The Tensile Properties and Microstructure of Ti-Tic Composites with Al Additions

The relationship between the tensile properties and microstructure of Ti-TiC composite materials with Al additions was investigated. Composites containing 40–50% TiC by volume were produced using standard casting procedures from the melt. Ultimate tensile strengths of 1113 MPa with 1–2 % ductility were found in these materials. Results show that the tensile properties are controlled by the size and distribution of TiC particles.

The receptor activator of nuclear factor-kappaB ligand inhibitor osteoprotegerin is a bone-protective agent in a rat model of chronic renal insufficiency and hyperparathyroidism

Osteoprotegerin (OPG) acts by neutralizing the receptor activator of nuclear factor-kappaB ligand (RANKL), the primary mediator of osteoclast differentiation, function, and survival. We examined whether OPG could affect the bone loss associated with chronic kidney disease (CKD) in a rodent model of CKD and secondary hyperparathyroidism (SHPT). SHPT was induced in rats by 5/6 nephrectomy (5/6 Nx) and a 1.2% P/0.6% Ca(2+) diet. Starting 1 week after 5/6 Nx, rats were treated with vehicle (veh) or OPG-Fc (3 mg/kg, intravenously) every 2 weeks for 9 weeks. At baseline, 3, 6, and 9 weeks, blood was taken and bone mineral density (BMD) and bone mineral content (BMC) were assessed by dual-energy X-ray absorptiometry. Serum parathyroid hormone (sPTH) levels reached 912 pg/ml in 5/6 Nx rats vs. 97 pg/ml in shams at 9 weeks. OPG-Fc had no effect on sPTH or Ca(2+) levels throughout the 9-week study, indicating that SHPT was a renal effect independent of bone changes. At 3 weeks, 5/6 Nx-veh rats had osteopenia compared with sham-veh rats and 5/6 Nx-OPG-Fc rats had significantly higher percent changes in whole-body BMC, leg BMD, and lumbar BMD versus 5/6 Nx-veh rats. By 6-9 weeks, elevated sPTH was associated with reversal of bone loss and osteitis fibrosa in the proximal tibial metaphysis. OPG-Fc decreased this sPTH-driven high bone turnover, resulting in augmented thickness of proximal tibial trabeculae in 5/6 Nx rats. Thus, RANKL inhibition with OPG-Fc can block the deleterious effects of continuously elevated sPTH on bone, suggesting that RANKL may be an important therapeutic target for protecting bone in patients with CKD and SHPT.

Characterization of fouled membranes from a membrane enhanced biological phosphorus removal system

Characterization of fouled membranes is the first step towards a good understanding of membrane fouling nature and thus formulating effective engineering measures for fouling prevention and control. In this study, fouled membrane fibres collected from a pilot scale membrane enhanced biological phosphorus removal (MEBPR) process were systematically examined. Several analytical tools, including scanning electron microscopy (SEM), conventional optical microscopy (COM), energy dispersive X-ray (EDX) microanalysis, matrix assisted laser desorption/ionization--mass spectrometry (MALDI-MS) analysis, and conventional chemical analysis techniques were used. The results indicated that membrane fouling in the MEBPR process was mainly of an organic nature, and most extractable foulants were carbohydrates and humic or humic-like substances. Unlike in other wastewater treatment membrane bioreactors, microbial growth on fouled membranes was not substantial, probably due to the vigorous aeration applied and the strong hydrodynamic conditions within the membrane pore structure. After a period of sludge filtration, membrane surfaces became more hydrophobic and the resultant hydrophobic interactions between the fouled membranes and mixed liquor constituents might have accelerated the fouling process.

CD4+CD45RBHi T cell transfer induced colitis in mice is accompanied by osteopenia which is treatable with recombinant human osteoprotegerin

BACKGROUND AND AIMS

Transfer of CD4+CD45RBHi T cells into semi syngeneic immunodeficient mice represents a model of inflammatory bowel disease (IBD). As patients with IBD often suffer from osteopenia, we studied if this T cell transfer in mice results in osteopenia in addition to colitis, and if treatment with osteoprotegerin (OPG) has effects on the bone mineral density of T cell transferred mice. We also investigated whether osteopenia was due to malabsorption as a result of a dysregulated digestive tract or as a consequence of the inflammatory process.

