitamin D3 administration. It is concluded that vitamin D3 may participate in the mechanism which regulates the intramitochondrial Ca concentration.     

Design and validation of a testing system to assess torsional cancellous bone failure in conjunction with time-lapsed micro-computed tomographic imaging

When compressed axially, cancellous bone often fails at an oblique angle along well-defined bands, highlighting the importance of cancellous bone shear properties. Torsion testing to determine shear properties of cancellous bone has often been conducted under conditions appropriate only for axis-symmetric specimens comprised of homogeneous and isotropic materials. However, most cancellous bone specimens do not meet these stringent test conditions. Therefore, the aim of this study was to design and validate a uniaxial, incremental torsional testing system for non-homogeneous orthotropic or non-axis-symmetric specimens.Precision and accuracy of the newly designed torsion system was validated by using Plexiglas rods and beams, where obtained material properties were compared to those supplied by the manufacturer. Additionally, the incremental step-wise application of angular displacement and simultaneous time-lapsed μCT imaging capability of the system was validated using whale cancellous bone specimens, with step-wise application of angular displacement yielding similar torsional mechanical properties to continuous application of angular displacement in a conventional torsion study.In conclusion, a novel torsion testing system for non-homogeneous, orthotropic materials using the incremental step-wise application of torsion and simultaneous time-lapsed μCT imaging was designed and validated.     

Alfacalcidol restores cancellous bone in ovariectomized rats

Active vitamin D metabolites have been demonstrated to reduce vertebral and hip fractures in elderly patients. A number of in vitro and in vivo pre-clinical studies have suggested that vitamin D may effectively stimulate osteoblastic activity and exert an anabolic effect on bone. The current study was designed to further explore the ability of an active vitamin D analog to restore bone in a skeletal site with established osteopenia in ovariectomized (OVX) rats. Female Sprague Dawley rats at five months of age and 8 weeks after sham ovariectomy or ovariectomy were randomly divided into 7 groups with 10 per group. At the beginning of the treatments, one group of sham-operated rats and one group of OVX rats were sacrificed to serve as baseline controls. Another group of sham-operated rats and one group of OVX rats were treated with vehicle for 4 weeks. The OVX rats in the remaining groups were treated with alfacalcidol at 0.05, 0.1 or 0.2 microg/kg/d by daily oral gavage, 5 days/week for 4 weeks. As expected, estrogen depletion caused high bone turnover and cancellous bone loss in lumbar vertebra of OVX rats. Alfacalcidol treatment at 0.1 or 0.2 but not 0.05 microg/kg/d increased serum calcium and phosphorus in OVX rats as compared with vehicle treatment. In addition, serum parathyroid hormone was suppressed, whereas serum osteocalcin was increased by alfacalcidol at all dose levels. Furthermore, histomorphometric data of 2nd lumbar vertebral body revealed that cancellous bone volume in OVX rats treated with alfacalcidol at 0.1 or 0.2 microg/kg/d was increased to the level of sham-operated rats treated with vehicle. This increment in cancellous bone mass was accompanied by increases in trabecular number and thickness and a decrease in trabecular separation. Moreover, osteoclast surface and number were significantly decreased, whereas bone formation variables such as mineralizing surface and bone formation rate were significantly increased in alfacalcidol- treated OVX rats compared with those of vehicle-treated OVX rats. Finally, a linear regression analysis showed that alfacalcidol treatment dose-dependently altered most of the variables measured in the current study. In conclusion, alfacalcidol completely restores cancellous bone by stimulating bone formation and suppressing bone resorption in lumbar vertebra of OVX rats when the treatment is started at an early phase of osteopenia. The evidence of increased bone formation by alfacalcidol treatments further supports the notion that active vitamin D metabolites or their analogs may exert anabolic effects on bone.     

