Biomedical subjects

M Stangassinger

Publications and source records attributed to M Stangassinger.

At least 19 recordsLinked to original sources

PubMed2006

Effects of amount of intake and stage of forage maturity on urinary allantoin excretion and estimated microbial crude protein synthesis in the rumen of steers.

Using ruminally cannulated steers, we investigated how urinary allantoin excretion was related to variations in feed intake and stage of forage maturity. Further, different approaches were compared for predicting ruminal microbial crude protein (MCP) synthesis and its efficiency. Experimental diets were arranged in a replicated 3 x 3 Latin square design (experiment 1) and a 4 x 4 Latin square design (experiment 2). In experiment 1, a mixed diet [forage to concentrate, 68:32 on a dry matter (DM) basis] was fed at three intake levels corresponding to 1, 1.5 and 2 times maintenance energy requirements. In experiment 2, four silage-based diets were fed based on perennial ryegrass (Lolium perenneL.), which was harvested at four maturity stages. Both experiments demonstrated the influence of diet on microbial growth rate and by this on efficiency of MCP synthesis, although the magnitude of the effects differed between approaches used for estimating MCP. Linear functions satisfactorily characterised the relationship between urinary allantoin excretion (y) and digestible organic matter (OM) intake (x, kg/day; experiment 1: y = 7.94 + 17.34 x; R(2) = 0.785) or intake of OM effectively degraded in the rumen (x, kg/day; experiment 2; y = 22.32 + 5.93 x; R(2) = 0.695). Urinary excretion of allantoin permitted a semi-quantitative prediction of MCP synthesis: ranking of diets and magnitude of changes in MCP synthesis were reflected.

Allantoin↗

PubMed2004

Effect of exercise on the mobilization of retinol and retinyl esters in plasma of sled dogs.

Fasting dogs do transport vitamin A (VA) in plasma not only as retinol but predominantly as retinyl esters. Contrary to retinol, nothing is known concerning the effects of athletic performance on plasma retinyl ester concentrations. The aim of this study was therefore to examine whether physical stress because of exercise and modification of the oxidative stress by supplementation of alpha-tocopherol influences the concentrations of retinol and retinyl esters in plasma of sled dogs. The study was carried out on 41 trained adult sled dogs, which were randomly assigned into two groups. One group (19 dogs) was daily substituted with 50 mg dl-alpha-tocopheryl acetate per kilogram body weight and the control group (22 dogs) was maintained on a basal diet during 3 months prior to exercise. The plasma concentrations of retinol, retinyl esters, alpha-tocopherol and triglycerides were measured immediately before, directly after and 24 h after exercise. The supplementation of alpha-tocopheryl acetate had no effect on plasma retinol and retinyl ester concentrations at any measurement time point. However, retinyl ester levels doubled in the non-supplemented group immediately after the race (p < 0.001), whereas in the supplemented group similar high levels were observed not until 24 h post-racing (p < 0.001). The high levels of retinyl esters were paralleled to some extent by an increase in plasma triglyceride concentrations, which were significantly higher 24 h post-racing than immediately before (p < 0.001) and after exercise (p < 0.001) in both groups. The increase in retinyl ester concentrations might be indicative of their mobilization from liver and adipose tissue. Whether plasma retinyl esters can be used as an indicator for the extent of nutrient mobilization during and post-exercise in sled dogs remains to be elucidated.

Adipose Tissue↗

PubMed2001

Expression and characterization of the chemokine receptors CCR2 and CCR5 in mice.