METHODS

CD4+CD45RBHi or CD4+CD45RBLo T cells (4 x 10(5)) were sorted from CB6F1 and transferred into C.B.17 scid/scid mice. Recipient mice were treated with human IgG1 Fc (control) or Fc-OPG three times per week in a prophylactic regimen as well as a therapeutic regimen (after 10% body weight loss) and were evaluated for osteopenia and colitis.

RESULTS

Mice that received CD4+CD45RBHi T cells developed osteopenia (as indicated by decreased bone density accompanied by decreased osteoblasts and increased osteoclasts) and colitis (as indicated by histological changes in the large intestine). Mice that received CD4+CD45RBLo T cells developed neither osteopenia nor colitis. All animals consumed, on average, the same amount of food and water over the course of the study. Prophylactic treatment with Fc-OPG increased bone density in mice that received either CD4+CD45RBHi or CD4+CD45RBLo T cells but had no effects on the gastrointestinal tract. Fc-OPG treatment of osteopenic mice with established IBD caused the normalisation of bone density. Osteopenia in CD4+CD45RBHi T cell recipients was accompanied by hypoparathyroidism that was partially normalised by treatment with Fc-OPG. CD4+CD45RBHi T cell recipients also had a bone marrow inflammatory cell infiltrate expressing tumour necrosis factor alpha which was unaffected by treatment with Fc-OPG.

CONCLUSIONS

CD4+CD45RBHi T cell transfer results in osteopenia in addition to colitis. Evidence suggests that this osteopenia was induced by inflammatory cell infiltration and not by malabsorption of calcium. Recombinant human osteoprotegerin effectively treated the osteopenia. OPG may be a useful therapeutic option for treating osteopenia in patients with IBD.

Structure characterization of human RalGDS gene, and the identification of its novel variant

RalGDS is a guanine nucleotide dissociation stimulator for Ral, which is a member of the Ras GTPase superfamily that regulates cellular proliferation, differentiation and transformation by mediating multiple signal transduction pathways. RalGDS can specifically promote the conversion from an inactive GDP-bound state to an active GTP-bound state for Ral. The cDNA of human RalGDS has been cloned recently. In this paper, by comparison between the gene's genomic and cDNA seqence, we determined the structure of the gene, which showed that the reported human RalGDS transcribed from 18 exons. Furthermore, a novel variant of RalGDS that codes for a protein with a different N-terminus was cloned and identified. Northern hybridization revealed that the novel transcript was of 6.0 kb in length while the transcript previously reported is of 4.0 kb. Both transcripts were ubiquitously expressed in human adult tissues examined, albeit with different amounts. In addition, this novel transcript was proved to be caused by employment of a new exon, designated as exon 1a, instead of the one, designated as exon 1b, in the reported cDNA. Thus, the RalGDS gene consists of at least 19 exons and spanned a 44 kb region. The length between exon 1a and exon 2 was 33 kb, while the length between exon 1b and exon 2 was 8.8 kb.

CD40/154 blockade and rejection of islet allografts in the streptozotocin and autoimmune diabetic rat

Islet transplantation in children with autoimmune diabetes will require immunosuppression that has minimal toxicity and side-effects, and overcomes the barrier of autoimmunity. Since antibodies directed against the CD40/154 co-stimulatory pathway may meet these criteria, we have tested the ability of hamster antirat CD154 (AH.F5, Biogen) to prevent rejection of renal subcapsular islet allografts in streptozotocin (STZ) or autoimmune (AUTO) diabetic diabetes-resistant biobreeding (DRBB) rats. STZ diabetic rats that received anti-CD154 at 15 mg/kg per dose but not 10 mg/kg per dose did not have evidence of rejection until about 80-120 d post-transplantation, by which time antibody concentrations had returned to undetectable levels. Rats retreated with anti-CD154 before recurrence of diabetes had a prolonged period of disease-free survival. Most of these rats had recurrence following a spleen cell challenge. In contrast, AUTO diabetic DRBB rats treated with anti-CD154 had recurrence of diabetes between 7 and 12 d following transplantation of the Dark Agouti (DA) islets. In a separate set, AUTO diabetic rats that received a simultaneous islet isograft, islet allograft and thyroid allograft had focal accumulation of lymphocytes at the periphery of the isograft, while the islet and thyroid allografts had diffuse infiltration with lymphocytes and destruction of tissue with no residual staining for glucagon. Therefore, autoimmunity adds an additional barrier to islet allotransplantation that is not overcome with CD40/154 blockade in an animal model that closely parallels autoimmune diabetes in humans. The results indicate the importance of testing regimen of islet transplantation in animal models of autoimmune diabetes.

