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Biomedical subjects

U Trechsel

Publications and source records attributed to U Trechsel.

At least 19 recordsLinked to original sources
PubMed1996

The effect of intranasal salmon calcitonin on postmenopausal bone turnover as assessed by biochemical markers: evidence of maximal effect after 8 weeks of continuous treatment.

Although treatment with intranasal salmon calcitonin (sCT) has been shown to effectively inhibit postmenopausal bone loss, there is still controversy over both timing and the duration of its application. In an open prospective study, we therefore assessed the effect of shortterm intranasal sCT on postmenopausal bone turnover, employing biochemical markers of bone metabolism. Ten early postmenopausal, previously untreated women (1-5 years after menopause) with biochemical evidence of increased bone resorption and a low bone mineral density at baseline were treated with intranasal sCT (100 IU B.I.D.) for a period of 3 months. Oral calcium (500 mg/day) was administered simultaneously, and during a further 3 month follow-up interval. Treatment with sCT resulted in a pronounced suppression of bone resorption markers with a maximum effect reached after 8 weeks of therapy: as compared to the respective baseline values, mean levels decreased by -26.2% +/- 3.4% (P < 0.001) for pyridinoline, -32.7% +/- 3.5% (P < 0.001) for deoxypyridinoline, -32.7% +/- 3.3% (P < 0.001) for hydroxyproline, and -24.1% +/- 8.2% (P < 0.001) for the amino-terminal telopeptide. In contrast, changes in bone formation markers of osteocalcin (-14.4% +/- 4.8%, P < 0.05) and C-terminal procollagen type I propetide (-7.9% +/- 3.9%, ns) were much less pronounced. Unexpectedly, after week 8 of the study all resorption markers showed a plateau and a trend to increase, although intranasal sCT was continued for a total of 12 weeks. This effect could not be attributed to the formation of anti-sCT antibodies. After cessation of treatment, both bone formation and resorption markers rapidly returned to baseline levels. Bone mineral density of both spine and hip showed no significant change during the observation period. Our results demonstrate that in postmenopausal women with a high bone turnover, intranasal treatment with 200 IU of sCT effectively reduces bone turnover and maintains bone mass, the maximum effect being reached after 8 weeks of treatment.

Administration, Intranasal↗
PubMed1992

N-terminal truncation of salmon calcitonin leads to calcitonin antagonists. Structure activity relationship of N-terminally truncated salmon calcitonin fragments in vitro and in vivo.

Structural requirements for binding to the bone calcitonin (CT) receptor and for CT bioactivity both in vitro and in vivo were assessed for a series of N-terminally truncated, N alpha-acetylated, fragments of salmon calcitonin (sCT). Sequential deletion of amino acid residues from the amino-terminus of [Ala7]sCT-(2-32) peptide amide first led to partial agonists and, upon deletion of residues 1 to 7, to a high affinity antagonist, N alpha-acetyl-sCT-(8-32)-NH2. The presence of two separate domains within the sCT sequence is proposed: (I) a binding domain comprising residues 9-32 and (II) an activation domain requiring residues 3 to 6. N alpha-acetyl-sCT-(8-32)-NH2, in several bioassays including plasminogen activator release from LLC-PK1 cells (pA2 = 7.31), cAMP production in UMR-106-06 cells (pA2 = 7.81) and in the fetal rat long bone resorption assay showed potent antagonistic properties.

Acetylation↗
PubMed1992

The effect of rat parathyroid hormone (1-34) infusion on urinary 3-hydroxypyridinium cross-link excretion in the rat.

The utility of measurement of the urinary excretion of the 3-hydroxypyridinium cross-links, pyridinoline (Pyr) and deoxypyridinoline (Dpyr) as indices of bone resorption in rats was investigated. Total Pyr and Dpyr excretion were measured in young rats treated by s.c. infusion with rat parathyroid hormone (1-34) (PTH) at 22-30 micrograms/kg/day or with diluent (controls) for 14 days. During infusion, average urinary excretion of both cross-links was significantly higher in PTH rats (Pyr: 11.77 +/- 0.44 nmol/day), Dpyr: 15.81 +/- 0.95 nmol/day) than in controls (Pyr: 10.17 +/- 0.35 nmol/day, Dpyr: 12.03 +/- 0.67 nmol/day). These results were consistent with the magnitude of the expected increase in bone resorption rate with this dose of PTH. The method appears to provide a sensitive measure of bone resorption for in vivo bone studies in rats.