The chemokine receptors CCR2 and CCR5 play important roles in the recruitment of monocytes/macrophages and T cells. To better understand the role of both receptors in murine models of inflammatory diseases and to recognize potential problems when correlating these data to humans, we have generated mAbs against murine CCR2 and CCR5. In mice CCR2 is homogeneously expressed on monocytes and on 2--15% of T cells, closely resembling the expression pattern in humans. In contrast to humans, murine NK cells are highly CCR5 positive. In addition, CCR5 is expressed on 3--10% of CD4 and 10--40% of CD8-positive T cells and is weakly detectable on monocytes. Using a model of immune complex nephritis, we examined the effects of inflammation on chemokine receptor expression and found a 10-fold enrichment of CCR5(+) and CCR2(+) T cells in the inflamed kidneys. The activity of various chemokines and the antagonistic properties of the mAbs were measured by ligand-induced internalization of CCR2 and CCR5 on primary leukocytes. The Ab MC-21 (anti-CCR2) reduced the activity of murine monocyte chemotactic protein 1 by 95%, whereas the Ab MC-68 (anti-CCR5) blocked over 99% of the macrophage-inflammatory protein 1alpha and RANTES activity. MC-21 and MC-68 efficiently blocked the ligand binding to CCR2 and CCR5 with an IC(50) of 0.09 and 0.6--1.0 microg/ml, respectively. In good correlation to these in vitro data, MC-21 almost completely prevented the influx of monocytes in thioglycollate-induced peritonitis. Therefore, both Abs appear as useful reagents to further study the role of CCR2 and CCR5 in murine disease models.

Animals↗

PubMed2001

Depletion of CCR5-expressing cells with bispecific antibodies and chemokine toxins: a new strategy in the treatment of chronic inflammatory diseases and HIV.

The chemokine receptor CCR5 is expressed on the majority of T cells and monocytes in the inflammatory infiltrate of diseases such as rheumatoid arthritis, renal diseases, and multiple sclerosis. In contrast, little expression of CCR5 is found on peripheral blood leukocytes. A specific depletion of CCR5(+) cells could therefore be a useful strategy to reduce the cellular infiltrate in chronic inflammations. Moreover, CCR5 is the major coreceptor for M-tropic HIV-1 strains. Depletion of CCR5(+) leukocytes may help to eliminate cells latently infected with HIV-1. We designed two constructs that specifically destroy chemokine receptor-positive cells. The first construct, a bispecific Ab, binds simultaneously to CCR5 and CD3. Thereby it redirects CD3(+) T cells against CCR5(+) target cells. The Ab specifically depletes CCR5(+) T cells and monocytes, but is inactive against cells that do not express CCR5. Furthermore, ex vivo the bispecific Ab eliminated >95% of CCR5(+) monocytes and T cells from the synovial fluid of patients with arthritis. Also, we designed a fusion protein of the chemokine RANTES and a truncated version of Pseudomonas. exotoxin A. The fusion protein binds to CCR5 and down-modulates the receptor from the cell surface. The chemokine toxin completely destroyed CCR5(+) Chinese hamster ovary cells at a concentration of 10 nM, whereas no cytotoxic effect was detectable against CCR5(-) Chinese hamster ovary cells. Both constructs efficiently deplete CCR5-positive cells, appear as useful agents in the treatment of chronic inflammatory diseases, and may help to eradicate HIV-1 by increasing the turnover of latently infected cells.

ADP Ribose Transferases↗

PubMed2001

Assessment of colostral transfer and systemic availability of immunoglobulin G in new-born foals using a newly developed enzyme-linked immunosorbent assay (ELISA) system.