Improved assessment of bone turnover by the PTH-(1-84)/large C-PTH fragments ratio in ESRD patients

BACKGROUND

The "intact" parathyroid hormone (PTH) assay recognizes PTH-(1-84) as well as amino terminally truncated PTH fragments, that is, large carboxyterminal PTH fragments (C-PTH fragments). The present study investigated whether the use of the plasma PTH-(1-84)/C-PTH fragment ratio enhances the noninvasive assessment of bone turnover in patients on dialysis.

METHODS

Bone biopsies and blood samples for determinations of routine indices of bone turnover and PTH peptides were obtained in 51 adult patients on dialysis not treated with drugs affecting bone such as vitamin D or corticosteroids. Blood levels of large C-PTH fragments were calculated by subtracting PTH-(1-84) from "intact" PTH. Patients were classified according to their levels of bone turnover based on histomorphometrically obtained results of activation frequency. Prediction of bone turnover by the various blood indices was done by using proper statistical methods. In addition, hypercalcemia was induced by calcium gluconate infusion in a subset of patients, and levels of PTH-(1-84), "intact" PTH, and PTH-(1-84)/C-PTH fragment ratio were determined.

RESULTS

The PTH-(1-84)/C-PTH fragment ratio was the best predictor of bone turnover. A ratio> 1 predicted high or normal bone turnover (sensitivity 100%), whereas a ratio <1 indicated a high probability (sensitivity 87.5%) of low bone turnover. Calcium infusion resulted in decrease in PTH-(1-84)/C-PTH fragment ratio.

CONCLUSIONS

The PTH-(1-84)/C-PTH fragment ratio predicts bone turnover with acceptable precision for biological measurements. Moreover, a change in serum calcium levels is one of the regulators of the relative amount of circulating PTH-(1-84) and its large C-PTH fragments.

Preliminary study of three-tone paradigm auditory P300 on aging dementia

OBJECTIVE

To explore the changes of three-tone paradigm P300 and observe the improvement of the diagnostic sensitivity of P300 in aging dementia.

METHODS

Thirty-four patients of aging dementia underwent traditional P300 (2t-P300) and three-tone paradigm auditory P300 (3t-P300). The results of these two methods were compared.

RESULTS

Abnormal P300 was found in 18 of 34 dementia cases (52.9%) by 2t-P300, and in 26 of 30 patients who finished the 3t-P300 tests (86.7%). In 2t-P300, 9 of 24 mild cases, 7 of 8 moderate cases and 2 severe cases showed abnormal results. In 3t-P300, 20 of 24 mild cases and all 6 moderate cases showed abnormal results. Abnormal 3t-P300 was found in 13 of 16 cases which showed normal 2t-P300. Besides prolonged and bad-shaped P300, no certain response of P300 to rare non-target stimulus (r-nT) was found in 10 mild cases by 3t-P300.

CONCLUSION

Three-tone paradigm auditory P300 had higher sensitivity in early diagnosis of aging dementia than traditional auditory P300. No P300 response to r-nT in 3t-P300 is an important index in early diagnosis of mild dementia.

[Synthesis and ultraviolet-visible spectrum of two new symmetrical porphyrins]

Meso-tetra(p-benzoylaminophenyl) porphyrin or meso-tetra (o-benzoylaminophenyl) porphyrin are synthesized by condensation of meso-tetra (p-aminophenyl) porphyrin or meso-tetra (o-aminophenyl) porphyrin and benzoyl chloride in DMF using NaOH as catalyst, these porphyrins and the method have not been reported previously. Their structures are ascertained by elemental analysis, ultraviolet-visible spectrum, IR and 1H-NMR measurements. The ultraviolet-visible spectrum of the two porphyrins is discussed in detail.

[Study on the association of pathologic myopia with HLA-DQB1 gene]

OBJECTIVE

To investigate the association of pathologic myopia (PM) with HLA-DQB1 alleles in order to study the pathogenesis of PM.

METHODS

The genome DNA of 66 patients with PM was extracted from the blood. The second exon of the HLA-DQB1 gene was amplified by polymerase chain reaction (PCR), and individual PCR products were digested by allele specific restriction enzymes of Hae III, BssH II, Apa I, BsaH I, Hae II, Hpa II, Rsa I, Bsp 1286 I for typing. Genotype was determined by restriction fragment length polymorphism (RFLP) pattern. The frequency of 16 alleles of HLA-DQB1 was detected and compared with that of the healthy control.