Amino Acids↗
PubMed1990

Stimulation of bone formation in vivo by transforming growth factor-beta: remodeling of woven bone and lack of inhibition by indomethacin.

Local effects of transforming growth factor-beta (TGF beta) on bone have been investigated in growing mice. The influence of indomethacin on TGF beta effects was also examined. Five daily injections of TGF beta-1 or -2 were administered subcutaneously over the frontal and parietal bones of seven-week-old mice. In animals treated with TGF beta alone or TGF beta and indomethacin, then killed on day 19 (day 1 = day of first TGF beta injection), the combined frontal and parietal bones were heavier and the frontal bones were thicker than in controls. On day 4, multiple layers of differentiating osteoblasts were visible in the periosteum of calvariae from TGF beta-treated animals. On day 8, highly vascularised periosteal woven bone was seen in the calvariae of TGF beta-treated animals. On day 19 (14 days after the last injection) the woven bone had been partially remodeled into lamellar bone containing bone marrow, and was still actively being remodeled. The histological appearance of bones from animals treated concurrently with TGF beta and indomethacin was identical to that of animals treated with TGF beta alone, and there appeared to be no difference between TGF beta-1 and TGF beta-2. Thus TGF beta-stimulated bone formation in vivo is a long term effect that appears to be independent of prostaglandins. Osteoclast counts in sections of TGF beta-treated animals were not elevated on day 4, although at this stage effects on osteoblastic cells were already morphologically apparent. Osteoclast counts in TGF beta-treated bones were significantly increased over control values on days 8 and 19.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Somatostatin receptors are restricted to a subpopulation of osteoblast-like cells during endochondral bone formation.

Specific binding sites for the peptide hormone somatostatin have previously been demonstrated in long bones from neonatal rats. In the present study, the distribution of somatostatin receptors during embryonic bone formation has been investigated using the stable radioiodinated somatostatin analogue, SDZ 204-090. Somatostatin receptors in rat long bones were first detectable at the time of invasion of the cartilage model by osteogenic cells. Initially, receptors were detectable throughout the region occupied by osteogenic cells. As bone growth proceeded, however, receptors were restricted to the region of most recent invasion of the hypertrophic cartilage, where osteoid had not yet been deposited. In vivo labelling studies in neonatal rats were carried out to identify the cells bearing somatostatin receptors. Receptors were present in a restricted region of the metaphysis, immediately adjacent to the hypertrophic cartilage. Chondrocytes, osteoclasts, and mature osteoblasts were not labelled by the radioligand. The labelled cells were often apposed to remnants of cartilage matrix and stained positively for the osteoblast marker, alkaline phosphatase. Thus the cells with specific somatostatin-binding sites were probably osteoblast precursor cells. Specific binding was detectable in all endochondral bones examined, including those of the skull, but no specific binding was found in the membrane bones of the skull. These data suggest that somatostatin is involved in the regulation of osteoblast differentiation during endochondral bone formation.

Animals↗
PubMed1990

Phosphate transport adaptation in rat jejunum and plasma level of 1,25-dihydroxyvitamin D3.

Intestinal absorption of inorganic phosphate (Pi) increases in response to a reduction in the dietary supply of Pi. In this work this adaptive response has been characterized in jejunal brush border membrane vesicles and studied in temporal relationship with the change in the plasma level of 1,25(OH)2D3. The results indicate that in rat jejunal brush border membrane vesicles the activity of the sodium-dependent Pi transport system is stimulated by a low Pi diet. This adaptive response was the result of an increase in the Vmax and a reduction in the Km of the cotransport system. This change in Pi transport was correlated with an increase in the circulating level of 1,25(OH)2D3 in a time-related fashion. In conclusion, these results are consistent with the notion that Pi restriction leads to an increase in Pi transport activity in the luminal membrane of the intestine. A time course study suggests that the elevation in plasma 1,25(OH)2D3 might be involved in the adaptation of the intestinal Pi transport system to Pi restriction.

Adaptation, Physiological↗
PubMed1989

Interleukin-6 is produced by bone and modulated by parathyroid hormone.