To measure the immunoglobulin G (IgG) concentration in colostrum, milk and serum samples, a sandwich enzyme-linked immunosorbent assay (ELISA) detection system was developed. The system provided high reproducibility and sensitivity for routine diagnostic purposes. The period of fluctuating serum concentrations of IgG was monitored in new-born foals and their mares for a period of 6 weeks postnatum and postpartum, respectively. All foals received colostrum from their mares. The mean IgG concentration in the precolostral mare serum was approximately 19.0 mg/ml and decreased significantly to 13.8 mg/ml within the first 24 h postpartum. The IgG value fell to a minimum of 11.2 mg/ml by day 21 and increased to 21.6 mg/ml by day 42 postpartum. Within the first 4 h postpartum, mean IgG concentrations of 54.5 mg/ml were measured in the colostrum. A significant decrease to 10.1 mg IgG/ml colostrum was then noted 9-12 h postpartum. The mean IgG concentrations in foal serum increased from 0.3 mg/ml (precolostral value) to 9.6 mg/ml within 5-8 h postnatum. After 13-16 h postnatum, the highest IgG value of 15.7 mg/ml was reached. Over time the mean IgG concentration decreased significantly to 7.9 mg/ml at day 35. At the end of the observation period (day 42 postnatum) the mean IgG concentration once again increased to 11.2 mg/ml serum. In addition, the possible influence of various parameters on IgG concentration were examined. No significant influences could be shown by the breed, mare age, number of pregnancies, days of gestation, month foaled, foal sex, or the different farms. Finally, the cumulative incidence of failure of passive transfer (FPT) defined as IgG levels < 4 mg/ml foal serum, and partial FPT (PFPT) at levels ranging from 4 to 8 mg/ml foal serum was determined. From a total of 70 foals, 10.0% showed FPT and 18.6% showed PFPT.

Animals↗

PubMed2001

B lymphopoiesis is upregulated after orchiectomy and is correlated with estradiol but not testosterone serum levels in aged male rats.

Previous studies have shown that B lymphopoiesis is augmented after androgen withdrawal in male mice. As an analogy to the skeletal system, some effects of androgens on the proliferation of B cells may be mediated via aromatization into estrogens in vivo. The aim of the present study was to assess the effects of androgen withdrawal on B lymphopoiesis in bone marrow of aged male rats sequentially over a period of 9 months, and to correlate the flow-cytometric findings with changes in systemic levels of sex steroids. We first showed that androgen withdrawal is associated with enhanced B lymphopoiesis in bone marrow of 4-month-old male orchiectomized (ORX) rats, and that the changes in the bone marrow B cell compartment in ORX animals can be reversed by testosterone supplementation. In a subsequent, sequential experiment, we found that orchiectomy induced a sustained rise in Thy 1.1+/CD45R+ bone marrow cells committed for the B cell lineage that lasted for several months in 13-month-old aged rats. In a stepwise model of multiple regression analysis using estradiol, free and total testosterone as independent variables, estradiol was the strongest predictor of the percentage of B precursor cells in bone marrow in aged SHAM and ORX rats. Free and total testosterone did not correlate with B lymphopoiesis in aged SHAM rats. The current experiment has clearly shown that androgen withdrawal upregulates the number of B lineage cells over several months in rat bone marrow. Furthermore, our results provide evidence that estradiol may play an important role as a physiological suppressor of B lymphopoiesis in aged male rats.

Aging↗

PubMed2001

NK and T cells constitute two major, functionally distinct intestinal epithelial lymphocyte subsets in the chicken.

Non-mammalian NK cells have not been characterized in detail; however, their analysis is essential for the understanding of the NK cell receptor phylogeny. As a first step towards defining chicken NK cells, several tissues were screened for the presence of NK cells, phenotypically defined as CD8(+) cells lacking T- or B-lineage specific markers. By this criteria, approximately 30% of CD8(+) intestinal intraepithelial lymphocytes (IEL), but <1% of splenocytes or peripheral blood lymphocytes were defined as NK cells. These CD8(+)CD3(-) IEL were used for the generation of the 28-4 mAb, immunoprecipitating a 35-kDa glycoprotein with a 28-kDa protein core. The CD3 and 28-4 mAb were used to separate IEL into CD3(+) IEL T cells and 28-4(+) cells, both co-expressing the CD8 antigen. During ontogeny, 28-4(+) cells were abundant in the IEL and in the embryonic spleen, where two subsets could be distinguished according to their CD8 and c-kit expression. Most importantly, 28-4(+) IEL lysed NK-sensitive targets, whereas intestinal T cells did not have any spontaneous cytolytic activity. These results define two major, phenotypically and functionally distinct IEL subpopulations, and imply an important role of NK cells in the mucosal immune system.