Effects of Multi-Deficiencies-Diet on Bone Parameters of Peripheral Bone in Ovariectomized Mature Rat

Many postmenopausal women have vitamin D and calcium deficiency. Therefore, vitamin D and calcium supplementation is recommended for all patients with osteopenia and osteoporosis. We used an experimental rat model to test the hypothesis that induction of osteoporosis is more efficiently achieved in peripheral bone through combining ovariectomy with a unique multi-deficiencies diet (vitamin D depletion and deficient calcium, vitamin K and phosphorus). 14-week-old Sprague-Dawley rats served as controls to examine the initial bone status. 11 rats were bilaterally ovariectomized (OVX) and fed with multi-deficiencies diet. Three months later the treated group and the Sham group (n = 8) were euthanized. Bone biomechanical competence of the diaphyseal bone was examined on both, tibia and femur. Image analysis was performed on tibia via µCT, and on femur via histological analysis. Lower torsional stiffness indicated inferior mechanical competence of the tibia in 3 month OVX+Diet. Proximal metaphyseal region of the tibia showed a diminished bone tissue portion to total tissue in the µCT despite the increased total area as evaluated in both µCT and histology. Cortical bone showed higher porosity and smaller cross sectional thickness of the tibial diaphysis in the OVX+Diet rats. A lower ALP positive area and elevated serum level of RANKL exhibited the unbalanced cellular interaction in bone remodeling in the OVX+Diet rat after 3 month of treatment. Interestingly, more adipose tissue area in bone marrow indicated an effect of bone loss similar to that observed in osteoporotic patients. Nonetheless, the presence of osteoid and elevated serum level of PTH, BGP and Opn suggest the development of osteomalacia rather than an osteoporosis. As the treatment and fracture management of both osteoporotic and osteomalacia patients are clinically overlapping, this study provides a preclinical animal model to be utilized in local supplementation of minerals, drugs and growth factors in future fracture healing studies.     

Influence of phase angle between axial and torsional loadings on fatigue fractures of bone

Fatigue fractures of cortical bone involve combined axial-torsional loading yet it is unknown how the relationship between axial and torsional loadings affects the fatigue behavior of bone. In this study the effect of superimposing in-phase and out-of-phase torsional on axial loading on the fatigue behavior of bone was investigated by conducting in vitro tests involving 0 degrees and 90 degrees phase shift between cyclic torsional and axial loadings. Results obtained indicate that fatigue life, patterns of moduli loss, microcracking and modes of fractures are dependent on the phase angle between axial and torsional loadings. Specimens subjected to in-phase torsional on axial loading demonstrated greater mixed mode interaction, underwent proportionate stiffness losses in tension, compression, and torsion, and consequently had a shorter fatigue life. In contrast, specimens subjected to out-of-phase loading regime displayed a smaller contribution of mixed mode failure, underwent a disproportionately large stiffness loss in torsion, and had a longer fatigue life. Furthermore, increase in phase angle provided additional planes on which damage was diffused delaying the final failure. Change in phase angle, seen in vivo during a number of physiological activities including walking, running and sprinting, will therefore affect fatigue behavior and contribute to pathogenesis of fatigue fractures.     

Noncollagenous bone proteins in experimental rickets in the rat

Rats were raised in the absence of vitamin D in utero and throughout post-fetal life and neither 1,25-dihydroxyvitamin D3 nor related metabolites were detected in serums. No changes were observed in the relative amount of extractable noncollagenous bone proteins (NCP) in rachitic compared to vitamin-D-repleted animals. As expected, the relative levels of the mineral-bound, serum-derived albumin and 2-HS glycoprotein were unaffected in bones of rachitic animals. Interestingly, the vitamin D deficiency also did not have dramatic effects on several bone cell-derived noncollagenous proteins including: bone proteoglycans I & 11, bone sialoprotein li osteonectin, and osteocalcin. In contrast to the proteoglycans, the bone sialoprotein II and osteonectin were found in the nonmineral compartment of the rachitic animals, presumably bound to the wide osteoid seam.     