Interleukin-6 (IL-6) is a cellular regulatory molecule, the diverse functions of which relate to cells both within and outside the immune system. In this report we demonstrated that bone tissue, specifically osteoblasts, produce interleukin-6 and that this function can be modulated by the osteotrophic hormone parathyroid hormone (PTH). Given that the complex process of bone remodeling is now thought to be regulated not only by systemic hormones but also by locally produced factors, the existence of a parathyroid hormone-stimulated production of interleukin-6 by osteoblasts may have important physiological significance.

Animals↗
PubMed1988

Production of hemopoietic growth factors by bone tissue and bone cells in culture.

This study was carried out to determine whether bone might be a source of hemopoietic growth factors. Both neonatal murine calvaria and primary cultures of cells isolated from calvaria released, upon stimulation with lipopolysaccharide, an activity that stimulated the growth of the interleukin (IL) 3-dependent cell lines, 32D cl, 123, and NSF 60. Upon gel filtration, this activity eluted with a molecular weight of 30,000 kDa. Further characterization, however, revealed that the major activity in conditioned medium was not IL 3. Activity was absorbed by DEAE-Sephacel at low salt concentration, whereas IL 3 does not adhere. Furthermore, an IL 3-specific antiserum did not neutralize the activity from cells and only partly neutralized the activity generated by whole calvaria. After gel filtration, the 30-kDa activity stimulated the growth of very large colonies in semisolid medium consisting mainly of granulocytes with the remainder being macrophages. No colony types belonging to other hemopoietic lineages were found, indicating, again, that the activity was not identical to IL 3. Subsequently, conditioned medium was fractionated by hydrophobic chromatography on Phenyl-Sepharose CL-4B, yielding two peaks of activity. Neutralization of activity with antisera to granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL 3 and use of colony assays showed that medium conditioned by whole calvaria contained GM-CSF and granulocyte CSF (G-CSF) in similar amounts together with a little IL 3, and medium conditioned with calvaria cells contained GM-CSF and little G-CSF. We conclude that bone releases hemopoietic growth factors that could contribute both to hemopoiesis and to the recruitment of osteoclasts from progenitors resident in the adjacent marrow.

Animals↗
PubMed1988

Bisphosphonates inhibit 1,25-dihydroxyvitamin D3-induced increase of osteocalcin in plasma of rats in vivo and in culture medium of rat calvaria in vitro.

In order to test whether bisphosphonates, which are potent inhibitors of osteoclastic bone resorption, may also act upon osteoblasts, we studied the effect of dichloromethylenebisphosphonate (Cl2MBP) and 4-amino-1-hydroxybutylidene-1,1-bisphosphonate (AHBuBP) on in vivo levels and in vitro release of osteocalcin, a bone-specific protein produced by osteoblasts. In rats, 161 mumol/kg of Cl2MBP or 1.61 mumol/kg AHBuBP strongly inhibited the increase of plasma osteocalcin induced by 1,25(OH)2D3. The inhibition was measurable within 24 hours after the administration of bisphosphonate and was independent of any change in bone resorption. The effect upon osteocalcin release was also present in calvaria cultures. 250 microM Cl2MBP strongly inhibited the osteocalcin release induced by 10(-8) M 1,25(OH)2D3. In the presence of 1,25(OH)2D3, protein synthesis and DNA synthesis were also decreased, whereas in the absence of 1,25(OH)2D3, protein synthesis was increased. Thus, bisphosphonates affect the production of a bone-specific protein by osteoblasts in addition to their inhibitory action on osteoclasts.

Alendronate↗
PubMed1988

Short- and long-term effects of a single dose of bisphosphonates on retinoid-induced bone resorption in thyroparathyroidectomized rats.

The inhibitory effect of a single subcutaneous (s.c.) dose of three different bisphosphonates (Bps)--4-amino-1-hydroxybutylidene-1,1-bisphosphonate (AHBuBP), 2-(2-pyridinyl)-ethylidene-1,1-bisphosphonate (2-PEBP), and dichloromethylene-bisphosphonate (Cl2MBP)--was studied in a model of retinoid-induced bone resorption, which consists of assessing the hypercalcemic effect of the arotinoid Ro 13-6298 given s.c. for three days in thyroparathyroidectomized (TPTX) rats. The retinoid was given on day 0, 1, and 2. Bps were administered together with or at different times prior to the first dose of retinoid. A dose-dependent inhibition was obtained with all three compounds. AHBuBP produced complete inhibition which remained for 3 weeks at 0.1 mg P/kg. The dose-response curves were identical when the compound was given on the first day of retinoid administration (day 0) or 6 days earlier. With 2-PEBP, the dose-response curve was the same as that for AHBuBP when given on day 0. When given 6 days earlier, the curve was shifted to 30 times less potency. Cl2MBP was about 100 times less potent than AHBuBP when given on day 0, with 3 mg P/kg producing complete inhibition. When given 6 days earlier, the curve was also shifted to 10 times less potency, and even 30 mg P/kg failed to produce complete inhibition. With 10 mg P/kg, the inhibitory effect was maintained partially for up to 3 weeks. This study shows that in this model of bone resorption the inhibitory effect of a single dose of certain Bps is effective for at least 3 weeks and that the compounds vary in their activity over time.