Animals↗

PubMed2001

1alpha-hydroxyvitamin D2 is less toxic but not bone selective relative to 1alpha-hydroxyvitamin D3 in ovariectomized rats.

Identification of bone selective vitamin D analogues would provide an interesting substance class for the treatment of osteoporosis. The synthetic prodrug 1alpha-hydroxyvitamin D2 [1alpha(OH)D2] has been shown to combine equal bone-preserving activity with distinctly reduced calcemic effects relative to 1alpha-hydroxyvitamin D3 [1alpha(OH)D3] in 3-month-old ovariectomized (OVX) rats. Therefore, 1alpha(OH)D2 may be a bone-selective compound. The aim of this study was to compare the bone protective and the calcemic activities of chronically administered 1alpha(OH)D2 and 1alpha(OH)D3 in 6-month-old OVX rats over a broad dose range from ineffective to toxic doses. Ninety-six female 6-month-old Fischer-344 rats were used for this experiment. Eighty rats were bilaterally OVX, 8 rats were sham-operated (SHAM), and 8 rats were killed at the time of surgery as a baseline control. Groups of OVX rats received vehicle alone (n = 16) or daily doses in the diet of 0.025, 0.05, 0.1, and 0.2 microg of 1alpha(OH)D2 or 1alpha(OH)D3 per kg body weight (BW) per day (n = 8 each). After calcein double-labeling, all animals were killed 3 months post-OVX. Orally administered 1alpha(OH)D2 was significantly less toxic compared with 1alpha(OH)D3 in terms of BW gain and kidney calcium content. The effects of 1alpha(OH)D2 and 1alpha(OH)D3 on serum calcium and urinary calcium excretion were generally similar at all doses in this study. Both 1alpha(OH)D2 and 1alpha(OH)D3 prevented the estrogen deficiency-induced bone loss in OVX rats, and induced profound bone anabolic effects at high dosages. 1alpha(OH)D3 and 1alpha(OH)D2 also dose-dependently increased total bone mineral density (BMD), cortical area, and cortical thickness in the tibial diaphysis of OVX rats. Bone resorption as assessed by osteoclast numbers (Oc.Ns) in vertebral cancellous bone and urinary excretion of deoxypyridinoline (DPD) was dose-dependently suppressed by 1alpha(OH)D2 and 1alpha(OH)D3. These data show that although 1alpha(OH)D2 was slightly but significantly less toxic compared with 1alpha(OH)D3, it did not have increased skeletal effects at any dose. Taken together, our findings argue against selective metabolic activation of 1alpha(OH)D2 in bone.

Animals↗

PubMed2000

Oncotic pressure in solid tumors is elevated.

Oncotic and hydrostatic pressure differences control the movement of fluid and large molecules across the microvascular wall of normal and tumor tissues. Recent studies have shown that the interstitial fluid pressure in tumors is elevated and is approximately equal to the microvascular pressure. Whereas oncotic pressure in blood plasma of various species is known, no data are available on the oncotic pressure in the interstitial space of tumors. We hypothesize that because of the leaky nature of tumor vessels, oncotic pressure in tumor interstitium should be close to that in plasma. To this end, we first developed a chronic wick method for the direct measurement of oncotic pressures in the interstitial fluid of tumors grown in mice. We found interstitial oncotic pressures in four human tumor xenografts to be higher than in s.c. tissue and comparable to that in plasma [rhabdomyosarcoma (RD), 24.2+/-4.7; squamous cell carcinoma (FaDu), 19.9+/-1.9; small cell lung carcinoma (54A), 21.1+/-2.8; colon adenocarcinoma (LIS174T), 16.7+/-3.0 mm Hg; s.c. tissue, 8.2+/-2.3; plasma, 20.0+/-1.6 mm Hg]. These results support our hypothesis that the oncotic pressure difference across the tumor microvascular wall is low. The high oncotic pressure in tumors is consistent with the elevated interstitial fluid pressure, and it contributes to the suboptimal delivery of large therapeutic agents to neoplastic cells.