RESULTS

The frequencies of HLA-DQB1 * 0301 and * 0303 were significantly higher in the patients with PM (P < 0.0001), while that of HLA-DQB1 * 0601 and * 0602 were significantly lower (P < 0.0001) than that of the control group.

CONCLUSION

HLA-DQB1 * 0301, * 0303 alleles are susceptible alleles, and possibly they are the pathogenic genes, * 0601, * 0602 are resistant alleles, and may be they possess the protective property.

Tandem conjugate reduction-aldol cyclization using Stryker's reagent

[see reaction]. Conjugate reduction by Stryker's reagent to form copper enolates, followed by intramolecular aldol cyclization, successfully generated five- and six-membered carbocycles in one pot efficiently. This tandem reaction is generally diastereoselective and provides good yields of the beta-hydroxyketones without any dehydration at low temperatures.

Parathyroid hormone/parathyroid hormone-related peptide type 1 receptor in human bone

The parathyroid hormone/parathyroid hormone-related peptide (PTH/PTHrP) receptor (denoted as PTH-1R) is a key signaling factor through which calcium-regulating hormones PTH and PTHrP exert their effects on bone. There are contradictory reports regarding the capability of osteoclasts to express PTH-1R. To address this issue in humans, bone biopsy specimen samples from 9 normal controls and 16 patients with moderate to severe secondary renal hyperparathyroid bone disease (2 degrees HPT) with elevated PTH levels were studied to determine whether osteoclasts in the bone microenvironment express PTH-1R messenger RNA (mRNA) and protein. We report that osteoclasts express the PTH-1R mRNA but the protein is detected only in patients with 2 degrees HPT. The PTH-1R mRNA and protein also were found in osteoblasts, osteocytes, and bone marrow cells. Receptor expression was higher in osteoclasts and osteoblasts of patients with 2 degrees HPT than normal controls (98.0 +/- 1.1% vs. 65.7 +/- 14.3% and 65.8 +/- 3.4% vs. 39.1 +/- 6.2%; p < 0.01, respectively). Approximately half of osteoclasts found in bone of patients with 2 degrees HPT have the PTH-1R protein. In patients with 2 degrees HPT, a positive relationship exists between erosion depth, a parameter of osteoclastic activity, and the percentage of osteoclasts with PTH-1R protein (r = 0.58; p < 0.05). In normal controls, an inverse relationship exists between the percentage of osteoblasts with receptor mRNA, mRNA signals/cell, and serum PTH levels (r = -0.82 and p < 0.05 and r = -0.78 and p < 0.01, respectively). The results provide the novel evidence of PTH-1R in human osteoclasts and suggest a functional role for the receptors in 2 degrees HPT.

Cloning and characterization of CIS 1b (cytokine inducible SH2-containing protein 1b), an alternative splicing form of CIS 1 gene

JAK-STAT pathway is essential in relaying cytokine signals and plays a vital role in cellular responses such as proliferation, differentiation and immunity. Some members of a recently found cytokine-inducible SH2 protein (CIS, =SOCS or SSI) family have proved to have negative effects on modulating JAK-STAT signaling pathway. In the present study, a novel human cDNA (CIS1b) which proved to be a variant of CIS1 gene was isolated by screen human placenta lambda gt11 cDNA library and 5'-rapid amplification of cDNA ends (RACE). Furthermore, the gene structure of CIS1 was determined by comparing the cDNA sequences of CIS1 and CIS1b to the genomic sequence in human chromosome 3p21.3. The expression patterns of CIS1b as well as CIS1 were analysed by Northern blot.

Anti-CD154 (CD40L) prevents recurrence of diabetes in islet isografts in the DR-BB rat