Animals↗
PubMed1988

Parathyroid hormone-independent regulation of 1,25(OH)2D in response to inhibition of bone resorption.

Both plasma level of 1,25-dihydroxyvitamin D [1,25(OH)2D] and intestinal Ca absorption increase after biphosphonate-induced inhibition of bone resorption. Parathyroid hormone (PTH) has been considered a key mediating element of this homeostatic response. In the present work, the role of PTH was assessed by studying the influence of 1-hydroxypentane-1,1-bisphosphonate (HPeBP) on vitamin D and Ca metabolism in both intact and thyroparathyroidectomized (TPTX) rats. In intact rats, HPeBP given at 0.1 mg P/kg body wt sc for 10 days strongly inhibited bone resorption without affecting bone formation. This effect was associated with a marked stimulation of intestinal Ca absorption and Ca balance. In this condition, HPeBP caused a marked rise in plasma 1.25(OH)2D without affecting the level of 25-hydroxyvitamin D. In TPTX rats, HPeBP given at same dose also inhibited bone resorption and enhanced plasma 1,25(OH)2D, intestinal Ca absorption and Ca balance. In summary, this study shows that bisphosphonates such as HPeBP with prevailing inhibitory activity on bone resorption induce a marked stimulation of both 1,25(OH)2D production and intestinal Ca absorption. This homeostatic response is not attenuated after PTH removal. Thus, as previously shown for the response to low Ca diet, PTH does not appear to be an essential mediating factor for stimulating 1,25(OH)2D production in response to an increase in bone mineral retention.

Animals↗
PubMed1987

Effect of a single injection of two new bisphosphonates on the hypercalcemia and hypercalciuria induced by Walker carcinosarcoma 256/B in thyroparathyroidectomized rats.

The effect of one single injection of two new bisphosphonates, 4-amino-1-hydroxybutylidene-1,1-bisphosphonate and 2-(2-pyridyl)ethylidene-1,1-bisphosphonate, and of dichloromethylenebisphosphonate on the hypercalcemia and hypercalciuria induced by the Walker carcinosarcoma 256/B in the thyroparathyroidectomized rat was evaluated. When given either before or after the development of hypercalcemia and hypercalciuria, 16.1 mumol/kg 4-amino-1-hydroxybutylidene-1,1-bisphosphonate or 2-(2-pyridyl)ethylidene-1,1-bisphosphonate totally inhibited hypercalciuria, whereas hypercalcemia was only partially reduced over the 14 days of the experiment. At 10 and 100 times lower doses, the effect was strongest the first days, but still partially present 14 days later. The difference of activity on calcemia and calciuria appears to be due to the fact that the tumor increased both bone resorption and renal reabsorption of calcium. Only the former was altered by the bisphosphonates. The two new compounds appeared to be of similar potency and more active than dichloromethylenebisphosphonate. These compounds could be promising for the treatment of malignant hypercalcemia and other conditions with increased bone resorption in humans, even when given only over short periods of time.

Alendronate↗
PubMed1987

Effect of synthetic calcium pyrophosphate and hydroxyapatite crystals on the interaction of human blood mononuclear cells with chondrocytes, synovial cells, and fibroblasts.

Synthetic calcium pyrophosphate dihydrate crystals and, to a lesser extent, synthetic hydroxyapatite crystals increased the amount of interleukin-1/mononuclear cell factor released by human blood monocytes, as measured by collagenase and prostaglandin E2 production by rabbit chondrocytes, human dermal fibroblasts, and adherent rheumatoid synovial cells. The same crystals also directly induced collagenase and prostaglandin E2 secretion by rabbit chondrocytes, and potentiated the action of interleukin-1/mononuclear cell factor on chondrocytes. These mechanisms may be important in the pathogenesis of the destructive arthropathies associated with these crystals.