Animals↗

PubMed2000

Transfer of the chemokine receptor CCR5 between cells by membrane-derived microparticles: a mechanism for cellular human immunodeficiency virus 1 infection.

The release of microparticles from eukaryotic cells is a well-recognized phenomenon. We demonstrate here that the chemokine receptor CCR5, the principal co-receptor for macrophage-tropic human immunodeficiency virus (HIV)-1, can be released through microparticles from the surface of CCR5+ Chinese hamster ovary cells and peripheral blood mononuclear cells. Microparticles containing CCR5 can transfer the receptor to CCR5- cells and render them CCR5+. The CCR5 transfer to CCR5-deficient peripheral blood mononuclear cells homozygous for a 32-base-pair deletion in the CCR5 gene enabled infection of these cells with macrophage-tropic HIV-1. In monocytes, the transfer of CCR5 could be inhibited by cytochalasin D, and transferred CCR5 could be downmodulated by chemokines. A transfer of CCR5 from peripheral blood mononuclear cells to endothelial cells during transendothelial migration could be demonstrated. Thus, the transfer of CCR5 may lead to infection of tissues without endogenous CCR5 expression. Moreover, the intercellular transfer of membrane proteins by microparticles might have broader consequences for intercellular communication beyond the effects seen for HIV-1.

Animals↗

PubMed2000

Adjuvant effects of various lipopeptides and interferon-gamma on the humoral immune response of chickens.

The adjuvant effects of various lipopeptides and recombinant chicken interferon gamma (IFN-gamma) on the humoral immune response of laying hens was investigated in four immunization studies. We used the lipopeptide Pam3Cys-Ser-(Lys)4 (PCSL), the conjugate P-Th1 consisting of the lipopeptide P3CS and the T-helper epitope Th1 (FISEAIIHVLHSRHPG), and the conjugate P-Th2 of the lipopeptide P3CSS and the T-helper epitope Th2, which corresponds to the peptide EWEFVNTPPLV, as adjuvants. Human serum albumin (HSA), recombinant bovine somatotropin (RBST), and human immunoglobulin G (IgG) served as antigens in the different experiments. All tested adjuvants enhanced the humoral immune response with various intensities. Chickens showed high antibody titers after the immunization with HSA even without adjuvant, but the adjuvant effects of PCSL and the combination of PCSL and recombinant chicken interferon-gamma (IFN-gamma) were much more pronounced using the antigens RBST and IgG. Especially after the third immunization, higher titers of antibodies were induced by the coadministration of P-Th1 and, to a greater extent, by the combination of PCSL and P-Th1 compared with the use of PCSL. Also, chickens that had received PCSL and P-Th2 showed the highest immune response, even after the second booster. The average concentrations of chicken immunoglobulin Y were significantly higher in 5-mo-old chickens (9.4 mg/mL serum and 10.1 mg/mL egg yolk) compared with 9-mo-old chickens (5.9 mg/mL serum and 5.1 mg/mL egg yolk). The specific serum antibody response was higher in the older chickens than in the younger chickens. Because chicken antibodies are likely to be used increasingly for diagnostic and therapy in the future, lipopeptides and recombinant chicken IFN-gamma may find many applications as adjuvants, thus contributing to the welfare of experimental animals.

Adjuvants, Immunologic↗

PubMed1999

Predominance of mononuclear cells expressing the chemokine receptor CCR5 in synovial effusions of patients with different forms of arthritis.