Vitamin K therapy for cortical bone fragility caused by reduced mechanical loading in a child with hemiplegia

Fractures frequently occur at cortical bone sites in children with cerebral palsy, but there is no established therapy. We previously found that treatment with vitamins D and K increased cortical bone mass in children with severe physical disability, and have hypothesized that vitamin K could play a significant role in pediatric cortical bones under conditions with reduced mechanical loading. In the present case report, we treated a right hemiplegic ambulant eight-year-old boy with oral vitamin K (15 mg per day) for eight months. Cortical bone geometries at mid-diaphyseal sites in bilateral tibiae were evaluated before and after the treatment. The cross-sectional total, bone and marrow areas of non-hemiplegic tibia increased by 8.8%, 7.4% and 12.0%, respectively, while those of hemiplegic tibia changed by 9.0%, 14.9% and -3.4%, respectively. As a result, the polar moment of inertia, an indicator of the resistance to torsion forces, increased by 13.0% in the non-hemiplegic tibia and by 63.7% in the hemiplegic tibia. Vitamin K may restrict cortical bone fragility, caused by reduced mechanical loading, through its actions at the endosteal bone marrow interface. Further studies are needed to confirm these findings and to clarify the mechanisms involved.     

Metabolic profiling of vitamin C deficiency in Gulo?/? mice using proton NMR spectroscopy

Nutrient deficiencies are an ongoing problem in many populations and ascorbic acid is a key vitamin whose mild or acute absence leads to a number of conditions including the famously debilitating scurvy. As such, the biochemical effects of ascorbate deficiency merit ongoing scrutiny, and the Gulo knockout mouse provides a useful model for the metabolomic examination of vitamin C deficiency. Like humans, these animals are incapable of synthesizing ascorbic acid but with dietary supplements are otherwise healthy and grow normally. In this study, all vitamin C sources were removed after weaning from the diet of Gulo-/- mice (n?=?7) and wild type controls (n?=?7) for 12?weeks before collection of serum. A replicate study was performed with similar parameters but animals were harvested pre-symptomatically after 2-3?weeks. The serum concentration of 50 metabolites was determined by quantitative profiling of 1D proton NMR spectra. Multivariate statistical models were used to describe metabolic changes as compared to control animals; replicate study animals were used for external validation of the resulting models. The results of the study highlight the metabolites and pathways known to require ascorbate for proper flux.     

Comparison between Different Methods for Biomechanical Assessment of Ex Vivo Fracture Callus Stiffness in Small Animal Bone Healing Studies

For ex vivo measurements of fracture callus stiffness in small animals, different test methods, such as torsion or bending tests, are established. Each method provides advantages and disadvantages, and it is still debated which of those is most sensitive to experimental conditions (i.e. specimen alignment, directional dependency, asymmetric behavior). The aim of this study was to experimentally compare six different testing methods regarding their robustness against experimental errors. Therefore, standardized specimens were created by selective laser sintering (SLS), mimicking size, directional behavior, and embedding variations of respective rat long bone specimens. For the latter, five different geometries were created which show shifted or tilted specimen alignments. The mechanical tests included three-point bending, four-point bending, cantilever bending, axial compression, constrained torsion, and unconstrained torsion. All three different bending tests showed the same principal behavior. They were highly dependent on the rotational direction of the maximum fracture callus expansion relative to the loading direction (creating experimental errors of more than 60%), however small angular deviations (<15°) were negligible. Differences in the experimental results between the bending tests originate in their respective location of maximal bending moment induction. Compared to four-point bending, three-point bending is easier to apply on small rat and mouse bones under realistic testing conditions and yields robust measurements, provided low variation of the callus shape among the tested specimens. Axial compressive testing was highly sensitive to embedding variations, and therefore cannot be recommended. Although it is experimentally difficult to realize, unconstrained torsion testing was found to be the most robust method, since it was independent of both rotational alignment and embedding uncertainties. Constrained torsional testing showed small errors (up to 16.8%, compared to corresponding alignment under unconstrained torsion) due to a parallel offset between the specimens’ axis of gravity and the torsional axis of rotation.     