Islet transplantation for the treatment of autoimmune diabetes is more difficult because of the additional barrier presented by the autoimmunity. We tested the ability of hamster anti-rat CD154 to prevent recurrence of diabetes in renal subcapsular islet isografts in DR-BB (RT1uu) rats with established autoimmune diabetes. Experimental animals with established diabetes received intravenous injections of 15 mg/kg anti-CD154 on a specified schedule starting 2 days before renal subcapsular transplantation of an islet isograft. Control animals received either saline or hamster IgG. Plasma glucose levels >250 mg/dl over 3 days were used to indicate the recurrence of diabetes. Rats that received saline (n = 5) or control antibody (n = 3) had a recurrence of diabetes 6-11 days after transplantation. Histological examination of islet isografts from these rats showed complete destruction of the insulin-producing portion of the isograft with residual cells positive for glucagon. Recipient rats that received anti-CD154 at the 15-mg/kg dosage (n = 6) did not have a recurrence of diabetes for 308-461 days after transplantation. Islet isografts removed from the rats showed low levels of insulin immunoreactivity, high levels of insulin mRNA, and focal infiltration with lymphocytes but no evidence of islet destruction. Mean peak antibody concentration was 266 microg/ml and returned to undetectable levels by 67-88 days after transplantation. Rats that received anti-CD154 starting at 4-7 days after transplantation had a recurrence of diabetes within 11 days of the isotransplantation. Therefore, anti-CD154 as the sole immunomodulator prevented the recurrence of diabetes in islet isografts in rats with established autoimmune diabetes. This suggests that CD40/CD154 blockade is effective in preventing the insulitis or the effector phase of autoimmune diabetes.

Polymorphism of the ABO blood group genes in Han, Kazak and Uygur populations in the Silk Route of northwestern China

Genetic polymorphism in the ABO blood group gene of Han, Kazak and Uygur populations inhabiting the most northwestern part of China was investigated using polymerase chain reaction-based techniques. The present study enrolled 43 healthy unrelated Han, 37 Kazak and 59 Uygur volunteers. The allele in A1 blood group is distinguished A0101 and A0102 in difference of nucleotide position 467. The A0101 allele is more frequent in Caucasian and the A0102 allele is characteristic in Mongoloid. It must be notable that A0201 in the A2 group (with a single base deletion at nucleotides 1059 to 1061) which was characteristic of Caucasian was observed in Kazak and Uygur populations but not in Han. Further, 00201 (with no nucleotide deletion at 261 and three nucleotide differences), which is frequent in different races including Caucasian except for Mongoloid, was detected also in Kazak and Uygur populations. The frequencies of B0101 in Kazak, Uygur and Han were comparable to those of other Asian populations but higher than those of Caucasian populations. Collectively, these results reveal that the allele frequencies of Kazak and Uygur at the ABO blood group locus are an intermediate between those of Mongoloid and Caucasian, suggesting the admixed feature of Kazak and Uygur with Mongoloid and Caucasian.

Short-term administration of the bisphosphonate ibandronate increases bone volume and prevents hyperparathyroid bone changes in mild experimental renal failure

BACKGROUND

Bisphosphonates (BP) are potent antiresorptive agents that have been used successfully in several bone diseases associated with hyperresorption. Hyperresorption, hypercalcemia, and osteoporosis are frequent findings in patients with renal failure or after renal transplantation. The present study was carried out to determine the effects of a new BP, ibandronate, on bone in a state of normal vs. moderately impaired renal function.

MATERIAL AND METHODS

Forty 90-day-old female rats were either 2/3 nephrectomized (Nx, n = 20) or sham-operated (Sham, n = 20). Half of the Nx and Sham rats received either ibandronate (1.25 microg/rat s.c.) or vehicle once weekly for three weeks. Before euthanasia, blood drawings were performed and 24-hr urine was collected. Femurs were analyzed by bone histomorphometry.

RESULTS

Serum creatinine, parathyroid hormone, and osteocalcin levels were equally higher in Nx rats given ibandronate or vehicle than in Sham rats. There was no difference in serum calcium, phosphorus, alkaline phosphatase, and urinary creatinine among the groups. Ibandronate-treated rats had lower urinary calcium and deoxypyridinoline crosslink levels than their Sham counterparts. Ibandronate-treated rats had higher bone volume than vehicle-treated animals. Ibandronate prevented the increase in erosion depth and bone turnover in Nx rats.

CONCLUSIONS

BPs such as ibandronate represent potentially useful tools in the treatment of certain facets of renal bone disease. Indications for BP therapy may include treatment of osteoporosis, hypercalcemia, and/or extraosseous calcifications. Optimal dose and frequency of BP administration need to be determined in these patients.