OBJECTIVE: To study the role of the chemokine receptors CCR5 and CCR2 in patients with arthritis. METHODS: CCR5 expression on peripheral blood leukocytes was compared with the expression on leukocytes isolated from the synovial fluid of 20 patients with different rheumatic joint diseases. Three additional samples were studied for CCR2 expression. The expression of chemokine receptors on blood and synovial fluid leukocytes was determined by 3-color flow cytometry analysis. To test CCR5 receptor down-modulation from the cell surface, leukocytes were incubated in vitro with a RANTES (regulated on activation, normal T cell expressed and secreted) derivative, aminooxypentane (AOP)-RANTES. Patients were genotyped for the delta32 CCR5 deletion by polymerase chain reaction. RESULTS: A high percentage of CCR5-expressing CD4+ and CD8+ T cells (74% and 81%, respectively), monocytes (51%), and natural killer cells (35%) was found in the synovial fluid of all patients, whereas in the peripheral blood, only a small percentage of these cells expressed CCR5 (13%, 32%, 7.8%, and 4%, respectively). Infiltration of CCR5-positive leukocytes was not reduced in CCR5-heterozygous patients. A similar, but less pronounced, distribution was observed for CCR2-positive T cells. In vitro, CCR5 was completely down-modulated on synovial fluid leukocytes by AOP-RANTES. CONCLUSION: The predominance of CCR5-positive mononuclear cells in the synovial effusions of patients with arthritis suggests an important role for CCR5 in the process of joint inflammation, and identifies CCR5 as a possible new target for therapeutic intervention.

Adolescent↗

PubMed1999

Skeletal effects of zinc deficiency in growing rats.

There is ample evidence that zinc plays an important role in bone metabolism and zinc deficiency has been implicated as a risk factor in the development of osteoporosis. It was the aim of the present study to investigate the skeletal effects of alimentary zinc deficiency in growing rats using quantitative bone histomorphometry. Twenty-four male Sprague Dawley rats with a mean initial body weight of 101 +/- 2 g were allocated in two groups of 12 rats each and had free access to a semi-synthetic, casein-based, zinc-deficient diet (0.76 mg zinc/kg) or to the same diet supplemented with 60 mg zinc per kg. All rats were sacrificed 42 days after the start of the experiment and the right distal femur was removed for bone histomorphometry. Relative to controls (+Zn), the zinc-deficient rats (-Zn) had a significantly lower body weight and about an 80% reduction in plasma and femur zinc concentration. The histomorphometric evaluation of the distal femoral metaphysis showed that zinc deficiency led to a 45% reduction (p < 0.01) in cancellous bone mass and to a deterioration of trabecular bone architecture, with fewer and thinner trabeculae. The osteopenia in -Zn rats was accompanied by significant reductions in osteoid perimeter (-31%, p < 0.05), osteoblast perimeter (-30%, p < 0.05), and osteoclast number (-38%, p < 0.01) relative to +Zn controls. We conclude that zinc deficiency induced low turnover osteopenia in femoral cancellous bone of growing rats. These results support the hypothesis that zinc deficiency during growth may impair the accumulation of maximal bone mass in humans; additionally, they suggest that zinc deficiency may play a role as a risk factor in the pathogenesis of osteoporosis.

Animals↗

PubMed1998

Aminooxypentane-RANTES induces CCR5 internalization but inhibits recycling: a novel inhibitory mechanism of HIV infectivity.