Regulation of the vitamin D receptor and cornifin beta expression in vaginal epithelium of the rats through vitamin D3

The aim of the present study was to determine the respective role of 1,25-dihydroxyvitamin D3 on vaginal epithelium and 1,25-dihydroxyvitamin D3 receptor expression in ovariectomized rats and vitamin D3 treated rats. Bilateral ovariectomies were performed in 20 mature, non-pregnant Wistar female rats. All the animals were divided into 2 groups consisting of 10 rats each. Group I served as control. In group II, animals were injected intramuscularly with vitamin D3 (50, 00 IU/kg). Two weeks after the injections, vaginas of animals in group I and group II were removed removed and processed for immunohistochemistry. Epithelial differentiation, 1,25-dihydroxyvitamin D3 receptor and cornifin beta expression were investigated in vaginal epithelium of control group (ovariectomized) and vitamin D3 treated rats. Vaginal epithelial cells from vitamin D3 treated animals changed into highly- stratified keratinizing layers. 1,25-dihydroxyvitamin D3 receptor and cornifin beta as a marker of squamous differentiation were present in ovariectomized rats treated with 1,25-dihydroxyvitamin D3. In contrast, cornifin beta and 1,25-dihydroxyvitamin D3 receptor were absent in all layers of vaginal epithelium in control group. We demonstrated for the first time that 1,25-dihydroxyvitamin D3 induced proliferation of vaginal epithelium consistent with the cornifin beta expression and 1,25-dihydroxyvitamin D3 up-regulated 1,25-dihydroxyvitamin D3 receptor expression in vaginal epithelium.     

The biomechanical effect of torsion on humeral shaft repair techniques for completed pathological fractures

In the presence of a tumor defect, completed humeral shaft fractures continue to be a major surgical challenge since there is no "gold standard" treatment. This is due, in part, to the fact that only one prior biomechanical study exists on the matter, but which only compared 2 repair methods. The current authors measured the humeral torsional performance of 5 fixation constructs for completed pathological fractures. In 40 artificial humeri, a 2-cm hemi-cylindrical cortical defect with a transverse fracture was created in the lateral cortex. Specimens were divided into 5 different constructs and tested in torsion. Construct A was a broad 10-hole 4.5-mm dynamic compression plate (DCP). Construct B was the same as A except that the screw holes and the tumor defect were filled with bone cement and the screws were inserted into soft cement. Construct C was the same as A except that the canal and tumor defect were filled with bone cement and the screws were inserted into dry cement. Construct D was a locked intramedullary nail inserted in the antegrade direction. Construct E was the same as D except that bone cement filled the defect. For torsional stiffness, construct C (4.45 ± 0.20 Nm/deg) was not different than B or E (p > 0.16), but was higher than A and D (p < 0.001). For failure torque, construct C achieved a higher failure torque (69.65 ± 5.35 Nm) than other groups (p < 0.001). For the failure angle, there were no differences between plating constructs A to C (p ≥ 0.11), except for B versus C (p < 0.05), or between nailing groups D versus E (p = 0.97), however, all plating groups had smaller failure angles than both nailing groups (p < 0.05). For failure energy, construct C (17.97 ± 3.59 J) had a higher value than other groups (p < 0.005), except for A (p = 0.057). Torsional failure always occurred in the bone in the classic "spiral" pattern. Construct C provided the highest torsional stability for a completed pathological humeral shaft fracture.     

Administration of 1 alpha-OH vitamin D3 and calcium prevents bone mass loss in patients with advanced prostatic carcinoma after orchidectomy treated with complete androgenic blockade