Animals↗
PubMed1987

The increase in skin 7-dehydrocholesterol induced by an hypocholesterolemic agent is associated with elevated 25-hydroxyvitamin D3 plasma level.

Vitamin D3 is generated in skin by UV irradiation of 7-dehydrocholesterol (7-DEHC). Whether the 7-DEHC amount in skin affects vitamin D3 formation, and thereby the plasma level of 25-hydroxyvitamin D3 (25[OH]D3) is not known. In the present work we report on the influence on vitamin D and Ca metabolism of a new hypocholesterolemic agent, HCG-917 (0-2-[hydroxy-3-]N'-(2-chlorophenyl)-N-piperazinyl-1- [propyl]-4-chloro-benz-aldoxim-hydrochloride) which inhibits 7-DEHC reductase and thereby increases skin 7-DEHC. Rats were treated with HCG 917 (0.3 and 5.0 mg/kg, orally) for 13 days. HCG 917 caused a dose-dependent decrease in cholesterol and concomitant accumulation of 7-DEHC in plasma and skin. In skin, 7-DEHC was: control: 1.05 +/- 0.20; HCG 917, 0.3 mg/kg: 1.41 +/- 0.22; HCG 917, 5.0 mg/kg: 2.35 +/- 0.35 mg/g. At a dose of 0.3 mg/kg, HCG 917 had no significant influence on the plasma level of neither 25(OH)D3 nor 1,25(OH)2D3. However, at a dose of 5.0 mg/kg, HCG 917 induced a significant increase in plasma 25(OH)D3 (control: 36.2 +/- 2.2; HCG 917 5.0 mg/kg: 57.6 +/- 6.5 nmol/l) and a slight but not significant rise in 1,25(OH)2D3. Calcium balance studies indicated that HCG 917 did not influence intestinal Ca absorption nor urinary Ca excretion. At a dose of 5.0 mg/kg HCG 917 slightly induced a decrease in total plasma Ca. In conclusion, HCG 917 treatment can induce a significant rise in skin 7-DEHC with an increase in plasma 25(OH)D3. These results suggest that variation in the skin level of 7-DEHC can directly influence the cutaneous production of vitamin D3 and thereby the vitamin D status of the organism.

Animals↗
PubMed1987

Murine osteoblastlike cells and the osteogenic cell MC3T3-E1 release a macrophage colony-stimulating activity in culture.

The osteoclast may be of hematopoietic lineage and as such its development could be regulated by colony-stimulating factors. Since there is much interest as to whether osteoblasts influence bone resorption, we examined whether bone cells produce colony-stimulating activity. Both cells isolated from neonatal calvaria and the osteogenic cell MC3T3-E1 were found to constitutively release a colony-stimulating activity possessing characteristics of a macrophage colony-stimulating factor, as determined by basic biochemical purification and by identity of colonies induced in cultures of bone marrow cells. Release could be increased by the presence of the bone-resorbing agents lipopolysaccharide and 1,25 dihydroxyvitamin D3. We conclude that the osteoblast may contribute to both the processes of osteoclast formation and of hematopoiesis through the secretion of colony-stimulating activity into the adjacent bone marrow.

Animals↗
PubMed1987

Hypercalcemia induced with an arotinoid in thyroparathyroidectomized rats. New model to study bone resorption in vivo.

A model of stimulated bone resorption was developed using a synthetic retinoid in thyroparathyroidectomized rats. The retinoid induced an increase in bone resorption and in the number of vertebral subperiosteal osteoclasts. The resulting increase in plasma Ca could be used as an easily measured index of bone resorption. Three bisphosphonates produced a dose-related prevention and reversal of retinoid-induced hypercalcemia. Their potencies were similar to those previously obtained by histomorphometry. Irradiation (600 rad) of the rats prevented hypercalcemia but failed to reverse it, showing that proliferation of osteoclast precursor cells was important in inducing, but not in maintaining, bone resorption. Calcitonin produced similar effects on calcemia and prevented the increase in osteoclast number but failed to reverse the increase, suggesting that it inhibited precursor proliferation. This model represents a new tool to study mechanisms of bone resorption and the action of inhibitors in vivo.

Animals↗