CCR5, a chemokine receptor expressed on T cells and macrophages, is the principal coreceptor for M-tropic HIV-1 strains. Recently, we described an NH2-terminal modification of the CCR5 ligand regulated on activation, normal T cell expressed and secreted (RANTES), aminooxypentane-RANTES (AOP-RANTES), that showed potent inhibition of macrophage infection by HIV-1 under conditions where RANTES was barely effective. To investigate the mechanism of AOP-RANTES inhibition of HIV infectivity we examined the surface expression of CCR5 using a monoclonal anti-CCR5 antibody, MC-1. We demonstrate that AOP-RANTES rapidly caused >90% decrease in cell surface expression of CCR5 on lymphocytes, monocytes/ macrophages, and CCR5 transfected Chinese hamster ovary (CHO) cells. RANTES also caused a loss of cell surface CCR5, although its effect was less than with AOP-RANTES. Significantly, AOP-RANTES inhibited recycling of internalized CCR5 to the cell surface, whereas RANTES did not. When peripheral blood mononuclear cells are cultured for prolonged periods of time in the presence of RANTES, CCR5 expression is comparable to that seen on cells treated with control medium, whereas there is no CCR5 surface expression on cells cultured in the presence of AOP-RANTES. Immunofluorescence indicated that both AOP-RANTES and RANTES induced downmodulation of cell surface CCR5, and that the receptor was redistributed into endocytic organelles containing the transferrin receptor. When RANTES was removed, the internalized receptor was recycled to the cell surface; however, the receptor internalized in the presence of AOP-RANTES was retained in endosomes. Using human osteosarcoma (GHOST) 34/CCR5 cells, the potency of AOP-RANTES and RANTES to inhibit infection by the M-tropic HIV-1 strain, SF 162, correlated with the degree of downregulation of CCR5 induced by the two chemokines. These differences between AOP-RANTES and RANTES in their effect on receptor downregulation and recycling suggest a mechanism for the potent inhibition of HIV infection by AOP-RANTES. Moreover, these results support the notion that receptor internalization and inhibition of receptor recycling present new targets for therapeutic agents to prevent HIV infection.

Animals↗

PubMed1998

Inhibition of the development of spontaneous autoimmune thyroiditis in the obese strain (OS) chickens by in vivo treatment with anti-CD4 or anti-CD8 antibodies.

The involvement of CD4+ and CD8+ T cells in pathogenesis of spontaneous autoimmune thyroiditis (SAT) in obese strain (OS) chickens has not been studied in depth until now. We depleted CD4+ or CD8+ T cells in OS chickens by treatment with murine monoclonal anti-CD4 or anti-CD8 antibodies at 3 day intervals beginning at hatching. The birds were killed at 19-25 days of age. Treatment with anti-CD4 antibody completely prevented SAT development, while treatment with anti-CD8 antibody partially inhibited SAT. These results show the critical role of CD4+ T cells in the development of SAT in OS chickens, and indicate that CD8+ T cells are also involved in SAT pathogenesis.

Age Factors↗

PubMed1998

Short-term prophylaxis against estrogen depletion-induced bone loss with calcitriol does not provide long-term beneficial effects on cancellous bone mass or structure in ovariectomized rats.

It was the aim of the present study to investigate whether a 2-month prophylaxis of postovariectomy bone loss with low-dose calcitriol would have long-lasting beneficial effects on cancellous bone mass or structure after its withdrawal in rats. Six-month-old female Fischer 344 rats were either ovariectomized (OVX) or sham-operated (SHAM). Groups of SHAM and OVX rats were orally treated with either 0.05 microgram calcitriol/kg per day or vehicle for 2 months postovariectomy, starting immediately after ovariectomy. Thereafter, the rats were maintained without treatment for another 4 months. Half the animals in each group were killed 2 months postovariectomy; the rest of the rats were killed 6 months postovariectomy. Cancellous bone histomorphometry was performed on the first lumbar vertebral body and on the proximal tibial metaphysis. Administration of low-dose calcitriol to SHAM and OVX rats resulted in hypercalciuria, but not hypercalcemia. By 2 months postovariectomy, calcitriol treatment of OVX rats had completely prevented tibial trabecular bone loss, and had increased vertebral cancellous bone mass in SHAM and OVX rats by about 30% over the level observed in SHAM vehicle controls. However, at the end of the experiment, i.e. 4 months after withdrawal of calcitriol, cancellous bone mass and structure in both the vertebrae and the tibiae of calcitriol-treated OVX rats were almost identical to those of vehicle-treated OVX rats. We conclude that prevention of bone loss with low-dose calcitriol during the phase of acute estrogen deficiency, when bone turnover is maximally increased, does not provide long-term beneficial effects on cancellous bone mass or structure in OVX rats. If extrapolated to postmenopausal women, this study would suggest that prophylaxis against postmenopausal bone loss with short-acting antiresorptive substances during only the first few years after menopause will probably not reduce the risk of postmenopausal osteoporosis later in life.