Targeted overexpression of insulin-like growth factor I to osteoblasts of transgenic mice: increased trabecular bone volume without increased osteoblast proliferation

Insulin-like growth factor I (IGF-I) is an important growth factor for bone, yet the mechanisms that mediate its anabolic activity in the skeleton are poorly understood. To examine the effects of locally produced IGF-I in bone in vivo, we targeted expression IGF-I to osteoblasts of transgenic mice using a human osteocalcin promoter. The IGF-I transgene was expressed in bone osteoblasts in OC-IGF-I transgenic mice at high levels in the absence of any change in serum IGF-I levels, or of total body growth. Bone formation rate at the distal femur in 3-week-old OC-IGF-I transgenic mice was approximately twice that of controls. By 6 weeks, bone mineral density as measured by dual energy x-ray, and quantitative computed tomography was significantly greater in OC-IGF-I transgenic mice compared with controls. Histomorphometric measurements revealed a marked (30%) increase femoral cancellous bone volume in the OC-IGF-I transgenic mice, but no change in the total number of osteoblasts or osteoclasts. Transgenic mice also demonstrated an increase in the osteocyte lacunea occupancy, suggesting that IGF-I may extend the osteocyte life span. We conclude that IGF-I produced locally in bone osteoblasts exerts its anabolic effect primarily by increasing the activity of resident osteoblasts.

[Refined chromosome assignment of human novel H-RalGDS gene on chromosome 9q34.1 by using radiation hybrid genebridge 4 panel]

OBJECTIVE

Refined chromosome assignment of a novel Ras-related H-RalGDS gene (the human homology of rat RalGDS, Ral guanine nucleotide dissociation stimulator recently cloned and characterized by our laboratory) by using human/rodent radiation somatic cell hybrid panel GB4.

METHODS

According to the sequence of the 3'-untranslated region of H-RalGDS cDNA, forward and reverse primers were designed and used to amplify the human/rodent somatic radiation hybrid Genebridge 4 panel. The PCR result of each cell line of the panel was scored in a certain way and put into the related internet site of WI/MIT Radiation Hybrid Mapper for RH mapping and comprehensive analysis.

RESULTS

The H-RalGDS gene was successfully localized to the framework of chromosome 9. After referring to literature and further integrated mapping analysis of the physical, genetic linkage and cytological mappings, the gene was assigned precisely between the markers SURF5 and RPL7A which had already been assigned to human chromosome 9q34.1.

CONCLUSION

The localization of H-RalGDS not only contributed much to the construction of refined gene map and cytogenetic map within the region of chromosome 9q34, but also made clear that RH mapping of human novel genes is a simple, convenient and reliable method which can provide even more genetic information of genes within chromosomal regions.

Intermittent and continuous administration of the bisphosphonate ibandronate in ovariohysterectomized beagle dogs: effects on bone morphometry and mineral properties

Bisphosphonates have emerged as a valuable treatment for postmenopausal osteoporosis. Bisphosphonate treatment is usually accompanied by a 3-6% gain in bone mineral density (BMD) during the first year of treatment and by a decrease in bone turnover. Despite low bone turnover, BMD continues to increase slowly beyond the first year of treatment. There is evidence that bisphosphonates not only increase bone volume but also enhance secondary mineralization. The present study was conducted to address this issue and to compare the effects of continuous and intermittent bisphosphonate therapy on static and dynamic parameters of bone structure, formation, and resorption and on mineral properties of bone. Sixty dogs were ovariohysterectomized (OHX) and 10 animals were sham-operated (Sham). Four months after surgery, OHX dogs were divided in six groups (n = 10 each). They received for 1 year ibandronate daily (5 out of 7 days) at a dose of 0, 0.8, 1.2, 4.1, and 14 microg/kg/day or intermittently (65 microg/kg/day, 2 weeks on, 11 weeks off). Sham dogs received vehicle daily. At month 4, there was a significant decrease in bone volume in OHX animals (p < 0.05). Doses of ibandronate >/= 4.1 microg/kg/day stopped or completely reversed bone loss. Bone turnover (activation frequency) was significantly depressed in OHX dogs given ibandronate at the dose of 14 microg/kg/day. This was accompanied by significantly higher crystal size, a higher mineral-to-matrix ratio, and a more uniformly mineralized bone matrix than in control dogs. This finding lends support to the hypothesis that an increase in secondary mineralization plays a role in gain in BMD associated with bisphosphonate treatment. Moreover, intermittent and continuous therapies had a similar effect on bone volume. However, intermittent therapy was more sparing on bone turnover and bone mineral properties. Intermittent therapy could therefore represent an attractive alternative approach to continuous therapy.