Complete androgenic blockade used in the treatment of advanced prostatic carcinoma can be attained by administration of antiandrogens in orchidectomized patients or by combined therapy with LH-RH analogs and antiandrogens. The treatment, however, decreases the influence of both androgens end estrogens on bone tissue and may result in bone mass loss and increased propensity to fractures. The purpose of the study was to determine the influence of complete androgenic blockade on bone mass and skeletal metabolism in men with advanced prostatic carcinoma and to assess whether 1alpha-OH vitamin D3 (1alpha-OHD3) together with calcium supplementation is able to prevent bone mass loss in men treated with complete androgenic blockade. 51 patients with advanced prostatic carcinoma, with skeletal metastases, aged 44 - 86, mean 68 ys were included into a 12-month prospective study. All patients were treated with orchidectomy followed by therapy with flutamide in a dose of 750 mg daily. 26 patients were additionally given 1alpha-OHD3 in a dose of 0.5 microg/d and calcium carbonate in an initial dose of 1 g daily. It was found that the 12-month treatment with complete androgenic blockade resulted in a decrease in bone mineral density (BMD) by 8.1% in the lumbar spine, by 6.3% in the femoral neck and by 3.5% in the total skeleton. Therapy with 1alpha-OHD3 and CaCO3 caused complete inhibition of bone tissue loss in the lumbar spine and resulted in an increase in BMD by 2.2% in femoral neck and by 1.9% in the total skeleton. None of the examined patients experienced any skeletal fractures. In both groups of patients a prompt decrease in serum alkaline phosphatase activity - a marker of osteoblast activity and an increase in fasting urine calcium creatinine ratio indicating acceleration of bone resorption were found. Conclusions: in patients with advanced prostatic carcinoma treated with complete androgenic blockade acceleration of bone mass loss is observed; treatment with 1alpha-OHD3 and CaCO3 is able to prevent both trabecular and compact bone loss.     

In vivo and in vitro inhibition of rat liver vitamin D3-25-hydroxylase activity by 19-hydroxy-10(S),19-dihydrovitamin D3

Rats treated with varying amounts of 19-hydroxy-10(S),19-dihydrovitamin D3 prior to administration of physiologic doses of vitamin D3 exhibit normal intestinal calcium transport but are unable to mobilize bone calcium. In contrast, 19-hydroxy-10(R),19-dihydrovitamin D3 had no inhibitory activity. Circulating serum levels of 25-hydroxy[3H]vitamin D3 and 1 alpha, 25-dihydroxy[3H]vitamin D3 are markedly suppressed but not totally eliminated in animals predosed with 19-hydroxy-10(S),19-dihydrovitamin D3 before [3H]vitamin D3. Hepatic 25-hydroxy[3H]vitamin D3 levels were approximately equal in both 19-hydroxy-10(S),19-dihydroviotamin D3 treated and untreated rats. However, the rate of conversion of [3H]vitamin D3 to 25-hydroxyvitamin D3 in vivo is greatly reduced in the treated rats. The inhibitory vitamin analogue was also show to block hepatic microsomal 25-hydroxylation in vitro. These results indicate that 19-hydroxy-10(S),19-dihydrovitamin D3 is a specific inhibitor for a hepatic microsomal vitamin D3-25-hydroxylase system.     

Assessing vitamin D status of callitrichids: Baseline data from wild cotton-top tamarins (Saguinus oedipus) in Colombia

Bone disease related to vitamin D deficiency is an insidious problem in captive colonies of callitrichids. Currently a diagnosis of vitamin D deficiency may be made after the appearance of clinical pathology, usually bone deformities or fractures. The development of assays for vitamin D metabolites suggests it may be possible to detect incipient vitamin D deficiency before animals are adversely affected. However, there are few data on normative levels of these metabolites in any nonhuman primates. We collected blood samples from 18 wild cotton-top tamarins (Saguinus oedipus) from Colombia and assayed them for 25-hydroxy vitamin D(25-OH-D), the major circulating form of the vitamin, which is believed to be a good indicator of status. Serum concentrations of 25-OH-D averaged 76.4 ng/ml (range 25.5–120 ng/ml). This is high compared with human norms (10–55 ng/ml), but the range is lower than that reported in the literature for captive callitrichids. Juveniles had higher serum concentrations than did adults, and pregnant females had lower concentrations than did nonpregnant females. These data confirm that healthy callitrichids have higher circulating levels of 25-OH-D than do humans, but they suggest that the extremely high levels found in some captive animals (300–600 ng/ml) may be above normal. We propose that serum concentrations of 25-OH-D of 50–120 ng/ml can be considered normal for cotton-top tamarins and perhaps other callitrichids. If serum values much below 50 ng/ml are found during clinical evaluation, the possibility of incipient vitamin D deficiency should be considered. Zoo Biol 16:39–46, 1997. © 1997 Wiley-Liss, Inc.