Analysis of Variance↗

PubMed1998

Ovariectomy augments B lymphopoiesis and generation of monocyte-macrophage precursors in rat bone marrow.

To investigate the effects of estrogen depletion on hematopoiesis and bone turnover, female rats were either ovariectomized (OVX) or sham operated and killed at 1, 2, 3, and 4 wk postsurgery. Flow cytometric analysis of bone marrow cells (BMC) revealed that, in close temporal association with the rise in bone turnover as measured by bone histomorphometry, the number of Thy 1.1+ and KiB1R+ BMC increased two- to threefold in OVX rats relative to sham controls. The Thy 1.1+ BMC were further characterized as Thy 1.1+/KiB1R+ and Thy 1.1+/HIS24+ double-positive cells of the B cell lineage. A transient rise in ED1+ myeloid cells expressing a lysosomal antigen specific for the monocyte-macrophage and osteoclast lineage coincided with the upregulation of osteoclast numbers in OVX rats at 2 wk postsurgery, but the number of ED8+ myelomonocytic BMC remained unchanged. Administration of estradiol prevented the rise in Thy 1.1+, KiB1R+, and ED1+ BMC in OVX animals. Our study indicates that ovariectomy upregulates B lymphopoiesis in rat bone marrow and increases myeloid cell differentiation into the monocyte-macrophage and possibly also the osteoclast lineage.

Animals↗

PubMed1998

Therapeutic efficacy of 1alpha,25-dihydroxyvitamin D3 and calcium in osteopenic ovariectomized rats: evidence for a direct anabolic effect of 1alpha,25-dihydroxyvitamin D3 on bone.

It is an important question for clinical therapy of osteoporosis with vitamin D metabolites whether these compounds exert their beneficial effects on the skeleton indirectly through an increase in intestinal calcium absorption or whether there is also a major direct component of action on bone. In this study, female 6-month-old Fischer rats were either ovariectomized (OVX) or sham operated. One month before surgery, all rats were placed on a diet containing 0.25% calcium and were kept on this diet throughout the study. Beginning 3 months post-OVX, groups of OVX rats orally received vehicle, a calcium supplement, low dose (0.025 microg/kg x day) or high dose (0.1 microg/kg x day) 1alpha,25-dihydroxyvitamin D3 [1,25-(OH)2D3], or combinations of low and high dose 1,25-(OH)2D3 with the calcium supplement. By 3 months postsurgery, pretreatment OVX controls had lost 74% and 37% of tibial and vertebral cancellous bone, respectively. Two-way factorial ANOVA showed that a 3-month treatment of osteopenic OVX rats with 1,25-(OH)2D3 dose dependently increased vertebral and tibial cancellous bone mass (P < 0.001 and P = 0.021, respectively) and trabecular width (P < 0.001). Furthermore, 1,25-(OH)2D3 increased serum calcium (P = 0.028) and urinary calcium excretion (P < 0.001) and reduced serum PTH levels (P < 0.001), osteoclast numbers (P < 0.001), and urinary collagen cross-links excretion (P < 0.001). Calcium supplementation alone was without therapeutic effect, and there was no significant two-way interaction between the individual treatment effects of 1,25-(OH)2D3 and calcium on bone mass. These data indicate that the anabolic effects of 1,25-(OH)2D3 in osteopenic OVX rats are mediated through a direct activity on bone.

Animals↗